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 <linux/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_RATIO 3 37 #define DM_BUFIO_LOW_WATERMARK_RATIO 16 38 39 /* 40 * Check buffer ages in this interval (seconds) 41 */ 42 #define DM_BUFIO_WORK_TIMER_SECS 30 43 44 /* 45 * Free buffers when they are older than this (seconds) 46 */ 47 #define DM_BUFIO_DEFAULT_AGE_SECS 300 48 49 /* 50 * The nr of bytes of cached data to keep around. 51 */ 52 #define DM_BUFIO_DEFAULT_RETAIN_BYTES (256 * 1024) 53 54 /* 55 * Align buffer writes to this boundary. 56 * Tests show that SSDs have the highest IOPS when using 4k writes. 57 */ 58 #define DM_BUFIO_WRITE_ALIGN 4096 59 60 /* 61 * dm_buffer->list_mode 62 */ 63 #define LIST_CLEAN 0 64 #define LIST_DIRTY 1 65 #define LIST_SIZE 2 66 67 /* 68 * Linking of buffers: 69 * All buffers are linked to buffer_tree with their node field. 70 * 71 * Clean buffers that are not being written (B_WRITING not set) 72 * are linked to lru[LIST_CLEAN] with their lru_list field. 73 * 74 * Dirty and clean buffers that are being written are linked to 75 * lru[LIST_DIRTY] with their lru_list field. When the write 76 * finishes, the buffer cannot be relinked immediately (because we 77 * are in an interrupt context and relinking requires process 78 * context), so some clean-not-writing buffers can be held on 79 * dirty_lru too. They are later added to lru in the process 80 * context. 81 */ 82 struct dm_bufio_client { 83 struct mutex lock; 84 85 struct list_head lru[LIST_SIZE]; 86 unsigned long n_buffers[LIST_SIZE]; 87 88 struct block_device *bdev; 89 unsigned block_size; 90 s8 sectors_per_block_bits; 91 void (*alloc_callback)(struct dm_buffer *); 92 void (*write_callback)(struct dm_buffer *); 93 94 struct kmem_cache *slab_buffer; 95 struct kmem_cache *slab_cache; 96 struct dm_io_client *dm_io; 97 98 struct list_head reserved_buffers; 99 unsigned need_reserved_buffers; 100 101 unsigned minimum_buffers; 102 103 struct rb_root buffer_tree; 104 wait_queue_head_t free_buffer_wait; 105 106 sector_t start; 107 108 int async_write_error; 109 110 struct list_head client_list; 111 struct shrinker shrinker; 112 }; 113 114 /* 115 * Buffer state bits. 116 */ 117 #define B_READING 0 118 #define B_WRITING 1 119 #define B_DIRTY 2 120 121 /* 122 * Describes how the block was allocated: 123 * kmem_cache_alloc(), __get_free_pages() or vmalloc(). 124 * See the comment at alloc_buffer_data. 125 */ 126 enum data_mode { 127 DATA_MODE_SLAB = 0, 128 DATA_MODE_GET_FREE_PAGES = 1, 129 DATA_MODE_VMALLOC = 2, 130 DATA_MODE_LIMIT = 3 131 }; 132 133 struct dm_buffer { 134 struct rb_node node; 135 struct list_head lru_list; 136 struct list_head global_list; 137 sector_t block; 138 void *data; 139 unsigned char data_mode; /* DATA_MODE_* */ 140 unsigned char list_mode; /* LIST_* */ 141 blk_status_t read_error; 142 blk_status_t write_error; 143 unsigned accessed; 144 unsigned hold_count; 145 unsigned long state; 146 unsigned long last_accessed; 147 unsigned dirty_start; 148 unsigned dirty_end; 149 unsigned write_start; 150 unsigned write_end; 151 struct dm_bufio_client *c; 152 struct list_head write_list; 153 void (*end_io)(struct dm_buffer *, blk_status_t); 154 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 155 #define MAX_STACK 10 156 unsigned int stack_len; 157 unsigned long stack_entries[MAX_STACK]; 158 #endif 159 }; 160 161 /*----------------------------------------------------------------*/ 162 163 #define dm_bufio_in_request() (!!current->bio_list) 164 165 static void dm_bufio_lock(struct dm_bufio_client *c) 166 { 167 mutex_lock_nested(&c->lock, dm_bufio_in_request()); 168 } 169 170 static int dm_bufio_trylock(struct dm_bufio_client *c) 171 { 172 return mutex_trylock(&c->lock); 173 } 174 175 static void dm_bufio_unlock(struct dm_bufio_client *c) 176 { 177 mutex_unlock(&c->lock); 178 } 179 180 /*----------------------------------------------------------------*/ 181 182 /* 183 * Default cache size: available memory divided by the ratio. 184 */ 185 static unsigned long dm_bufio_default_cache_size; 186 187 /* 188 * Total cache size set by the user. 189 */ 190 static unsigned long dm_bufio_cache_size; 191 192 /* 193 * A copy of dm_bufio_cache_size because dm_bufio_cache_size can change 194 * at any time. If it disagrees, the user has changed cache size. 195 */ 196 static unsigned long dm_bufio_cache_size_latch; 197 198 static DEFINE_SPINLOCK(global_spinlock); 199 200 static LIST_HEAD(global_queue); 201 202 static unsigned long global_num = 0; 203 204 /* 205 * Buffers are freed after this timeout 206 */ 207 static unsigned dm_bufio_max_age = DM_BUFIO_DEFAULT_AGE_SECS; 208 static unsigned long dm_bufio_retain_bytes = DM_BUFIO_DEFAULT_RETAIN_BYTES; 209 210 static unsigned long dm_bufio_peak_allocated; 211 static unsigned long dm_bufio_allocated_kmem_cache; 212 static unsigned long dm_bufio_allocated_get_free_pages; 213 static unsigned long dm_bufio_allocated_vmalloc; 214 static unsigned long dm_bufio_current_allocated; 215 216 /*----------------------------------------------------------------*/ 217 218 /* 219 * The current number of clients. 220 */ 221 static int dm_bufio_client_count; 222 223 /* 224 * The list of all clients. 225 */ 226 static LIST_HEAD(dm_bufio_all_clients); 227 228 /* 229 * This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count 230 */ 231 static DEFINE_MUTEX(dm_bufio_clients_lock); 232 233 static struct workqueue_struct *dm_bufio_wq; 234 static struct delayed_work dm_bufio_cleanup_old_work; 235 static struct work_struct dm_bufio_replacement_work; 236 237 238 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 239 static void buffer_record_stack(struct dm_buffer *b) 240 { 241 b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2); 242 } 243 #endif 244 245 /*---------------------------------------------------------------- 246 * A red/black tree acts as an index for all the buffers. 247 *--------------------------------------------------------------*/ 248 static struct dm_buffer *__find(struct dm_bufio_client *c, sector_t block) 249 { 250 struct rb_node *n = c->buffer_tree.rb_node; 251 struct dm_buffer *b; 252 253 while (n) { 254 b = container_of(n, struct dm_buffer, node); 255 256 if (b->block == block) 257 return b; 258 259 n = (b->block < block) ? n->rb_left : n->rb_right; 260 } 261 262 return NULL; 263 } 264 265 static void __insert(struct dm_bufio_client *c, struct dm_buffer *b) 266 { 267 struct rb_node **new = &c->buffer_tree.rb_node, *parent = NULL; 268 struct dm_buffer *found; 269 270 while (*new) { 271 found = container_of(*new, struct dm_buffer, node); 272 273 if (found->block == b->block) { 274 BUG_ON(found != b); 275 return; 276 } 277 278 parent = *new; 279 new = (found->block < b->block) ? 280 &((*new)->rb_left) : &((*new)->rb_right); 281 } 282 283 rb_link_node(&b->node, parent, new); 284 rb_insert_color(&b->node, &c->buffer_tree); 285 } 286 287 static void __remove(struct dm_bufio_client *c, struct dm_buffer *b) 288 { 289 rb_erase(&b->node, &c->buffer_tree); 290 } 291 292 /*----------------------------------------------------------------*/ 293 294 static void adjust_total_allocated(struct dm_buffer *b, bool unlink) 295 { 296 unsigned char data_mode; 297 long diff; 298 299 static unsigned long * const class_ptr[DATA_MODE_LIMIT] = { 300 &dm_bufio_allocated_kmem_cache, 301 &dm_bufio_allocated_get_free_pages, 302 &dm_bufio_allocated_vmalloc, 303 }; 304 305 data_mode = b->data_mode; 306 diff = (long)b->c->block_size; 307 if (unlink) 308 diff = -diff; 309 310 spin_lock(&global_spinlock); 311 312 *class_ptr[data_mode] += diff; 313 314 dm_bufio_current_allocated += diff; 315 316 if (dm_bufio_current_allocated > dm_bufio_peak_allocated) 317 dm_bufio_peak_allocated = dm_bufio_current_allocated; 318 319 b->accessed = 1; 320 321 if (!unlink) { 322 list_add(&b->global_list, &global_queue); 323 global_num++; 324 if (dm_bufio_current_allocated > dm_bufio_cache_size) 325 queue_work(dm_bufio_wq, &dm_bufio_replacement_work); 326 } else { 327 list_del(&b->global_list); 328 global_num--; 329 } 330 331 spin_unlock(&global_spinlock); 332 } 333 334 /* 335 * Change the number of clients and recalculate per-client limit. 336 */ 337 static void __cache_size_refresh(void) 338 { 339 BUG_ON(!mutex_is_locked(&dm_bufio_clients_lock)); 340 BUG_ON(dm_bufio_client_count < 0); 341 342 dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size); 343 344 /* 345 * Use default if set to 0 and report the actual cache size used. 346 */ 347 if (!dm_bufio_cache_size_latch) { 348 (void)cmpxchg(&dm_bufio_cache_size, 0, 349 dm_bufio_default_cache_size); 350 dm_bufio_cache_size_latch = dm_bufio_default_cache_size; 351 } 352 } 353 354 /* 355 * Allocating buffer data. 356 * 357 * Small buffers are allocated with kmem_cache, to use space optimally. 358 * 359 * For large buffers, we choose between get_free_pages and vmalloc. 360 * Each has advantages and disadvantages. 361 * 362 * __get_free_pages can randomly fail if the memory is fragmented. 363 * __vmalloc won't randomly fail, but vmalloc space is limited (it may be 364 * as low as 128M) so using it for caching is not appropriate. 365 * 366 * If the allocation may fail we use __get_free_pages. Memory fragmentation 367 * won't have a fatal effect here, but it just causes flushes of some other 368 * buffers and more I/O will be performed. Don't use __get_free_pages if it 369 * always fails (i.e. order >= MAX_ORDER). 370 * 371 * If the allocation shouldn't fail we use __vmalloc. This is only for the 372 * initial reserve allocation, so there's no risk of wasting all vmalloc 373 * space. 374 */ 375 static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, 376 unsigned char *data_mode) 377 { 378 if (unlikely(c->slab_cache != NULL)) { 379 *data_mode = DATA_MODE_SLAB; 380 return kmem_cache_alloc(c->slab_cache, gfp_mask); 381 } 382 383 if (c->block_size <= KMALLOC_MAX_SIZE && 384 gfp_mask & __GFP_NORETRY) { 385 *data_mode = DATA_MODE_GET_FREE_PAGES; 386 return (void *)__get_free_pages(gfp_mask, 387 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT)); 388 } 389 390 *data_mode = DATA_MODE_VMALLOC; 391 392 /* 393 * __vmalloc allocates the data pages and auxiliary structures with 394 * gfp_flags that were specified, but pagetables are always allocated 395 * with GFP_KERNEL, no matter what was specified as gfp_mask. 396 * 397 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that 398 * all allocations done by this process (including pagetables) are done 399 * as if GFP_NOIO was specified. 400 */ 401 if (gfp_mask & __GFP_NORETRY) { 402 unsigned noio_flag = memalloc_noio_save(); 403 void *ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); 404 405 memalloc_noio_restore(noio_flag); 406 return ptr; 407 } 408 409 return __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); 410 } 411 412 /* 413 * Free buffer's data. 414 */ 415 static void free_buffer_data(struct dm_bufio_client *c, 416 void *data, unsigned char data_mode) 417 { 418 switch (data_mode) { 419 case DATA_MODE_SLAB: 420 kmem_cache_free(c->slab_cache, data); 421 break; 422 423 case DATA_MODE_GET_FREE_PAGES: 424 free_pages((unsigned long)data, 425 c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT)); 426 break; 427 428 case DATA_MODE_VMALLOC: 429 vfree(data); 430 break; 431 432 default: 433 DMCRIT("dm_bufio_free_buffer_data: bad data mode: %d", 434 data_mode); 435 BUG(); 436 } 437 } 438 439 /* 440 * Allocate buffer and its data. 441 */ 442 static struct dm_buffer *alloc_buffer(struct dm_bufio_client *c, gfp_t gfp_mask) 443 { 444 struct dm_buffer *b = kmem_cache_alloc(c->slab_buffer, gfp_mask); 445 446 if (!b) 447 return NULL; 448 449 b->c = c; 450 451 b->data = alloc_buffer_data(c, gfp_mask, &b->data_mode); 452 if (!b->data) { 453 kmem_cache_free(c->slab_buffer, b); 454 return NULL; 455 } 456 457 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 458 b->stack_len = 0; 459 #endif 460 return b; 461 } 462 463 /* 464 * Free buffer and its data. 465 */ 466 static void free_buffer(struct dm_buffer *b) 467 { 468 struct dm_bufio_client *c = b->c; 469 470 free_buffer_data(c, b->data, b->data_mode); 471 kmem_cache_free(c->slab_buffer, b); 472 } 473 474 /* 475 * Link buffer to the buffer tree and clean or dirty queue. 476 */ 477 static void __link_buffer(struct dm_buffer *b, sector_t block, int dirty) 478 { 479 struct dm_bufio_client *c = b->c; 480 481 c->n_buffers[dirty]++; 482 b->block = block; 483 b->list_mode = dirty; 484 list_add(&b->lru_list, &c->lru[dirty]); 485 __insert(b->c, b); 486 b->last_accessed = jiffies; 487 488 adjust_total_allocated(b, false); 489 } 490 491 /* 492 * Unlink buffer from the buffer tree and dirty or clean queue. 493 */ 494 static void __unlink_buffer(struct dm_buffer *b) 495 { 496 struct dm_bufio_client *c = b->c; 497 498 BUG_ON(!c->n_buffers[b->list_mode]); 499 500 c->n_buffers[b->list_mode]--; 501 __remove(b->c, b); 502 list_del(&b->lru_list); 503 504 adjust_total_allocated(b, true); 505 } 506 507 /* 508 * Place the buffer to the head of dirty or clean LRU queue. 509 */ 510 static void __relink_lru(struct dm_buffer *b, int dirty) 511 { 512 struct dm_bufio_client *c = b->c; 513 514 b->accessed = 1; 515 516 BUG_ON(!c->n_buffers[b->list_mode]); 517 518 c->n_buffers[b->list_mode]--; 519 c->n_buffers[dirty]++; 520 b->list_mode = dirty; 521 list_move(&b->lru_list, &c->lru[dirty]); 522 b->last_accessed = jiffies; 523 } 524 525 /*---------------------------------------------------------------- 526 * Submit I/O on the buffer. 527 * 528 * Bio interface is faster but it has some problems: 529 * the vector list is limited (increasing this limit increases 530 * memory-consumption per buffer, so it is not viable); 531 * 532 * the memory must be direct-mapped, not vmalloced; 533 * 534 * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and 535 * it is not vmalloced, try using the bio interface. 536 * 537 * If the buffer is big, if it is vmalloced or if the underlying device 538 * rejects the bio because it is too large, use dm-io layer to do the I/O. 539 * The dm-io layer splits the I/O into multiple requests, avoiding the above 540 * shortcomings. 541 *--------------------------------------------------------------*/ 542 543 /* 544 * dm-io completion routine. It just calls b->bio.bi_end_io, pretending 545 * that the request was handled directly with bio interface. 546 */ 547 static void dmio_complete(unsigned long error, void *context) 548 { 549 struct dm_buffer *b = context; 550 551 b->end_io(b, unlikely(error != 0) ? BLK_STS_IOERR : 0); 552 } 553 554 static void use_dmio(struct dm_buffer *b, int rw, sector_t sector, 555 unsigned n_sectors, unsigned offset) 556 { 557 int r; 558 struct dm_io_request io_req = { 559 .bi_op = rw, 560 .bi_op_flags = 0, 561 .notify.fn = dmio_complete, 562 .notify.context = b, 563 .client = b->c->dm_io, 564 }; 565 struct dm_io_region region = { 566 .bdev = b->c->bdev, 567 .sector = sector, 568 .count = n_sectors, 569 }; 570 571 if (b->data_mode != DATA_MODE_VMALLOC) { 572 io_req.mem.type = DM_IO_KMEM; 573 io_req.mem.ptr.addr = (char *)b->data + offset; 574 } else { 575 io_req.mem.type = DM_IO_VMA; 576 io_req.mem.ptr.vma = (char *)b->data + offset; 577 } 578 579 r = dm_io(&io_req, 1, ®ion, NULL); 580 if (unlikely(r)) 581 b->end_io(b, errno_to_blk_status(r)); 582 } 583 584 static void bio_complete(struct bio *bio) 585 { 586 struct dm_buffer *b = bio->bi_private; 587 blk_status_t status = bio->bi_status; 588 bio_put(bio); 589 b->end_io(b, status); 590 } 591 592 static void use_bio(struct dm_buffer *b, int rw, sector_t sector, 593 unsigned n_sectors, unsigned offset) 594 { 595 struct bio *bio; 596 char *ptr; 597 unsigned vec_size, len; 598 599 vec_size = b->c->block_size >> PAGE_SHIFT; 600 if (unlikely(b->c->sectors_per_block_bits < PAGE_SHIFT - SECTOR_SHIFT)) 601 vec_size += 2; 602 603 bio = bio_kmalloc(GFP_NOWAIT | __GFP_NORETRY | __GFP_NOWARN, vec_size); 604 if (!bio) { 605 dmio: 606 use_dmio(b, rw, sector, n_sectors, offset); 607 return; 608 } 609 610 bio->bi_iter.bi_sector = sector; 611 bio_set_dev(bio, b->c->bdev); 612 bio_set_op_attrs(bio, rw, 0); 613 bio->bi_end_io = bio_complete; 614 bio->bi_private = b; 615 616 ptr = (char *)b->data + offset; 617 len = n_sectors << SECTOR_SHIFT; 618 619 do { 620 unsigned this_step = min((unsigned)(PAGE_SIZE - offset_in_page(ptr)), len); 621 if (!bio_add_page(bio, virt_to_page(ptr), this_step, 622 offset_in_page(ptr))) { 623 bio_put(bio); 624 goto dmio; 625 } 626 627 len -= this_step; 628 ptr += this_step; 629 } while (len > 0); 630 631 submit_bio(bio); 632 } 633 634 static void submit_io(struct dm_buffer *b, int rw, void (*end_io)(struct dm_buffer *, blk_status_t)) 635 { 636 unsigned n_sectors; 637 sector_t sector; 638 unsigned offset, end; 639 640 b->end_io = end_io; 641 642 if (likely(b->c->sectors_per_block_bits >= 0)) 643 sector = b->block << b->c->sectors_per_block_bits; 644 else 645 sector = b->block * (b->c->block_size >> SECTOR_SHIFT); 646 sector += b->c->start; 647 648 if (rw != REQ_OP_WRITE) { 649 n_sectors = b->c->block_size >> SECTOR_SHIFT; 650 offset = 0; 651 } else { 652 if (b->c->write_callback) 653 b->c->write_callback(b); 654 offset = b->write_start; 655 end = b->write_end; 656 offset &= -DM_BUFIO_WRITE_ALIGN; 657 end += DM_BUFIO_WRITE_ALIGN - 1; 658 end &= -DM_BUFIO_WRITE_ALIGN; 659 if (unlikely(end > b->c->block_size)) 660 end = b->c->block_size; 661 662 sector += offset >> SECTOR_SHIFT; 663 n_sectors = (end - offset) >> SECTOR_SHIFT; 664 } 665 666 if (b->data_mode != DATA_MODE_VMALLOC) 667 use_bio(b, rw, sector, n_sectors, offset); 668 else 669 use_dmio(b, rw, sector, n_sectors, offset); 670 } 671 672 /*---------------------------------------------------------------- 673 * Writing dirty buffers 674 *--------------------------------------------------------------*/ 675 676 /* 677 * The endio routine for write. 678 * 679 * Set the error, clear B_WRITING bit and wake anyone who was waiting on 680 * it. 681 */ 682 static void write_endio(struct dm_buffer *b, blk_status_t status) 683 { 684 b->write_error = status; 685 if (unlikely(status)) { 686 struct dm_bufio_client *c = b->c; 687 688 (void)cmpxchg(&c->async_write_error, 0, 689 blk_status_to_errno(status)); 690 } 691 692 BUG_ON(!test_bit(B_WRITING, &b->state)); 693 694 smp_mb__before_atomic(); 695 clear_bit(B_WRITING, &b->state); 696 smp_mb__after_atomic(); 697 698 wake_up_bit(&b->state, B_WRITING); 699 } 700 701 /* 702 * Initiate a write on a dirty buffer, but don't wait for it. 703 * 704 * - If the buffer is not dirty, exit. 705 * - If there some previous write going on, wait for it to finish (we can't 706 * have two writes on the same buffer simultaneously). 707 * - Submit our write and don't wait on it. We set B_WRITING indicating 708 * that there is a write in progress. 709 */ 710 static void __write_dirty_buffer(struct dm_buffer *b, 711 struct list_head *write_list) 712 { 713 if (!test_bit(B_DIRTY, &b->state)) 714 return; 715 716 clear_bit(B_DIRTY, &b->state); 717 wait_on_bit_lock_io(&b->state, B_WRITING, TASK_UNINTERRUPTIBLE); 718 719 b->write_start = b->dirty_start; 720 b->write_end = b->dirty_end; 721 722 if (!write_list) 723 submit_io(b, REQ_OP_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, REQ_OP_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 * Check if we're over watermark. 936 * If we are over threshold_buffers, start freeing buffers. 937 * If we're over "limit_buffers", block until we get under the limit. 938 */ 939 static void __check_watermark(struct dm_bufio_client *c, 940 struct list_head *write_list) 941 { 942 if (c->n_buffers[LIST_DIRTY] > c->n_buffers[LIST_CLEAN] * DM_BUFIO_WRITEBACK_RATIO) 943 __write_dirty_buffers_async(c, 1, write_list); 944 } 945 946 /*---------------------------------------------------------------- 947 * Getting a buffer 948 *--------------------------------------------------------------*/ 949 950 static struct dm_buffer *__bufio_new(struct dm_bufio_client *c, sector_t block, 951 enum new_flag nf, int *need_submit, 952 struct list_head *write_list) 953 { 954 struct dm_buffer *b, *new_b = NULL; 955 956 *need_submit = 0; 957 958 b = __find(c, block); 959 if (b) 960 goto found_buffer; 961 962 if (nf == NF_GET) 963 return NULL; 964 965 new_b = __alloc_buffer_wait(c, nf); 966 if (!new_b) 967 return NULL; 968 969 /* 970 * We've had a period where the mutex was unlocked, so need to 971 * recheck the buffer tree. 972 */ 973 b = __find(c, block); 974 if (b) { 975 __free_buffer_wake(new_b); 976 goto found_buffer; 977 } 978 979 __check_watermark(c, write_list); 980 981 b = new_b; 982 b->hold_count = 1; 983 b->read_error = 0; 984 b->write_error = 0; 985 __link_buffer(b, block, LIST_CLEAN); 986 987 if (nf == NF_FRESH) { 988 b->state = 0; 989 return b; 990 } 991 992 b->state = 1 << B_READING; 993 *need_submit = 1; 994 995 return b; 996 997 found_buffer: 998 if (nf == NF_PREFETCH) 999 return NULL; 1000 /* 1001 * Note: it is essential that we don't wait for the buffer to be 1002 * read if dm_bufio_get function is used. Both dm_bufio_get and 1003 * dm_bufio_prefetch can be used in the driver request routine. 1004 * If the user called both dm_bufio_prefetch and dm_bufio_get on 1005 * the same buffer, it would deadlock if we waited. 1006 */ 1007 if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state))) 1008 return NULL; 1009 1010 b->hold_count++; 1011 __relink_lru(b, test_bit(B_DIRTY, &b->state) || 1012 test_bit(B_WRITING, &b->state)); 1013 return b; 1014 } 1015 1016 /* 1017 * The endio routine for reading: set the error, clear the bit and wake up 1018 * anyone waiting on the buffer. 1019 */ 1020 static void read_endio(struct dm_buffer *b, blk_status_t status) 1021 { 1022 b->read_error = status; 1023 1024 BUG_ON(!test_bit(B_READING, &b->state)); 1025 1026 smp_mb__before_atomic(); 1027 clear_bit(B_READING, &b->state); 1028 smp_mb__after_atomic(); 1029 1030 wake_up_bit(&b->state, B_READING); 1031 } 1032 1033 /* 1034 * A common routine for dm_bufio_new and dm_bufio_read. Operation of these 1035 * functions is similar except that dm_bufio_new doesn't read the 1036 * buffer from the disk (assuming that the caller overwrites all the data 1037 * and uses dm_bufio_mark_buffer_dirty to write new data back). 1038 */ 1039 static void *new_read(struct dm_bufio_client *c, sector_t block, 1040 enum new_flag nf, struct dm_buffer **bp) 1041 { 1042 int need_submit; 1043 struct dm_buffer *b; 1044 1045 LIST_HEAD(write_list); 1046 1047 dm_bufio_lock(c); 1048 b = __bufio_new(c, block, nf, &need_submit, &write_list); 1049 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 1050 if (b && b->hold_count == 1) 1051 buffer_record_stack(b); 1052 #endif 1053 dm_bufio_unlock(c); 1054 1055 __flush_write_list(&write_list); 1056 1057 if (!b) 1058 return NULL; 1059 1060 if (need_submit) 1061 submit_io(b, REQ_OP_READ, read_endio); 1062 1063 wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE); 1064 1065 if (b->read_error) { 1066 int error = blk_status_to_errno(b->read_error); 1067 1068 dm_bufio_release(b); 1069 1070 return ERR_PTR(error); 1071 } 1072 1073 *bp = b; 1074 1075 return b->data; 1076 } 1077 1078 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block, 1079 struct dm_buffer **bp) 1080 { 1081 return new_read(c, block, NF_GET, bp); 1082 } 1083 EXPORT_SYMBOL_GPL(dm_bufio_get); 1084 1085 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block, 1086 struct dm_buffer **bp) 1087 { 1088 BUG_ON(dm_bufio_in_request()); 1089 1090 return new_read(c, block, NF_READ, bp); 1091 } 1092 EXPORT_SYMBOL_GPL(dm_bufio_read); 1093 1094 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block, 1095 struct dm_buffer **bp) 1096 { 1097 BUG_ON(dm_bufio_in_request()); 1098 1099 return new_read(c, block, NF_FRESH, bp); 1100 } 1101 EXPORT_SYMBOL_GPL(dm_bufio_new); 1102 1103 void dm_bufio_prefetch(struct dm_bufio_client *c, 1104 sector_t block, unsigned n_blocks) 1105 { 1106 struct blk_plug plug; 1107 1108 LIST_HEAD(write_list); 1109 1110 BUG_ON(dm_bufio_in_request()); 1111 1112 blk_start_plug(&plug); 1113 dm_bufio_lock(c); 1114 1115 for (; n_blocks--; block++) { 1116 int need_submit; 1117 struct dm_buffer *b; 1118 b = __bufio_new(c, block, NF_PREFETCH, &need_submit, 1119 &write_list); 1120 if (unlikely(!list_empty(&write_list))) { 1121 dm_bufio_unlock(c); 1122 blk_finish_plug(&plug); 1123 __flush_write_list(&write_list); 1124 blk_start_plug(&plug); 1125 dm_bufio_lock(c); 1126 } 1127 if (unlikely(b != NULL)) { 1128 dm_bufio_unlock(c); 1129 1130 if (need_submit) 1131 submit_io(b, REQ_OP_READ, read_endio); 1132 dm_bufio_release(b); 1133 1134 cond_resched(); 1135 1136 if (!n_blocks) 1137 goto flush_plug; 1138 dm_bufio_lock(c); 1139 } 1140 } 1141 1142 dm_bufio_unlock(c); 1143 1144 flush_plug: 1145 blk_finish_plug(&plug); 1146 } 1147 EXPORT_SYMBOL_GPL(dm_bufio_prefetch); 1148 1149 void dm_bufio_release(struct dm_buffer *b) 1150 { 1151 struct dm_bufio_client *c = b->c; 1152 1153 dm_bufio_lock(c); 1154 1155 BUG_ON(!b->hold_count); 1156 1157 b->hold_count--; 1158 if (!b->hold_count) { 1159 wake_up(&c->free_buffer_wait); 1160 1161 /* 1162 * If there were errors on the buffer, and the buffer is not 1163 * to be written, free the buffer. There is no point in caching 1164 * invalid buffer. 1165 */ 1166 if ((b->read_error || b->write_error) && 1167 !test_bit(B_READING, &b->state) && 1168 !test_bit(B_WRITING, &b->state) && 1169 !test_bit(B_DIRTY, &b->state)) { 1170 __unlink_buffer(b); 1171 __free_buffer_wake(b); 1172 } 1173 } 1174 1175 dm_bufio_unlock(c); 1176 } 1177 EXPORT_SYMBOL_GPL(dm_bufio_release); 1178 1179 void dm_bufio_mark_partial_buffer_dirty(struct dm_buffer *b, 1180 unsigned start, unsigned end) 1181 { 1182 struct dm_bufio_client *c = b->c; 1183 1184 BUG_ON(start >= end); 1185 BUG_ON(end > b->c->block_size); 1186 1187 dm_bufio_lock(c); 1188 1189 BUG_ON(test_bit(B_READING, &b->state)); 1190 1191 if (!test_and_set_bit(B_DIRTY, &b->state)) { 1192 b->dirty_start = start; 1193 b->dirty_end = end; 1194 __relink_lru(b, LIST_DIRTY); 1195 } else { 1196 if (start < b->dirty_start) 1197 b->dirty_start = start; 1198 if (end > b->dirty_end) 1199 b->dirty_end = end; 1200 } 1201 1202 dm_bufio_unlock(c); 1203 } 1204 EXPORT_SYMBOL_GPL(dm_bufio_mark_partial_buffer_dirty); 1205 1206 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b) 1207 { 1208 dm_bufio_mark_partial_buffer_dirty(b, 0, b->c->block_size); 1209 } 1210 EXPORT_SYMBOL_GPL(dm_bufio_mark_buffer_dirty); 1211 1212 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c) 1213 { 1214 LIST_HEAD(write_list); 1215 1216 BUG_ON(dm_bufio_in_request()); 1217 1218 dm_bufio_lock(c); 1219 __write_dirty_buffers_async(c, 0, &write_list); 1220 dm_bufio_unlock(c); 1221 __flush_write_list(&write_list); 1222 } 1223 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers_async); 1224 1225 /* 1226 * For performance, it is essential that the buffers are written asynchronously 1227 * and simultaneously (so that the block layer can merge the writes) and then 1228 * waited upon. 1229 * 1230 * Finally, we flush hardware disk cache. 1231 */ 1232 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c) 1233 { 1234 int a, f; 1235 unsigned long buffers_processed = 0; 1236 struct dm_buffer *b, *tmp; 1237 1238 LIST_HEAD(write_list); 1239 1240 dm_bufio_lock(c); 1241 __write_dirty_buffers_async(c, 0, &write_list); 1242 dm_bufio_unlock(c); 1243 __flush_write_list(&write_list); 1244 dm_bufio_lock(c); 1245 1246 again: 1247 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_DIRTY], lru_list) { 1248 int dropped_lock = 0; 1249 1250 if (buffers_processed < c->n_buffers[LIST_DIRTY]) 1251 buffers_processed++; 1252 1253 BUG_ON(test_bit(B_READING, &b->state)); 1254 1255 if (test_bit(B_WRITING, &b->state)) { 1256 if (buffers_processed < c->n_buffers[LIST_DIRTY]) { 1257 dropped_lock = 1; 1258 b->hold_count++; 1259 dm_bufio_unlock(c); 1260 wait_on_bit_io(&b->state, B_WRITING, 1261 TASK_UNINTERRUPTIBLE); 1262 dm_bufio_lock(c); 1263 b->hold_count--; 1264 } else 1265 wait_on_bit_io(&b->state, B_WRITING, 1266 TASK_UNINTERRUPTIBLE); 1267 } 1268 1269 if (!test_bit(B_DIRTY, &b->state) && 1270 !test_bit(B_WRITING, &b->state)) 1271 __relink_lru(b, LIST_CLEAN); 1272 1273 cond_resched(); 1274 1275 /* 1276 * If we dropped the lock, the list is no longer consistent, 1277 * so we must restart the search. 1278 * 1279 * In the most common case, the buffer just processed is 1280 * relinked to the clean list, so we won't loop scanning the 1281 * same buffer again and again. 1282 * 1283 * This may livelock if there is another thread simultaneously 1284 * dirtying buffers, so we count the number of buffers walked 1285 * and if it exceeds the total number of buffers, it means that 1286 * someone is doing some writes simultaneously with us. In 1287 * this case, stop, dropping the lock. 1288 */ 1289 if (dropped_lock) 1290 goto again; 1291 } 1292 wake_up(&c->free_buffer_wait); 1293 dm_bufio_unlock(c); 1294 1295 a = xchg(&c->async_write_error, 0); 1296 f = dm_bufio_issue_flush(c); 1297 if (a) 1298 return a; 1299 1300 return f; 1301 } 1302 EXPORT_SYMBOL_GPL(dm_bufio_write_dirty_buffers); 1303 1304 /* 1305 * Use dm-io to send an empty barrier to flush the device. 1306 */ 1307 int dm_bufio_issue_flush(struct dm_bufio_client *c) 1308 { 1309 struct dm_io_request io_req = { 1310 .bi_op = REQ_OP_WRITE, 1311 .bi_op_flags = REQ_PREFLUSH | REQ_SYNC, 1312 .mem.type = DM_IO_KMEM, 1313 .mem.ptr.addr = NULL, 1314 .client = c->dm_io, 1315 }; 1316 struct dm_io_region io_reg = { 1317 .bdev = c->bdev, 1318 .sector = 0, 1319 .count = 0, 1320 }; 1321 1322 BUG_ON(dm_bufio_in_request()); 1323 1324 return dm_io(&io_req, 1, &io_reg, NULL); 1325 } 1326 EXPORT_SYMBOL_GPL(dm_bufio_issue_flush); 1327 1328 /* 1329 * We first delete any other buffer that may be at that new location. 1330 * 1331 * Then, we write the buffer to the original location if it was dirty. 1332 * 1333 * Then, if we are the only one who is holding the buffer, relink the buffer 1334 * in the buffer tree for the new location. 1335 * 1336 * If there was someone else holding the buffer, we write it to the new 1337 * location but not relink it, because that other user needs to have the buffer 1338 * at the same place. 1339 */ 1340 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block) 1341 { 1342 struct dm_bufio_client *c = b->c; 1343 struct dm_buffer *new; 1344 1345 BUG_ON(dm_bufio_in_request()); 1346 1347 dm_bufio_lock(c); 1348 1349 retry: 1350 new = __find(c, new_block); 1351 if (new) { 1352 if (new->hold_count) { 1353 __wait_for_free_buffer(c); 1354 goto retry; 1355 } 1356 1357 /* 1358 * FIXME: Is there any point waiting for a write that's going 1359 * to be overwritten in a bit? 1360 */ 1361 __make_buffer_clean(new); 1362 __unlink_buffer(new); 1363 __free_buffer_wake(new); 1364 } 1365 1366 BUG_ON(!b->hold_count); 1367 BUG_ON(test_bit(B_READING, &b->state)); 1368 1369 __write_dirty_buffer(b, NULL); 1370 if (b->hold_count == 1) { 1371 wait_on_bit_io(&b->state, B_WRITING, 1372 TASK_UNINTERRUPTIBLE); 1373 set_bit(B_DIRTY, &b->state); 1374 b->dirty_start = 0; 1375 b->dirty_end = c->block_size; 1376 __unlink_buffer(b); 1377 __link_buffer(b, new_block, LIST_DIRTY); 1378 } else { 1379 sector_t old_block; 1380 wait_on_bit_lock_io(&b->state, B_WRITING, 1381 TASK_UNINTERRUPTIBLE); 1382 /* 1383 * Relink buffer to "new_block" so that write_callback 1384 * sees "new_block" as a block number. 1385 * After the write, link the buffer back to old_block. 1386 * All this must be done in bufio lock, so that block number 1387 * change isn't visible to other threads. 1388 */ 1389 old_block = b->block; 1390 __unlink_buffer(b); 1391 __link_buffer(b, new_block, b->list_mode); 1392 submit_io(b, REQ_OP_WRITE, write_endio); 1393 wait_on_bit_io(&b->state, B_WRITING, 1394 TASK_UNINTERRUPTIBLE); 1395 __unlink_buffer(b); 1396 __link_buffer(b, old_block, b->list_mode); 1397 } 1398 1399 dm_bufio_unlock(c); 1400 dm_bufio_release(b); 1401 } 1402 EXPORT_SYMBOL_GPL(dm_bufio_release_move); 1403 1404 /* 1405 * Free the given buffer. 1406 * 1407 * This is just a hint, if the buffer is in use or dirty, this function 1408 * does nothing. 1409 */ 1410 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block) 1411 { 1412 struct dm_buffer *b; 1413 1414 dm_bufio_lock(c); 1415 1416 b = __find(c, block); 1417 if (b && likely(!b->hold_count) && likely(!b->state)) { 1418 __unlink_buffer(b); 1419 __free_buffer_wake(b); 1420 } 1421 1422 dm_bufio_unlock(c); 1423 } 1424 EXPORT_SYMBOL_GPL(dm_bufio_forget); 1425 1426 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n) 1427 { 1428 c->minimum_buffers = n; 1429 } 1430 EXPORT_SYMBOL_GPL(dm_bufio_set_minimum_buffers); 1431 1432 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c) 1433 { 1434 return c->block_size; 1435 } 1436 EXPORT_SYMBOL_GPL(dm_bufio_get_block_size); 1437 1438 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c) 1439 { 1440 sector_t s = i_size_read(c->bdev->bd_inode) >> SECTOR_SHIFT; 1441 if (likely(c->sectors_per_block_bits >= 0)) 1442 s >>= c->sectors_per_block_bits; 1443 else 1444 sector_div(s, c->block_size >> SECTOR_SHIFT); 1445 return s; 1446 } 1447 EXPORT_SYMBOL_GPL(dm_bufio_get_device_size); 1448 1449 sector_t dm_bufio_get_block_number(struct dm_buffer *b) 1450 { 1451 return b->block; 1452 } 1453 EXPORT_SYMBOL_GPL(dm_bufio_get_block_number); 1454 1455 void *dm_bufio_get_block_data(struct dm_buffer *b) 1456 { 1457 return b->data; 1458 } 1459 EXPORT_SYMBOL_GPL(dm_bufio_get_block_data); 1460 1461 void *dm_bufio_get_aux_data(struct dm_buffer *b) 1462 { 1463 return b + 1; 1464 } 1465 EXPORT_SYMBOL_GPL(dm_bufio_get_aux_data); 1466 1467 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b) 1468 { 1469 return b->c; 1470 } 1471 EXPORT_SYMBOL_GPL(dm_bufio_get_client); 1472 1473 static void drop_buffers(struct dm_bufio_client *c) 1474 { 1475 struct dm_buffer *b; 1476 int i; 1477 bool warned = false; 1478 1479 BUG_ON(dm_bufio_in_request()); 1480 1481 /* 1482 * An optimization so that the buffers are not written one-by-one. 1483 */ 1484 dm_bufio_write_dirty_buffers_async(c); 1485 1486 dm_bufio_lock(c); 1487 1488 while ((b = __get_unclaimed_buffer(c))) 1489 __free_buffer_wake(b); 1490 1491 for (i = 0; i < LIST_SIZE; i++) 1492 list_for_each_entry(b, &c->lru[i], lru_list) { 1493 WARN_ON(!warned); 1494 warned = true; 1495 DMERR("leaked buffer %llx, hold count %u, list %d", 1496 (unsigned long long)b->block, b->hold_count, i); 1497 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 1498 stack_trace_print(b->stack_entries, b->stack_len, 1); 1499 /* mark unclaimed to avoid BUG_ON below */ 1500 b->hold_count = 0; 1501 #endif 1502 } 1503 1504 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING 1505 while ((b = __get_unclaimed_buffer(c))) 1506 __free_buffer_wake(b); 1507 #endif 1508 1509 for (i = 0; i < LIST_SIZE; i++) 1510 BUG_ON(!list_empty(&c->lru[i])); 1511 1512 dm_bufio_unlock(c); 1513 } 1514 1515 /* 1516 * We may not be able to evict this buffer if IO pending or the client 1517 * is still using it. Caller is expected to know buffer is too old. 1518 * 1519 * And if GFP_NOFS is used, we must not do any I/O because we hold 1520 * dm_bufio_clients_lock and we would risk deadlock if the I/O gets 1521 * rerouted to different bufio client. 1522 */ 1523 static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp) 1524 { 1525 if (!(gfp & __GFP_FS)) { 1526 if (test_bit(B_READING, &b->state) || 1527 test_bit(B_WRITING, &b->state) || 1528 test_bit(B_DIRTY, &b->state)) 1529 return false; 1530 } 1531 1532 if (b->hold_count) 1533 return false; 1534 1535 __make_buffer_clean(b); 1536 __unlink_buffer(b); 1537 __free_buffer_wake(b); 1538 1539 return true; 1540 } 1541 1542 static unsigned long get_retain_buffers(struct dm_bufio_client *c) 1543 { 1544 unsigned long retain_bytes = READ_ONCE(dm_bufio_retain_bytes); 1545 if (likely(c->sectors_per_block_bits >= 0)) 1546 retain_bytes >>= c->sectors_per_block_bits + SECTOR_SHIFT; 1547 else 1548 retain_bytes /= c->block_size; 1549 return retain_bytes; 1550 } 1551 1552 static unsigned long __scan(struct dm_bufio_client *c, unsigned long nr_to_scan, 1553 gfp_t gfp_mask) 1554 { 1555 int l; 1556 struct dm_buffer *b, *tmp; 1557 unsigned long freed = 0; 1558 unsigned long count = c->n_buffers[LIST_CLEAN] + 1559 c->n_buffers[LIST_DIRTY]; 1560 unsigned long retain_target = get_retain_buffers(c); 1561 1562 for (l = 0; l < LIST_SIZE; l++) { 1563 list_for_each_entry_safe_reverse(b, tmp, &c->lru[l], lru_list) { 1564 if (__try_evict_buffer(b, gfp_mask)) 1565 freed++; 1566 if (!--nr_to_scan || ((count - freed) <= retain_target)) 1567 return freed; 1568 cond_resched(); 1569 } 1570 } 1571 return freed; 1572 } 1573 1574 static unsigned long 1575 dm_bufio_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) 1576 { 1577 struct dm_bufio_client *c; 1578 unsigned long freed; 1579 1580 c = container_of(shrink, struct dm_bufio_client, shrinker); 1581 if (sc->gfp_mask & __GFP_FS) 1582 dm_bufio_lock(c); 1583 else if (!dm_bufio_trylock(c)) 1584 return SHRINK_STOP; 1585 1586 freed = __scan(c, sc->nr_to_scan, sc->gfp_mask); 1587 dm_bufio_unlock(c); 1588 return freed; 1589 } 1590 1591 static unsigned long 1592 dm_bufio_shrink_count(struct shrinker *shrink, struct shrink_control *sc) 1593 { 1594 struct dm_bufio_client *c = container_of(shrink, struct dm_bufio_client, shrinker); 1595 unsigned long count = READ_ONCE(c->n_buffers[LIST_CLEAN]) + 1596 READ_ONCE(c->n_buffers[LIST_DIRTY]); 1597 unsigned long retain_target = get_retain_buffers(c); 1598 1599 return (count < retain_target) ? 0 : (count - retain_target); 1600 } 1601 1602 /* 1603 * Create the buffering interface 1604 */ 1605 struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsigned block_size, 1606 unsigned reserved_buffers, unsigned aux_size, 1607 void (*alloc_callback)(struct dm_buffer *), 1608 void (*write_callback)(struct dm_buffer *)) 1609 { 1610 int r; 1611 struct dm_bufio_client *c; 1612 unsigned i; 1613 char slab_name[27]; 1614 1615 if (!block_size || block_size & ((1 << SECTOR_SHIFT) - 1)) { 1616 DMERR("%s: block size not specified or is not multiple of 512b", __func__); 1617 r = -EINVAL; 1618 goto bad_client; 1619 } 1620 1621 c = kzalloc(sizeof(*c), GFP_KERNEL); 1622 if (!c) { 1623 r = -ENOMEM; 1624 goto bad_client; 1625 } 1626 c->buffer_tree = RB_ROOT; 1627 1628 c->bdev = bdev; 1629 c->block_size = block_size; 1630 if (is_power_of_2(block_size)) 1631 c->sectors_per_block_bits = __ffs(block_size) - SECTOR_SHIFT; 1632 else 1633 c->sectors_per_block_bits = -1; 1634 1635 c->alloc_callback = alloc_callback; 1636 c->write_callback = write_callback; 1637 1638 for (i = 0; i < LIST_SIZE; i++) { 1639 INIT_LIST_HEAD(&c->lru[i]); 1640 c->n_buffers[i] = 0; 1641 } 1642 1643 mutex_init(&c->lock); 1644 INIT_LIST_HEAD(&c->reserved_buffers); 1645 c->need_reserved_buffers = reserved_buffers; 1646 1647 dm_bufio_set_minimum_buffers(c, DM_BUFIO_MIN_BUFFERS); 1648 1649 init_waitqueue_head(&c->free_buffer_wait); 1650 c->async_write_error = 0; 1651 1652 c->dm_io = dm_io_client_create(); 1653 if (IS_ERR(c->dm_io)) { 1654 r = PTR_ERR(c->dm_io); 1655 goto bad_dm_io; 1656 } 1657 1658 if (block_size <= KMALLOC_MAX_SIZE && 1659 (block_size < PAGE_SIZE || !is_power_of_2(block_size))) { 1660 unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE); 1661 snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size); 1662 c->slab_cache = kmem_cache_create(slab_name, block_size, align, 1663 SLAB_RECLAIM_ACCOUNT, NULL); 1664 if (!c->slab_cache) { 1665 r = -ENOMEM; 1666 goto bad; 1667 } 1668 } 1669 if (aux_size) 1670 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer-%u", aux_size); 1671 else 1672 snprintf(slab_name, sizeof slab_name, "dm_bufio_buffer"); 1673 c->slab_buffer = kmem_cache_create(slab_name, sizeof(struct dm_buffer) + aux_size, 1674 0, SLAB_RECLAIM_ACCOUNT, NULL); 1675 if (!c->slab_buffer) { 1676 r = -ENOMEM; 1677 goto bad; 1678 } 1679 1680 while (c->need_reserved_buffers) { 1681 struct dm_buffer *b = alloc_buffer(c, GFP_KERNEL); 1682 1683 if (!b) { 1684 r = -ENOMEM; 1685 goto bad; 1686 } 1687 __free_buffer_wake(b); 1688 } 1689 1690 c->shrinker.count_objects = dm_bufio_shrink_count; 1691 c->shrinker.scan_objects = dm_bufio_shrink_scan; 1692 c->shrinker.seeks = 1; 1693 c->shrinker.batch = 0; 1694 r = register_shrinker(&c->shrinker); 1695 if (r) 1696 goto bad; 1697 1698 mutex_lock(&dm_bufio_clients_lock); 1699 dm_bufio_client_count++; 1700 list_add(&c->client_list, &dm_bufio_all_clients); 1701 __cache_size_refresh(); 1702 mutex_unlock(&dm_bufio_clients_lock); 1703 1704 return c; 1705 1706 bad: 1707 while (!list_empty(&c->reserved_buffers)) { 1708 struct dm_buffer *b = list_entry(c->reserved_buffers.next, 1709 struct dm_buffer, lru_list); 1710 list_del(&b->lru_list); 1711 free_buffer(b); 1712 } 1713 kmem_cache_destroy(c->slab_cache); 1714 kmem_cache_destroy(c->slab_buffer); 1715 dm_io_client_destroy(c->dm_io); 1716 bad_dm_io: 1717 mutex_destroy(&c->lock); 1718 kfree(c); 1719 bad_client: 1720 return ERR_PTR(r); 1721 } 1722 EXPORT_SYMBOL_GPL(dm_bufio_client_create); 1723 1724 /* 1725 * Free the buffering interface. 1726 * It is required that there are no references on any buffers. 1727 */ 1728 void dm_bufio_client_destroy(struct dm_bufio_client *c) 1729 { 1730 unsigned i; 1731 1732 drop_buffers(c); 1733 1734 unregister_shrinker(&c->shrinker); 1735 1736 mutex_lock(&dm_bufio_clients_lock); 1737 1738 list_del(&c->client_list); 1739 dm_bufio_client_count--; 1740 __cache_size_refresh(); 1741 1742 mutex_unlock(&dm_bufio_clients_lock); 1743 1744 BUG_ON(!RB_EMPTY_ROOT(&c->buffer_tree)); 1745 BUG_ON(c->need_reserved_buffers); 1746 1747 while (!list_empty(&c->reserved_buffers)) { 1748 struct dm_buffer *b = list_entry(c->reserved_buffers.next, 1749 struct dm_buffer, lru_list); 1750 list_del(&b->lru_list); 1751 free_buffer(b); 1752 } 1753 1754 for (i = 0; i < LIST_SIZE; i++) 1755 if (c->n_buffers[i]) 1756 DMERR("leaked buffer count %d: %ld", i, c->n_buffers[i]); 1757 1758 for (i = 0; i < LIST_SIZE; i++) 1759 BUG_ON(c->n_buffers[i]); 1760 1761 kmem_cache_destroy(c->slab_cache); 1762 kmem_cache_destroy(c->slab_buffer); 1763 dm_io_client_destroy(c->dm_io); 1764 mutex_destroy(&c->lock); 1765 kfree(c); 1766 } 1767 EXPORT_SYMBOL_GPL(dm_bufio_client_destroy); 1768 1769 void dm_bufio_set_sector_offset(struct dm_bufio_client *c, sector_t start) 1770 { 1771 c->start = start; 1772 } 1773 EXPORT_SYMBOL_GPL(dm_bufio_set_sector_offset); 1774 1775 static unsigned get_max_age_hz(void) 1776 { 1777 unsigned max_age = READ_ONCE(dm_bufio_max_age); 1778 1779 if (max_age > UINT_MAX / HZ) 1780 max_age = UINT_MAX / HZ; 1781 1782 return max_age * HZ; 1783 } 1784 1785 static bool older_than(struct dm_buffer *b, unsigned long age_hz) 1786 { 1787 return time_after_eq(jiffies, b->last_accessed + age_hz); 1788 } 1789 1790 static void __evict_old_buffers(struct dm_bufio_client *c, unsigned long age_hz) 1791 { 1792 struct dm_buffer *b, *tmp; 1793 unsigned long retain_target = get_retain_buffers(c); 1794 unsigned long count; 1795 LIST_HEAD(write_list); 1796 1797 dm_bufio_lock(c); 1798 1799 __check_watermark(c, &write_list); 1800 if (unlikely(!list_empty(&write_list))) { 1801 dm_bufio_unlock(c); 1802 __flush_write_list(&write_list); 1803 dm_bufio_lock(c); 1804 } 1805 1806 count = c->n_buffers[LIST_CLEAN] + c->n_buffers[LIST_DIRTY]; 1807 list_for_each_entry_safe_reverse(b, tmp, &c->lru[LIST_CLEAN], lru_list) { 1808 if (count <= retain_target) 1809 break; 1810 1811 if (!older_than(b, age_hz)) 1812 break; 1813 1814 if (__try_evict_buffer(b, 0)) 1815 count--; 1816 1817 cond_resched(); 1818 } 1819 1820 dm_bufio_unlock(c); 1821 } 1822 1823 static void do_global_cleanup(struct work_struct *w) 1824 { 1825 struct dm_bufio_client *locked_client = NULL; 1826 struct dm_bufio_client *current_client; 1827 struct dm_buffer *b; 1828 unsigned spinlock_hold_count; 1829 unsigned long threshold = dm_bufio_cache_size - 1830 dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO; 1831 unsigned long loops = global_num * 2; 1832 1833 mutex_lock(&dm_bufio_clients_lock); 1834 1835 while (1) { 1836 cond_resched(); 1837 1838 spin_lock(&global_spinlock); 1839 if (unlikely(dm_bufio_current_allocated <= threshold)) 1840 break; 1841 1842 spinlock_hold_count = 0; 1843 get_next: 1844 if (!loops--) 1845 break; 1846 if (unlikely(list_empty(&global_queue))) 1847 break; 1848 b = list_entry(global_queue.prev, struct dm_buffer, global_list); 1849 1850 if (b->accessed) { 1851 b->accessed = 0; 1852 list_move(&b->global_list, &global_queue); 1853 if (likely(++spinlock_hold_count < 16)) 1854 goto get_next; 1855 spin_unlock(&global_spinlock); 1856 continue; 1857 } 1858 1859 current_client = b->c; 1860 if (unlikely(current_client != locked_client)) { 1861 if (locked_client) 1862 dm_bufio_unlock(locked_client); 1863 1864 if (!dm_bufio_trylock(current_client)) { 1865 spin_unlock(&global_spinlock); 1866 dm_bufio_lock(current_client); 1867 locked_client = current_client; 1868 continue; 1869 } 1870 1871 locked_client = current_client; 1872 } 1873 1874 spin_unlock(&global_spinlock); 1875 1876 if (unlikely(!__try_evict_buffer(b, GFP_KERNEL))) { 1877 spin_lock(&global_spinlock); 1878 list_move(&b->global_list, &global_queue); 1879 spin_unlock(&global_spinlock); 1880 } 1881 } 1882 1883 spin_unlock(&global_spinlock); 1884 1885 if (locked_client) 1886 dm_bufio_unlock(locked_client); 1887 1888 mutex_unlock(&dm_bufio_clients_lock); 1889 } 1890 1891 static void cleanup_old_buffers(void) 1892 { 1893 unsigned long max_age_hz = get_max_age_hz(); 1894 struct dm_bufio_client *c; 1895 1896 mutex_lock(&dm_bufio_clients_lock); 1897 1898 __cache_size_refresh(); 1899 1900 list_for_each_entry(c, &dm_bufio_all_clients, client_list) 1901 __evict_old_buffers(c, max_age_hz); 1902 1903 mutex_unlock(&dm_bufio_clients_lock); 1904 } 1905 1906 static void work_fn(struct work_struct *w) 1907 { 1908 cleanup_old_buffers(); 1909 1910 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work, 1911 DM_BUFIO_WORK_TIMER_SECS * HZ); 1912 } 1913 1914 /*---------------------------------------------------------------- 1915 * Module setup 1916 *--------------------------------------------------------------*/ 1917 1918 /* 1919 * This is called only once for the whole dm_bufio module. 1920 * It initializes memory limit. 1921 */ 1922 static int __init dm_bufio_init(void) 1923 { 1924 __u64 mem; 1925 1926 dm_bufio_allocated_kmem_cache = 0; 1927 dm_bufio_allocated_get_free_pages = 0; 1928 dm_bufio_allocated_vmalloc = 0; 1929 dm_bufio_current_allocated = 0; 1930 1931 mem = (__u64)mult_frac(totalram_pages() - totalhigh_pages(), 1932 DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT; 1933 1934 if (mem > ULONG_MAX) 1935 mem = ULONG_MAX; 1936 1937 #ifdef CONFIG_MMU 1938 if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100)) 1939 mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100); 1940 #endif 1941 1942 dm_bufio_default_cache_size = mem; 1943 1944 mutex_lock(&dm_bufio_clients_lock); 1945 __cache_size_refresh(); 1946 mutex_unlock(&dm_bufio_clients_lock); 1947 1948 dm_bufio_wq = alloc_workqueue("dm_bufio_cache", WQ_MEM_RECLAIM, 0); 1949 if (!dm_bufio_wq) 1950 return -ENOMEM; 1951 1952 INIT_DELAYED_WORK(&dm_bufio_cleanup_old_work, work_fn); 1953 INIT_WORK(&dm_bufio_replacement_work, do_global_cleanup); 1954 queue_delayed_work(dm_bufio_wq, &dm_bufio_cleanup_old_work, 1955 DM_BUFIO_WORK_TIMER_SECS * HZ); 1956 1957 return 0; 1958 } 1959 1960 /* 1961 * This is called once when unloading the dm_bufio module. 1962 */ 1963 static void __exit dm_bufio_exit(void) 1964 { 1965 int bug = 0; 1966 1967 cancel_delayed_work_sync(&dm_bufio_cleanup_old_work); 1968 flush_workqueue(dm_bufio_wq); 1969 destroy_workqueue(dm_bufio_wq); 1970 1971 if (dm_bufio_client_count) { 1972 DMCRIT("%s: dm_bufio_client_count leaked: %d", 1973 __func__, dm_bufio_client_count); 1974 bug = 1; 1975 } 1976 1977 if (dm_bufio_current_allocated) { 1978 DMCRIT("%s: dm_bufio_current_allocated leaked: %lu", 1979 __func__, dm_bufio_current_allocated); 1980 bug = 1; 1981 } 1982 1983 if (dm_bufio_allocated_get_free_pages) { 1984 DMCRIT("%s: dm_bufio_allocated_get_free_pages leaked: %lu", 1985 __func__, dm_bufio_allocated_get_free_pages); 1986 bug = 1; 1987 } 1988 1989 if (dm_bufio_allocated_vmalloc) { 1990 DMCRIT("%s: dm_bufio_vmalloc leaked: %lu", 1991 __func__, dm_bufio_allocated_vmalloc); 1992 bug = 1; 1993 } 1994 1995 BUG_ON(bug); 1996 } 1997 1998 module_init(dm_bufio_init) 1999 module_exit(dm_bufio_exit) 2000 2001 module_param_named(max_cache_size_bytes, dm_bufio_cache_size, ulong, S_IRUGO | S_IWUSR); 2002 MODULE_PARM_DESC(max_cache_size_bytes, "Size of metadata cache"); 2003 2004 module_param_named(max_age_seconds, dm_bufio_max_age, uint, S_IRUGO | S_IWUSR); 2005 MODULE_PARM_DESC(max_age_seconds, "Max age of a buffer in seconds"); 2006 2007 module_param_named(retain_bytes, dm_bufio_retain_bytes, ulong, S_IRUGO | S_IWUSR); 2008 MODULE_PARM_DESC(retain_bytes, "Try to keep at least this many bytes cached in memory"); 2009 2010 module_param_named(peak_allocated_bytes, dm_bufio_peak_allocated, ulong, S_IRUGO | S_IWUSR); 2011 MODULE_PARM_DESC(peak_allocated_bytes, "Tracks the maximum allocated memory"); 2012 2013 module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, S_IRUGO); 2014 MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc"); 2015 2016 module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, S_IRUGO); 2017 MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages"); 2018 2019 module_param_named(allocated_vmalloc_bytes, dm_bufio_allocated_vmalloc, ulong, S_IRUGO); 2020 MODULE_PARM_DESC(allocated_vmalloc_bytes, "Memory allocated with vmalloc"); 2021 2022 module_param_named(current_allocated_bytes, dm_bufio_current_allocated, ulong, S_IRUGO); 2023 MODULE_PARM_DESC(current_allocated_bytes, "Memory currently used by the cache"); 2024 2025 MODULE_AUTHOR("Mikulas Patocka <dm-devel@redhat.com>"); 2026 MODULE_DESCRIPTION(DM_NAME " buffered I/O library"); 2027 MODULE_LICENSE("GPL"); 2028