/*
   * Resizable virtual memory filesystem for Linux.
   *
   * Copyright (C) 2000 Linus Torvalds.
   *		 2000 Transmeta Corp.
   *		 2000-2001 Christoph Rohland
   *		 2000-2001 SAP AG
   *		 2002 Red Hat Inc.

   * Copyright (C) 2002-2005 Hugh Dickins.
   * Copyright (C) 2002-2005 VERITAS Software Corporation.

   * Copyright (C) 2004 Andi Kleen, SuSE Labs
   *
   * Extended attribute support for tmpfs:
   * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@lkcl.net>
   * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
   *
   * This file is released under the GPL.
   */
  
  /*
   * This virtual memory filesystem is heavily based on the ramfs. It
   * extends ramfs by the ability to use swap and honor resource limits
   * which makes it a completely usable filesystem.
   */

  #include <linux/module.h>
  #include <linux/init.h>

  #include <linux/fs.h>

  #include <linux/xattr.h>

  #include <linux/exportfs.h>

  #include <linux/generic_acl.h>

  #include <linux/mm.h>
  #include <linux/mman.h>
  #include <linux/file.h>
  #include <linux/swap.h>
  #include <linux/pagemap.h>
  #include <linux/string.h>
  #include <linux/slab.h>
  #include <linux/backing-dev.h>
  #include <linux/shmem_fs.h>
  #include <linux/mount.h>
  #include <linux/writeback.h>
  #include <linux/vfs.h>
  #include <linux/blkdev.h>
  #include <linux/security.h>
  #include <linux/swapops.h>
  #include <linux/mempolicy.h>
  #include <linux/namei.h>

  #include <linux/ctype.h>

  #include <linux/migrate.h>

  #include <linux/highmem.h>

  #include <asm/uaccess.h>
  #include <asm/div64.h>
  #include <asm/pgtable.h>
  
  /* This magic number is used in glibc for posix shared memory */
  #define TMPFS_MAGIC	0x01021994
  
  #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
  #define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
  #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
  
  #define SHMEM_MAX_INDEX  (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
  #define SHMEM_MAX_BYTES  ((unsigned long long)SHMEM_MAX_INDEX << PAGE_CACHE_SHIFT)
  
  #define VM_ACCT(size)    (PAGE_CACHE_ALIGN(size) >> PAGE_SHIFT)
  
  /* info->flags needs VM_flags to handle pagein/truncate races efficiently */
  #define SHMEM_PAGEIN	 VM_READ
  #define SHMEM_TRUNCATE	 VM_WRITE
  
  /* Definition to limit shmem_truncate's steps between cond_rescheds */
  #define LATENCY_LIMIT	 64
  
  /* Pretend that each entry is of this size in directory's i_size */
  #define BOGO_DIRENT_SIZE 20

  /* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
  enum sgp_type {
  	SGP_QUICK,	/* don't try more than file page cache lookup */
  	SGP_READ,	/* don't exceed i_size, don't allocate page */
  	SGP_CACHE,	/* don't exceed i_size, may allocate page */
  	SGP_WRITE,	/* may exceed i_size, may allocate page */

  	SGP_FAULT,	/* same as SGP_CACHE, return with page locked */

  };
  
  static int shmem_getpage(struct inode *inode, unsigned long idx,
  			 struct page **pagep, enum sgp_type sgp, int *type);

  static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)

  {
  	/*
  	 * The above definition of ENTRIES_PER_PAGE, and the use of
  	 * BLOCKS_PER_PAGE on indirect pages, assume PAGE_CACHE_SIZE:
  	 * might be reconsidered if it ever diverges from PAGE_SIZE.

  	 *
  	 * __GFP_MOVABLE is masked out as swap vectors cannot move

  	 */

  	return alloc_pages((gfp_mask & ~__GFP_MOVABLE) | __GFP_ZERO,
  				PAGE_CACHE_SHIFT-PAGE_SHIFT);

  }
  
  static inline void shmem_dir_free(struct page *page)
  {
  	__free_pages(page, PAGE_CACHE_SHIFT-PAGE_SHIFT);
  }
  
  static struct page **shmem_dir_map(struct page *page)
  {
  	return (struct page **)kmap_atomic(page, KM_USER0);
  }
  
  static inline void shmem_dir_unmap(struct page **dir)
  {
  	kunmap_atomic(dir, KM_USER0);
  }
  
  static swp_entry_t *shmem_swp_map(struct page *page)
  {
  	return (swp_entry_t *)kmap_atomic(page, KM_USER1);
  }
  
  static inline void shmem_swp_balance_unmap(void)
  {
  	/*
  	 * When passing a pointer to an i_direct entry, to code which
  	 * also handles indirect entries and so will shmem_swp_unmap,
  	 * we must arrange for the preempt count to remain in balance.
  	 * What kmap_atomic of a lowmem page does depends on config
  	 * and architecture, so pretend to kmap_atomic some lowmem page.
  	 */
  	(void) kmap_atomic(ZERO_PAGE(0), KM_USER1);
  }
  
  static inline void shmem_swp_unmap(swp_entry_t *entry)
  {
  	kunmap_atomic(entry, KM_USER1);
  }
  
  static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
  {
  	return sb->s_fs_info;
  }
  
  /*
   * shmem_file_setup pre-accounts the whole fixed size of a VM object,
   * for shared memory and for shared anonymous (/dev/zero) mappings
   * (unless MAP_NORESERVE and sysctl_overcommit_memory <= 1),
   * consistent with the pre-accounting of private mappings ...
   */
  static inline int shmem_acct_size(unsigned long flags, loff_t size)
  {
  	return (flags & VM_ACCOUNT)?
  		security_vm_enough_memory(VM_ACCT(size)): 0;
  }
  
  static inline void shmem_unacct_size(unsigned long flags, loff_t size)
  {
  	if (flags & VM_ACCOUNT)
  		vm_unacct_memory(VM_ACCT(size));
  }
  
  /*
   * ... whereas tmpfs objects are accounted incrementally as
   * pages are allocated, in order to allow huge sparse files.
   * shmem_getpage reports shmem_acct_block failure as -ENOSPC not -ENOMEM,
   * so that a failure on a sparse tmpfs mapping will give SIGBUS not OOM.
   */
  static inline int shmem_acct_block(unsigned long flags)
  {
  	return (flags & VM_ACCOUNT)?
  		0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
  }
  
  static inline void shmem_unacct_blocks(unsigned long flags, long pages)
  {
  	if (!(flags & VM_ACCOUNT))
  		vm_unacct_memory(pages * VM_ACCT(PAGE_CACHE_SIZE));
  }

  static const struct super_operations shmem_ops;

  static const struct address_space_operations shmem_aops;

  static const struct file_operations shmem_file_operations;

  static const struct inode_operations shmem_inode_operations;
  static const struct inode_operations shmem_dir_inode_operations;
  static const struct inode_operations shmem_special_inode_operations;

  static struct vm_operations_struct shmem_vm_ops;

  static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {

  	.ra_pages	= 0,	/* No readahead */
  	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  	.unplug_io_fn	= default_unplug_io_fn,
  };
  
  static LIST_HEAD(shmem_swaplist);
  static DEFINE_SPINLOCK(shmem_swaplist_lock);
  
  static void shmem_free_blocks(struct inode *inode, long pages)
  {
  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);

  	if (sbinfo->max_blocks) {

  		spin_lock(&sbinfo->stat_lock);
  		sbinfo->free_blocks += pages;
  		inode->i_blocks -= pages*BLOCKS_PER_PAGE;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  }
  
  /*
   * shmem_recalc_inode - recalculate the size of an inode
   *
   * @inode: inode to recalc
   *
   * We have to calculate the free blocks since the mm can drop
   * undirtied hole pages behind our back.
   *
   * But normally   info->alloced == inode->i_mapping->nrpages + info->swapped
   * So mm freed is info->alloced - (inode->i_mapping->nrpages + info->swapped)
   *
   * It has to be called with the spinlock held.
   */
  static void shmem_recalc_inode(struct inode *inode)
  {
  	struct shmem_inode_info *info = SHMEM_I(inode);
  	long freed;
  
  	freed = info->alloced - info->swapped - inode->i_mapping->nrpages;
  	if (freed > 0) {
  		info->alloced -= freed;
  		shmem_unacct_blocks(info->flags, freed);
  		shmem_free_blocks(inode, freed);
  	}
  }
  
  /*
   * shmem_swp_entry - find the swap vector position in the info structure
   *
   * @info:  info structure for the inode
   * @index: index of the page to find
   * @page:  optional page to add to the structure. Has to be preset to
   *         all zeros
   *
   * If there is no space allocated yet it will return NULL when
   * page is NULL, else it will use the page for the needed block,
   * setting it to NULL on return to indicate that it has been used.
   *
   * The swap vector is organized the following way:
   *
   * There are SHMEM_NR_DIRECT entries directly stored in the
   * shmem_inode_info structure. So small files do not need an addional
   * allocation.
   *
   * For pages with index > SHMEM_NR_DIRECT there is the pointer
   * i_indirect which points to a page which holds in the first half
   * doubly indirect blocks, in the second half triple indirect blocks:
   *
   * For an artificial ENTRIES_PER_PAGE = 4 this would lead to the
   * following layout (for SHMEM_NR_DIRECT == 16):
   *
   * i_indirect -> dir --> 16-19
   * 	      |	     +-> 20-23
   * 	      |
   * 	      +-->dir2 --> 24-27
   * 	      |	       +-> 28-31
   * 	      |	       +-> 32-35
   * 	      |	       +-> 36-39
   * 	      |
   * 	      +-->dir3 --> 40-43
   * 	       	       +-> 44-47
   * 	      	       +-> 48-51
   * 	      	       +-> 52-55
   */
  static swp_entry_t *shmem_swp_entry(struct shmem_inode_info *info, unsigned long index, struct page **page)
  {
  	unsigned long offset;
  	struct page **dir;
  	struct page *subdir;
  
  	if (index < SHMEM_NR_DIRECT) {
  		shmem_swp_balance_unmap();
  		return info->i_direct+index;
  	}
  	if (!info->i_indirect) {
  		if (page) {
  			info->i_indirect = *page;
  			*page = NULL;
  		}
  		return NULL;			/* need another page */
  	}
  
  	index -= SHMEM_NR_DIRECT;
  	offset = index % ENTRIES_PER_PAGE;
  	index /= ENTRIES_PER_PAGE;
  	dir = shmem_dir_map(info->i_indirect);
  
  	if (index >= ENTRIES_PER_PAGE/2) {
  		index -= ENTRIES_PER_PAGE/2;
  		dir += ENTRIES_PER_PAGE/2 + index/ENTRIES_PER_PAGE;
  		index %= ENTRIES_PER_PAGE;
  		subdir = *dir;
  		if (!subdir) {
  			if (page) {
  				*dir = *page;
  				*page = NULL;
  			}
  			shmem_dir_unmap(dir);
  			return NULL;		/* need another page */
  		}
  		shmem_dir_unmap(dir);
  		dir = shmem_dir_map(subdir);
  	}
  
  	dir += index;
  	subdir = *dir;
  	if (!subdir) {
  		if (!page || !(subdir = *page)) {
  			shmem_dir_unmap(dir);
  			return NULL;		/* need a page */
  		}
  		*dir = subdir;
  		*page = NULL;
  	}
  	shmem_dir_unmap(dir);
  	return shmem_swp_map(subdir) + offset;
  }
  
  static void shmem_swp_set(struct shmem_inode_info *info, swp_entry_t *entry, unsigned long value)
  {
  	long incdec = value? 1: -1;
  
  	entry->val = value;
  	info->swapped += incdec;

  	if ((unsigned long)(entry - info->i_direct) >= SHMEM_NR_DIRECT) {
  		struct page *page = kmap_atomic_to_page(entry);
  		set_page_private(page, page_private(page) + incdec);
  	}

  }
  
  /*
   * shmem_swp_alloc - get the position of the swap entry for the page.
   *                   If it does not exist allocate the entry.
   *
   * @info:	info structure for the inode
   * @index:	index of the page to find
   * @sgp:	check and recheck i_size? skip allocation?
   */
  static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info, unsigned long index, enum sgp_type sgp)
  {
  	struct inode *inode = &info->vfs_inode;
  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
  	struct page *page = NULL;
  	swp_entry_t *entry;
  
  	if (sgp != SGP_WRITE &&
  	    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode))
  		return ERR_PTR(-EINVAL);
  
  	while (!(entry = shmem_swp_entry(info, index, &page))) {
  		if (sgp == SGP_READ)
  			return shmem_swp_map(ZERO_PAGE(0));
  		/*
  		 * Test free_blocks against 1 not 0, since we have 1 data
  		 * page (and perhaps indirect index pages) yet to allocate:
  		 * a waste to allocate index if we cannot allocate data.
  		 */

  		if (sbinfo->max_blocks) {

  			spin_lock(&sbinfo->stat_lock);
  			if (sbinfo->free_blocks <= 1) {
  				spin_unlock(&sbinfo->stat_lock);
  				return ERR_PTR(-ENOSPC);
  			}
  			sbinfo->free_blocks--;
  			inode->i_blocks += BLOCKS_PER_PAGE;
  			spin_unlock(&sbinfo->stat_lock);
  		}
  
  		spin_unlock(&info->lock);

  		page = shmem_dir_alloc(mapping_gfp_mask(inode->i_mapping));

  		if (page)
  			set_page_private(page, 0);

  		spin_lock(&info->lock);
  
  		if (!page) {
  			shmem_free_blocks(inode, 1);
  			return ERR_PTR(-ENOMEM);
  		}
  		if (sgp != SGP_WRITE &&
  		    ((loff_t) index << PAGE_CACHE_SHIFT) >= i_size_read(inode)) {
  			entry = ERR_PTR(-EINVAL);
  			break;
  		}
  		if (info->next_index <= index)
  			info->next_index = index + 1;
  	}
  	if (page) {
  		/* another task gave its page, or truncated the file */
  		shmem_free_blocks(inode, 1);
  		shmem_dir_free(page);
  	}
  	if (info->next_index <= index && !IS_ERR(entry))
  		info->next_index = index + 1;
  	return entry;
  }
  
  /*
   * shmem_free_swp - free some swap entries in a directory
   *

   * @dir:        pointer to the directory
   * @edir:       pointer after last entry of the directory
   * @punch_lock: pointer to spinlock when needed for the holepunch case

   */

  static int shmem_free_swp(swp_entry_t *dir, swp_entry_t *edir,
  						spinlock_t *punch_lock)

  {

  	spinlock_t *punch_unlock = NULL;

  	swp_entry_t *ptr;
  	int freed = 0;
  
  	for (ptr = dir; ptr < edir; ptr++) {
  		if (ptr->val) {

  			if (unlikely(punch_lock)) {
  				punch_unlock = punch_lock;
  				punch_lock = NULL;
  				spin_lock(punch_unlock);
  				if (!ptr->val)
  					continue;
  			}

  			free_swap_and_cache(*ptr);
  			*ptr = (swp_entry_t){0};
  			freed++;
  		}
  	}

  	if (punch_unlock)
  		spin_unlock(punch_unlock);

  	return freed;
  }

  static int shmem_map_and_free_swp(struct page *subdir, int offset,
  		int limit, struct page ***dir, spinlock_t *punch_lock)

  {
  	swp_entry_t *ptr;
  	int freed = 0;
  
  	ptr = shmem_swp_map(subdir);
  	for (; offset < limit; offset += LATENCY_LIMIT) {
  		int size = limit - offset;
  		if (size > LATENCY_LIMIT)
  			size = LATENCY_LIMIT;

  		freed += shmem_free_swp(ptr+offset, ptr+offset+size,
  							punch_lock);

  		if (need_resched()) {
  			shmem_swp_unmap(ptr);
  			if (*dir) {
  				shmem_dir_unmap(*dir);
  				*dir = NULL;
  			}
  			cond_resched();
  			ptr = shmem_swp_map(subdir);
  		}
  	}
  	shmem_swp_unmap(ptr);
  	return freed;
  }
  
  static void shmem_free_pages(struct list_head *next)
  {
  	struct page *page;
  	int freed = 0;
  
  	do {
  		page = container_of(next, struct page, lru);
  		next = next->next;
  		shmem_dir_free(page);
  		freed++;
  		if (freed >= LATENCY_LIMIT) {
  			cond_resched();
  			freed = 0;
  		}
  	} while (next);
  }

  static void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)

  {
  	struct shmem_inode_info *info = SHMEM_I(inode);
  	unsigned long idx;
  	unsigned long size;
  	unsigned long limit;
  	unsigned long stage;
  	unsigned long diroff;
  	struct page **dir;
  	struct page *topdir;
  	struct page *middir;
  	struct page *subdir;
  	swp_entry_t *ptr;
  	LIST_HEAD(pages_to_free);
  	long nr_pages_to_free = 0;
  	long nr_swaps_freed = 0;
  	int offset;
  	int freed;

  	int punch_hole;

  	spinlock_t *needs_lock;
  	spinlock_t *punch_lock;

  	unsigned long upper_limit;

  
  	inode->i_ctime = inode->i_mtime = CURRENT_TIME;

  	idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

  	if (idx >= info->next_index)
  		return;
  
  	spin_lock(&info->lock);
  	info->flags |= SHMEM_TRUNCATE;

  	if (likely(end == (loff_t) -1)) {
  		limit = info->next_index;

  		upper_limit = SHMEM_MAX_INDEX;

  		info->next_index = idx;

  		needs_lock = NULL;

  		punch_hole = 0;

  	} else {

  		if (end + 1 >= inode->i_size) {	/* we may free a little more */
  			limit = (inode->i_size + PAGE_CACHE_SIZE - 1) >>
  							PAGE_CACHE_SHIFT;
  			upper_limit = SHMEM_MAX_INDEX;
  		} else {
  			limit = (end + 1) >> PAGE_CACHE_SHIFT;
  			upper_limit = limit;
  		}

  		needs_lock = &info->lock;

  		punch_hole = 1;
  	}

  	topdir = info->i_indirect;

  	if (topdir && idx <= SHMEM_NR_DIRECT && !punch_hole) {

  		info->i_indirect = NULL;
  		nr_pages_to_free++;
  		list_add(&topdir->lru, &pages_to_free);
  	}
  	spin_unlock(&info->lock);
  
  	if (info->swapped && idx < SHMEM_NR_DIRECT) {
  		ptr = info->i_direct;
  		size = limit;
  		if (size > SHMEM_NR_DIRECT)
  			size = SHMEM_NR_DIRECT;

  		nr_swaps_freed = shmem_free_swp(ptr+idx, ptr+size, needs_lock);

  	}

  
  	/*
  	 * If there are no indirect blocks or we are punching a hole
  	 * below indirect blocks, nothing to be done.
  	 */

  	if (!topdir || limit <= SHMEM_NR_DIRECT)

  		goto done2;

  	/*
  	 * The truncation case has already dropped info->lock, and we're safe
  	 * because i_size and next_index have already been lowered, preventing
  	 * access beyond.  But in the punch_hole case, we still need to take
  	 * the lock when updating the swap directory, because there might be
  	 * racing accesses by shmem_getpage(SGP_CACHE), shmem_unuse_inode or
  	 * shmem_writepage.  However, whenever we find we can remove a whole
  	 * directory page (not at the misaligned start or end of the range),
  	 * we first NULLify its pointer in the level above, and then have no
  	 * need to take the lock when updating its contents: needs_lock and
  	 * punch_lock (either pointing to info->lock or NULL) manage this.
  	 */

  	upper_limit -= SHMEM_NR_DIRECT;

  	limit -= SHMEM_NR_DIRECT;
  	idx = (idx > SHMEM_NR_DIRECT)? (idx - SHMEM_NR_DIRECT): 0;
  	offset = idx % ENTRIES_PER_PAGE;
  	idx -= offset;
  
  	dir = shmem_dir_map(topdir);
  	stage = ENTRIES_PER_PAGEPAGE/2;
  	if (idx < ENTRIES_PER_PAGEPAGE/2) {
  		middir = topdir;
  		diroff = idx/ENTRIES_PER_PAGE;
  	} else {
  		dir += ENTRIES_PER_PAGE/2;
  		dir += (idx - ENTRIES_PER_PAGEPAGE/2)/ENTRIES_PER_PAGEPAGE;
  		while (stage <= idx)
  			stage += ENTRIES_PER_PAGEPAGE;
  		middir = *dir;
  		if (*dir) {
  			diroff = ((idx - ENTRIES_PER_PAGEPAGE/2) %
  				ENTRIES_PER_PAGEPAGE) / ENTRIES_PER_PAGE;

  			if (!diroff && !offset && upper_limit >= stage) {

  				if (needs_lock) {
  					spin_lock(needs_lock);
  					*dir = NULL;
  					spin_unlock(needs_lock);
  					needs_lock = NULL;
  				} else
  					*dir = NULL;

  				nr_pages_to_free++;
  				list_add(&middir->lru, &pages_to_free);
  			}
  			shmem_dir_unmap(dir);
  			dir = shmem_dir_map(middir);
  		} else {
  			diroff = 0;
  			offset = 0;
  			idx = stage;
  		}
  	}
  
  	for (; idx < limit; idx += ENTRIES_PER_PAGE, diroff++) {
  		if (unlikely(idx == stage)) {
  			shmem_dir_unmap(dir);
  			dir = shmem_dir_map(topdir) +
  			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
  			while (!*dir) {
  				dir++;
  				idx += ENTRIES_PER_PAGEPAGE;
  				if (idx >= limit)
  					goto done1;
  			}
  			stage = idx + ENTRIES_PER_PAGEPAGE;
  			middir = *dir;

  			if (punch_hole)
  				needs_lock = &info->lock;

  			if (upper_limit >= stage) {

  				if (needs_lock) {
  					spin_lock(needs_lock);
  					*dir = NULL;
  					spin_unlock(needs_lock);
  					needs_lock = NULL;
  				} else
  					*dir = NULL;

  				nr_pages_to_free++;
  				list_add(&middir->lru, &pages_to_free);
  			}

  			shmem_dir_unmap(dir);
  			cond_resched();
  			dir = shmem_dir_map(middir);
  			diroff = 0;
  		}

  		punch_lock = needs_lock;

  		subdir = dir[diroff];

  		if (subdir && !offset && upper_limit-idx >= ENTRIES_PER_PAGE) {
  			if (needs_lock) {
  				spin_lock(needs_lock);
  				dir[diroff] = NULL;
  				spin_unlock(needs_lock);
  				punch_lock = NULL;
  			} else
  				dir[diroff] = NULL;
  			nr_pages_to_free++;
  			list_add(&subdir->lru, &pages_to_free);
  		}
  		if (subdir && page_private(subdir) /* has swap entries */) {

  			size = limit - idx;
  			if (size > ENTRIES_PER_PAGE)
  				size = ENTRIES_PER_PAGE;
  			freed = shmem_map_and_free_swp(subdir,

  					offset, size, &dir, punch_lock);

  			if (!dir)
  				dir = shmem_dir_map(middir);
  			nr_swaps_freed += freed;

  			if (offset || punch_lock) {

  				spin_lock(&info->lock);

  				set_page_private(subdir,
  					page_private(subdir) - freed);

  				spin_unlock(&info->lock);

  			} else
  				BUG_ON(page_private(subdir) != freed);

  		}

  		offset = 0;

  	}
  done1:
  	shmem_dir_unmap(dir);
  done2:
  	if (inode->i_mapping->nrpages && (info->flags & SHMEM_PAGEIN)) {
  		/*
  		 * Call truncate_inode_pages again: racing shmem_unuse_inode
  		 * may have swizzled a page in from swap since vmtruncate or
  		 * generic_delete_inode did it, before we lowered next_index.
  		 * Also, though shmem_getpage checks i_size before adding to
  		 * cache, no recheck after: so fix the narrow window there too.

  		 *
  		 * Recalling truncate_inode_pages_range and unmap_mapping_range
  		 * every time for punch_hole (which never got a chance to clear
  		 * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
  		 * yet hardly ever necessary: try to optimize them out later.

  		 */

  		truncate_inode_pages_range(inode->i_mapping, start, end);

  		if (punch_hole)
  			unmap_mapping_range(inode->i_mapping, start,
  							end - start, 1);

  	}
  
  	spin_lock(&info->lock);
  	info->flags &= ~SHMEM_TRUNCATE;
  	info->swapped -= nr_swaps_freed;
  	if (nr_pages_to_free)
  		shmem_free_blocks(inode, nr_pages_to_free);
  	shmem_recalc_inode(inode);
  	spin_unlock(&info->lock);
  
  	/*
  	 * Empty swap vector directory pages to be freed?
  	 */
  	if (!list_empty(&pages_to_free)) {
  		pages_to_free.prev->next = NULL;
  		shmem_free_pages(pages_to_free.next);
  	}
  }

  static void shmem_truncate(struct inode *inode)
  {
  	shmem_truncate_range(inode, inode->i_size, (loff_t)-1);
  }

  static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
  {
  	struct inode *inode = dentry->d_inode;
  	struct page *page = NULL;
  	int error;

  	if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {

  		if (attr->ia_size < inode->i_size) {
  			/*
  			 * If truncating down to a partial page, then
  			 * if that page is already allocated, hold it
  			 * in memory until the truncation is over, so
  			 * truncate_partial_page cannnot miss it were
  			 * it assigned to swap.
  			 */
  			if (attr->ia_size & (PAGE_CACHE_SIZE-1)) {
  				(void) shmem_getpage(inode,
  					attr->ia_size>>PAGE_CACHE_SHIFT,
  						&page, SGP_READ, NULL);
  			}
  			/*
  			 * Reset SHMEM_PAGEIN flag so that shmem_truncate can
  			 * detect if any pages might have been added to cache
  			 * after truncate_inode_pages.  But we needn't bother
  			 * if it's being fully truncated to zero-length: the
  			 * nrpages check is efficient enough in that case.
  			 */
  			if (attr->ia_size) {
  				struct shmem_inode_info *info = SHMEM_I(inode);
  				spin_lock(&info->lock);
  				info->flags &= ~SHMEM_PAGEIN;
  				spin_unlock(&info->lock);
  			}
  		}
  	}
  
  	error = inode_change_ok(inode, attr);
  	if (!error)
  		error = inode_setattr(inode, attr);

  #ifdef CONFIG_TMPFS_POSIX_ACL
  	if (!error && (attr->ia_valid & ATTR_MODE))
  		error = generic_acl_chmod(inode, &shmem_acl_ops);
  #endif

  	if (page)
  		page_cache_release(page);
  	return error;
  }
  
  static void shmem_delete_inode(struct inode *inode)
  {
  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
  	struct shmem_inode_info *info = SHMEM_I(inode);
  
  	if (inode->i_op->truncate == shmem_truncate) {

  		truncate_inode_pages(inode->i_mapping, 0);

  		shmem_unacct_size(info->flags, inode->i_size);
  		inode->i_size = 0;
  		shmem_truncate(inode);
  		if (!list_empty(&info->swaplist)) {
  			spin_lock(&shmem_swaplist_lock);
  			list_del_init(&info->swaplist);
  			spin_unlock(&shmem_swaplist_lock);
  		}
  	}

  	BUG_ON(inode->i_blocks);
  	if (sbinfo->max_inodes) {

  		spin_lock(&sbinfo->stat_lock);
  		sbinfo->free_inodes++;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  	clear_inode(inode);
  }
  
  static inline int shmem_find_swp(swp_entry_t entry, swp_entry_t *dir, swp_entry_t *edir)
  {
  	swp_entry_t *ptr;
  
  	for (ptr = dir; ptr < edir; ptr++) {
  		if (ptr->val == entry.val)
  			return ptr - dir;
  	}
  	return -1;
  }
  
  static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, struct page *page)
  {
  	struct inode *inode;
  	unsigned long idx;
  	unsigned long size;
  	unsigned long limit;
  	unsigned long stage;
  	struct page **dir;
  	struct page *subdir;
  	swp_entry_t *ptr;
  	int offset;
  
  	idx = 0;
  	ptr = info->i_direct;
  	spin_lock(&info->lock);
  	limit = info->next_index;
  	size = limit;
  	if (size > SHMEM_NR_DIRECT)
  		size = SHMEM_NR_DIRECT;
  	offset = shmem_find_swp(entry, ptr, ptr+size);
  	if (offset >= 0) {
  		shmem_swp_balance_unmap();
  		goto found;
  	}
  	if (!info->i_indirect)
  		goto lost2;
  
  	dir = shmem_dir_map(info->i_indirect);
  	stage = SHMEM_NR_DIRECT + ENTRIES_PER_PAGEPAGE/2;
  
  	for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
  		if (unlikely(idx == stage)) {
  			shmem_dir_unmap(dir-1);
  			dir = shmem_dir_map(info->i_indirect) +
  			    ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
  			while (!*dir) {
  				dir++;
  				idx += ENTRIES_PER_PAGEPAGE;
  				if (idx >= limit)
  					goto lost1;
  			}
  			stage = idx + ENTRIES_PER_PAGEPAGE;
  			subdir = *dir;
  			shmem_dir_unmap(dir);
  			dir = shmem_dir_map(subdir);
  		}
  		subdir = *dir;

  		if (subdir && page_private(subdir)) {

  			ptr = shmem_swp_map(subdir);
  			size = limit - idx;
  			if (size > ENTRIES_PER_PAGE)
  				size = ENTRIES_PER_PAGE;
  			offset = shmem_find_swp(entry, ptr, ptr+size);
  			if (offset >= 0) {
  				shmem_dir_unmap(dir);
  				goto found;
  			}
  			shmem_swp_unmap(ptr);
  		}
  	}
  lost1:
  	shmem_dir_unmap(dir-1);
  lost2:
  	spin_unlock(&info->lock);
  	return 0;
  found:
  	idx += offset;
  	inode = &info->vfs_inode;
  	if (move_from_swap_cache(page, idx, inode->i_mapping) == 0) {
  		info->flags |= SHMEM_PAGEIN;
  		shmem_swp_set(info, ptr + offset, 0);
  	}
  	shmem_swp_unmap(ptr);
  	spin_unlock(&info->lock);
  	/*
  	 * Decrement swap count even when the entry is left behind:
  	 * try_to_unuse will skip over mms, then reincrement count.
  	 */
  	swap_free(entry);
  	return 1;
  }
  
  /*
   * shmem_unuse() search for an eventually swapped out shmem page.
   */
  int shmem_unuse(swp_entry_t entry, struct page *page)
  {
  	struct list_head *p, *next;
  	struct shmem_inode_info *info;
  	int found = 0;
  
  	spin_lock(&shmem_swaplist_lock);
  	list_for_each_safe(p, next, &shmem_swaplist) {
  		info = list_entry(p, struct shmem_inode_info, swaplist);
  		if (!info->swapped)
  			list_del_init(&info->swaplist);
  		else if (shmem_unuse_inode(info, entry, page)) {
  			/* move head to start search for next from here */
  			list_move_tail(&shmem_swaplist, &info->swaplist);
  			found = 1;
  			break;
  		}
  	}
  	spin_unlock(&shmem_swaplist_lock);
  	return found;
  }
  
  /*
   * Move the page from the page cache to the swap cache.
   */
  static int shmem_writepage(struct page *page, struct writeback_control *wbc)
  {
  	struct shmem_inode_info *info;
  	swp_entry_t *entry, swap;
  	struct address_space *mapping;
  	unsigned long index;
  	struct inode *inode;
  
  	BUG_ON(!PageLocked(page));
  	BUG_ON(page_mapped(page));
  
  	mapping = page->mapping;
  	index = page->index;
  	inode = mapping->host;
  	info = SHMEM_I(inode);
  	if (info->flags & VM_LOCKED)
  		goto redirty;
  	swap = get_swap_page();
  	if (!swap.val)
  		goto redirty;
  
  	spin_lock(&info->lock);
  	shmem_recalc_inode(inode);
  	if (index >= info->next_index) {
  		BUG_ON(!(info->flags & SHMEM_TRUNCATE));
  		goto unlock;
  	}
  	entry = shmem_swp_entry(info, index, NULL);
  	BUG_ON(!entry);
  	BUG_ON(entry->val);
  
  	if (move_to_swap_cache(page, swap) == 0) {
  		shmem_swp_set(info, entry, swap.val);
  		shmem_swp_unmap(entry);
  		spin_unlock(&info->lock);
  		if (list_empty(&info->swaplist)) {
  			spin_lock(&shmem_swaplist_lock);
  			/* move instead of add in case we're racing */
  			list_move_tail(&info->swaplist, &shmem_swaplist);
  			spin_unlock(&shmem_swaplist_lock);
  		}
  		unlock_page(page);
  		return 0;
  	}
  
  	shmem_swp_unmap(entry);
  unlock:
  	spin_unlock(&info->lock);
  	swap_free(swap);
  redirty:
  	set_page_dirty(page);

  	return AOP_WRITEPAGE_ACTIVATE;	/* Return with the page locked */

  }
  
  #ifdef CONFIG_NUMA

  static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)

  {
  	char *nodelist = strchr(value, ':');
  	int err = 1;
  
  	if (nodelist) {
  		/* NUL-terminate policy string */
  		*nodelist++ = '\0';
  		if (nodelist_parse(nodelist, *policy_nodes))
  			goto out;

  		if (!nodes_subset(*policy_nodes, node_online_map))
  			goto out;

  	}
  	if (!strcmp(value, "default")) {
  		*policy = MPOL_DEFAULT;
  		/* Don't allow a nodelist */
  		if (!nodelist)
  			err = 0;
  	} else if (!strcmp(value, "prefer")) {
  		*policy = MPOL_PREFERRED;
  		/* Insist on a nodelist of one node only */
  		if (nodelist) {
  			char *rest = nodelist;
  			while (isdigit(*rest))
  				rest++;
  			if (!*rest)
  				err = 0;
  		}
  	} else if (!strcmp(value, "bind")) {
  		*policy = MPOL_BIND;
  		/* Insist on a nodelist */
  		if (nodelist)
  			err = 0;
  	} else if (!strcmp(value, "interleave")) {
  		*policy = MPOL_INTERLEAVE;
  		/* Default to nodes online if no nodelist */
  		if (!nodelist)
  			*policy_nodes = node_online_map;
  		err = 0;
  	}
  out:
  	/* Restore string for error message */
  	if (nodelist)
  		*--nodelist = ':';
  	return err;
  }

  static struct page *shmem_swapin_async(struct shared_policy *p,
  				       swp_entry_t entry, unsigned long idx)
  {
  	struct page *page;
  	struct vm_area_struct pvma;
  
  	/* Create a pseudo vma that just contains the policy */
  	memset(&pvma, 0, sizeof(struct vm_area_struct));
  	pvma.vm_end = PAGE_SIZE;
  	pvma.vm_pgoff = idx;
  	pvma.vm_policy = mpol_shared_policy_lookup(p, idx);
  	page = read_swap_cache_async(entry, &pvma, 0);
  	mpol_free(pvma.vm_policy);
  	return page;
  }
  
  struct page *shmem_swapin(struct shmem_inode_info *info, swp_entry_t entry,
  			  unsigned long idx)
  {
  	struct shared_policy *p = &info->policy;
  	int i, num;
  	struct page *page;
  	unsigned long offset;
  
  	num = valid_swaphandles(entry, &offset);
  	for (i = 0; i < num; offset++, i++) {
  		page = shmem_swapin_async(p,
  				swp_entry(swp_type(entry), offset), idx);
  		if (!page)
  			break;
  		page_cache_release(page);
  	}
  	lru_add_drain();	/* Push any new pages onto the LRU now */
  	return shmem_swapin_async(p, entry, idx);
  }
  
  static struct page *

  shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info,

  		 unsigned long idx)
  {
  	struct vm_area_struct pvma;
  	struct page *page;
  
  	memset(&pvma, 0, sizeof(struct vm_area_struct));
  	pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, idx);
  	pvma.vm_pgoff = idx;
  	pvma.vm_end = PAGE_SIZE;
  	page = alloc_page_vma(gfp | __GFP_ZERO, &pvma, 0);
  	mpol_free(pvma.vm_policy);
  	return page;
  }
  #else

  static inline int shmem_parse_mpol(char *value, int *policy, nodemask_t *policy_nodes)
  {
  	return 1;
  }

  static inline struct page *
  shmem_swapin(struct shmem_inode_info *info,swp_entry_t entry,unsigned long idx)
  {
  	swapin_readahead(entry, 0, NULL);
  	return read_swap_cache_async(entry, NULL, 0);
  }
  
  static inline struct page *

  shmem_alloc_page(gfp_t gfp,struct shmem_inode_info *info, unsigned long idx)

  {
  	return alloc_page(gfp | __GFP_ZERO);
  }
  #endif
  
  /*
   * shmem_getpage - either get the page from swap or allocate a new one
   *
   * If we allocate a new one we do not mark it dirty. That's up to the
   * vm. If we swap it in we mark it dirty since we also free the swap
   * entry since a page cannot live in both the swap and page cache
   */
  static int shmem_getpage(struct inode *inode, unsigned long idx,
  			struct page **pagep, enum sgp_type sgp, int *type)
  {
  	struct address_space *mapping = inode->i_mapping;
  	struct shmem_inode_info *info = SHMEM_I(inode);
  	struct shmem_sb_info *sbinfo;
  	struct page *filepage = *pagep;
  	struct page *swappage;
  	swp_entry_t *entry;
  	swp_entry_t swap;
  	int error;
  
  	if (idx >= SHMEM_MAX_INDEX)
  		return -EFBIG;

  
  	if (type)

  		*type = 0;

  	/*
  	 * Normally, filepage is NULL on entry, and either found
  	 * uptodate immediately, or allocated and zeroed, or read
  	 * in under swappage, which is then assigned to filepage.

  	 * But shmem_readpage and shmem_write_begin pass in a locked

  	 * filepage, which may be found not uptodate by other callers
  	 * too, and may need to be copied from the swappage read in.

  	 */
  repeat:
  	if (!filepage)
  		filepage = find_lock_page(mapping, idx);
  	if (filepage && PageUptodate(filepage))
  		goto done;
  	error = 0;
  	if (sgp == SGP_QUICK)
  		goto failed;
  
  	spin_lock(&info->lock);
  	shmem_recalc_inode(inode);
  	entry = shmem_swp_alloc(info, idx, sgp);
  	if (IS_ERR(entry)) {
  		spin_unlock(&info->lock);
  		error = PTR_ERR(entry);
  		goto failed;
  	}
  	swap = *entry;
  
  	if (swap.val) {
  		/* Look it up and read it in.. */
  		swappage = lookup_swap_cache(swap);
  		if (!swappage) {
  			shmem_swp_unmap(entry);

  			/* here we actually do the io */

  			if (type && !(*type & VM_FAULT_MAJOR)) {

  				__count_vm_event(PGMAJFAULT);

  				*type |= VM_FAULT_MAJOR;

  			}

  			spin_unlock(&info->lock);

  			swappage = shmem_swapin(info, swap, idx);
  			if (!swappage) {
  				spin_lock(&info->lock);
  				entry = shmem_swp_alloc(info, idx, sgp);
  				if (IS_ERR(entry))
  					error = PTR_ERR(entry);
  				else {
  					if (entry->val == swap.val)
  						error = -ENOMEM;
  					shmem_swp_unmap(entry);
  				}
  				spin_unlock(&info->lock);
  				if (error)
  					goto failed;
  				goto repeat;
  			}
  			wait_on_page_locked(swappage);
  			page_cache_release(swappage);
  			goto repeat;
  		}
  
  		/* We have to do this with page locked to prevent races */
  		if (TestSetPageLocked(swappage)) {
  			shmem_swp_unmap(entry);
  			spin_unlock(&info->lock);
  			wait_on_page_locked(swappage);
  			page_cache_release(swappage);
  			goto repeat;
  		}
  		if (PageWriteback(swappage)) {
  			shmem_swp_unmap(entry);
  			spin_unlock(&info->lock);
  			wait_on_page_writeback(swappage);
  			unlock_page(swappage);
  			page_cache_release(swappage);
  			goto repeat;
  		}
  		if (!PageUptodate(swappage)) {
  			shmem_swp_unmap(entry);
  			spin_unlock(&info->lock);
  			unlock_page(swappage);
  			page_cache_release(swappage);
  			error = -EIO;
  			goto failed;
  		}
  
  		if (filepage) {
  			shmem_swp_set(info, entry, 0);
  			shmem_swp_unmap(entry);
  			delete_from_swap_cache(swappage);
  			spin_unlock(&info->lock);
  			copy_highpage(filepage, swappage);
  			unlock_page(swappage);
  			page_cache_release(swappage);
  			flush_dcache_page(filepage);
  			SetPageUptodate(filepage);
  			set_page_dirty(filepage);
  			swap_free(swap);
  		} else if (!(error = move_from_swap_cache(
  				swappage, idx, mapping))) {
  			info->flags |= SHMEM_PAGEIN;
  			shmem_swp_set(info, entry, 0);
  			shmem_swp_unmap(entry);
  			spin_unlock(&info->lock);
  			filepage = swappage;
  			swap_free(swap);
  		} else {
  			shmem_swp_unmap(entry);
  			spin_unlock(&info->lock);
  			unlock_page(swappage);
  			page_cache_release(swappage);
  			if (error == -ENOMEM) {
  				/* let kswapd refresh zone for GFP_ATOMICs */

  				congestion_wait(WRITE, HZ/50);

  			}
  			goto repeat;
  		}
  	} else if (sgp == SGP_READ && !filepage) {
  		shmem_swp_unmap(entry);
  		filepage = find_get_page(mapping, idx);
  		if (filepage &&
  		    (!PageUptodate(filepage) || TestSetPageLocked(filepage))) {
  			spin_unlock(&info->lock);
  			wait_on_page_locked(filepage);
  			page_cache_release(filepage);
  			filepage = NULL;
  			goto repeat;
  		}
  		spin_unlock(&info->lock);
  	} else {
  		shmem_swp_unmap(entry);
  		sbinfo = SHMEM_SB(inode->i_sb);

  		if (sbinfo->max_blocks) {

  			spin_lock(&sbinfo->stat_lock);
  			if (sbinfo->free_blocks == 0 ||
  			    shmem_acct_block(info->flags)) {
  				spin_unlock(&sbinfo->stat_lock);
  				spin_unlock(&info->lock);
  				error = -ENOSPC;
  				goto failed;
  			}
  			sbinfo->free_blocks--;
  			inode->i_blocks += BLOCKS_PER_PAGE;
  			spin_unlock(&sbinfo->stat_lock);
  		} else if (shmem_acct_block(info->flags)) {
  			spin_unlock(&info->lock);
  			error = -ENOSPC;
  			goto failed;
  		}
  
  		if (!filepage) {
  			spin_unlock(&info->lock);
  			filepage = shmem_alloc_page(mapping_gfp_mask(mapping),
  						    info,
  						    idx);
  			if (!filepage) {
  				shmem_unacct_blocks(info->flags, 1);
  				shmem_free_blocks(inode, 1);
  				error = -ENOMEM;
  				goto failed;
  			}
  
  			spin_lock(&info->lock);
  			entry = shmem_swp_alloc(info, idx, sgp);
  			if (IS_ERR(entry))
  				error = PTR_ERR(entry);
  			else {
  				swap = *entry;
  				shmem_swp_unmap(entry);
  			}
  			if (error || swap.val || 0 != add_to_page_cache_lru(
  					filepage, mapping, idx, GFP_ATOMIC)) {
  				spin_unlock(&info->lock);
  				page_cache_release(filepage);
  				shmem_unacct_blocks(info->flags, 1);
  				shmem_free_blocks(inode, 1);
  				filepage = NULL;
  				if (error)
  					goto failed;
  				goto repeat;
  			}
  			info->flags |= SHMEM_PAGEIN;
  		}
  
  		info->alloced++;
  		spin_unlock(&info->lock);
  		flush_dcache_page(filepage);
  		SetPageUptodate(filepage);
  	}
  done:
  	if (*pagep != filepage) {

  		*pagep = filepage;

  		if (sgp != SGP_FAULT)

  			unlock_page(filepage);

  	}
  	return 0;
  
  failed:
  	if (*pagep != filepage) {
  		unlock_page(filepage);
  		page_cache_release(filepage);
  	}
  	return error;
  }

  static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

  {

  	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;

  	int error;

  	int ret;

  	if (((loff_t)vmf->pgoff << PAGE_CACHE_SHIFT) >= i_size_read(inode))
  		return VM_FAULT_SIGBUS;

  	error = shmem_getpage(inode, vmf->pgoff, &vmf->page, SGP_FAULT, &ret);
  	if (error)
  		return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);

  	mark_page_accessed(vmf->page);

  	return ret | VM_FAULT_LOCKED;

  }

  #ifdef CONFIG_NUMA
  int shmem_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
  {

  	struct inode *i = vma->vm_file->f_path.dentry->d_inode;

  	return mpol_set_shared_policy(&SHMEM_I(i)->policy, vma, new);
  }
  
  struct mempolicy *
  shmem_get_policy(struct vm_area_struct *vma, unsigned long addr)
  {

  	struct inode *i = vma->vm_file->f_path.dentry->d_inode;

  	unsigned long idx;
  
  	idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
  	return mpol_shared_policy_lookup(&SHMEM_I(i)->policy, idx);
  }
  #endif
  
  int shmem_lock(struct file *file, int lock, struct user_struct *user)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	struct shmem_inode_info *info = SHMEM_I(inode);
  	int retval = -ENOMEM;
  
  	spin_lock(&info->lock);
  	if (lock && !(info->flags & VM_LOCKED)) {
  		if (!user_shm_lock(inode->i_size, user))
  			goto out_nomem;
  		info->flags |= VM_LOCKED;
  	}
  	if (!lock && (info->flags & VM_LOCKED) && user) {
  		user_shm_unlock(inode->i_size, user);
  		info->flags &= ~VM_LOCKED;
  	}
  	retval = 0;
  out_nomem:
  	spin_unlock(&info->lock);
  	return retval;
  }

  static int shmem_mmap(struct file *file, struct vm_area_struct *vma)

  {
  	file_accessed(file);
  	vma->vm_ops = &shmem_vm_ops;

  	vma->vm_flags |= VM_CAN_NONLINEAR;

  	return 0;
  }
  
  static struct inode *
  shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
  {
  	struct inode *inode;
  	struct shmem_inode_info *info;
  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

  	if (sbinfo->max_inodes) {

  		spin_lock(&sbinfo->stat_lock);
  		if (!sbinfo->free_inodes) {
  			spin_unlock(&sbinfo->stat_lock);
  			return NULL;
  		}
  		sbinfo->free_inodes--;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  
  	inode = new_inode(sb);
  	if (inode) {
  		inode->i_mode = mode;
  		inode->i_uid = current->fsuid;
  		inode->i_gid = current->fsgid;

  		inode->i_blocks = 0;
  		inode->i_mapping->a_ops = &shmem_aops;
  		inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

  		inode->i_generation = get_seconds();

  		info = SHMEM_I(inode);
  		memset(info, 0, (char *)inode - (char *)info);
  		spin_lock_init(&info->lock);
  		INIT_LIST_HEAD(&info->swaplist);
  
  		switch (mode & S_IFMT) {
  		default:

  			inode->i_op = &shmem_special_inode_operations;

  			init_special_inode(inode, mode, dev);
  			break;
  		case S_IFREG:
  			inode->i_op = &shmem_inode_operations;
  			inode->i_fop = &shmem_file_operations;

  			mpol_shared_policy_init(&info->policy, sbinfo->policy,
  							&sbinfo->policy_nodes);

  			break;
  		case S_IFDIR:

  			inc_nlink(inode);

  			/* Some things misbehave if size == 0 on a directory */
  			inode->i_size = 2 * BOGO_DIRENT_SIZE;
  			inode->i_op = &shmem_dir_inode_operations;
  			inode->i_fop = &simple_dir_operations;
  			break;
  		case S_IFLNK:
  			/*
  			 * Must not load anything in the rbtree,
  			 * mpol_free_shared_policy will not be called.
  			 */

  			mpol_shared_policy_init(&info->policy, MPOL_DEFAULT,
  						NULL);

  			break;
  		}

  	} else if (sbinfo->max_inodes) {

  		spin_lock(&sbinfo->stat_lock);
  		sbinfo->free_inodes++;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  	return inode;
  }
  
  #ifdef CONFIG_TMPFS

  static const struct inode_operations shmem_symlink_inode_operations;
  static const struct inode_operations shmem_symlink_inline_operations;

  
  /*

   * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;

   * but providing them allows a tmpfs file to be used for splice, sendfile, and
   * below the loop driver, in the generic fashion that many filesystems support.

   */

  static int shmem_readpage(struct file *file, struct page *page)
  {
  	struct inode *inode = page->mapping->host;
  	int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
  	unlock_page(page);
  	return error;
  }

  static int

  shmem_write_begin(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned flags,
  			struct page **pagep, void **fsdata)

  {

  	struct inode *inode = mapping->host;
  	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
  	*pagep = NULL;
  	return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
  }
  
  static int
  shmem_write_end(struct file *file, struct address_space *mapping,
  			loff_t pos, unsigned len, unsigned copied,
  			struct page *page, void *fsdata)
  {
  	struct inode *inode = mapping->host;
  
  	set_page_dirty(page);
  	page_cache_release(page);
  
  	if (pos+copied > inode->i_size)
  		i_size_write(inode, pos+copied);
  
  	return copied;

  }
  
  static ssize_t
  shmem_file_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
  {

  	struct inode	*inode = file->f_path.dentry->d_inode;

  	loff_t		pos;
  	unsigned long	written;
  	ssize_t		err;
  
  	if ((ssize_t) count < 0)
  		return -EINVAL;
  
  	if (!access_ok(VERIFY_READ, buf, count))
  		return -EFAULT;

  	mutex_lock(&inode->i_mutex);

  
  	pos = *ppos;
  	written = 0;
  
  	err = generic_write_checks(file, &pos, &count, 0);
  	if (err || !count)
  		goto out;

  	err = remove_suid(file->f_path.dentry);

  	if (err)
  		goto out;
  
  	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
  
  	do {
  		struct page *page = NULL;
  		unsigned long bytes, index, offset;
  		char *kaddr;
  		int left;
  
  		offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
  		index = pos >> PAGE_CACHE_SHIFT;
  		bytes = PAGE_CACHE_SIZE - offset;
  		if (bytes > count)
  			bytes = count;
  
  		/*
  		 * We don't hold page lock across copy from user -
  		 * what would it guard against? - so no deadlock here.
  		 * But it still may be a good idea to prefault below.
  		 */
  
  		err = shmem_getpage(inode, index, &page, SGP_WRITE, NULL);
  		if (err)
  			break;
  
  		left = bytes;
  		if (PageHighMem(page)) {
  			volatile unsigned char dummy;
  			__get_user(dummy, buf);
  			__get_user(dummy, buf + bytes - 1);
  
  			kaddr = kmap_atomic(page, KM_USER0);
  			left = __copy_from_user_inatomic(kaddr + offset,
  							buf, bytes);
  			kunmap_atomic(kaddr, KM_USER0);
  		}
  		if (left) {
  			kaddr = kmap(page);
  			left = __copy_from_user(kaddr + offset, buf, bytes);
  			kunmap(page);
  		}
  
  		written += bytes;
  		count -= bytes;
  		pos += bytes;
  		buf += bytes;
  		if (pos > inode->i_size)
  			i_size_write(inode, pos);
  
  		flush_dcache_page(page);
  		set_page_dirty(page);
  		mark_page_accessed(page);
  		page_cache_release(page);
  
  		if (left) {
  			pos -= left;
  			written -= left;
  			err = -EFAULT;
  			break;
  		}
  
  		/*
  		 * Our dirty pages are not counted in nr_dirty,
  		 * and we do not attempt to balance dirty pages.
  		 */
  
  		cond_resched();
  	} while (count);
  
  	*ppos = pos;
  	if (written)
  		err = written;
  out:

  	mutex_unlock(&inode->i_mutex);

  	return err;
  }
  
  static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
  {

  	struct inode *inode = filp->f_path.dentry->d_inode;

  	struct address_space *mapping = inode->i_mapping;
  	unsigned long index, offset;
  
  	index = *ppos >> PAGE_CACHE_SHIFT;
  	offset = *ppos & ~PAGE_CACHE_MASK;
  
  	for (;;) {
  		struct page *page = NULL;
  		unsigned long end_index, nr, ret;
  		loff_t i_size = i_size_read(inode);
  
  		end_index = i_size >> PAGE_CACHE_SHIFT;
  		if (index > end_index)
  			break;
  		if (index == end_index) {
  			nr = i_size & ~PAGE_CACHE_MASK;
  			if (nr <= offset)
  				break;
  		}
  
  		desc->error = shmem_getpage(inode, index, &page, SGP_READ, NULL);
  		if (desc->error) {
  			if (desc->error == -EINVAL)
  				desc->error = 0;
  			break;
  		}
  
  		/*
  		 * We must evaluate after, since reads (unlike writes)

  		 * are called without i_mutex protection against truncate

  		 */
  		nr = PAGE_CACHE_SIZE;
  		i_size = i_size_read(inode);
  		end_index = i_size >> PAGE_CACHE_SHIFT;
  		if (index == end_index) {
  			nr = i_size & ~PAGE_CACHE_MASK;
  			if (nr <= offset) {
  				if (page)
  					page_cache_release(page);
  				break;
  			}
  		}
  		nr -= offset;
  
  		if (page) {
  			/*
  			 * If users can be writing to this page using arbitrary
  			 * virtual addresses, take care about potential aliasing
  			 * before reading the page on the kernel side.
  			 */
  			if (mapping_writably_mapped(mapping))
  				flush_dcache_page(page);
  			/*
  			 * Mark the page accessed if we read the beginning.
  			 */
  			if (!offset)
  				mark_page_accessed(page);

  		} else {

  			page = ZERO_PAGE(0);

  			page_cache_get(page);
  		}

  
  		/*
  		 * Ok, we have the page, and it's up-to-date, so
  		 * now we can copy it to user space...
  		 *
  		 * The actor routine returns how many bytes were actually used..
  		 * NOTE! This may not be the same as how much of a user buffer
  		 * we filled up (we may be padding etc), so we can only update
  		 * "pos" here (the actor routine has to update the user buffer
  		 * pointers and the remaining count).
  		 */
  		ret = actor(desc, page, offset, nr);
  		offset += ret;
  		index += offset >> PAGE_CACHE_SHIFT;
  		offset &= ~PAGE_CACHE_MASK;
  
  		page_cache_release(page);
  		if (ret != nr || !desc->count)
  			break;
  
  		cond_resched();
  	}
  
  	*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
  	file_accessed(filp);
  }
  
  static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
  {
  	read_descriptor_t desc;
  
  	if ((ssize_t) count < 0)
  		return -EINVAL;
  	if (!access_ok(VERIFY_WRITE, buf, count))
  		return -EFAULT;
  	if (!count)
  		return 0;
  
  	desc.written = 0;
  	desc.count = count;
  	desc.arg.buf = buf;
  	desc.error = 0;
  
  	do_shmem_file_read(filp, ppos, &desc, file_read_actor);
  	if (desc.written)
  		return desc.written;
  	return desc.error;
  }

  static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)

  {

  	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);

  
  	buf->f_type = TMPFS_MAGIC;
  	buf->f_bsize = PAGE_CACHE_SIZE;
  	buf->f_namelen = NAME_MAX;

  	spin_lock(&sbinfo->stat_lock);
  	if (sbinfo->max_blocks) {

  		buf->f_blocks = sbinfo->max_blocks;
  		buf->f_bavail = buf->f_bfree = sbinfo->free_blocks;

  	}
  	if (sbinfo->max_inodes) {

  		buf->f_files = sbinfo->max_inodes;
  		buf->f_ffree = sbinfo->free_inodes;

  	}
  	/* else leave those fields 0 like simple_statfs */

  	spin_unlock(&sbinfo->stat_lock);

  	return 0;
  }
  
  /*
   * File creation. Allocate an inode, and we're done..
   */
  static int
  shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
  {
  	struct inode *inode = shmem_get_inode(dir->i_sb, mode, dev);
  	int error = -ENOSPC;
  
  	if (inode) {

  		error = security_inode_init_security(inode, dir, NULL, NULL,
  						     NULL);
  		if (error) {
  			if (error != -EOPNOTSUPP) {
  				iput(inode);
  				return error;
  			}

  		}
  		error = shmem_acl_init(inode, dir);
  		if (error) {
  			iput(inode);
  			return error;

  		}

  		if (dir->i_mode & S_ISGID) {
  			inode->i_gid = dir->i_gid;
  			if (S_ISDIR(mode))
  				inode->i_mode |= S_ISGID;
  		}
  		dir->i_size += BOGO_DIRENT_SIZE;
  		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
  		d_instantiate(dentry, inode);
  		dget(dentry); /* Extra count - pin the dentry in core */

  	}
  	return error;
  }
  
  static int shmem_mkdir(struct inode *dir, struct dentry *dentry, int mode)
  {
  	int error;
  
  	if ((error = shmem_mknod(dir, dentry, mode | S_IFDIR, 0)))
  		return error;

  	inc_nlink(dir);

  	return 0;
  }
  
  static int shmem_create(struct inode *dir, struct dentry *dentry, int mode,
  		struct nameidata *nd)
  {
  	return shmem_mknod(dir, dentry, mode | S_IFREG, 0);
  }
  
  /*
   * Link a file..
   */
  static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
  {
  	struct inode *inode = old_dentry->d_inode;
  	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
  
  	/*
  	 * No ordinary (disk based) filesystem counts links as inodes;
  	 * but each new link needs a new dentry, pinning lowmem, and
  	 * tmpfs dentries cannot be pruned until they are unlinked.
  	 */

  	if (sbinfo->max_inodes) {

  		spin_lock(&sbinfo->stat_lock);
  		if (!sbinfo->free_inodes) {
  			spin_unlock(&sbinfo->stat_lock);
  			return -ENOSPC;
  		}
  		sbinfo->free_inodes--;
  		spin_unlock(&sbinfo->stat_lock);
  	}
  
  	dir->i_size += BOGO_DIRENT_SIZE;
  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

  	inc_nlink(inode);

  	atomic_inc(&inode->i_count);	/* New dentry reference */
  	dget(dentry);		/* Extra pinning count for the created dentry */
  	d_instantiate(dentry, inode);
  	return 0;
  }
  
  static int shmem_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct inode *inode = dentry->d_inode;
  
  	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
  		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);

  		if (sbinfo->max_inodes) {

  			spin_lock(&sbinfo->stat_lock);
  			sbinfo->free_inodes++;
  			spin_unlock(&sbinfo->stat_lock);
  		}
  	}
  
  	dir->i_size -= BOGO_DIRENT_SIZE;
  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

  	drop_nlink(inode);

  	dput(dentry);	/* Undo the count from "create" - this does all the work */
  	return 0;
  }
  
  static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
  {
  	if (!simple_empty(dentry))
  		return -ENOTEMPTY;

  	drop_nlink(dentry->d_inode);
  	drop_nlink(dir);

  	return shmem_unlink(dir, dentry);
  }
  
  /*
   * The VFS layer already does all the dentry stuff for rename,
   * we just have to decrement the usage count for the target if
   * it exists so that the VFS layer correctly free's it when it
   * gets overwritten.
   */
  static int shmem_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
  {
  	struct inode *inode = old_dentry->d_inode;
  	int they_are_dirs = S_ISDIR(inode->i_mode);
  
  	if (!simple_empty(new_dentry))
  		return -ENOTEMPTY;
  
  	if (new_dentry->d_inode) {
  		(void) shmem_unlink(new_dir, new_dentry);
  		if (they_are_dirs)

  			drop_nlink(old_dir);

  	} else if (they_are_dirs) {

  		drop_nlink(old_dir);

  		inc_nlink(new_dir);

  	}
  
  	old_dir->i_size -= BOGO_DIRENT_SIZE;
  	new_dir->i_size += BOGO_DIRENT_SIZE;
  	old_dir->i_ctime = old_dir->i_mtime =
  	new_dir->i_ctime = new_dir->i_mtime =
  	inode->i_ctime = CURRENT_TIME;
  	return 0;
  }
  
  static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
  {
  	int error;
  	int len;
  	struct inode *inode;
  	struct page *page = NULL;
  	char *kaddr;
  	struct shmem_inode_info *info;
  
  	len = strlen(symname) + 1;
  	if (len > PAGE_CACHE_SIZE)
  		return -ENAMETOOLONG;
  
  	inode = shmem_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
  	if (!inode)
  		return -ENOSPC;

  	error = security_inode_init_security(inode, dir, NULL, NULL,
  					     NULL);
  	if (error) {
  		if (error != -EOPNOTSUPP) {
  			iput(inode);
  			return error;
  		}
  		error = 0;
  	}

  	info = SHMEM_I(inode);
  	inode->i_size = len-1;
  	if (len <= (char *)inode - (char *)info) {
  		/* do it inline */
  		memcpy(info, symname, len);
  		inode->i_op = &shmem_symlink_inline_operations;
  	} else {
  		error = shmem_getpage(inode, 0, &page, SGP_WRITE, NULL);
  		if (error) {
  			iput(inode);
  			return error;
  		}
  		inode->i_op = &shmem_symlink_inode_operations;
  		kaddr = kmap_atomic(page, KM_USER0);
  		memcpy(kaddr, symname, len);
  		kunmap_atomic(kaddr, KM_USER0);
  		set_page_dirty(page);
  		page_cache_release(page);
  	}
  	if (dir->i_mode & S_ISGID)
  		inode->i_gid = dir->i_gid;
  	dir->i_size += BOGO_DIRENT_SIZE;
  	dir->i_ctime = dir->i_mtime = CURRENT_TIME;
  	d_instantiate(dentry, inode);
  	dget(dentry);
  	return 0;
  }

  static void *shmem_follow_link_inline(struct dentry *dentry, struct nameidata *nd)

  {
  	nd_set_link(nd, (char *)SHMEM_I(dentry->d_inode));

  	return NULL;

  }

  static void *shmem_follow_link(struct dentry *dentry, struct nameidata *nd)

  {
  	struct page *page = NULL;
  	int res = shmem_getpage(dentry->d_inode, 0, &page, SGP_READ, NULL);
  	nd_set_link(nd, res ? ERR_PTR(res) : kmap(page));

  	return page;

  }

  static void shmem_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)

  {
  	if (!IS_ERR(nd_get_link(nd))) {

  		struct page *page = cookie;

  		kunmap(page);
  		mark_page_accessed(page);
  		page_cache_release(page);

  	}
  }

  static const struct inode_operations shmem_symlink_inline_operations = {

  	.readlink	= generic_readlink,
  	.follow_link	= shmem_follow_link_inline,

  };

  static const struct inode_operations shmem_symlink_inode_operations = {

  	.truncate	= shmem_truncate,
  	.readlink	= generic_readlink,
  	.follow_link	= shmem_follow_link,
  	.put_link	= shmem_put_link,

  };

  #ifdef CONFIG_TMPFS_POSIX_ACL
  /**
   * Superblocks without xattr inode operations will get security.* xattr
   * support from the VFS "for free". As soon as we have any other xattrs
   * like ACLs, we also need to implement the security.* handlers at
   * filesystem level, though.
   */
  
  static size_t shmem_xattr_security_list(struct inode *inode, char *list,
  					size_t list_len, const char *name,
  					size_t name_len)
  {
  	return security_inode_listsecurity(inode, list, list_len);
  }
  
  static int shmem_xattr_security_get(struct inode *inode, const char *name,
  				    void *buffer, size_t size)
  {
  	if (strcmp(name, "") == 0)
  		return -EINVAL;
  	return security_inode_getsecurity(inode, name, buffer, size,
  					  -EOPNOTSUPP);
  }
  
  static int shmem_xattr_security_set(struct inode *inode, const char *name,
  				    const void *value, size_t size, int flags)
  {
  	if (strcmp(name, "") == 0)
  		return -EINVAL;
  	return security_inode_setsecurity(inode, name, value, size, flags);
  }

  static struct xattr_handler shmem_xattr_security_handler = {

  	.prefix = XATTR_SECURITY_PREFIX,
  	.list   = shmem_xattr_security_list,
  	.get    = shmem_xattr_security_get,
  	.set    = shmem_xattr_security_set,
  };
  
  static struct xattr_handler *shmem_xattr_handlers[] = {
  	&shmem_xattr_acl_access_handler,
  	&shmem_xattr_acl_default_handler,
  	&shmem_xattr_security_handler,
  	NULL
  };
  #endif

  static struct dentry *shmem_get_parent(struct dentry *child)
  {
  	return ERR_PTR(-ESTALE);
  }
  
  static int shmem_match(struct inode *ino, void *vfh)
  {
  	__u32 *fh = vfh;
  	__u64 inum = fh[2];
  	inum = (inum << 32) | fh[1];
  	return ino->i_ino == inum && fh[0] == ino->i_generation;
  }
  
  static struct dentry *shmem_get_dentry(struct super_block *sb, void *vfh)
  {
  	struct dentry *de = NULL;
  	struct inode *inode;
  	__u32 *fh = vfh;
  	__u64 inum = fh[2];
  	inum = (inum << 32) | fh[1];
  
  	inode = ilookup5(sb, (unsigned long)(inum+fh[0]), shmem_match, vfh);
  	if (inode) {
  		de = d_find_alias(inode);
  		iput(inode);
  	}
  
  	return de? de: ERR_PTR(-ESTALE);
  }
  
  static struct dentry *shmem_decode_fh(struct super_block *sb, __u32 *fh,
  		int len, int type,
  		int (*acceptable)(void *context, struct dentry *de),
  		void *context)
  {
  	if (len < 3)
  		return ERR_PTR(-ESTALE);
  
  	return sb->s_export_op->find_exported_dentry(sb, fh, NULL, acceptable,
  							context);
  }
  
  static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
  				int connectable)
  {
  	struct inode *inode = dentry->d_inode;
  
  	if (*len < 3)
  		return 255;
  
  	if (hlist_unhashed(&inode->i_hash)) {
  		/* Unfortunately insert_inode_hash is not idempotent,
  		 * so as we hash inodes here rather than at creation
  		 * time, we need a lock to ensure we only try
  		 * to do it once
  		 */
  		static DEFINE_SPINLOCK(lock);
  		spin_lock(&lock);
  		if (hlist_unhashed(&inode->i_hash))
  			__insert_inode_hash(inode,
  					    inode->i_ino + inode->i_generation);
  		spin_unlock(&lock);
  	}
  
  	fh[0] = inode->i_generation;
  	fh[1] = inode->i_ino;
  	fh[2] = ((__u64)inode->i_ino) >> 32;
  
  	*len = 3;
  	return 1;
  }
  
  static struct export_operations shmem_export_ops = {
  	.get_parent     = shmem_get_parent,
  	.get_dentry     = shmem_get_dentry,
  	.encode_fh      = shmem_encode_fh,
  	.decode_fh      = shmem_decode_fh,
  };

  static int shmem_parse_options(char *options, int *mode, uid_t *uid,
  	gid_t *gid, unsigned long *blocks, unsigned long *inodes,
  	int *policy, nodemask_t *policy_nodes)

  {
  	char *this_char, *value, *rest;

  	while (options != NULL) {
  		this_char = options;
  		for (;;) {
  			/*
  			 * NUL-terminate this option: unfortunately,
  			 * mount options form a comma-separated list,
  			 * but mpol's nodelist may also contain commas.
  			 */
  			options = strchr(options, ',');
  			if (options == NULL)
  				break;
  			options++;
  			if (!isdigit(*options)) {
  				options[-1] = '\0';
  				break;
  			}
  		}

  		if (!*this_char)
  			continue;
  		if ((value = strchr(this_char,'=')) != NULL) {
  			*value++ = 0;
  		} else {
  			printk(KERN_ERR
  			    "tmpfs: No value for mount option '%s'
  ",
  			    this_char);
  			return 1;
  		}
  
  		if (!strcmp(this_char,"size")) {
  			unsigned long long size;
  			size = memparse(value,&rest);
  			if (*rest == '%') {
  				size <<= PAGE_SHIFT;
  				size *= totalram_pages;
  				do_div(size, 100);
  				rest++;
  			}
  			if (*rest)
  				goto bad_val;
  			*blocks = size >> PAGE_CACHE_SHIFT;
  		} else if (!strcmp(this_char,"nr_blocks")) {
  			*blocks = memparse(value,&rest);
  			if (*rest)
  				goto bad_val;
  		} else if (!strcmp(this_char,"nr_inodes")) {
  			*inodes = memparse(value,&rest);
  			if (*rest)
  				goto bad_val;
  		} else if (!strcmp(this_char,"mode")) {
  			if (!mode)
  				continue;
  			*mode = simple_strtoul(value,&rest,8);
  			if (*rest)
  				goto bad_val;
  		} else if (!strcmp(this_char,"uid")) {
  			if (!uid)
  				continue;
  			*uid = simple_strtoul(value,&rest,0);
  			if (*rest)
  				goto bad_val;
  		} else if (!strcmp(this_char,"gid")) {
  			if (!gid)
  				continue;
  			*gid = simple_strtoul(value,&rest,0);
  			if (*rest)
  				goto bad_val;

  		} else if (!strcmp(this_char,"mpol")) {

  			if (shmem_parse_mpol(value,policy,policy_nodes))

  				goto bad_val;

  		} else {
  			printk(KERN_ERR "tmpfs: Bad mount option %s
  ",
  			       this_char);
  			return 1;
  		}
  	}
  	return 0;
  
  bad_val:
  	printk(KERN_ERR "tmpfs: Bad value '%s' for mount option '%s'
  ",
  	       value, this_char);
  	return 1;
  
  }
  
  static int shmem_remount_fs(struct super_block *sb, int *flags, char *data)
  {
  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);

  	unsigned long max_blocks = sbinfo->max_blocks;
  	unsigned long max_inodes = sbinfo->max_inodes;

  	int policy = sbinfo->policy;
  	nodemask_t policy_nodes = sbinfo->policy_nodes;

  	unsigned long blocks;
  	unsigned long inodes;
  	int error = -EINVAL;

  	if (shmem_parse_options(data, NULL, NULL, NULL, &max_blocks,
  				&max_inodes, &policy, &policy_nodes))

  		return error;

  	spin_lock(&sbinfo->stat_lock);
  	blocks = sbinfo->max_blocks - sbinfo->free_blocks;
  	inodes = sbinfo->max_inodes - sbinfo->free_inodes;
  	if (max_blocks < blocks)
  		goto out;
  	if (max_inodes < inodes)
  		goto out;
  	/*
  	 * Those tests also disallow limited->unlimited while any are in
  	 * use, so i_blocks will always be zero when max_blocks is zero;
  	 * but we must separately disallow unlimited->limited, because
  	 * in that case we have no record of how much is already in use.
  	 */
  	if (max_blocks && !sbinfo->max_blocks)
  		goto out;
  	if (max_inodes && !sbinfo->max_inodes)
  		goto out;
  
  	error = 0;
  	sbinfo->max_blocks  = max_blocks;
  	sbinfo->free_blocks = max_blocks - blocks;
  	sbinfo->max_inodes  = max_inodes;
  	sbinfo->free_inodes = max_inodes - inodes;

  	sbinfo->policy = policy;
  	sbinfo->policy_nodes = policy_nodes;

  out:
  	spin_unlock(&sbinfo->stat_lock);
  	return error;

  }
  #endif
  
  static void shmem_put_super(struct super_block *sb)
  {
  	kfree(sb->s_fs_info);
  	sb->s_fs_info = NULL;
  }

  static int shmem_fill_super(struct super_block *sb,
  			    void *data, int silent)
  {
  	struct inode *inode;
  	struct dentry *root;
  	int mode   = S_IRWXUGO | S_ISVTX;
  	uid_t uid = current->fsuid;
  	gid_t gid = current->fsgid;
  	int err = -ENOMEM;

  	struct shmem_sb_info *sbinfo;

  	unsigned long blocks = 0;
  	unsigned long inodes = 0;

  	int policy = MPOL_DEFAULT;
  	nodemask_t policy_nodes = node_online_map;

  #ifdef CONFIG_TMPFS

  	/*
  	 * Per default we only allow half of the physical ram per
  	 * tmpfs instance, limiting inodes to one per page of lowmem;
  	 * but the internal instance is left unlimited.
  	 */
  	if (!(sb->s_flags & MS_NOUSER)) {
  		blocks = totalram_pages / 2;
  		inodes = totalram_pages - totalhigh_pages;
  		if (inodes > blocks)
  			inodes = blocks;

  		if (shmem_parse_options(data, &mode, &uid, &gid, &blocks,
  					&inodes, &policy, &policy_nodes))

  			return -EINVAL;
  	}

  	sb->s_export_op = &shmem_export_ops;

  #else
  	sb->s_flags |= MS_NOUSER;
  #endif

  	/* Round up to L1_CACHE_BYTES to resist false sharing */
  	sbinfo = kmalloc(max((int)sizeof(struct shmem_sb_info),
  				L1_CACHE_BYTES), GFP_KERNEL);
  	if (!sbinfo)
  		return -ENOMEM;
  
  	spin_lock_init(&sbinfo->stat_lock);
  	sbinfo->max_blocks = blocks;
  	sbinfo->free_blocks = blocks;
  	sbinfo->max_inodes = inodes;
  	sbinfo->free_inodes = inodes;

  	sbinfo->policy = policy;
  	sbinfo->policy_nodes = policy_nodes;

  
  	sb->s_fs_info = sbinfo;

  	sb->s_maxbytes = SHMEM_MAX_BYTES;
  	sb->s_blocksize = PAGE_CACHE_SIZE;
  	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
  	sb->s_magic = TMPFS_MAGIC;
  	sb->s_op = &shmem_ops;

  	sb->s_time_gran = 1;

  #ifdef CONFIG_TMPFS_POSIX_ACL
  	sb->s_xattr = shmem_xattr_handlers;
  	sb->s_flags |= MS_POSIXACL;
  #endif

  	inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
  	if (!inode)
  		goto failed;
  	inode->i_uid = uid;
  	inode->i_gid = gid;
  	root = d_alloc_root(inode);
  	if (!root)
  		goto failed_iput;
  	sb->s_root = root;
  	return 0;
  
  failed_iput:
  	iput(inode);
  failed:
  	shmem_put_super(sb);
  	return err;
  }

  static struct kmem_cache *shmem_inode_cachep;

  
  static struct inode *shmem_alloc_inode(struct super_block *sb)
  {
  	struct shmem_inode_info *p;

  	p = (struct shmem_inode_info *)kmem_cache_alloc(shmem_inode_cachep, GFP_KERNEL);

  	if (!p)
  		return NULL;
  	return &p->vfs_inode;
  }
  
  static void shmem_destroy_inode(struct inode *inode)
  {
  	if ((inode->i_mode & S_IFMT) == S_IFREG) {
  		/* only struct inode is valid if it's an inline symlink */
  		mpol_free_shared_policy(&SHMEM_I(inode)->policy);
  	}

  	shmem_acl_destroy_inode(inode);

  	kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
  }

  static void init_once(void *foo, struct kmem_cache *cachep,
  		      unsigned long flags)

  {
  	struct shmem_inode_info *p = (struct shmem_inode_info *) foo;

  	inode_init_once(&p->vfs_inode);

  #ifdef CONFIG_TMPFS_POSIX_ACL

  	p->i_acl = NULL;
  	p->i_default_acl = NULL;

  #endif

  }
  
  static int init_inodecache(void)
  {
  	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
  				sizeof(struct shmem_inode_info),

  				0, 0, init_once);

  	if (shmem_inode_cachep == NULL)
  		return -ENOMEM;
  	return 0;
  }
  
  static void destroy_inodecache(void)
  {

  	kmem_cache_destroy(shmem_inode_cachep);

  }

  static const struct address_space_operations shmem_aops = {

  	.writepage	= shmem_writepage,

  	.set_page_dirty	= __set_page_dirty_no_writeback,

  #ifdef CONFIG_TMPFS

  	.readpage	= shmem_readpage,

  	.write_begin	= shmem_write_begin,
  	.write_end	= shmem_write_end,

  #endif

  	.migratepage	= migrate_page,

  };

  static const struct file_operations shmem_file_operations = {

  	.mmap		= shmem_mmap,
  #ifdef CONFIG_TMPFS
  	.llseek		= generic_file_llseek,
  	.read		= shmem_file_read,
  	.write		= shmem_file_write,
  	.fsync		= simple_sync_file,

  	.splice_read	= generic_file_splice_read,
  	.splice_write	= generic_file_splice_write,

  #endif
  };

  static const struct inode_operations shmem_inode_operations = {

  	.truncate	= shmem_truncate,
  	.setattr	= shmem_notify_change,

  	.truncate_range	= shmem_truncate_range,

  #ifdef CONFIG_TMPFS_POSIX_ACL
  	.setxattr	= generic_setxattr,
  	.getxattr	= generic_getxattr,
  	.listxattr	= generic_listxattr,
  	.removexattr	= generic_removexattr,
  	.permission	= shmem_permission,
  #endif

  };

  static const struct inode_operations shmem_dir_inode_operations = {

  #ifdef CONFIG_TMPFS
  	.create		= shmem_create,
  	.lookup		= simple_lookup,
  	.link		= shmem_link,
  	.unlink		= shmem_unlink,
  	.symlink	= shmem_symlink,
  	.mkdir		= shmem_mkdir,
  	.rmdir		= shmem_rmdir,
  	.mknod		= shmem_mknod,
  	.rename		= shmem_rename,

  #endif

  #ifdef CONFIG_TMPFS_POSIX_ACL
  	.setattr	= shmem_notify_change,
  	.setxattr	= generic_setxattr,
  	.getxattr	= generic_getxattr,
  	.listxattr	= generic_listxattr,
  	.removexattr	= generic_removexattr,
  	.permission	= shmem_permission,
  #endif
  };

  static const struct inode_operations shmem_special_inode_operations = {

  #ifdef CONFIG_TMPFS_POSIX_ACL
  	.setattr	= shmem_notify_change,
  	.setxattr	= generic_setxattr,
  	.getxattr	= generic_getxattr,
  	.listxattr	= generic_listxattr,
  	.removexattr	= generic_removexattr,
  	.permission	= shmem_permission,
  #endif

  };

  static const struct super_operations shmem_ops = {

  	.alloc_inode	= shmem_alloc_inode,
  	.destroy_inode	= shmem_destroy_inode,
  #ifdef CONFIG_TMPFS
  	.statfs		= shmem_statfs,
  	.remount_fs	= shmem_remount_fs,
  #endif
  	.delete_inode	= shmem_delete_inode,
  	.drop_inode	= generic_delete_inode,
  	.put_super	= shmem_put_super,
  };
  
  static struct vm_operations_struct shmem_vm_ops = {

  	.fault		= shmem_fault,

  #ifdef CONFIG_NUMA
  	.set_policy     = shmem_set_policy,
  	.get_policy     = shmem_get_policy,
  #endif
  };

  static int shmem_get_sb(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data, struct vfsmount *mnt)

  {

  	return get_sb_nodev(fs_type, flags, data, shmem_fill_super, mnt);

  }
  
  static struct file_system_type tmpfs_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "tmpfs",
  	.get_sb		= shmem_get_sb,
  	.kill_sb	= kill_litter_super,
  };
  static struct vfsmount *shm_mnt;
  
  static int __init init_tmpfs(void)
  {
  	int error;
  
  	error = init_inodecache();
  	if (error)
  		goto out3;
  
  	error = register_filesystem(&tmpfs_fs_type);
  	if (error) {
  		printk(KERN_ERR "Could not register tmpfs
  ");
  		goto out2;
  	}

  	shm_mnt = vfs_kern_mount(&tmpfs_fs_type, MS_NOUSER,

  				tmpfs_fs_type.name, NULL);
  	if (IS_ERR(shm_mnt)) {
  		error = PTR_ERR(shm_mnt);
  		printk(KERN_ERR "Could not kern_mount tmpfs
  ");
  		goto out1;
  	}
  	return 0;
  
  out1:
  	unregister_filesystem(&tmpfs_fs_type);
  out2:
  	destroy_inodecache();
  out3:
  	shm_mnt = ERR_PTR(error);
  	return error;
  }
  module_init(init_tmpfs)
  
  /*
   * shmem_file_setup - get an unlinked file living in tmpfs
   *
   * @name: name for dentry (to be seen in /proc/<pid>/maps
   * @size: size to be set for the file
   *
   */
  struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
  {
  	int error;
  	struct file *file;
  	struct inode *inode;
  	struct dentry *dentry, *root;
  	struct qstr this;
  
  	if (IS_ERR(shm_mnt))
  		return (void *)shm_mnt;
  
  	if (size < 0 || size > SHMEM_MAX_BYTES)
  		return ERR_PTR(-EINVAL);
  
  	if (shmem_acct_size(flags, size))
  		return ERR_PTR(-ENOMEM);
  
  	error = -ENOMEM;
  	this.name = name;
  	this.len = strlen(name);
  	this.hash = 0; /* will go */
  	root = shm_mnt->mnt_root;
  	dentry = d_alloc(root, &this);
  	if (!dentry)
  		goto put_memory;
  
  	error = -ENFILE;
  	file = get_empty_filp();
  	if (!file)
  		goto put_dentry;
  
  	error = -ENOSPC;
  	inode = shmem_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
  	if (!inode)
  		goto close_file;
  
  	SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
  	d_instantiate(dentry, inode);
  	inode->i_size = size;
  	inode->i_nlink = 0;	/* It is unlinked */

  	file->f_path.mnt = mntget(shm_mnt);
  	file->f_path.dentry = dentry;

  	file->f_mapping = inode->i_mapping;
  	file->f_op = &shmem_file_operations;
  	file->f_mode = FMODE_WRITE | FMODE_READ;
  	return file;
  
  close_file:
  	put_filp(file);
  put_dentry:
  	dput(dentry);
  put_memory:
  	shmem_unacct_size(flags, size);
  	return ERR_PTR(error);
  }
  
  /*
   * shmem_zero_setup - setup a shared anonymous mapping
   *
   * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
   */
  int shmem_zero_setup(struct vm_area_struct *vma)
  {
  	struct file *file;
  	loff_t size = vma->vm_end - vma->vm_start;
  
  	file = shmem_file_setup("dev/zero", size, vma->vm_flags);
  	if (IS_ERR(file))
  		return PTR_ERR(file);
  
  	if (vma->vm_file)
  		fput(vma->vm_file);
  	vma->vm_file = file;
  	vma->vm_ops = &shmem_vm_ops;
  	return 0;
  }