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mm/zswap.c 24.1 KB
2b2811178   Seth Jennings   zswap: add to mm/
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  /*
   * zswap.c - zswap driver file
   *
   * zswap is a backend for frontswap that takes pages that are in the process
   * of being swapped out and attempts to compress and store them in a
   * RAM-based memory pool.  This can result in a significant I/O reduction on
   * the swap device and, in the case where decompressing from RAM is faster
   * than reading from the swap device, can also improve workload performance.
   *
   * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version 2
   * of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
  */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/module.h>
  #include <linux/cpu.h>
  #include <linux/highmem.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>
  #include <linux/atomic.h>
  #include <linux/frontswap.h>
  #include <linux/rbtree.h>
  #include <linux/swap.h>
  #include <linux/crypto.h>
  #include <linux/mempool.h>
  #include <linux/zbud.h>
  
  #include <linux/mm_types.h>
  #include <linux/page-flags.h>
  #include <linux/swapops.h>
  #include <linux/writeback.h>
  #include <linux/pagemap.h>
  
  /*********************************
  * statistics
  **********************************/
  /* Number of memory pages used by the compressed pool */
  static u64 zswap_pool_pages;
  /* The number of compressed pages currently stored in zswap */
  static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  
  /*
   * The statistics below are not protected from concurrent access for
   * performance reasons so they may not be a 100% accurate.  However,
   * they do provide useful information on roughly how many times a
   * certain event is occurring.
  */
  
  /* Pool limit was hit (see zswap_max_pool_percent) */
  static u64 zswap_pool_limit_hit;
  /* Pages written back when pool limit was reached */
  static u64 zswap_written_back_pages;
  /* Store failed due to a reclaim failure after pool limit was reached */
  static u64 zswap_reject_reclaim_fail;
  /* Compressed page was too big for the allocator to (optimally) store */
  static u64 zswap_reject_compress_poor;
  /* Store failed because underlying allocator could not get memory */
  static u64 zswap_reject_alloc_fail;
  /* Store failed because the entry metadata could not be allocated (rare) */
  static u64 zswap_reject_kmemcache_fail;
  /* Duplicate store was encountered (rare) */
  static u64 zswap_duplicate_entry;
  
  /*********************************
  * tunables
  **********************************/
  /* Enable/disable zswap (disabled by default, fixed at boot for now) */
  static bool zswap_enabled __read_mostly;
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  module_param_named(enabled, zswap_enabled, bool, 0444);
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  /* Compressor to be used by zswap (fixed at boot for now) */
  #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
  static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
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  module_param_named(compressor, zswap_compressor, charp, 0444);
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  /* 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);
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  /* zbud_pool is shared by all of zswap backend  */
  static struct zbud_pool *zswap_pool;
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  /*********************************
  * compression functions
  **********************************/
  /* per-cpu compression transforms */
  static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
  
  enum comp_op {
  	ZSWAP_COMPOP_COMPRESS,
  	ZSWAP_COMPOP_DECOMPRESS
  };
  
  static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
  				u8 *dst, unsigned int *dlen)
  {
  	struct crypto_comp *tfm;
  	int ret;
  
  	tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
  	switch (op) {
  	case ZSWAP_COMPOP_COMPRESS:
  		ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
  		break;
  	case ZSWAP_COMPOP_DECOMPRESS:
  		ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
  		break;
  	default:
  		ret = -EINVAL;
  	}
  
  	put_cpu();
  	return ret;
  }
  
  static int __init zswap_comp_init(void)
  {
  	if (!crypto_has_comp(zswap_compressor, 0, 0)) {
  		pr_info("%s compressor not available
  ", zswap_compressor);
  		/* fall back to default compressor */
  		zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
  		if (!crypto_has_comp(zswap_compressor, 0, 0))
  			/* can't even load the default compressor */
  			return -ENODEV;
  	}
  	pr_info("using %s compressor
  ", zswap_compressor);
  
  	/* alloc percpu transforms */
  	zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
  	if (!zswap_comp_pcpu_tfms)
  		return -ENOMEM;
  	return 0;
  }
  
  static void zswap_comp_exit(void)
  {
  	/* free percpu transforms */
  	if (zswap_comp_pcpu_tfms)
  		free_percpu(zswap_comp_pcpu_tfms);
  }
  
  /*********************************
  * data structures
  **********************************/
  /*
   * struct zswap_entry
   *
   * This structure contains the metadata for tracking a single compressed
   * page within zswap.
   *
   * rbnode - links the entry into red-black tree for the appropriate swap type
   * refcount - the number of outstanding reference to the entry. This is needed
   *            to protect against premature freeing of the entry by code
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   *            concurrent calls to load, invalidate, and writeback.  The lock
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   *            for the zswap_tree structure that contains the entry must
   *            be held while changing the refcount.  Since the lock must
   *            be held, there is no reason to also make refcount atomic.
   * offset - the swap offset for the entry.  Index into the red-black tree.
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   * handle - zbud 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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   */
  struct zswap_entry {
  	struct rb_node rbnode;
  	pgoff_t offset;
  	int refcount;
  	unsigned int length;
  	unsigned long handle;
  };
  
  struct zswap_header {
  	swp_entry_t swpentry;
  };
  
  /*
   * The tree lock in the zswap_tree struct protects a few things:
   * - the rbtree
   * - the refcount field of each entry in the tree
   */
  struct zswap_tree {
  	struct rb_root rbroot;
  	spinlock_t lock;
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  };
  
  static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
  
  /*********************************
  * zswap entry functions
  **********************************/
  static struct kmem_cache *zswap_entry_cache;
  
  static int zswap_entry_cache_create(void)
  {
  	zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
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  	return zswap_entry_cache == NULL;
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  }
  
  static void zswap_entry_cache_destory(void)
  {
  	kmem_cache_destroy(zswap_entry_cache);
  }
  
  static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
  {
  	struct zswap_entry *entry;
  	entry = kmem_cache_alloc(zswap_entry_cache, gfp);
  	if (!entry)
  		return NULL;
  	entry->refcount = 1;
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  	RB_CLEAR_NODE(&entry->rbnode);
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  	return entry;
  }
  
  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;
  }
  
  /*
   * 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 zbud allocation,
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   * freeing the entry itself, and decrementing the number of stored pages.
   */
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  static void zswap_free_entry(struct zswap_entry *entry)
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  {
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  	zbud_free(zswap_pool, entry->handle);
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  	zswap_entry_cache_free(entry);
  	atomic_dec(&zswap_stored_pages);
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  	zswap_pool_pages = zbud_get_pool_size(zswap_pool);
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  }
  
  /* caller must hold the tree lock */
  static void zswap_entry_get(struct zswap_entry *entry)
  {
  	entry->refcount++;
  }
  
  /* 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);
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  		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 = NULL;
  
  	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_cpu_notifier(unsigned long action, unsigned long cpu)
  {
  	struct crypto_comp *tfm;
  	u8 *dst;
  
  	switch (action) {
  	case CPU_UP_PREPARE:
  		tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
  		if (IS_ERR(tfm)) {
  			pr_err("can't allocate compressor transform
  ");
  			return NOTIFY_BAD;
  		}
  		*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
  		dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
  		if (!dst) {
  			pr_err("can't allocate compressor buffer
  ");
  			crypto_free_comp(tfm);
  			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
  			return NOTIFY_BAD;
  		}
  		per_cpu(zswap_dstmem, cpu) = dst;
  		break;
  	case CPU_DEAD:
  	case CPU_UP_CANCELED:
  		tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
  		if (tfm) {
  			crypto_free_comp(tfm);
  			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
  		}
  		dst = per_cpu(zswap_dstmem, cpu);
  		kfree(dst);
  		per_cpu(zswap_dstmem, cpu) = NULL;
  		break;
  	default:
  		break;
  	}
  	return NOTIFY_OK;
  }
  
  static int zswap_cpu_notifier(struct notifier_block *nb,
  				unsigned long action, void *pcpu)
  {
  	unsigned long cpu = (unsigned long)pcpu;
  	return __zswap_cpu_notifier(action, cpu);
  }
  
  static struct notifier_block zswap_cpu_notifier_block = {
  	.notifier_call = zswap_cpu_notifier
  };
  
  static int zswap_cpu_init(void)
  {
  	unsigned long cpu;
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  	cpu_notifier_register_begin();
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  	for_each_online_cpu(cpu)
  		if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
  			goto cleanup;
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  	__register_cpu_notifier(&zswap_cpu_notifier_block);
  	cpu_notifier_register_done();
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  	return 0;
  
  cleanup:
  	for_each_online_cpu(cpu)
  		__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
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  	cpu_notifier_register_done();
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  	return -ENOMEM;
  }
  
  /*********************************
  * helpers
  **********************************/
  static bool zswap_is_full(void)
  {
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  	return totalram_pages * zswap_max_pool_percent / 100 <
  		zswap_pool_pages;
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  }
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  /*********************************
  * writeback code
  **********************************/
  /* return enum for zswap_get_swap_cache_page */
  enum zswap_get_swap_ret {
  	ZSWAP_SWAPCACHE_NEW,
  	ZSWAP_SWAPCACHE_EXIST,
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  	ZSWAP_SWAPCACHE_FAIL,
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  };
  
  /*
   * 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
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   * 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
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   */
  static int zswap_get_swap_cache_page(swp_entry_t entry,
  				struct page **retpage)
  {
  	struct page *found_page, *new_page = NULL;
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  	struct address_space *swapper_space = swap_address_space(entry);
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  	int err;
  
  	*retpage = NULL;
  	do {
  		/*
  		 * First check the swap cache.  Since this is normally
  		 * called after lookup_swap_cache() failed, re-calling
  		 * that would confuse statistics.
  		 */
  		found_page = find_get_page(swapper_space, entry.val);
  		if (found_page)
  			break;
  
  		/*
  		 * Get a new page to read into from swap.
  		 */
  		if (!new_page) {
  			new_page = alloc_page(GFP_KERNEL);
  			if (!new_page)
  				break; /* Out of memory */
  		}
  
  		/*
  		 * call radix_tree_preload() while we can wait.
  		 */
  		err = radix_tree_preload(GFP_KERNEL);
  		if (err)
  			break;
  
  		/*
  		 * Swap entry may have been freed since our caller observed it.
  		 */
  		err = swapcache_prepare(entry);
  		if (err == -EEXIST) { /* seems racy */
  			radix_tree_preload_end();
  			continue;
  		}
  		if (err) { /* swp entry is obsolete ? */
  			radix_tree_preload_end();
  			break;
  		}
  
  		/* May fail (-ENOMEM) if radix-tree node allocation failed. */
  		__set_page_locked(new_page);
  		SetPageSwapBacked(new_page);
  		err = __add_to_swap_cache(new_page, entry);
  		if (likely(!err)) {
  			radix_tree_preload_end();
  			lru_cache_add_anon(new_page);
  			*retpage = new_page;
  			return ZSWAP_SWAPCACHE_NEW;
  		}
  		radix_tree_preload_end();
  		ClearPageSwapBacked(new_page);
  		__clear_page_locked(new_page);
  		/*
  		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
  		 * clear SWAP_HAS_CACHE flag.
  		 */
  		swapcache_free(entry, NULL);
  	} while (err != -ENOMEM);
  
  	if (new_page)
  		page_cache_release(new_page);
  	if (!found_page)
67d13fe84   Weijie Yang   mm/zswap: bugfix:...
508
  		return ZSWAP_SWAPCACHE_FAIL;
2b2811178   Seth Jennings   zswap: add to mm/
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
  	*retpage = found_page;
  	return ZSWAP_SWAPCACHE_EXIST;
  }
  
  /*
   * Attempts to free an entry by adding a page to the swap cache,
   * decompressing the entry data into the page, and issuing a
   * bio write to write the page back to the swap device.
   *
   * This can be thought of as a "resumed writeback" of the page
   * to the swap device.  We are basically resuming the same swap
   * writeback path that was intercepted with the frontswap_store()
   * in the first place.  After the page has been decompressed into
   * the swap cache, the compressed version stored by zswap can be
   * freed.
   */
  static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
  {
  	struct zswap_header *zhdr;
  	swp_entry_t swpentry;
  	struct zswap_tree *tree;
  	pgoff_t offset;
  	struct zswap_entry *entry;
  	struct page *page;
  	u8 *src, *dst;
  	unsigned int dlen;
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
535
  	int ret;
2b2811178   Seth Jennings   zswap: add to mm/
536
537
538
539
540
541
542
543
544
545
  	struct writeback_control wbc = {
  		.sync_mode = WB_SYNC_NONE,
  	};
  
  	/* extract swpentry from data */
  	zhdr = zbud_map(pool, handle);
  	swpentry = zhdr->swpentry; /* here */
  	zbud_unmap(pool, handle);
  	tree = zswap_trees[swp_type(swpentry)];
  	offset = swp_offset(swpentry);
2b2811178   Seth Jennings   zswap: add to mm/
546
547
548
  
  	/* find and ref zswap entry */
  	spin_lock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
549
  	entry = zswap_entry_find_get(&tree->rbroot, offset);
2b2811178   Seth Jennings   zswap: add to mm/
550
551
552
553
554
  	if (!entry) {
  		/* entry was invalidated */
  		spin_unlock(&tree->lock);
  		return 0;
  	}
2b2811178   Seth Jennings   zswap: add to mm/
555
556
557
558
559
  	spin_unlock(&tree->lock);
  	BUG_ON(offset != entry->offset);
  
  	/* try to allocate swap cache page */
  	switch (zswap_get_swap_cache_page(swpentry, &page)) {
67d13fe84   Weijie Yang   mm/zswap: bugfix:...
560
  	case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
2b2811178   Seth Jennings   zswap: add to mm/
561
562
  		ret = -ENOMEM;
  		goto fail;
67d13fe84   Weijie Yang   mm/zswap: bugfix:...
563
  	case ZSWAP_SWAPCACHE_EXIST:
2b2811178   Seth Jennings   zswap: add to mm/
564
565
566
567
568
569
570
571
  		/* page is already in the swap cache, ignore for now */
  		page_cache_release(page);
  		ret = -EEXIST;
  		goto fail;
  
  	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
  		/* decompress */
  		dlen = PAGE_SIZE;
60105e124   Minchan Kim   mm/zswap: support...
572
  		src = (u8 *)zbud_map(zswap_pool, entry->handle) +
2b2811178   Seth Jennings   zswap: add to mm/
573
574
575
576
577
  			sizeof(struct zswap_header);
  		dst = kmap_atomic(page);
  		ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
  				entry->length, dst, &dlen);
  		kunmap_atomic(dst);
60105e124   Minchan Kim   mm/zswap: support...
578
  		zbud_unmap(zswap_pool, entry->handle);
2b2811178   Seth Jennings   zswap: add to mm/
579
580
581
582
583
584
  		BUG_ON(ret);
  		BUG_ON(dlen != PAGE_SIZE);
  
  		/* page is up to date */
  		SetPageUptodate(page);
  	}
b349acc76   Weijie Yang   mm/zswap: avoid u...
585
586
  	/* move it to the tail of the inactive list after end_writeback */
  	SetPageReclaim(page);
2b2811178   Seth Jennings   zswap: add to mm/
587
588
589
590
591
592
  	/* start writeback */
  	__swap_writepage(page, &wbc, end_swap_bio_write);
  	page_cache_release(page);
  	zswap_written_back_pages++;
  
  	spin_lock(&tree->lock);
2b2811178   Seth Jennings   zswap: add to mm/
593
  	/* drop local reference */
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
594
  	zswap_entry_put(tree, entry);
2b2811178   Seth Jennings   zswap: add to mm/
595
596
  
  	/*
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
597
598
599
600
601
602
603
604
  	* 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);
2b2811178   Seth Jennings   zswap: add to mm/
605
  	spin_unlock(&tree->lock);
2b2811178   Seth Jennings   zswap: add to mm/
606

0ab0abcf5   Weijie Yang   mm/zswap: refacto...
607
608
609
610
611
612
613
614
615
  	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
  	*/
2b2811178   Seth Jennings   zswap: add to mm/
616
617
  fail:
  	spin_lock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
618
  	zswap_entry_put(tree, entry);
2b2811178   Seth Jennings   zswap: add to mm/
619
  	spin_unlock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
620
621
  
  end:
2b2811178   Seth Jennings   zswap: add to mm/
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
  	return ret;
  }
  
  /*********************************
  * frontswap hooks
  **********************************/
  /* attempts to compress and store an single page */
  static int zswap_frontswap_store(unsigned type, pgoff_t offset,
  				struct page *page)
  {
  	struct zswap_tree *tree = zswap_trees[type];
  	struct zswap_entry *entry, *dupentry;
  	int ret;
  	unsigned int dlen = PAGE_SIZE, len;
  	unsigned long handle;
  	char *buf;
  	u8 *src, *dst;
  	struct zswap_header *zhdr;
  
  	if (!tree) {
  		ret = -ENODEV;
  		goto reject;
  	}
  
  	/* reclaim space if needed */
  	if (zswap_is_full()) {
  		zswap_pool_limit_hit++;
60105e124   Minchan Kim   mm/zswap: support...
649
  		if (zbud_reclaim_page(zswap_pool, 8)) {
2b2811178   Seth Jennings   zswap: add to mm/
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
  			zswap_reject_reclaim_fail++;
  			ret = -ENOMEM;
  			goto reject;
  		}
  	}
  
  	/* allocate entry */
  	entry = zswap_entry_cache_alloc(GFP_KERNEL);
  	if (!entry) {
  		zswap_reject_kmemcache_fail++;
  		ret = -ENOMEM;
  		goto reject;
  	}
  
  	/* compress */
  	dst = get_cpu_var(zswap_dstmem);
  	src = kmap_atomic(page);
  	ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
  	kunmap_atomic(src);
  	if (ret) {
  		ret = -EINVAL;
  		goto freepage;
  	}
  
  	/* store */
  	len = dlen + sizeof(struct zswap_header);
60105e124   Minchan Kim   mm/zswap: support...
676
  	ret = zbud_alloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
2b2811178   Seth Jennings   zswap: add to mm/
677
678
679
680
681
682
683
684
685
  		&handle);
  	if (ret == -ENOSPC) {
  		zswap_reject_compress_poor++;
  		goto freepage;
  	}
  	if (ret) {
  		zswap_reject_alloc_fail++;
  		goto freepage;
  	}
60105e124   Minchan Kim   mm/zswap: support...
686
  	zhdr = zbud_map(zswap_pool, handle);
2b2811178   Seth Jennings   zswap: add to mm/
687
688
689
  	zhdr->swpentry = swp_entry(type, offset);
  	buf = (u8 *)(zhdr + 1);
  	memcpy(buf, dst, dlen);
60105e124   Minchan Kim   mm/zswap: support...
690
  	zbud_unmap(zswap_pool, handle);
2b2811178   Seth Jennings   zswap: add to mm/
691
692
693
694
695
696
697
698
699
700
701
702
703
704
  	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 */
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
705
706
  			zswap_rb_erase(&tree->rbroot, dupentry);
  			zswap_entry_put(tree, dupentry);
2b2811178   Seth Jennings   zswap: add to mm/
707
708
709
710
711
712
  		}
  	} while (ret == -EEXIST);
  	spin_unlock(&tree->lock);
  
  	/* update stats */
  	atomic_inc(&zswap_stored_pages);
60105e124   Minchan Kim   mm/zswap: support...
713
  	zswap_pool_pages = zbud_get_pool_size(zswap_pool);
2b2811178   Seth Jennings   zswap: add to mm/
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
  
  	return 0;
  
  freepage:
  	put_cpu_var(zswap_dstmem);
  	zswap_entry_cache_free(entry);
  reject:
  	return ret;
  }
  
  /*
   * returns 0 if the page was successfully decompressed
   * return -1 on entry not found or error
  */
  static int zswap_frontswap_load(unsigned type, pgoff_t offset,
  				struct page *page)
  {
  	struct zswap_tree *tree = zswap_trees[type];
  	struct zswap_entry *entry;
  	u8 *src, *dst;
  	unsigned int dlen;
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
735
  	int ret;
2b2811178   Seth Jennings   zswap: add to mm/
736
737
738
  
  	/* find */
  	spin_lock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
739
  	entry = zswap_entry_find_get(&tree->rbroot, offset);
2b2811178   Seth Jennings   zswap: add to mm/
740
741
742
743
744
  	if (!entry) {
  		/* entry was written back */
  		spin_unlock(&tree->lock);
  		return -1;
  	}
2b2811178   Seth Jennings   zswap: add to mm/
745
746
747
748
  	spin_unlock(&tree->lock);
  
  	/* decompress */
  	dlen = PAGE_SIZE;
60105e124   Minchan Kim   mm/zswap: support...
749
  	src = (u8 *)zbud_map(zswap_pool, entry->handle) +
2b2811178   Seth Jennings   zswap: add to mm/
750
751
752
753
754
  			sizeof(struct zswap_header);
  	dst = kmap_atomic(page);
  	ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
  		dst, &dlen);
  	kunmap_atomic(dst);
60105e124   Minchan Kim   mm/zswap: support...
755
  	zbud_unmap(zswap_pool, entry->handle);
2b2811178   Seth Jennings   zswap: add to mm/
756
757
758
  	BUG_ON(ret);
  
  	spin_lock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
759
  	zswap_entry_put(tree, entry);
2b2811178   Seth Jennings   zswap: add to mm/
760
  	spin_unlock(&tree->lock);
2b2811178   Seth Jennings   zswap: add to mm/
761
762
763
764
765
766
767
768
  	return 0;
  }
  
  /* frees an entry in zswap */
  static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
  {
  	struct zswap_tree *tree = zswap_trees[type];
  	struct zswap_entry *entry;
2b2811178   Seth Jennings   zswap: add to mm/
769
770
771
772
773
774
775
776
777
778
779
  
  	/* 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 */
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
780
  	zswap_rb_erase(&tree->rbroot, entry);
2b2811178   Seth Jennings   zswap: add to mm/
781
782
  
  	/* drop the initial reference from entry creation */
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
783
  	zswap_entry_put(tree, entry);
2b2811178   Seth Jennings   zswap: add to mm/
784
785
  
  	spin_unlock(&tree->lock);
2b2811178   Seth Jennings   zswap: add to mm/
786
787
788
789
790
791
  }
  
  /* frees all zswap entries for the given swap type */
  static void zswap_frontswap_invalidate_area(unsigned type)
  {
  	struct zswap_tree *tree = zswap_trees[type];
0bd42136f   Cody P Schafer   mm/zswap: use pos...
792
  	struct zswap_entry *entry, *n;
2b2811178   Seth Jennings   zswap: add to mm/
793
794
795
796
797
798
  
  	if (!tree)
  		return;
  
  	/* walk the tree and free everything */
  	spin_lock(&tree->lock);
0ab0abcf5   Weijie Yang   mm/zswap: refacto...
799
  	rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
60105e124   Minchan Kim   mm/zswap: support...
800
  		zswap_free_entry(entry);
2b2811178   Seth Jennings   zswap: add to mm/
801
802
  	tree->rbroot = RB_ROOT;
  	spin_unlock(&tree->lock);
aa9bca05a   Weijie Yang   mm/zswap: bugfix:...
803
804
  	kfree(tree);
  	zswap_trees[type] = NULL;
2b2811178   Seth Jennings   zswap: add to mm/
805
806
807
808
809
810
811
812
813
814
815
  }
  
  static struct zbud_ops zswap_zbud_ops = {
  	.evict = zswap_writeback_entry
  };
  
  static void zswap_frontswap_init(unsigned type)
  {
  	struct zswap_tree *tree;
  
  	tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
60105e124   Minchan Kim   mm/zswap: support...
816
817
818
819
820
  	if (!tree) {
  		pr_err("alloc failed, zswap disabled for swap type %d
  ", type);
  		return;
  	}
2b2811178   Seth Jennings   zswap: add to mm/
821
822
823
  	tree->rbroot = RB_ROOT;
  	spin_lock_init(&tree->lock);
  	zswap_trees[type] = tree;
2b2811178   Seth Jennings   zswap: add to mm/
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
  }
  
  static struct frontswap_ops zswap_frontswap_ops = {
  	.store = zswap_frontswap_store,
  	.load = zswap_frontswap_load,
  	.invalidate_page = zswap_frontswap_invalidate_page,
  	.invalidate_area = zswap_frontswap_invalidate_area,
  	.init = zswap_frontswap_init
  };
  
  /*********************************
  * debugfs functions
  **********************************/
  #ifdef CONFIG_DEBUG_FS
  #include <linux/debugfs.h>
  
  static struct dentry *zswap_debugfs_root;
  
  static int __init zswap_debugfs_init(void)
  {
  	if (!debugfs_initialized())
  		return -ENODEV;
  
  	zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
  	if (!zswap_debugfs_root)
  		return -ENOMEM;
  
  	debugfs_create_u64("pool_limit_hit", S_IRUGO,
  			zswap_debugfs_root, &zswap_pool_limit_hit);
  	debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
  			zswap_debugfs_root, &zswap_reject_reclaim_fail);
  	debugfs_create_u64("reject_alloc_fail", S_IRUGO,
  			zswap_debugfs_root, &zswap_reject_alloc_fail);
  	debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
  			zswap_debugfs_root, &zswap_reject_kmemcache_fail);
  	debugfs_create_u64("reject_compress_poor", S_IRUGO,
  			zswap_debugfs_root, &zswap_reject_compress_poor);
  	debugfs_create_u64("written_back_pages", S_IRUGO,
  			zswap_debugfs_root, &zswap_written_back_pages);
  	debugfs_create_u64("duplicate_entry", S_IRUGO,
  			zswap_debugfs_root, &zswap_duplicate_entry);
  	debugfs_create_u64("pool_pages", S_IRUGO,
  			zswap_debugfs_root, &zswap_pool_pages);
  	debugfs_create_atomic_t("stored_pages", S_IRUGO,
  			zswap_debugfs_root, &zswap_stored_pages);
  
  	return 0;
  }
  
  static void __exit zswap_debugfs_exit(void)
  {
  	debugfs_remove_recursive(zswap_debugfs_root);
  }
  #else
  static int __init zswap_debugfs_init(void)
  {
  	return 0;
  }
  
  static void __exit zswap_debugfs_exit(void) { }
  #endif
  
  /*********************************
  * module init and exit
  **********************************/
  static int __init init_zswap(void)
  {
  	if (!zswap_enabled)
  		return 0;
  
  	pr_info("loading zswap
  ");
60105e124   Minchan Kim   mm/zswap: support...
896
897
898
899
900
901
902
  
  	zswap_pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops);
  	if (!zswap_pool) {
  		pr_err("zbud pool creation failed
  ");
  		goto error;
  	}
2b2811178   Seth Jennings   zswap: add to mm/
903
904
905
  	if (zswap_entry_cache_create()) {
  		pr_err("entry cache creation failed
  ");
60105e124   Minchan Kim   mm/zswap: support...
906
  		goto cachefail;
2b2811178   Seth Jennings   zswap: add to mm/
907
908
909
910
911
912
913
914
915
916
917
  	}
  	if (zswap_comp_init()) {
  		pr_err("compressor initialization failed
  ");
  		goto compfail;
  	}
  	if (zswap_cpu_init()) {
  		pr_err("per-cpu initialization failed
  ");
  		goto pcpufail;
  	}
60105e124   Minchan Kim   mm/zswap: support...
918

2b2811178   Seth Jennings   zswap: add to mm/
919
920
921
922
923
924
925
926
927
  	frontswap_register_ops(&zswap_frontswap_ops);
  	if (zswap_debugfs_init())
  		pr_warn("debugfs initialization failed
  ");
  	return 0;
  pcpufail:
  	zswap_comp_exit();
  compfail:
  	zswap_entry_cache_destory();
60105e124   Minchan Kim   mm/zswap: support...
928
929
  cachefail:
  	zbud_destroy_pool(zswap_pool);
2b2811178   Seth Jennings   zswap: add to mm/
930
931
932
933
934
935
936
937
938
  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");