1/*
  2 * zswap.c - zswap driver file
  3 *
  4 * zswap is a backend for frontswap that takes pages that are in the process
  5 * of being swapped out and attempts to compress and store them in a
  6 * RAM-based memory pool.  This can result in a significant I/O reduction on
  7 * the swap device and, in the case where decompressing from RAM is faster
  8 * than reading from the swap device, can also improve workload performance.
  9 *
 10 * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
 11 *
 12 * This program is free software; you can redistribute it and/or
 13 * modify it under the terms of the GNU General Public License
 14 * as published by the Free Software Foundation; either version 2
 15 * of the License, or (at your option) any later version.
 16 *
 17 * This program is distributed in the hope that it will be useful,
 18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 20 * GNU General Public License for more details.
 21*/
 22
 23#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 24
 25#include <linux/module.h>
 26#include <linux/cpu.h>
 27#include <linux/highmem.h>
 28#include <linux/slab.h>
 29#include <linux/spinlock.h>
 30#include <linux/types.h>
 31#include <linux/atomic.h>
 32#include <linux/frontswap.h>
 33#include <linux/rbtree.h>
 34#include <linux/swap.h>
 35#include <linux/crypto.h>
 
 
 36#include <linux/mempool.h>
 37#include <linux/zbud.h>
 38
 
 39#include <linux/mm_types.h>
 40#include <linux/page-flags.h>
 41#include <linux/swapops.h>
 42#include <linux/writeback.h>
 43#include <linux/pagemap.h>
 
 
 
 
 
 44
 45/*********************************
 46* statistics
 47**********************************/
 48/* Number of memory pages used by the compressed pool */
 49static u64 zswap_pool_pages;
 50/* The number of compressed pages currently stored in zswap */
 51static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
 
 
 52
 53/*
 54 * The statistics below are not protected from concurrent access for
 55 * performance reasons so they may not be a 100% accurate.  However,
 56 * they do provide useful information on roughly how many times a
 57 * certain event is occurring.
 58*/
 59
 60/* Pool limit was hit (see zswap_max_pool_percent) */
 61static u64 zswap_pool_limit_hit;
 62/* Pages written back when pool limit was reached */
 63static u64 zswap_written_back_pages;
 64/* Store failed due to a reclaim failure after pool limit was reached */
 65static u64 zswap_reject_reclaim_fail;
 
 
 66/* Compressed page was too big for the allocator to (optimally) store */
 67static u64 zswap_reject_compress_poor;
 68/* Store failed because underlying allocator could not get memory */
 69static u64 zswap_reject_alloc_fail;
 70/* Store failed because the entry metadata could not be allocated (rare) */
 71static u64 zswap_reject_kmemcache_fail;
 72/* Duplicate store was encountered (rare) */
 73static u64 zswap_duplicate_entry;
 
 
 
 74
 75/*********************************
 76* tunables
 77**********************************/
 78/* Enable/disable zswap (disabled by default, fixed at boot for now) */
 79static bool zswap_enabled __read_mostly;
 80module_param_named(enabled, zswap_enabled, bool, 0444);
 81
 82/* Compressor to be used by zswap (fixed at boot for now) */
 83#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
 84static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
 85module_param_named(compressor, zswap_compressor, charp, 0444);
 86
 87/* The maximum percentage of memory that the compressed pool can occupy */
 88static unsigned int zswap_max_pool_percent = 20;
 89module_param_named(max_pool_percent,
 90			zswap_max_pool_percent, uint, 0644);
 91
 92/* zbud_pool is shared by all of zswap backend  */
 93static struct zbud_pool *zswap_pool;
 94
 95/*********************************
 96* compression functions
 97**********************************/
 98/* per-cpu compression transforms */
 99static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
 
 
 
 
100
101enum comp_op {
102	ZSWAP_COMPOP_COMPRESS,
103	ZSWAP_COMPOP_DECOMPRESS
 
 
 
 
 
104};
 
 
105
106static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
107				u8 *dst, unsigned int *dlen)
108{
109	struct crypto_comp *tfm;
110	int ret;
 
 
 
 
111
112	tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
113	switch (op) {
114	case ZSWAP_COMPOP_COMPRESS:
115		ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
116		break;
117	case ZSWAP_COMPOP_DECOMPRESS:
118		ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
119		break;
120	default:
121		ret = -EINVAL;
122	}
123
124	put_cpu();
125	return ret;
126}
 
127
128static int __init zswap_comp_init(void)
129{
130	if (!crypto_has_comp(zswap_compressor, 0, 0)) {
131		pr_info("%s compressor not available\n", zswap_compressor);
132		/* fall back to default compressor */
133		zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
134		if (!crypto_has_comp(zswap_compressor, 0, 0))
135			/* can't even load the default compressor */
136			return -ENODEV;
137	}
138	pr_info("using %s compressor\n", zswap_compressor);
139
140	/* alloc percpu transforms */
141	zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
142	if (!zswap_comp_pcpu_tfms)
143		return -ENOMEM;
144	return 0;
145}
 
 
146
147static void zswap_comp_exit(void)
148{
149	/* free percpu transforms */
150	if (zswap_comp_pcpu_tfms)
151		free_percpu(zswap_comp_pcpu_tfms);
152}
153
154/*********************************
155* data structures
156**********************************/
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
157/*
158 * struct zswap_entry
159 *
160 * This structure contains the metadata for tracking a single compressed
161 * page within zswap.
162 *
163 * rbnode - links the entry into red-black tree for the appropriate swap type
164 * refcount - the number of outstanding reference to the entry. This is needed
165 *            to protect against premature freeing of the entry by code
166 *            concurrent calls to load, invalidate, and writeback.  The lock
167 *            for the zswap_tree structure that contains the entry must
168 *            be held while changing the refcount.  Since the lock must
169 *            be held, there is no reason to also make refcount atomic.
170 * offset - the swap offset for the entry.  Index into the red-black tree.
171 * handle - zbud allocation handle that stores the compressed page data
172 * length - the length in bytes of the compressed page data.  Needed during
173 *          decompression
 
 
 
 
 
 
174 */
175struct zswap_entry {
176	struct rb_node rbnode;
177	pgoff_t offset;
178	int refcount;
179	unsigned int length;
180	unsigned long handle;
181};
182
183struct zswap_header {
184	swp_entry_t swpentry;
 
 
 
 
 
 
 
 
185};
186
187/*
188 * The tree lock in the zswap_tree struct protects a few things:
189 * - the rbtree
190 * - the refcount field of each entry in the tree
191 */
192struct zswap_tree {
193	struct rb_root rbroot;
194	spinlock_t lock;
195};
196
197static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
198
199/*********************************
200* zswap entry functions
201**********************************/
202static struct kmem_cache *zswap_entry_cache;
203
204static int zswap_entry_cache_create(void)
205{
206	zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
207	return zswap_entry_cache == NULL;
208}
209
210static void zswap_entry_cache_destory(void)
 
 
 
 
211{
212	kmem_cache_destroy(zswap_entry_cache);
 
213}
214
215static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
216{
217	struct zswap_entry *entry;
218	entry = kmem_cache_alloc(zswap_entry_cache, gfp);
219	if (!entry)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
220		return NULL;
221	entry->refcount = 1;
222	RB_CLEAR_NODE(&entry->rbnode);
223	return entry;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
224}
225
226static void zswap_entry_cache_free(struct zswap_entry *entry)
227{
228	kmem_cache_free(zswap_entry_cache, entry);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
229}
230
231/*********************************
232* rbtree functions
233**********************************/
234static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
235{
236	struct rb_node *node = root->rb_node;
237	struct zswap_entry *entry;
 
238
239	while (node) {
240		entry = rb_entry(node, struct zswap_entry, rbnode);
241		if (entry->offset > offset)
 
242			node = node->rb_left;
243		else if (entry->offset < offset)
244			node = node->rb_right;
245		else
246			return entry;
247	}
248	return NULL;
249}
250
251/*
252 * In the case that a entry with the same offset is found, a pointer to
253 * the existing entry is stored in dupentry and the function returns -EEXIST
254 */
255static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
256			struct zswap_entry **dupentry)
257{
258	struct rb_node **link = &root->rb_node, *parent = NULL;
259	struct zswap_entry *myentry;
 
260
261	while (*link) {
262		parent = *link;
263		myentry = rb_entry(parent, struct zswap_entry, rbnode);
264		if (myentry->offset > entry->offset)
 
265			link = &(*link)->rb_left;
266		else if (myentry->offset < entry->offset)
267			link = &(*link)->rb_right;
268		else {
269			*dupentry = myentry;
270			return -EEXIST;
271		}
272	}
273	rb_link_node(&entry->rbnode, parent, link);
274	rb_insert_color(&entry->rbnode, root);
275	return 0;
276}
277
278static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
279{
280	if (!RB_EMPTY_NODE(&entry->rbnode)) {
281		rb_erase(&entry->rbnode, root);
282		RB_CLEAR_NODE(&entry->rbnode);
283	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
284}
285
286/*
287 * Carries out the common pattern of freeing and entry's zbud allocation,
288 * freeing the entry itself, and decrementing the number of stored pages.
289 */
290static void zswap_free_entry(struct zswap_entry *entry)
291{
292	zbud_free(zswap_pool, entry->handle);
 
 
 
 
 
 
 
 
 
 
 
293	zswap_entry_cache_free(entry);
294	atomic_dec(&zswap_stored_pages);
295	zswap_pool_pages = zbud_get_pool_size(zswap_pool);
296}
297
298/* caller must hold the tree lock */
299static void zswap_entry_get(struct zswap_entry *entry)
 
 
 
 
300{
301	entry->refcount++;
 
302}
303
304/* caller must hold the tree lock
305* remove from the tree and free it, if nobody reference the entry
306*/
307static void zswap_entry_put(struct zswap_tree *tree,
308			struct zswap_entry *entry)
309{
310	int refcount = --entry->refcount;
 
 
 
 
311
312	BUG_ON(refcount < 0);
313	if (refcount == 0) {
314		zswap_rb_erase(&tree->rbroot, entry);
315		zswap_free_entry(entry);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
316	}
317}
318
319/* caller must hold the tree lock */
320static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
321				pgoff_t offset)
322{
323	struct zswap_entry *entry = NULL;
 
 
 
324
325	entry = zswap_rb_search(root, offset);
326	if (entry)
327		zswap_entry_get(entry);
328
329	return entry;
 
 
 
 
330}
331
332/*********************************
333* per-cpu code
334**********************************/
335static DEFINE_PER_CPU(u8 *, zswap_dstmem);
336
337static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
338{
339	struct crypto_comp *tfm;
340	u8 *dst;
341
342	switch (action) {
343	case CPU_UP_PREPARE:
344		tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
345		if (IS_ERR(tfm)) {
346			pr_err("can't allocate compressor transform\n");
347			return NOTIFY_BAD;
348		}
349		*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
350		dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
351		if (!dst) {
352			pr_err("can't allocate compressor buffer\n");
353			crypto_free_comp(tfm);
354			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
355			return NOTIFY_BAD;
356		}
357		per_cpu(zswap_dstmem, cpu) = dst;
358		break;
359	case CPU_DEAD:
360	case CPU_UP_CANCELED:
361		tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
362		if (tfm) {
363			crypto_free_comp(tfm);
364			*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
365		}
366		dst = per_cpu(zswap_dstmem, cpu);
367		kfree(dst);
368		per_cpu(zswap_dstmem, cpu) = NULL;
369		break;
370	default:
371		break;
372	}
373	return NOTIFY_OK;
 
374}
375
376static int zswap_cpu_notifier(struct notifier_block *nb,
377				unsigned long action, void *pcpu)
378{
379	unsigned long cpu = (unsigned long)pcpu;
380	return __zswap_cpu_notifier(action, cpu);
381}
 
 
 
 
 
 
382
383static struct notifier_block zswap_cpu_notifier_block = {
384	.notifier_call = zswap_cpu_notifier
385};
386
387static int zswap_cpu_init(void)
388{
389	unsigned long cpu;
390
391	cpu_notifier_register_begin();
392	for_each_online_cpu(cpu)
393		if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
394			goto cleanup;
395	__register_cpu_notifier(&zswap_cpu_notifier_block);
396	cpu_notifier_register_done();
397	return 0;
398
399cleanup:
400	for_each_online_cpu(cpu)
401		__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
402	cpu_notifier_register_done();
403	return -ENOMEM;
404}
 
405
406/*********************************
407* helpers
408**********************************/
409static bool zswap_is_full(void)
410{
411	return totalram_pages * zswap_max_pool_percent / 100 <
412		zswap_pool_pages;
413}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
414
415/*********************************
416* writeback code
417**********************************/
418/* return enum for zswap_get_swap_cache_page */
419enum zswap_get_swap_ret {
420	ZSWAP_SWAPCACHE_NEW,
421	ZSWAP_SWAPCACHE_EXIST,
422	ZSWAP_SWAPCACHE_FAIL,
423};
424
425/*
426 * zswap_get_swap_cache_page
427 *
428 * This is an adaption of read_swap_cache_async()
429 *
430 * This function tries to find a page with the given swap entry
431 * in the swapper_space address space (the swap cache).  If the page
432 * is found, it is returned in retpage.  Otherwise, a page is allocated,
433 * added to the swap cache, and returned in retpage.
434 *
435 * If success, the swap cache page is returned in retpage
436 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
437 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
438 *     the new page is added to swapcache and locked
439 * Returns ZSWAP_SWAPCACHE_FAIL on error
440 */
441static int zswap_get_swap_cache_page(swp_entry_t entry,
442				struct page **retpage)
443{
444	struct page *found_page, *new_page = NULL;
445	struct address_space *swapper_space = swap_address_space(entry);
446	int err;
447
448	*retpage = NULL;
449	do {
450		/*
451		 * First check the swap cache.  Since this is normally
452		 * called after lookup_swap_cache() failed, re-calling
453		 * that would confuse statistics.
454		 */
455		found_page = find_get_page(swapper_space, entry.val);
456		if (found_page)
457			break;
458
459		/*
460		 * Get a new page to read into from swap.
461		 */
462		if (!new_page) {
463			new_page = alloc_page(GFP_KERNEL);
464			if (!new_page)
465				break; /* Out of memory */
466		}
467
468		/*
469		 * call radix_tree_preload() while we can wait.
470		 */
471		err = radix_tree_preload(GFP_KERNEL);
472		if (err)
473			break;
474
475		/*
476		 * Swap entry may have been freed since our caller observed it.
477		 */
478		err = swapcache_prepare(entry);
479		if (err == -EEXIST) { /* seems racy */
480			radix_tree_preload_end();
481			continue;
482		}
483		if (err) { /* swp entry is obsolete ? */
484			radix_tree_preload_end();
485			break;
486		}
487
488		/* May fail (-ENOMEM) if radix-tree node allocation failed. */
489		__set_page_locked(new_page);
490		SetPageSwapBacked(new_page);
491		err = __add_to_swap_cache(new_page, entry);
492		if (likely(!err)) {
493			radix_tree_preload_end();
494			lru_cache_add_anon(new_page);
495			*retpage = new_page;
496			return ZSWAP_SWAPCACHE_NEW;
497		}
498		radix_tree_preload_end();
499		ClearPageSwapBacked(new_page);
500		__clear_page_locked(new_page);
501		/*
502		 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
503		 * clear SWAP_HAS_CACHE flag.
504		 */
505		swapcache_free(entry, NULL);
506	} while (err != -ENOMEM);
 
 
 
 
 
507
508	if (new_page)
509		page_cache_release(new_page);
510	if (!found_page)
511		return ZSWAP_SWAPCACHE_FAIL;
512	*retpage = found_page;
513	return ZSWAP_SWAPCACHE_EXIST;
514}
515
 
 
 
516/*
517 * Attempts to free an entry by adding a page to the swap cache,
518 * decompressing the entry data into the page, and issuing a
519 * bio write to write the page back to the swap device.
520 *
521 * This can be thought of as a "resumed writeback" of the page
522 * to the swap device.  We are basically resuming the same swap
523 * writeback path that was intercepted with the frontswap_store()
524 * in the first place.  After the page has been decompressed into
525 * the swap cache, the compressed version stored by zswap can be
526 * freed.
527 */
528static int zswap_writeback_entry(struct zbud_pool *pool, unsigned long handle)
 
529{
530	struct zswap_header *zhdr;
531	swp_entry_t swpentry;
532	struct zswap_tree *tree;
533	pgoff_t offset;
534	struct zswap_entry *entry;
535	struct page *page;
536	u8 *src, *dst;
537	unsigned int dlen;
538	int ret;
539	struct writeback_control wbc = {
540		.sync_mode = WB_SYNC_NONE,
541	};
542
543	/* extract swpentry from data */
544	zhdr = zbud_map(pool, handle);
545	swpentry = zhdr->swpentry; /* here */
546	zbud_unmap(pool, handle);
547	tree = zswap_trees[swp_type(swpentry)];
548	offset = swp_offset(swpentry);
549
550	/* find and ref zswap entry */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
551	spin_lock(&tree->lock);
552	entry = zswap_entry_find_get(&tree->rbroot, offset);
553	if (!entry) {
554		/* entry was invalidated */
555		spin_unlock(&tree->lock);
556		return 0;
 
 
 
557	}
 
 
 
558	spin_unlock(&tree->lock);
559	BUG_ON(offset != entry->offset);
560
561	/* try to allocate swap cache page */
562	switch (zswap_get_swap_cache_page(swpentry, &page)) {
563	case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
564		ret = -ENOMEM;
565		goto fail;
566
567	case ZSWAP_SWAPCACHE_EXIST:
568		/* page is already in the swap cache, ignore for now */
569		page_cache_release(page);
570		ret = -EEXIST;
571		goto fail;
572
573	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
574		/* decompress */
575		dlen = PAGE_SIZE;
576		src = (u8 *)zbud_map(zswap_pool, entry->handle) +
577			sizeof(struct zswap_header);
578		dst = kmap_atomic(page);
579		ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
580				entry->length, dst, &dlen);
581		kunmap_atomic(dst);
582		zbud_unmap(zswap_pool, entry->handle);
583		BUG_ON(ret);
584		BUG_ON(dlen != PAGE_SIZE);
585
586		/* page is up to date */
587		SetPageUptodate(page);
588	}
 
589
590	/* move it to the tail of the inactive list after end_writeback */
591	SetPageReclaim(page);
592
593	/* start writeback */
594	__swap_writepage(page, &wbc, end_swap_bio_write);
595	page_cache_release(page);
596	zswap_written_back_pages++;
597
598	spin_lock(&tree->lock);
599	/* drop local reference */
600	zswap_entry_put(tree, entry);
 
 
 
 
 
 
 
 
 
 
 
601
602	/*
603	* There are two possible situations for entry here:
604	* (1) refcount is 1(normal case),  entry is valid and on the tree
605	* (2) refcount is 0, entry is freed and not on the tree
606	*     because invalidate happened during writeback
607	*  search the tree and free the entry if find entry
608	*/
609	if (entry == zswap_rb_search(&tree->rbroot, offset))
610		zswap_entry_put(tree, entry);
611	spin_unlock(&tree->lock);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
612
613	goto end;
 
 
 
 
 
614
615	/*
616	* if we get here due to ZSWAP_SWAPCACHE_EXIST
617	* a load may happening concurrently
618	* it is safe and okay to not free the entry
619	* if we free the entry in the following put
620	* it it either okay to return !0
621	*/
622fail:
623	spin_lock(&tree->lock);
624	zswap_entry_put(tree, entry);
625	spin_unlock(&tree->lock);
626
627end:
 
 
 
 
 
 
 
 
 
 
 
 
 
628	return ret;
629}
630
631/*********************************
632* frontswap hooks
633**********************************/
634/* attempts to compress and store an single page */
635static int zswap_frontswap_store(unsigned type, pgoff_t offset,
636				struct page *page)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
637{
638	struct zswap_tree *tree = zswap_trees[type];
 
 
639	struct zswap_entry *entry, *dupentry;
640	int ret;
641	unsigned int dlen = PAGE_SIZE, len;
642	unsigned long handle;
643	char *buf;
644	u8 *src, *dst;
645	struct zswap_header *zhdr;
646
647	if (!tree) {
648		ret = -ENODEV;
649		goto reject;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
650	}
651
652	/* reclaim space if needed */
653	if (zswap_is_full()) {
654		zswap_pool_limit_hit++;
655		if (zbud_reclaim_page(zswap_pool, 8)) {
656			zswap_reject_reclaim_fail++;
657			ret = -ENOMEM;
658			goto reject;
659		}
 
 
 
 
660	}
661
662	/* allocate entry */
663	entry = zswap_entry_cache_alloc(GFP_KERNEL);
664	if (!entry) {
665		zswap_reject_kmemcache_fail++;
666		ret = -ENOMEM;
667		goto reject;
668	}
669
670	/* compress */
671	dst = get_cpu_var(zswap_dstmem);
672	src = kmap_atomic(page);
673	ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
674	kunmap_atomic(src);
675	if (ret) {
676		ret = -EINVAL;
677		goto freepage;
 
 
 
 
 
678	}
679
680	/* store */
681	len = dlen + sizeof(struct zswap_header);
682	ret = zbud_alloc(zswap_pool, len, __GFP_NORETRY | __GFP_NOWARN,
683		&handle);
684	if (ret == -ENOSPC) {
685		zswap_reject_compress_poor++;
686		goto freepage;
687	}
688	if (ret) {
689		zswap_reject_alloc_fail++;
 
690		goto freepage;
 
 
 
 
 
 
 
 
691	}
692	zhdr = zbud_map(zswap_pool, handle);
693	zhdr->swpentry = swp_entry(type, offset);
694	buf = (u8 *)(zhdr + 1);
695	memcpy(buf, dst, dlen);
696	zbud_unmap(zswap_pool, handle);
697	put_cpu_var(zswap_dstmem);
698
699	/* populate entry */
700	entry->offset = offset;
701	entry->handle = handle;
702	entry->length = dlen;
 
 
 
 
 
 
 
703
704	/* map */
705	spin_lock(&tree->lock);
706	do {
707		ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
708		if (ret == -EEXIST) {
709			zswap_duplicate_entry++;
710			/* remove from rbtree */
711			zswap_rb_erase(&tree->rbroot, dupentry);
712			zswap_entry_put(tree, dupentry);
713		}
714	} while (ret == -EEXIST);
 
 
 
 
715	spin_unlock(&tree->lock);
716
717	/* update stats */
718	atomic_inc(&zswap_stored_pages);
719	zswap_pool_pages = zbud_get_pool_size(zswap_pool);
 
720
721	return 0;
722
 
 
723freepage:
724	put_cpu_var(zswap_dstmem);
725	zswap_entry_cache_free(entry);
726reject:
727	return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
728}
729
730/*
731 * returns 0 if the page was successfully decompressed
732 * return -1 on entry not found or error
733*/
734static int zswap_frontswap_load(unsigned type, pgoff_t offset,
735				struct page *page)
736{
737	struct zswap_tree *tree = zswap_trees[type];
 
 
 
 
738	struct zswap_entry *entry;
739	u8 *src, *dst;
740	unsigned int dlen;
741	int ret;
742
743	/* find */
744	spin_lock(&tree->lock);
745	entry = zswap_entry_find_get(&tree->rbroot, offset);
746	if (!entry) {
747		/* entry was written back */
748		spin_unlock(&tree->lock);
749		return -1;
750	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
751	spin_unlock(&tree->lock);
752
753	/* decompress */
754	dlen = PAGE_SIZE;
755	src = (u8 *)zbud_map(zswap_pool, entry->handle) +
756			sizeof(struct zswap_header);
757	dst = kmap_atomic(page);
758	ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
759		dst, &dlen);
760	kunmap_atomic(dst);
761	zbud_unmap(zswap_pool, entry->handle);
762	BUG_ON(ret);
763
764	spin_lock(&tree->lock);
765	zswap_entry_put(tree, entry);
766	spin_unlock(&tree->lock);
767
768	return 0;
 
 
 
 
 
769}
770
771/* frees an entry in zswap */
772static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
773{
774	struct zswap_tree *tree = zswap_trees[type];
 
775	struct zswap_entry *entry;
776
777	/* find */
778	spin_lock(&tree->lock);
779	entry = zswap_rb_search(&tree->rbroot, offset);
780	if (!entry) {
781		/* entry was written back */
782		spin_unlock(&tree->lock);
783		return;
784	}
785
786	/* remove from rbtree */
787	zswap_rb_erase(&tree->rbroot, entry);
788
789	/* drop the initial reference from entry creation */
790	zswap_entry_put(tree, entry);
791
792	spin_unlock(&tree->lock);
793}
794
795/* frees all zswap entries for the given swap type */
796static void zswap_frontswap_invalidate_area(unsigned type)
797{
798	struct zswap_tree *tree = zswap_trees[type];
799	struct zswap_entry *entry, *n;
800
801	if (!tree)
802		return;
 
 
 
 
803
804	/* walk the tree and free everything */
805	spin_lock(&tree->lock);
806	rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
807		zswap_free_entry(entry);
808	tree->rbroot = RB_ROOT;
809	spin_unlock(&tree->lock);
810	kfree(tree);
811	zswap_trees[type] = NULL;
812}
813
814static struct zbud_ops zswap_zbud_ops = {
815	.evict = zswap_writeback_entry
816};
 
817
818static void zswap_frontswap_init(unsigned type)
819{
820	struct zswap_tree *tree;
 
821
822	tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
823	if (!tree) {
824		pr_err("alloc failed, zswap disabled for swap type %d\n", type);
825		return;
826	}
827
828	tree->rbroot = RB_ROOT;
829	spin_lock_init(&tree->lock);
830	zswap_trees[type] = tree;
831}
832
833static struct frontswap_ops zswap_frontswap_ops = {
834	.store = zswap_frontswap_store,
835	.load = zswap_frontswap_load,
836	.invalidate_page = zswap_frontswap_invalidate_page,
837	.invalidate_area = zswap_frontswap_invalidate_area,
838	.init = zswap_frontswap_init
839};
840
841/*********************************
842* debugfs functions
843**********************************/
844#ifdef CONFIG_DEBUG_FS
845#include <linux/debugfs.h>
846
847static struct dentry *zswap_debugfs_root;
848
849static int __init zswap_debugfs_init(void)
850{
851	if (!debugfs_initialized())
852		return -ENODEV;
853
854	zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
855	if (!zswap_debugfs_root)
856		return -ENOMEM;
857
858	debugfs_create_u64("pool_limit_hit", S_IRUGO,
859			zswap_debugfs_root, &zswap_pool_limit_hit);
860	debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
861			zswap_debugfs_root, &zswap_reject_reclaim_fail);
862	debugfs_create_u64("reject_alloc_fail", S_IRUGO,
863			zswap_debugfs_root, &zswap_reject_alloc_fail);
864	debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
865			zswap_debugfs_root, &zswap_reject_kmemcache_fail);
866	debugfs_create_u64("reject_compress_poor", S_IRUGO,
867			zswap_debugfs_root, &zswap_reject_compress_poor);
868	debugfs_create_u64("written_back_pages", S_IRUGO,
869			zswap_debugfs_root, &zswap_written_back_pages);
870	debugfs_create_u64("duplicate_entry", S_IRUGO,
871			zswap_debugfs_root, &zswap_duplicate_entry);
872	debugfs_create_u64("pool_pages", S_IRUGO,
873			zswap_debugfs_root, &zswap_pool_pages);
874	debugfs_create_atomic_t("stored_pages", S_IRUGO,
875			zswap_debugfs_root, &zswap_stored_pages);
 
 
876
877	return 0;
878}
879
880static void __exit zswap_debugfs_exit(void)
881{
882	debugfs_remove_recursive(zswap_debugfs_root);
883}
884#else
885static int __init zswap_debugfs_init(void)
886{
887	return 0;
888}
889
890static void __exit zswap_debugfs_exit(void) { }
891#endif
892
893/*********************************
894* module init and exit
895**********************************/
896static int __init init_zswap(void)
897{
898	if (!zswap_enabled)
899		return 0;
900
901	pr_info("loading zswap\n");
902
903	zswap_pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops);
904	if (!zswap_pool) {
905		pr_err("zbud pool creation failed\n");
906		goto error;
907	}
908
909	if (zswap_entry_cache_create()) {
 
910		pr_err("entry cache creation failed\n");
911		goto cachefail;
912	}
913	if (zswap_comp_init()) {
914		pr_err("compressor initialization failed\n");
915		goto compfail;
916	}
917	if (zswap_cpu_init()) {
918		pr_err("per-cpu initialization failed\n");
919		goto pcpufail;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
920	}
921
922	frontswap_register_ops(&zswap_frontswap_ops);
923	if (zswap_debugfs_init())
924		pr_warn("debugfs initialization failed\n");
 
925	return 0;
926pcpufail:
927	zswap_comp_exit();
928compfail:
929	zswap_entry_cache_destory();
930cachefail:
931	zbud_destroy_pool(zswap_pool);
932error:
 
 
 
 
 
 
933	return -ENOMEM;
934}
 
 
 
 
 
 
 
935/* must be late so crypto has time to come up */
936late_initcall(init_zswap);
937
938MODULE_LICENSE("GPL");
939MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
940MODULE_DESCRIPTION("Compressed cache for swap pages");