[PATCHv5 7/8] zswap: add swap page writeback support
Ric Mason
ric.masonn at gmail.com
Sat Feb 16 06:11:07 UTC 2013
On 02/14/2013 02:38 AM, Seth Jennings wrote:
> This patch adds support for evicting swap pages that are currently
> compressed in zswap to the swap device. This functionality is very
> important and make zswap a true cache in that, once the cache is full
> or can't grow due to memory pressure, the oldest pages can be moved
> out of zswap to the swap device so newer pages can be compressed and
> stored in zswap.
>
> This introduces a good amount of new code to guarantee coherency.
> Most notably, and LRU list is added to the zswap_tree structure,
> and refcounts are added to each entry to ensure that one code path
> doesn't free then entry while another code path is operating on it.
>
> Signed-off-by: Seth Jennings <sjenning at linux.vnet.ibm.com>
> ---
> mm/zswap.c | 530 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 510 insertions(+), 20 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index e77ab2f..6478262 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -36,6 +36,12 @@
> #include <linux/mempool.h>
> #include <linux/zsmalloc.h>
>
> +#include <linux/mm_types.h>
> +#include <linux/page-flags.h>
> +#include <linux/swapops.h>
> +#include <linux/writeback.h>
> +#include <linux/pagemap.h>
> +
> /*********************************
> * statistics
> **********************************/
> @@ -43,6 +49,8 @@
> static atomic_t zswap_pool_pages = ATOMIC_INIT(0);
> /* The number of compressed pages currently stored in zswap */
> static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
> +/* The number of outstanding pages awaiting writeback */
> +static atomic_t zswap_outstanding_writebacks = ATOMIC_INIT(0);
>
> /*
> * The statistics below are not protected from concurrent access for
> @@ -51,9 +59,13 @@ static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
> * certain event is occurring.
> */
> static u64 zswap_pool_limit_hit;
> +static u64 zswap_written_back_pages;
> static u64 zswap_reject_compress_poor;
> +static u64 zswap_writeback_attempted;
> +static u64 zswap_reject_tmppage_fail;
> static u64 zswap_reject_zsmalloc_fail;
> static u64 zswap_reject_kmemcache_fail;
> +static u64 zswap_saved_by_writeback;
> static u64 zswap_duplicate_entry;
>
> /*********************************
> @@ -82,6 +94,14 @@ static unsigned int zswap_max_compression_ratio = 80;
> module_param_named(max_compression_ratio,
> zswap_max_compression_ratio, uint, 0644);
>
> +/*
> + * Maximum number of outstanding writebacks allowed at any given time.
> + * This is to prevent decompressing an unbounded number of compressed
> + * pages into the swap cache all at once, and to help with writeback
> + * congestion.
> +*/
> +#define ZSWAP_MAX_OUTSTANDING_FLUSHES 64
> +
> /*********************************
> * compression functions
> **********************************/
> @@ -144,16 +164,47 @@ static void zswap_comp_exit(void)
> /*********************************
> * 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
> + * lru - links the entry into the lru list 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.
> + * type - the swap type for the entry. Used to map back to the zswap_tree
> + * structure that contains the entry.
> + * 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;
> + struct list_head lru;
> + int refcount;
> unsigned type;
> pgoff_t offset;
> unsigned long handle;
> unsigned int length;
> };
>
> +/*
> + * The tree lock in the zswap_tree struct protects a few things:
> + * - the rbtree
> + * - the lru list
> + * - the refcount field of each entry in the tree
> + */
> struct zswap_tree {
> struct rb_root rbroot;
> + struct list_head lru;
> spinlock_t lock;
> struct zs_pool *pool;
> };
> @@ -185,6 +236,8 @@ static inline struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
> entry = kmem_cache_alloc(zswap_entry_cache, gfp);
> if (!entry)
> return NULL;
> + INIT_LIST_HEAD(&entry->lru);
> + entry->refcount = 1;
> return entry;
> }
>
> @@ -193,6 +246,17 @@ static inline void zswap_entry_cache_free(struct zswap_entry *entry)
> kmem_cache_free(zswap_entry_cache, entry);
> }
>
> +static inline void zswap_entry_get(struct zswap_entry *entry)
> +{
> + entry->refcount++;
> +}
> +
> +static inline int zswap_entry_put(struct zswap_entry *entry)
> +{
> + entry->refcount--;
> + return entry->refcount;
> +}
> +
> /*********************************
> * rbtree functions
> **********************************/
> @@ -367,6 +431,333 @@ static struct zs_ops zswap_zs_ops = {
> .free = zswap_free_page
> };
>
> +
> +/*********************************
> +* helpers
> +**********************************/
> +
> +/*
> + * 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)
> +{
> + zs_free(tree->pool, entry->handle);
> + zswap_entry_cache_free(entry);
> + atomic_dec(&zswap_stored_pages);
> +}
> +
> +/*********************************
> +* writeback code
> +**********************************/
> +static void zswap_end_swap_write(struct bio *bio, int err)
> +{
> + end_swap_bio_write(bio, err);
> + atomic_dec(&zswap_outstanding_writebacks);
> + zswap_written_back_pages++;
> +}
> +
> +/* 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;
> + 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 and 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 zswap_entry *entry)
> +{
> + unsigned long type = entry->type;
> + struct zswap_tree *tree = zswap_trees[type];
> + struct page *page;
> + swp_entry_t swpentry;
> + u8 *src, *dst;
> + unsigned int dlen;
> + int ret;
> + struct writeback_control wbc = {
> + .sync_mode = WB_SYNC_NONE,
> + };
> +
> + /* get/allocate page in the swap cache */
> + swpentry = swp_entry(type, entry->offset);
> +
> + /* try to allocate swap cache page */
> + switch (zswap_get_swap_cache_page(swpentry, &page)) {
> +
> + case ZSWAP_SWAPCACHE_NOMEM: /* no memory */
> + return -ENOMEM;
> + break; /* not reached */
> +
> + case ZSWAP_SWAPCACHE_EXIST: /* page is unlocked */
> + /* page is already in the swap cache, ignore for now */
> + return -EEXIST;
> + break; /* not reached */
> +
> + case ZSWAP_SWAPCACHE_NEW: /* page is locked */
> + /* decompress */
> + dlen = PAGE_SIZE;
> + src = zs_map_object(tree->pool, entry->handle, ZS_MM_RO);
> + dst = kmap_atomic(page);
> + ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
> + dst, &dlen);
> + kunmap_atomic(dst);
> + zs_unmap_object(tree->pool, entry->handle);
> + BUG_ON(ret);
> + BUG_ON(dlen != PAGE_SIZE);
> +
> + /* page is up to date */
> + SetPageUptodate(page);
> + }
> +
> + /* start writeback */
> + SetPageReclaim(page);
> + /*
> + * Return value is ignored here because it doesn't change anything
> + * for us. Page is returned unlocked.
> + */
> + (void)__swap_writepage(page, &wbc, zswap_end_swap_write);
> + page_cache_release(page);
> + atomic_inc(&zswap_outstanding_writebacks);
> +
> + return 0;
> +}
> +
> +/*
> + * Attempts to free nr of entries via writeback to the swap device.
> + * The number of entries that were actually freed is returned.
> + */
> +static int zswap_writeback_entries(unsigned type, int nr)
> +{
> + struct zswap_tree *tree = zswap_trees[type];
> + struct zswap_entry *entry;
> + int i, ret, refcount, freed_nr = 0;
> +
> + /*
> + * This limits is arbitrary for now until a better
> + * policy can be implemented. This is so we don't
> + * eat all of RAM decompressing pages for writeback.
> + */
> + if (atomic_read(&zswap_outstanding_writebacks) >
> + ZSWAP_MAX_OUTSTANDING_FLUSHES)
> + return 0;
> +
> + for (i = 0; i < nr; i++) {
> + spin_lock(&tree->lock);
> +
> + /* dequeue from lru */
> + if (list_empty(&tree->lru)) {
> + spin_unlock(&tree->lock);
> + break;
> + }
> + entry = list_first_entry(&tree->lru,
> + struct zswap_entry, lru);
> + list_del_init(&entry->lru);
> +
> + /* so invalidate doesn't free the entry from under us */
> + zswap_entry_get(entry);
> +
> + spin_unlock(&tree->lock);
> +
> + /* attempt writeback */
> + ret = zswap_writeback_entry(entry);
> +
> + spin_lock(&tree->lock);
> +
> + /* drop reference from above */
> + refcount = zswap_entry_put(entry);
> +
> + if (!ret)
> + /* 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 or writeback failed;
> + * do not free entry, add back to LRU
> + * (2) refcount is 0, (usual case) not invalidate yet;
> + * free entry
> + * (3) refcount is -1, invalidate happened during writeback;
> + * free entry
> + */
> + if (refcount > 0)
> + list_add(&entry->lru, &tree->lru);
> + spin_unlock(&tree->lock);
> +
> + if (refcount <= 0) {
> + /* free the entry */
> + if (refcount == 0)
> + /* no invalidate yet, remove from rbtree */
> + rb_erase(&entry->rbnode, &tree->rbroot);
> + zswap_free_entry(tree, entry);
> + freed_nr++;
> + }
> +
> + if (atomic_read(&zswap_outstanding_writebacks) >
> + ZSWAP_MAX_OUTSTANDING_FLUSHES)
> + break;
> + }
> + return freed_nr++;
> +}
> +
> +/*******************************************
> +* page pool for temporary compression result
> +********************************************/
> +#define ZSWAP_TMPPAGE_POOL_PAGES 16
Why not the number of online cpu?
> +static LIST_HEAD(zswap_tmppage_list);
> +static DEFINE_SPINLOCK(zswap_tmppage_lock);
> +
> +static void zswap_tmppage_pool_destroy(void)
> +{
> + struct page *page, *tmppage;
> +
> + spin_lock(&zswap_tmppage_lock);
> + list_for_each_entry_safe(page, tmppage, &zswap_tmppage_list, lru) {
> + list_del(&page->lru);
> + __free_pages(page, 1);
> + }
> + spin_unlock(&zswap_tmppage_lock);
> +}
> +
> +static int zswap_tmppage_pool_create(void)
> +{
> + int i;
> + struct page *page;
> +
> + for (i = 0; i < ZSWAP_TMPPAGE_POOL_PAGES; i++) {
> + page = alloc_pages(GFP_KERNEL, 1);
> + if (!page) {
> + zswap_tmppage_pool_destroy();
> + return -ENOMEM;
> + }
> + spin_lock(&zswap_tmppage_lock);
> + list_add(&page->lru, &zswap_tmppage_list);
> + spin_unlock(&zswap_tmppage_lock);
> + }
> + return 0;
> +}
> +
> +static inline struct page *zswap_tmppage_alloc(void)
> +{
> + struct page *page;
> +
> + spin_lock(&zswap_tmppage_lock);
> + if (list_empty(&zswap_tmppage_list)) {
> + spin_unlock(&zswap_tmppage_lock);
> + return NULL;
> + }
> + page = list_first_entry(&zswap_tmppage_list, struct page, lru);
> + list_del(&page->lru);
> + spin_unlock(&zswap_tmppage_lock);
> + return page;
> +}
> +
> +static inline void zswap_tmppage_free(struct page *page)
> +{
> + spin_lock(&zswap_tmppage_lock);
> + list_add(&page->lru, &zswap_tmppage_list);
> + spin_unlock(&zswap_tmppage_lock);
> +}
> +
> /*********************************
> * frontswap hooks
> **********************************/
> @@ -380,7 +771,9 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> unsigned int dlen = PAGE_SIZE;
> unsigned long handle;
> char *buf;
> - u8 *src, *dst;
> + u8 *src, *dst, *tmpdst;
> + struct page *tmppage;
> + bool writeback_attempted = 0;
>
> if (!tree) {
> ret = -ENODEV;
> @@ -394,12 +787,12 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> kunmap_atomic(src);
> if (ret) {
> ret = -EINVAL;
> - goto putcpu;
> + goto freepage;
> }
> if ((dlen * 100 / PAGE_SIZE) > zswap_max_compression_ratio) {
> zswap_reject_compress_poor++;
> ret = -E2BIG;
> - goto putcpu;
> + goto freepage;
> }
>
> /* store */
> @@ -407,15 +800,46 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> __GFP_NORETRY | __GFP_HIGHMEM | __GFP_NOMEMALLOC |
> __GFP_NOWARN);
> if (!handle) {
> - zswap_reject_zsmalloc_fail++;
> - ret = -ENOMEM;
> - goto putcpu;
> + zswap_writeback_attempted++;
> + /*
> + * Copy compressed buffer out of per-cpu storage so
> + * we can re-enable preemption.
> + */
Why re-enable preemption is very important?
> + tmppage = zswap_tmppage_alloc();
> + if (!tmppage) {
> + zswap_reject_tmppage_fail++;
> + ret = -ENOMEM;
> + goto freepage;
> + }
> + writeback_attempted = 1;
> + tmpdst = page_address(tmppage);
> + memcpy(tmpdst, dst, dlen);
> + dst = tmpdst;
> + put_cpu_var(zswap_dstmem);
> +
> + /* try to free up some space */
> + /* TODO: replace with more targeted policy */
> + zswap_writeback_entries(type, 16);
> + /* try again, allowing wait */
> + handle = zs_malloc(tree->pool, dlen,
> + __GFP_NORETRY | __GFP_HIGHMEM | __GFP_NOMEMALLOC |
> + __GFP_NOWARN);
> + if (!handle) {
> + /* still no space, fail */
> + zswap_reject_zsmalloc_fail++;
> + ret = -ENOMEM;
> + goto freepage;
> + }
> + zswap_saved_by_writeback++;
> }
>
> buf = zs_map_object(tree->pool, handle, ZS_MM_WO);
> memcpy(buf, dst, dlen);
> zs_unmap_object(tree->pool, handle);
> - put_cpu_var(zswap_dstmem);
> + if (writeback_attempted)
> + zswap_tmppage_free(tmppage);
> + else
> + put_cpu_var(zswap_dstmem);
>
> /* allocate entry */
> entry = zswap_entry_cache_alloc(GFP_KERNEL);
> @@ -438,16 +862,17 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
> ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
> if (ret == -EEXIST) {
> zswap_duplicate_entry++;
> -
> - /* remove from rbtree */
> + /* remove from rbtree and lru */
> rb_erase(&dupentry->rbnode, &tree->rbroot);
> -
> - /* free */
> - zs_free(tree->pool, dupentry->handle);
> - zswap_entry_cache_free(dupentry);
> - atomic_dec(&zswap_stored_pages);
> + if (!list_empty(&dupentry->lru))
> + list_del_init(&dupentry->lru);
> + if (!zswap_entry_put(dupentry)) {
> + /* free */
> + zswap_free_entry(tree, dupentry);
> + }
> }
> } while (ret == -EEXIST);
> + list_add_tail(&entry->lru, &tree->lru);
> spin_unlock(&tree->lock);
>
> /* update stats */
> @@ -455,8 +880,11 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
>
> return 0;
>
> -putcpu:
> - put_cpu_var(zswap_dstmem);
> +freepage:
> + if (writeback_attempted)
> + zswap_tmppage_free(tmppage);
> + else
> + put_cpu_var(zswap_dstmem);
> reject:
> return ret;
> }
> @@ -472,10 +900,21 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> struct zswap_entry *entry;
> u8 *src, *dst;
> unsigned int dlen;
> + 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 -1;
> + }
> + zswap_entry_get(entry);
> +
> + /* remove from lru */
> + if (!list_empty(&entry->lru))
> + list_del_init(&entry->lru);
> spin_unlock(&tree->lock);
>
> /* decompress */
> @@ -487,6 +926,24 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
> kunmap_atomic(dst);
> zs_unmap_object(tree->pool, entry->handle);
>
> + spin_lock(&tree->lock);
> + refcount = zswap_entry_put(entry);
> + if (likely(refcount)) {
> + list_add_tail(&entry->lru, &tree->lru);
> + 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;
> }
>
> @@ -495,19 +952,34 @@ 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 */
> + /* remove from rbtree and lru */
> rb_erase(&entry->rbnode, &tree->rbroot);
> + if (!list_empty(&entry->lru))
> + list_del_init(&entry->lru);
> +
> + /* 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 */
> - zs_free(tree->pool, entry->handle);
> - zswap_entry_cache_free(entry);
> - atomic_dec(&zswap_stored_pages);
> + zswap_free_entry(tree, entry);
> }
>
> /* invalidates all pages for the given swap type */
> @@ -531,6 +1003,7 @@ static void zswap_frontswap_invalidate_area(unsigned type)
> node = next;
> }
> tree->rbroot = RB_ROOT;
> + INIT_LIST_HEAD(&tree->lru);
> spin_unlock(&tree->lock);
> }
>
> @@ -546,6 +1019,7 @@ static void zswap_frontswap_init(unsigned type)
> if (!tree->pool)
> goto freetree;
> tree->rbroot = RB_ROOT;
> + INIT_LIST_HEAD(&tree->lru);
> spin_lock_init(&tree->lock);
> zswap_trees[type] = tree;
> return;
> @@ -581,20 +1055,30 @@ static int __init zswap_debugfs_init(void)
> if (!zswap_debugfs_root)
> return -ENOMEM;
>
> + debugfs_create_u64("saved_by_writeback", S_IRUGO,
> + zswap_debugfs_root, &zswap_saved_by_writeback);
> debugfs_create_u64("pool_limit_hit", S_IRUGO,
> zswap_debugfs_root, &zswap_pool_limit_hit);
> + debugfs_create_u64("reject_writeback_attempted", S_IRUGO,
> + zswap_debugfs_root, &zswap_writeback_attempted);
> + debugfs_create_u64("reject_tmppage_fail", S_IRUGO,
> + zswap_debugfs_root, &zswap_reject_tmppage_fail);
> debugfs_create_u64("reject_zsmalloc_fail", S_IRUGO,
> zswap_debugfs_root, &zswap_reject_zsmalloc_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_atomic_t("pool_pages", S_IRUGO,
> zswap_debugfs_root, &zswap_pool_pages);
> debugfs_create_atomic_t("stored_pages", S_IRUGO,
> zswap_debugfs_root, &zswap_stored_pages);
> + debugfs_create_atomic_t("outstanding_writebacks", S_IRUGO,
> + zswap_debugfs_root, &zswap_outstanding_writebacks);
>
> return 0;
> }
> @@ -629,6 +1113,10 @@ static int __init init_zswap(void)
> pr_err("page pool initialization failed\n");
> goto pagepoolfail;
> }
> + if (zswap_tmppage_pool_create()) {
> + pr_err("workmem pool initialization failed\n");
> + goto tmppoolfail;
> + }
> if (zswap_comp_init()) {
> pr_err("compressor initialization failed\n");
> goto compfail;
> @@ -644,6 +1132,8 @@ static int __init init_zswap(void)
> pcpufail:
> zswap_comp_exit();
> compfail:
> + zswap_tmppage_pool_destroy();
> +tmppoolfail:
> zswap_page_pool_destroy();
> pagepoolfail:
> zswap_entry_cache_destory();
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