1 /* 2 * Functions related to setting various queue properties from drivers 3 */ 4 #include <linux/kernel.h> 5 #include <linux/module.h> 6 #include <linux/init.h> 7 #include <linux/bio.h> 8 #include <linux/blkdev.h> 9 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */ 10 #include <linux/gcd.h> 11 #include <linux/lcm.h> 12 #include <linux/jiffies.h> 13 #include <linux/gfp.h> 14 15 #include "blk.h" 16 17 unsigned long blk_max_low_pfn; 18 EXPORT_SYMBOL(blk_max_low_pfn); 19 20 unsigned long blk_max_pfn; 21 22 /** 23 * blk_queue_prep_rq - set a prepare_request function for queue 24 * @q: queue 25 * @pfn: prepare_request function 26 * 27 * It's possible for a queue to register a prepare_request callback which 28 * is invoked before the request is handed to the request_fn. The goal of 29 * the function is to prepare a request for I/O, it can be used to build a 30 * cdb from the request data for instance. 31 * 32 */ 33 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn) 34 { 35 q->prep_rq_fn = pfn; 36 } 37 EXPORT_SYMBOL(blk_queue_prep_rq); 38 39 /** 40 * blk_queue_unprep_rq - set an unprepare_request function for queue 41 * @q: queue 42 * @ufn: unprepare_request function 43 * 44 * It's possible for a queue to register an unprepare_request callback 45 * which is invoked before the request is finally completed. The goal 46 * of the function is to deallocate any data that was allocated in the 47 * prepare_request callback. 48 * 49 */ 50 void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn) 51 { 52 q->unprep_rq_fn = ufn; 53 } 54 EXPORT_SYMBOL(blk_queue_unprep_rq); 55 56 /** 57 * blk_queue_merge_bvec - set a merge_bvec function for queue 58 * @q: queue 59 * @mbfn: merge_bvec_fn 60 * 61 * Usually queues have static limitations on the max sectors or segments that 62 * we can put in a request. Stacking drivers may have some settings that 63 * are dynamic, and thus we have to query the queue whether it is ok to 64 * add a new bio_vec to a bio at a given offset or not. If the block device 65 * has such limitations, it needs to register a merge_bvec_fn to control 66 * the size of bio's sent to it. Note that a block device *must* allow a 67 * single page to be added to an empty bio. The block device driver may want 68 * to use the bio_split() function to deal with these bio's. By default 69 * no merge_bvec_fn is defined for a queue, and only the fixed limits are 70 * honored. 71 */ 72 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn) 73 { 74 q->merge_bvec_fn = mbfn; 75 } 76 EXPORT_SYMBOL(blk_queue_merge_bvec); 77 78 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn) 79 { 80 q->softirq_done_fn = fn; 81 } 82 EXPORT_SYMBOL(blk_queue_softirq_done); 83 84 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout) 85 { 86 q->rq_timeout = timeout; 87 } 88 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout); 89 90 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn) 91 { 92 q->rq_timed_out_fn = fn; 93 } 94 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out); 95 96 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn) 97 { 98 q->lld_busy_fn = fn; 99 } 100 EXPORT_SYMBOL_GPL(blk_queue_lld_busy); 101 102 /** 103 * blk_set_default_limits - reset limits to default values 104 * @lim: the queue_limits structure to reset 105 * 106 * Description: 107 * Returns a queue_limit struct to its default state. Can be used by 108 * stacking drivers like DM that stage table swaps and reuse an 109 * existing device queue. 110 */ 111 void blk_set_default_limits(struct queue_limits *lim) 112 { 113 lim->max_segments = BLK_MAX_SEGMENTS; 114 lim->max_integrity_segments = 0; 115 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK; 116 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE; 117 lim->max_sectors = BLK_DEF_MAX_SECTORS; 118 lim->max_hw_sectors = INT_MAX; 119 lim->max_discard_sectors = 0; 120 lim->discard_granularity = 0; 121 lim->discard_alignment = 0; 122 lim->discard_misaligned = 0; 123 lim->discard_zeroes_data = -1; 124 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512; 125 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT); 126 lim->alignment_offset = 0; 127 lim->io_opt = 0; 128 lim->misaligned = 0; 129 lim->cluster = 1; 130 } 131 EXPORT_SYMBOL(blk_set_default_limits); 132 133 /** 134 * blk_queue_make_request - define an alternate make_request function for a device 135 * @q: the request queue for the device to be affected 136 * @mfn: the alternate make_request function 137 * 138 * Description: 139 * The normal way for &struct bios to be passed to a device 140 * driver is for them to be collected into requests on a request 141 * queue, and then to allow the device driver to select requests 142 * off that queue when it is ready. This works well for many block 143 * devices. However some block devices (typically virtual devices 144 * such as md or lvm) do not benefit from the processing on the 145 * request queue, and are served best by having the requests passed 146 * directly to them. This can be achieved by providing a function 147 * to blk_queue_make_request(). 148 * 149 * Caveat: 150 * The driver that does this *must* be able to deal appropriately 151 * with buffers in "highmemory". This can be accomplished by either calling 152 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling 153 * blk_queue_bounce() to create a buffer in normal memory. 154 **/ 155 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 156 { 157 /* 158 * set defaults 159 */ 160 q->nr_requests = BLKDEV_MAX_RQ; 161 162 q->make_request_fn = mfn; 163 blk_queue_dma_alignment(q, 511); 164 blk_queue_congestion_threshold(q); 165 q->nr_batching = BLK_BATCH_REQ; 166 167 q->unplug_thresh = 4; /* hmm */ 168 q->unplug_delay = msecs_to_jiffies(3); /* 3 milliseconds */ 169 if (q->unplug_delay == 0) 170 q->unplug_delay = 1; 171 172 q->unplug_timer.function = blk_unplug_timeout; 173 q->unplug_timer.data = (unsigned long)q; 174 175 blk_set_default_limits(&q->limits); 176 blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS); 177 178 /* 179 * If the caller didn't supply a lock, fall back to our embedded 180 * per-queue locks 181 */ 182 if (!q->queue_lock) 183 q->queue_lock = &q->__queue_lock; 184 185 /* 186 * by default assume old behaviour and bounce for any highmem page 187 */ 188 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH); 189 } 190 EXPORT_SYMBOL(blk_queue_make_request); 191 192 /** 193 * blk_queue_bounce_limit - set bounce buffer limit for queue 194 * @q: the request queue for the device 195 * @dma_mask: the maximum address the device can handle 196 * 197 * Description: 198 * Different hardware can have different requirements as to what pages 199 * it can do I/O directly to. A low level driver can call 200 * blk_queue_bounce_limit to have lower memory pages allocated as bounce 201 * buffers for doing I/O to pages residing above @dma_mask. 202 **/ 203 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask) 204 { 205 unsigned long b_pfn = dma_mask >> PAGE_SHIFT; 206 int dma = 0; 207 208 q->bounce_gfp = GFP_NOIO; 209 #if BITS_PER_LONG == 64 210 /* 211 * Assume anything <= 4GB can be handled by IOMMU. Actually 212 * some IOMMUs can handle everything, but I don't know of a 213 * way to test this here. 214 */ 215 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) 216 dma = 1; 217 q->limits.bounce_pfn = max(max_low_pfn, b_pfn); 218 #else 219 if (b_pfn < blk_max_low_pfn) 220 dma = 1; 221 q->limits.bounce_pfn = b_pfn; 222 #endif 223 if (dma) { 224 init_emergency_isa_pool(); 225 q->bounce_gfp = GFP_NOIO | GFP_DMA; 226 q->limits.bounce_pfn = b_pfn; 227 } 228 } 229 EXPORT_SYMBOL(blk_queue_bounce_limit); 230 231 /** 232 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request 233 * @limits: the queue limits 234 * @max_hw_sectors: max hardware sectors in the usual 512b unit 235 * 236 * Description: 237 * Enables a low level driver to set a hard upper limit, 238 * max_hw_sectors, on the size of requests. max_hw_sectors is set by 239 * the device driver based upon the combined capabilities of I/O 240 * controller and storage device. 241 * 242 * max_sectors is a soft limit imposed by the block layer for 243 * filesystem type requests. This value can be overridden on a 244 * per-device basis in /sys/block/<device>/queue/max_sectors_kb. 245 * The soft limit can not exceed max_hw_sectors. 246 **/ 247 void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors) 248 { 249 if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) { 250 max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9); 251 printk(KERN_INFO "%s: set to minimum %d\n", 252 __func__, max_hw_sectors); 253 } 254 255 limits->max_hw_sectors = max_hw_sectors; 256 limits->max_sectors = min_t(unsigned int, max_hw_sectors, 257 BLK_DEF_MAX_SECTORS); 258 } 259 EXPORT_SYMBOL(blk_limits_max_hw_sectors); 260 261 /** 262 * blk_queue_max_hw_sectors - set max sectors for a request for this queue 263 * @q: the request queue for the device 264 * @max_hw_sectors: max hardware sectors in the usual 512b unit 265 * 266 * Description: 267 * See description for blk_limits_max_hw_sectors(). 268 **/ 269 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors) 270 { 271 blk_limits_max_hw_sectors(&q->limits, max_hw_sectors); 272 } 273 EXPORT_SYMBOL(blk_queue_max_hw_sectors); 274 275 /** 276 * blk_queue_max_discard_sectors - set max sectors for a single discard 277 * @q: the request queue for the device 278 * @max_discard_sectors: maximum number of sectors to discard 279 **/ 280 void blk_queue_max_discard_sectors(struct request_queue *q, 281 unsigned int max_discard_sectors) 282 { 283 q->limits.max_discard_sectors = max_discard_sectors; 284 } 285 EXPORT_SYMBOL(blk_queue_max_discard_sectors); 286 287 /** 288 * blk_queue_max_segments - set max hw segments for a request for this queue 289 * @q: the request queue for the device 290 * @max_segments: max number of segments 291 * 292 * Description: 293 * Enables a low level driver to set an upper limit on the number of 294 * hw data segments in a request. 295 **/ 296 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments) 297 { 298 if (!max_segments) { 299 max_segments = 1; 300 printk(KERN_INFO "%s: set to minimum %d\n", 301 __func__, max_segments); 302 } 303 304 q->limits.max_segments = max_segments; 305 } 306 EXPORT_SYMBOL(blk_queue_max_segments); 307 308 /** 309 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg 310 * @q: the request queue for the device 311 * @max_size: max size of segment in bytes 312 * 313 * Description: 314 * Enables a low level driver to set an upper limit on the size of a 315 * coalesced segment 316 **/ 317 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) 318 { 319 if (max_size < PAGE_CACHE_SIZE) { 320 max_size = PAGE_CACHE_SIZE; 321 printk(KERN_INFO "%s: set to minimum %d\n", 322 __func__, max_size); 323 } 324 325 q->limits.max_segment_size = max_size; 326 } 327 EXPORT_SYMBOL(blk_queue_max_segment_size); 328 329 /** 330 * blk_queue_logical_block_size - set logical block size for the queue 331 * @q: the request queue for the device 332 * @size: the logical block size, in bytes 333 * 334 * Description: 335 * This should be set to the lowest possible block size that the 336 * storage device can address. The default of 512 covers most 337 * hardware. 338 **/ 339 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size) 340 { 341 q->limits.logical_block_size = size; 342 343 if (q->limits.physical_block_size < size) 344 q->limits.physical_block_size = size; 345 346 if (q->limits.io_min < q->limits.physical_block_size) 347 q->limits.io_min = q->limits.physical_block_size; 348 } 349 EXPORT_SYMBOL(blk_queue_logical_block_size); 350 351 /** 352 * blk_queue_physical_block_size - set physical block size for the queue 353 * @q: the request queue for the device 354 * @size: the physical block size, in bytes 355 * 356 * Description: 357 * This should be set to the lowest possible sector size that the 358 * hardware can operate on without reverting to read-modify-write 359 * operations. 360 */ 361 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size) 362 { 363 q->limits.physical_block_size = size; 364 365 if (q->limits.physical_block_size < q->limits.logical_block_size) 366 q->limits.physical_block_size = q->limits.logical_block_size; 367 368 if (q->limits.io_min < q->limits.physical_block_size) 369 q->limits.io_min = q->limits.physical_block_size; 370 } 371 EXPORT_SYMBOL(blk_queue_physical_block_size); 372 373 /** 374 * blk_queue_alignment_offset - set physical block alignment offset 375 * @q: the request queue for the device 376 * @offset: alignment offset in bytes 377 * 378 * Description: 379 * Some devices are naturally misaligned to compensate for things like 380 * the legacy DOS partition table 63-sector offset. Low-level drivers 381 * should call this function for devices whose first sector is not 382 * naturally aligned. 383 */ 384 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset) 385 { 386 q->limits.alignment_offset = 387 offset & (q->limits.physical_block_size - 1); 388 q->limits.misaligned = 0; 389 } 390 EXPORT_SYMBOL(blk_queue_alignment_offset); 391 392 /** 393 * blk_limits_io_min - set minimum request size for a device 394 * @limits: the queue limits 395 * @min: smallest I/O size in bytes 396 * 397 * Description: 398 * Some devices have an internal block size bigger than the reported 399 * hardware sector size. This function can be used to signal the 400 * smallest I/O the device can perform without incurring a performance 401 * penalty. 402 */ 403 void blk_limits_io_min(struct queue_limits *limits, unsigned int min) 404 { 405 limits->io_min = min; 406 407 if (limits->io_min < limits->logical_block_size) 408 limits->io_min = limits->logical_block_size; 409 410 if (limits->io_min < limits->physical_block_size) 411 limits->io_min = limits->physical_block_size; 412 } 413 EXPORT_SYMBOL(blk_limits_io_min); 414 415 /** 416 * blk_queue_io_min - set minimum request size for the queue 417 * @q: the request queue for the device 418 * @min: smallest I/O size in bytes 419 * 420 * Description: 421 * Storage devices may report a granularity or preferred minimum I/O 422 * size which is the smallest request the device can perform without 423 * incurring a performance penalty. For disk drives this is often the 424 * physical block size. For RAID arrays it is often the stripe chunk 425 * size. A properly aligned multiple of minimum_io_size is the 426 * preferred request size for workloads where a high number of I/O 427 * operations is desired. 428 */ 429 void blk_queue_io_min(struct request_queue *q, unsigned int min) 430 { 431 blk_limits_io_min(&q->limits, min); 432 } 433 EXPORT_SYMBOL(blk_queue_io_min); 434 435 /** 436 * blk_limits_io_opt - set optimal request size for a device 437 * @limits: the queue limits 438 * @opt: smallest I/O size in bytes 439 * 440 * Description: 441 * Storage devices may report an optimal I/O size, which is the 442 * device's preferred unit for sustained I/O. This is rarely reported 443 * for disk drives. For RAID arrays it is usually the stripe width or 444 * the internal track size. A properly aligned multiple of 445 * optimal_io_size is the preferred request size for workloads where 446 * sustained throughput is desired. 447 */ 448 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt) 449 { 450 limits->io_opt = opt; 451 } 452 EXPORT_SYMBOL(blk_limits_io_opt); 453 454 /** 455 * blk_queue_io_opt - set optimal request size for the queue 456 * @q: the request queue for the device 457 * @opt: optimal request size in bytes 458 * 459 * Description: 460 * Storage devices may report an optimal I/O size, which is the 461 * device's preferred unit for sustained I/O. This is rarely reported 462 * for disk drives. For RAID arrays it is usually the stripe width or 463 * the internal track size. A properly aligned multiple of 464 * optimal_io_size is the preferred request size for workloads where 465 * sustained throughput is desired. 466 */ 467 void blk_queue_io_opt(struct request_queue *q, unsigned int opt) 468 { 469 blk_limits_io_opt(&q->limits, opt); 470 } 471 EXPORT_SYMBOL(blk_queue_io_opt); 472 473 /** 474 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers 475 * @t: the stacking driver (top) 476 * @b: the underlying device (bottom) 477 **/ 478 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) 479 { 480 blk_stack_limits(&t->limits, &b->limits, 0); 481 } 482 EXPORT_SYMBOL(blk_queue_stack_limits); 483 484 /** 485 * blk_stack_limits - adjust queue_limits for stacked devices 486 * @t: the stacking driver limits (top device) 487 * @b: the underlying queue limits (bottom, component device) 488 * @start: first data sector within component device 489 * 490 * Description: 491 * This function is used by stacking drivers like MD and DM to ensure 492 * that all component devices have compatible block sizes and 493 * alignments. The stacking driver must provide a queue_limits 494 * struct (top) and then iteratively call the stacking function for 495 * all component (bottom) devices. The stacking function will 496 * attempt to combine the values and ensure proper alignment. 497 * 498 * Returns 0 if the top and bottom queue_limits are compatible. The 499 * top device's block sizes and alignment offsets may be adjusted to 500 * ensure alignment with the bottom device. If no compatible sizes 501 * and alignments exist, -1 is returned and the resulting top 502 * queue_limits will have the misaligned flag set to indicate that 503 * the alignment_offset is undefined. 504 */ 505 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, 506 sector_t start) 507 { 508 unsigned int top, bottom, alignment, ret = 0; 509 510 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); 511 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); 512 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn); 513 514 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, 515 b->seg_boundary_mask); 516 517 t->max_segments = min_not_zero(t->max_segments, b->max_segments); 518 t->max_integrity_segments = min_not_zero(t->max_integrity_segments, 519 b->max_integrity_segments); 520 521 t->max_segment_size = min_not_zero(t->max_segment_size, 522 b->max_segment_size); 523 524 t->misaligned |= b->misaligned; 525 526 alignment = queue_limit_alignment_offset(b, start); 527 528 /* Bottom device has different alignment. Check that it is 529 * compatible with the current top alignment. 530 */ 531 if (t->alignment_offset != alignment) { 532 533 top = max(t->physical_block_size, t->io_min) 534 + t->alignment_offset; 535 bottom = max(b->physical_block_size, b->io_min) + alignment; 536 537 /* Verify that top and bottom intervals line up */ 538 if (max(top, bottom) & (min(top, bottom) - 1)) { 539 t->misaligned = 1; 540 ret = -1; 541 } 542 } 543 544 t->logical_block_size = max(t->logical_block_size, 545 b->logical_block_size); 546 547 t->physical_block_size = max(t->physical_block_size, 548 b->physical_block_size); 549 550 t->io_min = max(t->io_min, b->io_min); 551 t->io_opt = lcm(t->io_opt, b->io_opt); 552 553 t->cluster &= b->cluster; 554 t->discard_zeroes_data &= b->discard_zeroes_data; 555 556 /* Physical block size a multiple of the logical block size? */ 557 if (t->physical_block_size & (t->logical_block_size - 1)) { 558 t->physical_block_size = t->logical_block_size; 559 t->misaligned = 1; 560 ret = -1; 561 } 562 563 /* Minimum I/O a multiple of the physical block size? */ 564 if (t->io_min & (t->physical_block_size - 1)) { 565 t->io_min = t->physical_block_size; 566 t->misaligned = 1; 567 ret = -1; 568 } 569 570 /* Optimal I/O a multiple of the physical block size? */ 571 if (t->io_opt & (t->physical_block_size - 1)) { 572 t->io_opt = 0; 573 t->misaligned = 1; 574 ret = -1; 575 } 576 577 /* Find lowest common alignment_offset */ 578 t->alignment_offset = lcm(t->alignment_offset, alignment) 579 & (max(t->physical_block_size, t->io_min) - 1); 580 581 /* Verify that new alignment_offset is on a logical block boundary */ 582 if (t->alignment_offset & (t->logical_block_size - 1)) { 583 t->misaligned = 1; 584 ret = -1; 585 } 586 587 /* Discard alignment and granularity */ 588 if (b->discard_granularity) { 589 alignment = queue_limit_discard_alignment(b, start); 590 591 if (t->discard_granularity != 0 && 592 t->discard_alignment != alignment) { 593 top = t->discard_granularity + t->discard_alignment; 594 bottom = b->discard_granularity + alignment; 595 596 /* Verify that top and bottom intervals line up */ 597 if (max(top, bottom) & (min(top, bottom) - 1)) 598 t->discard_misaligned = 1; 599 } 600 601 t->max_discard_sectors = min_not_zero(t->max_discard_sectors, 602 b->max_discard_sectors); 603 t->discard_granularity = max(t->discard_granularity, 604 b->discard_granularity); 605 t->discard_alignment = lcm(t->discard_alignment, alignment) & 606 (t->discard_granularity - 1); 607 } 608 609 return ret; 610 } 611 EXPORT_SYMBOL(blk_stack_limits); 612 613 /** 614 * bdev_stack_limits - adjust queue limits for stacked drivers 615 * @t: the stacking driver limits (top device) 616 * @bdev: the component block_device (bottom) 617 * @start: first data sector within component device 618 * 619 * Description: 620 * Merges queue limits for a top device and a block_device. Returns 621 * 0 if alignment didn't change. Returns -1 if adding the bottom 622 * device caused misalignment. 623 */ 624 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev, 625 sector_t start) 626 { 627 struct request_queue *bq = bdev_get_queue(bdev); 628 629 start += get_start_sect(bdev); 630 631 return blk_stack_limits(t, &bq->limits, start); 632 } 633 EXPORT_SYMBOL(bdev_stack_limits); 634 635 /** 636 * disk_stack_limits - adjust queue limits for stacked drivers 637 * @disk: MD/DM gendisk (top) 638 * @bdev: the underlying block device (bottom) 639 * @offset: offset to beginning of data within component device 640 * 641 * Description: 642 * Merges the limits for a top level gendisk and a bottom level 643 * block_device. 644 */ 645 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev, 646 sector_t offset) 647 { 648 struct request_queue *t = disk->queue; 649 650 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) { 651 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE]; 652 653 disk_name(disk, 0, top); 654 bdevname(bdev, bottom); 655 656 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n", 657 top, bottom); 658 } 659 } 660 EXPORT_SYMBOL(disk_stack_limits); 661 662 /** 663 * blk_queue_dma_pad - set pad mask 664 * @q: the request queue for the device 665 * @mask: pad mask 666 * 667 * Set dma pad mask. 668 * 669 * Appending pad buffer to a request modifies the last entry of a 670 * scatter list such that it includes the pad buffer. 671 **/ 672 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask) 673 { 674 q->dma_pad_mask = mask; 675 } 676 EXPORT_SYMBOL(blk_queue_dma_pad); 677 678 /** 679 * blk_queue_update_dma_pad - update pad mask 680 * @q: the request queue for the device 681 * @mask: pad mask 682 * 683 * Update dma pad mask. 684 * 685 * Appending pad buffer to a request modifies the last entry of a 686 * scatter list such that it includes the pad buffer. 687 **/ 688 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask) 689 { 690 if (mask > q->dma_pad_mask) 691 q->dma_pad_mask = mask; 692 } 693 EXPORT_SYMBOL(blk_queue_update_dma_pad); 694 695 /** 696 * blk_queue_dma_drain - Set up a drain buffer for excess dma. 697 * @q: the request queue for the device 698 * @dma_drain_needed: fn which returns non-zero if drain is necessary 699 * @buf: physically contiguous buffer 700 * @size: size of the buffer in bytes 701 * 702 * Some devices have excess DMA problems and can't simply discard (or 703 * zero fill) the unwanted piece of the transfer. They have to have a 704 * real area of memory to transfer it into. The use case for this is 705 * ATAPI devices in DMA mode. If the packet command causes a transfer 706 * bigger than the transfer size some HBAs will lock up if there 707 * aren't DMA elements to contain the excess transfer. What this API 708 * does is adjust the queue so that the buf is always appended 709 * silently to the scatterlist. 710 * 711 * Note: This routine adjusts max_hw_segments to make room for appending 712 * the drain buffer. If you call blk_queue_max_segments() after calling 713 * this routine, you must set the limit to one fewer than your device 714 * can support otherwise there won't be room for the drain buffer. 715 */ 716 int blk_queue_dma_drain(struct request_queue *q, 717 dma_drain_needed_fn *dma_drain_needed, 718 void *buf, unsigned int size) 719 { 720 if (queue_max_segments(q) < 2) 721 return -EINVAL; 722 /* make room for appending the drain */ 723 blk_queue_max_segments(q, queue_max_segments(q) - 1); 724 q->dma_drain_needed = dma_drain_needed; 725 q->dma_drain_buffer = buf; 726 q->dma_drain_size = size; 727 728 return 0; 729 } 730 EXPORT_SYMBOL_GPL(blk_queue_dma_drain); 731 732 /** 733 * blk_queue_segment_boundary - set boundary rules for segment merging 734 * @q: the request queue for the device 735 * @mask: the memory boundary mask 736 **/ 737 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask) 738 { 739 if (mask < PAGE_CACHE_SIZE - 1) { 740 mask = PAGE_CACHE_SIZE - 1; 741 printk(KERN_INFO "%s: set to minimum %lx\n", 742 __func__, mask); 743 } 744 745 q->limits.seg_boundary_mask = mask; 746 } 747 EXPORT_SYMBOL(blk_queue_segment_boundary); 748 749 /** 750 * blk_queue_dma_alignment - set dma length and memory alignment 751 * @q: the request queue for the device 752 * @mask: alignment mask 753 * 754 * description: 755 * set required memory and length alignment for direct dma transactions. 756 * this is used when building direct io requests for the queue. 757 * 758 **/ 759 void blk_queue_dma_alignment(struct request_queue *q, int mask) 760 { 761 q->dma_alignment = mask; 762 } 763 EXPORT_SYMBOL(blk_queue_dma_alignment); 764 765 /** 766 * blk_queue_update_dma_alignment - update dma length and memory alignment 767 * @q: the request queue for the device 768 * @mask: alignment mask 769 * 770 * description: 771 * update required memory and length alignment for direct dma transactions. 772 * If the requested alignment is larger than the current alignment, then 773 * the current queue alignment is updated to the new value, otherwise it 774 * is left alone. The design of this is to allow multiple objects 775 * (driver, device, transport etc) to set their respective 776 * alignments without having them interfere. 777 * 778 **/ 779 void blk_queue_update_dma_alignment(struct request_queue *q, int mask) 780 { 781 BUG_ON(mask > PAGE_SIZE); 782 783 if (mask > q->dma_alignment) 784 q->dma_alignment = mask; 785 } 786 EXPORT_SYMBOL(blk_queue_update_dma_alignment); 787 788 /** 789 * blk_queue_flush - configure queue's cache flush capability 790 * @q: the request queue for the device 791 * @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA 792 * 793 * Tell block layer cache flush capability of @q. If it supports 794 * flushing, REQ_FLUSH should be set. If it supports bypassing 795 * write cache for individual writes, REQ_FUA should be set. 796 */ 797 void blk_queue_flush(struct request_queue *q, unsigned int flush) 798 { 799 WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA)); 800 801 if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA))) 802 flush &= ~REQ_FUA; 803 804 q->flush_flags = flush & (REQ_FLUSH | REQ_FUA); 805 } 806 EXPORT_SYMBOL_GPL(blk_queue_flush); 807 808 static int __init blk_settings_init(void) 809 { 810 blk_max_low_pfn = max_low_pfn - 1; 811 blk_max_pfn = max_pfn - 1; 812 return 0; 813 } 814 subsys_initcall(blk_settings_init); 815