text: /*
   * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
   * Written by Alex Tomas <alex@clusterfs.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public Licens
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
   */
  
  
  /*
   * mballoc.c contains the multiblocks allocation routines
   */
  
  #include "ext4_jbd2.h"
  #include "mballoc.h"
  #include <linux/log2.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/backing-dev.h>
  #include <trace/events/ext4.h>
  
  #ifdef CONFIG_EXT4_DEBUG
  ushort ext4_mballoc_debug __read_mostly;
  
  module_param_named(mballoc_debug, ext4_mballoc_debug, ushort, 0644);
  MODULE_PARM_DESC(mballoc_debug, "Debugging level for ext4's mballoc");
  #endif
  
  /*
   * MUSTDO:
   *   - test ext4_ext_search_left() and ext4_ext_search_right()
   *   - search for metadata in few groups
   *
   * TODO v4:
   *   - normalization should take into account whether file is still open
   *   - discard preallocations if no free space left (policy?)
   *   - don't normalize tails
   *   - quota
   *   - reservation for superuser
   *
   * TODO v3:
   *   - bitmap read-ahead (proposed by Oleg Drokin aka green)
   *   - track min/max extents in each group for better group selection
   *   - mb_mark_used() may allocate chunk right after splitting buddy
   *   - tree of groups sorted by number of free blocks
   *   - error handling
   */
  
  /*
   * The allocation request involve request for multiple number of blocks
   * near to the goal(block) value specified.
   *
   * During initialization phase of the allocator we decide to use the
   * group preallocation or inode preallocation depending on the size of
   * the file. The size of the file could be the resulting file size we
   * would have after allocation, or the current file size, which ever
   * is larger. If the size is less than sbi->s_mb_stream_request we
   * select to use the group preallocation. The default value of
   * s_mb_stream_request is 16 blocks. This can also be tuned via
   * /sys/fs/ext4/<partition>/mb_stream_req. The value is represented in
   * terms of number of blocks.
   *
   * The main motivation for having small file use group preallocation is to
   * ensure that we have small files closer together on the disk.
   *
   * First stage the allocator looks at the inode prealloc list,
   * ext4_inode_info->i_prealloc_list, which contains list of prealloc
   * spaces for this particular inode. The inode prealloc space is
   * represented as:
   *
   * pa_lstart -> the logical start block for this prealloc space
   * pa_pstart -> the physical start block for this prealloc space
   * pa_len    -> length for this prealloc space (in clusters)
   * pa_free   ->  free space available in this prealloc space (in clusters)
   *
   * The inode preallocation space is used looking at the _logical_ start
   * block. If only the logical file block falls within the range of prealloc
   * space we will consume the particular prealloc space. This makes sure that
   * we have contiguous physical blocks representing the file blocks
   *
   * The important thing to be noted in case of inode prealloc space is that
   * we don't modify the values associated to inode prealloc space except
   * pa_free.
   *
   * If we are not able to find blocks in the inode prealloc space and if we
   * have the group allocation flag set then we look at the locality group
   * prealloc space. These are per CPU prealloc list represented as
   *
   * ext4_sb_info.s_locality_groups[smp_processor_id()]
   *
   * The reason for having a per cpu locality group is to reduce the contention
   * between CPUs. It is possible to get scheduled at this point.
   *
   * The locality group prealloc space is used looking at whether we have
   * enough free space (pa_free) within the prealloc space.
   *
   * If we can't allocate blocks via inode prealloc or/and locality group
   * prealloc then we look at the buddy cache. The buddy cache is represented
   * by ext4_sb_info.s_buddy_cache (struct inode) whose file offset gets
   * mapped to the buddy and bitmap information regarding different
   * groups. The buddy information is attached to buddy cache inode so that
   * we can access them through the page cache. The information regarding
   * each group is loaded via ext4_mb_load_buddy.  The information involve
   * block bitmap and buddy information. The information are stored in the
   * inode as:
   *
   *  {                        page                        }
   *  [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...
   *
   *
   * one block each for bitmap and buddy information.  So for each group we
   * take up 2 blocks. A page can contain blocks_per_page (PAGE_CACHE_SIZE /
   * blocksize) blocks.  So it can have information regarding groups_per_page
   * which is blocks_per_page/2
   *
   * The buddy cache inode is not stored on disk. The inode is thrown
   * away when the filesystem is unmounted.
   *
   * We look for count number of blocks in the buddy cache. If we were able
   * to locate that many free blocks we return with additional information
   * regarding rest of the contiguous physical block available
   *
   * Before allocating blocks via buddy cache we normalize the request
   * blocks. This ensure we ask for more blocks that we needed. The extra
   * blocks that we get after allocation is added to the respective prealloc
   * list. In case of inode preallocation we follow a list of heuristics
   * based on file size. This can be found in ext4_mb_normalize_request. If
   * we are doing a group prealloc we try to normalize the request to
   * sbi->s_mb_group_prealloc.  The default value of s_mb_group_prealloc is
   * dependent on the cluster size; for non-bigalloc file systems, it is
   * 512 blocks. This can be tuned via
   * /sys/fs/ext4/<partition>/mb_group_prealloc. The value is represented in
   * terms of number of blocks. If we have mounted the file system with -O
   * stripe=<value> option the group prealloc request is normalized to the
   * the smallest multiple of the stripe value (sbi->s_stripe) which is
   * greater than the default mb_group_prealloc.
   *
   * The regular allocator (using the buddy cache) supports a few tunables.
   *
   * /sys/fs/ext4/<partition>/mb_min_to_scan
   * /sys/fs/ext4/<partition>/mb_max_to_scan
   * /sys/fs/ext4/<partition>/mb_order2_req
   *
   * The regular allocator uses buddy scan only if the request len is power of
   * 2 blocks and the order of allocation is >= sbi->s_mb_order2_reqs. The
   * value of s_mb_order2_reqs can be tuned via
   * /sys/fs/ext4/<partition>/mb_order2_req.  If the request len is equal to
   * stripe size (sbi->s_stripe), we try to search for contiguous block in
   * stripe size. This should result in better allocation on RAID setups. If
   * not, we search in the specific group using bitmap for best extents. The
   * tunable min_to_scan and max_to_scan control the behaviour here.
   * min_to_scan indicate how long the mballoc __must__ look for a best
   * extent and max_to_scan indicates how long the mballoc __can__ look for a
   * best extent in the found extents. Searching for the blocks starts with
   * the group specified as the goal value in allocation context via
   * ac_g_ex. Each group is first checked based on the criteria whether it
   * can be used for allocation. ext4_mb_good_group explains how the groups are
   * checked.
   *
   * Both the prealloc space are getting populated as above. So for the first
   * request we will hit the buddy cache which will result in this prealloc
   * space getting filled. The prealloc space is then later used for the
   * subsequent request.
   */
  
  /*
   * mballoc operates on the following data:
   *  - on-disk bitmap
   *  - in-core buddy (actually includes buddy and bitmap)
   *  - preallocation descriptors (PAs)
   *
   * there are two types of preallocations:
   *  - inode
   *    assiged to specific inode and can be used for this inode only.
   *    it describes part of inode's space preallocated to specific
   *    physical blocks. any block from that preallocated can be used
   *    independent. the descriptor just tracks number of blocks left
   *    unused. so, before taking some block from descriptor, one must
   *    make sure corresponded logical block isn't allocated yet. this
   *    also means that freeing any block within descriptor's range
   *    must discard all preallocated blocks.
   *  - locality group
   *    assigned to specific locality group which does not translate to
   *    permanent set of inodes: inode can join and leave group. space
   *    from this type of preallocation can be used for any inode. thus
   *    it's consumed from the beginning to the end.
   *
   * relation between them can be expressed as:
   *    in-core buddy = on-disk bitmap + preallocation descriptors
   *
   * this mean blocks mballoc considers used are:
   *  - allocated blocks (persistent)
   *  - preallocated blocks (non-persistent)
   *
   * consistency in mballoc world means that at any time a block is either
   * free or used in ALL structures. notice: "any time" should not be read
   * literally -- time is discrete and delimited by locks.
   *
   *  to keep it simple, we don't use block numbers, instead we count number of
   *  blocks: how many blocks marked used/free in on-disk bitmap, buddy and PA.
   *
   * all operations can be expressed as:
   *  - init buddy:			buddy = on-disk + PAs
   *  - new PA:				buddy += N; PA = N
   *  - use inode PA:			on-disk += N; PA -= N
   *  - discard inode PA			buddy -= on-disk - PA; PA = 0
   *  - use locality group PA		on-disk += N; PA -= N
   *  - discard locality group PA		buddy -= PA; PA = 0
   *  note: 'buddy -= on-disk - PA' is used to show that on-disk bitmap
   *        is used in real operation because we can't know actual used
   *        bits from PA, only from on-disk bitmap
   *
   * if we follow this strict logic, then all operations above should be atomic.
   * given some of them can block, we'd have to use something like semaphores
   * killing performance on high-end SMP hardware. let's try to relax it using
   * the following knowledge:
   *  1) if buddy is referenced, it's already initialized
   *  2) while block is used in buddy and the buddy is referenced,
   *     nobody can re-allocate that block
   *  3) we work on bitmaps and '+' actually means 'set bits'. if on-disk has
   *     bit set and PA claims same block, it's OK. IOW, one can set bit in
   *     on-disk bitmap if buddy has same bit set or/and PA covers corresponded
   *     block
   *
   * so, now we're building a concurrency table:
   *  - init buddy vs.
   *    - new PA
   *      blocks for PA are allocated in the buddy, buddy must be referenced
   *      until PA is linked to allocation group to avoid concurrent buddy init
   *    - use inode PA
   *      we need to make sure that either on-disk bitmap or PA has uptodate data
   *      given (3) we care that PA-=N operation doesn't interfere with init
   *    - discard inode PA
   *      the simplest way would be to have buddy initialized by the discard
   *    - use locality group PA
   *      again PA-=N must be serialized with init
   *    - discard locality group PA
   *      the simplest way would be to have buddy initialized by the discard
   *  - new PA vs.
   *    - use inode PA
   *      i_data_sem serializes them
   *    - discard inode PA
   *      discard process must wait until PA isn't used by another process
   *    - use locality group PA
   *      some mutex should serialize them
   *    - discard locality group PA
   *      discard process must wait until PA isn't used by another process
   *  - use inode PA
   *    - use inode PA
   *      i_data_sem or another mutex should serializes them
   *    - discard inode PA
   *      discard process must wait until PA isn't used by another process
   *    - use locality group PA
   *      nothing wrong here -- they're different PAs covering different blocks
   *    - discard locality group PA
   *      discard process must wait until PA isn't used by another process
   *
   * now we're ready to make few consequences:
   *  - PA is referenced and while it is no discard is possible
   *  - PA is referenced until block isn't marked in on-disk bitmap
   *  - PA changes only after on-disk bitmap
   *  - discard must not compete with init. either init is done before
   *    any discard or they're serialized somehow
   *  - buddy init as sum of on-disk bitmap and PAs is done atomically
   *
   * a special case when we've used PA to emptiness. no need to modify buddy
   * in this case, but we should care about concurrent init
   *
   */
  
   /*
   * Logic in few words:
   *
   *  - allocation:
   *    load group
   *    find blocks
   *    mark bits in on-disk bitmap
   *    release group
   *
   *  - use preallocation:
   *    find proper PA (per-inode or group)
   *    load group
   *    mark bits in on-disk bitmap
   *    release group
   *    release PA
   *
   *  - free:
   *    load group
   *    mark bits in on-disk bitmap
   *    release group
   *
   *  - discard preallocations in group:
   *    mark PAs deleted
   *    move them onto local list
   *    load on-disk bitmap
   *    load group
   *    remove PA from object (inode or locality group)
   *    mark free blocks in-core
   *
   *  - discard inode's preallocations:
   */
  
  /*
   * Locking rules
   *
   * Locks:
   *  - bitlock on a group	(group)
   *  - object (inode/locality)	(object)
   *  - per-pa lock		(pa)
   *
   * Paths:
   *  - new pa
   *    object
   *    group
   *
   *  - find and use pa:
   *    pa
   *
   *  - release consumed pa:
   *    pa
   *    group
   *    object
   *
   *  - generate in-core bitmap:
   *    group
   *        pa
   *
   *  - discard all for given object (inode, locality group):
   *    object
   *        pa
   *    group
   *
   *  - discard all for given group:
   *    group
   *        pa
   *    group
   *        object
   *
   */
  static struct kmem_cache *ext4_pspace_cachep;
  static struct kmem_cache *ext4_ac_cachep;
  static struct kmem_cache *ext4_free_data_cachep;
  
  /* We create slab caches for groupinfo data structures based on the
   * superblock block size.  There will be one per mounted filesystem for
   * each unique s_blocksize_bits */
  #define NR_GRPINFO_CACHES 8
  static struct kmem_cache *ext4_groupinfo_caches[NR_GRPINFO_CACHES];
  
  static const char *ext4_groupinfo_slab_names[NR_GRPINFO_CACHES] = {
  	"ext4_groupinfo_1k", "ext4_groupinfo_2k", "ext4_groupinfo_4k",
  	"ext4_groupinfo_8k", "ext4_groupinfo_16k", "ext4_groupinfo_32k",
  	"ext4_groupinfo_64k", "ext4_groupinfo_128k"
  };
  
  static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
  					ext4_group_t group);
  static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
  						ext4_group_t group);
  static void ext4_free_data_callback(struct super_block *sb,
  				struct ext4_journal_cb_entry *jce, int rc);
  
  static inline void *mb_correct_addr_and_bit(int *bit, void *addr)
  {
  #if BITS_PER_LONG == 64
  	*bit += ((unsigned long) addr & 7UL) << 3;
  	addr = (void *) ((unsigned long) addr & ~7UL);
  #elif BITS_PER_LONG == 32
  	*bit += ((unsigned long) addr & 3UL) << 3;
  	addr = (void *) ((unsigned long) addr & ~3UL);
  #else
  #error "how many bits you are?!"
  #endif
  	return addr;
  }
  
  static inline int mb_test_bit(int bit, void *addr)
  {
  	/*
  	 * ext4_test_bit on architecture like powerpc
  	 * needs unsigned long aligned address
  	 */
  	addr = mb_correct_addr_and_bit(&bit, addr);
  	return ext4_test_bit(bit, addr);
  }
  
  static inline void mb_set_bit(int bit, void *addr)
  {
  	addr = mb_correct_addr_and_bit(&bit, addr);
  	ext4_set_bit(bit, addr);
  }
  
  static inline void mb_clear_bit(int bit, void *addr)
  {
  	addr = mb_correct_addr_and_bit(&bit, addr);
  	ext4_clear_bit(bit, addr);
  }
  
  static inline int mb_test_and_clear_bit(int bit, void *addr)
  {
  	addr = mb_correct_addr_and_bit(&bit, addr);
  	return ext4_test_and_clear_bit(bit, addr);
  }
  
  static inline int mb_find_next_zero_bit(void *addr, int max, int start)
  {
  	int fix = 0, ret, tmpmax;
  	addr = mb_correct_addr_and_bit(&fix, addr);
  	tmpmax = max + fix;
  	start += fix;
  
  	ret = ext4_find_next_zero_bit(addr, tmpmax, start) - fix;
  	if (ret > max)
  		return max;
  	return ret;
  }
  
  static inline int mb_find_next_bit(void *addr, int max, int start)
  {
  	int fix = 0, ret, tmpmax;
  	addr = mb_correct_addr_and_bit(&fix, addr);
  	tmpmax = max + fix;
  	start += fix;
  
  	ret = ext4_find_next_bit(addr, tmpmax, start) - fix;
  	if (ret > max)
  		return max;
  	return ret;
  }
  
  static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
  {
  	char *bb;
  
  	BUG_ON(e4b->bd_bitmap == e4b->bd_buddy);
  	BUG_ON(max == NULL);
  
  	if (order > e4b->bd_blkbits + 1) {
  		*max = 0;
  		return NULL;
  	}
  
  	/* at order 0 we see each particular block */
  	if (order == 0) {
  		*max = 1 << (e4b->bd_blkbits + 3);
  		return e4b->bd_bitmap;
  	}
  
  	bb = e4b->bd_buddy + EXT4_SB(e4b->bd_sb)->s_mb_offsets[order];
  	*max = EXT4_SB(e4b->bd_sb)->s_mb_maxs[order];
  
  	return bb;
  }
  
  #ifdef DOUBLE_CHECK
  static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b,
  			   int first, int count)
  {
  	int i;
  	struct super_block *sb = e4b->bd_sb;
  
  	if (unlikely(e4b->bd_info->bb_bitmap == NULL))
  		return;
  	assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));
  	for (i = 0; i < count; i++) {
  		if (!mb_test_bit(first + i, e4b->bd_info->bb_bitmap)) {
  			ext4_fsblk_t blocknr;
  
  			blocknr = ext4_group_first_block_no(sb, e4b->bd_group);
  			blocknr += EXT4_C2B(EXT4_SB(sb), first + i);
  			ext4_grp_locked_error(sb, e4b->bd_group,
  					      inode ? inode->i_ino : 0,
  					      blocknr,
  					      "freeing block already freed "
  					      "(bit %u)",
  					      first + i);
  		}
  		mb_clear_bit(first + i, e4b->bd_info->bb_bitmap);
  	}
  }
  
  static void mb_mark_used_double(struct ext4_buddy *e4b, int first, int count)
  {
  	int i;
  
  	if (unlikely(e4b->bd_info->bb_bitmap == NULL))
  		return;
  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
  	for (i = 0; i < count; i++) {
  		BUG_ON(mb_test_bit(first + i, e4b->bd_info->bb_bitmap));
  		mb_set_bit(first + i, e4b->bd_info->bb_bitmap);
  	}
  }
  
  static void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
  {
  	if (memcmp(e4b->bd_info->bb_bitmap, bitmap, e4b->bd_sb->s_blocksize)) {
  		unsigned char *b1, *b2;
  		int i;
  		b1 = (unsigned char *) e4b->bd_info->bb_bitmap;
  		b2 = (unsigned char *) bitmap;
  		for (i = 0; i < e4b->bd_sb->s_blocksize; i++) {
  			if (b1[i] != b2[i]) {
  				ext4_msg(e4b->bd_sb, KERN_ERR,
  					 "corruption in group %u "
  					 "at byte %u(%u): %x in copy != %x "
  					 "on disk/prealloc",
  					 e4b->bd_group, i, i * 8, b1[i], b2[i]);
  				BUG();
  			}
  		}
  	}
  }
  
  #else
  static inline void mb_free_blocks_double(struct inode *inode,
  				struct ext4_buddy *e4b, int first, int count)
  {
  	return;
  }
  static inline void mb_mark_used_double(struct ext4_buddy *e4b,
  						int first, int count)
  {
  	return;
  }
  static inline void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
  {
  	return;
  }
  #endif
  
  #ifdef AGGRESSIVE_CHECK
  
  #define MB_CHECK_ASSERT(assert)						\
  do {									\
  	if (!(assert)) {						\
  		printk(KERN_EMERG					\
  			"Assertion failure in %s() at %s:%d: \"%s\"\n",	\
  			function, file, line, # assert);		\
  		BUG();							\
  	}								\
  } while (0)
  
  static int __mb_check_buddy(struct ext4_buddy *e4b, char *file,
  				const char *function, int line)
  {
  	struct super_block *sb = e4b->bd_sb;
  	int order = e4b->bd_blkbits + 1;
  	int max;
  	int max2;
  	int i;
  	int j;
  	int k;
  	int count;
  	struct ext4_group_info *grp;
  	int fragments = 0;
  	int fstart;
  	struct list_head *cur;
  	void *buddy;
  	void *buddy2;
  
  	{
  		static int mb_check_counter;
  		if (mb_check_counter++ % 100 != 0)
  			return 0;
  	}
  
  	while (order > 1) {
  		buddy = mb_find_buddy(e4b, order, &max);
  		MB_CHECK_ASSERT(buddy);
  		buddy2 = mb_find_buddy(e4b, order - 1, &max2);
  		MB_CHECK_ASSERT(buddy2);
  		MB_CHECK_ASSERT(buddy != buddy2);
  		MB_CHECK_ASSERT(max * 2 == max2);
  
  		count = 0;
  		for (i = 0; i < max; i++) {
  
  			if (mb_test_bit(i, buddy)) {
  				/* only single bit in buddy2 may be 1 */
  				if (!mb_test_bit(i << 1, buddy2)) {
  					MB_CHECK_ASSERT(
  						mb_test_bit((i<<1)+1, buddy2));
  				} else if (!mb_test_bit((i << 1) + 1, buddy2)) {
  					MB_CHECK_ASSERT(
  						mb_test_bit(i << 1, buddy2));
  				}
  				continue;
  			}
  
  			/* both bits in buddy2 must be 1 */
  			MB_CHECK_ASSERT(mb_test_bit(i << 1, buddy2));
  			MB_CHECK_ASSERT(mb_test_bit((i << 1) + 1, buddy2));
  
  			for (j = 0; j < (1 << order); j++) {
  				k = (i * (1 << order)) + j;
  				MB_CHECK_ASSERT(
  					!mb_test_bit(k, e4b->bd_bitmap));
  			}
  			count++;
  		}
  		MB_CHECK_ASSERT(e4b->bd_info->bb_counters[order] == count);
  		order--;
  	}
  
  	fstart = -1;
  	buddy = mb_find_buddy(e4b, 0, &max);
  	for (i = 0; i < max; i++) {
  		if (!mb_test_bit(i, buddy)) {
  			MB_CHECK_ASSERT(i >= e4b->bd_info->bb_first_free);
  			if (fstart == -1) {
  				fragments++;
  				fstart = i;
  			}
  			continue;
  		}
  		fstart = -1;
  		/* check used bits only */
  		for (j = 0; j < e4b->bd_blkbits + 1; j++) {
  			buddy2 = mb_find_buddy(e4b, j, &max2);
  			k = i >> j;
  			MB_CHECK_ASSERT(k < max2);
  			MB_CHECK_ASSERT(mb_test_bit(k, buddy2));
  		}
  	}
  	MB_CHECK_ASSERT(!EXT4_MB_GRP_NEED_INIT(e4b->bd_info));
  	MB_CHECK_ASSERT(e4b->bd_info->bb_fragments == fragments);
  
  	grp = ext4_get_group_info(sb, e4b->bd_group);
  	list_for_each(cur, &grp->bb_prealloc_list) {
  		ext4_group_t groupnr;
  		struct ext4_prealloc_space *pa;
  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		ext4_get_group_no_and_offset(sb, pa->pa_pstart, &groupnr, &k);
  		MB_CHECK_ASSERT(groupnr == e4b->bd_group);
  		for (i = 0; i < pa->pa_len; i++)
  			MB_CHECK_ASSERT(mb_test_bit(k + i, buddy));
  	}
  	return 0;
  }
  #undef MB_CHECK_ASSERT
  #define mb_check_buddy(e4b) __mb_check_buddy(e4b,	\
  					__FILE__, __func__, __LINE__)
  #else
  #define mb_check_buddy(e4b)
  #endif
  
  /*
   * Divide blocks started from @first with length @len into
   * smaller chunks with power of 2 blocks.
   * Clear the bits in bitmap which the blocks of the chunk(s) covered,
   * then increase bb_counters[] for corresponded chunk size.
   */
  static void ext4_mb_mark_free_simple(struct super_block *sb,
  				void *buddy, ext4_grpblk_t first, ext4_grpblk_t len,
  					struct ext4_group_info *grp)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	ext4_grpblk_t min;
  	ext4_grpblk_t max;
  	ext4_grpblk_t chunk;
  	unsigned int border;
  
  	BUG_ON(len > EXT4_CLUSTERS_PER_GROUP(sb));
  
  	border = 2 << sb->s_blocksize_bits;
  
  	while (len > 0) {
  		/* find how many blocks can be covered since this position */
  		max = ffs(first | border) - 1;
  
  		/* find how many blocks of power 2 we need to mark */
  		min = fls(len) - 1;
  
  		if (max < min)
  			min = max;
  		chunk = 1 << min;
  
  		/* mark multiblock chunks only */
  		grp->bb_counters[min]++;
  		if (min > 0)
  			mb_clear_bit(first >> min,
  				     buddy + sbi->s_mb_offsets[min]);
  
  		len -= chunk;
  		first += chunk;
  	}
  }
  
  /*
   * Cache the order of the largest free extent we have available in this block
   * group.
   */
  static void
  mb_set_largest_free_order(struct super_block *sb, struct ext4_group_info *grp)
  {
  	int i;
  	int bits;
  
  	grp->bb_largest_free_order = -1; /* uninit */
  
  	bits = sb->s_blocksize_bits + 1;
  	for (i = bits; i >= 0; i--) {
  		if (grp->bb_counters[i] > 0) {
  			grp->bb_largest_free_order = i;
  			break;
  		}
  	}
  }
  
  static noinline_for_stack
  void ext4_mb_generate_buddy(struct super_block *sb,
  				void *buddy, void *bitmap, ext4_group_t group)
  {
  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	ext4_grpblk_t max = EXT4_CLUSTERS_PER_GROUP(sb);
  	ext4_grpblk_t i = 0;
  	ext4_grpblk_t first;
  	ext4_grpblk_t len;
  	unsigned free = 0;
  	unsigned fragments = 0;
  	unsigned long long period = get_cycles();
  
  	/* initialize buddy from bitmap which is aggregation
  	 * of on-disk bitmap and preallocations */
  	i = mb_find_next_zero_bit(bitmap, max, 0);
  	grp->bb_first_free = i;
  	while (i < max) {
  		fragments++;
  		first = i;
  		i = mb_find_next_bit(bitmap, max, i);
  		len = i - first;
  		free += len;
  		if (len > 1)
  			ext4_mb_mark_free_simple(sb, buddy, first, len, grp);
  		else
  			grp->bb_counters[0]++;
  		if (i < max)
  			i = mb_find_next_zero_bit(bitmap, max, i);
  	}
  	grp->bb_fragments = fragments;
  
  	if (free != grp->bb_free) {
  		ext4_grp_locked_error(sb, group, 0, 0,
  				      "block bitmap and bg descriptor "
  				      "inconsistent: %u vs %u free clusters",
  				      free, grp->bb_free);
  		/*
  		 * If we intend to continue, we consider group descriptor
  		 * corrupt and update bb_free using bitmap value
  		 */
  		grp->bb_free = free;
  		if (!EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
  			percpu_counter_sub(&sbi->s_freeclusters_counter,
  					   grp->bb_free);
  		set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT, &grp->bb_state);
  	}
  	mb_set_largest_free_order(sb, grp);
  
  	clear_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
  
  	period = get_cycles() - period;
  	spin_lock(&EXT4_SB(sb)->s_bal_lock);
  	EXT4_SB(sb)->s_mb_buddies_generated++;
  	EXT4_SB(sb)->s_mb_generation_time += period;
  	spin_unlock(&EXT4_SB(sb)->s_bal_lock);
  }
  
  static void mb_regenerate_buddy(struct ext4_buddy *e4b)
  {
  	int count;
  	int order = 1;
  	void *buddy;
  
  	while ((buddy = mb_find_buddy(e4b, order++, &count))) {
  		ext4_set_bits(buddy, 0, count);
  	}
  	e4b->bd_info->bb_fragments = 0;
  	memset(e4b->bd_info->bb_counters, 0,
  		sizeof(*e4b->bd_info->bb_counters) *
  		(e4b->bd_sb->s_blocksize_bits + 2));
  
  	ext4_mb_generate_buddy(e4b->bd_sb, e4b->bd_buddy,
  		e4b->bd_bitmap, e4b->bd_group);
  }
  
  /* The buddy information is attached the buddy cache inode
   * for convenience. The information regarding each group
   * is loaded via ext4_mb_load_buddy. The information involve
   * block bitmap and buddy information. The information are
   * stored in the inode as
   *
   * {                        page                        }
   * [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...
   *
   *
   * one block each for bitmap and buddy information.
   * So for each group we take up 2 blocks. A page can
   * contain blocks_per_page (PAGE_CACHE_SIZE / blocksize)  blocks.
   * So it can have information regarding groups_per_page which
   * is blocks_per_page/2
   *
   * Locking note:  This routine takes the block group lock of all groups
   * for this page; do not hold this lock when calling this routine!
   */
  
  static int ext4_mb_init_cache(struct page *page, char *incore, gfp_t gfp)
  {
  	ext4_group_t ngroups;
  	int blocksize;
  	int blocks_per_page;
  	int groups_per_page;
  	int err = 0;
  	int i;
  	ext4_group_t first_group, group;
  	int first_block;
  	struct super_block *sb;
  	struct buffer_head *bhs;
  	struct buffer_head **bh = NULL;
  	struct inode *inode;
  	char *data;
  	char *bitmap;
  	struct ext4_group_info *grinfo;
  
  	mb_debug(1, "init page %lu\n", page->index);
  
  	inode = page->mapping->host;
  	sb = inode->i_sb;
  	ngroups = ext4_get_groups_count(sb);
  	blocksize = 1 << inode->i_blkbits;
  	blocks_per_page = PAGE_CACHE_SIZE / blocksize;
  
  	groups_per_page = blocks_per_page >> 1;
  	if (groups_per_page == 0)
  		groups_per_page = 1;
  
  	/* allocate buffer_heads to read bitmaps */
  	if (groups_per_page > 1) {
  		i = sizeof(struct buffer_head *) * groups_per_page;
  		bh = kzalloc(i, gfp);
  		if (bh == NULL) {
  			err = -ENOMEM;
  			goto out;
  		}
  	} else
  		bh = &bhs;
  
  	first_group = page->index * blocks_per_page / 2;
  
  	/* read all groups the page covers into the cache */
  	for (i = 0, group = first_group; i < groups_per_page; i++, group++) {
  		if (group >= ngroups)
  			break;
  
  		grinfo = ext4_get_group_info(sb, group);
  		/*
  		 * If page is uptodate then we came here after online resize
  		 * which added some new uninitialized group info structs, so
  		 * we must skip all initialized uptodate buddies on the page,
  		 * which may be currently in use by an allocating task.
  		 */
  		if (PageUptodate(page) && !EXT4_MB_GRP_NEED_INIT(grinfo)) {
  			bh[i] = NULL;
  			continue;
  		}
  		bh[i] = ext4_read_block_bitmap_nowait(sb, group);
  		if (IS_ERR(bh[i])) {
  			err = PTR_ERR(bh[i]);
  			bh[i] = NULL;
  			goto out;
  		}
  		mb_debug(1, "read bitmap for group %u\n", group);
  	}
  
  	/* wait for I/O completion */
  	for (i = 0, group = first_group; i < groups_per_page; i++, group++) {
  		int err2;
  
  		if (!bh[i])
  			continue;
  		err2 = ext4_wait_block_bitmap(sb, group, bh[i]);
  		if (!err)
  			err = err2;
  	}
  
  	first_block = page->index * blocks_per_page;
  	for (i = 0; i < blocks_per_page; i++) {
  		group = (first_block + i) >> 1;
  		if (group >= ngroups)
  			break;
  
  		if (!bh[group - first_group])
  			/* skip initialized uptodate buddy */
  			continue;
  
  		if (!buffer_verified(bh[group - first_group]))
  			/* Skip faulty bitmaps */
  			continue;
  		err = 0;
  
  		/*
  		 * data carry information regarding this
  		 * particular group in the format specified
  		 * above
  		 *
  		 */
  		data = page_address(page) + (i * blocksize);
  		bitmap = bh[group - first_group]->b_data;
  
  		/*
  		 * We place the buddy block and bitmap block
  		 * close together
  		 */
  		if ((first_block + i) & 1) {
  			/* this is block of buddy */
  			BUG_ON(incore == NULL);
  			mb_debug(1, "put buddy for group %u in page %lu/%x\n",
  				group, page->index, i * blocksize);
  			trace_ext4_mb_buddy_bitmap_load(sb, group);
  			grinfo = ext4_get_group_info(sb, group);
  			grinfo->bb_fragments = 0;
  			memset(grinfo->bb_counters, 0,
  			       sizeof(*grinfo->bb_counters) *
  				(sb->s_blocksize_bits+2));
  			/*
  			 * incore got set to the group block bitmap below
  			 */
  			ext4_lock_group(sb, group);
  			/* init the buddy */
  			memset(data, 0xff, blocksize);
  			ext4_mb_generate_buddy(sb, data, incore, group);
  			ext4_unlock_group(sb, group);
  			incore = NULL;
  		} else {
  			/* this is block of bitmap */
  			BUG_ON(incore != NULL);
  			mb_debug(1, "put bitmap for group %u in page %lu/%x\n",
  				group, page->index, i * blocksize);
  			trace_ext4_mb_bitmap_load(sb, group);
  
  			/* see comments in ext4_mb_put_pa() */
  			ext4_lock_group(sb, group);
  			memcpy(data, bitmap, blocksize);
  
  			/* mark all preallocated blks used in in-core bitmap */
  			ext4_mb_generate_from_pa(sb, data, group);
  			ext4_mb_generate_from_freelist(sb, data, group);
  			ext4_unlock_group(sb, group);
  
  			/* set incore so that the buddy information can be
  			 * generated using this
  			 */
  			incore = data;
  		}
  	}
  	SetPageUptodate(page);
  
  out:
  	if (bh) {
  		for (i = 0; i < groups_per_page; i++)
  			brelse(bh[i]);
  		if (bh != &bhs)
  			kfree(bh);
  	}
  	return err;
  }
  
  /*
   * Lock the buddy and bitmap pages. This make sure other parallel init_group
   * on the same buddy page doesn't happen whild holding the buddy page lock.
   * Return locked buddy and bitmap pages on e4b struct. If buddy and bitmap
   * are on the same page e4b->bd_buddy_page is NULL and return value is 0.
   */
  static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
  		ext4_group_t group, struct ext4_buddy *e4b, gfp_t gfp)
  {
  	struct inode *inode = EXT4_SB(sb)->s_buddy_cache;
  	int block, pnum, poff;
  	int blocks_per_page;
  	struct page *page;
  
  	e4b->bd_buddy_page = NULL;
  	e4b->bd_bitmap_page = NULL;
  
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  	page = find_or_create_page(inode->i_mapping, pnum, gfp);
  	if (!page)
  		return -ENOMEM;
  	BUG_ON(page->mapping != inode->i_mapping);
  	e4b->bd_bitmap_page = page;
  	e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
  
  	if (blocks_per_page >= 2) {
  		/* buddy and bitmap are on the same page */
  		return 0;
  	}
  
  	block++;
  	pnum = block / blocks_per_page;
  	page = find_or_create_page(inode->i_mapping, pnum, gfp);
  	if (!page)
  		return -ENOMEM;
  	BUG_ON(page->mapping != inode->i_mapping);
  	e4b->bd_buddy_page = page;
  	return 0;
  }
  
  static void ext4_mb_put_buddy_page_lock(struct ext4_buddy *e4b)
  {
  	if (e4b->bd_bitmap_page) {
  		unlock_page(e4b->bd_bitmap_page);
  		page_cache_release(e4b->bd_bitmap_page);
  	}
  	if (e4b->bd_buddy_page) {
  		unlock_page(e4b->bd_buddy_page);
  		page_cache_release(e4b->bd_buddy_page);
  	}
  }
  
  /*
   * Locking note:  This routine calls ext4_mb_init_cache(), which takes the
   * block group lock of all groups for this page; do not hold the BG lock when
   * calling this routine!
   */
  static noinline_for_stack
  int ext4_mb_init_group(struct super_block *sb, ext4_group_t group, gfp_t gfp)
  {
  
  	struct ext4_group_info *this_grp;
  	struct ext4_buddy e4b;
  	struct page *page;
  	int ret = 0;
  
  	might_sleep();
  	mb_debug(1, "init group %u\n", group);
  	this_grp = ext4_get_group_info(sb, group);
  	/*
  	 * This ensures that we don't reinit the buddy cache
  	 * page which map to the group from which we are already
  	 * allocating. If we are looking at the buddy cache we would
  	 * have taken a reference using ext4_mb_load_buddy and that
  	 * would have pinned buddy page to page cache.
  	 * The call to ext4_mb_get_buddy_page_lock will mark the
  	 * page accessed.
  	 */
  	ret = ext4_mb_get_buddy_page_lock(sb, group, &e4b, gfp);
  	if (ret || !EXT4_MB_GRP_NEED_INIT(this_grp)) {
  		/*
  		 * somebody initialized the group
  		 * return without doing anything
  		 */
  		goto err;
  	}
  
  	page = e4b.bd_bitmap_page;
  	ret = ext4_mb_init_cache(page, NULL, gfp);
  	if (ret)
  		goto err;
  	if (!PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  
  	if (e4b.bd_buddy_page == NULL) {
  		/*
  		 * If both the bitmap and buddy are in
  		 * the same page we don't need to force
  		 * init the buddy
  		 */
  		ret = 0;
  		goto err;
  	}
  	/* init buddy cache */
  	page = e4b.bd_buddy_page;
  	ret = ext4_mb_init_cache(page, e4b.bd_bitmap, gfp);
  	if (ret)
  		goto err;
  	if (!PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  err:
  	ext4_mb_put_buddy_page_lock(&e4b);
  	return ret;
  }
  
  /*
   * Locking note:  This routine calls ext4_mb_init_cache(), which takes the
   * block group lock of all groups for this page; do not hold the BG lock when
   * calling this routine!
   */
  static noinline_for_stack int
  ext4_mb_load_buddy_gfp(struct super_block *sb, ext4_group_t group,
  		       struct ext4_buddy *e4b, gfp_t gfp)
  {
  	int blocks_per_page;
  	int block;
  	int pnum;
  	int poff;
  	struct page *page;
  	int ret;
  	struct ext4_group_info *grp;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct inode *inode = sbi->s_buddy_cache;
  
  	might_sleep();
  	mb_debug(1, "load group %u\n", group);
  
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
  	grp = ext4_get_group_info(sb, group);
  
  	e4b->bd_blkbits = sb->s_blocksize_bits;
  	e4b->bd_info = grp;
  	e4b->bd_sb = sb;
  	e4b->bd_group = group;
  	e4b->bd_buddy_page = NULL;
  	e4b->bd_bitmap_page = NULL;
  
  	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  		/*
  		 * we need full data about the group
  		 * to make a good selection
  		 */
  		ret = ext4_mb_init_group(sb, group, gfp);
  		if (ret)
  			return ret;
  	}
  
  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  
  	/* we could use find_or_create_page(), but it locks page
  	 * what we'd like to avoid in fast path ... */
  	page = find_get_page_flags(inode->i_mapping, pnum, FGP_ACCESSED);
  	if (page == NULL || !PageUptodate(page)) {
  		if (page)
  			/*
  			 * drop the page reference and try
  			 * to get the page with lock. If we
  			 * are not uptodate that implies
  			 * somebody just created the page but
  			 * is yet to initialize the same. So
  			 * wait for it to initialize.
  			 */
  			page_cache_release(page);
  		page = find_or_create_page(inode->i_mapping, pnum, gfp);
  		if (page) {
  			BUG_ON(page->mapping != inode->i_mapping);
  			if (!PageUptodate(page)) {
  				ret = ext4_mb_init_cache(page, NULL, gfp);
  				if (ret) {
  					unlock_page(page);
  					goto err;
  				}
  				mb_cmp_bitmaps(e4b, page_address(page) +
  					       (poff * sb->s_blocksize));
  			}
  			unlock_page(page);
  		}
  	}
  	if (page == NULL) {
  		ret = -ENOMEM;
  		goto err;
  	}
  	if (!PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  
  	/* Pages marked accessed already */
  	e4b->bd_bitmap_page = page;
  	e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
  
  	block++;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  
  	page = find_get_page_flags(inode->i_mapping, pnum, FGP_ACCESSED);
  	if (page == NULL || !PageUptodate(page)) {
  		if (page)
  			page_cache_release(page);
  		page = find_or_create_page(inode->i_mapping, pnum, gfp);
  		if (page) {
  			BUG_ON(page->mapping != inode->i_mapping);
  			if (!PageUptodate(page)) {
  				ret = ext4_mb_init_cache(page, e4b->bd_bitmap,
  							 gfp);
  				if (ret) {
  					unlock_page(page);
  					goto err;
  				}
  			}
  			unlock_page(page);
  		}
  	}
  	if (page == NULL) {
  		ret = -ENOMEM;
  		goto err;
  	}
  	if (!PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  
  	/* Pages marked accessed already */
  	e4b->bd_buddy_page = page;
  	e4b->bd_buddy = page_address(page) + (poff * sb->s_blocksize);
  
  	BUG_ON(e4b->bd_bitmap_page == NULL);
  	BUG_ON(e4b->bd_buddy_page == NULL);
  
  	return 0;
  
  err:
  	if (page)
  		page_cache_release(page);
  	if (e4b->bd_bitmap_page)
  		page_cache_release(e4b->bd_bitmap_page);
  	if (e4b->bd_buddy_page)
  		page_cache_release(e4b->bd_buddy_page);
  	e4b->bd_buddy = NULL;
  	e4b->bd_bitmap = NULL;
  	return ret;
  }
  
  static int ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
  			      struct ext4_buddy *e4b)
  {
  	return ext4_mb_load_buddy_gfp(sb, group, e4b, GFP_NOFS);
  }
  
  static void ext4_mb_unload_buddy(struct ext4_buddy *e4b)
  {
  	if (e4b->bd_bitmap_page)
  		page_cache_release(e4b->bd_bitmap_page);
  	if (e4b->bd_buddy_page)
  		page_cache_release(e4b->bd_buddy_page);
  }
  
  
  static int mb_find_order_for_block(struct ext4_buddy *e4b, int block)
  {
  	int order = 1;
  	int bb_incr = 1 << (e4b->bd_blkbits - 1);
  	void *bb;
  
  	BUG_ON(e4b->bd_bitmap == e4b->bd_buddy);
  	BUG_ON(block >= (1 << (e4b->bd_blkbits + 3)));
  
  	bb = e4b->bd_buddy;
  	while (order <= e4b->bd_blkbits + 1) {
  		block = block >> 1;
  		if (!mb_test_bit(block, bb)) {
  			/* this block is part of buddy of order 'order' */
  			return order;
  		}
  		bb += bb_incr;
  		bb_incr >>= 1;
  		order++;
  	}
  	return 0;
  }
  
  static void mb_clear_bits(void *bm, int cur, int len)
  {
  	__u32 *addr;
  
  	len = cur + len;
  	while (cur < len) {
  		if ((cur & 31) == 0 && (len - cur) >= 32) {
  			/* fast path: clear whole word at once */
  			addr = bm + (cur >> 3);
  			*addr = 0;
  			cur += 32;
  			continue;
  		}
  		mb_clear_bit(cur, bm);
  		cur++;
  	}
  }
  
  /* clear bits in given range
   * will return first found zero bit if any, -1 otherwise
   */
  static int mb_test_and_clear_bits(void *bm, int cur, int len)
  {
  	__u32 *addr;
  	int zero_bit = -1;
  
  	len = cur + len;
  	while (cur < len) {
  		if ((cur & 31) == 0 && (len - cur) >= 32) {
  			/* fast path: clear whole word at once */
  			addr = bm + (cur >> 3);
  			if (*addr != (__u32)(-1) && zero_bit == -1)
  				zero_bit = cur + mb_find_next_zero_bit(addr, 32, 0);
  			*addr = 0;
  			cur += 32;
  			continue;
  		}
  		if (!mb_test_and_clear_bit(cur, bm) && zero_bit == -1)
  			zero_bit = cur;
  		cur++;
  	}
  
  	return zero_bit;
  }
  
  void ext4_set_bits(void *bm, int cur, int len)
  {
  	__u32 *addr;
  
  	len = cur + len;
  	while (cur < len) {
  		if ((cur & 31) == 0 && (len - cur) >= 32) {
  			/* fast path: set whole word at once */
  			addr = bm + (cur >> 3);
  			*addr = 0xffffffff;
  			cur += 32;
  			continue;
  		}
  		mb_set_bit(cur, bm);
  		cur++;
  	}
  }
  
  /*
   * _________________________________________________________________ */
  
  static inline int mb_buddy_adjust_border(int* bit, void* bitmap, int side)
  {
  	if (mb_test_bit(*bit + side, bitmap)) {
  		mb_clear_bit(*bit, bitmap);
  		(*bit) -= side;
  		return 1;
  	}
  	else {
  		(*bit) += side;
  		mb_set_bit(*bit, bitmap);
  		return -1;
  	}
  }
  
  static void mb_buddy_mark_free(struct ext4_buddy *e4b, int first, int last)
  {
  	int max;
  	int order = 1;
  	void *buddy = mb_find_buddy(e4b, order, &max);
  
  	while (buddy) {
  		void *buddy2;
  
  		/* Bits in range [first; last] are known to be set since
  		 * corresponding blocks were allocated. Bits in range
  		 * (first; last) will stay set because they form buddies on
  		 * upper layer. We just deal with borders if they don't
  		 * align with upper layer and then go up.
  		 * Releasing entire group is all about clearing
  		 * single bit of highest order buddy.
  		 */
  
  		/* Example:
  		 * ---------------------------------
  		 * |   1   |   1   |   1   |   1   |
  		 * ---------------------------------
  		 * | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
  		 * ---------------------------------
  		 *   0   1   2   3   4   5   6   7
  		 *      \_____________________/
  		 *
  		 * Neither [1] nor [6] is aligned to above layer.
  		 * Left neighbour [0] is free, so mark it busy,
  		 * decrease bb_counters and extend range to
  		 * [0; 6]
  		 * Right neighbour [7] is busy. It can't be coaleasced with [6], so
  		 * mark [6] free, increase bb_counters and shrink range to
  		 * [0; 5].
  		 * Then shift range to [0; 2], go up and do the same.
  		 */
  
  
  		if (first & 1)
  			e4b->bd_info->bb_counters[order] += mb_buddy_adjust_border(&first, buddy, -1);
  		if (!(last & 1))
  			e4b->bd_info->bb_counters[order] += mb_buddy_adjust_border(&last, buddy, 1);
  		if (first > last)
  			break;
  		order++;
  
  		if (first == last || !(buddy2 = mb_find_buddy(e4b, order, &max))) {
  			mb_clear_bits(buddy, first, last - first + 1);
  			e4b->bd_info->bb_counters[order - 1] += last - first + 1;
  			break;
  		}
  		first >>= 1;
  		last >>= 1;
  		buddy = buddy2;
  	}
  }
  
  static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
  			   int first, int count)
  {
  	int left_is_free = 0;
  	int right_is_free = 0;
  	int block;
  	int last = first + count - 1;
  	struct super_block *sb = e4b->bd_sb;
  
  	if (WARN_ON(count == 0))
  		return;
  	BUG_ON(last >= (sb->s_blocksize << 3));
  	assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));
  	/* Don't bother if the block group is corrupt. */
  	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info)))
  		return;
  
  	mb_check_buddy(e4b);
  	mb_free_blocks_double(inode, e4b, first, count);
  
  	e4b->bd_info->bb_free += count;
  	if (first < e4b->bd_info->bb_first_free)
  		e4b->bd_info->bb_first_free = first;
  
  	/* access memory sequentially: check left neighbour,
  	 * clear range and then check right neighbour
  	 */
  	if (first != 0)
  		left_is_free = !mb_test_bit(first - 1, e4b->bd_bitmap);
  	block = mb_test_and_clear_bits(e4b->bd_bitmap, first, count);
  	if (last + 1 < EXT4_SB(sb)->s_mb_maxs[0])
  		right_is_free = !mb_test_bit(last + 1, e4b->bd_bitmap);
  
  	if (unlikely(block != -1)) {
  		struct ext4_sb_info *sbi = EXT4_SB(sb);
  		ext4_fsblk_t blocknr;
  
  		blocknr = ext4_group_first_block_no(sb, e4b->bd_group);
  		blocknr += EXT4_C2B(EXT4_SB(sb), block);
  		ext4_grp_locked_error(sb, e4b->bd_group,
  				      inode ? inode->i_ino : 0,
  				      blocknr,
  				      "freeing already freed block "
  				      "(bit %u); block bitmap corrupt.",
  				      block);
  		if (!EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info))
  			percpu_counter_sub(&sbi->s_freeclusters_counter,
  					   e4b->bd_info->bb_free);
  		/* Mark the block group as corrupt. */
  		set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
  			&e4b->bd_info->bb_state);
  		mb_regenerate_buddy(e4b);
  		goto done;
  	}
  
  	/* let's maintain fragments counter */
  	if (left_is_free && right_is_free)
  		e4b->bd_info->bb_fragments--;
  	else if (!left_is_free && !right_is_free)
  		e4b->bd_info->bb_fragments++;
  
  	/* buddy[0] == bd_bitmap is a special case, so handle
  	 * it right away and let mb_buddy_mark_free stay free of
  	 * zero order checks.
  	 * Check if neighbours are to be coaleasced,
  	 * adjust bitmap bb_counters and borders appropriately.
  	 */
  	if (first & 1) {
  		first += !left_is_free;
  		e4b->bd_info->bb_counters[0] += left_is_free ? -1 : 1;
  	}
  	if (!(last & 1)) {
  		last -= !right_is_free;
  		e4b->bd_info->bb_counters[0] += right_is_free ? -1 : 1;
  	}
  
  	if (first <= last)
  		mb_buddy_mark_free(e4b, first >> 1, last >> 1);
  
  done:
  	mb_set_largest_free_order(sb, e4b->bd_info);
  	mb_check_buddy(e4b);
  }
  
  static int mb_find_extent(struct ext4_buddy *e4b, int block,
  				int needed, struct ext4_free_extent *ex)
  {
  	int next = block;
  	int max, order;
  	void *buddy;
  
  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
  	BUG_ON(ex == NULL);
  
  	buddy = mb_find_buddy(e4b, 0, &max);
  	BUG_ON(buddy == NULL);
  	BUG_ON(block >= max);
  	if (mb_test_bit(block, buddy)) {
  		ex->fe_len = 0;
  		ex->fe_start = 0;
  		ex->fe_group = 0;
  		return 0;
  	}
  
  	/* find actual order */
  	order = mb_find_order_for_block(e4b, block);
  	block = block >> order;
  
  	ex->fe_len = 1 << order;
  	ex->fe_start = block << order;
  	ex->fe_group = e4b->bd_group;
  
  	/* calc difference from given start */
  	next = next - ex->fe_start;
  	ex->fe_len -= next;
  	ex->fe_start += next;
  
  	while (needed > ex->fe_len &&
  	       mb_find_buddy(e4b, order, &max)) {
  
  		if (block + 1 >= max)
  			break;
  
  		next = (block + 1) * (1 << order);
  		if (mb_test_bit(next, e4b->bd_bitmap))
  			break;
  
  		order = mb_find_order_for_block(e4b, next);
  
  		block = next >> order;
  		ex->fe_len += 1 << order;
  	}
  
  	BUG_ON(ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3)));
  	return ex->fe_len;
  }
  
  static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
  {
  	int ord;
  	int mlen = 0;
  	int max = 0;
  	int cur;
  	int start = ex->fe_start;
  	int len = ex->fe_len;
  	unsigned ret = 0;
  	int len0 = len;
  	void *buddy;
  
  	BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3));
  	BUG_ON(e4b->bd_group != ex->fe_group);
  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));
  	mb_check_buddy(e4b);
  	mb_mark_used_double(e4b, start, len);
  
  	e4b->bd_info->bb_free -= len;
  	if (e4b->bd_info->bb_first_free == start)
  		e4b->bd_info->bb_first_free += len;
  
  	/* let's maintain fragments counter */
  	if (start != 0)
  		mlen = !mb_test_bit(start - 1, e4b->bd_bitmap);
  	if (start + len < EXT4_SB(e4b->bd_sb)->s_mb_maxs[0])
  		max = !mb_test_bit(start + len, e4b->bd_bitmap);
  	if (mlen && max)
  		e4b->bd_info->bb_fragments++;
  	else if (!mlen && !max)
  		e4b->bd_info->bb_fragments--;
  
  	/* let's maintain buddy itself */
  	while (len) {
  		ord = mb_find_order_for_block(e4b, start);
  
  		if (((start >> ord) << ord) == start && len >= (1 << ord)) {
  			/* the whole chunk may be allocated at once! */
  			mlen = 1 << ord;
  			buddy = mb_find_buddy(e4b, ord, &max);
  			BUG_ON((start >> ord) >= max);
  			mb_set_bit(start >> ord, buddy);
  			e4b->bd_info->bb_counters[ord]--;
  			start += mlen;
  			len -= mlen;
  			BUG_ON(len < 0);
  			continue;
  		}
  
  		/* store for history */
  		if (ret == 0)
  			ret = len | (ord << 16);
  
  		/* we have to split large buddy */
  		BUG_ON(ord <= 0);
  		buddy = mb_find_buddy(e4b, ord, &max);
  		mb_set_bit(start >> ord, buddy);
  		e4b->bd_info->bb_counters[ord]--;
  
  		ord--;
  		cur = (start >> ord) & ~1U;
  		buddy = mb_find_buddy(e4b, ord, &max);
  		mb_clear_bit(cur, buddy);
  		mb_clear_bit(cur + 1, buddy);
  		e4b->bd_info->bb_counters[ord]++;
  		e4b->bd_info->bb_counters[ord]++;
  	}
  	mb_set_largest_free_order(e4b->bd_sb, e4b->bd_info);
  
  	ext4_set_bits(e4b->bd_bitmap, ex->fe_start, len0);
  	mb_check_buddy(e4b);
  
  	return ret;
  }
  
  /*
   * Must be called under group lock!
   */
  static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	int ret;
  
  	BUG_ON(ac->ac_b_ex.fe_group != e4b->bd_group);
  	BUG_ON(ac->ac_status == AC_STATUS_FOUND);
  
  	ac->ac_b_ex.fe_len = min(ac->ac_b_ex.fe_len, ac->ac_g_ex.fe_len);
  	ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical;
  	ret = mb_mark_used(e4b, &ac->ac_b_ex);
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_tail = ret & 0xffff;
  	ac->ac_buddy = ret >> 16;
  
  	/*
  	 * take the page reference. We want the page to be pinned
  	 * so that we don't get a ext4_mb_init_cache_call for this
  	 * group until we update the bitmap. That would mean we
  	 * double allocate blocks. The reference is dropped
  	 * in ext4_mb_release_context
  	 */
  	ac->ac_bitmap_page = e4b->bd_bitmap_page;
  	get_page(ac->ac_bitmap_page);
  	ac->ac_buddy_page = e4b->bd_buddy_page;
  	get_page(ac->ac_buddy_page);
  	/* store last allocated for subsequent stream allocation */
  	if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
  		spin_lock(&sbi->s_md_lock);
  		sbi->s_mb_last_group = ac->ac_f_ex.fe_group;
  		sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
  		spin_unlock(&sbi->s_md_lock);
  	}
  }
  
  /*
   * regular allocator, for general purposes allocation
   */
  
  static void ext4_mb_check_limits(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b,
  					int finish_group)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	struct ext4_free_extent *bex = &ac->ac_b_ex;
  	struct ext4_free_extent *gex = &ac->ac_g_ex;
  	struct ext4_free_extent ex;
  	int max;
  
  	if (ac->ac_status == AC_STATUS_FOUND)
  		return;
  	/*
  	 * We don't want to scan for a whole year
  	 */
  	if (ac->ac_found > sbi->s_mb_max_to_scan &&
  			!(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		ac->ac_status = AC_STATUS_BREAK;
  		return;
  	}
  
  	/*
  	 * Haven't found good chunk so far, let's continue
  	 */
  	if (bex->fe_len < gex->fe_len)
  		return;
  
  	if ((finish_group || ac->ac_found > sbi->s_mb_min_to_scan)
  			&& bex->fe_group == e4b->bd_group) {
  		/* recheck chunk's availability - we don't know
  		 * when it was found (within this lock-unlock
  		 * period or not) */
  		max = mb_find_extent(e4b, bex->fe_start, gex->fe_len, &ex);
  		if (max >= gex->fe_len) {
  			ext4_mb_use_best_found(ac, e4b);
  			return;
  		}
  	}
  }
  
  /*
   * The routine checks whether found extent is good enough. If it is,
   * then the extent gets marked used and flag is set to the context
   * to stop scanning. Otherwise, the extent is compared with the
   * previous found extent and if new one is better, then it's stored
   * in the context. Later, the best found extent will be used, if
   * mballoc can't find good enough extent.
   *
   * FIXME: real allocation policy is to be designed yet!
   */
  static void ext4_mb_measure_extent(struct ext4_allocation_context *ac,
  					struct ext4_free_extent *ex,
  					struct ext4_buddy *e4b)
  {
  	struct ext4_free_extent *bex = &ac->ac_b_ex;
  	struct ext4_free_extent *gex = &ac->ac_g_ex;
  
  	BUG_ON(ex->fe_len <= 0);
  	BUG_ON(ex->fe_len > EXT4_CLUSTERS_PER_GROUP(ac->ac_sb));
  	BUG_ON(ex->fe_start >= EXT4_CLUSTERS_PER_GROUP(ac->ac_sb));
  	BUG_ON(ac->ac_status != AC_STATUS_CONTINUE);
  
  	ac->ac_found++;
  
  	/*
  	 * The special case - take what you catch first
  	 */
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		*bex = *ex;
  		ext4_mb_use_best_found(ac, e4b);
  		return;
  	}
  
  	/*
  	 * Let's check whether the chuck is good enough
  	 */
  	if (ex->fe_len == gex->fe_len) {
  		*bex = *ex;
  		ext4_mb_use_best_found(ac, e4b);
  		return;
  	}
  
  	/*
  	 * If this is first found extent, just store it in the context
  	 */
  	if (bex->fe_len == 0) {
  		*bex = *ex;
  		return;
  	}
  
  	/*
  	 * If new found extent is better, store it in the context
  	 */
  	if (bex->fe_len < gex->fe_len) {
  		/* if the request isn't satisfied, any found extent
  		 * larger than previous best one is better */
  		if (ex->fe_len > bex->fe_len)
  			*bex = *ex;
  	} else if (ex->fe_len > gex->fe_len) {
  		/* if the request is satisfied, then we try to find
  		 * an extent that still satisfy the request, but is
  		 * smaller than previous one */
  		if (ex->fe_len < bex->fe_len)
  			*bex = *ex;
  	}
  
  	ext4_mb_check_limits(ac, e4b, 0);
  }
  
  static noinline_for_stack
  int ext4_mb_try_best_found(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b)
  {
  	struct ext4_free_extent ex = ac->ac_b_ex;
  	ext4_group_t group = ex.fe_group;
  	int max;
  	int err;
  
  	BUG_ON(ex.fe_len <= 0);
  	err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
  	if (err)
  		return err;
  
  	ext4_lock_group(ac->ac_sb, group);
  	max = mb_find_extent(e4b, ex.fe_start, ex.fe_len, &ex);
  
  	if (max > 0) {
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	}
  
  	ext4_unlock_group(ac->ac_sb, group);
  	ext4_mb_unload_buddy(e4b);
  
  	return 0;
  }
  
  static noinline_for_stack
  int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,
  				struct ext4_buddy *e4b)
  {
  	ext4_group_t group = ac->ac_g_ex.fe_group;
  	int max;
  	int err;
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
  	struct ext4_free_extent ex;
  
  	if (!(ac->ac_flags & EXT4_MB_HINT_TRY_GOAL))
  		return 0;
  	if (grp->bb_free == 0)
  		return 0;
  
  	err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
  	if (err)
  		return err;
  
  	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(e4b->bd_info))) {
  		ext4_mb_unload_buddy(e4b);
  		return 0;
  	}
  
  	ext4_lock_group(ac->ac_sb, group);
  	max = mb_find_extent(e4b, ac->ac_g_ex.fe_start,
  			     ac->ac_g_ex.fe_len, &ex);
  	ex.fe_logical = 0xDEADFA11; /* debug value */
  
  	if (max >= ac->ac_g_ex.fe_len && ac->ac_g_ex.fe_len == sbi->s_stripe) {
  		ext4_fsblk_t start;
  
  		start = ext4_group_first_block_no(ac->ac_sb, e4b->bd_group) +
  			ex.fe_start;
  		/* use do_div to get remainder (would be 64-bit modulo) */
  		if (do_div(start, sbi->s_stripe) == 0) {
  			ac->ac_found++;
  			ac->ac_b_ex = ex;
  			ext4_mb_use_best_found(ac, e4b);
  		}
  	} else if (max >= ac->ac_g_ex.fe_len) {
  		BUG_ON(ex.fe_len <= 0);
  		BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
  		BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
  		ac->ac_found++;
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	} else if (max > 0 && (ac->ac_flags & EXT4_MB_HINT_MERGE)) {
  		/* Sometimes, caller may want to merge even small
  		 * number of blocks to an existing extent */
  		BUG_ON(ex.fe_len <= 0);
  		BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
  		BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
  		ac->ac_found++;
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	}
  	ext4_unlock_group(ac->ac_sb, group);
  	ext4_mb_unload_buddy(e4b);
  
  	return 0;
  }
  
  /*
   * The routine scans buddy structures (not bitmap!) from given order
   * to max order and tries to find big enough chunk to satisfy the req
   */
  static noinline_for_stack
  void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_group_info *grp = e4b->bd_info;
  	void *buddy;
  	int i;
  	int k;
  	int max;
  
  	BUG_ON(ac->ac_2order <= 0);
  	for (i = ac->ac_2order; i <= sb->s_blocksize_bits + 1; i++) {
  		if (grp->bb_counters[i] == 0)
  			continue;
  
  		buddy = mb_find_buddy(e4b, i, &max);
  		BUG_ON(buddy == NULL);
  
  		k = mb_find_next_zero_bit(buddy, max, 0);
  		BUG_ON(k >= max);
  
  		ac->ac_found++;
  
  		ac->ac_b_ex.fe_len = 1 << i;
  		ac->ac_b_ex.fe_start = k << i;
  		ac->ac_b_ex.fe_group = e4b->bd_group;
  
  		ext4_mb_use_best_found(ac, e4b);
  
  		BUG_ON(ac->ac_b_ex.fe_len != ac->ac_g_ex.fe_len);
  
  		if (EXT4_SB(sb)->s_mb_stats)
  			atomic_inc(&EXT4_SB(sb)->s_bal_2orders);
  
  		break;
  	}
  }
  
  /*
   * The routine scans the group and measures all found extents.
   * In order to optimize scanning, caller must pass number of
   * free blocks in the group, so the routine can know upper limit.
   */
  static noinline_for_stack
  void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	void *bitmap = e4b->bd_bitmap;
  	struct ext4_free_extent ex;
  	int i;
  	int free;
  
  	free = e4b->bd_info->bb_free;
  	BUG_ON(free <= 0);
  
  	i = e4b->bd_info->bb_first_free;
  
  	while (free && ac->ac_status == AC_STATUS_CONTINUE) {
  		i = mb_find_next_zero_bit(bitmap,
  						EXT4_CLUSTERS_PER_GROUP(sb), i);
  		if (i >= EXT4_CLUSTERS_PER_GROUP(sb)) {
  			/*
  			 * IF we have corrupt bitmap, we won't find any
  			 * free blocks even though group info says we
  			 * we have free blocks
  			 */
  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
  					"%d free clusters as per "
  					"group info. But bitmap says 0",
  					free);
  			break;
  		}
  
  		mb_find_extent(e4b, i, ac->ac_g_ex.fe_len, &ex);
  		BUG_ON(ex.fe_len <= 0);
  		if (free < ex.fe_len) {
  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
  					"%d free clusters as per "
  					"group info. But got %d blocks",
  					free, ex.fe_len);
  			/*
  			 * The number of free blocks differs. This mostly
  			 * indicate that the bitmap is corrupt. So exit
  			 * without claiming the space.
  			 */
  			break;
  		}
  		ex.fe_logical = 0xDEADC0DE; /* debug value */
  		ext4_mb_measure_extent(ac, &ex, e4b);
  
  		i += ex.fe_len;
  		free -= ex.fe_len;
  	}
  
  	ext4_mb_check_limits(ac, e4b, 1);
  }
  
  /*
   * This is a special case for storages like raid5
   * we try to find stripe-aligned chunks for stripe-size-multiple requests
   */
  static noinline_for_stack
  void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
  				 struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	void *bitmap = e4b->bd_bitmap;
  	struct ext4_free_extent ex;
  	ext4_fsblk_t first_group_block;
  	ext4_fsblk_t a;
  	ext4_grpblk_t i;
  	int max;
  
  	BUG_ON(sbi->s_stripe == 0);
  
  	/* find first stripe-aligned block in group */
  	first_group_block = ext4_group_first_block_no(sb, e4b->bd_group);
  
  	a = first_group_block + sbi->s_stripe - 1;
  	do_div(a, sbi->s_stripe);
  	i = (a * sbi->s_stripe) - first_group_block;
  
  	while (i < EXT4_CLUSTERS_PER_GROUP(sb)) {
  		if (!mb_test_bit(i, bitmap)) {
  			max = mb_find_extent(e4b, i, sbi->s_stripe, &ex);
  			if (max >= sbi->s_stripe) {
  				ac->ac_found++;
  				ex.fe_logical = 0xDEADF00D; /* debug value */
  				ac->ac_b_ex = ex;
  				ext4_mb_use_best_found(ac, e4b);
  				break;
  			}
  		}
  		i += sbi->s_stripe;
  	}
  }
  
  /*
   * This is now called BEFORE we load the buddy bitmap.
   * Returns either 1 or 0 indicating that the group is either suitable
   * for the allocation or not. In addition it can also return negative
   * error code when something goes wrong.
   */
  static int ext4_mb_good_group(struct ext4_allocation_context *ac,
  				ext4_group_t group, int cr)
  {
  	unsigned free, fragments;
  	int flex_size = ext4_flex_bg_size(EXT4_SB(ac->ac_sb));
  	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
  
  	BUG_ON(cr < 0 || cr >= 4);
  
  	free = grp->bb_free;
  	if (free == 0)
  		return 0;
  	if (cr <= 2 && free < ac->ac_g_ex.fe_len)
  		return 0;
  
  	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(grp)))
  		return 0;
  
  	/* We only do this if the grp has never been initialized */
  	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  		int ret = ext4_mb_init_group(ac->ac_sb, group, GFP_NOFS);
  		if (ret)
  			return ret;
  	}
  
  	fragments = grp->bb_fragments;
  	if (fragments == 0)
  		return 0;
  
  	switch (cr) {
  	case 0:
  		BUG_ON(ac->ac_2order == 0);
  
  		/* Avoid using the first bg of a flexgroup for data files */
  		if ((ac->ac_flags & EXT4_MB_HINT_DATA) &&
  		    (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) &&
  		    ((group % flex_size) == 0))
  			return 0;
  
  		if ((ac->ac_2order > ac->ac_sb->s_blocksize_bits+1) ||
  		    (free / fragments) >= ac->ac_g_ex.fe_len)
  			return 1;
  
  		if (grp->bb_largest_free_order < ac->ac_2order)
  			return 0;
  
  		return 1;
  	case 1:
  		if ((free / fragments) >= ac->ac_g_ex.fe_len)
  			return 1;
  		break;
  	case 2:
  		if (free >= ac->ac_g_ex.fe_len)
  			return 1;
  		break;
  	case 3:
  		return 1;
  	default:
  		BUG();
  	}
  
  	return 0;
  }
  
  static noinline_for_stack int
  ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
  {
  	ext4_group_t ngroups, group, i;
  	int cr;
  	int err = 0, first_err = 0;
  	struct ext4_sb_info *sbi;
  	struct super_block *sb;
  	struct ext4_buddy e4b;
  
  	sb = ac->ac_sb;
  	sbi = EXT4_SB(sb);
  	ngroups = ext4_get_groups_count(sb);
  	/* non-extent files are limited to low blocks/groups */
  	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))
  		ngroups = sbi->s_blockfile_groups;
  
  	BUG_ON(ac->ac_status == AC_STATUS_FOUND);
  
  	/* first, try the goal */
  	err = ext4_mb_find_by_goal(ac, &e4b);
  	if (err || ac->ac_status == AC_STATUS_FOUND)
  		goto out;
  
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
  		goto out;
  
  	/*
  	 * ac->ac2_order is set only if the fe_len is a power of 2
  	 * if ac2_order is set we also set criteria to 0 so that we
  	 * try exact allocation using buddy.
  	 */
  	i = fls(ac->ac_g_ex.fe_len);
  	ac->ac_2order = 0;
  	/*
  	 * We search using buddy data only if the order of the request
  	 * is greater than equal to the sbi_s_mb_order2_reqs
  	 * You can tune it via /sys/fs/ext4/<partition>/mb_order2_req
  	 */
  	if (i >= sbi->s_mb_order2_reqs) {
  		/*
  		 * This should tell if fe_len is exactly power of 2
  		 */
  		if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0)
  			ac->ac_2order = i - 1;
  	}
  
  	/* if stream allocation is enabled, use global goal */
  	if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {
  		/* TBD: may be hot point */
  		spin_lock(&sbi->s_md_lock);
  		ac->ac_g_ex.fe_group = sbi->s_mb_last_group;
  		ac->ac_g_ex.fe_start = sbi->s_mb_last_start;
  		spin_unlock(&sbi->s_md_lock);
  	}
  
  	/* Let's just scan groups to find more-less suitable blocks */
  	cr = ac->ac_2order ? 0 : 1;
  	/*
  	 * cr == 0 try to get exact allocation,
  	 * cr == 3  try to get anything
  	 */
  repeat:
  	for (; cr < 4 && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
  		ac->ac_criteria = cr;
  		/*
  		 * searching for the right group start
  		 * from the goal value specified
  		 */
  		group = ac->ac_g_ex.fe_group;
  
  		for (i = 0; i < ngroups; group++, i++) {
  			int ret = 0;
  			cond_resched();
  			/*
  			 * Artificially restricted ngroups for non-extent
  			 * files makes group > ngroups possible on first loop.
  			 */
  			if (group >= ngroups)
  				group = 0;
  
  			/* This now checks without needing the buddy page */
  			ret = ext4_mb_good_group(ac, group, cr);
  			if (ret <= 0) {
  				if (!first_err)
  					first_err = ret;
  				continue;
  			}
  
  			err = ext4_mb_load_buddy(sb, group, &e4b);
  			if (err)
  				goto out;
  
  			ext4_lock_group(sb, group);
  
  			/*
  			 * We need to check again after locking the
  			 * block group
  			 */
  			ret = ext4_mb_good_group(ac, group, cr);
  			if (ret <= 0) {
  				ext4_unlock_group(sb, group);
  				ext4_mb_unload_buddy(&e4b);
  				if (!first_err)
  					first_err = ret;
  				continue;
  			}
  
  			ac->ac_groups_scanned++;
  			if (cr == 0 && ac->ac_2order < sb->s_blocksize_bits+2)
  				ext4_mb_simple_scan_group(ac, &e4b);
  			else if (cr == 1 && sbi->s_stripe &&
  					!(ac->ac_g_ex.fe_len % sbi->s_stripe))
  				ext4_mb_scan_aligned(ac, &e4b);
  			else
  				ext4_mb_complex_scan_group(ac, &e4b);
  
  			ext4_unlock_group(sb, group);
  			ext4_mb_unload_buddy(&e4b);
  
  			if (ac->ac_status != AC_STATUS_CONTINUE)
  				break;
  		}
  	}
  
  	if (ac->ac_b_ex.fe_len > 0 && ac->ac_status != AC_STATUS_FOUND &&
  	    !(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		/*
  		 * We've been searching too long. Let's try to allocate
  		 * the best chunk we've found so far
  		 */
  
  		ext4_mb_try_best_found(ac, &e4b);
  		if (ac->ac_status != AC_STATUS_FOUND) {
  			/*
  			 * Someone more lucky has already allocated it.
  			 * The only thing we can do is just take first
  			 * found block(s)
  			printk(KERN_DEBUG "EXT4-fs: someone won our chunk\n");
  			 */
  			ac->ac_b_ex.fe_group = 0;
  			ac->ac_b_ex.fe_start = 0;
  			ac->ac_b_ex.fe_len = 0;
  			ac->ac_status = AC_STATUS_CONTINUE;
  			ac->ac_flags |= EXT4_MB_HINT_FIRST;
  			cr = 3;
  			atomic_inc(&sbi->s_mb_lost_chunks);
  			goto repeat;
  		}
  	}
  out:
  	if (!err && ac->ac_status != AC_STATUS_FOUND && first_err)
  		err = first_err;
  	return err;
  }
  
  static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
  {
  	struct super_block *sb = seq->private;
  	ext4_group_t group;
  
  	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
  		return NULL;
  	group = *pos + 1;
  	return (void *) ((unsigned long) group);
  }
  
  static void *ext4_mb_seq_groups_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct super_block *sb = seq->private;
  	ext4_group_t group;
  
  	++*pos;
  	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
  		return NULL;
  	group = *pos + 1;
  	return (void *) ((unsigned long) group);
  }
  
  static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
  {
  	struct super_block *sb = seq->private;
  	ext4_group_t group = (ext4_group_t) ((unsigned long) v);
  	int i;
  	int err, buddy_loaded = 0;
  	struct ext4_buddy e4b;
  	struct ext4_group_info *grinfo;
  	struct sg {
  		struct ext4_group_info info;
  		ext4_grpblk_t counters[EXT4_MAX_BLOCK_LOG_SIZE + 2];
  	} sg;
  
  	group--;
  	if (group == 0)
  		seq_puts(seq, "#group: free  frags first ["
  			      " 2^0   2^1   2^2   2^3   2^4   2^5   2^6  "
  			      " 2^7   2^8   2^9   2^10  2^11  2^12  2^13  ]");
  
  	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
  		sizeof(struct ext4_group_info);
  	grinfo = ext4_get_group_info(sb, group);
  	/* Load the group info in memory only if not already loaded. */
  	if (unlikely(EXT4_MB_GRP_NEED_INIT(grinfo))) {
  		err = ext4_mb_load_buddy(sb, group, &e4b);
  		if (err) {
  			seq_printf(seq, "#%-5u: I/O error\n", group);
  			return 0;
  		}
  		buddy_loaded = 1;
  	}
  
  	memcpy(&sg, ext4_get_group_info(sb, group), i);
  
  	if (buddy_loaded)
  		ext4_mb_unload_buddy(&e4b);
  
  	seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,
  			sg.info.bb_fragments, sg.info.bb_first_free);
  	for (i = 0; i <= 13; i++)
  		seq_printf(seq, " %-5u", i <= sb->s_blocksize_bits + 1 ?
  				sg.info.bb_counters[i] : 0);
  	seq_printf(seq, " ]\n");
  
  	return 0;
  }
  
  static void ext4_mb_seq_groups_stop(struct seq_file *seq, void *v)
  {
  }
  
  static const struct seq_operations ext4_mb_seq_groups_ops = {
  	.start  = ext4_mb_seq_groups_start,
  	.next   = ext4_mb_seq_groups_next,
  	.stop   = ext4_mb_seq_groups_stop,
  	.show   = ext4_mb_seq_groups_show,
  };
  
  static int ext4_mb_seq_groups_open(struct inode *inode, struct file *file)
  {
  	struct super_block *sb = PDE_DATA(inode);
  	int rc;
  
  	rc = seq_open(file, &ext4_mb_seq_groups_ops);
  	if (rc == 0) {
  		struct seq_file *m = file->private_data;
  		m->private = sb;
  	}
  	return rc;
  
  }
  
  const struct file_operations ext4_seq_mb_groups_fops = {
  	.owner		= THIS_MODULE,
  	.open		= ext4_mb_seq_groups_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };
  
  static struct kmem_cache *get_groupinfo_cache(int blocksize_bits)
  {
  	int cache_index = blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE;
  	struct kmem_cache *cachep = ext4_groupinfo_caches[cache_index];
  
  	BUG_ON(!cachep);
  	return cachep;
  }
  
  /*
   * Allocate the top-level s_group_info array for the specified number
   * of groups
   */
  int ext4_mb_alloc_groupinfo(struct super_block *sb, ext4_group_t ngroups)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	unsigned size;
  	struct ext4_group_info ***new_groupinfo;
  
  	size = (ngroups + EXT4_DESC_PER_BLOCK(sb) - 1) >>
  		EXT4_DESC_PER_BLOCK_BITS(sb);
  	if (size <= sbi->s_group_info_size)
  		return 0;
  
  	size = roundup_pow_of_two(sizeof(*sbi->s_group_info) * size);
  	new_groupinfo = ext4_kvzalloc(size, GFP_KERNEL);
  	if (!new_groupinfo) {
  		ext4_msg(sb, KERN_ERR, "can't allocate buddy meta group");
  		return -ENOMEM;
  	}
  	if (sbi->s_group_info) {
  		memcpy(new_groupinfo, sbi->s_group_info,
  		       sbi->s_group_info_size * sizeof(*sbi->s_group_info));
  		kvfree(sbi->s_group_info);
  	}
  	sbi->s_group_info = new_groupinfo;
  	sbi->s_group_info_size = size / sizeof(*sbi->s_group_info);
  	ext4_debug("allocated s_groupinfo array for %d meta_bg's\n", 
  		   sbi->s_group_info_size);
  	return 0;
  }
  
  /* Create and initialize ext4_group_info data for the given group. */
  int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
  			  struct ext4_group_desc *desc)
  {
  	int i;
  	int metalen = 0;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_group_info **meta_group_info;
  	struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits);
  
  	/*
  	 * First check if this group is the first of a reserved block.
  	 * If it's true, we have to allocate a new table of pointers
  	 * to ext4_group_info structures
  	 */
  	if (group % EXT4_DESC_PER_BLOCK(sb) == 0) {
  		metalen = sizeof(*meta_group_info) <<
  			EXT4_DESC_PER_BLOCK_BITS(sb);
  		meta_group_info = kmalloc(metalen, GFP_NOFS);
  		if (meta_group_info == NULL) {
  			ext4_msg(sb, KERN_ERR, "can't allocate mem "
  				 "for a buddy group");
  			goto exit_meta_group_info;
  		}
  		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)] =
  			meta_group_info;
  	}
  
  	meta_group_info =
  		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)];
  	i = group & (EXT4_DESC_PER_BLOCK(sb) - 1);
  
  	meta_group_info[i] = kmem_cache_zalloc(cachep, GFP_NOFS);
  	if (meta_group_info[i] == NULL) {
  		ext4_msg(sb, KERN_ERR, "can't allocate buddy mem");
  		goto exit_group_info;
  	}
  	set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT,
  		&(meta_group_info[i]->bb_state));
  
  	/*
  	 * initialize bb_free to be able to skip
  	 * empty groups without initialization
  	 */
  	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
  		meta_group_info[i]->bb_free =
  			ext4_free_clusters_after_init(sb, group, desc);
  	} else {
  		meta_group_info[i]->bb_free =
  			ext4_free_group_clusters(sb, desc);
  	}
  
  	INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
  	init_rwsem(&meta_group_info[i]->alloc_sem);
  	meta_group_info[i]->bb_free_root = RB_ROOT;
  	meta_group_info[i]->bb_largest_free_order = -1;  /* uninit */
  
  #ifdef DOUBLE_CHECK
  	{
  		struct buffer_head *bh;
  		meta_group_info[i]->bb_bitmap =
  			kmalloc(sb->s_blocksize, GFP_NOFS);
  		BUG_ON(meta_group_info[i]->bb_bitmap == NULL);
  		bh = ext4_read_block_bitmap(sb, group);
  		BUG_ON(IS_ERR_OR_NULL(bh));
  		memcpy(meta_group_info[i]->bb_bitmap, bh->b_data,
  			sb->s_blocksize);
  		put_bh(bh);
  	}
  #endif
  
  	return 0;
  
  exit_group_info:
  	/* If a meta_group_info table has been allocated, release it now */
  	if (group % EXT4_DESC_PER_BLOCK(sb) == 0) {
  		kfree(sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)]);
  		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)] = NULL;
  	}
  exit_meta_group_info:
  	return -ENOMEM;
  } /* ext4_mb_add_groupinfo */
  
  static int ext4_mb_init_backend(struct super_block *sb)
  {
  	ext4_group_t ngroups = ext4_get_groups_count(sb);
  	ext4_group_t i;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	int err;
  	struct ext4_group_desc *desc;
  	struct kmem_cache *cachep;
  
  	err = ext4_mb_alloc_groupinfo(sb, ngroups);
  	if (err)
  		return err;
  
  	sbi->s_buddy_cache = new_inode(sb);
  	if (sbi->s_buddy_cache == NULL) {
  		ext4_msg(sb, KERN_ERR, "can't get new inode");
  		goto err_freesgi;
  	}
  	/* To avoid potentially colliding with an valid on-disk inode number,
  	 * use EXT4_BAD_INO for the buddy cache inode number.  This inode is
  	 * not in the inode hash, so it should never be found by iget(), but
  	 * this will avoid confusion if it ever shows up during debugging. */
  	sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;
  	EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;
  	for (i = 0; i < ngroups; i++) {
  		desc = ext4_get_group_desc(sb, i, NULL);
  		if (desc == NULL) {
  			ext4_msg(sb, KERN_ERR, "can't read descriptor %u", i);
  			goto err_freebuddy;
  		}
  		if (ext4_mb_add_groupinfo(sb, i, desc) != 0)
  			goto err_freebuddy;
  	}
  
  	return 0;
  
  err_freebuddy:
  	cachep = get_groupinfo_cache(sb->s_blocksize_bits);
  	while (i-- > 0)
  		kmem_cache_free(cachep, ext4_get_group_info(sb, i));
  	i = sbi->s_group_info_size;
  	while (i-- > 0)
  		kfree(sbi->s_group_info[i]);
  	iput(sbi->s_buddy_cache);
  err_freesgi:
  	kvfree(sbi->s_group_info);
  	return -ENOMEM;
  }
  
  static void ext4_groupinfo_destroy_slabs(void)
  {
  	int i;
  
  	for (i = 0; i < NR_GRPINFO_CACHES; i++) {
  		if (ext4_groupinfo_caches[i])
  			kmem_cache_destroy(ext4_groupinfo_caches[i]);
  		ext4_groupinfo_caches[i] = NULL;
  	}
  }
  
  static int ext4_groupinfo_create_slab(size_t size)
  {
  	static DEFINE_MUTEX(ext4_grpinfo_slab_create_mutex);
  	int slab_size;
  	int blocksize_bits = order_base_2(size);
  	int cache_index = blocksize_bits - EXT4_MIN_BLOCK_LOG_SIZE;
  	struct kmem_cache *cachep;
  
  	if (cache_index >= NR_GRPINFO_CACHES)
  		return -EINVAL;
  
  	if (unlikely(cache_index < 0))
  		cache_index = 0;
  
  	mutex_lock(&ext4_grpinfo_slab_create_mutex);
  	if (ext4_groupinfo_caches[cache_index]) {
  		mutex_unlock(&ext4_grpinfo_slab_create_mutex);
  		return 0;	/* Already created */
  	}
  
  	slab_size = offsetof(struct ext4_group_info,
  				bb_counters[blocksize_bits + 2]);
  
  	cachep = kmem_cache_create(ext4_groupinfo_slab_names[cache_index],
  					slab_size, 0, SLAB_RECLAIM_ACCOUNT,
  					NULL);
  
  	ext4_groupinfo_caches[cache_index] = cachep;
  
  	mutex_unlock(&ext4_grpinfo_slab_create_mutex);
  	if (!cachep) {
  		printk(KERN_EMERG
  		       "EXT4-fs: no memory for groupinfo slab cache\n");
  		return -ENOMEM;
  	}
  
  	return 0;
  }
  
  int ext4_mb_init(struct super_block *sb)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	unsigned i, j;
  	unsigned offset, offset_incr;
  	unsigned max;
  	int ret;
  
  	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets);
  
  	sbi->s_mb_offsets = kmalloc(i, GFP_KERNEL);
  	if (sbi->s_mb_offsets == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_maxs);
  	sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
  	if (sbi->s_mb_maxs == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	ret = ext4_groupinfo_create_slab(sb->s_blocksize);
  	if (ret < 0)
  		goto out;
  
  	/* order 0 is regular bitmap */
  	sbi->s_mb_maxs[0] = sb->s_blocksize << 3;
  	sbi->s_mb_offsets[0] = 0;
  
  	i = 1;
  	offset = 0;
  	offset_incr = 1 << (sb->s_blocksize_bits - 1);
  	max = sb->s_blocksize << 2;
  	do {
  		sbi->s_mb_offsets[i] = offset;
  		sbi->s_mb_maxs[i] = max;
  		offset += offset_incr;
  		offset_incr = offset_incr >> 1;
  		max = max >> 1;
  		i++;
  	} while (i <= sb->s_blocksize_bits + 1);
  
  	spin_lock_init(&sbi->s_md_lock);
  	spin_lock_init(&sbi->s_bal_lock);
  
  	sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;
  	sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;
  	sbi->s_mb_stats = MB_DEFAULT_STATS;
  	sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
  	sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;
  	/*
  	 * The default group preallocation is 512, which for 4k block
  	 * sizes translates to 2 megabytes.  However for bigalloc file
  	 * systems, this is probably too big (i.e, if the cluster size
  	 * is 1 megabyte, then group preallocation size becomes half a
  	 * gigabyte!).  As a default, we will keep a two megabyte
  	 * group pralloc size for cluster sizes up to 64k, and after
  	 * that, we will force a minimum group preallocation size of
  	 * 32 clusters.  This translates to 8 megs when the cluster
  	 * size is 256k, and 32 megs when the cluster size is 1 meg,
  	 * which seems reasonable as a default.
  	 */
  	sbi->s_mb_group_prealloc = max(MB_DEFAULT_GROUP_PREALLOC >>
  				       sbi->s_cluster_bits, 32);
  	/*
  	 * If there is a s_stripe > 1, then we set the s_mb_group_prealloc
  	 * to the lowest multiple of s_stripe which is bigger than
  	 * the s_mb_group_prealloc as determined above. We want
  	 * the preallocation size to be an exact multiple of the
  	 * RAID stripe size so that preallocations don't fragment
  	 * the stripes.
  	 */
  	if (sbi->s_stripe > 1) {
  		sbi->s_mb_group_prealloc = roundup(
  			sbi->s_mb_group_prealloc, sbi->s_stripe);
  	}
  
  	sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
  	if (sbi->s_locality_groups == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	for_each_possible_cpu(i) {
  		struct ext4_locality_group *lg;
  		lg = per_cpu_ptr(sbi->s_locality_groups, i);
  		mutex_init(&lg->lg_mutex);
  		for (j = 0; j < PREALLOC_TB_SIZE; j++)
  			INIT_LIST_HEAD(&lg->lg_prealloc_list[j]);
  		spin_lock_init(&lg->lg_prealloc_lock);
  	}
  
  	/* init file for buddy data */
  	ret = ext4_mb_init_backend(sb);
  	if (ret != 0)
  		goto out_free_locality_groups;
  
  	return 0;
  
  out_free_locality_groups:
  	free_percpu(sbi->s_locality_groups);
  	sbi->s_locality_groups = NULL;
  out:
  	kfree(sbi->s_mb_offsets);
  	sbi->s_mb_offsets = NULL;
  	kfree(sbi->s_mb_maxs);
  	sbi->s_mb_maxs = NULL;
  	return ret;
  }
  
  /* need to called with the ext4 group lock held */
  static void ext4_mb_cleanup_pa(struct ext4_group_info *grp)
  {
  	struct ext4_prealloc_space *pa;
  	struct list_head *cur, *tmp;
  	int count = 0;
  
  	list_for_each_safe(cur, tmp, &grp->bb_prealloc_list) {
  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		list_del(&pa->pa_group_list);
  		count++;
  		kmem_cache_free(ext4_pspace_cachep, pa);
  	}
  	if (count)
  		mb_debug(1, "mballoc: %u PAs left\n", count);
  
  }
  
  int ext4_mb_release(struct super_block *sb)
  {
  	ext4_group_t ngroups = ext4_get_groups_count(sb);
  	ext4_group_t i;
  	int num_meta_group_infos;
  	struct ext4_group_info *grinfo;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct kmem_cache *cachep = get_groupinfo_cache(sb->s_blocksize_bits);
  
  	if (sbi->s_group_info) {
  		for (i = 0; i < ngroups; i++) {
  			grinfo = ext4_get_group_info(sb, i);
  #ifdef DOUBLE_CHECK
  			kfree(grinfo->bb_bitmap);
  #endif
  			ext4_lock_group(sb, i);
  			ext4_mb_cleanup_pa(grinfo);
  			ext4_unlock_group(sb, i);
  			kmem_cache_free(cachep, grinfo);
  		}
  		num_meta_group_infos = (ngroups +
  				EXT4_DESC_PER_BLOCK(sb) - 1) >>
  			EXT4_DESC_PER_BLOCK_BITS(sb);
  		for (i = 0; i < num_meta_group_infos; i++)
  			kfree(sbi->s_group_info[i]);
  		kvfree(sbi->s_group_info);
  	}
  	kfree(sbi->s_mb_offsets);
  	kfree(sbi->s_mb_maxs);
  	iput(sbi->s_buddy_cache);
  	if (sbi->s_mb_stats) {
  		ext4_msg(sb, KERN_INFO,
  		       "mballoc: %u blocks %u reqs (%u success)",
  				atomic_read(&sbi->s_bal_allocated),
  				atomic_read(&sbi->s_bal_reqs),
  				atomic_read(&sbi->s_bal_success));
  		ext4_msg(sb, KERN_INFO,
  		      "mballoc: %u extents scanned, %u goal hits, "
  				"%u 2^N hits, %u breaks, %u lost",
  				atomic_read(&sbi->s_bal_ex_scanned),
  				atomic_read(&sbi->s_bal_goals),
  				atomic_read(&sbi->s_bal_2orders),
  				atomic_read(&sbi->s_bal_breaks),
  				atomic_read(&sbi->s_mb_lost_chunks));
  		ext4_msg(sb, KERN_INFO,
  		       "mballoc: %lu generated and it took %Lu",
  				sbi->s_mb_buddies_generated,
  				sbi->s_mb_generation_time);
  		ext4_msg(sb, KERN_INFO,
  		       "mballoc: %u preallocated, %u discarded",
  				atomic_read(&sbi->s_mb_preallocated),
  				atomic_read(&sbi->s_mb_discarded));
  	}
  
  	free_percpu(sbi->s_locality_groups);
  
  	return 0;
  }
  
  static inline int ext4_issue_discard(struct super_block *sb,
  		ext4_group_t block_group, ext4_grpblk_t cluster, int count)
  {
  	ext4_fsblk_t discard_block;
  
  	discard_block = (EXT4_C2B(EXT4_SB(sb), cluster) +
  			 ext4_group_first_block_no(sb, block_group));
  	count = EXT4_C2B(EXT4_SB(sb), count);
  	trace_ext4_discard_blocks(sb,
  			(unsigned long long) discard_block, count);
  	return sb_issue_discard(sb, discard_block, count, GFP_NOFS, 0);
  }
  
  /*
   * This function is called by the jbd2 layer once the commit has finished,
   * so we know we can free the blocks that were released with that commit.
   */
  static void ext4_free_data_callback(struct super_block *sb,
  				    struct ext4_journal_cb_entry *jce,
  				    int rc)
  {
  	struct ext4_free_data *entry = (struct ext4_free_data *)jce;
  	struct ext4_buddy e4b;
  	struct ext4_group_info *db;
  	int err, count = 0, count2 = 0;
  
  	mb_debug(1, "gonna free %u blocks in group %u (0x%p):",
  		 entry->efd_count, entry->efd_group, entry);
  
  	if (test_opt(sb, DISCARD)) {
  		err = ext4_issue_discard(sb, entry->efd_group,
  					 entry->efd_start_cluster,
  					 entry->efd_count);
  		if (err && err != -EOPNOTSUPP)
  			ext4_msg(sb, KERN_WARNING, "discard request in"
  				 " group:%d block:%d count:%d failed"
  				 " with %d", entry->efd_group,
  				 entry->efd_start_cluster,
  				 entry->efd_count, err);
  	}
  
  	err = ext4_mb_load_buddy(sb, entry->efd_group, &e4b);
  	/* we expect to find existing buddy because it's pinned */
  	BUG_ON(err != 0);
  
  
  	db = e4b.bd_info;
  	/* there are blocks to put in buddy to make them really free */
  	count += entry->efd_count;
  	count2++;
  	ext4_lock_group(sb, entry->efd_group);
  	/* Take it out of per group rb tree */
  	rb_erase(&entry->efd_node, &(db->bb_free_root));
  	mb_free_blocks(NULL, &e4b, entry->efd_start_cluster, entry->efd_count);
  
  	/*
  	 * Clear the trimmed flag for the group so that the next
  	 * ext4_trim_fs can trim it.
  	 * If the volume is mounted with -o discard, online discard
  	 * is supported and the free blocks will be trimmed online.
  	 */
  	if (!test_opt(sb, DISCARD))
  		EXT4_MB_GRP_CLEAR_TRIMMED(db);
  
  	if (!db->bb_free_root.rb_node) {
  		/* No more items in the per group rb tree
  		 * balance refcounts from ext4_mb_free_metadata()
  		 */
  		page_cache_release(e4b.bd_buddy_page);
  		page_cache_release(e4b.bd_bitmap_page);
  	}
  	ext4_unlock_group(sb, entry->efd_group);
  	kmem_cache_free(ext4_free_data_cachep, entry);
  	ext4_mb_unload_buddy(&e4b);
  
  	mb_debug(1, "freed %u blocks in %u structures\n", count, count2);
  }
  
  int __init ext4_init_mballoc(void)
  {
  	ext4_pspace_cachep = KMEM_CACHE(ext4_prealloc_space,
  					SLAB_RECLAIM_ACCOUNT);
  	if (ext4_pspace_cachep == NULL)
  		return -ENOMEM;
  
  	ext4_ac_cachep = KMEM_CACHE(ext4_allocation_context,
  				    SLAB_RECLAIM_ACCOUNT);
  	if (ext4_ac_cachep == NULL) {
  		kmem_cache_destroy(ext4_pspace_cachep);
  		return -ENOMEM;
  	}
  
  	ext4_free_data_cachep = KMEM_CACHE(ext4_free_data,
  					   SLAB_RECLAIM_ACCOUNT);
  	if (ext4_free_data_cachep == NULL) {
  		kmem_cache_destroy(ext4_pspace_cachep);
  		kmem_cache_destroy(ext4_ac_cachep);
  		return -ENOMEM;
  	}
  	return 0;
  }
  
  void ext4_exit_mballoc(void)
  {
  	/*
  	 * Wait for completion of call_rcu()'s on ext4_pspace_cachep
  	 * before destroying the slab cache.
  	 */
  	rcu_barrier();
  	kmem_cache_destroy(ext4_pspace_cachep);
  	kmem_cache_destroy(ext4_ac_cachep);
  	kmem_cache_destroy(ext4_free_data_cachep);
  	ext4_groupinfo_destroy_slabs();
  }
  
  
  /*
   * Check quota and mark chosen space (ac->ac_b_ex) non-free in bitmaps
   * Returns 0 if success or error code
   */
  static noinline_for_stack int
  ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
  				handle_t *handle, unsigned int reserv_clstrs)
  {
  	struct buffer_head *bitmap_bh = NULL;
  	struct ext4_group_desc *gdp;
  	struct buffer_head *gdp_bh;
  	struct ext4_sb_info *sbi;
  	struct super_block *sb;
  	ext4_fsblk_t block;
  	int err, len;
  
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(ac->ac_b_ex.fe_len <= 0);
  
  	sb = ac->ac_sb;
  	sbi = EXT4_SB(sb);
  
  	bitmap_bh = ext4_read_block_bitmap(sb, ac->ac_b_ex.fe_group);
  	if (IS_ERR(bitmap_bh)) {
  		err = PTR_ERR(bitmap_bh);
  		bitmap_bh = NULL;
  		goto out_err;
  	}
  
  	BUFFER_TRACE(bitmap_bh, "getting write access");
  	err = ext4_journal_get_write_access(handle, bitmap_bh);
  	if (err)
  		goto out_err;
  
  	err = -EIO;
  	gdp = ext4_get_group_desc(sb, ac->ac_b_ex.fe_group, &gdp_bh);
  	if (!gdp)
  		goto out_err;
  
  	ext4_debug("using block group %u(%d)\n", ac->ac_b_ex.fe_group,
  			ext4_free_group_clusters(sb, gdp));
  
  	BUFFER_TRACE(gdp_bh, "get_write_access");
  	err = ext4_journal_get_write_access(handle, gdp_bh);
  	if (err)
  		goto out_err;
  
  	block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  
  	len = EXT4_C2B(sbi, ac->ac_b_ex.fe_len);
  	if (!ext4_data_block_valid(sbi, block, len)) {
  		ext4_error(sb, "Allocating blocks %llu-%llu which overlap "
  			   "fs metadata", block, block+len);
  		/* File system mounted not to panic on error
  		 * Fix the bitmap and return EFSCORRUPTED
  		 * We leak some of the blocks here.
  		 */
  		ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  		ext4_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
  			      ac->ac_b_ex.fe_len);
  		ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  		err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
  		if (!err)
  			err = -EFSCORRUPTED;
  		goto out_err;
  	}
  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  #ifdef AGGRESSIVE_CHECK
  	{
  		int i;
  		for (i = 0; i < ac->ac_b_ex.fe_len; i++) {
  			BUG_ON(mb_test_bit(ac->ac_b_ex.fe_start + i,
  						bitmap_bh->b_data));
  		}
  	}
  #endif
  	ext4_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
  		      ac->ac_b_ex.fe_len);
  	if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
  		gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
  		ext4_free_group_clusters_set(sb, gdp,
  					     ext4_free_clusters_after_init(sb,
  						ac->ac_b_ex.fe_group, gdp));
  	}
  	len = ext4_free_group_clusters(sb, gdp) - ac->ac_b_ex.fe_len;
  	ext4_free_group_clusters_set(sb, gdp, len);
  	ext4_block_bitmap_csum_set(sb, ac->ac_b_ex.fe_group, gdp, bitmap_bh);
  	ext4_group_desc_csum_set(sb, ac->ac_b_ex.fe_group, gdp);
  
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  	percpu_counter_sub(&sbi->s_freeclusters_counter, ac->ac_b_ex.fe_len);
  	/*
  	 * Now reduce the dirty block count also. Should not go negative
  	 */
  	if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
  		/* release all the reserved blocks if non delalloc */
  		percpu_counter_sub(&sbi->s_dirtyclusters_counter,
  				   reserv_clstrs);
  
  	if (sbi->s_log_groups_per_flex) {
  		ext4_group_t flex_group = ext4_flex_group(sbi,
  							  ac->ac_b_ex.fe_group);
  		atomic64_sub(ac->ac_b_ex.fe_len,
  			     &sbi->s_flex_groups[flex_group].free_clusters);
  	}
  
  	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
  	if (err)
  		goto out_err;
  	err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);
  
  out_err:
  	brelse(bitmap_bh);
  	return err;
  }
  
  /*
   * here we normalize request for locality group
   * Group request are normalized to s_mb_group_prealloc, which goes to
   * s_strip if we set the same via mount option.
   * s_mb_group_prealloc can be configured via
   * /sys/fs/ext4/<partition>/mb_group_prealloc
   *
   * XXX: should we try to preallocate more than the group has now?
   */
  static void ext4_mb_normalize_group_request(struct ext4_allocation_context *ac)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_locality_group *lg = ac->ac_lg;
  
  	BUG_ON(lg == NULL);
  	ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc;
  	mb_debug(1, "#%u: goal %u blocks for locality group\n",
  		current->pid, ac->ac_g_ex.fe_len);
  }
  
  /*
   * Normalization means making request better in terms of
   * size and alignment
   */
  static noinline_for_stack void
  ext4_mb_normalize_request(struct ext4_allocation_context *ac,
  				struct ext4_allocation_request *ar)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	int bsbits, max;
  	ext4_lblk_t end;
  	loff_t size, start_off;
  	loff_t orig_size __maybe_unused;
  	ext4_lblk_t start;
  	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
  	struct ext4_prealloc_space *pa;
  
  	/* do normalize only data requests, metadata requests
  	   do not need preallocation */
  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
  		return;
  
  	/* sometime caller may want exact blocks */
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
  		return;
  
  	/* caller may indicate that preallocation isn't
  	 * required (it's a tail, for example) */
  	if (ac->ac_flags & EXT4_MB_HINT_NOPREALLOC)
  		return;
  
  	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC) {
  		ext4_mb_normalize_group_request(ac);
  		return ;
  	}
  
  	bsbits = ac->ac_sb->s_blocksize_bits;
  
  	/* first, let's learn actual file size
  	 * given current request is allocated */
  	size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
  	size = size << bsbits;
  	if (size < i_size_read(ac->ac_inode))
  		size = i_size_read(ac->ac_inode);
  	orig_size = size;
  
  	/* max size of free chunks */
  	max = 2 << bsbits;
  
  #define NRL_CHECK_SIZE(req, size, max, chunk_size)	\
  		(req <= (size) || max <= (chunk_size))
  
  	/* first, try to predict filesize */
  	/* XXX: should this table be tunable? */
  	start_off = 0;
  	if (size <= 16 * 1024) {
  		size = 16 * 1024;
  	} else if (size <= 32 * 1024) {
  		size = 32 * 1024;
  	} else if (size <= 64 * 1024) {
  		size = 64 * 1024;
  	} else if (size <= 128 * 1024) {
  		size = 128 * 1024;
  	} else if (size <= 256 * 1024) {
  		size = 256 * 1024;
  	} else if (size <= 512 * 1024) {
  		size = 512 * 1024;
  	} else if (size <= 1024 * 1024) {
  		size = 1024 * 1024;
  	} else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, 2 * 1024)) {
  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
  						(21 - bsbits)) << 21;
  		size = 2 * 1024 * 1024;
  	} else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, 4 * 1024)) {
  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
  							(22 - bsbits)) << 22;
  		size = 4 * 1024 * 1024;
  	} else if (NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,
  					(8<<20)>>bsbits, max, 8 * 1024)) {
  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
  							(23 - bsbits)) << 23;
  		size = 8 * 1024 * 1024;
  	} else {
  		start_off = (loff_t) ac->ac_o_ex.fe_logical << bsbits;
  		size	  = (loff_t) EXT4_C2B(EXT4_SB(ac->ac_sb),
  					      ac->ac_o_ex.fe_len) << bsbits;
  	}
  	size = size >> bsbits;
  	start = start_off >> bsbits;
  
  	/* don't cover already allocated blocks in selected range */
  	if (ar->pleft && start <= ar->lleft) {
  		size -= ar->lleft + 1 - start;
  		start = ar->lleft + 1;
  	}
  	if (ar->pright && start + size - 1 >= ar->lright)
  		size -= start + size - ar->lright;
  
  	end = start + size;
  
  	/* check we don't cross already preallocated blocks */
  	rcu_read_lock();
  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
  		ext4_lblk_t pa_end;
  
  		if (pa->pa_deleted)
  			continue;
  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted) {
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  
  		pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
  						  pa->pa_len);
  
  		/* PA must not overlap original request */
  		BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
  			ac->ac_o_ex.fe_logical < pa->pa_lstart));
  
  		/* skip PAs this normalized request doesn't overlap with */
  		if (pa->pa_lstart >= end || pa_end <= start) {
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  		BUG_ON(pa->pa_lstart <= start && pa_end >= end);
  
  		/* adjust start or end to be adjacent to this pa */
  		if (pa_end <= ac->ac_o_ex.fe_logical) {
  			BUG_ON(pa_end < start);
  			start = pa_end;
  		} else if (pa->pa_lstart > ac->ac_o_ex.fe_logical) {
  			BUG_ON(pa->pa_lstart > end);
  			end = pa->pa_lstart;
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  	size = end - start;
  
  	/* XXX: extra loop to check we really don't overlap preallocations */
  	rcu_read_lock();
  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
  		ext4_lblk_t pa_end;
  
  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted == 0) {
  			pa_end = pa->pa_lstart + EXT4_C2B(EXT4_SB(ac->ac_sb),
  							  pa->pa_len);
  			BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  
  	if (start + size <= ac->ac_o_ex.fe_logical &&
  			start > ac->ac_o_ex.fe_logical) {
  		ext4_msg(ac->ac_sb, KERN_ERR,
  			 "start %lu, size %lu, fe_logical %lu",
  			 (unsigned long) start, (unsigned long) size,
  			 (unsigned long) ac->ac_o_ex.fe_logical);
  		BUG();
  	}
  	BUG_ON(size <= 0 || size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
  
  	/* now prepare goal request */
  
  	/* XXX: is it better to align blocks WRT to logical
  	 * placement or satisfy big request as is */
  	ac->ac_g_ex.fe_logical = start;
  	ac->ac_g_ex.fe_len = EXT4_NUM_B2C(sbi, size);
  
  	/* define goal start in order to merge */
  	if (ar->pright && (ar->lright == (start + size))) {
  		/* merge to the right */
  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pright - size,
  						&ac->ac_f_ex.fe_group,
  						&ac->ac_f_ex.fe_start);
  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
  	}
  	if (ar->pleft && (ar->lleft + 1 == start)) {
  		/* merge to the left */
  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pleft + 1,
  						&ac->ac_f_ex.fe_group,
  						&ac->ac_f_ex.fe_start);
  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
  	}
  
  	mb_debug(1, "goal: %u(was %u) blocks at %u\n", (unsigned) size,
  		(unsigned) orig_size, (unsigned) start);
  }
  
  static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  
  	if (sbi->s_mb_stats && ac->ac_g_ex.fe_len > 1) {
  		atomic_inc(&sbi->s_bal_reqs);
  		atomic_add(ac->ac_b_ex.fe_len, &sbi->s_bal_allocated);
  		if (ac->ac_b_ex.fe_len >= ac->ac_o_ex.fe_len)
  			atomic_inc(&sbi->s_bal_success);
  		atomic_add(ac->ac_found, &sbi->s_bal_ex_scanned);
  		if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&
  				ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)
  			atomic_inc(&sbi->s_bal_goals);
  		if (ac->ac_found > sbi->s_mb_max_to_scan)
  			atomic_inc(&sbi->s_bal_breaks);
  	}
  
  	if (ac->ac_op == EXT4_MB_HISTORY_ALLOC)
  		trace_ext4_mballoc_alloc(ac);
  	else
  		trace_ext4_mballoc_prealloc(ac);
  }
  
  /*
   * Called on failure; free up any blocks from the inode PA for this
   * context.  We don't need this for MB_GROUP_PA because we only change
   * pa_free in ext4_mb_release_context(), but on failure, we've already
   * zeroed out ac->ac_b_ex.fe_len, so group_pa->pa_free is not changed.
   */
  static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac)
  {
  	struct ext4_prealloc_space *pa = ac->ac_pa;
  	struct ext4_buddy e4b;
  	int err;
  
  	if (pa == NULL) {
  		if (ac->ac_f_ex.fe_len == 0)
  			return;
  		err = ext4_mb_load_buddy(ac->ac_sb, ac->ac_f_ex.fe_group, &e4b);
  		if (err) {
  			/*
  			 * This should never happen since we pin the
  			 * pages in the ext4_allocation_context so
  			 * ext4_mb_load_buddy() should never fail.
  			 */
  			WARN(1, "mb_load_buddy failed (%d)", err);
  			return;
  		}
  		ext4_lock_group(ac->ac_sb, ac->ac_f_ex.fe_group);
  		mb_free_blocks(ac->ac_inode, &e4b, ac->ac_f_ex.fe_start,
  			       ac->ac_f_ex.fe_len);
  		ext4_unlock_group(ac->ac_sb, ac->ac_f_ex.fe_group);
  		ext4_mb_unload_buddy(&e4b);
  		return;
  	}
  	if (pa->pa_type == MB_INODE_PA)
  		pa->pa_free += ac->ac_b_ex.fe_len;
  }
  
  /*
   * use blocks preallocated to inode
   */
  static void ext4_mb_use_inode_pa(struct ext4_allocation_context *ac,
  				struct ext4_prealloc_space *pa)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	ext4_fsblk_t start;
  	ext4_fsblk_t end;
  	int len;
  
  	/* found preallocated blocks, use them */
  	start = pa->pa_pstart + (ac->ac_o_ex.fe_logical - pa->pa_lstart);
  	end = min(pa->pa_pstart + EXT4_C2B(sbi, pa->pa_len),
  		  start + EXT4_C2B(sbi, ac->ac_o_ex.fe_len));
  	len = EXT4_NUM_B2C(sbi, end - start);
  	ext4_get_group_no_and_offset(ac->ac_sb, start, &ac->ac_b_ex.fe_group,
  					&ac->ac_b_ex.fe_start);
  	ac->ac_b_ex.fe_len = len;
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_pa = pa;
  
  	BUG_ON(start < pa->pa_pstart);
  	BUG_ON(end > pa->pa_pstart + EXT4_C2B(sbi, pa->pa_len));
  	BUG_ON(pa->pa_free < len);
  	pa->pa_free -= len;
  
  	mb_debug(1, "use %llu/%u from inode pa %p\n", start, len, pa);
  }
  
  /*
   * use blocks preallocated to locality group
   */
  static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
  				struct ext4_prealloc_space *pa)
  {
  	unsigned int len = ac->ac_o_ex.fe_len;
  
  	ext4_get_group_no_and_offset(ac->ac_sb, pa->pa_pstart,
  					&ac->ac_b_ex.fe_group,
  					&ac->ac_b_ex.fe_start);
  	ac->ac_b_ex.fe_len = len;
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_pa = pa;
  
  	/* we don't correct pa_pstart or pa_plen here to avoid
  	 * possible race when the group is being loaded concurrently
  	 * instead we correct pa later, after blocks are marked
  	 * in on-disk bitmap -- see ext4_mb_release_context()
  	 * Other CPUs are prevented from allocating from this pa by lg_mutex
  	 */
  	mb_debug(1, "use %u/%u from group pa %p\n", pa->pa_lstart-len, len, pa);
  }
  
  /*
   * Return the prealloc space that have minimal distance
   * from the goal block. @cpa is the prealloc
   * space that is having currently known minimal distance
   * from the goal block.
   */
  static struct ext4_prealloc_space *
  ext4_mb_check_group_pa(ext4_fsblk_t goal_block,
  			struct ext4_prealloc_space *pa,
  			struct ext4_prealloc_space *cpa)
  {
  	ext4_fsblk_t cur_distance, new_distance;
  
  	if (cpa == NULL) {
  		atomic_inc(&pa->pa_count);
  		return pa;
  	}
  	cur_distance = abs(goal_block - cpa->pa_pstart);
  	new_distance = abs(goal_block - pa->pa_pstart);
  
  	if (cur_distance <= new_distance)
  		return cpa;
  
  	/* drop the previous reference */
  	atomic_dec(&cpa->pa_count);
  	atomic_inc(&pa->pa_count);
  	return pa;
  }
  
  /*
   * search goal blocks in preallocated space
   */
  static noinline_for_stack int
  ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	int order, i;
  	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
  	struct ext4_locality_group *lg;
  	struct ext4_prealloc_space *pa, *cpa = NULL;
  	ext4_fsblk_t goal_block;
  
  	/* only data can be preallocated */
  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
  		return 0;
  
  	/* first, try per-file preallocation */
  	rcu_read_lock();
  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
  
  		/* all fields in this condition don't change,
  		 * so we can skip locking for them */
  		if (ac->ac_o_ex.fe_logical < pa->pa_lstart ||
  		    ac->ac_o_ex.fe_logical >= (pa->pa_lstart +
  					       EXT4_C2B(sbi, pa->pa_len)))
  			continue;
  
  		/* non-extent files can't have physical blocks past 2^32 */
  		if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)) &&
  		    (pa->pa_pstart + EXT4_C2B(sbi, pa->pa_len) >
  		     EXT4_MAX_BLOCK_FILE_PHYS))
  			continue;
  
  		/* found preallocated blocks, use them */
  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted == 0 && pa->pa_free) {
  			atomic_inc(&pa->pa_count);
  			ext4_mb_use_inode_pa(ac, pa);
  			spin_unlock(&pa->pa_lock);
  			ac->ac_criteria = 10;
  			rcu_read_unlock();
  			return 1;
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  
  	/* can we use group allocation? */
  	if (!(ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC))
  		return 0;
  
  	/* inode may have no locality group for some reason */
  	lg = ac->ac_lg;
  	if (lg == NULL)
  		return 0;
  	order  = fls(ac->ac_o_ex.fe_len) - 1;
  	if (order > PREALLOC_TB_SIZE - 1)
  		/* The max size of hash table is PREALLOC_TB_SIZE */
  		order = PREALLOC_TB_SIZE - 1;
  
  	goal_block = ext4_grp_offs_to_block(ac->ac_sb, &ac->ac_g_ex);
  	/*
  	 * search for the prealloc space that is having
  	 * minimal distance from the goal block.
  	 */
  	for (i = order; i < PREALLOC_TB_SIZE; i++) {
  		rcu_read_lock();
  		list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[i],
  					pa_inode_list) {
  			spin_lock(&pa->pa_lock);
  			if (pa->pa_deleted == 0 &&
  					pa->pa_free >= ac->ac_o_ex.fe_len) {
  
  				cpa = ext4_mb_check_group_pa(goal_block,
  								pa, cpa);
  			}
  			spin_unlock(&pa->pa_lock);
  		}
  		rcu_read_unlock();
  	}
  	if (cpa) {
  		ext4_mb_use_group_pa(ac, cpa);
  		ac->ac_criteria = 20;
  		return 1;
  	}
  	return 0;
  }
  
  /*
   * the function goes through all block freed in the group
   * but not yet committed and marks them used in in-core bitmap.
   * buddy must be generated from this bitmap
   * Need to be called with the ext4 group lock held
   */
  static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
  						ext4_group_t group)
  {
  	struct rb_node *n;
  	struct ext4_group_info *grp;
  	struct ext4_free_data *entry;
  
  	grp = ext4_get_group_info(sb, group);
  	n = rb_first(&(grp->bb_free_root));
  
  	while (n) {
  		entry = rb_entry(n, struct ext4_free_data, efd_node);
  		ext4_set_bits(bitmap, entry->efd_start_cluster, entry->efd_count);
  		n = rb_next(n);
  	}
  	return;
  }
  
  /*
   * the function goes through all preallocation in this group and marks them
   * used in in-core bitmap. buddy must be generated from this bitmap
   * Need to be called with ext4 group lock held
   */
  static noinline_for_stack
  void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
  					ext4_group_t group)
  {
  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
  	struct ext4_prealloc_space *pa;
  	struct list_head *cur;
  	ext4_group_t groupnr;
  	ext4_grpblk_t start;
  	int preallocated = 0;
  	int len;
  
  	/* all form of preallocation discards first load group,
  	 * so the only competing code is preallocation use.
  	 * we don't need any locking here
  	 * notice we do NOT ignore preallocations with pa_deleted
  	 * otherwise we could leave used blocks available for
  	 * allocation in buddy when concurrent ext4_mb_put_pa()
  	 * is dropping preallocation
  	 */
  	list_for_each(cur, &grp->bb_prealloc_list) {
  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		spin_lock(&pa->pa_lock);
  		ext4_get_group_no_and_offset(sb, pa->pa_pstart,
  					     &groupnr, &start);
  		len = pa->pa_len;
  		spin_unlock(&pa->pa_lock);
  		if (unlikely(len == 0))
  			continue;
  		BUG_ON(groupnr != group);
  		ext4_set_bits(bitmap, start, len);
  		preallocated += len;
  	}
  	mb_debug(1, "prellocated %u for group %u\n", preallocated, group);
  }
  
  static void ext4_mb_pa_callback(struct rcu_head *head)
  {
  	struct ext4_prealloc_space *pa;
  	pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu);
  
  	BUG_ON(atomic_read(&pa->pa_count));
  	BUG_ON(pa->pa_deleted == 0);
  	kmem_cache_free(ext4_pspace_cachep, pa);
  }
  
  /*
   * drops a reference to preallocated space descriptor
   * if this was the last reference and the space is consumed
   */
  static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
  			struct super_block *sb, struct ext4_prealloc_space *pa)
  {
  	ext4_group_t grp;
  	ext4_fsblk_t grp_blk;
  
  	/* in this short window concurrent discard can set pa_deleted */
  	spin_lock(&pa->pa_lock);
  	if (!atomic_dec_and_test(&pa->pa_count) || pa->pa_free != 0) {
  		spin_unlock(&pa->pa_lock);
  		return;
  	}
  
  	if (pa->pa_deleted == 1) {
  		spin_unlock(&pa->pa_lock);
  		return;
  	}
  
  	pa->pa_deleted = 1;
  	spin_unlock(&pa->pa_lock);
  
  	grp_blk = pa->pa_pstart;
  	/*
  	 * If doing group-based preallocation, pa_pstart may be in the
  	 * next group when pa is used up
  	 */
  	if (pa->pa_type == MB_GROUP_PA)
  		grp_blk--;
  
  	grp = ext4_get_group_number(sb, grp_blk);
  
  	/*
  	 * possible race:
  	 *
  	 *  P1 (buddy init)			P2 (regular allocation)
  	 *					find block B in PA
  	 *  copy on-disk bitmap to buddy
  	 *  					mark B in on-disk bitmap
  	 *					drop PA from group
  	 *  mark all PAs in buddy
  	 *
  	 * thus, P1 initializes buddy with B available. to prevent this
  	 * we make "copy" and "mark all PAs" atomic and serialize "drop PA"
  	 * against that pair
  	 */
  	ext4_lock_group(sb, grp);
  	list_del(&pa->pa_group_list);
  	ext4_unlock_group(sb, grp);
  
  	spin_lock(pa->pa_obj_lock);
  	list_del_rcu(&pa->pa_inode_list);
  	spin_unlock(pa->pa_obj_lock);
  
  	call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
  }
  
  /*
   * creates new preallocated space for given inode
   */
  static noinline_for_stack int
  ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_prealloc_space *pa;
  	struct ext4_group_info *grp;
  	struct ext4_inode_info *ei;
  
  	/* preallocate only when found space is larger then requested */
  	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
  
  	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
  	if (pa == NULL)
  		return -ENOMEM;
  
  	if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) {
  		int winl;
  		int wins;
  		int win;
  		int offs;
  
  		/* we can't allocate as much as normalizer wants.
  		 * so, found space must get proper lstart
  		 * to cover original request */
  		BUG_ON(ac->ac_g_ex.fe_logical > ac->ac_o_ex.fe_logical);
  		BUG_ON(ac->ac_g_ex.fe_len < ac->ac_o_ex.fe_len);
  
  		/* we're limited by original request in that
  		 * logical block must be covered any way
  		 * winl is window we can move our chunk within */
  		winl = ac->ac_o_ex.fe_logical - ac->ac_g_ex.fe_logical;
  
  		/* also, we should cover whole original request */
  		wins = EXT4_C2B(sbi, ac->ac_b_ex.fe_len - ac->ac_o_ex.fe_len);
  
  		/* the smallest one defines real window */
  		win = min(winl, wins);
  
  		offs = ac->ac_o_ex.fe_logical %
  			EXT4_C2B(sbi, ac->ac_b_ex.fe_len);
  		if (offs && offs < win)
  			win = offs;
  
  		ac->ac_b_ex.fe_logical = ac->ac_o_ex.fe_logical -
  			EXT4_NUM_B2C(sbi, win);
  		BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical);
  		BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len);
  	}
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	pa->pa_lstart = ac->ac_b_ex.fe_logical;
  	pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  	pa->pa_len = ac->ac_b_ex.fe_len;
  	pa->pa_free = pa->pa_len;
  	atomic_set(&pa->pa_count, 1);
  	spin_lock_init(&pa->pa_lock);
  	INIT_LIST_HEAD(&pa->pa_inode_list);
  	INIT_LIST_HEAD(&pa->pa_group_list);
  	pa->pa_deleted = 0;
  	pa->pa_type = MB_INODE_PA;
  
  	mb_debug(1, "new inode pa %p: %llu/%u for %u\n", pa,
  			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
  	trace_ext4_mb_new_inode_pa(ac, pa);
  
  	ext4_mb_use_inode_pa(ac, pa);
  	atomic_add(pa->pa_free, &sbi->s_mb_preallocated);
  
  	ei = EXT4_I(ac->ac_inode);
  	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
  
  	pa->pa_obj_lock = &ei->i_prealloc_lock;
  	pa->pa_inode = ac->ac_inode;
  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  
  	spin_lock(pa->pa_obj_lock);
  	list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
  	spin_unlock(pa->pa_obj_lock);
  
  	return 0;
  }
  
  /*
   * creates new preallocated space for locality group inodes belongs to
   */
  static noinline_for_stack int
  ext4_mb_new_group_pa(struct ext4_allocation_context *ac)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_locality_group *lg;
  	struct ext4_prealloc_space *pa;
  	struct ext4_group_info *grp;
  
  	/* preallocate only when found space is larger then requested */
  	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
  
  	BUG_ON(ext4_pspace_cachep == NULL);
  	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
  	if (pa == NULL)
  		return -ENOMEM;
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  	pa->pa_lstart = pa->pa_pstart;
  	pa->pa_len = ac->ac_b_ex.fe_len;
  	pa->pa_free = pa->pa_len;
  	atomic_set(&pa->pa_count, 1);
  	spin_lock_init(&pa->pa_lock);
  	INIT_LIST_HEAD(&pa->pa_inode_list);
  	INIT_LIST_HEAD(&pa->pa_group_list);
  	pa->pa_deleted = 0;
  	pa->pa_type = MB_GROUP_PA;
  
  	mb_debug(1, "new group pa %p: %llu/%u for %u\n", pa,
  			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
  	trace_ext4_mb_new_group_pa(ac, pa);
  
  	ext4_mb_use_group_pa(ac, pa);
  	atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);
  
  	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
  	lg = ac->ac_lg;
  	BUG_ON(lg == NULL);
  
  	pa->pa_obj_lock = &lg->lg_prealloc_lock;
  	pa->pa_inode = NULL;
  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  
  	/*
  	 * We will later add the new pa to the right bucket
  	 * after updating the pa_free in ext4_mb_release_context
  	 */
  	return 0;
  }
  
  static int ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
  {
  	int err;
  
  	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
  		err = ext4_mb_new_group_pa(ac);
  	else
  		err = ext4_mb_new_inode_pa(ac);
  	return err;
  }
  
  /*
   * finds all unused blocks in on-disk bitmap, frees them in
   * in-core bitmap and buddy.
   * @pa must be unlinked from inode and group lists, so that
   * nobody else can find/use it.
   * the caller MUST hold group/inode locks.
   * TODO: optimize the case when there are no in-core structures yet
   */
  static noinline_for_stack int
  ext4_mb_release_inode_pa(struct ext4_buddy *e4b, struct buffer_head *bitmap_bh,
  			struct ext4_prealloc_space *pa)
  {
  	struct super_block *sb = e4b->bd_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	unsigned int end;
  	unsigned int next;
  	ext4_group_t group;
  	ext4_grpblk_t bit;
  	unsigned long long grp_blk_start;
  	int err = 0;
  	int free = 0;
  
  	BUG_ON(pa->pa_deleted == 0);
  	ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
  	grp_blk_start = pa->pa_pstart - EXT4_C2B(sbi, bit);
  	BUG_ON(group != e4b->bd_group && pa->pa_len != 0);
  	end = bit + pa->pa_len;
  
  	while (bit < end) {
  		bit = mb_find_next_zero_bit(bitmap_bh->b_data, end, bit);
  		if (bit >= end)
  			break;
  		next = mb_find_next_bit(bitmap_bh->b_data, end, bit);
  		mb_debug(1, "    free preallocated %u/%u in group %u\n",
  			 (unsigned) ext4_group_first_block_no(sb, group) + bit,
  			 (unsigned) next - bit, (unsigned) group);
  		free += next - bit;
  
  		trace_ext4_mballoc_discard(sb, NULL, group, bit, next - bit);
  		trace_ext4_mb_release_inode_pa(pa, (grp_blk_start +
  						    EXT4_C2B(sbi, bit)),
  					       next - bit);
  		mb_free_blocks(pa->pa_inode, e4b, bit, next - bit);
  		bit = next + 1;
  	}
  	if (free != pa->pa_free) {
  		ext4_msg(e4b->bd_sb, KERN_CRIT,
  			 "pa %p: logic %lu, phys. %lu, len %lu",
  			 pa, (unsigned long) pa->pa_lstart,
  			 (unsigned long) pa->pa_pstart,
  			 (unsigned long) pa->pa_len);
  		ext4_grp_locked_error(sb, group, 0, 0, "free %u, pa_free %u",
  					free, pa->pa_free);
  		/*
  		 * pa is already deleted so we use the value obtained
  		 * from the bitmap and continue.
  		 */
  	}
  	atomic_add(free, &sbi->s_mb_discarded);
  
  	return err;
  }
  
  static noinline_for_stack int
  ext4_mb_release_group_pa(struct ext4_buddy *e4b,
  				struct ext4_prealloc_space *pa)
  {
  	struct super_block *sb = e4b->bd_sb;
  	ext4_group_t group;
  	ext4_grpblk_t bit;
  
  	trace_ext4_mb_release_group_pa(sb, pa);
  	BUG_ON(pa->pa_deleted == 0);
  	ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
  	BUG_ON(group != e4b->bd_group && pa->pa_len != 0);
  	mb_free_blocks(pa->pa_inode, e4b, bit, pa->pa_len);
  	atomic_add(pa->pa_len, &EXT4_SB(sb)->s_mb_discarded);
  	trace_ext4_mballoc_discard(sb, NULL, group, bit, pa->pa_len);
  
  	return 0;
  }
  
  /*
   * releases all preallocations in given group
   *
   * first, we need to decide discard policy:
   * - when do we discard
   *   1) ENOSPC
   * - how many do we discard
   *   1) how many requested
   */
  static noinline_for_stack int
  ext4_mb_discard_group_preallocations(struct super_block *sb,
  					ext4_group_t group, int needed)
  {
  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
  	struct buffer_head *bitmap_bh = NULL;
  	struct ext4_prealloc_space *pa, *tmp;
  	struct list_head list;
  	struct ext4_buddy e4b;
  	int err;
  	int busy = 0;
  	int free = 0;
  
  	mb_debug(1, "discard preallocation for group %u\n", group);
  
  	if (list_empty(&grp->bb_prealloc_list))
  		return 0;
  
  	bitmap_bh = ext4_read_block_bitmap(sb, group);
  	if (IS_ERR(bitmap_bh)) {
  		err = PTR_ERR(bitmap_bh);
  		ext4_error(sb, "Error %d reading block bitmap for %u",
  			   err, group);
  		return 0;
  	}
  
  	err = ext4_mb_load_buddy(sb, group, &e4b);
  	if (err) {
  		ext4_error(sb, "Error loading buddy information for %u", group);
  		put_bh(bitmap_bh);
  		return 0;
  	}
  
  	if (needed == 0)
  		needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
  
  	INIT_LIST_HEAD(&list);
  repeat:
  	ext4_lock_group(sb, group);
  	list_for_each_entry_safe(pa, tmp,
  				&grp->bb_prealloc_list, pa_group_list) {
  		spin_lock(&pa->pa_lock);
  		if (atomic_read(&pa->pa_count)) {
  			spin_unlock(&pa->pa_lock);
  			busy = 1;
  			continue;
  		}
  		if (pa->pa_deleted) {
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  
  		/* seems this one can be freed ... */
  		pa->pa_deleted = 1;
  
  		/* we can trust pa_free ... */
  		free += pa->pa_free;
  
  		spin_unlock(&pa->pa_lock);
  
  		list_del(&pa->pa_group_list);
  		list_add(&pa->u.pa_tmp_list, &list);
  	}
  
  	/* if we still need more blocks and some PAs were used, try again */
  	if (free < needed && busy) {
  		busy = 0;
  		ext4_unlock_group(sb, group);
  		cond_resched();
  		goto repeat;
  	}
  
  	/* found anything to free? */
  	if (list_empty(&list)) {
  		BUG_ON(free != 0);
  		goto out;
  	}
  
  	/* now free all selected PAs */
  	list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
  
  		/* remove from object (inode or locality group) */
  		spin_lock(pa->pa_obj_lock);
  		list_del_rcu(&pa->pa_inode_list);
  		spin_unlock(pa->pa_obj_lock);
  
  		if (pa->pa_type == MB_GROUP_PA)
  			ext4_mb_release_group_pa(&e4b, pa);
  		else
  			ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa);
  
  		list_del(&pa->u.pa_tmp_list);
  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
  	}
  
  out:
  	ext4_unlock_group(sb, group);
  	ext4_mb_unload_buddy(&e4b);
  	put_bh(bitmap_bh);
  	return free;
  }
  
  /*
   * releases all non-used preallocated blocks for given inode
   *
   * It's important to discard preallocations under i_data_sem
   * We don't want another block to be served from the prealloc
   * space when we are discarding the inode prealloc space.
   *
   * FIXME!! Make sure it is valid at all the call sites
   */
  void ext4_discard_preallocations(struct inode *inode)
  {
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	struct super_block *sb = inode->i_sb;
  	struct buffer_head *bitmap_bh = NULL;
  	struct ext4_prealloc_space *pa, *tmp;
  	ext4_group_t group = 0;
  	struct list_head list;
  	struct ext4_buddy e4b;
  	int err;
  
  	if (!S_ISREG(inode->i_mode)) {
  		/*BUG_ON(!list_empty(&ei->i_prealloc_list));*/
  		return;
  	}
  
  	mb_debug(1, "discard preallocation for inode %lu\n", inode->i_ino);
  	trace_ext4_discard_preallocations(inode);
  
  	INIT_LIST_HEAD(&list);
  
  repeat:
  	/* first, collect all pa's in the inode */
  	spin_lock(&ei->i_prealloc_lock);
  	while (!list_empty(&ei->i_prealloc_list)) {
  		pa = list_entry(ei->i_prealloc_list.next,
  				struct ext4_prealloc_space, pa_inode_list);
  		BUG_ON(pa->pa_obj_lock != &ei->i_prealloc_lock);
  		spin_lock(&pa->pa_lock);
  		if (atomic_read(&pa->pa_count)) {
  			/* this shouldn't happen often - nobody should
  			 * use preallocation while we're discarding it */
  			spin_unlock(&pa->pa_lock);
  			spin_unlock(&ei->i_prealloc_lock);
  			ext4_msg(sb, KERN_ERR,
  				 "uh-oh! used pa while discarding");
  			WARN_ON(1);
  			schedule_timeout_uninterruptible(HZ);
  			goto repeat;
  
  		}
  		if (pa->pa_deleted == 0) {
  			pa->pa_deleted = 1;
  			spin_unlock(&pa->pa_lock);
  			list_del_rcu(&pa->pa_inode_list);
  			list_add(&pa->u.pa_tmp_list, &list);
  			continue;
  		}
  
  		/* someone is deleting pa right now */
  		spin_unlock(&pa->pa_lock);
  		spin_unlock(&ei->i_prealloc_lock);
  
  		/* we have to wait here because pa_deleted
  		 * doesn't mean pa is already unlinked from
  		 * the list. as we might be called from
  		 * ->clear_inode() the inode will get freed
  		 * and concurrent thread which is unlinking
  		 * pa from inode's list may access already
  		 * freed memory, bad-bad-bad */
  
  		/* XXX: if this happens too often, we can
  		 * add a flag to force wait only in case
  		 * of ->clear_inode(), but not in case of
  		 * regular truncate */
  		schedule_timeout_uninterruptible(HZ);
  		goto repeat;
  	}
  	spin_unlock(&ei->i_prealloc_lock);
  
  	list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
  		BUG_ON(pa->pa_type != MB_INODE_PA);
  		group = ext4_get_group_number(sb, pa->pa_pstart);
  
  		err = ext4_mb_load_buddy(sb, group, &e4b);
  		if (err) {
  			ext4_error(sb, "Error loading buddy information for %u",
  					group);
  			continue;
  		}
  
  		bitmap_bh = ext4_read_block_bitmap(sb, group);
  		if (IS_ERR(bitmap_bh)) {
  			err = PTR_ERR(bitmap_bh);
  			ext4_error(sb, "Error %d reading block bitmap for %u",
  					err, group);
  			ext4_mb_unload_buddy(&e4b);
  			continue;
  		}
  
  		ext4_lock_group(sb, group);
  		list_del(&pa->pa_group_list);
  		ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa);
  		ext4_unlock_group(sb, group);
  
  		ext4_mb_unload_buddy(&e4b);
  		put_bh(bitmap_bh);
  
  		list_del(&pa->u.pa_tmp_list);
  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
  	}
  }
  
  #ifdef CONFIG_EXT4_DEBUG
  static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
  {
  	struct super_block *sb = ac->ac_sb;
  	ext4_group_t ngroups, i;
  
  	if (!ext4_mballoc_debug ||
  	    (EXT4_SB(sb)->s_mount_flags & EXT4_MF_FS_ABORTED))
  		return;
  
  	ext4_msg(ac->ac_sb, KERN_ERR, "Can't allocate:"
  			" Allocation context details:");
  	ext4_msg(ac->ac_sb, KERN_ERR, "status %d flags %d",
  			ac->ac_status, ac->ac_flags);
  	ext4_msg(ac->ac_sb, KERN_ERR, "orig %lu/%lu/%lu@%lu, "
  		 	"goal %lu/%lu/%lu@%lu, "
  			"best %lu/%lu/%lu@%lu cr %d",
  			(unsigned long)ac->ac_o_ex.fe_group,
  			(unsigned long)ac->ac_o_ex.fe_start,
  			(unsigned long)ac->ac_o_ex.fe_len,
  			(unsigned long)ac->ac_o_ex.fe_logical,
  			(unsigned long)ac->ac_g_ex.fe_group,
  			(unsigned long)ac->ac_g_ex.fe_start,
  			(unsigned long)ac->ac_g_ex.fe_len,
  			(unsigned long)ac->ac_g_ex.fe_logical,
  			(unsigned long)ac->ac_b_ex.fe_group,
  			(unsigned long)ac->ac_b_ex.fe_start,
  			(unsigned long)ac->ac_b_ex.fe_len,
  			(unsigned long)ac->ac_b_ex.fe_logical,
  			(int)ac->ac_criteria);
  	ext4_msg(ac->ac_sb, KERN_ERR, "%d found", ac->ac_found);
  	ext4_msg(ac->ac_sb, KERN_ERR, "groups: ");
  	ngroups = ext4_get_groups_count(sb);
  	for (i = 0; i < ngroups; i++) {
  		struct ext4_group_info *grp = ext4_get_group_info(sb, i);
  		struct ext4_prealloc_space *pa;
  		ext4_grpblk_t start;
  		struct list_head *cur;
  		ext4_lock_group(sb, i);
  		list_for_each(cur, &grp->bb_prealloc_list) {
  			pa = list_entry(cur, struct ext4_prealloc_space,
  					pa_group_list);
  			spin_lock(&pa->pa_lock);
  			ext4_get_group_no_and_offset(sb, pa->pa_pstart,
  						     NULL, &start);
  			spin_unlock(&pa->pa_lock);
  			printk(KERN_ERR "PA:%u:%d:%u \n", i,
  			       start, pa->pa_len);
  		}
  		ext4_unlock_group(sb, i);
  
  		if (grp->bb_free == 0)
  			continue;
  		printk(KERN_ERR "%u: %d/%d \n",
  		       i, grp->bb_free, grp->bb_fragments);
  	}
  	printk(KERN_ERR "\n");
  }
  #else
  static inline void ext4_mb_show_ac(struct ext4_allocation_context *ac)
  {
  	return;
  }
  #endif
  
  /*
   * We use locality group preallocation for small size file. The size of the
   * file is determined by the current size or the resulting size after
   * allocation which ever is larger
   *
   * One can tune this size via /sys/fs/ext4/<partition>/mb_stream_req
   */
  static void ext4_mb_group_or_file(struct ext4_allocation_context *ac)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	int bsbits = ac->ac_sb->s_blocksize_bits;
  	loff_t size, isize;
  
  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
  		return;
  
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
  		return;
  
  	size = ac->ac_o_ex.fe_logical + EXT4_C2B(sbi, ac->ac_o_ex.fe_len);
  	isize = (i_size_read(ac->ac_inode) + ac->ac_sb->s_blocksize - 1)
  		>> bsbits;
  
  	if ((size == isize) &&
  	    !ext4_fs_is_busy(sbi) &&
  	    (atomic_read(&ac->ac_inode->i_writecount) == 0)) {
  		ac->ac_flags |= EXT4_MB_HINT_NOPREALLOC;
  		return;
  	}
  
  	if (sbi->s_mb_group_prealloc <= 0) {
  		ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
  		return;
  	}
  
  	/* don't use group allocation for large files */
  	size = max(size, isize);
  	if (size > sbi->s_mb_stream_request) {
  		ac->ac_flags |= EXT4_MB_STREAM_ALLOC;
  		return;
  	}
  
  	BUG_ON(ac->ac_lg != NULL);
  	/*
  	 * locality group prealloc space are per cpu. The reason for having
  	 * per cpu locality group is to reduce the contention between block
  	 * request from multiple CPUs.
  	 */
  	ac->ac_lg = raw_cpu_ptr(sbi->s_locality_groups);
  
  	/* we're going to use group allocation */
  	ac->ac_flags |= EXT4_MB_HINT_GROUP_ALLOC;
  
  	/* serialize all allocations in the group */
  	mutex_lock(&ac->ac_lg->lg_mutex);
  }
  
  static noinline_for_stack int
  ext4_mb_initialize_context(struct ext4_allocation_context *ac,
  				struct ext4_allocation_request *ar)
  {
  	struct super_block *sb = ar->inode->i_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_super_block *es = sbi->s_es;
  	ext4_group_t group;
  	unsigned int len;
  	ext4_fsblk_t goal;
  	ext4_grpblk_t block;
  
  	/* we can't allocate > group size */
  	len = ar->len;
  
  	/* just a dirty hack to filter too big requests  */
  	if (len >= EXT4_CLUSTERS_PER_GROUP(sb))
  		len = EXT4_CLUSTERS_PER_GROUP(sb);
  
  	/* start searching from the goal */
  	goal = ar->goal;
  	if (goal < le32_to_cpu(es->s_first_data_block) ||
  			goal >= ext4_blocks_count(es))
  		goal = le32_to_cpu(es->s_first_data_block);
  	ext4_get_group_no_and_offset(sb, goal, &group, &block);
  
  	/* set up allocation goals */
  	ac->ac_b_ex.fe_logical = EXT4_LBLK_CMASK(sbi, ar->logical);
  	ac->ac_status = AC_STATUS_CONTINUE;
  	ac->ac_sb = sb;
  	ac->ac_inode = ar->inode;
  	ac->ac_o_ex.fe_logical = ac->ac_b_ex.fe_logical;
  	ac->ac_o_ex.fe_group = group;
  	ac->ac_o_ex.fe_start = block;
  	ac->ac_o_ex.fe_len = len;
  	ac->ac_g_ex = ac->ac_o_ex;
  	ac->ac_flags = ar->flags;
  
  	/* we have to define context: we'll we work with a file or
  	 * locality group. this is a policy, actually */
  	ext4_mb_group_or_file(ac);
  
  	mb_debug(1, "init ac: %u blocks @ %u, goal %u, flags %x, 2^%d, "
  			"left: %u/%u, right %u/%u to %swritable\n",
  			(unsigned) ar->len, (unsigned) ar->logical,
  			(unsigned) ar->goal, ac->ac_flags, ac->ac_2order,
  			(unsigned) ar->lleft, (unsigned) ar->pleft,
  			(unsigned) ar->lright, (unsigned) ar->pright,
  			atomic_read(&ar->inode->i_writecount) ? "" : "non-");
  	return 0;
  
  }
  
  static noinline_for_stack void
  ext4_mb_discard_lg_preallocations(struct super_block *sb,
  					struct ext4_locality_group *lg,
  					int order, int total_entries)
  {
  	ext4_group_t group = 0;
  	struct ext4_buddy e4b;
  	struct list_head discard_list;
  	struct ext4_prealloc_space *pa, *tmp;
  
  	mb_debug(1, "discard locality group preallocation\n");
  
  	INIT_LIST_HEAD(&discard_list);
  
  	spin_lock(&lg->lg_prealloc_lock);
  	list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[order],
  						pa_inode_list) {
  		spin_lock(&pa->pa_lock);
  		if (atomic_read(&pa->pa_count)) {
  			/*
  			 * This is the pa that we just used
  			 * for block allocation. So don't
  			 * free that
  			 */
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  		if (pa->pa_deleted) {
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  		/* only lg prealloc space */
  		BUG_ON(pa->pa_type != MB_GROUP_PA);
  
  		/* seems this one can be freed ... */
  		pa->pa_deleted = 1;
  		spin_unlock(&pa->pa_lock);
  
  		list_del_rcu(&pa->pa_inode_list);
  		list_add(&pa->u.pa_tmp_list, &discard_list);
  
  		total_entries--;
  		if (total_entries <= 5) {
  			/*
  			 * we want to keep only 5 entries
  			 * allowing it to grow to 8. This
  			 * mak sure we don't call discard
  			 * soon for this list.
  			 */
  			break;
  		}
  	}
  	spin_unlock(&lg->lg_prealloc_lock);
  
  	list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
  
  		group = ext4_get_group_number(sb, pa->pa_pstart);
  		if (ext4_mb_load_buddy(sb, group, &e4b)) {
  			ext4_error(sb, "Error loading buddy information for %u",
  					group);
  			continue;
  		}
  		ext4_lock_group(sb, group);
  		list_del(&pa->pa_group_list);
  		ext4_mb_release_group_pa(&e4b, pa);
  		ext4_unlock_group(sb, group);
  
  		ext4_mb_unload_buddy(&e4b);
  		list_del(&pa->u.pa_tmp_list);
  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
  	}
  }
  
  /*
   * We have incremented pa_count. So it cannot be freed at this
   * point. Also we hold lg_mutex. So no parallel allocation is
   * possible from this lg. That means pa_free cannot be updated.
   *
   * A parallel ext4_mb_discard_group_preallocations is possible.
   * which can cause the lg_prealloc_list to be updated.
   */
  
  static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
  {
  	int order, added = 0, lg_prealloc_count = 1;
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_locality_group *lg = ac->ac_lg;
  	struct ext4_prealloc_space *tmp_pa, *pa = ac->ac_pa;
  
  	order = fls(pa->pa_free) - 1;
  	if (order > PREALLOC_TB_SIZE - 1)
  		/* The max size of hash table is PREALLOC_TB_SIZE */
  		order = PREALLOC_TB_SIZE - 1;
  	/* Add the prealloc space to lg */
  	spin_lock(&lg->lg_prealloc_lock);
  	list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[order],
  						pa_inode_list) {
  		spin_lock(&tmp_pa->pa_lock);
  		if (tmp_pa->pa_deleted) {
  			spin_unlock(&tmp_pa->pa_lock);
  			continue;
  		}
  		if (!added && pa->pa_free < tmp_pa->pa_free) {
  			/* Add to the tail of the previous entry */
  			list_add_tail_rcu(&pa->pa_inode_list,
  						&tmp_pa->pa_inode_list);
  			added = 1;
  			/*
  			 * we want to count the total
  			 * number of entries in the list
  			 */
  		}
  		spin_unlock(&tmp_pa->pa_lock);
  		lg_prealloc_count++;
  	}
  	if (!added)
  		list_add_tail_rcu(&pa->pa_inode_list,
  					&lg->lg_prealloc_list[order]);
  	spin_unlock(&lg->lg_prealloc_lock);
  
  	/* Now trim the list to be not more than 8 elements */
  	if (lg_prealloc_count > 8) {
  		ext4_mb_discard_lg_preallocations(sb, lg,
  						  order, lg_prealloc_count);
  		return;
  	}
  	return ;
  }
  
  /*
   * release all resource we used in allocation
   */
  static int ext4_mb_release_context(struct ext4_allocation_context *ac)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	struct ext4_prealloc_space *pa = ac->ac_pa;
  	if (pa) {
  		if (pa->pa_type == MB_GROUP_PA) {
  			/* see comment in ext4_mb_use_group_pa() */
  			spin_lock(&pa->pa_lock);
  			pa->pa_pstart += EXT4_C2B(sbi, ac->ac_b_ex.fe_len);
  			pa->pa_lstart += EXT4_C2B(sbi, ac->ac_b_ex.fe_len);
  			pa->pa_free -= ac->ac_b_ex.fe_len;
  			pa->pa_len -= ac->ac_b_ex.fe_len;
  			spin_unlock(&pa->pa_lock);
  		}
  	}
  	if (pa) {
  		/*
  		 * We want to add the pa to the right bucket.
  		 * Remove it from the list and while adding
  		 * make sure the list to which we are adding
  		 * doesn't grow big.
  		 */
  		if ((pa->pa_type == MB_GROUP_PA) && likely(pa->pa_free)) {
  			spin_lock(pa->pa_obj_lock);
  			list_del_rcu(&pa->pa_inode_list);
  			spin_unlock(pa->pa_obj_lock);
  			ext4_mb_add_n_trim(ac);
  		}
  		ext4_mb_put_pa(ac, ac->ac_sb, pa);
  	}
  	if (ac->ac_bitmap_page)
  		page_cache_release(ac->ac_bitmap_page);
  	if (ac->ac_buddy_page)
  		page_cache_release(ac->ac_buddy_page);
  	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
  		mutex_unlock(&ac->ac_lg->lg_mutex);
  	ext4_mb_collect_stats(ac);
  	return 0;
  }
  
  static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
  {
  	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
  	int ret;
  	int freed = 0;
  
  	trace_ext4_mb_discard_preallocations(sb, needed);
  	for (i = 0; i < ngroups && needed > 0; i++) {
  		ret = ext4_mb_discard_group_preallocations(sb, i, needed);
  		freed += ret;
  		needed -= ret;
  	}
  
  	return freed;
  }
  
  /*
   * Main entry point into mballoc to allocate blocks
   * it tries to use preallocation first, then falls back
   * to usual allocation
   */
  ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
  				struct ext4_allocation_request *ar, int *errp)
  {
  	int freed;
  	struct ext4_allocation_context *ac = NULL;
  	struct ext4_sb_info *sbi;
  	struct super_block *sb;
  	ext4_fsblk_t block = 0;
  	unsigned int inquota = 0;
  	unsigned int reserv_clstrs = 0;
  
  	might_sleep();
  	sb = ar->inode->i_sb;
  	sbi = EXT4_SB(sb);
  
  	trace_ext4_request_blocks(ar);
  
  	/* Allow to use superuser reservation for quota file */
  	if (IS_NOQUOTA(ar->inode))
  		ar->flags |= EXT4_MB_USE_ROOT_BLOCKS;
  
  	if ((ar->flags & EXT4_MB_DELALLOC_RESERVED) == 0) {
  		/* Without delayed allocation we need to verify
  		 * there is enough free blocks to do block allocation
  		 * and verify allocation doesn't exceed the quota limits.
  		 */
  		while (ar->len &&
  			ext4_claim_free_clusters(sbi, ar->len, ar->flags)) {
  
  			/* let others to free the space */
  			cond_resched();
  			ar->len = ar->len >> 1;
  		}
  		if (!ar->len) {
  			*errp = -ENOSPC;
  			return 0;
  		}
  		reserv_clstrs = ar->len;
  		if (ar->flags & EXT4_MB_USE_ROOT_BLOCKS) {
  			dquot_alloc_block_nofail(ar->inode,
  						 EXT4_C2B(sbi, ar->len));
  		} else {
  			while (ar->len &&
  				dquot_alloc_block(ar->inode,
  						  EXT4_C2B(sbi, ar->len))) {
  
  				ar->flags |= EXT4_MB_HINT_NOPREALLOC;
  				ar->len--;
  			}
  		}
  		inquota = ar->len;
  		if (ar->len == 0) {
  			*errp = -EDQUOT;
  			goto out;
  		}
  	}
  
  	ac = kmem_cache_zalloc(ext4_ac_cachep, GFP_NOFS);
  	if (!ac) {
  		ar->len = 0;
  		*errp = -ENOMEM;
  		goto out;
  	}
  
  	*errp = ext4_mb_initialize_context(ac, ar);
  	if (*errp) {
  		ar->len = 0;
  		goto out;
  	}
  
  	ac->ac_op = EXT4_MB_HISTORY_PREALLOC;
  	if (!ext4_mb_use_preallocated(ac)) {
  		ac->ac_op = EXT4_MB_HISTORY_ALLOC;
  		ext4_mb_normalize_request(ac, ar);
  repeat:
  		/* allocate space in core */
  		*errp = ext4_mb_regular_allocator(ac);
  		if (*errp)
  			goto discard_and_exit;
  
  		/* as we've just preallocated more space than
  		 * user requested originally, we store allocated
  		 * space in a special descriptor */
  		if (ac->ac_status == AC_STATUS_FOUND &&
  		    ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len)
  			*errp = ext4_mb_new_preallocation(ac);
  		if (*errp) {
  		discard_and_exit:
  			ext4_discard_allocated_blocks(ac);
  			goto errout;
  		}
  	}
  	if (likely(ac->ac_status == AC_STATUS_FOUND)) {
  		*errp = ext4_mb_mark_diskspace_used(ac, handle, reserv_clstrs);
  		if (*errp) {
  			ext4_discard_allocated_blocks(ac);
  			goto errout;
  		} else {
  			block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  			ar->len = ac->ac_b_ex.fe_len;
  		}
  	} else {
  		freed  = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
  		if (freed)
  			goto repeat;
  		*errp = -ENOSPC;
  	}
  
  errout:
  	if (*errp) {
  		ac->ac_b_ex.fe_len = 0;
  		ar->len = 0;
  		ext4_mb_show_ac(ac);
  	}
  	ext4_mb_release_context(ac);
  out:
  	if (ac)
  		kmem_cache_free(ext4_ac_cachep, ac);
  	if (inquota && ar->len < inquota)
  		dquot_free_block(ar->inode, EXT4_C2B(sbi, inquota - ar->len));
  	if (!ar->len) {
  		if ((ar->flags & EXT4_MB_DELALLOC_RESERVED) == 0)
  			/* release all the reserved blocks if non delalloc */
  			percpu_counter_sub(&sbi->s_dirtyclusters_counter,
  						reserv_clstrs);
  	}
  
  	trace_ext4_allocate_blocks(ar, (unsigned long long)block);
  
  	return block;
  }
  
  /*
   * We can merge two free data extents only if the physical blocks
   * are contiguous, AND the extents were freed by the same transaction,
   * AND the blocks are associated with the same group.
   */
  static int can_merge(struct ext4_free_data *entry1,
  			struct ext4_free_data *entry2)
  {
  	if ((entry1->efd_tid == entry2->efd_tid) &&
  	    (entry1->efd_group == entry2->efd_group) &&
  	    ((entry1->efd_start_cluster + entry1->efd_count) == entry2->efd_start_cluster))
  		return 1;
  	return 0;
  }
  
  static noinline_for_stack int
  ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
  		      struct ext4_free_data *new_entry)
  {
  	ext4_group_t group = e4b->bd_group;
  	ext4_grpblk_t cluster;
  	struct ext4_free_data *entry;
  	struct ext4_group_info *db = e4b->bd_info;
  	struct super_block *sb = e4b->bd_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct rb_node **n = &db->bb_free_root.rb_node, *node;
  	struct rb_node *parent = NULL, *new_node;
  
  	BUG_ON(!ext4_handle_valid(handle));
  	BUG_ON(e4b->bd_bitmap_page == NULL);
  	BUG_ON(e4b->bd_buddy_page == NULL);
  
  	new_node = &new_entry->efd_node;
  	cluster = new_entry->efd_start_cluster;
  
  	if (!*n) {
  		/* first free block exent. We need to
  		   protect buddy cache from being freed,
  		 * otherwise we'll refresh it from
  		 * on-disk bitmap and lose not-yet-available
  		 * blocks */
  		page_cache_get(e4b->bd_buddy_page);
  		page_cache_get(e4b->bd_bitmap_page);
  	}
  	while (*n) {
  		parent = *n;
  		entry = rb_entry(parent, struct ext4_free_data, efd_node);
  		if (cluster < entry->efd_start_cluster)
  			n = &(*n)->rb_left;
  		else if (cluster >= (entry->efd_start_cluster + entry->efd_count))
  			n = &(*n)->rb_right;
  		else {
  			ext4_grp_locked_error(sb, group, 0,
  				ext4_group_first_block_no(sb, group) +
  				EXT4_C2B(sbi, cluster),
  				"Block already on to-be-freed list");
  			return 0;
  		}
  	}
  
  	rb_link_node(new_node, parent, n);
  	rb_insert_color(new_node, &db->bb_free_root);
  
  	/* Now try to see the extent can be merged to left and right */
  	node = rb_prev(new_node);
  	if (node) {
  		entry = rb_entry(node, struct ext4_free_data, efd_node);
  		if (can_merge(entry, new_entry) &&
  		    ext4_journal_callback_try_del(handle, &entry->efd_jce)) {
  			new_entry->efd_start_cluster = entry->efd_start_cluster;
  			new_entry->efd_count += entry->efd_count;
  			rb_erase(node, &(db->bb_free_root));
  			kmem_cache_free(ext4_free_data_cachep, entry);
  		}
  	}
  
  	node = rb_next(new_node);
  	if (node) {
  		entry = rb_entry(node, struct ext4_free_data, efd_node);
  		if (can_merge(new_entry, entry) &&
  		    ext4_journal_callback_try_del(handle, &entry->efd_jce)) {
  			new_entry->efd_count += entry->efd_count;
  			rb_erase(node, &(db->bb_free_root));
  			kmem_cache_free(ext4_free_data_cachep, entry);
  		}
  	}
  	/* Add the extent to transaction's private list */
  	ext4_journal_callback_add(handle, ext4_free_data_callback,
  				  &new_entry->efd_jce);
  	return 0;
  }
  
  /**
   * ext4_free_blocks() -- Free given blocks and update quota
   * @handle:		handle for this transaction
   * @inode:		inode
   * @block:		start physical block to free
   * @count:		number of blocks to count
   * @flags:		flags used by ext4_free_blocks
   */
  void ext4_free_blocks(handle_t *handle, struct inode *inode,
  		      struct buffer_head *bh, ext4_fsblk_t block,
  		      unsigned long count, int flags)
  {
  	struct buffer_head *bitmap_bh = NULL;
  	struct super_block *sb = inode->i_sb;
  	struct ext4_group_desc *gdp;
  	unsigned int overflow;
  	ext4_grpblk_t bit;
  	struct buffer_head *gd_bh;
  	ext4_group_t block_group;
  	struct ext4_sb_info *sbi;
  	struct ext4_buddy e4b;
  	unsigned int count_clusters;
  	int err = 0;
  	int ret;
  
  	might_sleep();
  	if (bh) {
  		if (block)
  			BUG_ON(block != bh->b_blocknr);
  		else
  			block = bh->b_blocknr;
  	}
  
  	sbi = EXT4_SB(sb);
  	if (!(flags & EXT4_FREE_BLOCKS_VALIDATED) &&
  	    !ext4_data_block_valid(sbi, block, count)) {
  		ext4_error(sb, "Freeing blocks not in datazone - "
  			   "block = %llu, count = %lu", block, count);
  		goto error_return;
  	}
  
  	ext4_debug("freeing block %llu\n", block);
  	trace_ext4_free_blocks(inode, block, count, flags);
  
  	if (bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
  		BUG_ON(count > 1);
  
  		ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
  			    inode, bh, block);
  	}
  
  	/*
  	 * We need to make sure we don't reuse the freed block until
  	 * after the transaction is committed, which we can do by
  	 * treating the block as metadata, below.  We make an
  	 * exception if the inode is to be written in writeback mode
  	 * since writeback mode has weak data consistency guarantees.
  	 */
  	if (!ext4_should_writeback_data(inode))
  		flags |= EXT4_FREE_BLOCKS_METADATA;
  
  	/*
  	 * If the extent to be freed does not begin on a cluster
  	 * boundary, we need to deal with partial clusters at the
  	 * beginning and end of the extent.  Normally we will free
  	 * blocks at the beginning or the end unless we are explicitly
  	 * requested to avoid doing so.
  	 */
  	overflow = EXT4_PBLK_COFF(sbi, block);
  	if (overflow) {
  		if (flags & EXT4_FREE_BLOCKS_NOFREE_FIRST_CLUSTER) {
  			overflow = sbi->s_cluster_ratio - overflow;
  			block += overflow;
  			if (count > overflow)
  				count -= overflow;
  			else
  				return;
  		} else {
  			block -= overflow;
  			count += overflow;
  		}
  	}
  	overflow = EXT4_LBLK_COFF(sbi, count);
  	if (overflow) {
  		if (flags & EXT4_FREE_BLOCKS_NOFREE_LAST_CLUSTER) {
  			if (count > overflow)
  				count -= overflow;
  			else
  				return;
  		} else
  			count += sbi->s_cluster_ratio - overflow;
  	}
  
  	if (!bh && (flags & EXT4_FREE_BLOCKS_FORGET)) {
  		int i;
  
  		for (i = 0; i < count; i++) {
  			cond_resched();
  			bh = sb_find_get_block(inode->i_sb, block + i);
  			if (!bh)
  				continue;
  			ext4_forget(handle, flags & EXT4_FREE_BLOCKS_METADATA,
  				    inode, bh, block + i);
  		}
  	}
  
  do_more:
  	overflow = 0;
  	ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
  
  	if (unlikely(EXT4_MB_GRP_BBITMAP_CORRUPT(
  			ext4_get_group_info(sb, block_group))))
  		return;
  
  	/*
  	 * Check to see if we are freeing blocks across a group
  	 * boundary.
  	 */
  	if (EXT4_C2B(sbi, bit) + count > EXT4_BLOCKS_PER_GROUP(sb)) {
  		overflow = EXT4_C2B(sbi, bit) + count -
  			EXT4_BLOCKS_PER_GROUP(sb);
  		count -= overflow;
  	}
  	count_clusters = EXT4_NUM_B2C(sbi, count);
  	bitmap_bh = ext4_read_block_bitmap(sb, block_group);
  	if (IS_ERR(bitmap_bh)) {
  		err = PTR_ERR(bitmap_bh);
  		bitmap_bh = NULL;
  		goto error_return;
  	}
  	gdp = ext4_get_group_desc(sb, block_group, &gd_bh);
  	if (!gdp) {
  		err = -EIO;
  		goto error_return;
  	}
  
  	if (in_range(ext4_block_bitmap(sb, gdp), block, count) ||
  	    in_range(ext4_inode_bitmap(sb, gdp), block, count) ||
  	    in_range(block, ext4_inode_table(sb, gdp),
  		     EXT4_SB(sb)->s_itb_per_group) ||
  	    in_range(block + count - 1, ext4_inode_table(sb, gdp),
  		     EXT4_SB(sb)->s_itb_per_group)) {
  
  		ext4_error(sb, "Freeing blocks in system zone - "
  			   "Block = %llu, count = %lu", block, count);
  		/* err = 0. ext4_std_error should be a no op */
  		goto error_return;
  	}
  
  	BUFFER_TRACE(bitmap_bh, "getting write access");
  	err = ext4_journal_get_write_access(handle, bitmap_bh);
  	if (err)
  		goto error_return;
  
  	/*
  	 * We are about to modify some metadata.  Call the journal APIs
  	 * to unshare ->b_data if a currently-committing transaction is
  	 * using it
  	 */
  	BUFFER_TRACE(gd_bh, "get_write_access");
  	err = ext4_journal_get_write_access(handle, gd_bh);
  	if (err)
  		goto error_return;
  #ifdef AGGRESSIVE_CHECK
  	{
  		int i;
  		for (i = 0; i < count_clusters; i++)
  			BUG_ON(!mb_test_bit(bit + i, bitmap_bh->b_data));
  	}
  #endif
  	trace_ext4_mballoc_free(sb, inode, block_group, bit, count_clusters);
  
  	/* __GFP_NOFAIL: retry infinitely, ignore TIF_MEMDIE and memcg limit. */
  	err = ext4_mb_load_buddy_gfp(sb, block_group, &e4b,
  				     GFP_NOFS|__GFP_NOFAIL);
  	if (err)
  		goto error_return;
  
  	if ((flags & EXT4_FREE_BLOCKS_METADATA) && ext4_handle_valid(handle)) {
  		struct ext4_free_data *new_entry;
  		/*
  		 * blocks being freed are metadata. these blocks shouldn't
  		 * be used until this transaction is committed
  		 *
  		 * We use __GFP_NOFAIL because ext4_free_blocks() is not allowed
  		 * to fail.
  		 */
  		new_entry = kmem_cache_alloc(ext4_free_data_cachep,
  				GFP_NOFS|__GFP_NOFAIL);
  		new_entry->efd_start_cluster = bit;
  		new_entry->efd_group = block_group;
  		new_entry->efd_count = count_clusters;
  		new_entry->efd_tid = handle->h_transaction->t_tid;
  
  		ext4_lock_group(sb, block_group);
  		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
  		ext4_mb_free_metadata(handle, &e4b, new_entry);
  	} else {
  		/* need to update group_info->bb_free and bitmap
  		 * with group lock held. generate_buddy look at
  		 * them with group lock_held
  		 */
  		if (test_opt(sb, DISCARD)) {
  			err = ext4_issue_discard(sb, block_group, bit, count);
  			if (err && err != -EOPNOTSUPP)
  				ext4_msg(sb, KERN_WARNING, "discard request in"
  					 " group:%d block:%d count:%lu failed"
  					 " with %d", block_group, bit, count,
  					 err);
  		} else
  			EXT4_MB_GRP_CLEAR_TRIMMED(e4b.bd_info);
  
  		ext4_lock_group(sb, block_group);
  		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
  		mb_free_blocks(inode, &e4b, bit, count_clusters);
  	}
  
  	ret = ext4_free_group_clusters(sb, gdp) + count_clusters;
  	ext4_free_group_clusters_set(sb, gdp, ret);
  	ext4_block_bitmap_csum_set(sb, block_group, gdp, bitmap_bh);
  	ext4_group_desc_csum_set(sb, block_group, gdp);
  	ext4_unlock_group(sb, block_group);
  
  	if (sbi->s_log_groups_per_flex) {
  		ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
  		atomic64_add(count_clusters,
  			     &sbi->s_flex_groups[flex_group].free_clusters);
  	}
  
  	if (!(flags & EXT4_FREE_BLOCKS_NO_QUOT_UPDATE))
  		dquot_free_block(inode, EXT4_C2B(sbi, count_clusters));
  	percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);
  
  	ext4_mb_unload_buddy(&e4b);
  
  	/* We dirtied the bitmap block */
  	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
  	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
  
  	/* And the group descriptor block */
  	BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
  	ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
  	if (!err)
  		err = ret;
  
  	if (overflow && !err) {
  		block += count;
  		count = overflow;
  		put_bh(bitmap_bh);
  		goto do_more;
  	}
  error_return:
  	brelse(bitmap_bh);
  	ext4_std_error(sb, err);
  	return;
  }
  
  /**
   * ext4_group_add_blocks() -- Add given blocks to an existing group
   * @handle:			handle to this transaction
   * @sb:				super block
   * @block:			start physical block to add to the block group
   * @count:			number of blocks to free
   *
   * This marks the blocks as free in the bitmap and buddy.
   */
  int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
  			 ext4_fsblk_t block, unsigned long count)
  {
  	struct buffer_head *bitmap_bh = NULL;
  	struct buffer_head *gd_bh;
  	ext4_group_t block_group;
  	ext4_grpblk_t bit;
  	unsigned int i;
  	struct ext4_group_desc *desc;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_buddy e4b;
  	int err = 0, ret, blk_free_count;
  	ext4_grpblk_t blocks_freed;
  
  	ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
  
  	if (count == 0)
  		return 0;
  
  	ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
  	/*
  	 * Check to see if we are freeing blocks across a group
  	 * boundary.
  	 */
  	if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
  		ext4_warning(sb, "too much blocks added to group %u\n",
  			     block_group);
  		err = -EINVAL;
  		goto error_return;
  	}
  
  	bitmap_bh = ext4_read_block_bitmap(sb, block_group);
  	if (IS_ERR(bitmap_bh)) {
  		err = PTR_ERR(bitmap_bh);
  		bitmap_bh = NULL;
  		goto error_return;
  	}
  
  	desc = ext4_get_group_desc(sb, block_group, &gd_bh);
  	if (!desc) {
  		err = -EIO;
  		goto error_return;
  	}
  
  	if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
  	    in_range(ext4_inode_bitmap(sb, desc), block, count) ||
  	    in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
  	    in_range(block + count - 1, ext4_inode_table(sb, desc),
  		     sbi->s_itb_per_group)) {
  		ext4_error(sb, "Adding blocks in system zones - "
  			   "Block = %llu, count = %lu",
  			   block, count);
  		err = -EINVAL;
  		goto error_return;
  	}
  
  	BUFFER_TRACE(bitmap_bh, "getting write access");
  	err = ext4_journal_get_write_access(handle, bitmap_bh);
  	if (err)
  		goto error_return;
  
  	/*
  	 * We are about to modify some metadata.  Call the journal APIs
  	 * to unshare ->b_data if a currently-committing transaction is
  	 * using it
  	 */
  	BUFFER_TRACE(gd_bh, "get_write_access");
  	err = ext4_journal_get_write_access(handle, gd_bh);
  	if (err)
  		goto error_return;
  
  	for (i = 0, blocks_freed = 0; i < count; i++) {
  		BUFFER_TRACE(bitmap_bh, "clear bit");
  		if (!mb_test_bit(bit + i, bitmap_bh->b_data)) {
  			ext4_error(sb, "bit already cleared for block %llu",
  				   (ext4_fsblk_t)(block + i));
  			BUFFER_TRACE(bitmap_bh, "bit already cleared");
  		} else {
  			blocks_freed++;
  		}
  	}
  
  	err = ext4_mb_load_buddy(sb, block_group, &e4b);
  	if (err)
  		goto error_return;
  
  	/*
  	 * need to update group_info->bb_free and bitmap
  	 * with group lock held. generate_buddy look at
  	 * them with group lock_held
  	 */
  	ext4_lock_group(sb, block_group);
  	mb_clear_bits(bitmap_bh->b_data, bit, count);
  	mb_free_blocks(NULL, &e4b, bit, count);
  	blk_free_count = blocks_freed + ext4_free_group_clusters(sb, desc);
  	ext4_free_group_clusters_set(sb, desc, blk_free_count);
  	ext4_block_bitmap_csum_set(sb, block_group, desc, bitmap_bh);
  	ext4_group_desc_csum_set(sb, block_group, desc);
  	ext4_unlock_group(sb, block_group);
  	percpu_counter_add(&sbi->s_freeclusters_counter,
  			   EXT4_NUM_B2C(sbi, blocks_freed));
  
  	if (sbi->s_log_groups_per_flex) {
  		ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
  		atomic64_add(EXT4_NUM_B2C(sbi, blocks_freed),
  			     &sbi->s_flex_groups[flex_group].free_clusters);
  	}
  
  	ext4_mb_unload_buddy(&e4b);
  
  	/* We dirtied the bitmap block */
  	BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
  	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
  
  	/* And the group descriptor block */
  	BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
  	ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
  	if (!err)
  		err = ret;
  
  error_return:
  	brelse(bitmap_bh);
  	ext4_std_error(sb, err);
  	return err;
  }
  
  /**
   * ext4_trim_extent -- function to TRIM one single free extent in the group
   * @sb:		super block for the file system
   * @start:	starting block of the free extent in the alloc. group
   * @count:	number of blocks to TRIM
   * @group:	alloc. group we are working with
   * @e4b:	ext4 buddy for the group
   *
   * Trim "count" blocks starting at "start" in the "group". To assure that no
   * one will allocate those blocks, mark it as used in buddy bitmap. This must
   * be called with under the group lock.
   */
  static int ext4_trim_extent(struct super_block *sb, int start, int count,
  			     ext4_group_t group, struct ext4_buddy *e4b)
  __releases(bitlock)
  __acquires(bitlock)
  {
  	struct ext4_free_extent ex;
  	int ret = 0;
  
  	trace_ext4_trim_extent(sb, group, start, count);
  
  	assert_spin_locked(ext4_group_lock_ptr(sb, group));
  
  	ex.fe_start = start;
  	ex.fe_group = group;
  	ex.fe_len = count;
  
  	/*
  	 * Mark blocks used, so no one can reuse them while
  	 * being trimmed.
  	 */
  	mb_mark_used(e4b, &ex);
  	ext4_unlock_group(sb, group);
  	ret = ext4_issue_discard(sb, group, start, count);
  	ext4_lock_group(sb, group);
  	mb_free_blocks(NULL, e4b, start, ex.fe_len);
  	return ret;
  }
  
  /**
   * ext4_trim_all_free -- function to trim all free space in alloc. group
   * @sb:			super block for file system
   * @group:		group to be trimmed
   * @start:		first group block to examine
   * @max:		last group block to examine
   * @minblocks:		minimum extent block count
   *
   * ext4_trim_all_free walks through group's buddy bitmap searching for free
   * extents. When the free block is found, ext4_trim_extent is called to TRIM
   * the extent.
   *
   *
   * ext4_trim_all_free walks through group's block bitmap searching for free
   * extents. When the free extent is found, mark it as used in group buddy
   * bitmap. Then issue a TRIM command on this extent and free the extent in
   * the group buddy bitmap. This is done until whole group is scanned.
   */
  static ext4_grpblk_t
  ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
  		   ext4_grpblk_t start, ext4_grpblk_t max,
  		   ext4_grpblk_t minblocks)
  {
  	void *bitmap;
  	ext4_grpblk_t next, count = 0, free_count = 0;
  	struct ext4_buddy e4b;
  	int ret = 0;
  
  	trace_ext4_trim_all_free(sb, group, start, max);
  
  	ret = ext4_mb_load_buddy(sb, group, &e4b);
  	if (ret) {
  		ext4_error(sb, "Error in loading buddy "
  				"information for %u", group);
  		return ret;
  	}
  	bitmap = e4b.bd_bitmap;
  
  	ext4_lock_group(sb, group);
  	if (EXT4_MB_GRP_WAS_TRIMMED(e4b.bd_info) &&
  	    minblocks >= atomic_read(&EXT4_SB(sb)->s_last_trim_minblks))
  		goto out;
  
  	start = (e4b.bd_info->bb_first_free > start) ?
  		e4b.bd_info->bb_first_free : start;
  
  	while (start <= max) {
  		start = mb_find_next_zero_bit(bitmap, max + 1, start);
  		if (start > max)
  			break;
  		next = mb_find_next_bit(bitmap, max + 1, start);
  
  		if ((next - start) >= minblocks) {
  			ret = ext4_trim_extent(sb, start,
  					       next - start, group, &e4b);
  			if (ret && ret != -EOPNOTSUPP)
  				break;
  			ret = 0;
  			count += next - start;
  		}
  		free_count += next - start;
  		start = next + 1;
  
  		if (fatal_signal_pending(current)) {
  			count = -ERESTARTSYS;
  			break;
  		}
  
  		if (need_resched()) {
  			ext4_unlock_group(sb, group);
  			cond_resched();
  			ext4_lock_group(sb, group);
  		}
  
  		if ((e4b.bd_info->bb_free - free_count) < minblocks)
  			break;
  	}
  
  	if (!ret) {
  		ret = count;
  		EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
  	}
  out:
  	ext4_unlock_group(sb, group);
  	ext4_mb_unload_buddy(&e4b);
  
  	ext4_debug("trimmed %d blocks in the group %d\n",
  		count, group);
  
  	return ret;
  }
  
  /**
   * ext4_trim_fs() -- trim ioctl handle function
   * @sb:			superblock for filesystem
   * @range:		fstrim_range structure
   *
   * start:	First Byte to trim
   * len:		number of Bytes to trim from start
   * minlen:	minimum extent length in Bytes
   * ext4_trim_fs goes through all allocation groups containing Bytes from
   * start to start+len. For each such a group ext4_trim_all_free function
   * is invoked to trim all free space.
   */
  int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
  {
  	struct ext4_group_info *grp;
  	ext4_group_t group, first_group, last_group;
  	ext4_grpblk_t cnt = 0, first_cluster, last_cluster;
  	uint64_t start, end, minlen, trimmed = 0;
  	ext4_fsblk_t first_data_blk =
  			le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
  	ext4_fsblk_t max_blks = ext4_blocks_count(EXT4_SB(sb)->s_es);
  	int ret = 0;
  
  	start = range->start >> sb->s_blocksize_bits;
  	end = start + (range->len >> sb->s_blocksize_bits) - 1;
  	minlen = EXT4_NUM_B2C(EXT4_SB(sb),
  			      range->minlen >> sb->s_blocksize_bits);
  
  	if (minlen > EXT4_CLUSTERS_PER_GROUP(sb) ||
  	    start >= max_blks ||
  	    range->len < sb->s_blocksize)
  		return -EINVAL;
  	if (end >= max_blks)
  		end = max_blks - 1;
  	if (end <= first_data_blk)
  		goto out;
  	if (start < first_data_blk)
  		start = first_data_blk;
  
  	/* Determine first and last group to examine based on start and end */
  	ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) start,
  				     &first_group, &first_cluster);
  	ext4_get_group_no_and_offset(sb, (ext4_fsblk_t) end,
  				     &last_group, &last_cluster);
  
  	/* end now represents the last cluster to discard in this group */
  	end = EXT4_CLUSTERS_PER_GROUP(sb) - 1;
  
  	for (group = first_group; group <= last_group; group++) {
  		grp = ext4_get_group_info(sb, group);
  		/* We only do this if the grp has never been initialized */
  		if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  			ret = ext4_mb_init_group(sb, group, GFP_NOFS);
  			if (ret)
  				break;
  		}
  
  		/*
  		 * For all the groups except the last one, last cluster will
  		 * always be EXT4_CLUSTERS_PER_GROUP(sb)-1, so we only need to
  		 * change it for the last group, note that last_cluster is
  		 * already computed earlier by ext4_get_group_no_and_offset()
  		 */
  		if (group == last_group)
  			end = last_cluster;
  
  		if (grp->bb_free >= minlen) {
  			cnt = ext4_trim_all_free(sb, group, first_cluster,
  						end, minlen);
  			if (cnt < 0) {
  				ret = cnt;
  				break;
  			}
  			trimmed += cnt;
  		}
  
  		/*
  		 * For every group except the first one, we are sure
  		 * that the first cluster to discard will be cluster #0.
  		 */
  		first_cluster = 0;
  	}
  
  	if (!ret)
  		atomic_set(&EXT4_SB(sb)->s_last_trim_minblks, minlen);
  
  out:
  	range->len = EXT4_C2B(EXT4_SB(sb), trimmed) << sb->s_blocksize_bits;
  	return ret;
  }
  