X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=mm%2Fshmem.c;h=5574b00ca771e8779fbd189d7b03c5ed8a8f48c3;hp=5cc21f8b4cd3e7e39dcd2f20f4fd0f710cf47dee;hb=285b2c4fdd69ea73b4762785d8c6be83b6c074a6;hpb=968e75fc13b6d582f42ce44172e13ba58157e11f

diff --git a/mm/shmem.c b/mm/shmem.c
index 5cc21f8b4cd3..5574b00ca771 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -66,37 +66,9 @@ static struct vfsmount *shm_mnt;
 #include <asm/div64.h>
 #include <asm/pgtable.h>
 
-/*
- * The maximum size of a shmem/tmpfs file is limited by the maximum size of
- * its triple-indirect swap vector - see illustration at shmem_swp_entry().
- *
- * With 4kB page size, maximum file size is just over 2TB on a 32-bit kernel,
- * but one eighth of that on a 64-bit kernel.  With 8kB page size, maximum
- * file size is just over 4TB on a 64-bit kernel, but 16TB on a 32-bit kernel,
- * MAX_LFS_FILESIZE being then more restrictive than swap vector layout.
- *
- * We use / and * instead of shifts in the definitions below, so that the swap
- * vector can be tested with small even values (e.g. 20) for ENTRIES_PER_PAGE.
- */
-#define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long))
-#define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE)
-
-#define SHMSWP_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))
-#define SHMSWP_MAX_BYTES (SHMSWP_MAX_INDEX << PAGE_CACHE_SHIFT)
-
-#define SHMEM_MAX_BYTES  min_t(unsigned long long, SHMSWP_MAX_BYTES, MAX_LFS_FILESIZE)
-#define SHMEM_MAX_INDEX  ((unsigned long)((SHMEM_MAX_BYTES+1) >> PAGE_CACHE_SHIFT))
-
 #define BLOCKS_PER_PAGE  (PAGE_CACHE_SIZE/512)
 #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
 
@@ -107,7 +79,7 @@ struct shmem_xattr {
 	char value[0];
 };
 
-/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
+/* Flag allocation requirements to shmem_getpage */
 enum sgp_type {
 	SGP_READ,	/* don't exceed i_size, don't allocate page */
 	SGP_CACHE,	/* don't exceed i_size, may allocate page */
@@ -137,56 +109,6 @@ static inline int shmem_getpage(struct inode *inode, pgoff_t index,
 			mapping_gfp_mask(inode->i_mapping), fault_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.
-	 *
-	 * Mobility flags are masked out as swap vectors cannot move
-	 */
-	return alloc_pages((gfp_mask & ~GFP_MOVABLE_MASK) | __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;
@@ -303,468 +225,56 @@ static void shmem_recalc_inode(struct inode *inode)
 	}
 }
 
-/**
- * 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)
+static void shmem_put_swap(struct shmem_inode_info *info, pgoff_t index,
+			   swp_entry_t swap)
 {
-	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.
- * @info:	info structure for the inode
- * @index:	index of the page to find
- * @sgp:	check and recheck i_size? skip allocation?
- * @gfp:	gfp mask to use for any page allocation
- *
- * If the entry does not exist, allocate it.
- */
-static swp_entry_t *shmem_swp_alloc(struct shmem_inode_info *info,
-			unsigned long index, enum sgp_type sgp, gfp_t gfp)
-{
-	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 used_blocks against 1 less max_blocks, 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) {
-			if (percpu_counter_compare(&sbinfo->used_blocks,
-						sbinfo->max_blocks - 1) >= 0)
-				return ERR_PTR(-ENOSPC);
-			percpu_counter_inc(&sbinfo->used_blocks);
-			inode->i_blocks += BLOCKS_PER_PAGE;
-		}
-
-		spin_unlock(&info->lock);
-		page = shmem_dir_alloc(gfp);
-		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;
+	if (index < SHMEM_NR_DIRECT)
+		info->i_direct[index] = swap;
 }
 
-static void shmem_free_pages(struct list_head *next)
+static swp_entry_t shmem_get_swap(struct shmem_inode_info *info, pgoff_t index)
 {
-	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);
+	return (index < SHMEM_NR_DIRECT) ?
+		info->i_direct[index] : (swp_entry_t){0};
 }
 
-void shmem_truncate_range(struct inode *inode, loff_t start, loff_t end)
+void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
 {
+	struct address_space *mapping = inode->i_mapping;
 	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;
+	pgoff_t start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+	pgoff_t end = (lend >> PAGE_CACHE_SHIFT);
+	pgoff_t index;
+	swp_entry_t swap;
 
-	truncate_inode_pages_range(inode->i_mapping, start, end);
+	truncate_inode_pages_range(mapping, lstart, lend);
 
-	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
-	idx = (start + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-	if (idx >= info->next_index)
-		return;
+	if (end > SHMEM_NR_DIRECT)
+		end = SHMEM_NR_DIRECT;
 
 	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 (index = start; index < end; index++) {
+		swap = shmem_get_swap(info, index);
+		if (swap.val) {
+			free_swap_and_cache(swap);
+			shmem_put_swap(info, index, (swp_entry_t){0});
+			info->swapped--;
 		}
 	}
 
-	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)) {
+	if (mapping->nrpages) {
+		spin_unlock(&info->lock);
 		/*
-		 * Call truncate_inode_pages again: racing shmem_unuse_inode
-		 * may have swizzled a page in from swap since
-		 * truncate_pagecache 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.
+		 * A page may have meanwhile sneaked in from swap.
 		 */
-		truncate_inode_pages_range(inode->i_mapping, start, end);
+		truncate_inode_pages_range(mapping, lstart, lend);
+		spin_lock(&info->lock);
 	}
 
-	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);
-	}
+	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 }
 EXPORT_SYMBOL_GPL(shmem_truncate_range);
 
@@ -797,19 +307,6 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
 				if (page)
 					unlock_page(page);
 			}
-			/*
-			 * 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 (newsize) {
-				struct shmem_inode_info *info = SHMEM_I(inode);
-				spin_lock(&info->lock);
-				info->flags &= ~SHMEM_PAGEIN;
-				spin_unlock(&info->lock);
-			}
 		}
 		if (newsize != oldsize) {
 			i_size_write(inode, newsize);
@@ -859,106 +356,28 @@ static void shmem_evict_inode(struct inode *inode)
 	end_writeback(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 address_space *mapping;
+	struct address_space *mapping = info->vfs_inode.i_mapping;
 	unsigned long idx;
-	unsigned long size;
-	unsigned long limit;
-	unsigned long stage;
-	struct page **dir;
-	struct page *subdir;
-	swp_entry_t *ptr;
-	int offset;
 	int error;
 
-	idx = 0;
-	ptr = info->i_direct;
-	spin_lock(&info->lock);
-	if (!info->swapped) {
-		list_del_init(&info->swaplist);
-		goto lost2;
-	}
-	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);
-			if (cond_resched_lock(&info->lock)) {
-				/* check it has not been truncated */
-				if (limit > info->next_index) {
-					limit = info->next_index;
-					if (idx >= limit)
-						goto lost2;
-				}
-			}
-			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);
-			shmem_swp_unmap(ptr);
-			if (offset >= 0) {
-				shmem_dir_unmap(dir);
-				ptr = shmem_swp_map(subdir);
-				goto found;
-			}
-		}
-	}
-lost1:
-	shmem_dir_unmap(dir-1);
-lost2:
-	spin_unlock(&info->lock);
+	for (idx = 0; idx < SHMEM_NR_DIRECT; idx++)
+		if (shmem_get_swap(info, idx).val == entry.val)
+			goto found;
 	return 0;
 found:
-	idx += offset;
-	ptr += offset;
+	spin_lock(&info->lock);
+	if (shmem_get_swap(info, idx).val != entry.val) {
+		spin_unlock(&info->lock);
+		return 0;
+	}
 
 	/*
 	 * Move _head_ to start search for next from here.
 	 * But be careful: shmem_evict_inode checks list_empty without taking
 	 * mutex, and there's an instant in list_move_tail when info->swaplist
-	 * would appear empty, if it were the only one on shmem_swaplist.  We
-	 * could avoid doing it if inode NULL; or use this minor optimization.
+	 * would appear empty, if it were the only one on shmem_swaplist.
 	 */
 	if (shmem_swaplist.next != &info->swaplist)
 		list_move_tail(&shmem_swaplist, &info->swaplist);
@@ -968,19 +387,17 @@ found:
 	 * but also to hold up shmem_evict_inode(): so inode cannot be freed
 	 * beneath us (pagelock doesn't help until the page is in pagecache).
 	 */
-	mapping = info->vfs_inode.i_mapping;
 	error = add_to_page_cache_locked(page, mapping, idx, GFP_NOWAIT);
 	/* which does mem_cgroup_uncharge_cache_page on error */
 
 	if (error != -ENOMEM) {
 		delete_from_swap_cache(page);
 		set_page_dirty(page);
-		info->flags |= SHMEM_PAGEIN;
-		shmem_swp_set(info, ptr, 0);
+		shmem_put_swap(info, idx, (swp_entry_t){0});
+		info->swapped--;
 		swap_free(entry);
 		error = 1;	/* not an error, but entry was found */
 	}
-	shmem_swp_unmap(ptr);
 	spin_unlock(&info->lock);
 	return error;
 }
@@ -1017,7 +434,14 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
 	mutex_lock(&shmem_swaplist_mutex);
 	list_for_each_safe(p, next, &shmem_swaplist) {
 		info = list_entry(p, struct shmem_inode_info, swaplist);
-		found = shmem_unuse_inode(info, entry, page);
+		if (!info->swapped) {
+			spin_lock(&info->lock);
+			if (!info->swapped)
+				list_del_init(&info->swaplist);
+			spin_unlock(&info->lock);
+		}
+		if (info->swapped)
+			found = shmem_unuse_inode(info, entry, page);
 		cond_resched();
 		if (found)
 			break;
@@ -1041,7 +465,7 @@ out:
 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct shmem_inode_info *info;
-	swp_entry_t *entry, swap;
+	swp_entry_t swap, oswap;
 	struct address_space *mapping;
 	unsigned long index;
 	struct inode *inode;
@@ -1067,6 +491,15 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
 		goto redirty;
 	}
+
+	/*
+	 * Just for this patch, we have a toy implementation,
+	 * which can swap out only the first SHMEM_NR_DIRECT pages:
+	 * for simple demonstration of where we need to think about swap.
+	 */
+	if (index >= SHMEM_NR_DIRECT)
+		goto redirty;
+
 	swap = get_swap_page();
 	if (!swap.val)
 		goto redirty;
@@ -1087,22 +520,19 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	spin_lock(&info->lock);
 	mutex_unlock(&shmem_swaplist_mutex);
 
-	if (index >= info->next_index) {
-		BUG_ON(!(info->flags & SHMEM_TRUNCATE));
-		goto unlock;
-	}
-	entry = shmem_swp_entry(info, index, NULL);
-	if (entry->val) {
+	oswap = shmem_get_swap(info, index);
+	if (oswap.val) {
 		WARN_ON_ONCE(1);	/* Still happens? Tell us about it! */
-		free_swap_and_cache(*entry);
-		shmem_swp_set(info, entry, 0);
+		free_swap_and_cache(oswap);
+		shmem_put_swap(info, index, (swp_entry_t){0});
+		info->swapped--;
 	}
 	shmem_recalc_inode(inode);
 
 	if (add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
 		delete_from_page_cache(page);
-		shmem_swp_set(info, entry, swap.val);
-		shmem_swp_unmap(entry);
+		shmem_put_swap(info, index, swap);
+		info->swapped++;
 		swap_shmem_alloc(swap);
 		spin_unlock(&info->lock);
 		BUG_ON(page_mapped(page));
@@ -1110,13 +540,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		return 0;
 	}
 
-	shmem_swp_unmap(entry);
-unlock:
 	spin_unlock(&info->lock);
-	/*
-	 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
-	 * clear SWAP_HAS_CACHE flag.
-	 */
 	swapcache_free(swap, NULL);
 redirty:
 	set_page_dirty(page);
@@ -1230,12 +654,10 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t idx,
 	struct shmem_sb_info *sbinfo;
 	struct page *page;
 	struct page *prealloc_page = NULL;
-	swp_entry_t *entry;
 	swp_entry_t swap;
 	int error;
-	int ret;
 
-	if (idx >= SHMEM_MAX_INDEX)
+	if (idx > (MAX_LFS_FILESIZE >> PAGE_CACHE_SHIFT))
 		return -EFBIG;
 repeat:
 	page = find_lock_page(mapping, idx);
@@ -1272,37 +694,22 @@ repeat:
 
 	spin_lock(&info->lock);
 	shmem_recalc_inode(inode);
-	entry = shmem_swp_alloc(info, idx, sgp, gfp);
-	if (IS_ERR(entry)) {
-		spin_unlock(&info->lock);
-		error = PTR_ERR(entry);
-		goto out;
-	}
-	swap = *entry;
-
+	swap = shmem_get_swap(info, idx);
 	if (swap.val) {
 		/* Look it up and read it in.. */
 		page = lookup_swap_cache(swap);
 		if (!page) {
-			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			/* here we actually do the io */
 			if (fault_type)
 				*fault_type |= VM_FAULT_MAJOR;
 			page = shmem_swapin(swap, gfp, info, idx);
 			if (!page) {
-				spin_lock(&info->lock);
-				entry = shmem_swp_alloc(info, idx, sgp, gfp);
-				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)
+				swp_entry_t nswap = shmem_get_swap(info, idx);
+				if (nswap.val == swap.val) {
+					error = -ENOMEM;
 					goto out;
+				}
 				goto repeat;
 			}
 			wait_on_page_locked(page);
@@ -1312,14 +719,12 @@ repeat:
 
 		/* We have to do this with page locked to prevent races */
 		if (!trylock_page(page)) {
-			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			wait_on_page_locked(page);
 			page_cache_release(page);
 			goto repeat;
 		}
 		if (PageWriteback(page)) {
-			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			wait_on_page_writeback(page);
 			unlock_page(page);
@@ -1327,7 +732,6 @@ repeat:
 			goto repeat;
 		}
 		if (!PageUptodate(page)) {
-			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			unlock_page(page);
 			page_cache_release(page);
@@ -1338,7 +742,6 @@ repeat:
 		error = add_to_page_cache_locked(page, mapping,
 						 idx, GFP_NOWAIT);
 		if (error) {
-			shmem_swp_unmap(entry);
 			spin_unlock(&info->lock);
 			if (error == -ENOMEM) {
 				/*
@@ -1358,16 +761,14 @@ repeat:
 			goto repeat;
 		}
 
-		info->flags |= SHMEM_PAGEIN;
-		shmem_swp_set(info, entry, 0);
-		shmem_swp_unmap(entry);
 		delete_from_swap_cache(page);
+		shmem_put_swap(info, idx, (swp_entry_t){0});
+		info->swapped--;
 		spin_unlock(&info->lock);
 		set_page_dirty(page);
 		swap_free(swap);
 
 	} else if (sgp == SGP_READ) {
-		shmem_swp_unmap(entry);
 		page = find_get_page(mapping, idx);
 		if (page && !trylock_page(page)) {
 			spin_unlock(&info->lock);
@@ -1378,7 +779,6 @@ repeat:
 		spin_unlock(&info->lock);
 
 	} else if (prealloc_page) {
-		shmem_swp_unmap(entry);
 		sbinfo = SHMEM_SB(inode->i_sb);
 		if (sbinfo->max_blocks) {
 			if (percpu_counter_compare(&sbinfo->used_blocks,
@@ -1393,34 +793,24 @@ repeat:
 		page = prealloc_page;
 		prealloc_page = NULL;
 
-		entry = shmem_swp_alloc(info, idx, sgp, gfp);
-		if (IS_ERR(entry))
-			error = PTR_ERR(entry);
-		else {
-			swap = *entry;
-			shmem_swp_unmap(entry);
-		}
-		ret = error || swap.val;
-		if (ret)
+		swap = shmem_get_swap(info, idx);
+		if (swap.val)
 			mem_cgroup_uncharge_cache_page(page);
 		else
-			ret = add_to_page_cache_lru(page, mapping,
+			error = add_to_page_cache_lru(page, mapping,
 						idx, GFP_NOWAIT);
 		/*
 		 * At add_to_page_cache_lru() failure,
 		 * uncharge will be done automatically.
 		 */
-		if (ret) {
+		if (swap.val || error) {
 			shmem_unacct_blocks(info->flags, 1);
 			shmem_free_blocks(inode, 1);
 			spin_unlock(&info->lock);
 			page_cache_release(page);
-			if (error)
-				goto out;
 			goto repeat;
 		}
 
-		info->flags |= SHMEM_PAGEIN;
 		info->alloced++;
 		spin_unlock(&info->lock);
 		clear_highpage(page);
@@ -2627,7 +2017,7 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
 		goto failed;
 	sbinfo->free_inodes = sbinfo->max_inodes;
 
-	sb->s_maxbytes = SHMEM_MAX_BYTES;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_blocksize = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = TMPFS_MAGIC;
@@ -2863,7 +2253,7 @@ out4:
 void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
 					struct page **pagep, swp_entry_t *ent)
 {
-	swp_entry_t entry = { .val = 0 }, *ptr;
+	swp_entry_t entry = { .val = 0 };
 	struct page *page = NULL;
 	struct shmem_inode_info *info = SHMEM_I(inode);
 
@@ -2871,16 +2261,13 @@ void mem_cgroup_get_shmem_target(struct inode *inode, pgoff_t pgoff,
 		goto out;
 
 	spin_lock(&info->lock);
-	ptr = shmem_swp_entry(info, pgoff, NULL);
 #ifdef CONFIG_SWAP
-	if (ptr && ptr->val) {
-		entry.val = ptr->val;
+	entry = shmem_get_swap(info, pgoff);
+	if (entry.val)
 		page = find_get_page(&swapper_space, entry.val);
-	} else
+	else
 #endif
 		page = find_get_page(inode->i_mapping, pgoff);
-	if (ptr)
-		shmem_swp_unmap(ptr);
 	spin_unlock(&info->lock);
 out:
 	*pagep = page;
@@ -2963,7 +2350,6 @@ out:
 #define shmem_get_inode(sb, dir, mode, dev, flags)	ramfs_get_inode(sb, dir, mode, dev)
 #define shmem_acct_size(flags, size)		0
 #define shmem_unacct_size(flags, size)		do {} while (0)
-#define SHMEM_MAX_BYTES				MAX_LFS_FILESIZE
 
 #endif /* CONFIG_SHMEM */
 
@@ -2987,7 +2373,7 @@ struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags
 	if (IS_ERR(shm_mnt))
 		return (void *)shm_mnt;
 
-	if (size < 0 || size > SHMEM_MAX_BYTES)
+	if (size < 0 || size > MAX_LFS_FILESIZE)
 		return ERR_PTR(-EINVAL);
 
 	if (shmem_acct_size(flags, size))