cregit-Linux how code gets into the kernel

Release 4.11 mm/zswap.c

Directory: mm
/*
 * 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/zpool.h>

#include <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>

/*********************************
* statistics
**********************************/
/* Total bytes used by the compressed storage */

static u64 zswap_pool_total_size;
/* 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
**********************************/


#define ZSWAP_PARAM_UNSET ""

/* Enable/disable zswap (disabled by default) */

static bool zswap_enabled;
static int zswap_enabled_param_set(const char *,
				   const struct kernel_param *);

static struct kernel_param_ops zswap_enabled_param_ops = {
	.set =		zswap_enabled_param_set,
	.get =		param_get_bool,
};
module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);

/* Crypto compressor to use */

#define ZSWAP_COMPRESSOR_DEFAULT "lzo"

static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
static int zswap_compressor_param_set(const char *,
				      const struct kernel_param *);

static struct kernel_param_ops zswap_compressor_param_ops = {
	.set =		zswap_compressor_param_set,
	.get =		param_get_charp,
	.free =		param_free_charp,
};
module_param_cb(compressor, &zswap_compressor_param_ops,
		&zswap_compressor, 0644);

/* Compressed storage zpool to use */

#define ZSWAP_ZPOOL_DEFAULT "zbud"

static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
static int zswap_zpool_param_set(const char *, const struct kernel_param *);

static struct kernel_param_ops zswap_zpool_param_ops = {
	.set =		zswap_zpool_param_set,
	.get =		param_get_charp,
	.free =		param_free_charp,
};
module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);

/* 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);

/*********************************
* data structures
**********************************/


struct zswap_pool {
	
struct zpool *zpool;
	
struct crypto_comp * __percpu *tfm;
	
struct kref kref;
	
struct list_head list;
	
struct work_struct work;
	
struct hlist_node node;
	
char tfm_name[CRYPTO_MAX_ALG_NAME];
};

/*
 * 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
 * offset - the swap offset for the entry.  Index into the red-black tree.
 * refcount - the number of outstanding reference to the entry. This is needed
 *            to protect against premature freeing of the entry by code
 *            concurrent 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.
 * length - the length in bytes of the compressed page data.  Needed during
 *          decompression
 * pool - the zswap_pool the entry's data is in
 * handle - zpool allocation handle that stores the compressed page data
 */

struct zswap_entry {
	
struct rb_node rbnode;
	
pgoff_t offset;
	
int refcount;
	
unsigned int length;
	
struct zswap_pool *pool;
	
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;
};


static struct zswap_tree *zswap_trees[MAX_SWAPFILES];

/* RCU-protected iteration */
static LIST_HEAD(zswap_pools);
/* protects zswap_pools list modification */
static DEFINE_SPINLOCK(zswap_pools_lock);
/* pool counter to provide unique names to zpool */

static atomic_t zswap_pools_count = ATOMIC_INIT(0);

/* used by param callback function */

static bool zswap_init_started;

/* fatal error during init */

static bool zswap_init_failed;

/* init completed, but couldn't create the initial pool */

static bool zswap_has_pool;

/*********************************
* helpers and fwd declarations
**********************************/


#define zswap_pool_debug(msg, p)				\
	pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
                 zpool_get_type((p)->zpool))

static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
static int zswap_pool_get(struct zswap_pool *pool);
static void zswap_pool_put(struct zswap_pool *pool);


static const struct zpool_ops zswap_zpool_ops = {
	.evict = zswap_writeback_entry
};


static bool zswap_is_full(void) { return totalram_pages * zswap_max_pool_percent / 100 < DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE); }

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static void zswap_update_total_size(void) { struct zswap_pool *pool; u64 total = 0; rcu_read_lock(); list_for_each_entry_rcu(pool, &zswap_pools, list) total += zpool_get_total_size(pool->zpool); rcu_read_unlock(); zswap_pool_total_size = total; }

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/********************************* * zswap entry functions **********************************/ static struct kmem_cache *zswap_entry_cache;
static int __init zswap_entry_cache_create(void) { zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); return zswap_entry_cache == NULL; }

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static void __init zswap_entry_cache_destroy(void) { kmem_cache_destroy(zswap_entry_cache); }

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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; RB_CLEAR_NODE(&entry->rbnode); return entry; }

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static void zswap_entry_cache_free(struct zswap_entry *entry) { kmem_cache_free(zswap_entry_cache, entry); }

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/********************************* * 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; }

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/* * 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; }

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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); } }

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/* * Carries out the common pattern of freeing and entry's zpool allocation, * freeing the entry itself, and decrementing the number of stored pages. */
static void zswap_free_entry(struct zswap_entry *entry) { zpool_free(entry->pool->zpool, entry->handle); zswap_pool_put(entry->pool); zswap_entry_cache_free(entry); atomic_dec(&zswap_stored_pages); zswap_update_total_size(); }

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/* caller must hold the tree lock */
static void zswap_entry_get(struct zswap_entry *entry) { entry->refcount++; }

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/* 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(entry); } }

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/* 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; entry = zswap_rb_search(root, offset); if (entry) zswap_entry_get(entry); return entry; }

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/********************************* * per-cpu code **********************************/ static DEFINE_PER_CPU(u8 *, zswap_dstmem);
static int zswap_dstmem_prepare(unsigned int cpu) { u8 *dst; dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); if (!dst) { pr_err("can't allocate compressor buffer\n"); return -ENOMEM; } per_cpu(zswap_dstmem, cpu) = dst; return 0; }

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static int zswap_dstmem_dead(unsigned int cpu) { u8 *dst; dst = per_cpu(zswap_dstmem, cpu); kfree(dst); per_cpu(zswap_dstmem, cpu) = NULL; return 0; }

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static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_comp *tfm; if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu))) return 0; tfm = crypto_alloc_comp(pool->tfm_name, 0, 0); if (IS_ERR_OR_NULL(tfm)) { pr_err("could not alloc crypto comp %s : %ld\n", pool->tfm_name, PTR_ERR(tfm)); return -ENOMEM; } *per_cpu_ptr(pool->tfm, cpu) = tfm; return 0; }

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static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node) { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_comp *tfm; tfm = *per_cpu_ptr(pool->tfm, cpu); if (!IS_ERR_OR_NULL(tfm)) crypto_free_comp(tfm); *per_cpu_ptr(pool->tfm, cpu) = NULL; return 0; }

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/********************************* * pool functions **********************************/
static struct zswap_pool *__zswap_pool_current(void) { struct zswap_pool *pool; pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list); WARN_ONCE(!pool && zswap_has_pool, "%s: no page storage pool!\n", __func__); return pool; }

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static struct zswap_pool *zswap_pool_current(void) { assert_spin_locked(&zswap_pools_lock); return __zswap_pool_current(); }

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static struct zswap_pool *zswap_pool_current_get(void) { struct zswap_pool *pool; rcu_read_lock(); pool = __zswap_pool_current(); if (!zswap_pool_get(pool)) pool = NULL; rcu_read_unlock(); return pool; }

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static struct zswap_pool *zswap_pool_last_get(void) { struct zswap_pool *pool, *last = NULL; rcu_read_lock(); list_for_each_entry_rcu(pool, &zswap_pools, list) last = pool; WARN_ONCE(!last && zswap_has_pool, "%s: no page storage pool!\n", __func__); if (!zswap_pool_get(last)) last = NULL; rcu_read_unlock(); return last; }

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/* type and compressor must be null-terminated */
static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor) { struct zswap_pool *pool; assert_spin_locked(&zswap_pools_lock); list_for_each_entry_rcu(pool, &zswap_pools, list) { if (strcmp(pool->tfm_name, compressor)) continue; if (strcmp(zpool_get_type(pool->zpool), type)) continue; /* if we can't get it, it's about to be destroyed */ if (!zswap_pool_get(pool)) continue; return pool; } return NULL; }

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static struct zswap_pool *zswap_pool_create(char *type, char *compressor) { struct zswap_pool *pool; char name[38]; /* 'zswap' + 32 char (max) num + \0 */ gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; int ret; if (!zswap_has_pool) { /* if either are unset, pool initialization failed, and we * need both params to be set correctly before trying to * create a pool. */ if (!strcmp(type, ZSWAP_PARAM_UNSET)) return NULL; if (!strcmp(compressor, ZSWAP_PARAM_UNSET)) return NULL; } pool = kzalloc(sizeof(*pool), GFP_KERNEL); if (!pool) { pr_err("pool alloc failed\n"); return NULL; } /* unique name for each pool specifically required by zsmalloc */ snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count)); pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops); if (!pool->zpool) { pr_err("%s zpool not available\n", type); goto error; } pr_debug("using %s zpool\n", zpool_get_type(pool->zpool)); strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name)); pool->tfm = alloc_percpu(struct crypto_comp *); if (!pool->tfm) { pr_err("percpu alloc failed\n"); goto error; } ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); if (ret) goto error; pr_debug("using %s compressor\n", pool->tfm_name); /* being the current pool takes 1 ref; this func expects the * caller to always add the new pool as the current pool */ kref_init(&pool->kref); INIT_LIST_HEAD(&pool->list); zswap_pool_debug("created", pool); return pool; error: free_percpu(pool->tfm); if (pool->zpool) zpool_destroy_pool(pool->zpool); kfree(pool); return NULL; }

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static __init struct zswap_pool *__zswap_pool_create_fallback(void) { bool has_comp, has_zpool; has_comp = crypto_has_comp(zswap_compressor, 0, 0); if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) { pr_err("compressor %s not available, using default %s\n", zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT); param_free_charp(&zswap_compressor); zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; has_comp = crypto_has_comp(zswap_compressor, 0, 0); } if (!has_comp) { pr_err("default compressor %s not available\n", zswap_compressor); param_free_charp(&zswap_compressor); zswap_compressor = ZSWAP_PARAM_UNSET; } has_zpool = zpool_has_pool(zswap_zpool_type); if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) { pr_err("zpool %s not available, using default %s\n", zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT); param_free_charp(&zswap_zpool_type); zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT; has_zpool = zpool_has_pool(zswap_zpool_type); } if (!has_zpool) { pr_err("default zpool %s not available\n", zswap_zpool_type); param_free_charp(&zswap_zpool_type); zswap_zpool_type = ZSWAP_PARAM_UNSET; } if (!has_comp || !has_zpool) return NULL; return zswap_pool_create(zswap_zpool_type, zswap_compressor);
} static void zswap_pool_destroy(struct zswap_pool *pool) { zswap_pool_debug("destroying", pool); cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); free_percpu(pool->tfm); zpool_destroy_pool(pool->zpool); kfree(pool); }

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static int __must_check zswap_pool_get(struct zswap_pool *pool) { if (!pool) return 0; return kref_get_unless_zero(&pool->kref); }

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static void __zswap_pool_release(struct work_struct *work) { struct zswap_pool *pool = container_of(work, typeof(*pool), work); synchronize_rcu(); /* nobody should have been able to get a kref... */ WARN_ON(kref_get_unless_zero(&pool->kref)); /* pool is now off zswap_pools list and has no references. */ zswap_pool_destroy(pool); }

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static void __zswap_pool_empty(struct kref *kref) { struct zswap_pool *pool; pool = container_of(kref, typeof(*pool), kref); spin_lock(&zswap_pools_lock); WARN_ON(pool == zswap_pool_current()); list_del_rcu(&pool->list); INIT_WORK(&pool->work, __zswap_pool_release); schedule_work(&pool->work); spin_unlock(&zswap_pools_lock); }

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static void zswap_pool_put(struct zswap_pool *pool) { kref_put(&pool->kref, __zswap_pool_empty); }

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/********************************* * param callbacks **********************************/ /* val must be a null-terminated string */
static int __zswap_param_set(const char *val, const struct kernel_param *kp, char *type, char *compressor) { struct zswap_pool *pool, *put_pool = NULL; char *s = strstrip((char *)val); int ret; if (zswap_init_failed) { pr_err("can't set param, initialization failed\n"); return -ENODEV; } /* no change required */ if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool) return 0; /* if this is load-time (pre-init) param setting, * don't create a pool; that's done during init. */ if (!zswap_init_started) return param_set_charp(s, kp); if (!type) { if (!zpool_has_pool(s)) { pr_err("zpool %s not available\n", s); return -ENOENT; } type = s; } else if (!compressor) { if (!crypto_has_comp(s, 0, 0)) { pr_err("compressor %s not available\n", s); return -ENOENT; } compressor = s; } else { WARN_ON(1); return -EINVAL; } spin_lock(&zswap_pools_lock); pool = zswap_pool_find_get(type, compressor); if (pool) { zswap_pool_debug("using existing", pool); WARN_ON(pool == zswap_pool_current()); list_del_rcu(&pool->list); } spin_unlock(&zswap_pools_lock); if (!pool) pool = zswap_pool_create(type, compressor); if (pool) ret = param_set_charp(s, kp); else ret = -EINVAL; spin_lock(&zswap_pools_lock); if (!ret) { put_pool = zswap_pool_current(); list_add_rcu(&pool->list, &zswap_pools); zswap_has_pool = true; } else if (pool) { /* add the possibly pre-existing pool to the end of the pools * list; if it's new (and empty) then it'll be removed and * destroyed by the put after we drop the lock */ list_add_tail_rcu(&pool->list, &zswap_pools); put_pool = pool; } spin_unlock(&zswap_pools_lock); if (!zswap_has_pool && !pool) { /* if initial pool creation failed, and this pool creation also * failed, maybe both compressor and zpool params were bad. * Allow changing this param, so pool creation will succeed * when the other param is changed. We already verified this * param is ok in the zpool_has_pool() or crypto_has_comp() * checks above. */ ret = param_set_charp(s, kp); } /* drop the ref from either the old current pool, * or the new pool we failed to add */ if (put_pool) zswap_pool_put(put_pool); return ret; }

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static int zswap_compressor_param_set(const char *val, const struct kernel_param *kp) { return __zswap_param_set(val, kp, zswap_zpool_type, NULL); }

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static int zswap_zpool_param_set(const char *val, const struct kernel_param *kp) { return __zswap_param_set(val, kp, NULL, zswap_compressor); }

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Dan Streetman29100.00%1100.00%
Total29100.00%1100.00%


static int zswap_enabled_param_set(const char *val, const struct kernel_param *kp) { if (zswap_init_failed) { pr_err("can't enable, initialization failed\n"); return -ENODEV; } if (!zswap_has_pool && zswap_init_started) { pr_err("can't enable, no pool configured\n"); return -ENODEV; } return param_set_bool(val, kp); }

Contributors

PersonTokensPropCommitsCommitProp
Dan Streetman58100.00%2100.00%
Total58100.00%2100.00%

/********************************* * writeback code **********************************/ /* return enum for zswap_get_swap_cache_page */ enum zswap_get_swap_ret { ZSWAP_SWAPCACHE_NEW, ZSWAP_SWAPCACHE_EXIST, ZSWAP_SWAPCACHE_FAIL, }; /* * 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 ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated, * the new page is added to swapcache and locked * Returns ZSWAP_SWAPCACHE_FAIL on error */
static int zswap_get_swap_cache_page(swp_entry_t entry, struct page **retpage) { bool page_was_allocated; *retpage = __read_swap_cache_async(entry, GFP_KERNEL, NULL, 0, &page_was_allocated); if (page_was_allocated) return ZSWAP_SWAPCACHE_NEW; if (!*retpage) return ZSWAP_SWAPCACHE_FAIL; return ZSWAP_SWAPCACHE_EXIST; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings4074.07%133.33%
Dmitry Safonov1324.07%133.33%
Weijie Yang11.85%133.33%
Total54100.00%3100.00%

/* * 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 zpool *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; struct crypto_comp *tfm; u8 *src, *dst; unsigned int dlen; int ret; struct writeback_control wbc = { .sync_mode = WB_SYNC_NONE, }; /* extract swpentry from data */ zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO); swpentry = zhdr->swpentry; /* here */ zpool_unmap_handle(pool, handle); tree = zswap_trees[swp_type(swpentry)]; offset = swp_offset(swpentry); /* find and ref zswap entry */ spin_lock(&tree->lock); entry = zswap_entry_find_get(&tree->rbroot, offset); if (!entry) { /* entry was invalidated */ spin_unlock(&tree->lock); return 0; } 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_FAIL: /* no memory or invalidate happened */ ret = -ENOMEM; goto fail; case ZSWAP_SWAPCACHE_EXIST: /* page is already in the swap cache, ignore for now */ put_page(page); ret = -EEXIST; goto fail; case ZSWAP_SWAPCACHE_NEW: /* page is locked */ /* decompress */ dlen = PAGE_SIZE; src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO) + sizeof(struct zswap_header); dst = kmap_atomic(page); tfm = *get_cpu_ptr(entry->pool->tfm); ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen); put_cpu_ptr(entry->pool->tfm); kunmap_atomic(dst); zpool_unmap_handle(entry->pool->zpool, entry->handle); BUG_ON(ret); BUG_ON(dlen != PAGE_SIZE); /* page is up to date */ SetPageUptodate(page); } /* move it to the tail of the inactive list after end_writeback */ SetPageReclaim(page); /* start writeback */ __swap_writepage(page, &wbc, end_swap_bio_write); put_page(page); zswap_written_back_pages++; spin_lock(&tree->lock); /* drop local reference */ zswap_entry_put(tree, 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 (entry == zswap_rb_search(&tree->rbroot, offset)) zswap_entry_put(tree, entry); spin_unlock(&tree->lock); 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); zswap_entry_put(tree, entry); spin_unlock(&tree->lock); end: return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings35280.73%114.29%
Dan Streetman4710.78%228.57%
Weijie Yang358.03%342.86%
Kirill A. Shutemov20.46%114.29%
Total436100.00%7100.00%


static int zswap_shrink(void) { struct zswap_pool *pool; int ret; pool = zswap_pool_last_get(); if (!pool) return -ENOENT; ret = zpool_shrink(pool->zpool, 1, NULL); zswap_pool_put(pool); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Dan Streetman51100.00%1100.00%
Total51100.00%1100.00%

/********************************* * 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; struct crypto_comp *tfm; int ret; unsigned int dlen = PAGE_SIZE, len; unsigned long handle; char *buf; u8 *src, *dst; struct zswap_header *zhdr; if (!zswap_enabled || !tree) { ret = -ENODEV; goto reject; } /* reclaim space if needed */ if (zswap_is_full()) { zswap_pool_limit_hit++; if (zswap_shrink()) { 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; } /* if entry is successfully added, it keeps the reference */ entry->pool = zswap_pool_current_get(); if (!entry->pool) { ret = -EINVAL; goto freepage; } /* compress */ dst = get_cpu_var(zswap_dstmem); tfm = *get_cpu_ptr(entry->pool->tfm); src = kmap_atomic(page); ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen); kunmap_atomic(src); put_cpu_ptr(entry->pool->tfm); if (ret) { ret = -EINVAL; goto put_dstmem; } /* store */ len = dlen + sizeof(struct zswap_header); ret = zpool_malloc(entry->pool->zpool, len, __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM, &handle); if (ret == -ENOSPC) { zswap_reject_compress_poor++; goto put_dstmem; } if (ret) { zswap_reject_alloc_fail++; goto put_dstmem; } zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW); zhdr->swpentry = swp_entry(type, offset); buf = (u8 *)(zhdr + 1); memcpy(buf, dst, dlen); zpool_unmap_handle(entry->pool->zpool, 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 */ zswap_rb_erase(&tree->rbroot, dupentry); zswap_entry_put(tree, dupentry); } } while (ret == -EEXIST); spin_unlock(&tree->lock); /* update stats */ atomic_inc(&zswap_stored_pages); zswap_update_total_size(); return 0; put_dstmem: put_cpu_var(zswap_dstmem); zswap_pool_put(entry->pool); freepage: zswap_entry_cache_free(entry); reject: return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings38778.34%116.67%
Dan Streetman10220.65%350.00%
Weijie Yang30.61%116.67%
Mel Gorman20.40%116.67%
Total494100.00%6100.00%

/* * 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; struct crypto_comp *tfm; u8 *src, *dst; unsigned int dlen; int ret; /* find */ spin_lock(&tree->lock); entry = zswap_entry_find_get(&tree->rbroot, offset); if (!entry) { /* entry was written back */ spin_unlock(&tree->lock); return -1; } spin_unlock(&tree->lock); /* decompress */ dlen = PAGE_SIZE; src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO) + sizeof(struct zswap_header); dst = kmap_atomic(page); tfm = *get_cpu_ptr(entry->pool->tfm); ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen); put_cpu_ptr(entry->pool->tfm); kunmap_atomic(dst); zpool_unmap_handle(entry->pool->zpool, entry->handle); BUG_ON(ret); spin_lock(&tree->lock); zswap_entry_put(tree, entry); spin_unlock(&tree->lock); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings18280.18%125.00%
Dan Streetman4218.50%250.00%
Weijie Yang31.32%125.00%
Total227100.00%4100.00%

/* 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; /* 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 */ zswap_rb_erase(&tree->rbroot, entry); /* drop the initial reference from entry creation */ zswap_entry_put(tree, entry); spin_unlock(&tree->lock); }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings8794.57%150.00%
Weijie Yang55.43%150.00%
Total92100.00%2100.00%

/* 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 zswap_entry *entry, *n; if (!tree) return; /* walk the tree and free everything */ spin_lock(&tree->lock); rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode) zswap_free_entry(entry); tree->rbroot = RB_ROOT; spin_unlock(&tree->lock); kfree(tree); zswap_trees[type] = NULL; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings6274.70%125.00%
Weijie Yang1315.66%250.00%
Cody P Schafer89.64%125.00%
Total83100.00%4100.00%


static void zswap_frontswap_init(unsigned type) { struct zswap_tree *tree; tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL); if (!tree) { pr_err("alloc failed, zswap disabled for swap type %d\n", type); return; } tree->rbroot = RB_ROOT; spin_lock_init(&tree->lock); zswap_trees[type] = tree; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings5790.48%150.00%
MinChan Kim69.52%150.00%
Total63100.00%2100.00%

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_total_size", S_IRUGO, zswap_debugfs_root, &zswap_pool_total_size); debugfs_create_atomic_t("stored_pages", S_IRUGO, zswap_debugfs_root, &zswap_stored_pages); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings14698.65%150.00%
Dan Streetman21.35%150.00%
Total148100.00%2100.00%


static void __exit zswap_debugfs_exit(void) { debugfs_remove_recursive(zswap_debugfs_root); }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings14100.00%1100.00%
Total14100.00%1100.00%

#else
static int __init zswap_debugfs_init(void) { return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings12100.00%1100.00%
Total12100.00%1100.00%


static void __exit zswap_debugfs_exit(void) { }

Contributors

PersonTokensPropCommitsCommitProp
Seth Jennings8100.00%1100.00%
Total8100.00%1100.00%

#endif /********************************* * module init and exit **********************************/
static int __init init_zswap(void) { struct zswap_pool *pool; int ret; zswap_init_started = true; if (zswap_entry_cache_create()) { pr_err("entry cache creation failed\n"); goto cache_fail; } ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare", zswap_dstmem_prepare, zswap_dstmem_dead); if (ret) { pr_err("dstmem alloc failed\n"); goto dstmem_fail; } ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE, "mm/zswap_pool:prepare", zswap_cpu_comp_prepare, zswap_cpu_comp_dead); if (ret) goto hp_fail; pool = __zswap_pool_create_fallback(); if (pool) { pr_info("loaded using pool %s/%s\n", pool->tfm_name, zpool_get_type(pool->zpool)); list_add(&pool->list, &zswap_pools); zswap_has_pool = true; } else { pr_err("pool creation failed\n"); zswap_enabled = false; } frontswap_register_ops(&zswap_frontswap_ops); if (zswap_debugfs_init()) pr_warn("debugfs initialization failed\n"); return 0; hp_fail: cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE); dstmem_fail: zswap_entry_cache_destroy(); cache_fail: /* if built-in, we aren't unloaded on failure; don't allow use */ zswap_init_failed = true; zswap_enabled = false; return -ENOMEM; }

Contributors

PersonTokensPropCommitsCommitProp
Dan Streetman7239.34%444.44%
Seth Jennings6636.07%111.11%
Sebastian Andrzej Siewior4323.50%222.22%
Fabian Frederick10.55%111.11%
MinChan Kim10.55%111.11%
Total183100.00%9100.00%

/* must be late so crypto has time to come up */ late_initcall(init_zswap); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>"); MODULE_DESCRIPTION("Compressed cache for swap pages");

Overall Contributors

PersonTokensPropCommitsCommitProp
Dan Streetman223846.57%1244.44%
Seth Jennings210543.80%27.41%
Weijie Yang2715.64%414.81%
Sebastian Andrzej Siewior1473.06%27.41%
Dmitry Safonov130.27%13.70%
MinChan Kim90.19%13.70%
Cody P Schafer80.17%13.70%
Eric Dumazet60.12%13.70%
Mel Gorman40.08%13.70%
Fabian Frederick30.06%13.70%
Kirill A. Shutemov20.04%13.70%
Total4806100.00%27100.00%
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