diff options
| -rw-r--r-- | mm/zswap.c | 182 |
1 files changed, 88 insertions, 94 deletions
diff --git a/mm/zswap.c b/mm/zswap.c index 0ffcad03baea..5a63f78a5601 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -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 - */ - if (refcount >= 0) { - /* no invalidate yet, remove from rbtree */ - rb_erase(&entry->rbnode, &tree->rbroot); - } + * 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 (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 */ @@ -743,22 +762,9 @@ 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)) { - spin_unlock(&tree->lock); - return 0; - } + zswap_entry_put(tree, entry); 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); |