|
|
@@ -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");
|
Linus Torvalds