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_sectors = UINT_MAX;
 148        lim->max_write_same_sectors = UINT_MAX;
 149}
 150EXPORT_SYMBOL(blk_set_stacking_limits);
 151
 152/**
 153 * blk_queue_make_request - define an alternate make_request function for a device
 154 * @q:  the request queue for the device to be affected
 155 * @mfn: the alternate make_request function
 156 *
 157 * Description:
 158 *    The normal way for &struct bios to be passed to a device
 159 *    driver is for them to be collected into requests on a request
 160 *    queue, and then to allow the device driver to select requests
 161 *    off that queue when it is ready.  This works well for many block
 162 *    devices. However some block devices (typically virtual devices
 163 *    such as md or lvm) do not benefit from the processing on the
 164 *    request queue, and are served best by having the requests passed
 165 *    directly to them.  This can be achieved by providing a function
 166 *    to blk_queue_make_request().
 167 *
 168 * Caveat:
 169 *    The driver that does this *must* be able to deal appropriately
 170 *    with buffers in "highmemory". This can be accomplished by either calling
 171 *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
 172 *    blk_queue_bounce() to create a buffer in normal memory.
 173 **/
 174void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 175{
 176        /*
 177         * set defaults
 178         */
 179        q->nr_requests = BLKDEV_MAX_RQ;
 180
 181        q->make_request_fn = mfn;
 182        blk_queue_dma_alignment(q, 511);
 183        blk_queue_congestion_threshold(q);
 184        q->nr_batching = BLK_BATCH_REQ;
 185
 186        blk_set_default_limits(&q->limits);
 187
 188        /*
 189         * by default assume old behaviour and bounce for any highmem page
 190         */
 191        blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
 192}
 193EXPORT_SYMBOL(blk_queue_make_request);
 194
 195/**
 196 * blk_queue_bounce_limit - set bounce buffer limit for queue
 197 * @q: the request queue for the device
 198 * @dma_mask: the maximum address the device can handle
 199 *
 200 * Description:
 201 *    Different hardware can have different requirements as to what pages
 202 *    it can do I/O directly to. A low level driver can call
 203 *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
 204 *    buffers for doing I/O to pages residing above @dma_mask.
 205 **/
 206void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
 207{
 208        unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
 209        int dma = 0;
 210
 211        q->bounce_gfp = GFP_NOIO;
 212#if BITS_PER_LONG == 64
 213        /*
 214         * Assume anything <= 4GB can be handled by IOMMU.  Actually
 215         * some IOMMUs can handle everything, but I don't know of a
 216         * way to test this here.
 217         */
 218        if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
 219                dma = 1;
 220        q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
 221#else
 222        if (b_pfn < blk_max_low_pfn)
 223                dma = 1;
 224        q->limits.bounce_pfn = b_pfn;
 225#endif
 226        if (dma) {
 227                init_emergency_isa_pool();
 228                q->bounce_gfp = GFP_NOIO | GFP_DMA;
 229                q->limits.bounce_pfn = b_pfn;
 230        }
 231}
 232EXPORT_SYMBOL(blk_queue_bounce_limit);
 233
 234/**
 235 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
 236 * @limits: the queue limits
 237 * @max_hw_sectors:  max hardware sectors in the usual 512b unit
 238 *
 239 * Description:
 240 *    Enables a low level driver to set a hard upper limit,
 241 *    max_hw_sectors, on the size of requests.  max_hw_sectors is set by
 242 *    the device driver based upon the combined capabilities of I/O
 243 *    controller and storage device.
 244 *
 245 *    max_sectors is a soft limit imposed by the block layer for
 246 *    filesystem type requests.  This value can be overridden on a
 247 *    per-device basis in /sys/block/<device>/queue/max_sectors_kb.
 248 *    The soft limit can not exceed max_hw_sectors.
 249 **/
 250void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
 251{
 252        if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
 253                max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
 254                printk(KERN_INFO "%s: set to minimum %d\n",
 255                       __func__, max_hw_sectors);
 256        }
 257
 258        limits->max_hw_sectors = max_hw_sectors;
 259        limits->max_sectors = min_t(unsigned int, max_hw_sectors,
 260                                    BLK_DEF_MAX_SECTORS);
 261}
 262EXPORT_SYMBOL(blk_limits_max_hw_sectors);
 263
 264/**
 265 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
 266 * @q:  the request queue for the device
 267 * @max_hw_sectors:  max hardware sectors in the usual 512b unit
 268 *
 269 * Description:
 270 *    See description for blk_limits_max_hw_sectors().
 271 **/
 272void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
 273{
 274        blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
 275}
 276EXPORT_SYMBOL(blk_queue_max_hw_sectors);
 277
 278/**
 279 * blk_queue_max_discard_sectors - set max sectors for a single discard
 280 * @q:  the request queue for the device
 281 * @max_discard_sectors: maximum number of sectors to discard
 282 **/
 283void blk_queue_max_discard_sectors(struct request_queue *q,
 284                unsigned int max_discard_sectors)
 285{
 286        q->limits.max_discard_sectors = max_discard_sectors;
 287}
 288EXPORT_SYMBOL(blk_queue_max_discard_sectors);
 289
 290/**
 291 * blk_queue_max_write_same_sectors - set max sectors for a single write same
 292 * @q:  the request queue for the device
 293 * @max_write_same_sectors: maximum number of sectors to write per command
 294 **/
 295void blk_queue_max_write_same_sectors(struct request_queue *q,
 296                                      unsigned int max_write_same_sectors)
 297{
 298        q->limits.max_write_same_sectors = max_write_same_sectors;
 299}
 300EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
 301
 302/**
 303 * blk_queue_max_segments - set max hw segments for a request for this queue
 304 * @q:  the request queue for the device
 305 * @max_segments:  max number of segments
 306 *
 307 * Description:
 308 *    Enables a low level driver to set an upper limit on the number of
 309 *    hw data segments in a request.
 310 **/
 311void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
 312{
 313        if (!max_segments) {
 314                max_segments = 1;
 315                printk(KERN_INFO "%s: set to minimum %d\n",
 316                       __func__, max_segments);
 317        }
 318
 319        q->limits.max_segments = max_segments;
 320}
 321EXPORT_SYMBOL(blk_queue_max_segments);
 322
 323/**
 324 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
 325 * @q:  the request queue for the device
 326 * @max_size:  max size of segment in bytes
 327 *
 328 * Description:
 329 *    Enables a low level driver to set an upper limit on the size of a
 330 *    coalesced segment
 331 **/
 332void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
 333{
 334        if (max_size < PAGE_CACHE_SIZE) {
 335                max_size = PAGE_CACHE_SIZE;
 336                printk(KERN_INFO "%s: set to minimum %d\n",
 337                       __func__, max_size);
 338        }
 339
 340        q->limits.max_segment_size = max_size;
 341}
 342EXPORT_SYMBOL(blk_queue_max_segment_size);
 343
 344/**
 345 * blk_queue_logical_block_size - set logical block size for the queue
 346 * @q:  the request queue for the device
 347 * @size:  the logical block size, in bytes
 348 *
 349 * Description:
 350 *   This should be set to the lowest possible block size that the
 351 *   storage device can address.  The default of 512 covers most
 352 *   hardware.
 353 **/
 354void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
 355{
 356        q->limits.logical_block_size = size;
 357
 358        if (q->limits.physical_block_size < size)
 359                q->limits.physical_block_size = size;
 360
 361        if (q->limits.io_min < q->limits.physical_block_size)
 362                q->limits.io_min = q->limits.physical_block_size;
 363}
 364EXPORT_SYMBOL(blk_queue_logical_block_size);
 365
 366/**
 367 * blk_queue_physical_block_size - set physical block size for the queue
 368 * @q:  the request queue for the device
 369 * @size:  the physical block size, in bytes
 370 *
 371 * Description:
 372 *   This should be set to the lowest possible sector size that the
 373 *   hardware can operate on without reverting to read-modify-write
 374 *   operations.
 375 */
 376void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
 377{
 378        q->limits.physical_block_size = size;
 379
 380        if (q->limits.physical_block_size < q->limits.logical_block_size)
 381                q->limits.physical_block_size = q->limits.logical_block_size;
 382
 383        if (q->limits.io_min < q->limits.physical_block_size)
 384                q->limits.io_min = q->limits.physical_block_size;
 385}
 386EXPORT_SYMBOL(blk_queue_physical_block_size);
 387
 388/**
 389 * blk_queue_alignment_offset - set physical block alignment offset
 390 * @q:  the request queue for the device
 391 * @offset: alignment offset in bytes
 392 *
 393 * Description:
 394 *   Some devices are naturally misaligned to compensate for things like
 395 *   the legacy DOS partition table 63-sector offset.  Low-level drivers
 396 *   should call this function for devices whose first sector is not
 397 *   naturally aligned.
 398 */
 399void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
 400{
 401        q->limits.alignment_offset =
 402                offset & (q->limits.physical_block_size - 1);
 403        q->limits.misaligned = 0;
 404}
 405EXPORT_SYMBOL(blk_queue_alignment_offset);
 406
 407/**
 408 * blk_limits_io_min - set minimum request size for a device
 409 * @limits: the queue limits
 410 * @min:  smallest I/O size in bytes
 411 *
 412 * Description:
 413 *   Some devices have an internal block size bigger than the reported
 414 *   hardware sector size.  This function can be used to signal the
 415 *   smallest I/O the device can perform without incurring a performance
 416 *   penalty.
 417 */
 418void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
 419{
 420        limits->io_min = min;
 421
 422        if (limits->io_min < limits->logical_block_size)
 423                limits->io_min = limits->logical_block_size;
 424
 425        if (limits->io_min < limits->physical_block_size)
 426                limits->io_min = limits->physical_block_size;
 427}
 428EXPORT_SYMBOL(blk_limits_io_min);
 429
 430/**
 431 * blk_queue_io_min - set minimum request size for the queue
 432 * @q:  the request queue for the device
 433 * @min:  smallest I/O size in bytes
 434 *
 435 * Description:
 436 *   Storage devices may report a granularity or preferred minimum I/O
 437 *   size which is the smallest request the device can perform without
 438 *   incurring a performance penalty.  For disk drives this is often the
 439 *   physical block size.  For RAID arrays it is often the stripe chunk
 440 *   size.  A properly aligned multiple of minimum_io_size is the
 441 *   preferred request size for workloads where a high number of I/O
 442 *   operations is desired.
 443 */
 444void blk_queue_io_min(struct request_queue *q, unsigned int min)
 445{
 446        blk_limits_io_min(&q->limits, min);
 447}
 448EXPORT_SYMBOL(blk_queue_io_min);
 449
 450/**
 451 * blk_limits_io_opt - set optimal request size for a device
 452 * @limits: the queue limits
 453 * @opt:  smallest I/O size in bytes
 454 *
 455 * Description:
 456 *   Storage devices may report an optimal I/O size, which is the
 457 *   device's preferred unit for sustained I/O.  This is rarely reported
 458 *   for disk drives.  For RAID arrays it is usually the stripe width or
 459 *   the internal track size.  A properly aligned multiple of
 460 *   optimal_io_size is the preferred request size for workloads where
 461 *   sustained throughput is desired.
 462 */
 463void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
 464{
 465        limits->io_opt = opt;
 466}
 467EXPORT_SYMBOL(blk_limits_io_opt);
 468
 469/**
 470 * blk_queue_io_opt - set optimal request size for the queue
 471 * @q:  the request queue for the device
 472 * @opt:  optimal request size in bytes
 473 *
 474 * Description:
 475 *   Storage devices may report an optimal I/O size, which is the
 476 *   device's preferred unit for sustained I/O.  This is rarely reported
 477 *   for disk drives.  For RAID arrays it is usually the stripe width or
 478 *   the internal track size.  A properly aligned multiple of
 479 *   optimal_io_size is the preferred request size for workloads where
 480 *   sustained throughput is desired.
 481 */
 482void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
 483{
 484        blk_limits_io_opt(&q->limits, opt);
 485}
 486EXPORT_SYMBOL(blk_queue_io_opt);
 487
 488/**
 489 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
 490 * @t:  the stacking driver (top)
 491 * @b:  the underlying device (bottom)
 492 **/
 493void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 494{
 495        blk_stack_limits(&t->limits, &b->limits, 0);
 496}
 497EXPORT_SYMBOL(blk_queue_stack_limits);
 498
 499/**
 500 * blk_stack_limits - adjust queue_limits for stacked devices
 501 * @t:  the stacking driver limits (top device)
 502 * @b:  the underlying queue limits (bottom, component device)
 503 * @start:  first data sector within component device
 504 *
 505 * Description:
 506 *    This function is used by stacking drivers like MD and DM to ensure
 507 *    that all component devices have compatible block sizes and
 508 *    alignments.  The stacking driver must provide a queue_limits
 509 *    struct (top) and then iteratively call the stacking function for
 510 *    all component (bottom) devices.  The stacking function will
 511 *    attempt to combine the values and ensure proper alignment.
 512 *
 513 *    Returns 0 if the top and bottom queue_limits are compatible.  The
 514 *    top device's block sizes and alignment offsets may be adjusted to
 515 *    ensure alignment with the bottom device. If no compatible sizes
 516 *    and alignments exist, -1 is returned and the resulting top
 517 *    queue_limits will have the misaligned flag set to indicate that
 518 *    the alignment_offset is undefined.
 519 */
 520int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 521                     sector_t start)
 522{
 523        unsigned int top, bottom, alignment, ret = 0;
 524
 525        t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
 526        t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
 527        t->max_write_same_sectors = min(t->max_write_same_sectors,
 528                                        b->max_write_same_sectors);
 529        t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
 530
 531        t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
 532                                            b->seg_boundary_mask);
 533
 534        t->max_segments = min_not_zero(t->max_segments, b->max_segments);
 535        t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
 536                                                 b->max_integrity_segments);
 537
 538        t->max_segment_size = min_not_zero(t->max_segment_size,
 539                                           b->max_segment_size);
 540
 541        t->misaligned |= b->misaligned;
 542
 543        alignment = queue_limit_alignment_offset(b, start);
 544
 545        /* Bottom device has different alignment.  Check that it is
 546         * compatible with the current top alignment.
 547         */
 548        if (t->alignment_offset != alignment) {
 549
 550                top = max(t->physical_block_size, t->io_min)
 551                        + t->alignment_offset;
 552                bottom = max(b->physical_block_size, b->io_min) + alignment;
 553
 554                /* Verify that top and bottom intervals line up */
 555                if (max(top, bottom) & (min(top, bottom) - 1)) {
 556                        t->misaligned = 1;
 557                        ret = -1;
 558                }
 559        }
 560
 561        t->logical_block_size = max(t->logical_block_size,
 562                                    b->logical_block_size);
 563
 564        t->physical_block_size = max(t->physical_block_size,
 565                                     b->physical_block_size);
 566
 567        t->io_min = max(t->io_min, b->io_min);
 568        t->io_opt = lcm(t->io_opt, b->io_opt);
 569
 570        t->cluster &= b->cluster;
 571        t->discard_zeroes_data &= b->discard_zeroes_data;
 572
 573        /* Physical block size a multiple of the logical block size? */
 574        if (t->physical_block_size & (t->logical_block_size - 1)) {
 575                t->physical_block_size = t->logical_block_size;
 576                t->misaligned = 1;
 577                ret = -1;
 578        }
 579
 580        /* Minimum I/O a multiple of the physical block size? */
 581        if (t->io_min & (t->physical_block_size - 1)) {
 582                t->io_min = t->physical_block_size;
 583                t->misaligned = 1;
 584                ret = -1;
 585        }
 586
 587        /* Optimal I/O a multiple of the physical block size? */
 588        if (t->io_opt & (t->physical_block_size - 1)) {
 589                t->io_opt = 0;
 590                t->misaligned = 1;
 591                ret = -1;
 592        }
 593
 594        /* Find lowest common alignment_offset */
 595        t->alignment_offset = lcm(t->alignment_offset, alignment)
 596                & (max(t->physical_block_size, t->io_min) - 1);
 597
 598        /* Verify that new alignment_offset is on a logical block boundary */
 599        if (t->alignment_offset & (t->logical_block_size - 1)) {
 600                t->misaligned = 1;
 601                ret = -1;
 602        }
 603
 604        /* Discard alignment and granularity */
 605        if (b->discard_granularity) {
 606                alignment = queue_limit_discard_alignment(b, start);
 607
 608                if (t->discard_granularity != 0 &&
 609                    t->discard_alignment != alignment) {
 610                        top = t->discard_granularity + t->discard_alignment;
 611                        bottom = b->discard_granularity + alignment;
 612
 613                        /* Verify that top and bottom intervals line up */
 614                        if ((max(top, bottom) % min(top, bottom)) != 0)
 615                                t->discard_misaligned = 1;
 616                }
 617
 618                t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
 619                                                      b->max_discard_sectors);
 620                t->discard_granularity = max(t->discard_granularity,
 621                                             b->discard_granularity);
 622                t->discard_alignment = lcm(t->discard_alignment, alignment) %
 623                        t->discard_granularity;
 624        }
 625
 626        return ret;
 627}
 628EXPORT_SYMBOL(blk_stack_limits);
 629
 630/**
 631 * bdev_stack_limits - adjust queue limits for stacked drivers
 632 * @t:  the stacking driver limits (top device)
 633 * @bdev:  the component block_device (bottom)
 634 * @start:  first data sector within component device
 635 *
 636 * Description:
 637 *    Merges queue limits for a top device and a block_device.  Returns
 638 *    0 if alignment didn't change.  Returns -1 if adding the bottom
 639 *    device caused misalignment.
 640 */
 641int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
 642                      sector_t start)
 643{
 644        struct request_queue *bq = bdev_get_queue(bdev);
 645
 646        start += get_start_sect(bdev);
 647
 648        return blk_stack_limits(t, &bq->limits, start);
 649}
 650EXPORT_SYMBOL(bdev_stack_limits);
 651
 652/**
 653 * disk_stack_limits - adjust queue limits for stacked drivers
 654 * @disk:  MD/DM gendisk (top)
 655 * @bdev:  the underlying block device (bottom)
 656 * @offset:  offset to beginning of data within component device
 657 *
 658 * Description:
 659 *    Merges the limits for a top level gendisk and a bottom level
 660 *    block_device.
 661 */
 662void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
 663                       sector_t offset)
 664{
 665        struct request_queue *t = disk->queue;
 666
 667        if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
 668                char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
 669
 670                disk_name(disk, 0, top);
 671                bdevname(bdev, bottom);
 672
 673                printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
 674                       top, bottom);
 675        }
 676}
 677EXPORT_SYMBOL(disk_stack_limits);
 678
 679/**
 680 * blk_queue_dma_pad - set pad mask
 681 * @q:     the request queue for the device
 682 * @mask:  pad mask
 683 *
 684 * Set dma pad mask.
 685 *
 686 * Appending pad buffer to a request modifies the last entry of a
 687 * scatter list such that it includes the pad buffer.
 688 **/
 689void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
 690{
 691        q->dma_pad_mask = mask;
 692}
 693EXPORT_SYMBOL(blk_queue_dma_pad);
 694
 695/**
 696 * blk_queue_update_dma_pad - update pad mask
 697 * @q:     the request queue for the device
 698 * @mask:  pad mask
 699 *
 700 * Update dma pad mask.
 701 *
 702 * Appending pad buffer to a request modifies the last entry of a
 703 * scatter list such that it includes the pad buffer.
 704 **/
 705void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
 706{
 707        if (mask > q->dma_pad_mask)
 708                q->dma_pad_mask = mask;
 709}
 710EXPORT_SYMBOL(blk_queue_update_dma_pad);
 711
 712/**
 713 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
 714 * @q:  the request queue for the device
 715 * @dma_drain_needed: fn which returns non-zero if drain is necessary
 716 * @buf:        physically contiguous buffer
 717 * @size:       size of the buffer in bytes
 718 *
 719 * Some devices have excess DMA problems and can't simply discard (or
 720 * zero fill) the unwanted piece of the transfer.  They have to have a
 721 * real area of memory to transfer it into.  The use case for this is
 722 * ATAPI devices in DMA mode.  If the packet command causes a transfer
 723 * bigger than the transfer size some HBAs will lock up if there
 724 * aren't DMA elements to contain the excess transfer.  What this API
 725 * does is adjust the queue so that the buf is always appended
 726 * silently to the scatterlist.
 727 *
 728 * Note: This routine adjusts max_hw_segments to make room for appending
 729 * the drain buffer.  If you call blk_queue_max_segments() after calling
 730 * this routine, you must set the limit to one fewer than your device
 731 * can support otherwise there won't be room for the drain buffer.
 732 */
 733int blk_queue_dma_drain(struct request_queue *q,
 734                               dma_drain_needed_fn *dma_drain_needed,
 735                               void *buf, unsigned int size)
 736{
 737        if (queue_max_segments(q) < 2)
 738                return -EINVAL;
 739        /* make room for appending the drain */
 740        blk_queue_max_segments(q, queue_max_segments(q) - 1);
 741        q->dma_drain_needed = dma_drain_needed;
 742        q->dma_drain_buffer = buf;
 743        q->dma_drain_size = size;
 744
 745        return 0;
 746}
 747EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
 748
 749/**
 750 * blk_queue_segment_boundary - set boundary rules for segment merging
 751 * @q:  the request queue for the device
 752 * @mask:  the memory boundary mask
 753 **/
 754void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
 755{
 756        if (mask < PAGE_CACHE_SIZE - 1) {
 757                mask = PAGE_CACHE_SIZE - 1;
 758                printk(KERN_INFO "%s: set to minimum %lx\n",
 759                       __func__, mask);
 760        }
 761
 762        q->limits.seg_boundary_mask = mask;
 763}
 764EXPORT_SYMBOL(blk_queue_segment_boundary);
 765
 766/**
 767 * blk_queue_dma_alignment - set dma length and memory alignment
 768 * @q:     the request queue for the device
 769 * @mask:  alignment mask
 770 *
 771 * description:
 772 *    set required memory and length alignment for direct dma transactions.
 773 *    this is used when building direct io requests for the queue.
 774 *
 775 **/
 776void blk_queue_dma_alignment(struct request_queue *q, int mask)
 777{
 778        q->dma_alignment = mask;
 779}
 780EXPORT_SYMBOL(blk_queue_dma_alignment);
 781
 782/**
 783 * blk_queue_update_dma_alignment - update dma length and memory alignment
 784 * @q:     the request queue for the device
 785 * @mask:  alignment mask
 786 *
 787 * description:
 788 *    update required memory and length alignment for direct dma transactions.
 789 *    If the requested alignment is larger than the current alignment, then
 790 *    the current queue alignment is updated to the new value, otherwise it
 791 *    is left alone.  The design of this is to allow multiple objects
 792 *    (driver, device, transport etc) to set their respective
 793 *    alignments without having them interfere.
 794 *
 795 **/
 796void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
 797{
 798        BUG_ON(mask > PAGE_SIZE);
 799
 800        if (mask > q->dma_alignment)
 801                q->dma_alignment = mask;
 802}
 803EXPORT_SYMBOL(blk_queue_update_dma_alignment);
 804
 805/**
 806 * blk_queue_flush - configure queue's cache flush capability
 807 * @q:          the request queue for the device
 808 * @flush:      0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
 809 *
 810 * Tell block layer cache flush capability of @q.  If it supports
 811 * flushing, REQ_FLUSH should be set.  If it supports bypassing
 812 * write cache for individual writes, REQ_FUA should be set.
 813 */
 814void blk_queue_flush(struct request_queue *q, unsigned int flush)
 815{
 816        WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
 817
 818        if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
 819                flush &= ~REQ_FUA;
 820
 821        q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
 822}
 823EXPORT_SYMBOL_GPL(blk_queue_flush);
 824
 825void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
 826{
 827        q->flush_not_queueable = !queueable;
 828}
 829EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
 830
 831static int __init blk_settings_init(void)
 832{
 833        blk_max_low_pfn = max_low_pfn - 1;
 834        blk_max_pfn = max_pfn - 1;
 835        return 0;
 836}
 837subsys_initcall(blk_settings_init);
 838
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