dm: make flush bios explicitly sync
[sfrench/cifs-2.6.git] / drivers / md / dm-bufio.c
1 /*
2  * Copyright (C) 2009-2011 Red Hat, Inc.
3  *
4  * Author: Mikulas Patocka <mpatocka@redhat.com>
5  *
6  * This file is released under the GPL.
7  */
8
9 #include "dm-bufio.h"
10
11 #include <linux/device-mapper.h>
12 #include <linux/dm-io.h>
13 #include <linux/slab.h>
14 #include <linux/sched/mm.h>
15 #include <linux/jiffies.h>
16 #include <linux/vmalloc.h>
17 #include <linux/shrinker.h>
18 #include <linux/module.h>
19 #include <linux/rbtree.h>
20 #include <linux/stacktrace.h>
21
22 #define DM_MSG_PREFIX "bufio"
23
24 /*
25  * Memory management policy:
26  *      Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
27  *      or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
28  *      Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
29  *      Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
30  *      dirty buffers.
31  */
32 #define DM_BUFIO_MIN_BUFFERS            8
33
34 #define DM_BUFIO_MEMORY_PERCENT         2
35 #define DM_BUFIO_VMALLOC_PERCENT        25
36 #define DM_BUFIO_WRITEBACK_PERCENT      75
37
38 /*
39  * Check buffer ages in this interval (seconds)
40  */
41 #define DM_BUFIO_WORK_TIMER_SECS        30
42
43 /*
44  * Free buffers when they are older than this (seconds)
45  */
46 #define DM_BUFIO_DEFAULT_AGE_SECS       300
47
48 /*
49  * The nr of bytes of cached data to keep around.
50  */
51 #define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)
52
53 /*
54  * The number of bvec entries that are embedded directly in the buffer.
55  * If the chunk size is larger, dm-io is used to do the io.
56  */
57 #define DM_BUFIO_INLINE_VECS            16
58
59 /*
60  * Don't try to use kmem_cache_alloc for blocks larger than this.
61  * For explanation, see alloc_buffer_data below.
62  */
63 #define DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT  (PAGE_SIZE >> 1)
64 #define DM_BUFIO_BLOCK_SIZE_GFP_LIMIT   (PAGE_SIZE << (MAX_ORDER - 1))
65
66 /*
67  * dm_buffer->list_mode
68  */
69 #define LIST_CLEAN      0
70 #define LIST_DIRTY      1
71 #define LIST_SIZE       2
72
73 /*
74  * Linking of buffers:
75  *      All buffers are linked to cache_hash with their hash_list field.
76  *
77  *      Clean buffers that are not being written (B_WRITING not set)
78  *      are linked to lru[LIST_CLEAN] with their lru_list field.
79  *
80  *      Dirty and clean buffers that are being written are linked to
81  *      lru[LIST_DIRTY] with their lru_list field. When the write
82  *      finishes, the buffer cannot be relinked immediately (because we
83  *      are in an interrupt context and relinking requires process
84  *      context), so some clean-not-writing buffers can be held on
85  *      dirty_lru too.  They are later added to lru in the process
86  *      context.
87  */
88 struct dm_bufio_client {
89         struct mutex lock;
90
91         struct list_head lru[LIST_SIZE];
92         unsigned long n_buffers[LIST_SIZE];
93
94         struct block_device *bdev;
95         unsigned block_size;
96         unsigned char sectors_per_block_bits;
97         unsigned char pages_per_block_bits;
98         unsigned char blocks_per_page_bits;
99         unsigned aux_size;
100         void (*alloc_callback)(struct dm_buffer *);
101         void (*write_callback)(struct dm_buffer *);
102
103         struct dm_io_client *dm_io;
104
105         struct list_head reserved_buffers;
106         unsigned need_reserved_buffers;
107
108         unsigned minimum_buffers;
109
110         struct rb_root buffer_tree;
111         wait_queue_head_t free_buffer_wait;
112
113         sector_t start;
114
115         int async_write_error;
116
117         struct list_head client_list;
118         struct shrinker shrinker;
119 };
120
121 /*
122  * Buffer state bits.
123  */
124 #define B_READING       0
125 #define B_WRITING       1
126 #define B_DIRTY         2
127
128 /*
129  * Describes how the block was allocated:
130  * kmem_cache_alloc(), __get_free_pages() or vmalloc().
131  * See the comment at alloc_buffer_data.
132  */
133 enum data_mode {
134         DATA_MODE_SLAB = 0,
135         DATA_MODE_GET_FREE_PAGES = 1,
136         DATA_MODE_VMALLOC = 2,
137         DATA_MODE_LIMIT = 3
138 };
139
140 struct dm_buffer {
141         struct rb_node node;
142         struct list_head lru_list;
143         sector_t block;
144         void *data;
145         enum data_mode data_mode;
146         unsigned char list_mode;                /* LIST_* */
147         unsigned hold_count;
148         int read_error;
149         int write_error;
150         unsigned long state;
151         unsigned long last_accessed;
152         struct dm_bufio_client *c;
153         struct list_head write_list;
154         struct bio bio;
155         struct bio_vec bio_vec[DM_BUFIO_INLINE_VECS];
156 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
157 #define MAX_STACK 10
158         struct stack_trace stack_trace;
159         unsigned long stack_entries[MAX_STACK];
160 #endif
161 };
162
163 /*----------------------------------------------------------------*/
164
165 static struct kmem_cache *dm_bufio_caches[PAGE_SHIFT - SECTOR_SHIFT];
166 static char *dm_bufio_cache_names[PAGE_SHIFT - SECTOR_SHIFT];
167
168 static inline int dm_bufio_cache_index(struct dm_bufio_client *c)
169 {
170         unsigned ret = c->blocks_per_page_bits - 1;
171
172         BUG_ON(ret >= ARRAY_SIZE(dm_bufio_caches));
173
174         return ret;
175 }
176
177 #define DM_BUFIO_CACHE(c)       (dm_bufio_caches[dm_bufio_cache_index(c)])
178 #define DM_BUFIO_CACHE_NAME(c)  (dm_bufio_cache_names[dm_bufio_cache_index(c)])
179
180 #define dm_bufio_in_request()   (!!current->bio_list)
181
182 static void dm_bufio_lock(struct dm_bufio_client *c)
183 {
184         mutex_lock_nested(&c->lock, dm_bufio_in_request());
185 }
186
187 static int dm_bufio_trylock(struct dm_bufio_client *c)
188 {
189         return mutex_trylock(&c->lock);
190 }
191
192 static void dm_bufio_unlock(struct dm_bufio_client *c)
193 {
194         mutex_unlock(&c->lock);
195 }
196
197 /*----------------------------------------------------------------*/
198
199 /*
200  * Default cache size: available memory divided by the ratio.
201  */
202 static unsigned long dm_bufio_default_cache_size;
203
204 /*
205  * Total cache size set by the user.
206  */
207 static unsigned long dm_bufio_cache_size;
208
209 /*
210  * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
211  * at any time.  If it disagrees, the user has changed cache size.
212  */
213 static unsigned long dm_bufio_cache_size_latch;
214
215 static DEFINE_SPINLOCK(param_spinlock);
216
217 /*
218  * Buffers are freed after this timeout
219  */
220 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS;
221 static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES;
222
223 static unsigned long dm_bufio_peak_allocated;
224 static unsigned long dm_bufio_allocated_kmem_cache;
225 static unsigned long dm_bufio_allocated_get_free_pages;
226 static unsigned long dm_bufio_allocated_vmalloc;
227 static unsigned long dm_bufio_current_allocated;
228
229 /*----------------------------------------------------------------*/
230
231 /*
232  * Per-client cache: dm_bufio_cache_size / dm_bufio_client_count
233  */
234 static unsigned long dm_bufio_cache_size_per_client;
235
236 /*
237  * The current number of clients.
238  */
239 static int dm_bufio_client_count;
240
241 /*
242  * The list of all clients.
243  */
244 static LIST_HEAD(dm_bufio_all_clients);
245
246 /*
247  * This mutex protects dm_bufio_cache_size_latch,
248  * dm_bufio_cache_size_per_client and dm_bufio_client_count
249  */
250 static DEFINE_MUTEX(dm_bufio_clients_lock);
251
252 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
253 static void buffer_record_stack(struct dm_buffer *b)
254 {
255         b->stack_trace.nr_entries = 0;
256         b->stack_trace.max_entries = MAX_STACK;
257         b->stack_trace.entries = b->stack_entries;
258         b->stack_trace.skip = 2;
259         save_stack_trace(&b->stack_trace);
260 }
261 #endif
262
263 /*----------------------------------------------------------------
264  * A red/black tree acts as an index for all the buffers.
265  *--------------------------------------------------------------*/
266 static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block)
267 {
268         struct rb_node *n = c->buffer_tree.rb_node;
269         struct dm_buffer *b;
270
271         while (n) {
272                 b = container_of(n, struct dm_buffer, node);
273
274                 if (b->block == block)
275                         return b;
276
277                 n = (b->block < block) ? n->rb_left : n->rb_right;
278         }
279
280         return NULL;
281 }
282
283 static void __insert(struct dm_bufio_client *c, struct dm_buffer *b)
284 {
285         struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL;
286         struct dm_buffer *found;
287
288         while (*new) {
289                 found = container_of(*new, struct dm_buffer, node);
290
291                 if (found->block == b->block) {
292                         BUG_ON(found != b);
293                         return;
294                 }
295
296                 parent = *new;
297                 new = (found->block < b->block) ?
298                         &((*new)->rb_left) : &((*new)->rb_right);
299         }
300
301         rb_link_node(&b->node, parent, new);
302         rb_insert_color(&b->node, &c->buffer_tree);
303 }
304
305 static void __remove(struct dm_bufio_client *c, struct dm_buffer *b)
306 {
307         rb_erase(&b->node, &c->buffer_tree);
308 }
309
310 /*----------------------------------------------------------------*/
311
312 static void adjust_total_allocated(enum data_mode data_mode, long diff)
313 {
314         static unsigned long * const class_ptr[DATA_MODE_LIMIT] = {
315                 &dm_bufio_allocated_kmem_cache,
316                 &dm_bufio_allocated_get_free_pages,
317                 &dm_bufio_allocated_vmalloc,
318         };
319
320         spin_lock(&param_spinlock);
321
322         *class_ptr[data_mode] += diff;
323
324         dm_bufio_current_allocated += diff;
325
326         if (dm_bufio_current_allocated > dm_bufio_peak_allocated)
327                 dm_bufio_peak_allocated = dm_bufio_current_allocated;
328
329         spin_unlock(&param_spinlock);
330 }
331
332 /*
333  * Change the number of clients and recalculate per-client limit.
334  */
335 static void __cache_size_refresh(void)
336 {
337         BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock));
338         BUG_ON(dm_bufio_client_count < 0);
339
340         dm_bufio_cache_size_latch = ACCESS_ONCE(dm_bufio_cache_size);
341
342         /*
343          * Use default if set to 0 and report the actual cache size used.
344          */
345         if (!dm_bufio_cache_size_latch) {
346                 (void)cmpxchg(&dm_bufio_cache_size, 0,
347                               dm_bufio_default_cache_size);
348                 dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
349         }
350
351         dm_bufio_cache_size_per_client = dm_bufio_cache_size_latch /
352                                          (dm_bufio_client_count ? : 1);
353 }
354
355 /*
356  * Allocating buffer data.
357  *
358  * Small buffers are allocated with kmem_cache, to use space optimally.
359  *
360  * For large buffers, we choose between get_free_pages and vmalloc.
361  * Each has advantages and disadvantages.
362  *
363  * __get_free_pages can randomly fail if the memory is fragmented.
364  * __vmalloc won't randomly fail, but vmalloc space is limited (it may be
365  * as low as 128M) so using it for caching is not appropriate.
366  *
367  * If the allocation may fail we use __get_free_pages. Memory fragmentation
368  * won't have a fatal effect here, but it just causes flushes of some other
369  * buffers and more I/O will be performed. Don't use __get_free_pages if it
370  * always fails (i.e. order >= MAX_ORDER).
371  *
372  * If the allocation shouldn't fail we use __vmalloc. This is only for the
373  * initial reserve allocation, so there's no risk of wasting all vmalloc
374  * space.
375  */
376 static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
377                                enum data_mode *data_mode)
378 {
379         unsigned noio_flag;
380         void *ptr;
381
382         if (c->block_size <= DM_BUFIO_BLOCK_SIZE_SLAB_LIMIT) {
383                 *data_mode = DATA_MODE_SLAB;
384                 return kmem_cache_alloc(DM_BUFIO_CACHE(c), gfp_mask);
385         }
386
387         if (c->block_size <= DM_BUFIO_BLOCK_SIZE_GFP_LIMIT &&
388             gfp_mask & __GFP_NORETRY) {
389                 *data_mode = DATA_MODE_GET_FREE_PAGES;
390                 return (void *)__get_free_pages(gfp_mask,
391                                                 c->pages_per_block_bits);
392         }
393
394         *data_mode = DATA_MODE_VMALLOC;
395
396         /*
397          * __vmalloc allocates the data pages and auxiliary structures with
398          * gfp_flags that were specified, but pagetables are always allocated
399          * with GFP_KERNEL, no matter what was specified as gfp_mask.
400          *
401          * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
402          * all allocations done by this process (including pagetables) are done
403          * as if GFP_NOIO was specified.
404          */
405
406         if (gfp_mask & __GFP_NORETRY)
407                 noio_flag = memalloc_noio_save();
408
409         ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL);
410
411         if (gfp_mask & __GFP_NORETRY)
412                 memalloc_noio_restore(noio_flag);
413
414         return ptr;
415 }
416
417 /*
418  * Free buffer's data.
419  */
420 static void free_buffer_data(struct dm_bufio_client *c,
421                              void *data, enum data_mode data_mode)
422 {
423         switch (data_mode) {
424         case DATA_MODE_SLAB:
425                 kmem_cache_free(DM_BUFIO_CACHE(c), data);
426                 break;
427
428         case DATA_MODE_GET_FREE_PAGES:
429                 free_pages((unsigned long)data, c->pages_per_block_bits);
430                 break;
431
432         case DATA_MODE_VMALLOC:
433                 vfree(data);
434                 break;
435
436         default:
437                 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d",
438                        data_mode);
439                 BUG();
440         }
441 }
442
443 /*
444  * Allocate buffer and its data.
445  */
446 static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask)
447 {
448         struct dm_buffer *b = kmalloc(sizeof(struct dm_buffer) + c->aux_size,
449                                       gfp_mask);
450
451         if (!b)
452                 return NULL;
453
454         b->c = c;
455
456         b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode);
457         if (!b->data) {
458                 kfree(b);
459                 return NULL;
460         }
461
462         adjust_total_allocated(b->data_mode, (long)c->block_size);
463
464 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
465         memset(&b->stack_trace, 0, sizeof(b->stack_trace));
466 #endif
467         return b;
468 }
469
470 /*
471  * Free buffer and its data.
472  */
473 static void free_buffer(struct dm_buffer *b)
474 {
475         struct dm_bufio_client *c = b->c;
476
477         adjust_total_allocated(b->data_mode, -(long)c->block_size);
478
479         free_buffer_data(c, b->data, b->data_mode);
480         kfree(b);
481 }
482
483 /*
484  * Link buffer to the hash list and clean or dirty queue.
485  */
486 static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty)
487 {
488         struct dm_bufio_client *c = b->c;
489
490         c->n_buffers[dirty]++;
491         b->block = block;
492         b->list_mode = dirty;
493         list_add(&b->lru_list, &c->lru[dirty]);
494         __insert(b->c, b);
495         b->last_accessed = jiffies;
496 }
497
498 /*
499  * Unlink buffer from the hash list and dirty or clean queue.
500  */
501 static void __unlink_buffer(struct dm_buffer *b)
502 {
503         struct dm_bufio_client *c = b->c;
504
505         BUG_ON(!c->n_buffers[b->list_mode]);
506
507         c->n_buffers[b->list_mode]--;
508         __remove(b->c, b);
509         list_del(&b->lru_list);
510 }
511
512 /*
513  * Place the buffer to the head of dirty or clean LRU queue.
514  */
515 static void __relink_lru(struct dm_buffer *b, int dirty)
516 {
517         struct dm_bufio_client *c = b->c;
518
519         BUG_ON(!c->n_buffers[b->list_mode]);
520
521         c->n_buffers[b->list_mode]--;
522         c->n_buffers[dirty]++;
523         b->list_mode = dirty;
524         list_move(&b->lru_list, &c->lru[dirty]);
525         b->last_accessed = jiffies;
526 }
527
528 /*----------------------------------------------------------------
529  * Submit I/O on the buffer.
530  *
531  * Bio interface is faster but it has some problems:
532  *      the vector list is limited (increasing this limit increases
533  *      memory-consumption per buffer, so it is not viable);
534  *
535  *      the memory must be direct-mapped, not vmalloced;
536  *
537  *      the I/O driver can reject requests spuriously if it thinks that
538  *      the requests are too big for the device or if they cross a
539  *      controller-defined memory boundary.
540  *
541  * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
542  * it is not vmalloced, try using the bio interface.
543  *
544  * If the buffer is big, if it is vmalloced or if the underlying device
545  * rejects the bio because it is too large, use dm-io layer to do the I/O.
546  * The dm-io layer splits the I/O into multiple requests, avoiding the above
547  * shortcomings.
548  *--------------------------------------------------------------*/
549
550 /*
551  * dm-io completion routine. It just calls b->bio.bi_end_io, pretending
552  * that the request was handled directly with bio interface.
553  */
554 static void dmio_complete(unsigned long error, void *context)
555 {
556         struct dm_buffer *b = context;
557
558         b->bio.bi_error = error ? -EIO : 0;
559         b->bio.bi_end_io(&b->bio);
560 }
561
562 static void use_dmio(struct dm_buffer *b, int rw, sector_t sector,
563                      unsigned n_sectors, bio_end_io_t *end_io)
564 {
565         int r;
566         struct dm_io_request io_req = {
567                 .bi_op = rw,
568                 .bi_op_flags = 0,
569                 .notify.fn = dmio_complete,
570                 .notify.context = b,
571                 .client = b->c->dm_io,
572         };
573         struct dm_io_region region = {
574                 .bdev = b->c->bdev,
575                 .sector = sector,
576                 .count = n_sectors,
577         };
578
579         if (b->data_mode != DATA_MODE_VMALLOC) {
580                 io_req.mem.type = DM_IO_KMEM;
581                 io_req.mem.ptr.addr = b->data;
582         } else {
583                 io_req.mem.type = DM_IO_VMA;
584                 io_req.mem.ptr.vma = b->data;
585         }
586
587         b->bio.bi_end_io = end_io;
588
589         r = dm_io(&io_req, 1, &region, NULL);
590         if (r) {
591                 b->bio.bi_error = r;
592                 end_io(&b->bio);
593         }
594 }
595
596 static void inline_endio(struct bio *bio)
597 {
598         bio_end_io_t *end_fn = bio->bi_private;
599         int error = bio->bi_error;
600
601         /*
602          * Reset the bio to free any attached resources
603          * (e.g. bio integrity profiles).
604          */
605         bio_reset(bio);
606
607         bio->bi_error = error;
608         end_fn(bio);
609 }
610
611 static void use_inline_bio(struct dm_buffer *b, int rw, sector_t sector,
612                            unsigned n_sectors, bio_end_io_t *end_io)
613 {
614         char *ptr;
615         int len;
616
617         bio_init(&b->bio, b->bio_vec, DM_BUFIO_INLINE_VECS);
618         b->bio.bi_iter.bi_sector = sector;
619         b->bio.bi_bdev = b->c->bdev;
620         b->bio.bi_end_io = inline_endio;
621         /*
622          * Use of .bi_private isn't a problem here because
623          * the dm_buffer's inline bio is local to bufio.
624          */
625         b->bio.bi_private = end_io;
626         bio_set_op_attrs(&b->bio, rw, 0);
627
628         /*
629          * We assume that if len >= PAGE_SIZE ptr is page-aligned.
630          * If len < PAGE_SIZE the buffer doesn't cross page boundary.
631          */
632         ptr = b->data;
633         len = n_sectors << SECTOR_SHIFT;
634
635         if (len >= PAGE_SIZE)
636                 BUG_ON((unsigned long)ptr & (PAGE_SIZE - 1));
637         else
638                 BUG_ON((unsigned long)ptr & (len - 1));
639
640         do {
641                 if (!bio_add_page(&b->bio, virt_to_page(ptr),
642                                   len < PAGE_SIZE ? len : PAGE_SIZE,
643                                   offset_in_page(ptr))) {
644                         BUG_ON(b->c->block_size <= PAGE_SIZE);
645                         use_dmio(b, rw, sector, n_sectors, end_io);
646                         return;
647                 }
648
649                 len -= PAGE_SIZE;
650                 ptr += PAGE_SIZE;
651         } while (len > 0);
652
653         submit_bio(&b->bio);
654 }
655
656 static void submit_io(struct dm_buffer *b, int rw, bio_end_io_t *end_io)
657 {
658         unsigned n_sectors;
659         sector_t sector;
660
661         if (rw == WRITE && b->c->write_callback)
662                 b->c->write_callback(b);
663
664         sector = (b->block << b->c->sectors_per_block_bits) + b->c->start;
665         n_sectors = 1 << b->c->sectors_per_block_bits;
666
667         if (n_sectors <= ((DM_BUFIO_INLINE_VECS * PAGE_SIZE) >> SECTOR_SHIFT) &&
668             b->data_mode != DATA_MODE_VMALLOC)
669                 use_inline_bio(b, rw, sector, n_sectors, end_io);
670         else
671                 use_dmio(b, rw, sector, n_sectors, end_io);
672 }
673
674 /*----------------------------------------------------------------
675  * Writing dirty buffers
676  *--------------------------------------------------------------*/
677
678 /*
679  * The endio routine for write.
680  *
681  * Set the error, clear B_WRITING bit and wake anyone who was waiting on
682  * it.
683  */
684 static void write_endio(struct bio *bio)
685 {
686         struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
687
688         b->write_error = bio->bi_error;
689         if (unlikely(bio->bi_error)) {
690                 struct dm_bufio_client *c = b->c;
691                 int error = bio->bi_error;
692                 (void)cmpxchg(&c->async_write_error, 0, error);
693         }
694
695         BUG_ON(!test_bit(B_WRITING, &b->state));
696
697         smp_mb__before_atomic();
698         clear_bit(B_WRITING, &b->state);
699         smp_mb__after_atomic();
700
701         wake_up_bit(&b->state, B_WRITING);
702 }
703
704 /*
705  * Initiate a write on a dirty buffer, but don't wait for it.
706  *
707  * - If the buffer is not dirty, exit.
708  * - If there some previous write going on, wait for it to finish (we can't
709  *   have two writes on the same buffer simultaneously).
710  * - Submit our write and don't wait on it. We set B_WRITING indicating
711  *   that there is a write in progress.
712  */
713 static void __write_dirty_buffer(struct dm_buffer *b,
714                                  struct list_head *write_list)
715 {
716         if (!test_bit(B_DIRTY, &b->state))
717                 return;
718
719         clear_bit(B_DIRTY, &b->state);
720         wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
721
722         if (!write_list)
723                 submit_io(b, WRITE, write_endio);
724         else
725                 list_add_tail(&b->write_list, write_list);
726 }
727
728 static void __flush_write_list(struct list_head *write_list)
729 {
730         struct blk_plug plug;
731         blk_start_plug(&plug);
732         while (!list_empty(write_list)) {
733                 struct dm_buffer *b =
734                         list_entry(write_list->next, struct dm_buffer, write_list);
735                 list_del(&b->write_list);
736                 submit_io(b, WRITE, write_endio);
737                 cond_resched();
738         }
739         blk_finish_plug(&plug);
740 }
741
742 /*
743  * Wait until any activity on the buffer finishes.  Possibly write the
744  * buffer if it is dirty.  When this function finishes, there is no I/O
745  * running on the buffer and the buffer is not dirty.
746  */
747 static void __make_buffer_clean(struct dm_buffer *b)
748 {
749         BUG_ON(b->hold_count);
750
751         if (!b->state)  /* fast case */
752                 return;
753
754         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
755         __write_dirty_buffer(b, NULL);
756         wait_on_bit_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE);
757 }
758
759 /*
760  * Find some buffer that is not held by anybody, clean it, unlink it and
761  * return it.
762  */
763 static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
764 {
765         struct dm_buffer *b;
766
767         list_for_each_entry_reverse(b, &c->lru[LIST_CLEAN], lru_list) {
768                 BUG_ON(test_bit(B_WRITING, &b->state));
769                 BUG_ON(test_bit(B_DIRTY, &b->state));
770
771                 if (!b->hold_count) {
772                         __make_buffer_clean(b);
773                         __unlink_buffer(b);
774                         return b;
775                 }
776                 cond_resched();
777         }
778
779         list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
780                 BUG_ON(test_bit(B_READING, &b->state));
781
782                 if (!b->hold_count) {
783                         __make_buffer_clean(b);
784                         __unlink_buffer(b);
785                         return b;
786                 }
787                 cond_resched();
788         }
789
790         return NULL;
791 }
792
793 /*
794  * Wait until some other threads free some buffer or release hold count on
795  * some buffer.
796  *
797  * This function is entered with c->lock held, drops it and regains it
798  * before exiting.
799  */
800 static void __wait_for_free_buffer(struct dm_bufio_client *c)
801 {
802         DECLARE_WAITQUEUE(wait, current);
803
804         add_wait_queue(&c->free_buffer_wait, &wait);
805         set_current_state(TASK_UNINTERRUPTIBLE);
806         dm_bufio_unlock(c);
807
808         io_schedule();
809
810         remove_wait_queue(&c->free_buffer_wait, &wait);
811
812         dm_bufio_lock(c);
813 }
814
815 enum new_flag {
816         NF_FRESH = 0,
817         NF_READ = 1,
818         NF_GET = 2,
819         NF_PREFETCH = 3
820 };
821
822 /*
823  * Allocate a new buffer. If the allocation is not possible, wait until
824  * some other thread frees a buffer.
825  *
826  * May drop the lock and regain it.
827  */
828 static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client *c, enum new_flag nf)
829 {
830         struct dm_buffer *b;
831         bool tried_noio_alloc = false;
832
833         /*
834          * dm-bufio is resistant to allocation failures (it just keeps
835          * one buffer reserved in cases all the allocations fail).
836          * So set flags to not try too hard:
837          *      GFP_NOWAIT: don't wait; if we need to sleep we'll release our
838          *                  mutex and wait ourselves.
839          *      __GFP_NORETRY: don't retry and rather return failure
840          *      __GFP_NOMEMALLOC: don't use emergency reserves
841          *      __GFP_NOWARN: don't print a warning in case of failure
842          *
843          * For debugging, if we set the cache size to 1, no new buffers will
844          * be allocated.
845          */
846         while (1) {
847                 if (dm_bufio_cache_size_latch != 1) {
848                         b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
849                         if (b)
850                                 return b;
851                 }
852
853                 if (nf == NF_PREFETCH)
854                         return NULL;
855
856                 if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
857                         dm_bufio_unlock(c);
858                         b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
859                         dm_bufio_lock(c);
860                         if (b)
861                                 return b;
862                         tried_noio_alloc = true;
863                 }
864
865                 if (!list_empty(&c->reserved_buffers)) {
866                         b = list_entry(c->reserved_buffers.next,
867                                        struct dm_buffer, lru_list);
868                         list_del(&b->lru_list);
869                         c->need_reserved_buffers++;
870
871                         return b;
872                 }
873
874                 b = __get_unclaimed_buffer(c);
875                 if (b)
876                         return b;
877
878                 __wait_for_free_buffer(c);
879         }
880 }
881
882 static struct dm_buffer *__alloc_buffer_wait(struct dm_bufio_client *c, enum new_flag nf)
883 {
884         struct dm_buffer *b = __alloc_buffer_wait_no_callback(c, nf);
885
886         if (!b)
887                 return NULL;
888
889         if (c->alloc_callback)
890                 c->alloc_callback(b);
891
892         return b;
893 }
894
895 /*
896  * Free a buffer and wake other threads waiting for free buffers.
897  */
898 static void __free_buffer_wake(struct dm_buffer *b)
899 {
900         struct dm_bufio_client *c = b->c;
901
902         if (!c->need_reserved_buffers)
903                 free_buffer(b);
904         else {
905                 list_add(&b->lru_list, &c->reserved_buffers);
906                 c->need_reserved_buffers--;
907         }
908
909         wake_up(&c->free_buffer_wait);
910 }
911
912 static void __write_dirty_buffers_async(struct dm_bufio_client *c, int no_wait,
913                                         struct list_head *write_list)
914 {
915         struct dm_buffer *b, *tmp;
916
917         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
918                 BUG_ON(test_bit(B_READING, &b->state));
919
920                 if (!test_bit(B_DIRTY, &b->state) &&
921                     !test_bit(B_WRITING, &b->state)) {
922                         __relink_lru(b, LIST_CLEAN);
923                         continue;
924                 }
925
926                 if (no_wait && test_bit(B_WRITING, &b->state))
927                         return;
928
929                 __write_dirty_buffer(b, write_list);
930                 cond_resched();
931         }
932 }
933
934 /*
935  * Get writeback threshold and buffer limit for a given client.
936  */
937 static void __get_memory_limit(struct dm_bufio_client *c,
938                                unsigned long *threshold_buffers,
939                                unsigned long *limit_buffers)
940 {
941         unsigned long buffers;
942
943         if (unlikely(ACCESS_ONCE(dm_bufio_cache_size) != dm_bufio_cache_size_latch)) {
944                 if (mutex_trylock(&dm_bufio_clients_lock)) {
945                         __cache_size_refresh();
946                         mutex_unlock(&dm_bufio_clients_lock);
947                 }
948         }
949
950         buffers = dm_bufio_cache_size_per_client >>
951                   (c->sectors_per_block_bits + SECTOR_SHIFT);
952
953         if (buffers < c->minimum_buffers)
954                 buffers = c->minimum_buffers;
955
956         *limit_buffers = buffers;
957         *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
958 }
959
960 /*
961  * Check if we're over watermark.
962  * If we are over threshold_buffers, start freeing buffers.
963  * If we're over "limit_buffers", block until we get under the limit.
964  */
965 static void __check_watermark(struct dm_bufio_client *c,
966                               struct list_head *write_list)
967 {
968         unsigned long threshold_buffers, limit_buffers;
969
970         __get_memory_limit(c, &threshold_buffers, &limit_buffers);
971
972         while (c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY] >
973                limit_buffers) {
974
975                 struct dm_buffer *b = __get_unclaimed_buffer(c);
976
977                 if (!b)
978                         return;
979
980                 __free_buffer_wake(b);
981                 cond_resched();
982         }
983
984         if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
985                 __write_dirty_buffers_async(c, 1, write_list);
986 }
987
988 /*----------------------------------------------------------------
989  * Getting a buffer
990  *--------------------------------------------------------------*/
991
992 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block,
993                                      enum new_flag nf, int *need_submit,
994                                      struct list_head *write_list)
995 {
996         struct dm_buffer *b, *new_b = NULL;
997
998         *need_submit = 0;
999
1000         b = __find(c, block);
1001         if (b)
1002                 goto found_buffer;
1003
1004         if (nf == NF_GET)
1005                 return NULL;
1006
1007         new_b = __alloc_buffer_wait(c, nf);
1008         if (!new_b)
1009                 return NULL;
1010
1011         /*
1012          * We've had a period where the mutex was unlocked, so need to
1013          * recheck the hash table.
1014          */
1015         b = __find(c, block);
1016         if (b) {
1017                 __free_buffer_wake(new_b);
1018                 goto found_buffer;
1019         }
1020
1021         __check_watermark(c, write_list);
1022
1023         b = new_b;
1024         b->hold_count = 1;
1025         b->read_error = 0;
1026         b->write_error = 0;
1027         __link_buffer(b, block, LIST_CLEAN);
1028
1029         if (nf == NF_FRESH) {
1030                 b->state = 0;
1031                 return b;
1032         }
1033
1034         b->state = 1 << B_READING;
1035         *need_submit = 1;
1036
1037         return b;
1038
1039 found_buffer:
1040         if (nf == NF_PREFETCH)
1041                 return NULL;
1042         /*
1043          * Note: it is essential that we don't wait for the buffer to be
1044          * read if dm_bufio_get function is used. Both dm_bufio_get and
1045          * dm_bufio_prefetch can be used in the driver request routine.
1046          * If the user called both dm_bufio_prefetch and dm_bufio_get on
1047          * the same buffer, it would deadlock if we waited.
1048          */
1049         if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
1050                 return NULL;
1051
1052         b->hold_count++;
1053         __relink_lru(b, test_bit(B_DIRTY, &b->state) ||
1054                      test_bit(B_WRITING, &b->state));
1055         return b;
1056 }
1057
1058 /*
1059  * The endio routine for reading: set the error, clear the bit and wake up
1060  * anyone waiting on the buffer.
1061  */
1062 static void read_endio(struct bio *bio)
1063 {
1064         struct dm_buffer *b = container_of(bio, struct dm_buffer, bio);
1065
1066         b->read_error = bio->bi_error;
1067
1068         BUG_ON(!test_bit(B_READING, &b->state));
1069
1070         smp_mb__before_atomic();
1071         clear_bit(B_READING, &b->state);
1072         smp_mb__after_atomic();
1073
1074         wake_up_bit(&b->state, B_READING);
1075 }
1076
1077 /*
1078  * A common routine for dm_bufio_new and dm_bufio_read.  Operation of these
1079  * functions is similar except that dm_bufio_new doesn't read the
1080  * buffer from the disk (assuming that the caller overwrites all the data
1081  * and uses dm_bufio_mark_buffer_dirty to write new data back).
1082  */
1083 static void *new_read(struct dm_bufio_client *c, sector_t block,
1084                       enum new_flag nf, struct dm_buffer **bp)
1085 {
1086         int need_submit;
1087         struct dm_buffer *b;
1088
1089         LIST_HEAD(write_list);
1090
1091         dm_bufio_lock(c);
1092         b = __bufio_new(c, block, nf, &need_submit, &write_list);
1093 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1094         if (b && b->hold_count == 1)
1095                 buffer_record_stack(b);
1096 #endif
1097         dm_bufio_unlock(c);
1098
1099         __flush_write_list(&write_list);
1100
1101         if (!b)
1102                 return NULL;
1103
1104         if (need_submit)
1105                 submit_io(b, READ, read_endio);
1106
1107         wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
1108
1109         if (b->read_error) {
1110                 int error = b->read_error;
1111
1112                 dm_bufio_release(b);
1113
1114                 return ERR_PTR(error);
1115         }
1116
1117         *bp = b;
1118
1119         return b->data;
1120 }
1121
1122 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
1123                    struct dm_buffer **bp)
1124 {
1125         return new_read(c, block, NF_GET, bp);
1126 }
1127 EXPORT_SYMBOL_GPL(dm_bufio_get);
1128
1129 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
1130                     struct dm_buffer **bp)
1131 {
1132         BUG_ON(dm_bufio_in_request());
1133
1134         return new_read(c, block, NF_READ, bp);
1135 }
1136 EXPORT_SYMBOL_GPL(dm_bufio_read);
1137
1138 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
1139                    struct dm_buffer **bp)
1140 {
1141         BUG_ON(dm_bufio_in_request());
1142
1143         return new_read(c, block, NF_FRESH, bp);
1144 }
1145 EXPORT_SYMBOL_GPL(dm_bufio_new);
1146
1147 void dm_bufio_prefetch(struct dm_bufio_client *c,
1148                        sector_t block, unsigned n_blocks)
1149 {
1150         struct blk_plug plug;
1151
1152         LIST_HEAD(write_list);
1153
1154         BUG_ON(dm_bufio_in_request());
1155
1156         blk_start_plug(&plug);
1157         dm_bufio_lock(c);
1158
1159         for (; n_blocks--; block++) {
1160                 int need_submit;
1161                 struct dm_buffer *b;
1162                 b = __bufio_new(c, block, NF_PREFETCH, &need_submit,
1163                                 &write_list);
1164                 if (unlikely(!list_empty(&write_list))) {
1165                         dm_bufio_unlock(c);
1166                         blk_finish_plug(&plug);
1167                         __flush_write_list(&write_list);
1168                         blk_start_plug(&plug);
1169                         dm_bufio_lock(c);
1170                 }
1171                 if (unlikely(b != NULL)) {
1172                         dm_bufio_unlock(c);
1173
1174                         if (need_submit)
1175                                 submit_io(b, READ, read_endio);
1176                         dm_bufio_release(b);
1177
1178                         cond_resched();
1179
1180                         if (!n_blocks)
1181                                 goto flush_plug;
1182                         dm_bufio_lock(c);
1183                 }
1184         }
1185
1186         dm_bufio_unlock(c);
1187
1188 flush_plug:
1189         blk_finish_plug(&plug);
1190 }
1191 EXPORT_SYMBOL_GPL(dm_bufio_prefetch);
1192
1193 void dm_bufio_release(struct dm_buffer *b)
1194 {
1195         struct dm_bufio_client *c = b->c;
1196
1197         dm_bufio_lock(c);
1198
1199         BUG_ON(!b->hold_count);
1200
1201         b->hold_count--;
1202         if (!b->hold_count) {
1203                 wake_up(&c->free_buffer_wait);
1204
1205                 /*
1206                  * If there were errors on the buffer, and the buffer is not
1207                  * to be written, free the buffer. There is no point in caching
1208                  * invalid buffer.
1209                  */
1210                 if ((b->read_error || b->write_error) &&
1211                     !test_bit(B_READING, &b->state) &&
1212                     !test_bit(B_WRITING, &b->state) &&
1213                     !test_bit(B_DIRTY, &b->state)) {
1214                         __unlink_buffer(b);
1215                         __free_buffer_wake(b);
1216                 }
1217         }
1218
1219         dm_bufio_unlock(c);
1220 }
1221 EXPORT_SYMBOL_GPL(dm_bufio_release);
1222
1223 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b)
1224 {
1225         struct dm_bufio_client *c = b->c;
1226
1227         dm_bufio_lock(c);
1228
1229         BUG_ON(test_bit(B_READING, &b->state));
1230
1231         if (!test_and_set_bit(B_DIRTY, &b->state))
1232                 __relink_lru(b, LIST_DIRTY);
1233
1234         dm_bufio_unlock(c);
1235 }
1236 EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty);
1237
1238 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c)
1239 {
1240         LIST_HEAD(write_list);
1241
1242         BUG_ON(dm_bufio_in_request());
1243
1244         dm_bufio_lock(c);
1245         __write_dirty_buffers_async(c, 0, &write_list);
1246         dm_bufio_unlock(c);
1247         __flush_write_list(&write_list);
1248 }
1249 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async);
1250
1251 /*
1252  * For performance, it is essential that the buffers are written asynchronously
1253  * and simultaneously (so that the block layer can merge the writes) and then
1254  * waited upon.
1255  *
1256  * Finally, we flush hardware disk cache.
1257  */
1258 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c)
1259 {
1260         int a, f;
1261         unsigned long buffers_processed = 0;
1262         struct dm_buffer *b, *tmp;
1263
1264         LIST_HEAD(write_list);
1265
1266         dm_bufio_lock(c);
1267         __write_dirty_buffers_async(c, 0, &write_list);
1268         dm_bufio_unlock(c);
1269         __flush_write_list(&write_list);
1270         dm_bufio_lock(c);
1271
1272 again:
1273         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) {
1274                 int dropped_lock = 0;
1275
1276                 if (buffers_processed < c->n_buffers[LIST_DIRTY])
1277                         buffers_processed++;
1278
1279                 BUG_ON(test_bit(B_READING, &b->state));
1280
1281                 if (test_bit(B_WRITING, &b->state)) {
1282                         if (buffers_processed < c->n_buffers[LIST_DIRTY]) {
1283                                 dropped_lock = 1;
1284                                 b->hold_count++;
1285                                 dm_bufio_unlock(c);
1286                                 wait_on_bit_io(&b->state, B_WRITING,
1287                                                TASK_UNINTERRUPTIBLE);
1288                                 dm_bufio_lock(c);
1289                                 b->hold_count--;
1290                         } else
1291                                 wait_on_bit_io(&b->state, B_WRITING,
1292                                                TASK_UNINTERRUPTIBLE);
1293                 }
1294
1295                 if (!test_bit(B_DIRTY, &b->state) &&
1296                     !test_bit(B_WRITING, &b->state))
1297                         __relink_lru(b, LIST_CLEAN);
1298
1299                 cond_resched();
1300
1301                 /*
1302                  * If we dropped the lock, the list is no longer consistent,
1303                  * so we must restart the search.
1304                  *
1305                  * In the most common case, the buffer just processed is
1306                  * relinked to the clean list, so we won't loop scanning the
1307                  * same buffer again and again.
1308                  *
1309                  * This may livelock if there is another thread simultaneously
1310                  * dirtying buffers, so we count the number of buffers walked
1311                  * and if it exceeds the total number of buffers, it means that
1312                  * someone is doing some writes simultaneously with us.  In
1313                  * this case, stop, dropping the lock.
1314                  */
1315                 if (dropped_lock)
1316                         goto again;
1317         }
1318         wake_up(&c->free_buffer_wait);
1319         dm_bufio_unlock(c);
1320
1321         a = xchg(&c->async_write_error, 0);
1322         f = dm_bufio_issue_flush(c);
1323         if (a)
1324                 return a;
1325
1326         return f;
1327 }
1328 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers);
1329
1330 /*
1331  * Use dm-io to send and empty barrier flush the device.
1332  */
1333 int dm_bufio_issue_flush(struct dm_bufio_client *c)
1334 {
1335         struct dm_io_request io_req = {
1336                 .bi_op = REQ_OP_WRITE,
1337                 .bi_op_flags = REQ_PREFLUSH | REQ_SYNC,
1338                 .mem.type = DM_IO_KMEM,
1339                 .mem.ptr.addr = NULL,
1340                 .client = c->dm_io,
1341         };
1342         struct dm_io_region io_reg = {
1343                 .bdev = c->bdev,
1344                 .sector = 0,
1345                 .count = 0,
1346         };
1347
1348         BUG_ON(dm_bufio_in_request());
1349
1350         return dm_io(&io_req, 1, &io_reg, NULL);
1351 }
1352 EXPORT_SYMBOL_GPL(dm_bufio_issue_flush);
1353
1354 /*
1355  * We first delete any other buffer that may be at that new location.
1356  *
1357  * Then, we write the buffer to the original location if it was dirty.
1358  *
1359  * Then, if we are the only one who is holding the buffer, relink the buffer
1360  * in the hash queue for the new location.
1361  *
1362  * If there was someone else holding the buffer, we write it to the new
1363  * location but not relink it, because that other user needs to have the buffer
1364  * at the same place.
1365  */
1366 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block)
1367 {
1368         struct dm_bufio_client *c = b->c;
1369         struct dm_buffer *new;
1370
1371         BUG_ON(dm_bufio_in_request());
1372
1373         dm_bufio_lock(c);
1374
1375 retry:
1376         new = __find(c, new_block);
1377         if (new) {
1378                 if (new->hold_count) {
1379                         __wait_for_free_buffer(c);
1380                         goto retry;
1381                 }
1382
1383                 /*
1384                  * FIXME: Is there any point waiting for a write that's going
1385                  * to be overwritten in a bit?
1386                  */
1387                 __make_buffer_clean(new);
1388                 __unlink_buffer(new);
1389                 __free_buffer_wake(new);
1390         }
1391
1392         BUG_ON(!b->hold_count);
1393         BUG_ON(test_bit(B_READING, &b->state));
1394
1395         __write_dirty_buffer(b, NULL);
1396         if (b->hold_count == 1) {
1397                 wait_on_bit_io(&b->state, B_WRITING,
1398                                TASK_UNINTERRUPTIBLE);
1399                 set_bit(B_DIRTY, &b->state);
1400                 __unlink_buffer(b);
1401                 __link_buffer(b, new_block, LIST_DIRTY);
1402         } else {
1403                 sector_t old_block;
1404                 wait_on_bit_lock_io(&b->state, B_WRITING,
1405                                     TASK_UNINTERRUPTIBLE);
1406                 /*
1407                  * Relink buffer to "new_block" so that write_callback
1408                  * sees "new_block" as a block number.
1409                  * After the write, link the buffer back to old_block.
1410                  * All this must be done in bufio lock, so that block number
1411                  * change isn't visible to other threads.
1412                  */
1413                 old_block = b->block;
1414                 __unlink_buffer(b);
1415                 __link_buffer(b, new_block, b->list_mode);
1416                 submit_io(b, WRITE, write_endio);
1417                 wait_on_bit_io(&b->state, B_WRITING,
1418                                TASK_UNINTERRUPTIBLE);
1419                 __unlink_buffer(b);
1420                 __link_buffer(b, old_block, b->list_mode);
1421         }
1422
1423         dm_bufio_unlock(c);
1424         dm_bufio_release(b);
1425 }
1426 EXPORT_SYMBOL_GPL(dm_bufio_release_move);
1427
1428 /*
1429  * Free the given buffer.
1430  *
1431  * This is just a hint, if the buffer is in use or dirty, this function
1432  * does nothing.
1433  */
1434 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
1435 {
1436         struct dm_buffer *b;
1437
1438         dm_bufio_lock(c);
1439
1440         b = __find(c, block);
1441         if (b && likely(!b->hold_count) && likely(!b->state)) {
1442                 __unlink_buffer(b);
1443                 __free_buffer_wake(b);
1444         }
1445
1446         dm_bufio_unlock(c);
1447 }
1448 EXPORT_SYMBOL(dm_bufio_forget);
1449
1450 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
1451 {
1452         c->minimum_buffers = n;
1453 }
1454 EXPORT_SYMBOL(dm_bufio_set_minimum_buffers);
1455
1456 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
1457 {
1458         return c->block_size;
1459 }
1460 EXPORT_SYMBOL_GPL(dm_bufio_get_block_size);
1461
1462 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c)
1463 {
1464         return i_size_read(c->bdev->bd_inode) >>
1465                            (SECTOR_SHIFT + c->sectors_per_block_bits);
1466 }
1467 EXPORT_SYMBOL_GPL(dm_bufio_get_device_size);
1468
1469 sector_t dm_bufio_get_block_number(struct dm_buffer *b)
1470 {
1471         return b->block;
1472 }
1473 EXPORT_SYMBOL_GPL(dm_bufio_get_block_number);
1474
1475 void *dm_bufio_get_block_data(struct dm_buffer *b)
1476 {
1477         return b->data;
1478 }
1479 EXPORT_SYMBOL_GPL(dm_bufio_get_block_data);
1480
1481 void *dm_bufio_get_aux_data(struct dm_buffer *b)
1482 {
1483         return b + 1;
1484 }
1485 EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data);
1486
1487 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b)
1488 {
1489         return b->c;
1490 }
1491 EXPORT_SYMBOL_GPL(dm_bufio_get_client);
1492
1493 static void drop_buffers(struct dm_bufio_client *c)
1494 {
1495         struct dm_buffer *b;
1496         int i;
1497         bool warned = false;
1498
1499         BUG_ON(dm_bufio_in_request());
1500
1501         /*
1502          * An optimization so that the buffers are not written one-by-one.
1503          */
1504         dm_bufio_write_dirty_buffers_async(c);
1505
1506         dm_bufio_lock(c);
1507
1508         while ((b = __get_unclaimed_buffer(c)))
1509                 __free_buffer_wake(b);
1510
1511         for (i = 0; i < LIST_SIZE; i++)
1512                 list_for_each_entry(b, &c->lru[i], lru_list) {
1513                         WARN_ON(!warned);
1514                         warned = true;
1515                         DMERR("leaked buffer %llx, hold count %u, list %d",
1516                               (unsigned long long)b->block, b->hold_count, i);
1517 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1518                         print_stack_trace(&b->stack_trace, 1);
1519                         b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
1520 #endif
1521                 }
1522
1523 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
1524         while ((b = __get_unclaimed_buffer(c)))
1525                 __free_buffer_wake(b);
1526 #endif
1527
1528         for (i = 0; i < LIST_SIZE; i++)
1529                 BUG_ON(!list_empty(&c->lru[i]));
1530
1531         dm_bufio_unlock(c);
1532 }
1533
1534 /*
1535  * We may not be able to evict this buffer if IO pending or the client
1536  * is still using it.  Caller is expected to know buffer is too old.
1537  *
1538  * And if GFP_NOFS is used, we must not do any I/O because we hold
1539  * dm_bufio_clients_lock and we would risk deadlock if the I/O gets
1540  * rerouted to different bufio client.
1541  */
1542 static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
1543 {
1544         if (!(gfp & __GFP_FS)) {
1545                 if (test_bit(B_READING, &b->state) ||
1546                     test_bit(B_WRITING, &b->state) ||
1547                     test_bit(B_DIRTY, &b->state))
1548                         return false;
1549         }
1550
1551         if (b->hold_count)
1552                 return false;
1553
1554         __make_buffer_clean(b);
1555         __unlink_buffer(b);
1556         __free_buffer_wake(b);
1557
1558         return true;
1559 }
1560
1561 static unsigned long get_retain_buffers(struct dm_bufio_client *c)
1562 {
1563         unsigned long retain_bytes = ACCESS_ONCE(dm_bufio_retain_bytes);
1564         return retain_bytes >> (c->sectors_per_block_bits + SECTOR_SHIFT);
1565 }
1566
1567 static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan,
1568                             gfp_t gfp_mask)
1569 {
1570         int l;
1571         struct dm_buffer *b, *tmp;
1572         unsigned long freed = 0;
1573         unsigned long count = nr_to_scan;
1574         unsigned long retain_target = get_retain_buffers(c);
1575
1576         for (l = 0; l < LIST_SIZE; l++) {
1577                 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) {
1578                         if (__try_evict_buffer(b, gfp_mask))
1579                                 freed++;
1580                         if (!--nr_to_scan || ((count - freed) <= retain_target))
1581                                 return freed;
1582                         cond_resched();
1583                 }
1584         }
1585         return freed;
1586 }
1587
1588 static unsigned long
1589 dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
1590 {
1591         struct dm_bufio_client *c;
1592         unsigned long freed;
1593
1594         c = container_of(shrink, struct dm_bufio_client, shrinker);
1595         if (sc->gfp_mask & __GFP_FS)
1596                 dm_bufio_lock(c);
1597         else if (!dm_bufio_trylock(c))
1598                 return SHRINK_STOP;
1599
1600         freed  = __scan(c, sc->nr_to_scan, sc->gfp_mask);
1601         dm_bufio_unlock(c);
1602         return freed;
1603 }
1604
1605 static unsigned long
1606 dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
1607 {
1608         struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker);
1609
1610         return ACCESS_ONCE(c->n_buffers[LIST_CLEAN]) + ACCESS_ONCE(c->n_buffers[LIST_DIRTY]);
1611 }
1612
1613 /*
1614  * Create the buffering interface
1615  */
1616 struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
1617                                                unsigned reserved_buffers, unsigned aux_size,
1618                                                void (*alloc_callback)(struct dm_buffer *),
1619                                                void (*write_callback)(struct dm_buffer *))
1620 {
1621         int r;
1622         struct dm_bufio_client *c;
1623         unsigned i;
1624
1625         BUG_ON(block_size < 1 << SECTOR_SHIFT ||
1626                (block_size & (block_size - 1)));
1627
1628         c = kzalloc(sizeof(*c), GFP_KERNEL);
1629         if (!c) {
1630                 r = -ENOMEM;
1631                 goto bad_client;
1632         }
1633         c->buffer_tree = RB_ROOT;
1634
1635         c->bdev = bdev;
1636         c->block_size = block_size;
1637         c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT;
1638         c->pages_per_block_bits = (__ffs(block_size) >= PAGE_SHIFT) ?
1639                                   __ffs(block_size) - PAGE_SHIFT : 0;
1640         c->blocks_per_page_bits = (__ffs(block_size) < PAGE_SHIFT ?
1641                                   PAGE_SHIFT - __ffs(block_size) : 0);
1642
1643         c->aux_size = aux_size;
1644         c->alloc_callback = alloc_callback;
1645         c->write_callback = write_callback;
1646
1647         for (i = 0; i < LIST_SIZE; i++) {
1648                 INIT_LIST_HEAD(&c->lru[i]);
1649                 c->n_buffers[i] = 0;
1650         }
1651
1652         mutex_init(&c->lock);
1653         INIT_LIST_HEAD(&c->reserved_buffers);
1654         c->need_reserved_buffers = reserved_buffers;
1655
1656         c->minimum_buffers = DM_BUFIO_MIN_BUFFERS;
1657
1658         init_waitqueue_head(&c->free_buffer_wait);
1659         c->async_write_error = 0;
1660
1661         c->dm_io = dm_io_client_create();
1662         if (IS_ERR(c->dm_io)) {
1663                 r = PTR_ERR(c->dm_io);
1664                 goto bad_dm_io;
1665         }
1666
1667         mutex_lock(&dm_bufio_clients_lock);
1668         if (c->blocks_per_page_bits) {
1669                 if (!DM_BUFIO_CACHE_NAME(c)) {
1670                         DM_BUFIO_CACHE_NAME(c) = kasprintf(GFP_KERNEL, "dm_bufio_cache-%u", c->block_size);
1671                         if (!DM_BUFIO_CACHE_NAME(c)) {
1672                                 r = -ENOMEM;
1673                                 mutex_unlock(&dm_bufio_clients_lock);
1674                                 goto bad_cache;
1675                         }
1676                 }
1677
1678                 if (!DM_BUFIO_CACHE(c)) {
1679                         DM_BUFIO_CACHE(c) = kmem_cache_create(DM_BUFIO_CACHE_NAME(c),
1680                                                               c->block_size,
1681                                                               c->block_size, 0, NULL);
1682                         if (!DM_BUFIO_CACHE(c)) {
1683                                 r = -ENOMEM;
1684                                 mutex_unlock(&dm_bufio_clients_lock);
1685                                 goto bad_cache;
1686                         }
1687                 }
1688         }
1689         mutex_unlock(&dm_bufio_clients_lock);
1690
1691         while (c->need_reserved_buffers) {
1692                 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL);
1693
1694                 if (!b) {
1695                         r = -ENOMEM;
1696                         goto bad_buffer;
1697                 }
1698                 __free_buffer_wake(b);
1699         }
1700
1701         mutex_lock(&dm_bufio_clients_lock);
1702         dm_bufio_client_count++;
1703         list_add(&c->client_list, &dm_bufio_all_clients);
1704         __cache_size_refresh();
1705         mutex_unlock(&dm_bufio_clients_lock);
1706
1707         c->shrinker.count_objects = dm_bufio_shrink_count;
1708         c->shrinker.scan_objects = dm_bufio_shrink_scan;
1709         c->shrinker.seeks = 1;
1710         c->shrinker.batch = 0;
1711         register_shrinker(&c->shrinker);
1712
1713         return c;
1714
1715 bad_buffer:
1716 bad_cache:
1717         while (!list_empty(&c->reserved_buffers)) {
1718                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1719                                                  struct dm_buffer, lru_list);
1720                 list_del(&b->lru_list);
1721                 free_buffer(b);
1722         }
1723         dm_io_client_destroy(c->dm_io);
1724 bad_dm_io:
1725         kfree(c);
1726 bad_client:
1727         return ERR_PTR(r);
1728 }
1729 EXPORT_SYMBOL_GPL(dm_bufio_client_create);
1730
1731 /*
1732  * Free the buffering interface.
1733  * It is required that there are no references on any buffers.
1734  */
1735 void dm_bufio_client_destroy(struct dm_bufio_client *c)
1736 {
1737         unsigned i;
1738
1739         drop_buffers(c);
1740
1741         unregister_shrinker(&c->shrinker);
1742
1743         mutex_lock(&dm_bufio_clients_lock);
1744
1745         list_del(&c->client_list);
1746         dm_bufio_client_count--;
1747         __cache_size_refresh();
1748
1749         mutex_unlock(&dm_bufio_clients_lock);
1750
1751         BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree));
1752         BUG_ON(c->need_reserved_buffers);
1753
1754         while (!list_empty(&c->reserved_buffers)) {
1755                 struct dm_buffer *b = list_entry(c->reserved_buffers.next,
1756                                                  struct dm_buffer, lru_list);
1757                 list_del(&b->lru_list);
1758                 free_buffer(b);
1759         }
1760
1761         for (i = 0; i < LIST_SIZE; i++)
1762                 if (c->n_buffers[i])
1763                         DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]);
1764
1765         for (i = 0; i < LIST_SIZE; i++)
1766                 BUG_ON(c->n_buffers[i]);
1767
1768         dm_io_client_destroy(c->dm_io);
1769         kfree(c);
1770 }
1771 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy);
1772
1773 void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start)
1774 {
1775         c->start = start;
1776 }
1777 EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset);
1778
1779 static unsigned get_max_age_hz(void)
1780 {
1781         unsigned max_age = ACCESS_ONCE(dm_bufio_max_age);
1782
1783         if (max_age > UINT_MAX / HZ)
1784                 max_age = UINT_MAX / HZ;
1785
1786         return max_age * HZ;
1787 }
1788
1789 static bool older_than(struct dm_buffer *b, unsigned long age_hz)
1790 {
1791         return time_after_eq(jiffies, b->last_accessed + age_hz);
1792 }
1793
1794 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz)
1795 {
1796         struct dm_buffer *b, *tmp;
1797         unsigned long retain_target = get_retain_buffers(c);
1798         unsigned long count;
1799         LIST_HEAD(write_list);
1800
1801         dm_bufio_lock(c);
1802
1803         __check_watermark(c, &write_list);
1804         if (unlikely(!list_empty(&write_list))) {
1805                 dm_bufio_unlock(c);
1806                 __flush_write_list(&write_list);
1807                 dm_bufio_lock(c);
1808         }
1809
1810         count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY];
1811         list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) {
1812                 if (count <= retain_target)
1813                         break;
1814
1815                 if (!older_than(b, age_hz))
1816                         break;
1817
1818                 if (__try_evict_buffer(b, 0))
1819                         count--;
1820
1821                 cond_resched();
1822         }
1823
1824         dm_bufio_unlock(c);
1825 }
1826
1827 static void cleanup_old_buffers(void)
1828 {
1829         unsigned long max_age_hz = get_max_age_hz();
1830         struct dm_bufio_client *c;
1831
1832         mutex_lock(&dm_bufio_clients_lock);
1833
1834         __cache_size_refresh();
1835
1836         list_for_each_entry(c, &dm_bufio_all_clients, client_list)
1837                 __evict_old_buffers(c, max_age_hz);
1838
1839         mutex_unlock(&dm_bufio_clients_lock);
1840 }
1841
1842 static struct workqueue_struct *dm_bufio_wq;
1843 static struct delayed_work dm_bufio_work;
1844
1845 static void work_fn(struct work_struct *w)
1846 {
1847         cleanup_old_buffers();
1848
1849         queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1850                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1851 }
1852
1853 /*----------------------------------------------------------------
1854  * Module setup
1855  *--------------------------------------------------------------*/
1856
1857 /*
1858  * This is called only once for the whole dm_bufio module.
1859  * It initializes memory limit.
1860  */
1861 static int __init dm_bufio_init(void)
1862 {
1863         __u64 mem;
1864
1865         dm_bufio_allocated_kmem_cache = 0;
1866         dm_bufio_allocated_get_free_pages = 0;
1867         dm_bufio_allocated_vmalloc = 0;
1868         dm_bufio_current_allocated = 0;
1869
1870         memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches);
1871         memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names);
1872
1873         mem = (__u64)((totalram_pages - totalhigh_pages) *
1874                       DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT;
1875
1876         if (mem > ULONG_MAX)
1877                 mem = ULONG_MAX;
1878
1879 #ifdef CONFIG_MMU
1880         /*
1881          * Get the size of vmalloc space the same way as VMALLOC_TOTAL
1882          * in fs/proc/internal.h
1883          */
1884         if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100)
1885                 mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100;
1886 #endif
1887
1888         dm_bufio_default_cache_size = mem;
1889
1890         mutex_lock(&dm_bufio_clients_lock);
1891         __cache_size_refresh();
1892         mutex_unlock(&dm_bufio_clients_lock);
1893
1894         dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0);
1895         if (!dm_bufio_wq)
1896                 return -ENOMEM;
1897
1898         INIT_DELAYED_WORK(&dm_bufio_work, work_fn);
1899         queue_delayed_work(dm_bufio_wq, &dm_bufio_work,
1900                            DM_BUFIO_WORK_TIMER_SECS * HZ);
1901
1902         return 0;
1903 }
1904
1905 /*
1906  * This is called once when unloading the dm_bufio module.
1907  */
1908 static void __exit dm_bufio_exit(void)
1909 {
1910         int bug = 0;
1911         int i;
1912
1913         cancel_delayed_work_sync(&dm_bufio_work);
1914         destroy_workqueue(dm_bufio_wq);
1915
1916         for (i = 0; i < ARRAY_SIZE(dm_bufio_caches); i++)
1917                 kmem_cache_destroy(dm_bufio_caches[i]);
1918
1919         for (i = 0; i < ARRAY_SIZE(dm_bufio_cache_names); i++)
1920                 kfree(dm_bufio_cache_names[i]);
1921
1922         if (dm_bufio_client_count) {
1923                 DMCRIT("%s: dm_bufio_client_count leaked: %d",
1924                         __func__, dm_bufio_client_count);
1925                 bug = 1;
1926         }
1927
1928         if (dm_bufio_current_allocated) {
1929                 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu",
1930                         __func__, dm_bufio_current_allocated);
1931                 bug = 1;
1932         }
1933
1934         if (dm_bufio_allocated_get_free_pages) {
1935                 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu",
1936                        __func__, dm_bufio_allocated_get_free_pages);
1937                 bug = 1;
1938         }
1939
1940         if (dm_bufio_allocated_vmalloc) {
1941                 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu",
1942                        __func__, dm_bufio_allocated_vmalloc);
1943                 bug = 1;
1944         }
1945
1946         BUG_ON(bug);
1947 }
1948
1949 module_init(dm_bufio_init)
1950 module_exit(dm_bufio_exit)
1951
1952 module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR);
1953 MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache");
1954
1955 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR);
1956 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds");
1957
1958 module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR);
1959 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory");
1960
1961 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR);
1962 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory");
1963
1964 module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO);
1965 MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc");
1966
1967 module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO);
1968 MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
1969
1970 module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO);
1971 MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc");
1972
1973 module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO);
1974 MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache");
1975
1976 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>");
1977 MODULE_DESCRIPTION(DM_NAME " buffered I/O library");
1978 MODULE_LICENSE("GPL");