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