text: /*
   * hugetlbpage-backed filesystem.  Based on ramfs.
   *
   * Nadia Yvette Chambers, 2002
   *
   * Copyright (C) 2002 Linus Torvalds.
   */
  
  #include <linux/module.h>
  #include <linux/thread_info.h>
  #include <asm/current.h>
  #include <linux/sched.h>		/* remove ASAP */
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/file.h>
  #include <linux/kernel.h>
  #include <linux/writeback.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <linux/init.h>
  #include <linux/string.h>
  #include <linux/capability.h>
  #include <linux/ctype.h>
  #include <linux/backing-dev.h>
  #include <linux/hugetlb.h>
  #include <linux/pagevec.h>
  #include <linux/parser.h>
  #include <linux/mman.h>
  #include <linux/slab.h>
  #include <linux/dnotify.h>
  #include <linux/statfs.h>
  #include <linux/security.h>
  #include <linux/magic.h>
  #include <linux/migrate.h>
  
  #include <asm/uaccess.h>
  
  static const struct super_operations hugetlbfs_ops;
  static const struct address_space_operations hugetlbfs_aops;
  const struct file_operations hugetlbfs_file_operations;
  static const struct inode_operations hugetlbfs_dir_inode_operations;
  static const struct inode_operations hugetlbfs_inode_operations;
  
  struct hugetlbfs_config {
  	kuid_t   uid;
  	kgid_t   gid;
  	umode_t mode;
  	long	nr_blocks;
  	long	nr_inodes;
  	struct hstate *hstate;
  };
  
  struct hugetlbfs_inode_info {
  	struct shared_policy policy;
  	struct inode vfs_inode;
  };
  
  static inline struct hugetlbfs_inode_info *HUGETLBFS_I(struct inode *inode)
  {
  	return container_of(inode, struct hugetlbfs_inode_info, vfs_inode);
  }
  
  static struct backing_dev_info hugetlbfs_backing_dev_info = {
  	.name		= "hugetlbfs",
  	.ra_pages	= 0,	/* No readahead */
  	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
  };
  
  int sysctl_hugetlb_shm_group;
  
  enum {
  	Opt_size, Opt_nr_inodes,
  	Opt_mode, Opt_uid, Opt_gid,
  	Opt_pagesize,
  	Opt_err,
  };
  
  static const match_table_t tokens = {
  	{Opt_size,	"size=%s"},
  	{Opt_nr_inodes,	"nr_inodes=%s"},
  	{Opt_mode,	"mode=%o"},
  	{Opt_uid,	"uid=%u"},
  	{Opt_gid,	"gid=%u"},
  	{Opt_pagesize,	"pagesize=%s"},
  	{Opt_err,	NULL},
  };
  
  static void huge_pagevec_release(struct pagevec *pvec)
  {
  	int i;
  
  	for (i = 0; i < pagevec_count(pvec); ++i)
  		put_page(pvec->pages[i]);
  
  	pagevec_reinit(pvec);
  }
  
  static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
  {
  	struct inode *inode = file_inode(file);
  	loff_t len, vma_len;
  	int ret;
  	struct hstate *h = hstate_file(file);
  
  	/*
  	 * vma address alignment (but not the pgoff alignment) has
  	 * already been checked by prepare_hugepage_range.  If you add
  	 * any error returns here, do so after setting VM_HUGETLB, so
  	 * is_vm_hugetlb_page tests below unmap_region go the right
  	 * way when do_mmap_pgoff unwinds (may be important on powerpc
  	 * and ia64).
  	 */
  	vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
  	vma->vm_ops = &hugetlb_vm_ops;
  
  	if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
  		return -EINVAL;
  
  	vma_len = (loff_t)(vma->vm_end - vma->vm_start);
  
  	mutex_lock(&inode->i_mutex);
  	file_accessed(file);
  
  	ret = -ENOMEM;
  	len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
  
  	if (hugetlb_reserve_pages(inode,
  				vma->vm_pgoff >> huge_page_order(h),
  				len >> huge_page_shift(h), vma,
  				vma->vm_flags))
  		goto out;
  
  	ret = 0;
  	hugetlb_prefault_arch_hook(vma->vm_mm);
  	if (vma->vm_flags & VM_WRITE && inode->i_size < len)
  		inode->i_size = len;
  out:
  	mutex_unlock(&inode->i_mutex);
  
  	return ret;
  }
  
  /*
   * Called under down_write(mmap_sem).
   */
  
  #ifndef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
  static unsigned long
  hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
  		unsigned long len, unsigned long pgoff, unsigned long flags)
  {
  	struct mm_struct *mm = current->mm;
  	struct vm_area_struct *vma;
  	struct hstate *h = hstate_file(file);
  	struct vm_unmapped_area_info info;
  
  	if (len & ~huge_page_mask(h))
  		return -EINVAL;
  	if (len > TASK_SIZE)
  		return -ENOMEM;
  
  	if (flags & MAP_FIXED) {
  		if (prepare_hugepage_range(file, addr, len))
  			return -EINVAL;
  		return addr;
  	}
  
  	if (addr) {
  		addr = ALIGN(addr, huge_page_size(h));
  		vma = find_vma(mm, addr);
  		if (TASK_SIZE - len >= addr &&
  		    (!vma || addr + len <= vma->vm_start))
  			return addr;
  	}
  
  	info.flags = 0;
  	info.length = len;
  	info.low_limit = TASK_UNMAPPED_BASE;
  	info.high_limit = TASK_SIZE;
  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
  	info.align_offset = 0;
  	return vm_unmapped_area(&info);
  }
  #endif
  
  static int
  hugetlbfs_read_actor(struct page *page, unsigned long offset,
  			char __user *buf, unsigned long count,
  			unsigned long size)
  {
  	char *kaddr;
  	unsigned long left, copied = 0;
  	int i, chunksize;
  
  	if (size > count)
  		size = count;
  
  	/* Find which 4k chunk and offset with in that chunk */
  	i = offset >> PAGE_CACHE_SHIFT;
  	offset = offset & ~PAGE_CACHE_MASK;
  
  	while (size) {
  		chunksize = PAGE_CACHE_SIZE;
  		if (offset)
  			chunksize -= offset;
  		if (chunksize > size)
  			chunksize = size;
  		kaddr = kmap(&page[i]);
  		left = __copy_to_user(buf, kaddr + offset, chunksize);
  		kunmap(&page[i]);
  		if (left) {
  			copied += (chunksize - left);
  			break;
  		}
  		offset = 0;
  		size -= chunksize;
  		buf += chunksize;
  		copied += chunksize;
  		i++;
  	}
  	return copied ? copied : -EFAULT;
  }
  
  /*
   * Support for read() - Find the page attached to f_mapping and copy out the
   * data. Its *very* similar to do_generic_mapping_read(), we can't use that
   * since it has PAGE_CACHE_SIZE assumptions.
   */
  static ssize_t hugetlbfs_read(struct file *filp, char __user *buf,
  			      size_t len, loff_t *ppos)
  {
  	struct hstate *h = hstate_file(filp);
  	struct address_space *mapping = filp->f_mapping;
  	struct inode *inode = mapping->host;
  	unsigned long index = *ppos >> huge_page_shift(h);
  	unsigned long offset = *ppos & ~huge_page_mask(h);
  	unsigned long end_index;
  	loff_t isize;
  	ssize_t retval = 0;
  
  	/* validate length */
  	if (len == 0)
  		goto out;
  
  	for (;;) {
  		struct page *page;
  		unsigned long nr, ret;
  		int ra;
  
  		/* nr is the maximum number of bytes to copy from this page */
  		nr = huge_page_size(h);
  		isize = i_size_read(inode);
  		if (!isize)
  			goto out;
  		end_index = (isize - 1) >> huge_page_shift(h);
  		if (index >= end_index) {
  			if (index > end_index)
  				goto out;
  			nr = ((isize - 1) & ~huge_page_mask(h)) + 1;
  			if (nr <= offset)
  				goto out;
  		}
  		nr = nr - offset;
  
  		/* Find the page */
  		page = find_lock_page(mapping, index);
  		if (unlikely(page == NULL)) {
  			/*
  			 * We have a HOLE, zero out the user-buffer for the
  			 * length of the hole or request.
  			 */
  			ret = len < nr ? len : nr;
  			if (clear_user(buf, ret))
  				ra = -EFAULT;
  			else
  				ra = 0;
  		} else {
  			unlock_page(page);
  
  			/*
  			 * We have the page, copy it to user space buffer.
  			 */
  			ra = hugetlbfs_read_actor(page, offset, buf, len, nr);
  			ret = ra;
  			page_cache_release(page);
  		}
  		if (ra < 0) {
  			if (retval == 0)
  				retval = ra;
  			goto out;
  		}
  
  		offset += ret;
  		retval += ret;
  		len -= ret;
  		index += offset >> huge_page_shift(h);
  		offset &= ~huge_page_mask(h);
  
  		/* short read or no more work */
  		if ((ret != nr) || (len == 0))
  			break;
  	}
  out:
  	*ppos = ((loff_t)index << huge_page_shift(h)) + offset;
  	return retval;
  }
  
  static int hugetlbfs_write_begin(struct file *file,
  			struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned flags,
  			struct page **pagep, void **fsdata)
  {
  	return -EINVAL;
  }
  
  static int hugetlbfs_write_end(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned copied,
  			struct page *page, void *fsdata)
  {
  	BUG();
  	return -EINVAL;
  }
  
  static void truncate_huge_page(struct page *page)
  {
  	cancel_dirty_page(page, /* No IO accounting for huge pages? */0);
  	ClearPageUptodate(page);
  	delete_from_page_cache(page);
  }
  
  static void truncate_hugepages(struct inode *inode, loff_t lstart)
  {
  	struct hstate *h = hstate_inode(inode);
  	struct address_space *mapping = &inode->i_data;
  	const pgoff_t start = lstart >> huge_page_shift(h);
  	struct pagevec pvec;
  	pgoff_t next;
  	int i, freed = 0;
  
  	pagevec_init(&pvec, 0);
  	next = start;
  	while (1) {
  		if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
  			if (next == start)
  				break;
  			next = start;
  			continue;
  		}
  
  		for (i = 0; i < pagevec_count(&pvec); ++i) {
  			struct page *page = pvec.pages[i];
  
  			lock_page(page);
  			if (page->index > next)
  				next = page->index;
  			++next;
  			truncate_huge_page(page);
  			unlock_page(page);
  			freed++;
  		}
  		huge_pagevec_release(&pvec);
  	}
  	BUG_ON(!lstart && mapping->nrpages);
  	hugetlb_unreserve_pages(inode, start, freed);
  }
  
  static void hugetlbfs_evict_inode(struct inode *inode)
  {
  	truncate_hugepages(inode, 0);
  	clear_inode(inode);
  }
  
  static inline void
  hugetlb_vmtruncate_list(struct rb_root *root, pgoff_t pgoff)
  {
  	struct vm_area_struct *vma;
  
  	vma_interval_tree_foreach(vma, root, pgoff, ULONG_MAX) {
  		unsigned long v_offset;
  
  		/*
  		 * Can the expression below overflow on 32-bit arches?
  		 * No, because the interval tree returns us only those vmas
  		 * which overlap the truncated area starting at pgoff,
  		 * and no vma on a 32-bit arch can span beyond the 4GB.
  		 */
  		if (vma->vm_pgoff < pgoff)
  			v_offset = (pgoff - vma->vm_pgoff) << PAGE_SHIFT;
  		else
  			v_offset = 0;
  
  		unmap_hugepage_range(vma, vma->vm_start + v_offset,
  				     vma->vm_end, NULL);
  	}
  }
  
  static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
  {
  	pgoff_t pgoff;
  	struct address_space *mapping = inode->i_mapping;
  	struct hstate *h = hstate_inode(inode);
  
  	BUG_ON(offset & ~huge_page_mask(h));
  	pgoff = offset >> PAGE_SHIFT;
  
  	i_size_write(inode, offset);
  	mutex_lock(&mapping->i_mmap_mutex);
  	if (!RB_EMPTY_ROOT(&mapping->i_mmap))
  		hugetlb_vmtruncate_list(&mapping->i_mmap, pgoff);
  	mutex_unlock(&mapping->i_mmap_mutex);
  	truncate_hugepages(inode, offset);
  	return 0;
  }
  
  static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
  {
  	struct inode *inode = dentry->d_inode;
  	struct hstate *h = hstate_inode(inode);
  	int error;
  	unsigned int ia_valid = attr->ia_valid;
  
  	BUG_ON(!inode);
  
  	error = inode_change_ok(inode, attr);
  	if (error)
  		return error;
  
  	if (ia_valid & ATTR_SIZE) {
  		error = -EINVAL;
  		if (attr->ia_size & ~huge_page_mask(h))
  			return -EINVAL;
  		error = hugetlb_vmtruncate(inode, attr->ia_size);
  		if (error)
  			return error;
  	}
  
  	setattr_copy(inode, attr);
  	mark_inode_dirty(inode);
  	return 0;
  }
  
  static struct inode *hugetlbfs_get_root(struct super_block *sb,
  					struct hugetlbfs_config *config)
  {
  	struct inode *inode;
  
  	inode = new_inode(sb);
  	if (inode) {
  		struct hugetlbfs_inode_info *info;
  		inode->i_ino = get_next_ino();
  		inode->i_mode = S_IFDIR | config->mode;
  		inode->i_uid = config->uid;
  		inode->i_gid = config->gid;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  		info = HUGETLBFS_I(inode);
  		mpol_shared_policy_init(&info->policy, NULL);
  		inode->i_op = &hugetlbfs_dir_inode_operations;
  		inode->i_fop = &simple_dir_operations;
  		/* directory inodes start off with i_nlink == 2 (for "." entry) */
  		inc_nlink(inode);
  		lockdep_annotate_inode_mutex_key(inode);
  	}
  	return inode;
  }
  
  /*
   * Hugetlbfs is not reclaimable; therefore its i_mmap_mutex will never
   * be taken from reclaim -- unlike regular filesystems. This needs an
   * annotation because huge_pmd_share() does an allocation under
   * i_mmap_mutex.
   */
  struct lock_class_key hugetlbfs_i_mmap_mutex_key;
  
  static struct inode *hugetlbfs_get_inode(struct super_block *sb,
  					struct inode *dir,
  					umode_t mode, dev_t dev)
  {
  	struct inode *inode;
  
  	inode = new_inode(sb);
  	if (inode) {
  		struct hugetlbfs_inode_info *info;
  		inode->i_ino = get_next_ino();
  		inode_init_owner(inode, dir, mode);
  		lockdep_set_class(&inode->i_mapping->i_mmap_mutex,
  				&hugetlbfs_i_mmap_mutex_key);
  		inode->i_mapping->a_ops = &hugetlbfs_aops;
  		inode->i_mapping->backing_dev_info =&hugetlbfs_backing_dev_info;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  		INIT_LIST_HEAD(&inode->i_mapping->private_list);
  		info = HUGETLBFS_I(inode);
  		/*
  		 * The policy is initialized here even if we are creating a
  		 * private inode because initialization simply creates an
  		 * an empty rb tree and calls spin_lock_init(), later when we
  		 * call mpol_free_shared_policy() it will just return because
  		 * the rb tree will still be empty.
  		 */
  		mpol_shared_policy_init(&info->policy, NULL);
  		switch (mode & S_IFMT) {
  		default:
  			init_special_inode(inode, mode, dev);
  			break;
  		case S_IFREG:
  			inode->i_op = &hugetlbfs_inode_operations;
  			inode->i_fop = &hugetlbfs_file_operations;
  			break;
  		case S_IFDIR:
  			inode->i_op = &hugetlbfs_dir_inode_operations;
  			inode->i_fop = &simple_dir_operations;
  
  			/* directory inodes start off with i_nlink == 2 (for "." entry) */
  			inc_nlink(inode);
  			break;
  		case S_IFLNK:
  			inode->i_op = &page_symlink_inode_operations;
  			break;
  		}
  		lockdep_annotate_inode_mutex_key(inode);
  	}
  	return inode;
  }
  
  /*
   * File creation. Allocate an inode, and we're done..
   */
  static int hugetlbfs_mknod(struct inode *dir,
  			struct dentry *dentry, umode_t mode, dev_t dev)
  {
  	struct inode *inode;
  	int error = -ENOSPC;
  
  	inode = hugetlbfs_get_inode(dir->i_sb, dir, mode, dev);
  	if (inode) {
  		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
  		d_instantiate(dentry, inode);
  		dget(dentry);	/* Extra count - pin the dentry in core */
  		error = 0;
  	}
  	return error;
  }
  
  static int hugetlbfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
  {
  	int retval = hugetlbfs_mknod(dir, dentry, mode | S_IFDIR, 0);
  	if (!retval)
  		inc_nlink(dir);
  	return retval;
  }
  
  static int hugetlbfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
  {
  	return hugetlbfs_mknod(dir, dentry, mode | S_IFREG, 0);
  }
  
  static int hugetlbfs_symlink(struct inode *dir,
  			struct dentry *dentry, const char *symname)
  {
  	struct inode *inode;
  	int error = -ENOSPC;
  
  	inode = hugetlbfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
  	if (inode) {
  		int l = strlen(symname)+1;
  		error = page_symlink(inode, symname, l);
  		if (!error) {
  			d_instantiate(dentry, inode);
  			dget(dentry);
  		} else
  			iput(inode);
  	}
  	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
  
  	return error;
  }
  
  /*
   * mark the head page dirty
   */
  static int hugetlbfs_set_page_dirty(struct page *page)
  {
  	struct page *head = compound_head(page);
  
  	SetPageDirty(head);
  	return 0;
  }
  
  static int hugetlbfs_migrate_page(struct address_space *mapping,
  				struct page *newpage, struct page *page,
  				enum migrate_mode mode)
  {
  	int rc;
  
  	rc = migrate_huge_page_move_mapping(mapping, newpage, page);
  	if (rc != MIGRATEPAGE_SUCCESS)
  		return rc;
  	migrate_page_copy(newpage, page);
  
  	return MIGRATEPAGE_SUCCESS;
  }
  
  static int hugetlbfs_statfs(struct dentry *dentry, struct kstatfs *buf)
  {
  	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(dentry->d_sb);
  	struct hstate *h = hstate_inode(dentry->d_inode);
  
  	buf->f_type = HUGETLBFS_MAGIC;
  	buf->f_bsize = huge_page_size(h);
  	if (sbinfo) {
  		spin_lock(&sbinfo->stat_lock);
  		/* If no limits set, just report 0 for max/free/used
  		 * blocks, like simple_statfs() */
  		if (sbinfo->spool) {
  			long free_pages;
  
  			spin_lock(&sbinfo->spool->lock);
  			buf->f_blocks = sbinfo->spool->max_hpages;
  			free_pages = sbinfo->spool->max_hpages
  				- sbinfo->spool->used_hpages;
  			buf->f_bavail = buf->f_bfree = free_pages;
  			spin_unlock(&sbinfo->spool->lock);
  			buf->f_files = sbinfo->max_inodes;
  			buf->f_ffree = sbinfo->free_inodes;
  		}
  		spin_unlock(&sbinfo->stat_lock);
  	}
  	buf->f_namelen = NAME_MAX;
  	return 0;
  }
  
  static void hugetlbfs_put_super(struct super_block *sb)
  {
  	struct hugetlbfs_sb_info *sbi = HUGETLBFS_SB(sb);
  
  	if (sbi) {
  		sb->s_fs_info = NULL;
  
  		if (sbi->spool)
  			hugepage_put_subpool(sbi->spool);
  
  		kfree(sbi);
  	}
  }
  
  static inline int hugetlbfs_dec_free_inodes(struct hugetlbfs_sb_info *sbinfo)
  {
  	if (sbinfo->free_inodes >= 0) {
  		spin_lock(&sbinfo->stat_lock);
  		if (unlikely(!sbinfo->free_inodes)) {
  			spin_unlock(&sbinfo->stat_lock);
  			return 0;
  		}
  		sbinfo->free_inodes--;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  
  	return 1;
  }
  
  static void hugetlbfs_inc_free_inodes(struct hugetlbfs_sb_info *sbinfo)
  {
  	if (sbinfo->free_inodes >= 0) {
  		spin_lock(&sbinfo->stat_lock);
  		sbinfo->free_inodes++;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  }
  
  
  static struct kmem_cache *hugetlbfs_inode_cachep;
  
  static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
  {
  	struct hugetlbfs_sb_info *sbinfo = HUGETLBFS_SB(sb);
  	struct hugetlbfs_inode_info *p;
  
  	if (unlikely(!hugetlbfs_dec_free_inodes(sbinfo)))
  		return NULL;
  	p = kmem_cache_alloc(hugetlbfs_inode_cachep, GFP_KERNEL);
  	if (unlikely(!p)) {
  		hugetlbfs_inc_free_inodes(sbinfo);
  		return NULL;
  	}
  	return &p->vfs_inode;
  }
  
  static void hugetlbfs_i_callback(struct rcu_head *head)
  {
  	struct inode *inode = container_of(head, struct inode, i_rcu);
  	kmem_cache_free(hugetlbfs_inode_cachep, HUGETLBFS_I(inode));
  }
  
  static void hugetlbfs_destroy_inode(struct inode *inode)
  {
  	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
  	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
  	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
  }
  
  static const struct address_space_operations hugetlbfs_aops = {
  	.write_begin	= hugetlbfs_write_begin,
  	.write_end	= hugetlbfs_write_end,
  	.set_page_dirty	= hugetlbfs_set_page_dirty,
  	.migratepage    = hugetlbfs_migrate_page,
  };
  
  
  static void init_once(void *foo)
  {
  	struct hugetlbfs_inode_info *ei = (struct hugetlbfs_inode_info *)foo;
  
  	inode_init_once(&ei->vfs_inode);
  }
  
  const struct file_operations hugetlbfs_file_operations = {
  	.read			= hugetlbfs_read,
  	.mmap			= hugetlbfs_file_mmap,
  	.fsync			= noop_fsync,
  	.get_unmapped_area	= hugetlb_get_unmapped_area,
  	.llseek		= default_llseek,
  };
  
  static const struct inode_operations hugetlbfs_dir_inode_operations = {
  	.create		= hugetlbfs_create,
  	.lookup		= simple_lookup,
  	.link		= simple_link,
  	.unlink		= simple_unlink,
  	.symlink	= hugetlbfs_symlink,
  	.mkdir		= hugetlbfs_mkdir,
  	.rmdir		= simple_rmdir,
  	.mknod		= hugetlbfs_mknod,
  	.rename		= simple_rename,
  	.setattr	= hugetlbfs_setattr,
  };
  
  static const struct inode_operations hugetlbfs_inode_operations = {
  	.setattr	= hugetlbfs_setattr,
  };
  
  static const struct super_operations hugetlbfs_ops = {
  	.alloc_inode    = hugetlbfs_alloc_inode,
  	.destroy_inode  = hugetlbfs_destroy_inode,
  	.evict_inode	= hugetlbfs_evict_inode,
  	.statfs		= hugetlbfs_statfs,
  	.put_super	= hugetlbfs_put_super,
  	.show_options	= generic_show_options,
  };
  
  static int
  hugetlbfs_parse_options(char *options, struct hugetlbfs_config *pconfig)
  {
  	char *p, *rest;
  	substring_t args[MAX_OPT_ARGS];
  	int option;
  	unsigned long long size = 0;
  	enum { NO_SIZE, SIZE_STD, SIZE_PERCENT } setsize = NO_SIZE;
  
  	if (!options)
  		return 0;
  
  	while ((p = strsep(&options, ",")) != NULL) {
  		int token;
  		if (!*p)
  			continue;
  
  		token = match_token(p, tokens, args);
  		switch (token) {
  		case Opt_uid:
  			if (match_int(&args[0], &option))
   				goto bad_val;
  			pconfig->uid = make_kuid(current_user_ns(), option);
  			if (!uid_valid(pconfig->uid))
  				goto bad_val;
  			break;
  
  		case Opt_gid:
  			if (match_int(&args[0], &option))
   				goto bad_val;
  			pconfig->gid = make_kgid(current_user_ns(), option);
  			if (!gid_valid(pconfig->gid))
  				goto bad_val;
  			break;
  
  		case Opt_mode:
  			if (match_octal(&args[0], &option))
   				goto bad_val;
  			pconfig->mode = option & 01777U;
  			break;
  
  		case Opt_size: {
  			/* memparse() will accept a K/M/G without a digit */
  			if (!isdigit(*args[0].from))
  				goto bad_val;
  			size = memparse(args[0].from, &rest);
  			setsize = SIZE_STD;
  			if (*rest == '%')
  				setsize = SIZE_PERCENT;
  			break;
  		}
  
  		case Opt_nr_inodes:
  			/* memparse() will accept a K/M/G without a digit */
  			if (!isdigit(*args[0].from))
  				goto bad_val;
  			pconfig->nr_inodes = memparse(args[0].from, &rest);
  			break;
  
  		case Opt_pagesize: {
  			unsigned long ps;
  			ps = memparse(args[0].from, &rest);
  			pconfig->hstate = size_to_hstate(ps);
  			if (!pconfig->hstate) {
  				printk(KERN_ERR
  				"hugetlbfs: Unsupported page size %lu MB\n",
  					ps >> 20);
  				return -EINVAL;
  			}
  			break;
  		}
  
  		default:
  			printk(KERN_ERR "hugetlbfs: Bad mount option: \"%s\"\n",
  				 p);
  			return -EINVAL;
  			break;
  		}
  	}
  
  	/* Do size after hstate is set up */
  	if (setsize > NO_SIZE) {
  		struct hstate *h = pconfig->hstate;
  		if (setsize == SIZE_PERCENT) {
  			size <<= huge_page_shift(h);
  			size *= h->max_huge_pages;
  			do_div(size, 100);
  		}
  		pconfig->nr_blocks = (size >> huge_page_shift(h));
  	}
  
  	return 0;
  
  bad_val:
   	printk(KERN_ERR "hugetlbfs: Bad value '%s' for mount option '%s'\n",
  	       args[0].from, p);
   	return -EINVAL;
  }
  
  static int
  hugetlbfs_fill_super(struct super_block *sb, void *data, int silent)
  {
  	int ret;
  	struct hugetlbfs_config config;
  	struct hugetlbfs_sb_info *sbinfo;
  
  	save_mount_options(sb, data);
  
  	config.nr_blocks = -1; /* No limit on size by default */
  	config.nr_inodes = -1; /* No limit on number of inodes by default */
  	config.uid = current_fsuid();
  	config.gid = current_fsgid();
  	config.mode = 0755;
  	config.hstate = &default_hstate;
  	ret = hugetlbfs_parse_options(data, &config);
  	if (ret)
  		return ret;
  
  	sbinfo = kmalloc(sizeof(struct hugetlbfs_sb_info), GFP_KERNEL);
  	if (!sbinfo)
  		return -ENOMEM;
  	sb->s_fs_info = sbinfo;
  	sbinfo->hstate = config.hstate;
  	spin_lock_init(&sbinfo->stat_lock);
  	sbinfo->max_inodes = config.nr_inodes;
  	sbinfo->free_inodes = config.nr_inodes;
  	sbinfo->spool = NULL;
  	if (config.nr_blocks != -1) {
  		sbinfo->spool = hugepage_new_subpool(config.nr_blocks);
  		if (!sbinfo->spool)
  			goto out_free;
  	}
  	sb->s_maxbytes = MAX_LFS_FILESIZE;
  	sb->s_blocksize = huge_page_size(config.hstate);
  	sb->s_blocksize_bits = huge_page_shift(config.hstate);
  	sb->s_magic = HUGETLBFS_MAGIC;
  	sb->s_op = &hugetlbfs_ops;
  	sb->s_time_gran = 1;
  	sb->s_root = d_make_root(hugetlbfs_get_root(sb, &config));
  	if (!sb->s_root)
  		goto out_free;
  	return 0;
  out_free:
  	if (sbinfo->spool)
  		kfree(sbinfo->spool);
  	kfree(sbinfo);
  	return -ENOMEM;
  }
  
  static struct dentry *hugetlbfs_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)
  {
  	return mount_nodev(fs_type, flags, data, hugetlbfs_fill_super);
  }
  
  static struct file_system_type hugetlbfs_fs_type = {
  	.name		= "hugetlbfs",
  	.mount		= hugetlbfs_mount,
  	.kill_sb	= kill_litter_super,
  };
  MODULE_ALIAS_FS("hugetlbfs");
  
  static struct vfsmount *hugetlbfs_vfsmount[HUGE_MAX_HSTATE];
  
  static int can_do_hugetlb_shm(void)
  {
  	kgid_t shm_group;
  	shm_group = make_kgid(&init_user_ns, sysctl_hugetlb_shm_group);
  	return capable(CAP_IPC_LOCK) || in_group_p(shm_group);
  }
  
  static int get_hstate_idx(int page_size_log)
  {
  	struct hstate *h = hstate_sizelog(page_size_log);
  
  	if (!h)
  		return -1;
  	return h - hstates;
  }
  
  static struct dentry_operations anon_ops = {
  	.d_dname = simple_dname
  };
  
  /*
   * Note that size should be aligned to proper hugepage size in caller side,
   * otherwise hugetlb_reserve_pages reserves one less hugepages than intended.
   */
  struct file *hugetlb_file_setup(const char *name, size_t size,
  				vm_flags_t acctflag, struct user_struct **user,
  				int creat_flags, int page_size_log)
  {
  	struct file *file = ERR_PTR(-ENOMEM);
  	struct inode *inode;
  	struct path path;
  	struct super_block *sb;
  	struct qstr quick_string;
  	int hstate_idx;
  
  	hstate_idx = get_hstate_idx(page_size_log);
  	if (hstate_idx < 0)
  		return ERR_PTR(-ENODEV);
  
  	*user = NULL;
  	if (!hugetlbfs_vfsmount[hstate_idx])
  		return ERR_PTR(-ENOENT);
  
  	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
  		*user = current_user();
  		if (user_shm_lock(size, *user)) {
  			task_lock(current);
  			printk_once(KERN_WARNING
  				"%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
  				current->comm, current->pid);
  			task_unlock(current);
  		} else {
  			*user = NULL;
  			return ERR_PTR(-EPERM);
  		}
  	}
  
  	sb = hugetlbfs_vfsmount[hstate_idx]->mnt_sb;
  	quick_string.name = name;
  	quick_string.len = strlen(quick_string.name);
  	quick_string.hash = 0;
  	path.dentry = d_alloc_pseudo(sb, &quick_string);
  	if (!path.dentry)
  		goto out_shm_unlock;
  
  	d_set_d_op(path.dentry, &anon_ops);
  	path.mnt = mntget(hugetlbfs_vfsmount[hstate_idx]);
  	file = ERR_PTR(-ENOSPC);
  	inode = hugetlbfs_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0);
  	if (!inode)
  		goto out_dentry;
  
  	file = ERR_PTR(-ENOMEM);
  	if (hugetlb_reserve_pages(inode, 0,
  			size >> huge_page_shift(hstate_inode(inode)), NULL,
  			acctflag))
  		goto out_inode;
  
  	d_instantiate(path.dentry, inode);
  	inode->i_size = size;
  	clear_nlink(inode);
  
  	file = alloc_file(&path, FMODE_WRITE | FMODE_READ,
  			&hugetlbfs_file_operations);
  	if (IS_ERR(file))
  		goto out_dentry; /* inode is already attached */
  
  	return file;
  
  out_inode:
  	iput(inode);
  out_dentry:
  	path_put(&path);
  out_shm_unlock:
  	if (*user) {
  		user_shm_unlock(size, *user);
  		*user = NULL;
  	}
  	return file;
  }
  
  static int __init init_hugetlbfs_fs(void)
  {
  	struct hstate *h;
  	int error;
  	int i;
  
  	error = bdi_init(&hugetlbfs_backing_dev_info);
  	if (error)
  		return error;
  
  	error = -ENOMEM;
  	hugetlbfs_inode_cachep = kmem_cache_create("hugetlbfs_inode_cache",
  					sizeof(struct hugetlbfs_inode_info),
  					0, 0, init_once);
  	if (hugetlbfs_inode_cachep == NULL)
  		goto out2;
  
  	error = register_filesystem(&hugetlbfs_fs_type);
  	if (error)
  		goto out;
  
  	i = 0;
  	for_each_hstate(h) {
  		char buf[50];
  		unsigned ps_kb = 1U << (h->order + PAGE_SHIFT - 10);
  
  		snprintf(buf, sizeof(buf), "pagesize=%uK", ps_kb);
  		hugetlbfs_vfsmount[i] = kern_mount_data(&hugetlbfs_fs_type,
  							buf);
  
  		if (IS_ERR(hugetlbfs_vfsmount[i])) {
  			pr_err("hugetlb: Cannot mount internal hugetlbfs for "
  				"page size %uK", ps_kb);
  			error = PTR_ERR(hugetlbfs_vfsmount[i]);
  			hugetlbfs_vfsmount[i] = NULL;
  		}
  		i++;
  	}
  	/* Non default hstates are optional */
  	if (!IS_ERR_OR_NULL(hugetlbfs_vfsmount[default_hstate_idx]))
  		return 0;
  
   out:
  	kmem_cache_destroy(hugetlbfs_inode_cachep);
   out2:
  	bdi_destroy(&hugetlbfs_backing_dev_info);
  	return error;
  }
  
  static void __exit exit_hugetlbfs_fs(void)
  {
  	struct hstate *h;
  	int i;
  
  
  	/*
  	 * Make sure all delayed rcu free inodes are flushed before we
  	 * destroy cache.
  	 */
  	rcu_barrier();
  	kmem_cache_destroy(hugetlbfs_inode_cachep);
  	i = 0;
  	for_each_hstate(h)
  		kern_unmount(hugetlbfs_vfsmount[i++]);
  	unregister_filesystem(&hugetlbfs_fs_type);
  	bdi_destroy(&hugetlbfs_backing_dev_info);
  }
  
  module_init(init_hugetlbfs_fs)
  module_exit(exit_hugetlbfs_fs)
  
  MODULE_LICENSE("GPL");
  