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. 108 */ 109 void blk_set_default_limits(struct queue_limits *lim) 110 { 111 lim->max_segments = BLK_MAX_SEGMENTS; 112 lim->max_integrity_segments = 0; 113 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK; 114 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE; 115 lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS; 116 lim->max_discard_sectors = 0; 117 lim->discard_granularity = 0; 118 lim->discard_alignment = 0; 119 lim->discard_misaligned = 0; 120 lim->discard_zeroes_data = 0; 121 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512; 122 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT); 123 lim->alignment_offset = 0; 124 lim->io_opt = 0; 125 lim->misaligned = 0; 126 lim->cluster = 1; 127 } 128 EXPORT_SYMBOL(blk_set_default_limits); 129 130 /** 131 * blk_set_stacking_limits - set default limits for stacking devices 132 * @lim: the queue_limits structure to reset 133 * 134 * Description: 135 * Returns a queue_limit struct to its default state. Should be used 136 * by stacking drivers like DM that have no internal limits. 137 */ 138 void blk_set_stacking_limits(struct queue_limits *lim) 139 { 140 blk_set_default_limits(lim); 141 142 /* Inherit limits from component devices */ 143 lim->discard_zeroes_data = 1; 144 lim->max_segments = USHRT_MAX; 145 lim->max_hw_sectors = UINT_MAX; 146 147 lim->max_sectors = BLK_DEF_MAX_SECTORS; 148 } 149 EXPORT_SYMBOL(blk_set_stacking_limits); 150 151 /** 152 * blk_queue_make_request - define an alternate make_request function for a device 153 * @q: the request queue for the device to be affected 154 * @mfn: the alternate make_request function 155 * 156 * Description: 157 * The normal way for &struct bios to be passed to a device 158 * driver is for them to be collected into requests on a request 159 * queue, and then to allow the device driver to select requests 160 * off that queue when it is ready. This works well for many block 161 * devices. However some block devices (typically virtual devices 162 * such as md or lvm) do not benefit from the processing on the 163 * request queue, and are served best by having the requests passed 164 * directly to them. This can be achieved by providing a function 165 * to blk_queue_make_request(). 166 * 167 * Caveat: 168 * The driver that does this *must* be able to deal appropriately 169 * with buffers in "highmemory". This can be accomplished by either calling 170 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling 171 * blk_queue_bounce() to create a buffer in normal memory. 172 **/ 173 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn) 174 { 175 /* 176 * set defaults 177 */ 178 q->nr_requests = BLKDEV_MAX_RQ; 179 180 q->make_request_fn = mfn; 181 blk_queue_dma_alignment(q, 511); 182 blk_queue_congestion_threshold(q); 183 q->nr_batching = BLK_BATCH_REQ; 184 185 blk_set_default_limits(&q->limits); 186 187 /* 188 * by default assume old behaviour and bounce for any highmem page 189 */ 190 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH); 191 } 192 EXPORT_SYMBOL(blk_queue_make_request); 193 194 /** 195 * blk_queue_bounce_limit - set bounce buffer limit for queue 196 * @q: the request queue for the device 197 * @dma_mask: the maximum address the device can handle 198 * 199 * Description: 200 * Different hardware can have different requirements as to what pages 201 * it can do I/O directly to. A low level driver can call 202 * blk_queue_bounce_limit to have lower memory pages allocated as bounce 203 * buffers for doing I/O to pages residing above @dma_mask. 204 **/ 205 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask) 206 { 207 unsigned long b_pfn = dma_mask >> PAGE_SHIFT; 208 int dma = 0; 209 210 q->bounce_gfp = GFP_NOIO; 211 #if BITS_PER_LONG == 64 212 /* 213 * Assume anything <= 4GB can be handled by IOMMU. Actually 214 * some IOMMUs can handle everything, but I don't know of a 215 * way to test this here. 216 */ 217 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT)) 218 dma = 1; 219 q->limits.bounce_pfn = max(max_low_pfn, b_pfn); 220 #else 221 if (b_pfn < blk_max_low_pfn) 222 dma = 1; 223 q->limits.bounce_pfn = b_pfn; 224 #endif 225 if (dma) { 226 init_emergency_isa_pool(); 227 q->bounce_gfp = GFP_NOIO | GFP_DMA; 228 q->limits.bounce_pfn = b_pfn; 229 } 230 } 231 EXPORT_SYMBOL(blk_queue_bounce_limit); 232 233 /** 234 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request 235 * @limits: the queue limits 236 * @max_hw_sectors: max hardware sectors in the usual 512b unit 237 * 238 * Description: 239 * Enables a low level driver to set a hard upper limit, 240 * max_hw_sectors, on the size of requests. max_hw_sectors is set by 241 * the device driver based upon the combined capabilities of I/O 242 * controller and storage device. 243 * 244 * max_sectors is a soft limit imposed by the block layer for 245 * filesystem type requests. This value can be overridden on a 246 * per-device basis in /sys/block/<device>/queue/max_sectors_kb. 247 * The soft limit can not exceed max_hw_sectors. 248 **/ 249 void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors) 250 { 251 if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) { 252 max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9); 253 printk(KERN_INFO "%s: set to minimum %d\n", 254 __func__, max_hw_sectors); 255 } 256 257 limits->max_hw_sectors = max_hw_sectors; 258 limits->max_sectors = min_t(unsigned int, max_hw_sectors, 259 BLK_DEF_MAX_SECTORS); 260 } 261 EXPORT_SYMBOL(blk_limits_max_hw_sectors); 262 263 /** 264 * blk_queue_max_hw_sectors - set max sectors for a request for this queue 265 * @q: the request queue for the device 266 * @max_hw_sectors: max hardware sectors in the usual 512b unit 267 * 268 * Description: 269 * See description for blk_limits_max_hw_sectors(). 270 **/ 271 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors) 272 { 273 blk_limits_max_hw_sectors(&q->limits, max_hw_sectors); 274 } 275 EXPORT_SYMBOL(blk_queue_max_hw_sectors); 276 277 /** 278 * blk_queue_max_discard_sectors - set max sectors for a single discard 279 * @q: the request queue for the device 280 * @max_discard_sectors: maximum number of sectors to discard 281 **/ 282 void blk_queue_max_discard_sectors(struct request_queue *q, 283 unsigned int max_discard_sectors) 284 { 285 q->limits.max_discard_sectors = max_discard_sectors; 286 } 287 EXPORT_SYMBOL(blk_queue_max_discard_sectors); 288 289 /** 290 * blk_queue_max_segments - set max hw segments for a request for this queue 291 * @q: the request queue for the device 292 * @max_segments: max number of segments 293 * 294 * Description: 295 * Enables a low level driver to set an upper limit on the number of 296 * hw data segments in a request. 297 **/ 298 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments) 299 { 300 if (!max_segments) { 301 max_segments = 1; 302 printk(KERN_INFO "%s: set to minimum %d\n", 303 __func__, max_segments); 304 } 305 306 q->limits.max_segments = max_segments; 307 } 308 EXPORT_SYMBOL(blk_queue_max_segments); 309 310 /** 311 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg 312 * @q: the request queue for the device 313 * @max_size: max size of segment in bytes 314 * 315 * Description: 316 * Enables a low level driver to set an upper limit on the size of a 317 * coalesced segment 318 **/ 319 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size) 320 { 321 if (max_size < PAGE_CACHE_SIZE) { 322 max_size = PAGE_CACHE_SIZE; 323 printk(KERN_INFO "%s: set to minimum %d\n", 324 __func__, max_size); 325 } 326 327 q->limits.max_segment_size = max_size; 328 } 329 EXPORT_SYMBOL(blk_queue_max_segment_size); 330 331 /** 332 * blk_queue_logical_block_size - set logical block size for the queue 333 * @q: the request queue for the device 334 * @size: the logical block size, in bytes 335 * 336 * Description: 337 * This should be set to the lowest possible block size that the 338 * storage device can address. The default of 512 covers most 339 * hardware. 340 **/ 341 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size) 342 { 343 q->limits.logical_block_size = size; 344 345 if (q->limits.physical_block_size < size) 346 q->limits.physical_block_size = size; 347 348 if (q->limits.io_min < q->limits.physical_block_size) 349 q->limits.io_min = q->limits.physical_block_size; 350 } 351 EXPORT_SYMBOL(blk_queue_logical_block_size); 352 353 /** 354 * blk_queue_physical_block_size - set physical block size for the queue 355 * @q: the request queue for the device 356 * @size: the physical block size, in bytes 357 * 358 * Description: 359 * This should be set to the lowest possible sector size that the 360 * hardware can operate on without reverting to read-modify-write 361 * operations. 362 */ 363 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size) 364 { 365 q->limits.physical_block_size = size; 366 367 if (q->limits.physical_block_size < q->limits.logical_block_size) 368 q->limits.physical_block_size = q->limits.logical_block_size; 369 370 if (q->limits.io_min < q->limits.physical_block_size) 371 q->limits.io_min = q->limits.physical_block_size; 372 } 373 EXPORT_SYMBOL(blk_queue_physical_block_size); 374 375 /** 376 * blk_queue_alignment_offset - set physical block alignment offset 377 * @q: the request queue for the device 378 * @offset: alignment offset in bytes 379 * 380 * Description: 381 * Some devices are naturally misaligned to compensate for things like 382 * the legacy DOS partition table 63-sector offset. Low-level drivers 383 * should call this function for devices whose first sector is not 384 * naturally aligned. 385 */ 386 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset) 387 { 388 q->limits.alignment_offset = 389 offset & (q->limits.physical_block_size - 1); 390 q->limits.misaligned = 0; 391 } 392 EXPORT_SYMBOL(blk_queue_alignment_offset); 393 394 /** 395 * blk_limits_io_min - set minimum request size for a device 396 * @limits: the queue limits 397 * @min: smallest I/O size in bytes 398 * 399 * Description: 400 * Some devices have an internal block size bigger than the reported 401 * hardware sector size. This function can be used to signal the 402 * smallest I/O the device can perform without incurring a performance 403 * penalty. 404 */ 405 void blk_limits_io_min(struct queue_limits *limits, unsigned int min) 406 { 407 limits->io_min = min; 408 409 if (limits->io_min < limits->logical_block_size) 410 limits->io_min = limits->logical_block_size; 411 412 if (limits->io_min < limits->physical_block_size) 413 limits->io_min = limits->physical_block_size; 414 } 415 EXPORT_SYMBOL(blk_limits_io_min); 416 417 /** 418 * blk_queue_io_min - set minimum request size for the queue 419 * @q: the request queue for the device 420 * @min: smallest I/O size in bytes 421 * 422 * Description: 423 * Storage devices may report a granularity or preferred minimum I/O 424 * size which is the smallest request the device can perform without 425 * incurring a performance penalty. For disk drives this is often the 426 * physical block size. For RAID arrays it is often the stripe chunk 427 * size. A properly aligned multiple of minimum_io_size is the 428 * preferred request size for workloads where a high number of I/O 429 * operations is desired. 430 */ 431 void blk_queue_io_min(struct request_queue *q, unsigned int min) 432 { 433 blk_limits_io_min(&q->limits, min); 434 } 435 EXPORT_SYMBOL(blk_queue_io_min); 436 437 /** 438 * blk_limits_io_opt - set optimal request size for a device 439 * @limits: the queue limits 440 * @opt: smallest I/O size in bytes 441 * 442 * Description: 443 * Storage devices may report an optimal I/O size, which is the 444 * device's preferred unit for sustained I/O. This is rarely reported 445 * for disk drives. For RAID arrays it is usually the stripe width or 446 * the internal track size. A properly aligned multiple of 447 * optimal_io_size is the preferred request size for workloads where 448 * sustained throughput is desired. 449 */ 450 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt) 451 { 452 limits->io_opt = opt; 453 } 454 EXPORT_SYMBOL(blk_limits_io_opt); 455 456 /** 457 * blk_queue_io_opt - set optimal request size for the queue 458 * @q: the request queue for the device 459 * @opt: optimal request size in bytes 460 * 461 * Description: 462 * Storage devices may report an optimal I/O size, which is the 463 * device's preferred unit for sustained I/O. This is rarely reported 464 * for disk drives. For RAID arrays it is usually the stripe width or 465 * the internal track size. A properly aligned multiple of 466 * optimal_io_size is the preferred request size for workloads where 467 * sustained throughput is desired. 468 */ 469 void blk_queue_io_opt(struct request_queue *q, unsigned int opt) 470 { 471 blk_limits_io_opt(&q->limits, opt); 472 } 473 EXPORT_SYMBOL(blk_queue_io_opt); 474 475 /** 476 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers 477 * @t: the stacking driver (top) 478 * @b: the underlying device (bottom) 479 **/ 480 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b) 481 { 482 blk_stack_limits(&t->limits, &b->limits, 0); 483 } 484 EXPORT_SYMBOL(blk_queue_stack_limits); 485 486 /** 487 * blk_stack_limits - adjust queue_limits for stacked devices 488 * @t: the stacking driver limits (top device) 489 * @b: the underlying queue limits (bottom, component device) 490 * @start: first data sector within component device 491 * 492 * Description: 493 * This function is used by stacking drivers like MD and DM to ensure 494 * that all component devices have compatible block sizes and 495 * alignments. The stacking driver must provide a queue_limits 496 * struct (top) and then iteratively call the stacking function for 497 * all component (bottom) devices. The stacking function will 498 * attempt to combine the values and ensure proper alignment. 499 * 500 * Returns 0 if the top and bottom queue_limits are compatible. The 501 * top device's block sizes and alignment offsets may be adjusted to 502 * ensure alignment with the bottom device. If no compatible sizes 503 * and alignments exist, -1 is returned and the resulting top 504 * queue_limits will have the misaligned flag set to indicate that 505 * the alignment_offset is undefined. 506 */ 507 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b, 508 sector_t start) 509 { 510 unsigned int top, bottom, alignment, ret = 0; 511 512 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors); 513 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors); 514 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn); 515 516 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, 517 b->seg_boundary_mask); 518 519 t->max_segments = min_not_zero(t->max_segments, b->max_segments); 520 t->max_integrity_segments = min_not_zero(t->max_integrity_segments, 521 b->max_integrity_segments); 522 523 t->max_segment_size = min_not_zero(t->max_segment_size, 524 b->max_segment_size); 525 526 t->misaligned |= b->misaligned; 527 528 alignment = queue_limit_alignment_offset(b, start); 529 530 /* Bottom device has different alignment. Check that it is 531 * compatible with the current top alignment. 532 */ 533 if (t->alignment_offset != alignment) { 534 535 top = max(t->physical_block_size, t->io_min) 536 + t->alignment_offset; 537 bottom = max(b->physical_block_size, b->io_min) + alignment; 538 539 /* Verify that top and bottom intervals line up */ 540 if (max(top, bottom) & (min(top, bottom) - 1)) { 541 t->misaligned = 1; 542 ret = -1; 543 } 544 } 545 546 t->logical_block_size = max(t->logical_block_size, 547 b->logical_block_size); 548 549 t->physical_block_size = max(t->physical_block_size, 550 b->physical_block_size); 551 552 t->io_min = max(t->io_min, b->io_min); 553 t->io_opt = lcm(t->io_opt, b->io_opt); 554 555 t->cluster &= b->cluster; 556 t->discard_zeroes_data &= b->discard_zeroes_data; 557 558 /* Physical block size a multiple of the logical block size? */ 559 if (t->physical_block_size & (t->logical_block_size - 1)) { 560 t->physical_block_size = t->logical_block_size; 561 t->misaligned = 1; 562 ret = -1; 563 } 564 565 /* Minimum I/O a multiple of the physical block size? */ 566 if (t->io_min & (t->physical_block_size - 1)) { 567 t->io_min = t->physical_block_size; 568 t->misaligned = 1; 569 ret = -1; 570 } 571 572 /* Optimal I/O a multiple of the physical block size? */ 573 if (t->io_opt & (t->physical_block_size - 1)) { 574 t->io_opt = 0; 575 t->misaligned = 1; 576 ret = -1; 577 } 578 579 /* Find lowest common alignment_offset */ 580 t->alignment_offset = lcm(t->alignment_offset, alignment) 581 & (max(t->physical_block_size, t->io_min) - 1); 582 583 /* Verify that new alignment_offset is on a logical block boundary */ 584 if (t->alignment_offset & (t->logical_block_size - 1)) { 585 t->misaligned = 1; 586 ret = -1; 587 } 588 589 /* Discard alignment and granularity */ 590 if (b->discard_granularity) { 591 alignment = queue_limit_discard_alignment(b, start); 592 593 if (t->discard_granularity != 0 && 594 t->discard_alignment != alignment) { 595 top = t->discard_granularity + t->discard_alignment; 596 bottom = b->discard_granularity + alignment; 597 598 /* Verify that top and bottom intervals line up */ 599 if (max(top, bottom) & (min(top, bottom) - 1)) 600 t->discard_misaligned = 1; 601 } 602 603 t->max_discard_sectors = min_not_zero(t->max_discard_sectors, 604 b->max_discard_sectors); 605 t->discard_granularity = max(t->discard_granularity, 606 b->discard_granularity); 607 t->discard_alignment = lcm(t->discard_alignment, alignment) & 608 (t->discard_granularity - 1); 609 } 610 611 return ret; 612 } 613 EXPORT_SYMBOL(blk_stack_limits); 614 615 /** 616 * bdev_stack_limits - adjust queue limits for stacked drivers 617 * @t: the stacking driver limits (top device) 618 * @bdev: the component block_device (bottom) 619 * @start: first data sector within component device 620 * 621 * Description: 622 * Merges queue limits for a top device and a block_device. Returns 623 * 0 if alignment didn't change. Returns -1 if adding the bottom 624 * device caused misalignment. 625 */ 626 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev, 627 sector_t start) 628 { 629 struct request_queue *bq = bdev_get_queue(bdev); 630 631 start += get_start_sect(bdev); 632 633 return blk_stack_limits(t, &bq->limits, start); 634 } 635 EXPORT_SYMBOL(bdev_stack_limits); 636 637 /** 638 * disk_stack_limits - adjust queue limits for stacked drivers 639 * @disk: MD/DM gendisk (top) 640 * @bdev: the underlying block device (bottom) 641 * @offset: offset to beginning of data within component device 642 * 643 * Description: 644 * Merges the limits for a top level gendisk and a bottom level 645 * block_device. 646 */ 647 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev, 648 sector_t offset) 649 { 650 struct request_queue *t = disk->queue; 651 652 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) { 653 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE]; 654 655 disk_name(disk, 0, top); 656 bdevname(bdev, bottom); 657 658 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n", 659 top, bottom); 660 } 661 } 662 EXPORT_SYMBOL(disk_stack_limits); 663 664 /** 665 * blk_queue_dma_pad - set pad mask 666 * @q: the request queue for the device 667 * @mask: pad mask 668 * 669 * Set dma pad mask. 670 * 671 * Appending pad buffer to a request modifies the last entry of a 672 * scatter list such that it includes the pad buffer. 673 **/ 674 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask) 675 { 676 q->dma_pad_mask = mask; 677 } 678 EXPORT_SYMBOL(blk_queue_dma_pad); 679 680 /** 681 * blk_queue_update_dma_pad - update pad mask 682 * @q: the request queue for the device 683 * @mask: pad mask 684 * 685 * Update dma pad mask. 686 * 687 * Appending pad buffer to a request modifies the last entry of a 688 * scatter list such that it includes the pad buffer. 689 **/ 690 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask) 691 { 692 if (mask > q->dma_pad_mask) 693 q->dma_pad_mask = mask; 694 } 695 EXPORT_SYMBOL(blk_queue_update_dma_pad); 696 697 /** 698 * blk_queue_dma_drain - Set up a drain buffer for excess dma. 699 * @q: the request queue for the device 700 * @dma_drain_needed: fn which returns non-zero if drain is necessary 701 * @buf: physically contiguous buffer 702 * @size: size of the buffer in bytes 703 * 704 * Some devices have excess DMA problems and can't simply discard (or 705 * zero fill) the unwanted piece of the transfer. They have to have a 706 * real area of memory to transfer it into. The use case for this is 707 * ATAPI devices in DMA mode. If the packet command causes a transfer 708 * bigger than the transfer size some HBAs will lock up if there 709 * aren't DMA elements to contain the excess transfer. What this API 710 * does is adjust the queue so that the buf is always appended 711 * silently to the scatterlist. 712 * 713 * Note: This routine adjusts max_hw_segments to make room for appending 714 * the drain buffer. If you call blk_queue_max_segments() after calling 715 * this routine, you must set the limit to one fewer than your device 716 * can support otherwise there won't be room for the drain buffer. 717 */ 718 int blk_queue_dma_drain(struct request_queue *q, 719 dma_drain_needed_fn *dma_drain_needed, 720 void *buf, unsigned int size) 721 { 722 if (queue_max_segments(q) < 2) 723 return -EINVAL; 724 /* make room for appending the drain */ 725 blk_queue_max_segments(q, queue_max_segments(q) - 1); 726 q->dma_drain_needed = dma_drain_needed; 727 q->dma_drain_buffer = buf; 728 q->dma_drain_size = size; 729 730 return 0; 731 } 732 EXPORT_SYMBOL_GPL(blk_queue_dma_drain); 733 734 /** 735 * blk_queue_segment_boundary - set boundary rules for segment merging 736 * @q: the request queue for the device 737 * @mask: the memory boundary mask 738 **/ 739 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask) 740 { 741 if (mask < PAGE_CACHE_SIZE - 1) { 742 mask = PAGE_CACHE_SIZE - 1; 743 printk(KERN_INFO "%s: set to minimum %lx\n", 744 __func__, mask); 745 } 746 747 q->limits.seg_boundary_mask = mask; 748 } 749 EXPORT_SYMBOL(blk_queue_segment_boundary); 750 751 /** 752 * blk_queue_dma_alignment - set dma length and memory alignment 753 * @q: the request queue for the device 754 * @mask: alignment mask 755 * 756 * description: 757 * set required memory and length alignment for direct dma transactions. 758 * this is used when building direct io requests for the queue. 759 * 760 **/ 761 void blk_queue_dma_alignment(struct request_queue *q, int mask) 762 { 763 q->dma_alignment = mask; 764 } 765 EXPORT_SYMBOL(blk_queue_dma_alignment); 766 767 /** 768 * blk_queue_update_dma_alignment - update dma length and memory alignment 769 * @q: the request queue for the device 770 * @mask: alignment mask 771 * 772 * description: 773 * update required memory and length alignment for direct dma transactions. 774 * If the requested alignment is larger than the current alignment, then 775 * the current queue alignment is updated to the new value, otherwise it 776 * is left alone. The design of this is to allow multiple objects 777 * (driver, device, transport etc) to set their respective 778 * alignments without having them interfere. 779 * 780 **/ 781 void blk_queue_update_dma_alignment(struct request_queue *q, int mask) 782 { 783 BUG_ON(mask > PAGE_SIZE); 784 785 if (mask > q->dma_alignment) 786 q->dma_alignment = mask; 787 } 788 EXPORT_SYMBOL(blk_queue_update_dma_alignment); 789 790 /** 791 * blk_queue_flush - configure queue's cache flush capability 792 * @q: the request queue for the device 793 * @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA 794 * 795 * Tell block layer cache flush capability of @q. If it supports 796 * flushing, REQ_FLUSH should be set. If it supports bypassing 797 * write cache for individual writes, REQ_FUA should be set. 798 */ 799 void blk_queue_flush(struct request_queue *q, unsigned int flush) 800 { 801 WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA)); 802 803 if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA))) 804 flush &= ~REQ_FUA; 805 806 q->flush_flags = flush & (REQ_FLUSH | REQ_FUA); 807 } 808 EXPORT_SYMBOL_GPL(blk_queue_flush); 809 810 void blk_queue_flush_queueable(struct request_queue *q, bool queueable) 811 { 812 q->flush_not_queueable = !queueable; 813 } 814 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable); 815 816 static int __init blk_settings_init(void) 817 { 818 blk_max_low_pfn = max_low_pfn - 1; 819 blk_max_pfn = max_pfn - 1; 820 return 0; 821 } 822 subsys_initcall(blk_settings_init); 823