text: /*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions
   * of the GNU General Public License version 2.
   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>
  #include <linux/blkdev.h>
  #include <linux/kthread.h>
  #include <linux/namei.h>
  #include <linux/mount.h>
  #include <linux/gfs2_ondisk.h>
  #include <linux/quotaops.h>
  
  #include "gfs2.h"
  #include "incore.h"
  #include "bmap.h"
  #include "glock.h"
  #include "glops.h"
  #include "inode.h"
  #include "recovery.h"
  #include "rgrp.h"
  #include "super.h"
  #include "sys.h"
  #include "util.h"
  #include "log.h"
  #include "quota.h"
  #include "dir.h"
  #include "trace_gfs2.h"
  
  #define DO 0
  #define UNDO 1
  
  static const u32 gfs2_old_fs_formats[] = {
          0
  };
  
  static const u32 gfs2_old_multihost_formats[] = {
          0
  };
  
  /**
   * gfs2_tune_init - Fill a gfs2_tune structure with default values
   * @gt: tune
   *
   */
  
  static void gfs2_tune_init(struct gfs2_tune *gt)
  {
  	spin_lock_init(&gt->gt_spin);
  
  	gt->gt_quota_simul_sync = 64;
  	gt->gt_quota_warn_period = 10;
  	gt->gt_quota_scale_num = 1;
  	gt->gt_quota_scale_den = 1;
  	gt->gt_new_files_jdata = 0;
  	gt->gt_max_readahead = 1 << 18;
  	gt->gt_complain_secs = 10;
  }
  
  static struct gfs2_sbd *init_sbd(struct super_block *sb)
  {
  	struct gfs2_sbd *sdp;
  
  	sdp = kzalloc(sizeof(struct gfs2_sbd), GFP_KERNEL);
  	if (!sdp)
  		return NULL;
  
  	sb->s_fs_info = sdp;
  	sdp->sd_vfs = sb;
  	set_bit(SDF_NOJOURNALID, &sdp->sd_flags);
  	gfs2_tune_init(&sdp->sd_tune);
  
  	init_waitqueue_head(&sdp->sd_glock_wait);
  	atomic_set(&sdp->sd_glock_disposal, 0);
  	spin_lock_init(&sdp->sd_statfs_spin);
  
  	spin_lock_init(&sdp->sd_rindex_spin);
  	mutex_init(&sdp->sd_rindex_mutex);
  	INIT_LIST_HEAD(&sdp->sd_rindex_list);
  	INIT_LIST_HEAD(&sdp->sd_rindex_mru_list);
  
  	INIT_LIST_HEAD(&sdp->sd_jindex_list);
  	spin_lock_init(&sdp->sd_jindex_spin);
  	mutex_init(&sdp->sd_jindex_mutex);
  
  	INIT_LIST_HEAD(&sdp->sd_quota_list);
  	mutex_init(&sdp->sd_quota_mutex);
  	init_waitqueue_head(&sdp->sd_quota_wait);
  	INIT_LIST_HEAD(&sdp->sd_trunc_list);
  	spin_lock_init(&sdp->sd_trunc_lock);
  
  	spin_lock_init(&sdp->sd_log_lock);
  	atomic_set(&sdp->sd_log_pinned, 0);
  	INIT_LIST_HEAD(&sdp->sd_log_le_buf);
  	INIT_LIST_HEAD(&sdp->sd_log_le_revoke);
  	INIT_LIST_HEAD(&sdp->sd_log_le_rg);
  	INIT_LIST_HEAD(&sdp->sd_log_le_databuf);
  	INIT_LIST_HEAD(&sdp->sd_log_le_ordered);
  
  	init_waitqueue_head(&sdp->sd_log_waitq);
  	init_waitqueue_head(&sdp->sd_logd_waitq);
  	INIT_LIST_HEAD(&sdp->sd_ail1_list);
  	INIT_LIST_HEAD(&sdp->sd_ail2_list);
  
  	init_rwsem(&sdp->sd_log_flush_lock);
  	atomic_set(&sdp->sd_log_in_flight, 0);
  	init_waitqueue_head(&sdp->sd_log_flush_wait);
  
  	INIT_LIST_HEAD(&sdp->sd_revoke_list);
  
  	mutex_init(&sdp->sd_freeze_lock);
  
  	return sdp;
  }
  
  
  /**
   * gfs2_check_sb - Check superblock
   * @sdp: the filesystem
   * @sb: The superblock
   * @silent: Don't print a message if the check fails
   *
   * Checks the version code of the FS is one that we understand how to
   * read and that the sizes of the various on-disk structures have not
   * changed.
   */
  
  static int gfs2_check_sb(struct gfs2_sbd *sdp, struct gfs2_sb_host *sb, int silent)
  {
  	unsigned int x;
  
  	if (sb->sb_magic != GFS2_MAGIC ||
  	    sb->sb_type != GFS2_METATYPE_SB) {
  		if (!silent)
  			printk(KERN_WARNING "GFS2: not a GFS2 filesystem\n");
  		return -EINVAL;
  	}
  
  	/*  If format numbers match exactly, we're done.  */
  
  	if (sb->sb_fs_format == GFS2_FORMAT_FS &&
  	    sb->sb_multihost_format == GFS2_FORMAT_MULTI)
  		return 0;
  
  	if (sb->sb_fs_format != GFS2_FORMAT_FS) {
  		for (x = 0; gfs2_old_fs_formats[x]; x++)
  			if (gfs2_old_fs_formats[x] == sb->sb_fs_format)
  				break;
  
  		if (!gfs2_old_fs_formats[x]) {
  			printk(KERN_WARNING
  			       "GFS2: code version (%u, %u) is incompatible "
  			       "with ondisk format (%u, %u)\n",
  			       GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
  			       sb->sb_fs_format, sb->sb_multihost_format);
  			printk(KERN_WARNING
  			       "GFS2: I don't know how to upgrade this FS\n");
  			return -EINVAL;
  		}
  	}
  
  	if (sb->sb_multihost_format != GFS2_FORMAT_MULTI) {
  		for (x = 0; gfs2_old_multihost_formats[x]; x++)
  			if (gfs2_old_multihost_formats[x] ==
  			    sb->sb_multihost_format)
  				break;
  
  		if (!gfs2_old_multihost_formats[x]) {
  			printk(KERN_WARNING
  			       "GFS2: code version (%u, %u) is incompatible "
  			       "with ondisk format (%u, %u)\n",
  			       GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
  			       sb->sb_fs_format, sb->sb_multihost_format);
  			printk(KERN_WARNING
  			       "GFS2: I don't know how to upgrade this FS\n");
  			return -EINVAL;
  		}
  	}
  
  	if (!sdp->sd_args.ar_upgrade) {
  		printk(KERN_WARNING
  		       "GFS2: code version (%u, %u) is incompatible "
  		       "with ondisk format (%u, %u)\n",
  		       GFS2_FORMAT_FS, GFS2_FORMAT_MULTI,
  		       sb->sb_fs_format, sb->sb_multihost_format);
  		printk(KERN_INFO
  		       "GFS2: Use the \"upgrade\" mount option to upgrade "
  		       "the FS\n");
  		printk(KERN_INFO "GFS2: See the manual for more details\n");
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static void end_bio_io_page(struct bio *bio, int error)
  {
  	struct page *page = bio->bi_private;
  
  	if (!error)
  		SetPageUptodate(page);
  	else
  		printk(KERN_WARNING "gfs2: error %d reading superblock\n", error);
  	unlock_page(page);
  }
  
  static void gfs2_sb_in(struct gfs2_sb_host *sb, const void *buf)
  {
  	const struct gfs2_sb *str = buf;
  
  	sb->sb_magic = be32_to_cpu(str->sb_header.mh_magic);
  	sb->sb_type = be32_to_cpu(str->sb_header.mh_type);
  	sb->sb_format = be32_to_cpu(str->sb_header.mh_format);
  	sb->sb_fs_format = be32_to_cpu(str->sb_fs_format);
  	sb->sb_multihost_format = be32_to_cpu(str->sb_multihost_format);
  	sb->sb_bsize = be32_to_cpu(str->sb_bsize);
  	sb->sb_bsize_shift = be32_to_cpu(str->sb_bsize_shift);
  	sb->sb_master_dir.no_addr = be64_to_cpu(str->sb_master_dir.no_addr);
  	sb->sb_master_dir.no_formal_ino = be64_to_cpu(str->sb_master_dir.no_formal_ino);
  	sb->sb_root_dir.no_addr = be64_to_cpu(str->sb_root_dir.no_addr);
  	sb->sb_root_dir.no_formal_ino = be64_to_cpu(str->sb_root_dir.no_formal_ino);
  
  	memcpy(sb->sb_lockproto, str->sb_lockproto, GFS2_LOCKNAME_LEN);
  	memcpy(sb->sb_locktable, str->sb_locktable, GFS2_LOCKNAME_LEN);
  	memcpy(sb->sb_uuid, str->sb_uuid, 16);
  }
  
  /**
   * gfs2_read_super - Read the gfs2 super block from disk
   * @sdp: The GFS2 super block
   * @sector: The location of the super block
   * @error: The error code to return
   *
   * This uses the bio functions to read the super block from disk
   * because we want to be 100% sure that we never read cached data.
   * A super block is read twice only during each GFS2 mount and is
   * never written to by the filesystem. The first time its read no
   * locks are held, and the only details which are looked at are those
   * relating to the locking protocol. Once locking is up and working,
   * the sb is read again under the lock to establish the location of
   * the master directory (contains pointers to journals etc) and the
   * root directory.
   *
   * Returns: 0 on success or error
   */
  
  static int gfs2_read_super(struct gfs2_sbd *sdp, sector_t sector)
  {
  	struct super_block *sb = sdp->sd_vfs;
  	struct gfs2_sb *p;
  	struct page *page;
  	struct bio *bio;
  
  	page = alloc_page(GFP_NOFS);
  	if (unlikely(!page))
  		return -ENOBUFS;
  
  	ClearPageUptodate(page);
  	ClearPageDirty(page);
  	lock_page(page);
  
  	bio = bio_alloc(GFP_NOFS, 1);
  	bio->bi_sector = sector * (sb->s_blocksize >> 9);
  	bio->bi_bdev = sb->s_bdev;
  	bio_add_page(bio, page, PAGE_SIZE, 0);
  
  	bio->bi_end_io = end_bio_io_page;
  	bio->bi_private = page;
  	submit_bio(READ_SYNC | REQ_META, bio);
  	wait_on_page_locked(page);
  	bio_put(bio);
  	if (!PageUptodate(page)) {
  		__free_page(page);
  		return -EIO;
  	}
  	p = kmap(page);
  	gfs2_sb_in(&sdp->sd_sb, p);
  	kunmap(page);
  	__free_page(page);
  	return 0;
  }
  
  /**
   * gfs2_read_sb - Read super block
   * @sdp: The GFS2 superblock
   * @silent: Don't print message if mount fails
   *
   */
  
  static int gfs2_read_sb(struct gfs2_sbd *sdp, int silent)
  {
  	u32 hash_blocks, ind_blocks, leaf_blocks;
  	u32 tmp_blocks;
  	unsigned int x;
  	int error;
  
  	error = gfs2_read_super(sdp, GFS2_SB_ADDR >> sdp->sd_fsb2bb_shift);
  	if (error) {
  		if (!silent)
  			fs_err(sdp, "can't read superblock\n");
  		return error;
  	}
  
  	error = gfs2_check_sb(sdp, &sdp->sd_sb, silent);
  	if (error)
  		return error;
  
  	sdp->sd_fsb2bb_shift = sdp->sd_sb.sb_bsize_shift -
  			       GFS2_BASIC_BLOCK_SHIFT;
  	sdp->sd_fsb2bb = 1 << sdp->sd_fsb2bb_shift;
  	sdp->sd_diptrs = (sdp->sd_sb.sb_bsize -
  			  sizeof(struct gfs2_dinode)) / sizeof(u64);
  	sdp->sd_inptrs = (sdp->sd_sb.sb_bsize -
  			  sizeof(struct gfs2_meta_header)) / sizeof(u64);
  	sdp->sd_jbsize = sdp->sd_sb.sb_bsize - sizeof(struct gfs2_meta_header);
  	sdp->sd_hash_bsize = sdp->sd_sb.sb_bsize / 2;
  	sdp->sd_hash_bsize_shift = sdp->sd_sb.sb_bsize_shift - 1;
  	sdp->sd_hash_ptrs = sdp->sd_hash_bsize / sizeof(u64);
  	sdp->sd_qc_per_block = (sdp->sd_sb.sb_bsize -
  				sizeof(struct gfs2_meta_header)) /
  			        sizeof(struct gfs2_quota_change);
  
  	/* Compute maximum reservation required to add a entry to a directory */
  
  	hash_blocks = DIV_ROUND_UP(sizeof(u64) * (1 << GFS2_DIR_MAX_DEPTH),
  			     sdp->sd_jbsize);
  
  	ind_blocks = 0;
  	for (tmp_blocks = hash_blocks; tmp_blocks > sdp->sd_diptrs;) {
  		tmp_blocks = DIV_ROUND_UP(tmp_blocks, sdp->sd_inptrs);
  		ind_blocks += tmp_blocks;
  	}
  
  	leaf_blocks = 2 + GFS2_DIR_MAX_DEPTH;
  
  	sdp->sd_max_dirres = hash_blocks + ind_blocks + leaf_blocks;
  
  	sdp->sd_heightsize[0] = sdp->sd_sb.sb_bsize -
  				sizeof(struct gfs2_dinode);
  	sdp->sd_heightsize[1] = sdp->sd_sb.sb_bsize * sdp->sd_diptrs;
  	for (x = 2;; x++) {
  		u64 space, d;
  		u32 m;
  
  		space = sdp->sd_heightsize[x - 1] * sdp->sd_inptrs;
  		d = space;
  		m = do_div(d, sdp->sd_inptrs);
  
  		if (d != sdp->sd_heightsize[x - 1] || m)
  			break;
  		sdp->sd_heightsize[x] = space;
  	}
  	sdp->sd_max_height = x;
  	sdp->sd_heightsize[x] = ~0;
  	gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT);
  
  	sdp->sd_jheightsize[0] = sdp->sd_sb.sb_bsize -
  				 sizeof(struct gfs2_dinode);
  	sdp->sd_jheightsize[1] = sdp->sd_jbsize * sdp->sd_diptrs;
  	for (x = 2;; x++) {
  		u64 space, d;
  		u32 m;
  
  		space = sdp->sd_jheightsize[x - 1] * sdp->sd_inptrs;
  		d = space;
  		m = do_div(d, sdp->sd_inptrs);
  
  		if (d != sdp->sd_jheightsize[x - 1] || m)
  			break;
  		sdp->sd_jheightsize[x] = space;
  	}
  	sdp->sd_max_jheight = x;
  	sdp->sd_jheightsize[x] = ~0;
  	gfs2_assert(sdp, sdp->sd_max_jheight <= GFS2_MAX_META_HEIGHT);
  
  	return 0;
  }
  
  static int init_names(struct gfs2_sbd *sdp, int silent)
  {
  	char *proto, *table;
  	int error = 0;
  
  	proto = sdp->sd_args.ar_lockproto;
  	table = sdp->sd_args.ar_locktable;
  
  	/*  Try to autodetect  */
  
  	if (!proto[0] || !table[0]) {
  		error = gfs2_read_super(sdp, GFS2_SB_ADDR >> sdp->sd_fsb2bb_shift);
  		if (error)
  			return error;
  
  		error = gfs2_check_sb(sdp, &sdp->sd_sb, silent);
  		if (error)
  			goto out;
  
  		if (!proto[0])
  			proto = sdp->sd_sb.sb_lockproto;
  		if (!table[0])
  			table = sdp->sd_sb.sb_locktable;
  	}
  
  	if (!table[0])
  		table = sdp->sd_vfs->s_id;
  
  	strlcpy(sdp->sd_proto_name, proto, GFS2_FSNAME_LEN);
  	strlcpy(sdp->sd_table_name, table, GFS2_FSNAME_LEN);
  
  	table = sdp->sd_table_name;
  	while ((table = strchr(table, '/')))
  		*table = '_';
  
  out:
  	return error;
  }
  
  static int init_locking(struct gfs2_sbd *sdp, struct gfs2_holder *mount_gh,
  			int undo)
  {
  	int error = 0;
  
  	if (undo)
  		goto fail_trans;
  
  	error = gfs2_glock_nq_num(sdp,
  				  GFS2_MOUNT_LOCK, &gfs2_nondisk_glops,
  				  LM_ST_EXCLUSIVE, LM_FLAG_NOEXP | GL_NOCACHE,
  				  mount_gh);
  	if (error) {
  		fs_err(sdp, "can't acquire mount glock: %d\n", error);
  		goto fail;
  	}
  
  	error = gfs2_glock_nq_num(sdp,
  				  GFS2_LIVE_LOCK, &gfs2_nondisk_glops,
  				  LM_ST_SHARED,
  				  LM_FLAG_NOEXP | GL_EXACT,
  				  &sdp->sd_live_gh);
  	if (error) {
  		fs_err(sdp, "can't acquire live glock: %d\n", error);
  		goto fail_mount;
  	}
  
  	error = gfs2_glock_get(sdp, GFS2_RENAME_LOCK, &gfs2_nondisk_glops,
  			       CREATE, &sdp->sd_rename_gl);
  	if (error) {
  		fs_err(sdp, "can't create rename glock: %d\n", error);
  		goto fail_live;
  	}
  
  	error = gfs2_glock_get(sdp, GFS2_TRANS_LOCK, &gfs2_trans_glops,
  			       CREATE, &sdp->sd_trans_gl);
  	if (error) {
  		fs_err(sdp, "can't create transaction glock: %d\n", error);
  		goto fail_rename;
  	}
  
  	return 0;
  
  fail_trans:
  	gfs2_glock_put(sdp->sd_trans_gl);
  fail_rename:
  	gfs2_glock_put(sdp->sd_rename_gl);
  fail_live:
  	gfs2_glock_dq_uninit(&sdp->sd_live_gh);
  fail_mount:
  	gfs2_glock_dq_uninit(mount_gh);
  fail:
  	return error;
  }
  
  static int gfs2_lookup_root(struct super_block *sb, struct dentry **dptr,
  			    u64 no_addr, const char *name)
  {
  	struct gfs2_sbd *sdp = sb->s_fs_info;
  	struct dentry *dentry;
  	struct inode *inode;
  
  	inode = gfs2_inode_lookup(sb, DT_DIR, no_addr, 0);
  	if (IS_ERR(inode)) {
  		fs_err(sdp, "can't read in %s inode: %ld\n", name, PTR_ERR(inode));
  		return PTR_ERR(inode);
  	}
  	dentry = d_alloc_root(inode);
  	if (!dentry) {
  		fs_err(sdp, "can't alloc %s dentry\n", name);
  		iput(inode);
  		return -ENOMEM;
  	}
  	dentry->d_op = &gfs2_dops;
  	*dptr = dentry;
  	return 0;
  }
  
  static int init_sb(struct gfs2_sbd *sdp, int silent)
  {
  	struct super_block *sb = sdp->sd_vfs;
  	struct gfs2_holder sb_gh;
  	u64 no_addr;
  	int ret;
  
  	ret = gfs2_glock_nq_num(sdp, GFS2_SB_LOCK, &gfs2_meta_glops,
  				LM_ST_SHARED, 0, &sb_gh);
  	if (ret) {
  		fs_err(sdp, "can't acquire superblock glock: %d\n", ret);
  		return ret;
  	}
  
  	ret = gfs2_read_sb(sdp, silent);
  	if (ret) {
  		fs_err(sdp, "can't read superblock: %d\n", ret);
  		goto out;
  	}
  
  	/* Set up the buffer cache and SB for real */
  	if (sdp->sd_sb.sb_bsize < bdev_logical_block_size(sb->s_bdev)) {
  		ret = -EINVAL;
  		fs_err(sdp, "FS block size (%u) is too small for device "
  		       "block size (%u)\n",
  		       sdp->sd_sb.sb_bsize, bdev_logical_block_size(sb->s_bdev));
  		goto out;
  	}
  	if (sdp->sd_sb.sb_bsize > PAGE_SIZE) {
  		ret = -EINVAL;
  		fs_err(sdp, "FS block size (%u) is too big for machine "
  		       "page size (%u)\n",
  		       sdp->sd_sb.sb_bsize, (unsigned int)PAGE_SIZE);
  		goto out;
  	}
  	sb_set_blocksize(sb, sdp->sd_sb.sb_bsize);
  
  	/* Get the root inode */
  	no_addr = sdp->sd_sb.sb_root_dir.no_addr;
  	ret = gfs2_lookup_root(sb, &sdp->sd_root_dir, no_addr, "root");
  	if (ret)
  		goto out;
  
  	/* Get the master inode */
  	no_addr = sdp->sd_sb.sb_master_dir.no_addr;
  	ret = gfs2_lookup_root(sb, &sdp->sd_master_dir, no_addr, "master");
  	if (ret) {
  		dput(sdp->sd_root_dir);
  		goto out;
  	}
  	sb->s_root = dget(sdp->sd_args.ar_meta ? sdp->sd_master_dir : sdp->sd_root_dir);
  out:
  	gfs2_glock_dq_uninit(&sb_gh);
  	return ret;
  }
  
  /**
   * map_journal_extents - create a reusable "extent" mapping from all logical
   * blocks to all physical blocks for the given journal.  This will save
   * us time when writing journal blocks.  Most journals will have only one
   * extent that maps all their logical blocks.  That's because gfs2.mkfs
   * arranges the journal blocks sequentially to maximize performance.
   * So the extent would map the first block for the entire file length.
   * However, gfs2_jadd can happen while file activity is happening, so
   * those journals may not be sequential.  Less likely is the case where
   * the users created their own journals by mounting the metafs and
   * laying it out.  But it's still possible.  These journals might have
   * several extents.
   *
   * TODO: This should be done in bigger chunks rather than one block at a time,
   *       but since it's only done at mount time, I'm not worried about the
   *       time it takes.
   */
  static int map_journal_extents(struct gfs2_sbd *sdp)
  {
  	struct gfs2_jdesc *jd = sdp->sd_jdesc;
  	unsigned int lb;
  	u64 db, prev_db; /* logical block, disk block, prev disk block */
  	struct gfs2_inode *ip = GFS2_I(jd->jd_inode);
  	struct gfs2_journal_extent *jext = NULL;
  	struct buffer_head bh;
  	int rc = 0;
  
  	prev_db = 0;
  
  	for (lb = 0; lb < ip->i_disksize >> sdp->sd_sb.sb_bsize_shift; lb++) {
  		bh.b_state = 0;
  		bh.b_blocknr = 0;
  		bh.b_size = 1 << ip->i_inode.i_blkbits;
  		rc = gfs2_block_map(jd->jd_inode, lb, &bh, 0);
  		db = bh.b_blocknr;
  		if (rc || !db) {
  			printk(KERN_INFO "GFS2 journal mapping error %d: lb="
  			       "%u db=%llu\n", rc, lb, (unsigned long long)db);
  			break;
  		}
  		if (!prev_db || db != prev_db + 1) {
  			jext = kzalloc(sizeof(struct gfs2_journal_extent),
  				       GFP_KERNEL);
  			if (!jext) {
  				printk(KERN_INFO "GFS2 error: out of memory "
  				       "mapping journal extents.\n");
  				rc = -ENOMEM;
  				break;
  			}
  			jext->dblock = db;
  			jext->lblock = lb;
  			jext->blocks = 1;
  			list_add_tail(&jext->extent_list, &jd->extent_list);
  		} else {
  			jext->blocks++;
  		}
  		prev_db = db;
  	}
  	return rc;
  }
  
  static void gfs2_others_may_mount(struct gfs2_sbd *sdp)
  {
  	char *message = "FIRSTMOUNT=Done";
  	char *envp[] = { message, NULL };
  	struct lm_lockstruct *ls = &sdp->sd_lockstruct;
  	ls->ls_first_done = 1;
  	kobject_uevent_env(&sdp->sd_kobj, KOBJ_CHANGE, envp);
  }
  
  /**
   * gfs2_jindex_hold - Grab a lock on the jindex
   * @sdp: The GFS2 superblock
   * @ji_gh: the holder for the jindex glock
   *
   * Returns: errno
   */
  
  static int gfs2_jindex_hold(struct gfs2_sbd *sdp, struct gfs2_holder *ji_gh)
  {
  	struct gfs2_inode *dip = GFS2_I(sdp->sd_jindex);
  	struct qstr name;
  	char buf[20];
  	struct gfs2_jdesc *jd;
  	int error;
  
  	name.name = buf;
  
  	mutex_lock(&sdp->sd_jindex_mutex);
  
  	for (;;) {
  		error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, ji_gh);
  		if (error)
  			break;
  
  		name.len = sprintf(buf, "journal%u", sdp->sd_journals);
  		name.hash = gfs2_disk_hash(name.name, name.len);
  
  		error = gfs2_dir_check(sdp->sd_jindex, &name, NULL);
  		if (error == -ENOENT) {
  			error = 0;
  			break;
  		}
  
  		gfs2_glock_dq_uninit(ji_gh);
  
  		if (error)
  			break;
  
  		error = -ENOMEM;
  		jd = kzalloc(sizeof(struct gfs2_jdesc), GFP_KERNEL);
  		if (!jd)
  			break;
  
  		INIT_LIST_HEAD(&jd->extent_list);
  		INIT_WORK(&jd->jd_work, gfs2_recover_func);
  		jd->jd_inode = gfs2_lookupi(sdp->sd_jindex, &name, 1);
  		if (!jd->jd_inode || IS_ERR(jd->jd_inode)) {
  			if (!jd->jd_inode)
  				error = -ENOENT;
  			else
  				error = PTR_ERR(jd->jd_inode);
  			kfree(jd);
  			break;
  		}
  
  		spin_lock(&sdp->sd_jindex_spin);
  		jd->jd_jid = sdp->sd_journals++;
  		list_add_tail(&jd->jd_list, &sdp->sd_jindex_list);
  		spin_unlock(&sdp->sd_jindex_spin);
  	}
  
  	mutex_unlock(&sdp->sd_jindex_mutex);
  
  	return error;
  }
  
  static int init_journal(struct gfs2_sbd *sdp, int undo)
  {
  	struct inode *master = sdp->sd_master_dir->d_inode;
  	struct gfs2_holder ji_gh;
  	struct gfs2_inode *ip;
  	int jindex = 1;
  	int error = 0;
  
  	if (undo) {
  		jindex = 0;
  		goto fail_jinode_gh;
  	}
  
  	sdp->sd_jindex = gfs2_lookup_simple(master, "jindex");
  	if (IS_ERR(sdp->sd_jindex)) {
  		fs_err(sdp, "can't lookup journal index: %d\n", error);
  		return PTR_ERR(sdp->sd_jindex);
  	}
  	ip = GFS2_I(sdp->sd_jindex);
  
  	/* Load in the journal index special file */
  
  	error = gfs2_jindex_hold(sdp, &ji_gh);
  	if (error) {
  		fs_err(sdp, "can't read journal index: %d\n", error);
  		goto fail;
  	}
  
  	error = -EUSERS;
  	if (!gfs2_jindex_size(sdp)) {
  		fs_err(sdp, "no journals!\n");
  		goto fail_jindex;
  	}
  
  	if (sdp->sd_args.ar_spectator) {
  		sdp->sd_jdesc = gfs2_jdesc_find(sdp, 0);
  		atomic_set(&sdp->sd_log_blks_free, sdp->sd_jdesc->jd_blocks);
  		atomic_set(&sdp->sd_log_thresh1, 2*sdp->sd_jdesc->jd_blocks/5);
  		atomic_set(&sdp->sd_log_thresh2, 4*sdp->sd_jdesc->jd_blocks/5);
  	} else {
  		if (sdp->sd_lockstruct.ls_jid >= gfs2_jindex_size(sdp)) {
  			fs_err(sdp, "can't mount journal #%u\n",
  			       sdp->sd_lockstruct.ls_jid);
  			fs_err(sdp, "there are only %u journals (0 - %u)\n",
  			       gfs2_jindex_size(sdp),
  			       gfs2_jindex_size(sdp) - 1);
  			goto fail_jindex;
  		}
  		sdp->sd_jdesc = gfs2_jdesc_find(sdp, sdp->sd_lockstruct.ls_jid);
  
  		error = gfs2_glock_nq_num(sdp, sdp->sd_lockstruct.ls_jid,
  					  &gfs2_journal_glops,
  					  LM_ST_EXCLUSIVE, LM_FLAG_NOEXP,
  					  &sdp->sd_journal_gh);
  		if (error) {
  			fs_err(sdp, "can't acquire journal glock: %d\n", error);
  			goto fail_jindex;
  		}
  
  		ip = GFS2_I(sdp->sd_jdesc->jd_inode);
  		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
  					   LM_FLAG_NOEXP | GL_EXACT | GL_NOCACHE,
  					   &sdp->sd_jinode_gh);
  		if (error) {
  			fs_err(sdp, "can't acquire journal inode glock: %d\n",
  			       error);
  			goto fail_journal_gh;
  		}
  
  		error = gfs2_jdesc_check(sdp->sd_jdesc);
  		if (error) {
  			fs_err(sdp, "my journal (%u) is bad: %d\n",
  			       sdp->sd_jdesc->jd_jid, error);
  			goto fail_jinode_gh;
  		}
  		atomic_set(&sdp->sd_log_blks_free, sdp->sd_jdesc->jd_blocks);
  		atomic_set(&sdp->sd_log_thresh1, 2*sdp->sd_jdesc->jd_blocks/5);
  		atomic_set(&sdp->sd_log_thresh2, 4*sdp->sd_jdesc->jd_blocks/5);
  
  		/* Map the extents for this journal's blocks */
  		map_journal_extents(sdp);
  	}
  	trace_gfs2_log_blocks(sdp, atomic_read(&sdp->sd_log_blks_free));
  
  	if (sdp->sd_lockstruct.ls_first) {
  		unsigned int x;
  		for (x = 0; x < sdp->sd_journals; x++) {
  			error = gfs2_recover_journal(gfs2_jdesc_find(sdp, x),
  						     true);
  			if (error) {
  				fs_err(sdp, "error recovering journal %u: %d\n",
  				       x, error);
  				goto fail_jinode_gh;
  			}
  		}
  
  		gfs2_others_may_mount(sdp);
  	} else if (!sdp->sd_args.ar_spectator) {
  		error = gfs2_recover_journal(sdp->sd_jdesc, true);
  		if (error) {
  			fs_err(sdp, "error recovering my journal: %d\n", error);
  			goto fail_jinode_gh;
  		}
  	}
  
  	set_bit(SDF_JOURNAL_CHECKED, &sdp->sd_flags);
  	gfs2_glock_dq_uninit(&ji_gh);
  	jindex = 0;
  
  	return 0;
  
  fail_jinode_gh:
  	if (!sdp->sd_args.ar_spectator)
  		gfs2_glock_dq_uninit(&sdp->sd_jinode_gh);
  fail_journal_gh:
  	if (!sdp->sd_args.ar_spectator)
  		gfs2_glock_dq_uninit(&sdp->sd_journal_gh);
  fail_jindex:
  	gfs2_jindex_free(sdp);
  	if (jindex)
  		gfs2_glock_dq_uninit(&ji_gh);
  fail:
  	iput(sdp->sd_jindex);
  	return error;
  }
  
  
  static int init_inodes(struct gfs2_sbd *sdp, int undo)
  {
  	int error = 0;
  	struct gfs2_inode *ip;
  	struct inode *master = sdp->sd_master_dir->d_inode;
  
  	if (undo)
  		goto fail_qinode;
  
  	error = init_journal(sdp, undo);
  	if (error)
  		goto fail;
  
  	/* Read in the master statfs inode */
  	sdp->sd_statfs_inode = gfs2_lookup_simple(master, "statfs");
  	if (IS_ERR(sdp->sd_statfs_inode)) {
  		error = PTR_ERR(sdp->sd_statfs_inode);
  		fs_err(sdp, "can't read in statfs inode: %d\n", error);
  		goto fail_journal;
  	}
  
  	/* Read in the resource index inode */
  	sdp->sd_rindex = gfs2_lookup_simple(master, "rindex");
  	if (IS_ERR(sdp->sd_rindex)) {
  		error = PTR_ERR(sdp->sd_rindex);
  		fs_err(sdp, "can't get resource index inode: %d\n", error);
  		goto fail_statfs;
  	}
  	ip = GFS2_I(sdp->sd_rindex);
  	sdp->sd_rindex_uptodate = 0;
  
  	/* Read in the quota inode */
  	sdp->sd_quota_inode = gfs2_lookup_simple(master, "quota");
  	if (IS_ERR(sdp->sd_quota_inode)) {
  		error = PTR_ERR(sdp->sd_quota_inode);
  		fs_err(sdp, "can't get quota file inode: %d\n", error);
  		goto fail_rindex;
  	}
  	return 0;
  
  fail_qinode:
  	iput(sdp->sd_quota_inode);
  fail_rindex:
  	gfs2_clear_rgrpd(sdp);
  	iput(sdp->sd_rindex);
  fail_statfs:
  	iput(sdp->sd_statfs_inode);
  fail_journal:
  	init_journal(sdp, UNDO);
  fail:
  	return error;
  }
  
  static int init_per_node(struct gfs2_sbd *sdp, int undo)
  {
  	struct inode *pn = NULL;
  	char buf[30];
  	int error = 0;
  	struct gfs2_inode *ip;
  	struct inode *master = sdp->sd_master_dir->d_inode;
  
  	if (sdp->sd_args.ar_spectator)
  		return 0;
  
  	if (undo)
  		goto fail_qc_gh;
  
  	pn = gfs2_lookup_simple(master, "per_node");
  	if (IS_ERR(pn)) {
  		error = PTR_ERR(pn);
  		fs_err(sdp, "can't find per_node directory: %d\n", error);
  		return error;
  	}
  
  	sprintf(buf, "statfs_change%u", sdp->sd_jdesc->jd_jid);
  	sdp->sd_sc_inode = gfs2_lookup_simple(pn, buf);
  	if (IS_ERR(sdp->sd_sc_inode)) {
  		error = PTR_ERR(sdp->sd_sc_inode);
  		fs_err(sdp, "can't find local \"sc\" file: %d\n", error);
  		goto fail;
  	}
  
  	sprintf(buf, "quota_change%u", sdp->sd_jdesc->jd_jid);
  	sdp->sd_qc_inode = gfs2_lookup_simple(pn, buf);
  	if (IS_ERR(sdp->sd_qc_inode)) {
  		error = PTR_ERR(sdp->sd_qc_inode);
  		fs_err(sdp, "can't find local \"qc\" file: %d\n", error);
  		goto fail_ut_i;
  	}
  
  	iput(pn);
  	pn = NULL;
  
  	ip = GFS2_I(sdp->sd_sc_inode);
  	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0,
  				   &sdp->sd_sc_gh);
  	if (error) {
  		fs_err(sdp, "can't lock local \"sc\" file: %d\n", error);
  		goto fail_qc_i;
  	}
  
  	ip = GFS2_I(sdp->sd_qc_inode);
  	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0,
  				   &sdp->sd_qc_gh);
  	if (error) {
  		fs_err(sdp, "can't lock local \"qc\" file: %d\n", error);
  		goto fail_ut_gh;
  	}
  
  	return 0;
  
  fail_qc_gh:
  	gfs2_glock_dq_uninit(&sdp->sd_qc_gh);
  fail_ut_gh:
  	gfs2_glock_dq_uninit(&sdp->sd_sc_gh);
  fail_qc_i:
  	iput(sdp->sd_qc_inode);
  fail_ut_i:
  	iput(sdp->sd_sc_inode);
  fail:
  	if (pn)
  		iput(pn);
  	return error;
  }
  
  static int init_threads(struct gfs2_sbd *sdp, int undo)
  {
  	struct task_struct *p;
  	int error = 0;
  
  	if (undo)
  		goto fail_quotad;
  
  	p = kthread_run(gfs2_logd, sdp, "gfs2_logd");
  	error = IS_ERR(p);
  	if (error) {
  		fs_err(sdp, "can't start logd thread: %d\n", error);
  		return error;
  	}
  	sdp->sd_logd_process = p;
  
  	p = kthread_run(gfs2_quotad, sdp, "gfs2_quotad");
  	error = IS_ERR(p);
  	if (error) {
  		fs_err(sdp, "can't start quotad thread: %d\n", error);
  		goto fail;
  	}
  	sdp->sd_quotad_process = p;
  
  	return 0;
  
  
  fail_quotad:
  	kthread_stop(sdp->sd_quotad_process);
  fail:
  	kthread_stop(sdp->sd_logd_process);
  	return error;
  }
  
  static const match_table_t nolock_tokens = {
  	{ Opt_jid, "jid=%d\n", },
  	{ Opt_err, NULL },
  };
  
  static void nolock_put_lock(struct kmem_cache *cachep, struct gfs2_glock *gl)
  {
  	struct gfs2_sbd *sdp = gl->gl_sbd;
  	kmem_cache_free(cachep, gl);
  	if (atomic_dec_and_test(&sdp->sd_glock_disposal))
  		wake_up(&sdp->sd_glock_wait);
  }
  
  static const struct lm_lockops nolock_ops = {
  	.lm_proto_name = "lock_nolock",
  	.lm_put_lock = nolock_put_lock,
  	.lm_tokens = &nolock_tokens,
  };
  
  /**
   * gfs2_lm_mount - mount a locking protocol
   * @sdp: the filesystem
   * @args: mount arguments
   * @silent: if 1, don't complain if the FS isn't a GFS2 fs
   *
   * Returns: errno
   */
  
  static int gfs2_lm_mount(struct gfs2_sbd *sdp, int silent)
  {
  	const struct lm_lockops *lm;
  	struct lm_lockstruct *ls = &sdp->sd_lockstruct;
  	struct gfs2_args *args = &sdp->sd_args;
  	const char *proto = sdp->sd_proto_name;
  	const char *table = sdp->sd_table_name;
  	const char *fsname;
  	char *o, *options;
  	int ret;
  
  	if (!strcmp("lock_nolock", proto)) {
  		lm = &nolock_ops;
  		sdp->sd_args.ar_localflocks = 1;
  		sdp->sd_args.ar_localcaching = 1;
  #ifdef CONFIG_GFS2_FS_LOCKING_DLM
  	} else if (!strcmp("lock_dlm", proto)) {
  		lm = &gfs2_dlm_ops;
  #endif
  	} else {
  		printk(KERN_INFO "GFS2: can't find protocol %s\n", proto);
  		return -ENOENT;
  	}
  
  	fs_info(sdp, "Trying to join cluster \"%s\", \"%s\"\n", proto, table);
  
  	ls->ls_ops = lm;
  	ls->ls_first = 1;
  
  	for (options = args->ar_hostdata; (o = strsep(&options, ":")); ) {
  		substring_t tmp[MAX_OPT_ARGS];
  		int token, option;
  
  		if (!o || !*o)
  			continue;
  
  		token = match_token(o, *lm->lm_tokens, tmp);
  		switch (token) {
  		case Opt_jid:
  			ret = match_int(&tmp[0], &option);
  			if (ret || option < 0) 
  				goto hostdata_error;
  			if (test_and_clear_bit(SDF_NOJOURNALID, &sdp->sd_flags))
  				ls->ls_jid = option;
  			break;
  		case Opt_id:
  			/* Obsolete, but left for backward compat purposes */
  			break;
  		case Opt_first:
  			ret = match_int(&tmp[0], &option);
  			if (ret || (option != 0 && option != 1))
  				goto hostdata_error;
  			ls->ls_first = option;
  			break;
  		case Opt_nodir:
  			ret = match_int(&tmp[0], &option);
  			if (ret || (option != 0 && option != 1))
  				goto hostdata_error;
  			ls->ls_nodir = option;
  			break;
  		case Opt_err:
  		default:
  hostdata_error:
  			fs_info(sdp, "unknown hostdata (%s)\n", o);
  			return -EINVAL;
  		}
  	}
  
  	if (sdp->sd_args.ar_spectator)
  		snprintf(sdp->sd_fsname, GFS2_FSNAME_LEN, "%s.s", table);
  	else
  		snprintf(sdp->sd_fsname, GFS2_FSNAME_LEN, "%s.%u", table,
  			 sdp->sd_lockstruct.ls_jid);
  
  	fsname = strchr(table, ':');
  	if (fsname)
  		fsname++;
  	if (lm->lm_mount == NULL) {
  		fs_info(sdp, "Now mounting FS...\n");
  		return 0;
  	}
  	ret = lm->lm_mount(sdp, fsname);
  	if (ret == 0)
  		fs_info(sdp, "Joined cluster. Now mounting FS...\n");
  	return ret;
  }
  
  void gfs2_lm_unmount(struct gfs2_sbd *sdp)
  {
  	const struct lm_lockops *lm = sdp->sd_lockstruct.ls_ops;
  	if (likely(!test_bit(SDF_SHUTDOWN, &sdp->sd_flags)) &&
  	    lm->lm_unmount)
  		lm->lm_unmount(sdp);
  }
  
  static int gfs2_journalid_wait(void *word)
  {
  	if (signal_pending(current))
  		return -EINTR;
  	schedule();
  	return 0;
  }
  
  static int wait_on_journal(struct gfs2_sbd *sdp)
  {
  	if (sdp->sd_args.ar_spectator)
  		return 0;
  	if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL)
  		return 0;
  
  	return wait_on_bit(&sdp->sd_flags, SDF_NOJOURNALID, gfs2_journalid_wait, TASK_INTERRUPTIBLE);
  }
  
  void gfs2_online_uevent(struct gfs2_sbd *sdp)
  {
  	struct super_block *sb = sdp->sd_vfs;
  	char ro[20];
  	char spectator[20];
  	char *envp[] = { ro, spectator, NULL };
  	sprintf(ro, "RDONLY=%d", (sb->s_flags & MS_RDONLY) ? 1 : 0);
  	sprintf(spectator, "SPECTATOR=%d", sdp->sd_args.ar_spectator ? 1 : 0);
  	kobject_uevent_env(&sdp->sd_kobj, KOBJ_ONLINE, envp);
  }
  
  /**
   * fill_super - Read in superblock
   * @sb: The VFS superblock
   * @data: Mount options
   * @silent: Don't complain if it's not a GFS2 filesystem
   *
   * Returns: errno
   */
  
  static int fill_super(struct super_block *sb, struct gfs2_args *args, int silent)
  {
  	struct gfs2_sbd *sdp;
  	struct gfs2_holder mount_gh;
  	int error;
  
  	sdp = init_sbd(sb);
  	if (!sdp) {
  		printk(KERN_WARNING "GFS2: can't alloc struct gfs2_sbd\n");
  		return -ENOMEM;
  	}
  	sdp->sd_args = *args;
  
  	if (sdp->sd_args.ar_spectator) {
                  sb->s_flags |= MS_RDONLY;
  		set_bit(SDF_NORECOVERY, &sdp->sd_flags);
  	}
  	if (sdp->sd_args.ar_posix_acl)
  		sb->s_flags |= MS_POSIXACL;
  	if (sdp->sd_args.ar_nobarrier)
  		set_bit(SDF_NOBARRIERS, &sdp->sd_flags);
  
  	sb->s_magic = GFS2_MAGIC;
  	sb->s_op = &gfs2_super_ops;
  	sb->s_export_op = &gfs2_export_ops;
  	sb->s_xattr = gfs2_xattr_handlers;
  	sb->s_qcop = &gfs2_quotactl_ops;
  	sb_dqopt(sb)->flags |= DQUOT_QUOTA_SYS_FILE;
  	sb->s_time_gran = 1;
  	sb->s_maxbytes = MAX_LFS_FILESIZE;
  
  	/* Set up the buffer cache and fill in some fake block size values
  	   to allow us to read-in the on-disk superblock. */
  	sdp->sd_sb.sb_bsize = sb_min_blocksize(sb, GFS2_BASIC_BLOCK);
  	sdp->sd_sb.sb_bsize_shift = sb->s_blocksize_bits;
  	sdp->sd_fsb2bb_shift = sdp->sd_sb.sb_bsize_shift -
                                 GFS2_BASIC_BLOCK_SHIFT;
  	sdp->sd_fsb2bb = 1 << sdp->sd_fsb2bb_shift;
  
  	sdp->sd_tune.gt_logd_secs = sdp->sd_args.ar_commit;
  	sdp->sd_tune.gt_quota_quantum = sdp->sd_args.ar_quota_quantum;
  	if (sdp->sd_args.ar_statfs_quantum) {
  		sdp->sd_tune.gt_statfs_slow = 0;
  		sdp->sd_tune.gt_statfs_quantum = sdp->sd_args.ar_statfs_quantum;
  	}
  	else {
  		sdp->sd_tune.gt_statfs_slow = 1;
  		sdp->sd_tune.gt_statfs_quantum = 30;
  	}
  
  	error = init_names(sdp, silent);
  	if (error)
  		goto fail;
  
  	gfs2_create_debugfs_file(sdp);
  
  	error = gfs2_sys_fs_add(sdp);
  	if (error)
  		goto fail;
  
  	error = gfs2_lm_mount(sdp, silent);
  	if (error)
  		goto fail_sys;
  
  	error = init_locking(sdp, &mount_gh, DO);
  	if (error)
  		goto fail_lm;
  
  	error = init_sb(sdp, silent);
  	if (error)
  		goto fail_locking;
  
  	error = wait_on_journal(sdp);
  	if (error)
  		goto fail_sb;
  
  	error = init_inodes(sdp, DO);
  	if (error)
  		goto fail_sb;
  
  	error = init_per_node(sdp, DO);
  	if (error)
  		goto fail_inodes;
  
  	error = gfs2_statfs_init(sdp);
  	if (error) {
  		fs_err(sdp, "can't initialize statfs subsystem: %d\n", error);
  		goto fail_per_node;
  	}
  
  	error = init_threads(sdp, DO);
  	if (error)
  		goto fail_per_node;
  
  	if (!(sb->s_flags & MS_RDONLY)) {
  		error = gfs2_make_fs_rw(sdp);
  		if (error) {
  			fs_err(sdp, "can't make FS RW: %d\n", error);
  			goto fail_threads;
  		}
  	}
  
  	gfs2_glock_dq_uninit(&mount_gh);
  	gfs2_online_uevent(sdp);
  	return 0;
  
  fail_threads:
  	init_threads(sdp, UNDO);
  fail_per_node:
  	init_per_node(sdp, UNDO);
  fail_inodes:
  	init_inodes(sdp, UNDO);
  fail_sb:
  	if (sdp->sd_root_dir)
  		dput(sdp->sd_root_dir);
  	if (sdp->sd_master_dir)
  		dput(sdp->sd_master_dir);
  	if (sb->s_root)
  		dput(sb->s_root);
  	sb->s_root = NULL;
  fail_locking:
  	init_locking(sdp, &mount_gh, UNDO);
  fail_lm:
  	invalidate_inodes(sb);
  	gfs2_gl_hash_clear(sdp);
  	gfs2_lm_unmount(sdp);
  fail_sys:
  	gfs2_sys_fs_del(sdp);
  fail:
  	gfs2_delete_debugfs_file(sdp);
  	kfree(sdp);
  	sb->s_fs_info = NULL;
  	return error;
  }
  
  static int set_gfs2_super(struct super_block *s, void *data)
  {
  	s->s_bdev = data;
  	s->s_dev = s->s_bdev->bd_dev;
  
  	/*
  	 * We set the bdi here to the queue backing, file systems can
  	 * overwrite this in ->fill_super()
  	 */
  	s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
  	return 0;
  }
  
  static int test_gfs2_super(struct super_block *s, void *ptr)
  {
  	struct block_device *bdev = ptr;
  	return (bdev == s->s_bdev);
  }
  
  /**
   * gfs2_get_sb - Get the GFS2 superblock
   * @fs_type: The GFS2 filesystem type
   * @flags: Mount flags
   * @dev_name: The name of the device
   * @data: The mount arguments
   * @mnt: The vfsmnt for this mount
   *
   * Q. Why not use get_sb_bdev() ?
   * A. We need to select one of two root directories to mount, independent
   *    of whether this is the initial, or subsequent, mount of this sb
   *
   * Returns: 0 or -ve on error
   */
  
  static int gfs2_get_sb(struct file_system_type *fs_type, int flags,
  		       const char *dev_name, void *data, struct vfsmount *mnt)
  {
  	struct block_device *bdev;
  	struct super_block *s;
  	fmode_t mode = FMODE_READ;
  	int error;
  	struct gfs2_args args;
  	struct gfs2_sbd *sdp;
  
  	if (!(flags & MS_RDONLY))
  		mode |= FMODE_WRITE;
  
  	bdev = open_bdev_exclusive(dev_name, mode, fs_type);
  	if (IS_ERR(bdev))
  		return PTR_ERR(bdev);
  
  	/*
  	 * once the super is inserted into the list by sget, s_umount
  	 * will protect the lockfs code from trying to start a snapshot
  	 * while we are mounting
  	 */
  	mutex_lock(&bdev->bd_fsfreeze_mutex);
  	if (bdev->bd_fsfreeze_count > 0) {
  		mutex_unlock(&bdev->bd_fsfreeze_mutex);
  		error = -EBUSY;
  		goto error_bdev;
  	}
  	s = sget(fs_type, test_gfs2_super, set_gfs2_super, bdev);
  	mutex_unlock(&bdev->bd_fsfreeze_mutex);
  	error = PTR_ERR(s);
  	if (IS_ERR(s))
  		goto error_bdev;
  
  	memset(&args, 0, sizeof(args));
  	args.ar_quota = GFS2_QUOTA_DEFAULT;
  	args.ar_data = GFS2_DATA_DEFAULT;
  	args.ar_commit = 30;
  	args.ar_statfs_quantum = 30;
  	args.ar_quota_quantum = 60;
  	args.ar_errors = GFS2_ERRORS_DEFAULT;
  
  	error = gfs2_mount_args(&args, data);
  	if (error) {
  		printk(KERN_WARNING "GFS2: can't parse mount arguments\n");
  		if (s->s_root)
  			goto error_super;
  		deactivate_locked_super(s);
  		return error;
  	}
  
  	if (s->s_root) {
  		error = -EBUSY;
  		if ((flags ^ s->s_flags) & MS_RDONLY)
  			goto error_super;
  		close_bdev_exclusive(bdev, mode);
  	} else {
  		char b[BDEVNAME_SIZE];
  
  		s->s_flags = flags;
  		s->s_mode = mode;
  		strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
  		sb_set_blocksize(s, block_size(bdev));
  		error = fill_super(s, &args, flags & MS_SILENT ? 1 : 0);
  		if (error) {
  			deactivate_locked_super(s);
  			return error;
  		}
  		s->s_flags |= MS_ACTIVE;
  		bdev->bd_super = s;
  	}
  
  	sdp = s->s_fs_info;
  	mnt->mnt_sb = s;
  	if (args.ar_meta)
  		mnt->mnt_root = dget(sdp->sd_master_dir);
  	else
  		mnt->mnt_root = dget(sdp->sd_root_dir);
  	return 0;
  
  error_super:
  	deactivate_locked_super(s);
  error_bdev:
  	close_bdev_exclusive(bdev, mode);
  	return error;
  }
  
  static int set_meta_super(struct super_block *s, void *ptr)
  {
  	return -EINVAL;
  }
  
  static int gfs2_get_sb_meta(struct file_system_type *fs_type, int flags,
  			    const char *dev_name, void *data, struct vfsmount *mnt)
  {
  	struct super_block *s;
  	struct gfs2_sbd *sdp;
  	struct path path;
  	int error;
  
  	error = kern_path(dev_name, LOOKUP_FOLLOW, &path);
  	if (error) {
  		printk(KERN_WARNING "GFS2: path_lookup on %s returned error %d\n",
  		       dev_name, error);
  		return error;
  	}
  	s = sget(&gfs2_fs_type, test_gfs2_super, set_meta_super,
  		 path.dentry->d_inode->i_sb->s_bdev);
  	path_put(&path);
  	if (IS_ERR(s)) {
  		printk(KERN_WARNING "GFS2: gfs2 mount does not exist\n");
  		return PTR_ERR(s);
  	}
  	if ((flags ^ s->s_flags) & MS_RDONLY) {
  		deactivate_locked_super(s);
  		return -EBUSY;
  	}
  	sdp = s->s_fs_info;
  	mnt->mnt_sb = s;
  	mnt->mnt_root = dget(sdp->sd_master_dir);
  	return 0;
  }
  
  static void gfs2_kill_sb(struct super_block *sb)
  {
  	struct gfs2_sbd *sdp = sb->s_fs_info;
  
  	if (sdp == NULL) {
  		kill_block_super(sb);
  		return;
  	}
  
  	gfs2_meta_syncfs(sdp);
  	dput(sdp->sd_root_dir);
  	dput(sdp->sd_master_dir);
  	sdp->sd_root_dir = NULL;
  	sdp->sd_master_dir = NULL;
  	shrink_dcache_sb(sb);
  	kill_block_super(sb);
  	gfs2_delete_debugfs_file(sdp);
  	kfree(sdp);
  }
  
  struct file_system_type gfs2_fs_type = {
  	.name = "gfs2",
  	.fs_flags = FS_REQUIRES_DEV,
  	.get_sb = gfs2_get_sb,
  	.kill_sb = gfs2_kill_sb,
  	.owner = THIS_MODULE,
  };
  
  struct file_system_type gfs2meta_fs_type = {
  	.name = "gfs2meta",
  	.fs_flags = FS_REQUIRES_DEV,
  	.get_sb = gfs2_get_sb_meta,
  	.owner = THIS_MODULE,
  };
  