1172 lines
30 KiB
C
1172 lines
30 KiB
C
/*
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* zswap.c - zswap driver file
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*
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* zswap is a backend for frontswap that takes pages that are in the
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* process of being swapped out and attempts to compress them and store
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* them in a RAM-based memory pool. This results in a significant I/O
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* reduction on the real swap device and, in the case of a slow swap
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* device, can also improve workload performance.
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*
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* Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/cpu.h>
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#include <linux/highmem.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include <linux/atomic.h>
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#include <linux/frontswap.h>
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#include <linux/rbtree.h>
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#include <linux/swap.h>
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#include <linux/crypto.h>
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#include <linux/mempool.h>
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#include <linux/zsmalloc.h>
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#include <linux/mm_types.h>
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#include <linux/page-flags.h>
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#include <linux/swapops.h>
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#include <linux/writeback.h>
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#include <linux/pagemap.h>
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/*********************************
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* statistics
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**********************************/
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/* Number of memory pages used by the compressed pool */
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atomic_t zswap_pool_pages = ATOMIC_INIT(0);
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/* The number of compressed pages currently stored in zswap */
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atomic_t zswap_stored_pages = ATOMIC_INIT(0);
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#ifdef CONFIG_ZSWAP_ENABLE_WRITEBACK
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/* The number of outstanding pages awaiting writeback */
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static atomic_t zswap_outstanding_writebacks = ATOMIC_INIT(0);
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#endif
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/*
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* The statistics below are not protected from concurrent access for
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* performance reasons so they may not be a 100% accurate. However,
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* they do provide useful information on roughly how many times a
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* certain event is occurring.
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*/
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static u64 zswap_pool_limit_hit;
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static u64 zswap_written_back_pages;
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static u64 zswap_reject_compress_poor;
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static u64 zswap_writeback_attempted;
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static u64 zswap_reject_tmppage_fail;
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static u64 zswap_reject_zsmalloc_fail;
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static u64 zswap_reject_kmemcache_fail;
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static u64 zswap_saved_by_writeback;
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static u64 zswap_duplicate_entry;
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/*********************************
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* tunables
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**********************************/
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/* Enable/disable zswap (enabled by default, fixed at boot for now) */
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static bool zswap_enabled = 1;
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module_param_named(enabled, zswap_enabled, bool, 0);
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/* Compressor to be used by zswap (fixed at boot for now) */
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#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
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static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
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module_param_named(compressor, zswap_compressor, charp, 0);
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/* The maximum percentage of memory that the compressed pool can occupy */
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static unsigned int zswap_max_pool_percent = 50;
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module_param_named(max_pool_percent,
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zswap_max_pool_percent, uint, 0644);
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/*
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* Maximum compression ratio, as as percentage, for an acceptable
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* compressed page. Any pages that do not compress by at least
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* this ratio will be rejected.
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*/
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static unsigned int zswap_max_compression_ratio = 80;
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module_param_named(max_compression_ratio,
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zswap_max_compression_ratio, uint, 0644);
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/*
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* Maximum number of outstanding writebacks allowed at any given time.
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* This is to prevent decompressing an unbounded number of compressed
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* pages into the swap cache all at once, and to help with writeback
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* congestion.
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*/
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#define ZSWAP_MAX_OUTSTANDING_FLUSHES 64
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/*********************************
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* compression functions
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**********************************/
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/* per-cpu compression transforms */
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static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
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enum comp_op {
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ZSWAP_COMPOP_COMPRESS,
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ZSWAP_COMPOP_DECOMPRESS
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};
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static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
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u8 *dst, unsigned int *dlen)
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{
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struct crypto_comp *tfm;
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int ret;
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tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
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switch (op) {
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case ZSWAP_COMPOP_COMPRESS:
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ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
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break;
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case ZSWAP_COMPOP_DECOMPRESS:
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ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
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break;
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default:
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ret = -EINVAL;
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}
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put_cpu();
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return ret;
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}
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static int __init zswap_comp_init(void)
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{
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if (!crypto_has_comp(zswap_compressor, 0, 0)) {
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pr_info("%s compressor not available\n", zswap_compressor);
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/* fall back to default compressor */
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zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
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if (!crypto_has_comp(zswap_compressor, 0, 0))
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/* can't even load the default compressor */
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return -ENODEV;
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}
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pr_info("using %s compressor\n", zswap_compressor);
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/* alloc percpu transforms */
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zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
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if (!zswap_comp_pcpu_tfms)
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return -ENOMEM;
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return 0;
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}
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static void zswap_comp_exit(void)
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{
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/* free percpu transforms */
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if (zswap_comp_pcpu_tfms)
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free_percpu(zswap_comp_pcpu_tfms);
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}
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/*********************************
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* data structures
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**********************************/
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/*
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* struct zswap_entry
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*
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* This structure contains the metadata for tracking a single compressed
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* page within zswap.
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*
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* rbnode - links the entry into red-black tree for the appropriate swap type
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* lru - links the entry into the lru list for the appropriate swap type
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* refcount - the number of outstanding reference to the entry. This is needed
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* to protect against premature freeing of the entry by code
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* concurent calls to load, invalidate, and writeback. The lock
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* for the zswap_tree structure that contains the entry must
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* be held while changing the refcount. Since the lock must
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* be held, there is no reason to also make refcount atomic.
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* type - the swap type for the entry. Used to map back to the zswap_tree
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* structure that contains the entry.
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* offset - the swap offset for the entry. Index into the red-black tree.
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* handle - zsmalloc allocation handle that stores the compressed page data
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* length - the length in bytes of the compressed page data. Needed during
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* decompression
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*/
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struct zswap_entry {
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struct rb_node rbnode;
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struct list_head lru;
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int refcount;
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pgoff_t offset;
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unsigned long handle;
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unsigned int length;
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};
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/*
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* The tree lock in the zswap_tree struct protects a few things:
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* - the rbtree
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* - the lru list
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* - the refcount field of each entry in the tree
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*/
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struct zswap_tree {
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struct rb_root rbroot;
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struct list_head lru;
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spinlock_t lock;
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struct zs_pool *pool;
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unsigned type;
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};
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static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
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/*********************************
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* zswap entry functions
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**********************************/
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#define ZSWAP_KMEM_CACHE_NAME "zswap_entry_cache"
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static struct kmem_cache *zswap_entry_cache;
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static inline int zswap_entry_cache_create(void)
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{
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zswap_entry_cache =
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kmem_cache_create(ZSWAP_KMEM_CACHE_NAME,
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sizeof(struct zswap_entry), 0, 0, NULL);
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return (zswap_entry_cache == NULL);
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}
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static inline void zswap_entry_cache_destory(void)
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{
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kmem_cache_destroy(zswap_entry_cache);
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}
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static inline struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
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{
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struct zswap_entry *entry;
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entry = kmem_cache_alloc(zswap_entry_cache, gfp);
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if (!entry)
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return NULL;
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INIT_LIST_HEAD(&entry->lru);
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entry->refcount = 1;
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return entry;
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}
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static inline void zswap_entry_cache_free(struct zswap_entry *entry)
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{
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kmem_cache_free(zswap_entry_cache, entry);
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}
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static inline void zswap_entry_get(struct zswap_entry *entry)
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{
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entry->refcount++;
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}
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static inline int zswap_entry_put(struct zswap_entry *entry)
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{
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entry->refcount--;
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return entry->refcount;
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}
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/*********************************
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* rbtree functions
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**********************************/
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static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
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{
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struct rb_node *node = root->rb_node;
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struct zswap_entry *entry;
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while (node) {
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entry = rb_entry(node, struct zswap_entry, rbnode);
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if (entry->offset > offset)
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node = node->rb_left;
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else if (entry->offset < offset)
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node = node->rb_right;
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else
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return entry;
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}
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return NULL;
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}
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/*
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* In the case that a entry with the same offset is found, it a pointer to
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* the existing entry is stored in dupentry and the function returns -EEXIST
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*/
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static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
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struct zswap_entry **dupentry)
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{
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struct rb_node **link = &root->rb_node, *parent = NULL;
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struct zswap_entry *myentry;
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while (*link) {
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parent = *link;
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myentry = rb_entry(parent, struct zswap_entry, rbnode);
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if (myentry->offset > entry->offset)
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link = &(*link)->rb_left;
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else if (myentry->offset < entry->offset)
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link = &(*link)->rb_right;
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else {
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*dupentry = myentry;
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return -EEXIST;
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}
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}
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rb_link_node(&entry->rbnode, parent, link);
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rb_insert_color(&entry->rbnode, root);
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return 0;
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}
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/*********************************
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* per-cpu code
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**********************************/
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static DEFINE_PER_CPU(u8 *, zswap_dstmem);
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static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
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{
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struct crypto_comp *tfm;
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u8 *dst;
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switch (action) {
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case CPU_UP_PREPARE:
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tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
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if (IS_ERR(tfm)) {
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pr_err("can't allocate compressor transform\n");
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return NOTIFY_BAD;
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}
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*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
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dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
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if (!dst) {
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pr_err("can't allocate compressor buffer\n");
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crypto_free_comp(tfm);
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*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
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return NOTIFY_BAD;
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}
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per_cpu(zswap_dstmem, cpu) = dst;
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break;
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case CPU_DEAD:
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case CPU_UP_CANCELED:
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tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
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if (tfm) {
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crypto_free_comp(tfm);
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*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
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}
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dst = per_cpu(zswap_dstmem, cpu);
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if (dst) {
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kfree(dst);
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per_cpu(zswap_dstmem, cpu) = NULL;
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}
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break;
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default:
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break;
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}
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return NOTIFY_OK;
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}
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static int zswap_cpu_notifier(struct notifier_block *nb,
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unsigned long action, void *pcpu)
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{
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unsigned long cpu = (unsigned long)pcpu;
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return __zswap_cpu_notifier(action, cpu);
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}
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static struct notifier_block zswap_cpu_notifier_block = {
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.notifier_call = zswap_cpu_notifier
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};
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static int zswap_cpu_init(void)
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{
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unsigned long cpu;
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get_online_cpus();
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for_each_online_cpu(cpu)
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if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
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goto cleanup;
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register_cpu_notifier(&zswap_cpu_notifier_block);
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put_online_cpus();
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return 0;
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cleanup:
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for_each_online_cpu(cpu)
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__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
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put_online_cpus();
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return -ENOMEM;
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}
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/*********************************
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* zsmalloc callbacks
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**********************************/
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static mempool_t *zswap_page_pool;
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static inline unsigned int zswap_max_pool_pages(void)
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{
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return zswap_max_pool_percent * totalram_pages / 100;
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}
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static inline int zswap_page_pool_create(void)
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{
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/* TODO: dynamically size mempool */
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zswap_page_pool = mempool_create_page_pool(256, 0);
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if (!zswap_page_pool)
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return -ENOMEM;
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return 0;
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}
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static inline void zswap_page_pool_destroy(void)
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{
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mempool_destroy(zswap_page_pool);
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}
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static struct page *zswap_alloc_page(gfp_t flags)
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{
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struct page *page;
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if (atomic_read(&zswap_pool_pages) >= zswap_max_pool_pages()) {
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zswap_pool_limit_hit++;
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return NULL;
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}
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page = mempool_alloc(zswap_page_pool, flags);
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if (page)
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atomic_inc(&zswap_pool_pages);
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return page;
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}
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static void zswap_free_page(struct page *page)
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{
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if (!page)
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return;
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mempool_free(page, zswap_page_pool);
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atomic_dec(&zswap_pool_pages);
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}
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static struct zs_ops zswap_zs_ops = {
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.alloc = zswap_alloc_page,
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.free = zswap_free_page
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};
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|
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/*********************************
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* helpers
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**********************************/
|
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/*
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* Carries out the common pattern of freeing and entry's zsmalloc allocation,
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* freeing the entry itself, and decrementing the number of stored pages.
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*/
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static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry)
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{
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zs_free(tree->pool, entry->handle);
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zswap_entry_cache_free(entry);
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atomic_dec(&zswap_stored_pages);
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}
|
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|
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#ifdef CONFIG_ZSWAP_ENABLE_WRITEBACK
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/*********************************
|
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* writeback code
|
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**********************************/
|
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static void zswap_end_swap_write(struct bio *bio, int err)
|
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{
|
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end_swap_bio_write(bio, err);
|
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atomic_dec(&zswap_outstanding_writebacks);
|
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zswap_written_back_pages++;
|
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}
|
|
|
|
/* return enum for zswap_get_swap_cache_page */
|
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enum zswap_get_swap_ret {
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ZSWAP_SWAPCACHE_NEW,
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ZSWAP_SWAPCACHE_EXIST,
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ZSWAP_SWAPCACHE_NOMEM
|
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};
|
|
|
|
/*
|
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* zswap_get_swap_cache_page
|
|
*
|
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* This is an adaption of read_swap_cache_async()
|
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*
|
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* This function tries to find a page with the given swap entry
|
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* in the swapper_space address space (the swap cache). If the page
|
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* is found, it is returned in retpage. Otherwise, a page is allocated,
|
|
* added to the swap cache, and returned in retpage.
|
|
*
|
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* If success, the swap cache page is returned in retpage
|
|
* Returns 0 if page was already in the swap cache, page is not locked
|
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* Returns 1 if the new page needs to be populated, page is locked
|
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* Returns <0 on error
|
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*/
|
|
static int zswap_get_swap_cache_page(swp_entry_t entry,
|
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struct page **retpage)
|
|
{
|
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struct page *found_page, *new_page = NULL;
|
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struct address_space *swapper_space = &swapper_spaces[swp_type(entry)];
|
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int err;
|
|
|
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*retpage = NULL;
|
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do {
|
|
/*
|
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* First check the swap cache. Since this is normally
|
|
* called after lookup_swap_cache() failed, re-calling
|
|
* that would confuse statistics.
|
|
*/
|
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found_page = find_get_page(swapper_space, entry.val);
|
|
if (found_page)
|
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break;
|
|
|
|
/*
|
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* 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_tree *tree,
|
|
struct zswap_entry *entry)
|
|
{
|
|
unsigned long type = tree->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);
|
|
if (!__swap_writepage(page, &wbc, zswap_end_swap_write))
|
|
atomic_inc(&zswap_outstanding_writebacks);
|
|
page_cache_release(page);
|
|
|
|
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(struct zswap_tree *tree, int nr)
|
|
{
|
|
struct zswap_entry *entry;
|
|
int i, ret, refcount, freed_nr = 0;
|
|
|
|
for (i = 0; i < nr; i++) {
|
|
/*
|
|
* 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)
|
|
break;
|
|
|
|
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(tree, 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 four possible values for refcount here:
|
|
* (1) refcount is 2, writeback failed and load is in progress;
|
|
* do nothing, load will add us back to the LRU
|
|
* (2) refcount is 1, writeback failed; do not free entry,
|
|
* add back to LRU
|
|
* (3) refcount is 0, (normal case) not invalidate yet;
|
|
* remove from rbtree and free entry
|
|
* (4) refcount is -1, invalidate happened during writeback;
|
|
* free entry
|
|
*/
|
|
if (refcount == 1)
|
|
list_add(&entry->lru, &tree->lru);
|
|
|
|
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);
|
|
freed_nr++;
|
|
}
|
|
}
|
|
return freed_nr;
|
|
}
|
|
#endif /* CONFIG_ZSWAP_ENABLE_WRITEBACK */
|
|
|
|
/*******************************************
|
|
* page pool for temporary compression result
|
|
********************************************/
|
|
#define ZSWAP_TMPPAGE_POOL_PAGES 16
|
|
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
|
|
**********************************/
|
|
/* 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;
|
|
unsigned long handle;
|
|
char *buf;
|
|
u8 *src, *dst;
|
|
struct page *tmppage;
|
|
bool writeback_attempted = 0;
|
|
#ifdef CONFIG_ZSWAP_ENABLE_WRITEBACK
|
|
u8 *tmpdst;
|
|
#endif
|
|
|
|
if (!tree) {
|
|
ret = -ENODEV;
|
|
goto reject;
|
|
}
|
|
|
|
/* if this page got EIO on pageout before, give up immediately */
|
|
if (PageError(page)) {
|
|
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;
|
|
}
|
|
if ((dlen * 100 / PAGE_SIZE) > zswap_max_compression_ratio) {
|
|
zswap_reject_compress_poor++;
|
|
ret = -E2BIG;
|
|
goto freepage;
|
|
}
|
|
|
|
/* store */
|
|
handle = zs_malloc(tree->pool, dlen,
|
|
__GFP_NORETRY | __GFP_HIGHMEM | __GFP_NOMEMALLOC |
|
|
__GFP_NOWARN);
|
|
if (!handle) {
|
|
#ifdef CONFIG_ZSWAP_ENABLE_WRITEBACK
|
|
zswap_writeback_attempted++;
|
|
/*
|
|
* Copy compressed buffer out of per-cpu storage so
|
|
* we can re-enable preemption.
|
|
*/
|
|
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(tree, 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++;
|
|
#else
|
|
ret = -ENOMEM;
|
|
goto freepage;
|
|
#endif
|
|
}
|
|
|
|
buf = zs_map_object(tree->pool, handle, ZS_MM_WO);
|
|
memcpy(buf, dst, dlen);
|
|
zs_unmap_object(tree->pool, handle);
|
|
if (writeback_attempted)
|
|
zswap_tmppage_free(tmppage);
|
|
else
|
|
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 and lru */
|
|
rb_erase(&dupentry->rbnode, &tree->rbroot);
|
|
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 */
|
|
atomic_inc(&zswap_stored_pages);
|
|
|
|
return 0;
|
|
|
|
freepage:
|
|
if (writeback_attempted)
|
|
zswap_tmppage_free(tmppage);
|
|
else
|
|
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;
|
|
|
|
/* 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 */
|
|
dlen = PAGE_SIZE;
|
|
src = zs_map_object(tree->pool, entry->handle, ZS_MM_RO);
|
|
dst = kmap_atomic(page);
|
|
zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
|
|
dst, &dlen);
|
|
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;
|
|
}
|
|
|
|
/* invalidates a single page */
|
|
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 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 */
|
|
zswap_free_entry(tree, entry);
|
|
}
|
|
|
|
/* invalidates all pages 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);
|
|
zs_free(tree->pool, entry->handle);
|
|
zswap_entry_cache_free(entry);
|
|
atomic_dec(&zswap_stored_pages);
|
|
}
|
|
tree->rbroot = RB_ROOT;
|
|
INIT_LIST_HEAD(&tree->lru);
|
|
spin_unlock(&tree->lock);
|
|
}
|
|
|
|
/* NOTE: this is called in atomic context from swapon and must not sleep */
|
|
static void zswap_frontswap_init(unsigned type)
|
|
{
|
|
struct zswap_tree *tree;
|
|
|
|
tree = kzalloc(sizeof(struct zswap_tree), GFP_ATOMIC);
|
|
if (!tree)
|
|
goto err;
|
|
tree->pool = zs_create_pool(GFP_NOWAIT, &zswap_zs_ops);
|
|
if (!tree->pool)
|
|
goto freetree;
|
|
tree->rbroot = RB_ROOT;
|
|
INIT_LIST_HEAD(&tree->lru);
|
|
spin_lock_init(&tree->lock);
|
|
tree->type = type;
|
|
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
|
|
};
|
|
|
|
/*********************************
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* debugfs functions
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|
**********************************/
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#ifdef CONFIG_DEBUG_FS
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#include <linux/debugfs.h>
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static struct dentry *zswap_debugfs_root;
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static int __init zswap_debugfs_init(void)
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{
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if (!debugfs_initialized())
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return -ENODEV;
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zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
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if (!zswap_debugfs_root)
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return -ENOMEM;
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debugfs_create_u64("saved_by_writeback", S_IRUGO,
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zswap_debugfs_root, &zswap_saved_by_writeback);
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debugfs_create_u64("pool_limit_hit", S_IRUGO,
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zswap_debugfs_root, &zswap_pool_limit_hit);
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debugfs_create_u64("reject_writeback_attempted", S_IRUGO,
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zswap_debugfs_root, &zswap_writeback_attempted);
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debugfs_create_u64("reject_tmppage_fail", S_IRUGO,
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zswap_debugfs_root, &zswap_reject_tmppage_fail);
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debugfs_create_u64("reject_zsmalloc_fail", S_IRUGO,
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zswap_debugfs_root, &zswap_reject_zsmalloc_fail);
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debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
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zswap_debugfs_root, &zswap_reject_kmemcache_fail);
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debugfs_create_u64("reject_compress_poor", S_IRUGO,
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zswap_debugfs_root, &zswap_reject_compress_poor);
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debugfs_create_u64("written_back_pages", S_IRUGO,
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zswap_debugfs_root, &zswap_written_back_pages);
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debugfs_create_u64("duplicate_entry", S_IRUGO,
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zswap_debugfs_root, &zswap_duplicate_entry);
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debugfs_create_atomic_t("pool_pages", S_IRUGO,
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zswap_debugfs_root, &zswap_pool_pages);
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|
debugfs_create_atomic_t("stored_pages", S_IRUGO,
|
|
zswap_debugfs_root, &zswap_stored_pages);
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#ifdef CONFIG_ZSWAP_ENABLE_WRITEBACK
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debugfs_create_atomic_t("outstanding_writebacks", S_IRUGO,
|
|
zswap_debugfs_root, &zswap_outstanding_writebacks);
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#endif
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|
return 0;
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|
}
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|
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static void __exit zswap_debugfs_exit(void)
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|
{
|
|
debugfs_remove_recursive(zswap_debugfs_root);
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}
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#else
|
|
static inline int __init zswap_debugfs_init(void)
|
|
{
|
|
return 0;
|
|
}
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|
|
|
static inline void __exit zswap_debugfs_exit(void) { }
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#endif
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|
|
/*********************************
|
|
* module init and exit
|
|
**********************************/
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static int __init init_zswap(void)
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|
{
|
|
if (!zswap_enabled)
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return 0;
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|
|
|
pr_info("loading zswap\n");
|
|
if (zswap_entry_cache_create()) {
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|
pr_err("entry cache creation failed\n");
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|
goto error;
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|
}
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|
if (zswap_page_pool_create()) {
|
|
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;
|
|
}
|
|
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_tmppage_pool_destroy();
|
|
tmppoolfail:
|
|
zswap_page_pool_destroy();
|
|
pagepoolfail:
|
|
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");
|