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