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mm/zswap: refactor the get/put routines

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The refcount routine was not fit the kernel get/put semantic exactly,
There were too many judgement statements on refcount and it could be
minus.

This patch does the following:

 - move refcount judgement to zswap_entry_put() to hide resource free function.

 - add a new function zswap_entry_find_get(), so that callers can use
   easily in the following pattern:

     zswap_entry_find_get
     .../* do something */
     zswap_entry_put

 - to eliminate compile error, move some functions declaration

This patch is based on Minchan Kim <minchan@kernel.org> 's idea and suggestion.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Bob Liu <bob.liu@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Weijie Yang 2013-11-12 15:08:27 -08:00 committed by Linus Torvalds
parent 67d13fe846
commit 0ab0abcf51
1 changed files with 88 additions and 94 deletions
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180
mm/zswap.c
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@ -217,6 +217,7 @@ static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
if (!entry)
return NULL;
entry->refcount = 1;
RB_CLEAR_NODE(&entry->rbnode);
return entry;
}
@ -225,19 +226,6 @@ static void zswap_entry_cache_free(struct zswap_entry *entry)
kmem_cache_free(zswap_entry_cache, entry);
}
/* caller must hold the tree lock */
static void zswap_entry_get(struct zswap_entry *entry)
{
entry->refcount++;
}
/* caller must hold the tree lock */
static int zswap_entry_put(struct zswap_entry *entry)
{
entry->refcount--;
return entry->refcount;
}
/*********************************
* rbtree functions
**********************************/
@ -285,6 +273,61 @@ static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
return 0;
}
static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
{
if (!RB_EMPTY_NODE(&entry->rbnode)) {
rb_erase(&entry->rbnode, root);
RB_CLEAR_NODE(&entry->rbnode);
}
}
/*
* Carries out the common pattern of freeing and entry's zsmalloc allocation,
* freeing the entry itself, and decrementing the number of stored pages.
*/
static void zswap_free_entry(struct zswap_tree *tree,
struct zswap_entry *entry)
{
zbud_free(tree->pool, entry->handle);
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
zswap_pool_pages = zbud_get_pool_size(tree->pool);
}
/* caller must hold the tree lock */
static void zswap_entry_get(struct zswap_entry *entry)
{
entry->refcount++;
}
/* caller must hold the tree lock
* remove from the tree and free it, if nobody reference the entry
*/
static void zswap_entry_put(struct zswap_tree *tree,
struct zswap_entry *entry)
{
int refcount = --entry->refcount;
BUG_ON(refcount < 0);
if (refcount == 0) {
zswap_rb_erase(&tree->rbroot, entry);
zswap_free_entry(tree, entry);
}
}
/* caller must hold the tree lock */
static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
pgoff_t offset)
{
struct zswap_entry *entry = NULL;
entry = zswap_rb_search(root, offset);
if (entry)
zswap_entry_get(entry);
return entry;
}
/*********************************
* per-cpu code
**********************************/
@ -368,18 +411,6 @@ static bool zswap_is_full(void)
zswap_pool_pages);
}
/*
* Carries out the common pattern of freeing and entry's zsmalloc allocation,
* freeing the entry itself, and decrementing the number of stored pages.
*/
static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry)
{
zbud_free(tree->pool, entry->handle);
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
zswap_pool_pages = zbud_get_pool_size(tree->pool);
}
/*********************************
* writeback code
**********************************/
@ -503,7 +534,7 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
struct page *page;
u8 *src, *dst;
unsigned int dlen;
int ret, refcount;
int ret;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
};
@ -518,13 +549,12 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
/* find and ref zswap entry */
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
entry = zswap_entry_find_get(&tree->rbroot, offset);
if (!entry) {
/* entry was invalidated */
spin_unlock(&tree->lock);
return 0;
}
zswap_entry_get(entry);
spin_unlock(&tree->lock);
BUG_ON(offset != entry->offset);
@ -566,42 +596,35 @@ static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
zswap_written_back_pages++;
spin_lock(&tree->lock);
/* drop local reference */
zswap_entry_put(entry);
/* drop the initial reference from entry creation */
refcount = zswap_entry_put(entry);
zswap_entry_put(tree, entry);
/*
* There are three possible values for refcount here:
* (1) refcount is 1, load is in progress, unlink from rbtree,
* load will free
* (2) refcount is 0, (normal case) entry is valid,
* remove from rbtree and free entry
* (3) refcount is -1, invalidate happened during writeback,
* free entry
* There are two possible situations for entry here:
* (1) refcount is 1(normal case), entry is valid and on the tree
* (2) refcount is 0, entry is freed and not on the tree
* because invalidate happened during writeback
* search the tree and free the entry if find entry
*/
if (refcount >= 0) {
/* no invalidate yet, remove from rbtree */
rb_erase(&entry->rbnode, &tree->rbroot);
}
if (entry == zswap_rb_search(&tree->rbroot, offset))
zswap_entry_put(tree, entry);
spin_unlock(&tree->lock);
if (refcount <= 0) {
/* free the entry */
zswap_free_entry(tree, entry);
return 0;
}
return -EAGAIN;
goto end;
/*
* if we get here due to ZSWAP_SWAPCACHE_EXIST
* a load may happening concurrently
* it is safe and okay to not free the entry
* if we free the entry in the following put
* it it either okay to return !0
*/
fail:
spin_lock(&tree->lock);
refcount = zswap_entry_put(entry);
if (refcount <= 0) {
/* invalidate happened, consider writeback as success */
zswap_free_entry(tree, entry);
ret = 0;
}
zswap_entry_put(tree, entry);
spin_unlock(&tree->lock);
end:
return ret;
}
@ -685,11 +708,8 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
if (ret == -EEXIST) {
zswap_duplicate_entry++;
/* remove from rbtree */
rb_erase(&dupentry->rbnode, &tree->rbroot);
if (!zswap_entry_put(dupentry)) {
/* free */
zswap_free_entry(tree, dupentry);
}
zswap_rb_erase(&tree->rbroot, dupentry);
zswap_entry_put(tree, dupentry);
}
} while (ret == -EEXIST);
spin_unlock(&tree->lock);
@ -718,17 +738,16 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
struct zswap_entry *entry;
u8 *src, *dst;
unsigned int dlen;
int refcount, ret;
int ret;
/* find */
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
entry = zswap_entry_find_get(&tree->rbroot, offset);
if (!entry) {
/* entry was written back */
spin_unlock(&tree->lock);
return -1;
}
zswap_entry_get(entry);
spin_unlock(&tree->lock);
/* decompress */
@ -743,21 +762,8 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
BUG_ON(ret);
spin_lock(&tree->lock);
refcount = zswap_entry_put(entry);
if (likely(refcount)) {
zswap_entry_put(tree, entry);
spin_unlock(&tree->lock);
return 0;
}
spin_unlock(&tree->lock);
/*
* We don't have to unlink from the rbtree because
* zswap_writeback_entry() or zswap_frontswap_invalidate page()
* has already done this for us if we are the last reference.
*/
/* free */
zswap_free_entry(tree, entry);
return 0;
}
@ -767,7 +773,6 @@ static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
{
struct zswap_tree *tree = zswap_trees[type];
struct zswap_entry *entry;
int refcount;
/* find */
spin_lock(&tree->lock);
@ -779,20 +784,12 @@ static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
}
/* remove from rbtree */
rb_erase(&entry->rbnode, &tree->rbroot);
zswap_rb_erase(&tree->rbroot, entry);
/* drop the initial reference from entry creation */
refcount = zswap_entry_put(entry);
zswap_entry_put(tree, entry);
spin_unlock(&tree->lock);
if (refcount) {
/* writeback in progress, writeback will free */
return;
}
/* free */
zswap_free_entry(tree, entry);
}
/* frees all zswap entries for the given swap type */
@ -806,11 +803,8 @@ static void zswap_frontswap_invalidate_area(unsigned type)
/* walk the tree and free everything */
spin_lock(&tree->lock);
rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode) {
zbud_free(tree->pool, entry->handle);
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
}
rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
zswap_free_entry(tree, entry);
tree->rbroot = RB_ROOT;
spin_unlock(&tree->lock);