linux/block/blk-settings.c
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   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.
 108 */
 109void 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_write_same_sectors = 0;
 117        lim->max_discard_sectors = 0;
 118        lim->discard_granularity = 0;
 119        lim->discard_alignment = 0;
 120        lim->discard_misaligned = 0;
 121        lim->discard_zeroes_data = 0;
 122        lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
 123        lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
 124        lim->alignment_offset = 0;
 125        lim->io_opt = 0;
 126        lim->misaligned = 0;
 127        lim->cluster = 1;
 128}
 129EXPORT_SYMBOL(blk_set_default_limits);
 130
 131/**
 132 * blk_set_stacking_limits - set default limits for stacking devices
 133 * @lim:  the queue_limits structure to reset
 134 *
 135 * Description:
 136 *   Returns a queue_limit struct to its default state. Should be used
 137 *   by stacking drivers like DM that have no internal limits.
 138 */
 139void blk_set_stacking_limits(struct queue_limits *lim)
 140{
 141        blk_set_default_limits(lim);
 142
 143        /* Inherit limits from component devices */
 144        lim->discard_zeroes_data = 1;
 145        lim->max_segments = USHRT_MAX;
 146        lim->max_hw_sectors = UINT_MAX;
 147        lim->max_segment_size = UINT_MAX;
 148        lim->max_sectors = UINT_MAX;
 149        lim->max_write_same_sectors = UINT_MAX;
 150}
 151EXPORT_SYMBOL(blk_set_stacking_limits);
 152
 153/**
 154 * blk_queue_make_request - define an alternate make_request function for a device
 155 * @q:  the request queue for the device to be affected
 156 * @mfn: the alternate make_request function
 157 *
 158 * Description:
 159 *    The normal way for &struct bios to be passed to a device
 160 *    driver is for them to be collected into requests on a request
 161 *    queue, and then to allow the device driver to select requests
 162 *    off that queue when it is ready.  This works well for many block
 163 *    devices. However some block devices (typically virtual devices
 164 *    such as md or lvm) do not benefit from the processing on the
 165 *    request queue, and are served best by having the requests passed
 166 *    directly to them.  This can be achieved by providing a function
 167 *    to blk_queue_make_request().
 168 *
 169 * Caveat:
 170 *    The driver that does this *must* be able to deal appropriately
 171 *    with buffers in "highmemory". This can be accomplished by either calling
 172 *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
 173 *    blk_queue_bounce() to create a buffer in normal memory.
 174 **/
 175void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 176{
 177        /*
 178         * set defaults
 179         */
 180        q->nr_requests = BLKDEV_MAX_RQ;
 181
 182        q->make_request_fn = mfn;
 183        blk_queue_dma_alignment(q, 511);
 184        blk_queue_congestion_threshold(q);
 185        q->nr_batching = BLK_BATCH_REQ;
 186
 187        blk_set_default_limits(&q->limits);
 188
 189        /*
 190         * by default assume old behaviour and bounce for any highmem page
 191         */
 192        blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
 193}
 194EXPORT_SYMBOL(blk_queue_make_request);
 195
 196/**
 197 * blk_queue_bounce_limit - set bounce buffer limit for queue
 198 * @q: the request queue for the device
 199 * @dma_mask: the maximum address the device can handle
 200 *
 201 * Description:
 202 *    Different hardware can have different requirements as to what pages
 203 *    it can do I/O directly to. A low level driver can call
 204 *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
 205 *    buffers for doing I/O to pages residing above @dma_mask.
 206 **/
 207void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
 208{
 209        unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
 210        int dma = 0;
 211
 212        q->bounce_gfp = GFP_NOIO;
 213#if BITS_PER_LONG == 64
 214        /*
 215         * Assume anything <= 4GB can be handled by IOMMU.  Actually
 216         * some IOMMUs can handle everything, but I don't know of a
 217         * way to test this here.
 218         */
 219        if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
 220                dma = 1;
 221        q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
 222#else
 223        if (b_pfn < blk_max_low_pfn)
 224                dma = 1;
 225        q->limits.bounce_pfn = b_pfn;
 226#endif
 227        if (dma) {
 228                init_emergency_isa_pool();
 229                q->bounce_gfp = GFP_NOIO | GFP_DMA;
 230                q->limits.bounce_pfn = b_pfn;
 231        }
 232}
 233EXPORT_SYMBOL(blk_queue_bounce_limit);
 234
 235/**
 236 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
 237 * @limits: the queue limits
 238 * @max_hw_sectors:  max hardware sectors in the usual 512b unit
 239 *
 240 * Description:
 241 *    Enables a low level driver to set a hard upper limit,
 242 *    max_hw_sectors, on the size of requests.  max_hw_sectors is set by
 243 *    the device driver based upon the combined capabilities of I/O
 244 *    controller and storage device.
 245 *
 246 *    max_sectors is a soft limit imposed by the block layer for
 247 *    filesystem type requests.  This value can be overridden on a
 248 *    per-device basis in /sys/block/<device>/queue/max_sectors_kb.
 249 *    The soft limit can not exceed max_hw_sectors.
 250 **/
 251void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
 252{
 253        if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
 254                max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
 255                printk(KERN_INFO "%s: set to minimum %d\n",
 256                       __func__, max_hw_sectors);
 257        }
 258
 259        limits->max_hw_sectors = max_hw_sectors;
 260        limits->max_sectors = min_t(unsigned int, max_hw_sectors,
 261                                    BLK_DEF_MAX_SECTORS);
 262}
 263EXPORT_SYMBOL(blk_limits_max_hw_sectors);
 264
 265/**
 266 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
 267 * @q:  the request queue for the device
 268 * @max_hw_sectors:  max hardware sectors in the usual 512b unit
 269 *
 270 * Description:
 271 *    See description for blk_limits_max_hw_sectors().
 272 **/
 273void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
 274{
 275        blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
 276}
 277EXPORT_SYMBOL(blk_queue_max_hw_sectors);
 278
 279/**
 280 * blk_queue_max_discard_sectors - set max sectors for a single discard
 281 * @q:  the request queue for the device
 282 * @max_discard_sectors: maximum number of sectors to discard
 283 **/
 284void blk_queue_max_discard_sectors(struct request_queue *q,
 285                unsigned int max_discard_sectors)
 286{
 287        q->limits.max_discard_sectors = max_discard_sectors;
 288}
 289EXPORT_SYMBOL(blk_queue_max_discard_sectors);
 290
 291/**
 292 * blk_queue_max_write_same_sectors - set max sectors for a single write same
 293 * @q:  the request queue for the device
 294 * @max_write_same_sectors: maximum number of sectors to write per command
 295 **/
 296void blk_queue_max_write_same_sectors(struct request_queue *q,
 297                                      unsigned int max_write_same_sectors)
 298{
 299        q->limits.max_write_same_sectors = max_write_same_sectors;
 300}
 301EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
 302
 303/**
 304 * blk_queue_max_segments - set max hw segments for a request for this queue
 305 * @q:  the request queue for the device
 306 * @max_segments:  max number of segments
 307 *
 308 * Description:
 309 *    Enables a low level driver to set an upper limit on the number of
 310 *    hw data segments in a request.
 311 **/
 312void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
 313{
 314        if (!max_segments) {
 315                max_segments = 1;
 316                printk(KERN_INFO "%s: set to minimum %d\n",
 317                       __func__, max_segments);
 318        }
 319
 320        q->limits.max_segments = max_segments;
 321}
 322EXPORT_SYMBOL(blk_queue_max_segments);
 323
 324/**
 325 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
 326 * @q:  the request queue for the device
 327 * @max_size:  max size of segment in bytes
 328 *
 329 * Description:
 330 *    Enables a low level driver to set an upper limit on the size of a
 331 *    coalesced segment
 332 **/
 333void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
 334{
 335        if (max_size < PAGE_CACHE_SIZE) {
 336                max_size = PAGE_CACHE_SIZE;
 337                printk(KERN_INFO "%s: set to minimum %d\n",
 338                       __func__, max_size);
 339        }
 340
 341        q->limits.max_segment_size = max_size;
 342}
 343EXPORT_SYMBOL(blk_queue_max_segment_size);
 344
 345/**
 346 * blk_queue_logical_block_size - set logical block size for the queue
 347 * @q:  the request queue for the device
 348 * @size:  the logical block size, in bytes
 349 *
 350 * Description:
 351 *   This should be set to the lowest possible block size that the
 352 *   storage device can address.  The default of 512 covers most
 353 *   hardware.
 354 **/
 355void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
 356{
 357        q->limits.logical_block_size = size;
 358
 359        if (q->limits.physical_block_size < size)
 360                q->limits.physical_block_size = size;
 361
 362        if (q->limits.io_min < q->limits.physical_block_size)
 363                q->limits.io_min = q->limits.physical_block_size;
 364}
 365EXPORT_SYMBOL(blk_queue_logical_block_size);
 366
 367/**
 368 * blk_queue_physical_block_size - set physical block size for the queue
 369 * @q:  the request queue for the device
 370 * @size:  the physical block size, in bytes
 371 *
 372 * Description:
 373 *   This should be set to the lowest possible sector size that the
 374 *   hardware can operate on without reverting to read-modify-write
 375 *   operations.
 376 */
 377void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
 378{
 379        q->limits.physical_block_size = size;
 380
 381        if (q->limits.physical_block_size < q->limits.logical_block_size)
 382                q->limits.physical_block_size = q->limits.logical_block_size;
 383
 384        if (q->limits.io_min < q->limits.physical_block_size)
 385                q->limits.io_min = q->limits.physical_block_size;
 386}
 387EXPORT_SYMBOL(blk_queue_physical_block_size);
 388
 389/**
 390 * blk_queue_alignment_offset - set physical block alignment offset
 391 * @q:  the request queue for the device
 392 * @offset: alignment offset in bytes
 393 *
 394 * Description:
 395 *   Some devices are naturally misaligned to compensate for things like
 396 *   the legacy DOS partition table 63-sector offset.  Low-level drivers
 397 *   should call this function for devices whose first sector is not
 398 *   naturally aligned.
 399 */
 400void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
 401{
 402        q->limits.alignment_offset =
 403                offset & (q->limits.physical_block_size - 1);
 404        q->limits.misaligned = 0;
 405}
 406EXPORT_SYMBOL(blk_queue_alignment_offset);
 407
 408/**
 409 * blk_limits_io_min - set minimum request size for a device
 410 * @limits: the queue limits
 411 * @min:  smallest I/O size in bytes
 412 *
 413 * Description:
 414 *   Some devices have an internal block size bigger than the reported
 415 *   hardware sector size.  This function can be used to signal the
 416 *   smallest I/O the device can perform without incurring a performance
 417 *   penalty.
 418 */
 419void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
 420{
 421        limits->io_min = min;
 422
 423        if (limits->io_min < limits->logical_block_size)
 424                limits->io_min = limits->logical_block_size;
 425
 426        if (limits->io_min < limits->physical_block_size)
 427                limits->io_min = limits->physical_block_size;
 428}
 429EXPORT_SYMBOL(blk_limits_io_min);
 430
 431/**
 432 * blk_queue_io_min - set minimum request size for the queue
 433 * @q:  the request queue for the device
 434 * @min:  smallest I/O size in bytes
 435 *
 436 * Description:
 437 *   Storage devices may report a granularity or preferred minimum I/O
 438 *   size which is the smallest request the device can perform without
 439 *   incurring a performance penalty.  For disk drives this is often the
 440 *   physical block size.  For RAID arrays it is often the stripe chunk
 441 *   size.  A properly aligned multiple of minimum_io_size is the
 442 *   preferred request size for workloads where a high number of I/O
 443 *   operations is desired.
 444 */
 445void blk_queue_io_min(struct request_queue *q, unsigned int min)
 446{
 447        blk_limits_io_min(&q->limits, min);
 448}
 449EXPORT_SYMBOL(blk_queue_io_min);
 450
 451/**
 452 * blk_limits_io_opt - set optimal request size for a device
 453 * @limits: the queue limits
 454 * @opt:  smallest I/O size in bytes
 455 *
 456 * Description:
 457 *   Storage devices may report an optimal I/O size, which is the
 458 *   device's preferred unit for sustained I/O.  This is rarely reported
 459 *   for disk drives.  For RAID arrays it is usually the stripe width or
 460 *   the internal track size.  A properly aligned multiple of
 461 *   optimal_io_size is the preferred request size for workloads where
 462 *   sustained throughput is desired.
 463 */
 464void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
 465{
 466        limits->io_opt = opt;
 467}
 468EXPORT_SYMBOL(blk_limits_io_opt);
 469
 470/**
 471 * blk_queue_io_opt - set optimal request size for the queue
 472 * @q:  the request queue for the device
 473 * @opt:  optimal request size in bytes
 474 *
 475 * Description:
 476 *   Storage devices may report an optimal I/O size, which is the
 477 *   device's preferred unit for sustained I/O.  This is rarely reported
 478 *   for disk drives.  For RAID arrays it is usually the stripe width or
 479 *   the internal track size.  A properly aligned multiple of
 480 *   optimal_io_size is the preferred request size for workloads where
 481 *   sustained throughput is desired.
 482 */
 483void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
 484{
 485        blk_limits_io_opt(&q->limits, opt);
 486}
 487EXPORT_SYMBOL(blk_queue_io_opt);
 488
 489/**
 490 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
 491 * @t:  the stacking driver (top)
 492 * @b:  the underlying device (bottom)
 493 **/
 494void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 495{
 496        blk_stack_limits(&t->limits, &b->limits, 0);
 497}
 498EXPORT_SYMBOL(blk_queue_stack_limits);
 499
 500/**
 501 * blk_stack_limits - adjust queue_limits for stacked devices
 502 * @t:  the stacking driver limits (top device)
 503 * @b:  the underlying queue limits (bottom, component device)
 504 * @start:  first data sector within component device
 505 *
 506 * Description:
 507 *    This function is used by stacking drivers like MD and DM to ensure
 508 *    that all component devices have compatible block sizes and
 509 *    alignments.  The stacking driver must provide a queue_limits
 510 *    struct (top) and then iteratively call the stacking function for
 511 *    all component (bottom) devices.  The stacking function will
 512 *    attempt to combine the values and ensure proper alignment.
 513 *
 514 *    Returns 0 if the top and bottom queue_limits are compatible.  The
 515 *    top device's block sizes and alignment offsets may be adjusted to
 516 *    ensure alignment with the bottom device. If no compatible sizes
 517 *    and alignments exist, -1 is returned and the resulting top
 518 *    queue_limits will have the misaligned flag set to indicate that
 519 *    the alignment_offset is undefined.
 520 */
 521int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 522                     sector_t start)
 523{
 524        unsigned int top, bottom, alignment, ret = 0;
 525
 526        t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
 527        t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
 528        t->max_write_same_sectors = min(t->max_write_same_sectors,
 529                                        b->max_write_same_sectors);
 530        t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
 531
 532        t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
 533                                            b->seg_boundary_mask);
 534
 535        t->max_segments = min_not_zero(t->max_segments, b->max_segments);
 536        t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
 537                                                 b->max_integrity_segments);
 538
 539        t->max_segment_size = min_not_zero(t->max_segment_size,
 540                                           b->max_segment_size);
 541
 542        t->misaligned |= b->misaligned;
 543
 544        alignment = queue_limit_alignment_offset(b, start);
 545
 546        /* Bottom device has different alignment.  Check that it is
 547         * compatible with the current top alignment.
 548         */
 549        if (t->alignment_offset != alignment) {
 550
 551                top = max(t->physical_block_size, t->io_min)
 552                        + t->alignment_offset;
 553                bottom = max(b->physical_block_size, b->io_min) + alignment;
 554
 555                /* Verify that top and bottom intervals line up */
 556                if (max(top, bottom) % min(top, bottom)) {
 557                        t->misaligned = 1;
 558                        ret = -1;
 559                }
 560        }
 561
 562        t->logical_block_size = max(t->logical_block_size,
 563                                    b->logical_block_size);
 564
 565        t->physical_block_size = max(t->physical_block_size,
 566                                     b->physical_block_size);
 567
 568        t->io_min = max(t->io_min, b->io_min);
 569        t->io_opt = lcm(t->io_opt, b->io_opt);
 570
 571        t->cluster &= b->cluster;
 572        t->discard_zeroes_data &= b->discard_zeroes_data;
 573
 574        /* Physical block size a multiple of the logical block size? */
 575        if (t->physical_block_size & (t->logical_block_size - 1)) {
 576                t->physical_block_size = t->logical_block_size;
 577                t->misaligned = 1;
 578                ret = -1;
 579        }
 580
 581        /* Minimum I/O a multiple of the physical block size? */
 582        if (t->io_min & (t->physical_block_size - 1)) {
 583                t->io_min = t->physical_block_size;
 584                t->misaligned = 1;
 585                ret = -1;
 586        }
 587
 588        /* Optimal I/O a multiple of the physical block size? */
 589        if (t->io_opt & (t->physical_block_size - 1)) {
 590                t->io_opt = 0;
 591                t->misaligned = 1;
 592                ret = -1;
 593        }
 594
 595        /* Find lowest common alignment_offset */
 596        t->alignment_offset = lcm(t->alignment_offset, alignment)
 597                % max(t->physical_block_size, t->io_min);
 598
 599        /* Verify that new alignment_offset is on a logical block boundary */
 600        if (t->alignment_offset & (t->logical_block_size - 1)) {
 601                t->misaligned = 1;
 602                ret = -1;
 603        }
 604
 605        /* Discard alignment and granularity */
 606        if (b->discard_granularity) {
 607                alignment = queue_limit_discard_alignment(b, start);
 608
 609                if (t->discard_granularity != 0 &&
 610                    t->discard_alignment != alignment) {
 611                        top = t->discard_granularity + t->discard_alignment;
 612                        bottom = b->discard_granularity + alignment;
 613
 614                        /* Verify that top and bottom intervals line up */
 615                        if ((max(top, bottom) % min(top, bottom)) != 0)
 616                                t->discard_misaligned = 1;
 617                }
 618
 619                t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
 620                                                      b->max_discard_sectors);
 621                t->discard_granularity = max(t->discard_granularity,
 622                                             b->discard_granularity);
 623                t->discard_alignment = lcm(t->discard_alignment, alignment) %
 624                        t->discard_granularity;
 625        }
 626
 627        return ret;
 628}
 629EXPORT_SYMBOL(blk_stack_limits);
 630
 631/**
 632 * bdev_stack_limits - adjust queue limits for stacked drivers
 633 * @t:  the stacking driver limits (top device)
 634 * @bdev:  the component block_device (bottom)
 635 * @start:  first data sector within component device
 636 *
 637 * Description:
 638 *    Merges queue limits for a top device and a block_device.  Returns
 639 *    0 if alignment didn't change.  Returns -1 if adding the bottom
 640 *    device caused misalignment.
 641 */
 642int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
 643                      sector_t start)
 644{
 645        struct request_queue *bq = bdev_get_queue(bdev);
 646
 647        start += get_start_sect(bdev);
 648
 649        return blk_stack_limits(t, &bq->limits, start);
 650}
 651EXPORT_SYMBOL(bdev_stack_limits);
 652
 653/**
 654 * disk_stack_limits - adjust queue limits for stacked drivers
 655 * @disk:  MD/DM gendisk (top)
 656 * @bdev:  the underlying block device (bottom)
 657 * @offset:  offset to beginning of data within component device
 658 *
 659 * Description:
 660 *    Merges the limits for a top level gendisk and a bottom level
 661 *    block_device.
 662 */
 663void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
 664                       sector_t offset)
 665{
 666        struct request_queue *t = disk->queue;
 667
 668        if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
 669                char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
 670
 671                disk_name(disk, 0, top);
 672                bdevname(bdev, bottom);
 673
 674                printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
 675                       top, bottom);
 676        }
 677}
 678EXPORT_SYMBOL(disk_stack_limits);
 679
 680/**
 681 * blk_queue_dma_pad - set pad mask
 682 * @q:     the request queue for the device
 683 * @mask:  pad mask
 684 *
 685 * Set 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 **/
 690void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
 691{
 692        q->dma_pad_mask = mask;
 693}
 694EXPORT_SYMBOL(blk_queue_dma_pad);
 695
 696/**
 697 * blk_queue_update_dma_pad - update pad mask
 698 * @q:     the request queue for the device
 699 * @mask:  pad mask
 700 *
 701 * Update dma pad mask.
 702 *
 703 * Appending pad buffer to a request modifies the last entry of a
 704 * scatter list such that it includes the pad buffer.
 705 **/
 706void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
 707{
 708        if (mask > q->dma_pad_mask)
 709                q->dma_pad_mask = mask;
 710}
 711EXPORT_SYMBOL(blk_queue_update_dma_pad);
 712
 713/**
 714 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
 715 * @q:  the request queue for the device
 716 * @dma_drain_needed: fn which returns non-zero if drain is necessary
 717 * @buf:        physically contiguous buffer
 718 * @size:       size of the buffer in bytes
 719 *
 720 * Some devices have excess DMA problems and can't simply discard (or
 721 * zero fill) the unwanted piece of the transfer.  They have to have a
 722 * real area of memory to transfer it into.  The use case for this is
 723 * ATAPI devices in DMA mode.  If the packet command causes a transfer
 724 * bigger than the transfer size some HBAs will lock up if there
 725 * aren't DMA elements to contain the excess transfer.  What this API
 726 * does is adjust the queue so that the buf is always appended
 727 * silently to the scatterlist.
 728 *
 729 * Note: This routine adjusts max_hw_segments to make room for appending
 730 * the drain buffer.  If you call blk_queue_max_segments() after calling
 731 * this routine, you must set the limit to one fewer than your device
 732 * can support otherwise there won't be room for the drain buffer.
 733 */
 734int blk_queue_dma_drain(struct request_queue *q,
 735                               dma_drain_needed_fn *dma_drain_needed,
 736                               void *buf, unsigned int size)
 737{
 738        if (queue_max_segments(q) < 2)
 739                return -EINVAL;
 740        /* make room for appending the drain */
 741        blk_queue_max_segments(q, queue_max_segments(q) - 1);
 742        q->dma_drain_needed = dma_drain_needed;
 743        q->dma_drain_buffer = buf;
 744        q->dma_drain_size = size;
 745
 746        return 0;
 747}
 748EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
 749
 750/**
 751 * blk_queue_segment_boundary - set boundary rules for segment merging
 752 * @q:  the request queue for the device
 753 * @mask:  the memory boundary mask
 754 **/
 755void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
 756{
 757        if (mask < PAGE_CACHE_SIZE - 1) {
 758                mask = PAGE_CACHE_SIZE - 1;
 759                printk(KERN_INFO "%s: set to minimum %lx\n",
 760                       __func__, mask);
 761        }
 762
 763        q->limits.seg_boundary_mask = mask;
 764}
 765EXPORT_SYMBOL(blk_queue_segment_boundary);
 766
 767/**
 768 * blk_queue_dma_alignment - set dma length and memory alignment
 769 * @q:     the request queue for the device
 770 * @mask:  alignment mask
 771 *
 772 * description:
 773 *    set required memory and length alignment for direct dma transactions.
 774 *    this is used when building direct io requests for the queue.
 775 *
 776 **/
 777void blk_queue_dma_alignment(struct request_queue *q, int mask)
 778{
 779        q->dma_alignment = mask;
 780}
 781EXPORT_SYMBOL(blk_queue_dma_alignment);
 782
 783/**
 784 * blk_queue_update_dma_alignment - update dma length and memory alignment
 785 * @q:     the request queue for the device
 786 * @mask:  alignment mask
 787 *
 788 * description:
 789 *    update required memory and length alignment for direct dma transactions.
 790 *    If the requested alignment is larger than the current alignment, then
 791 *    the current queue alignment is updated to the new value, otherwise it
 792 *    is left alone.  The design of this is to allow multiple objects
 793 *    (driver, device, transport etc) to set their respective
 794 *    alignments without having them interfere.
 795 *
 796 **/
 797void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
 798{
 799        BUG_ON(mask > PAGE_SIZE);
 800
 801        if (mask > q->dma_alignment)
 802                q->dma_alignment = mask;
 803}
 804EXPORT_SYMBOL(blk_queue_update_dma_alignment);
 805
 806/**
 807 * blk_queue_flush - configure queue's cache flush capability
 808 * @q:          the request queue for the device
 809 * @flush:      0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
 810 *
 811 * Tell block layer cache flush capability of @q.  If it supports
 812 * flushing, REQ_FLUSH should be set.  If it supports bypassing
 813 * write cache for individual writes, REQ_FUA should be set.
 814 */
 815void blk_queue_flush(struct request_queue *q, unsigned int flush)
 816{
 817        WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
 818
 819        if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
 820                flush &= ~REQ_FUA;
 821
 822        q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
 823}
 824EXPORT_SYMBOL_GPL(blk_queue_flush);
 825
 826void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
 827{
 828        q->flush_not_queueable = !queueable;
 829}
 830EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
 831
 832static int __init blk_settings_init(void)
 833{
 834        blk_max_low_pfn = max_low_pfn - 1;
 835        blk_max_pfn = max_pfn - 1;
 836        return 0;
 837}
 838subsys_initcall(blk_settings_init);
 839