diff options
| -rw-r--r-- | mm/Kconfig | 20 | ||||
| -rw-r--r-- | mm/Makefile | 1 | ||||
| -rw-r--r-- | mm/zswap.c | 943 |
3 files changed, 964 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index 45503ed5f3a..8028dcc6615 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -488,6 +488,26 @@ config ZBUD deterministic reclaim properties that make it preferable to a higher density approach when reclaim will be used. +config ZSWAP + bool "Compressed cache for swap pages (EXPERIMENTAL)" + depends on FRONTSWAP && CRYPTO=y + select CRYPTO_LZO + select ZBUD + default n + help + A lightweight compressed cache for swap pages. It takes + pages that are in the process of being swapped out and attempts to + compress them into a dynamically allocated RAM-based memory pool. + This can result in a significant I/O reduction on swap device and, + in the case where decompressing from RAM is faster that swap device + reads, can also improve workload performance. + + This is marked experimental because it is a new feature (as of + v3.11) that interacts heavily with memory reclaim. While these + interactions don't cause any known issues on simple memory setups, + they have not be fully explored on the large set of potential + configurations and workloads that exist. + config MEM_SOFT_DIRTY bool "Track memory changes" depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY diff --git a/mm/Makefile b/mm/Makefile index 95f0197ce3d..f00803386a6 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -32,6 +32,7 @@ obj-$(CONFIG_HAVE_MEMBLOCK) += memblock.o obj-$(CONFIG_BOUNCE) += bounce.o obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o obj-$(CONFIG_FRONTSWAP) += frontswap.o +obj-$(CONFIG_ZSWAP) += zswap.o obj-$(CONFIG_HAS_DMA) += dmapool.o obj-$(CONFIG_HUGETLBFS) += hugetlb.o obj-$(CONFIG_NUMA) += mempolicy.o diff --git a/mm/zswap.c b/mm/zswap.c new file mode 100644 index 00000000000..deda2b671e1 --- /dev/null +++ b/mm/zswap.c @@ -0,0 +1,943 @@ +/* + * zswap.c - zswap driver file + * + * zswap is a backend for frontswap that takes pages that are in the process + * of being swapped out and attempts to compress and store them in a + * RAM-based memory pool. This can result in a significant I/O reduction on + * the swap device and, in the case where decompressing from RAM is faster + * than reading from the swap device, can also improve workload performance. + * + * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. +*/ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/cpu.h> +#include <linux/highmem.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/types.h> +#include <linux/atomic.h> +#include <linux/frontswap.h> +#include <linux/rbtree.h> +#include <linux/swap.h> +#include <linux/crypto.h> +#include <linux/mempool.h> +#include <linux/zbud.h> + +#include <linux/mm_types.h> +#include <linux/page-flags.h> +#include <linux/swapops.h> +#include <linux/writeback.h> +#include <linux/pagemap.h> + +/********************************* +* statistics +**********************************/ +/* Number of memory pages used by the compressed pool */ +static u64 zswap_pool_pages; +/* The number of compressed pages currently stored in zswap */ +static atomic_t zswap_stored_pages = ATOMIC_INIT(0); + +/* + * The statistics below are not protected from concurrent access for + * performance reasons so they may not be a 100% accurate. However, + * they do provide useful information on roughly how many times a + * certain event is occurring. +*/ + +/* Pool limit was hit (see zswap_max_pool_percent) */ +static u64 zswap_pool_limit_hit; +/* Pages written back when pool limit was reached */ +static u64 zswap_written_back_pages; +/* Store failed due to a reclaim failure after pool limit was reached */ +static u64 zswap_reject_reclaim_fail; +/* Compressed page was too big for the allocator to (optimally) store */ +static u64 zswap_reject_compress_poor; +/* Store failed because underlying allocator could not get memory */ +static u64 zswap_reject_alloc_fail; +/* Store failed because the entry metadata could not be allocated (rare) */ +static u64 zswap_reject_kmemcache_fail; +/* Duplicate store was encountered (rare) */ +static u64 zswap_duplicate_entry; + +/********************************* +* tunables +**********************************/ +/* Enable/disable zswap (disabled by default, fixed at boot for now) */ +static bool zswap_enabled __read_mostly; +module_param_named(enabled, zswap_enabled, bool, 0); + +/* Compressor to be used by zswap (fixed at boot for now) */ +#define ZSWAP_COMPRESSOR_DEFAULT "lzo" +static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; +module_param_named(compressor, zswap_compressor, charp, 0); + +/* The maximum percentage of memory that the compressed pool can occupy */ +static unsigned int zswap_max_pool_percent = 20; +module_param_named(max_pool_percent, + zswap_max_pool_percent, uint, 0644); + +/********************************* +* compression functions +**********************************/ +/* per-cpu compression transforms */ +static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms; + +enum comp_op { + ZSWAP_COMPOP_COMPRESS, + ZSWAP_COMPOP_DECOMPRESS +}; + +static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen, + u8 *dst, unsigned int *dlen) +{ + struct crypto_comp *tfm; + int ret; + + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu()); + switch (op) { + case ZSWAP_COMPOP_COMPRESS: + ret = crypto_comp_compress(tfm, src, slen, dst, dlen); + break; + case ZSWAP_COMPOP_DECOMPRESS: + ret = crypto_comp_decompress(tfm, src, slen, dst, dlen); + break; + default: + ret = -EINVAL; + } + + put_cpu(); + return ret; +} + +static int __init zswap_comp_init(void) +{ + if (!crypto_has_comp(zswap_compressor, 0, 0)) { + pr_info("%s compressor not available\n", zswap_compressor); + /* fall back to default compressor */ + zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; + if (!crypto_has_comp(zswap_compressor, 0, 0)) + /* can't even load the default compressor */ + return -ENODEV; + } + pr_info("using %s compressor\n", zswap_compressor); + + /* alloc percpu transforms */ + zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *); + if (!zswap_comp_pcpu_tfms) + return -ENOMEM; + return 0; +} + +static void zswap_comp_exit(void) +{ + /* free percpu transforms */ + if (zswap_comp_pcpu_tfms) + free_percpu(zswap_comp_pcpu_tfms); +} + +/********************************* +* data structures +**********************************/ +/* + * struct zswap_entry + * + * This structure contains the metadata for tracking a single compressed + * page within zswap. + * + * rbnode - links the entry into red-black tree for the appropriate swap type + * refcount - the number of outstanding reference to the entry. This is needed + * to protect against premature freeing of the entry by code + * concurent calls to load, invalidate, and writeback. The lock + * for the zswap_tree structure that contains the entry must + * be held while changing the refcount. Since the lock must + * be held, there is no reason to also make refcount atomic. + * offset - the swap offset for the entry. Index into the red-black tree. + * handle - zsmalloc allocation handle that stores the compressed page data + * length - the length in bytes of the compressed page data. Needed during + * decompression + */ +struct zswap_entry { + struct rb_node rbnode; + pgoff_t offset; + int refcount; + unsigned int length; + unsigned long handle; +}; + +struct zswap_header { + swp_entry_t swpentry; +}; + +/* + * The tree lock in the zswap_tree struct protects a few things: + * - the rbtree + * - the refcount field of each entry in the tree + */ +struct zswap_tree { + struct rb_root rbroot; + spinlock_t lock; + struct zbud_pool *pool; +}; + +static struct zswap_tree *zswap_trees[MAX_SWAPFILES]; + +/********************************* +* zswap entry functions +**********************************/ +static struct kmem_cache *zswap_entry_cache; + +static int zswap_entry_cache_create(void) +{ + zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); + return (zswap_entry_cache == NULL); +} + +static void zswap_entry_cache_destory(void) +{ + kmem_cache_destroy(zswap_entry_cache); +} + +static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp) +{ + struct zswap_entry *entry; + entry = kmem_cache_alloc(zswap_entry_cache, gfp); + if (!entry) + return NULL; + entry->refcount = 1; + return entry; +} + +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 +**********************************/ +static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset) +{ + struct rb_node *node = root->rb_node; + struct zswap_entry *entry; + + while (node) { + entry = rb_entry(node, struct zswap_entry, rbnode); + if (entry->offset > offset) + node = node->rb_left; + else if (entry->offset < offset) + node = node->rb_right; + else + return entry; + } + return NULL; +} + +/* + * In the case that a entry with the same offset is found, a pointer to + * the existing entry is stored in dupentry and the function returns -EEXIST + */ +static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry, + struct zswap_entry **dupentry) +{ + struct rb_node **link = &root->rb_node, *parent = NULL; + struct zswap_entry *myentry; + + while (*link) { + parent = *link; + myentry = rb_entry(parent, struct zswap_entry, rbnode); + if (myentry->offset > entry->offset) + link = &(*link)->rb_left; + else if (myentry->offset < entry->offset) + link = &(*link)->rb_right; + else { + *dupentry = myentry; + return -EEXIST; + } + } + rb_link_node(&entry->rbnode, parent, link); + rb_insert_color(&entry->rbnode, root); + return 0; +} + +/********************************* +* per-cpu code +**********************************/ +static DEFINE_PER_CPU(u8 *, zswap_dstmem); + +static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu) +{ + struct crypto_comp *tfm; + u8 *dst; + + switch (action) { + case CPU_UP_PREPARE: + tfm = crypto_alloc_comp(zswap_compressor, 0, 0); + if (IS_ERR(tfm)) { + pr_err("can't allocate compressor transform\n"); + return NOTIFY_BAD; + } + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm; + dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL); + if (!dst) { + pr_err("can't allocate compressor buffer\n"); + crypto_free_comp(tfm); + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; + return NOTIFY_BAD; + } + per_cpu(zswap_dstmem, cpu) = dst; + break; + case CPU_DEAD: + case CPU_UP_CANCELED: + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu); + if (tfm) { + crypto_free_comp(tfm); + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; + } + dst = per_cpu(zswap_dstmem, cpu); + kfree(dst); + per_cpu(zswap_dstmem, cpu) = NULL; + break; + default: + break; + } + return NOTIFY_OK; +} + +static int zswap_cpu_notifier(struct notifier_block *nb, + unsigned long action, void *pcpu) +{ + unsigned long cpu = (unsigned long)pcpu; + return __zswap_cpu_notifier(action, cpu); +} + +static struct notifier_block zswap_cpu_notifier_block = { + .notifier_call = zswap_cpu_notifier +}; + +static int zswap_cpu_init(void) +{ + unsigned long cpu; + + get_online_cpus(); + for_each_online_cpu(cpu) + if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK) + goto cleanup; + register_cpu_notifier(&zswap_cpu_notifier_block); + put_online_cpus(); + return 0; + +cleanup: + for_each_online_cpu(cpu) + __zswap_cpu_notifier(CPU_UP_CANCELED, cpu); + put_online_cpus(); + return -ENOMEM; +} + +/********************************* +* helpers +**********************************/ +static bool zswap_is_full(void) +{ + return (totalram_pages * zswap_max_pool_percent / 100 < + 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 +**********************************/ +/* return enum for zswap_get_swap_cache_page */ +enum zswap_get_swap_ret { + ZSWAP_SWAPCACHE_NEW, + ZSWAP_SWAPCACHE_EXIST, + ZSWAP_SWAPCACHE_NOMEM +}; + +/* + * zswap_get_swap_cache_page + * + * This is an adaption of read_swap_cache_async() + * + * This function tries to find a page with the given swap entry + * in the swapper_space address space (the swap cache). If the page + * is found, it is returned in retpage. Otherwise, a page is allocated, + * added to the swap cache, and returned in retpage. + * + * If success, the swap cache page is returned in retpage + * Returns 0 if page was already in the swap cache, page is not locked + * Returns 1 if the new page needs to be populated, page is locked + * Returns <0 on error + */ +static int zswap_get_swap_cache_page(swp_entry_t entry, + struct page **retpage) +{ + struct page *found_page, *new_page = NULL; + struct address_space *swapper_space = &swapper_spaces[swp_type(entry)]; + int err; + + *retpage = NULL; + do { + /* + * First check the swap cache. Since this is normally + * called after lookup_swap_cache() failed, re-calling + * that would confuse statistics. + */ + found_page = find_get_page(swapper_space, entry.val); + if (found_page) + break; + + /* + * Get a new page to read into from swap. + */ + if (!new_page) { + new_page = alloc_page(GFP_KERNEL); + if (!new_page) + break; /* Out of memory */ + } + + /* + * call radix_tree_preload() while we can wait. + */ + err = radix_tree_preload(GFP_KERNEL); + if (err) + break; + + /* + * Swap entry may have been freed since our caller observed it. + */ + err = swapcache_prepare(entry); + if (err == -EEXIST) { /* seems racy */ + radix_tree_preload_end(); + continue; + } + if (err) { /* swp entry is obsolete ? */ + radix_tree_preload_end(); + break; + } + + /* May fail (-ENOMEM) if radix-tree node allocation failed. */ + __set_page_locked(new_page); + SetPageSwapBacked(new_page); + err = __add_to_swap_cache(new_page, entry); + if (likely(!err)) { + radix_tree_preload_end(); + lru_cache_add_anon(new_page); + *retpage = new_page; + return ZSWAP_SWAPCACHE_NEW; + } + radix_tree_preload_end(); + ClearPageSwapBacked(new_page); + __clear_page_locked(new_page); + /* + * add_to_swap_cache() doesn't return -EEXIST, so we can safely + * clear SWAP_HAS_CACHE flag. + */ + swapcache_free(entry, NULL); + } while (err != -ENOMEM); + + if (new_page) + page_cache_release(new_page); + if (!found_page) + return ZSWAP_SWAPCACHE_NOMEM; + *retpage = found_page; + return ZSWAP_SWAPCACHE_EXIST; +} + +/* + * Attempts to free an entry by adding a page to the swap cache, + * decompressing the entry data into the page, and issuing a + * bio write to write the page back to the swap device. + * + * This can be thought of as a "resumed writeback" of the page + * to the swap device. We are basically resuming the same swap + * writeback path that was intercepted with the frontswap_store() + * in the first place. After the page has been decompressed into + * the swap cache, the compressed version stored by zswap can be + * freed. + */ +static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle) +{ + struct zswap_header *zhdr; + swp_entry_t swpentry; + struct zswap_tree *tree; + pgoff_t offset; + struct zswap_entry *entry; + struct page *page; + u8 *src, *dst; + unsigned int dlen; + int ret, refcount; + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + }; + + /* extract swpentry from data */ + zhdr = zbud_map(pool, handle); + swpentry = zhdr->swpentry; /* here */ + zbud_unmap(pool, handle); + tree = zswap_trees[swp_type(swpentry)]; + offset = swp_offset(swpentry); + BUG_ON(pool != tree->pool); + + /* find and ref zswap entry */ + spin_lock(&tree->lock); + entry = zswap_rb_search(&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); + + /* try to allocate swap cache page */ + switch (zswap_get_swap_cache_page(swpentry, &page)) { + case ZSWAP_SWAPCACHE_NOMEM: /* no memory */ + ret = -ENOMEM; + goto fail; + + case ZSWAP_SWAPCACHE_EXIST: /* page is unlocked */ + /* page is already in the swap cache, ignore for now */ + page_cache_release(page); + ret = -EEXIST; + goto fail; + + case ZSWAP_SWAPCACHE_NEW: /* page is locked */ + /* decompress */ + dlen = PAGE_SIZE; + src = (u8 *)zbud_map(tree->pool, entry->handle) + + sizeof(struct zswap_header); + dst = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, + entry->length, dst, &dlen); + kunmap_atomic(dst); + zbud_unmap(tree->pool, entry->handle); + BUG_ON(ret); + BUG_ON(dlen != PAGE_SIZE); + + /* page is up to date */ + SetPageUptodate(page); + } + + /* start writeback */ + __swap_writepage(page, &wbc, end_swap_bio_write); + page_cache_release(page); + 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); + + /* + * 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); + } + spin_unlock(&tree->lock); + if (refcount <= 0) { + /* free the entry */ + zswap_free_entry(tree, entry); + return 0; + } + return -EAGAIN; + +fail: + spin_lock(&tree->lock); + zswap_entry_put(entry); + spin_unlock(&tree->lock); + return ret; +} + +/********************************* +* frontswap hooks +**********************************/ +/* attempts to compress and store an single page */ +static int zswap_frontswap_store(unsigned type, pgoff_t offset, + struct page *page) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct zswap_entry *entry, *dupentry; + int ret; + unsigned int dlen = PAGE_SIZE, len; + unsigned long handle; + char *buf; + u8 *src, *dst; + struct zswap_header *zhdr; + + if (!tree) { + ret = -ENODEV; + goto reject; + } + + /* reclaim space if needed */ + if (zswap_is_full()) { + zswap_pool_limit_hit++; + if (zbud_reclaim_page(tree->pool, 8)) { + zswap_reject_reclaim_fail++; + ret = -ENOMEM; + goto reject; + } + } + + /* allocate entry */ + entry = zswap_entry_cache_alloc(GFP_KERNEL); + if (!entry) { + zswap_reject_kmemcache_fail++; + ret = -ENOMEM; + goto reject; + } + + /* compress */ + dst = get_cpu_var(zswap_dstmem); + src = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen); + kunmap_atomic(src); + if (ret) { + ret = -EINVAL; + goto freepage; + } + + /* store */ + len = dlen + sizeof(struct zswap_header); + ret = zbud_alloc(tree->pool, len, __GFP_NORETRY | __GFP_NOWARN, + &handle); + if (ret == -ENOSPC) { + zswap_reject_compress_poor++; + goto freepage; + } + if (ret) { + zswap_reject_alloc_fail++; + goto freepage; + } + zhdr = zbud_map(tree->pool, handle); + zhdr->swpentry = swp_entry(type, offset); + buf = (u8 *)(zhdr + 1); + memcpy(buf, dst, dlen); + zbud_unmap(tree->pool, handle); + put_cpu_var(zswap_dstmem); + + /* populate entry */ + entry->offset = offset; + entry->handle = handle; + entry->length = dlen; + + /* map */ + spin_lock(&tree->lock); + do { + ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry); + 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); + } + } + } while (ret == -EEXIST); + spin_unlock(&tree->lock); + + /* update stats */ + atomic_inc(&zswap_stored_pages); + zswap_pool_pages = zbud_get_pool_size(tree->pool); + + return 0; + +freepage: + put_cpu_var(zswap_dstmem); + zswap_entry_cache_free(entry); +reject: + return ret; +} + +/* + * returns 0 if the page was successfully decompressed + * return -1 on entry not found or error +*/ +static int zswap_frontswap_load(unsigned type, pgoff_t offset, + struct page *page) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct zswap_entry *entry; + u8 *src, *dst; + unsigned int dlen; + int refcount, ret; + + /* find */ + spin_lock(&tree->lock); + entry = zswap_rb_search(&tree->rbroot, offset); + if (!entry) { + /* entry was written back */ + spin_unlock(&tree->lock); + return -1; + } + zswap_entry_get(entry); + spin_unlock(&tree->lock); + + /* decompress */ + dlen = PAGE_SIZE; + src = (u8 *)zbud_map(tree->pool, entry->handle) + + sizeof(struct zswap_header); + dst = kmap_atomic(page); + ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length, + dst, &dlen); + kunmap_atomic(dst); + zbud_unmap(tree->pool, entry->handle); + BUG_ON(ret); + + spin_lock(&tree->lock); + refcount = zswap_entry_put(entry); + if (likely(refcount)) { + 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; +} + +/* frees an entry in zswap */ +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); + entry = zswap_rb_search(&tree->rbroot, offset); + if (!entry) { + /* entry was written back */ + spin_unlock(&tree->lock); + return; + } + + /* remove from rbtree */ + rb_erase(&entry->rbnode, &tree->rbroot); + + /* drop the initial reference from entry creation */ + refcount = zswap_entry_put(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 */ +static void zswap_frontswap_invalidate_area(unsigned type) +{ + struct zswap_tree *tree = zswap_trees[type]; + struct rb_node *node; + struct zswap_entry *entry; + + if (!tree) + return; + + /* walk the tree and free everything */ + spin_lock(&tree->lock); + /* + * TODO: Even though this code should not be executed because + * the try_to_unuse() in swapoff should have emptied the tree, + * it is very wasteful to rebalance the tree after every + * removal when we are freeing the whole tree. + * + * If post-order traversal code is ever added to the rbtree + * implementation, it should be used here. + */ + while ((node = rb_first(&tree->rbroot))) { + entry = rb_entry(node, struct zswap_entry, rbnode); + rb_erase(&entry->rbnode, &tree->rbroot); + zbud_free(tree->pool, entry->handle); + zswap_entry_cache_free(entry); + atomic_dec(&zswap_stored_pages); + } + tree->rbroot = RB_ROOT; + spin_unlock(&tree->lock); +} + +static struct zbud_ops zswap_zbud_ops = { + .evict = zswap_writeback_entry +}; + +static void zswap_frontswap_init(unsigned type) +{ + struct zswap_tree *tree; + + tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL); + if (!tree) + goto err; + tree->pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops); + if (!tree->pool) + goto freetree; + tree->rbroot = RB_ROOT; + spin_lock_init(&tree->lock); + zswap_trees[type] = tree; + return; + +freetree: + kfree(tree); +err: + pr_err("alloc failed, zswap disabled for swap type %d\n", type); +} + +static struct frontswap_ops zswap_frontswap_ops = { + .store = zswap_frontswap_store, + .load = zswap_frontswap_load, + .invalidate_page = zswap_frontswap_invalidate_page, + .invalidate_area = zswap_frontswap_invalidate_area, + .init = zswap_frontswap_init +}; + +/********************************* +* debugfs functions +**********************************/ +#ifdef CONFIG_DEBUG_FS +#include <linux/debugfs.h> + +static struct dentry *zswap_debugfs_root; + +static int __init zswap_debugfs_init(void) +{ + if (!debugfs_initialized()) + return -ENODEV; + + zswap_debugfs_root = debugfs_create_dir("zswap", NULL); + if (!zswap_debugfs_root) + return -ENOMEM; + + debugfs_create_u64("pool_limit_hit", S_IRUGO, + zswap_debugfs_root, &zswap_pool_limit_hit); + debugfs_create_u64("reject_reclaim_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_reclaim_fail); + debugfs_create_u64("reject_alloc_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_alloc_fail); + debugfs_create_u64("reject_kmemcache_fail", S_IRUGO, + zswap_debugfs_root, &zswap_reject_kmemcache_fail); + debugfs_create_u64("reject_compress_poor", S_IRUGO, + zswap_debugfs_root, &zswap_reject_compress_poor); + debugfs_create_u64("written_back_pages", S_IRUGO, + zswap_debugfs_root, &zswap_written_back_pages); + debugfs_create_u64("duplicate_entry", S_IRUGO, + zswap_debugfs_root, &zswap_duplicate_entry); + debugfs_create_u64("pool_pages", S_IRUGO, + zswap_debugfs_root, &zswap_pool_pages); + debugfs_create_atomic_t("stored_pages", S_IRUGO, + zswap_debugfs_root, &zswap_stored_pages); + + return 0; +} + +static void __exit zswap_debugfs_exit(void) +{ + debugfs_remove_recursive(zswap_debugfs_root); +} +#else +static int __init zswap_debugfs_init(void) +{ + return 0; +} + +static void __exit zswap_debugfs_exit(void) { } +#endif + +/********************************* +* module init and exit +**********************************/ +static int __init init_zswap(void) +{ + if (!zswap_enabled) + return 0; + + pr_info("loading zswap\n"); + if (zswap_entry_cache_create()) { + pr_err("entry cache creation failed\n"); + goto error; + } + if (zswap_comp_init()) { + pr_err("compressor initialization failed\n"); + goto compfail; + } + if (zswap_cpu_init()) { + pr_err("per-cpu initialization failed\n"); + goto pcpufail; + } + frontswap_register_ops(&zswap_frontswap_ops); + if (zswap_debugfs_init()) + pr_warn("debugfs initialization failed\n"); + return 0; +pcpufail: + zswap_comp_exit(); +compfail: + zswap_entry_cache_destory(); +error: + return -ENOMEM; +} +/* must be late so crypto has time to come up */ +late_initcall(init_zswap); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>"); +MODULE_DESCRIPTION("Compressed cache for swap pages"); |