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
  11#include "blk.h"
  12
  13unsigned long blk_max_low_pfn;
  14EXPORT_SYMBOL(blk_max_low_pfn);
  15
  16unsigned long blk_max_pfn;
  17
  18/**
  19 * blk_queue_prep_rq - set a prepare_request function for queue
  20 * @q:          queue
  21 * @pfn:        prepare_request function
  22 *
  23 * It's possible for a queue to register a prepare_request callback which
  24 * is invoked before the request is handed to the request_fn. The goal of
  25 * the function is to prepare a request for I/O, it can be used to build a
  26 * cdb from the request data for instance.
  27 *
  28 */
  29void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
  30{
  31        q->prep_rq_fn = pfn;
  32}
  33EXPORT_SYMBOL(blk_queue_prep_rq);
  34
  35/**
  36 * blk_queue_set_discard - set a discard_sectors function for queue
  37 * @q:          queue
  38 * @dfn:        prepare_discard function
  39 *
  40 * It's possible for a queue to register a discard callback which is used
  41 * to transform a discard request into the appropriate type for the
  42 * hardware. If none is registered, then discard requests are failed
  43 * with %EOPNOTSUPP.
  44 *
  45 */
  46void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
  47{
  48        q->prepare_discard_fn = dfn;
  49}
  50EXPORT_SYMBOL(blk_queue_set_discard);
  51
  52/**
  53 * blk_queue_merge_bvec - set a merge_bvec function for queue
  54 * @q:          queue
  55 * @mbfn:       merge_bvec_fn
  56 *
  57 * Usually queues have static limitations on the max sectors or segments that
  58 * we can put in a request. Stacking drivers may have some settings that
  59 * are dynamic, and thus we have to query the queue whether it is ok to
  60 * add a new bio_vec to a bio at a given offset or not. If the block device
  61 * has such limitations, it needs to register a merge_bvec_fn to control
  62 * the size of bio's sent to it. Note that a block device *must* allow a
  63 * single page to be added to an empty bio. The block device driver may want
  64 * to use the bio_split() function to deal with these bio's. By default
  65 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
  66 * honored.
  67 */
  68void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
  69{
  70        q->merge_bvec_fn = mbfn;
  71}
  72EXPORT_SYMBOL(blk_queue_merge_bvec);
  73
  74void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
  75{
  76        q->softirq_done_fn = fn;
  77}
  78EXPORT_SYMBOL(blk_queue_softirq_done);
  79
  80void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
  81{
  82        q->rq_timeout = timeout;
  83}
  84EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
  85
  86void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
  87{
  88        q->rq_timed_out_fn = fn;
  89}
  90EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
  91
  92void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
  93{
  94        q->lld_busy_fn = fn;
  95}
  96EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
  97
  98/**
  99 * blk_queue_make_request - define an alternate make_request function for a device
 100 * @q:  the request queue for the device to be affected
 101 * @mfn: the alternate make_request function
 102 *
 103 * Description:
 104 *    The normal way for &struct bios to be passed to a device
 105 *    driver is for them to be collected into requests on a request
 106 *    queue, and then to allow the device driver to select requests
 107 *    off that queue when it is ready.  This works well for many block
 108 *    devices. However some block devices (typically virtual devices
 109 *    such as md or lvm) do not benefit from the processing on the
 110 *    request queue, and are served best by having the requests passed
 111 *    directly to them.  This can be achieved by providing a function
 112 *    to blk_queue_make_request().
 113 *
 114 * Caveat:
 115 *    The driver that does this *must* be able to deal appropriately
 116 *    with buffers in "highmemory". This can be accomplished by either calling
 117 *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
 118 *    blk_queue_bounce() to create a buffer in normal memory.
 119 **/
 120void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 121{
 122        /*
 123         * set defaults
 124         */
 125        q->nr_requests = BLKDEV_MAX_RQ;
 126        blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
 127        blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
 128        blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
 129        blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
 130
 131        q->make_request_fn = mfn;
 132        q->backing_dev_info.ra_pages =
 133                        (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 134        q->backing_dev_info.state = 0;
 135        q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
 136        blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
 137        blk_queue_hardsect_size(q, 512);
 138        blk_queue_dma_alignment(q, 511);
 139        blk_queue_congestion_threshold(q);
 140        q->nr_batching = BLK_BATCH_REQ;
 141
 142        q->unplug_thresh = 4;           /* hmm */
 143        q->unplug_delay = (3 * HZ) / 1000;      /* 3 milliseconds */
 144        if (q->unplug_delay == 0)
 145                q->unplug_delay = 1;
 146
 147        q->unplug_timer.function = blk_unplug_timeout;
 148        q->unplug_timer.data = (unsigned long)q;
 149
 150        /*
 151         * by default assume old behaviour and bounce for any highmem page
 152         */
 153        blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
 154}
 155EXPORT_SYMBOL(blk_queue_make_request);
 156
 157/**
 158 * blk_queue_bounce_limit - set bounce buffer limit for queue
 159 * @q: the request queue for the device
 160 * @dma_mask: the maximum address the device can handle
 161 *
 162 * Description:
 163 *    Different hardware can have different requirements as to what pages
 164 *    it can do I/O directly to. A low level driver can call
 165 *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
 166 *    buffers for doing I/O to pages residing above @dma_mask.
 167 **/
 168void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
 169{
 170        unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
 171        int dma = 0;
 172
 173        q->bounce_gfp = GFP_NOIO;
 174#if BITS_PER_LONG == 64
 175        /*
 176         * Assume anything <= 4GB can be handled by IOMMU.  Actually
 177         * some IOMMUs can handle everything, but I don't know of a
 178         * way to test this here.
 179         */
 180        if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
 181                dma = 1;
 182        q->bounce_pfn = max_low_pfn;
 183#else
 184        if (b_pfn < blk_max_low_pfn)
 185                dma = 1;
 186        q->bounce_pfn = b_pfn;
 187#endif
 188        if (dma) {
 189                init_emergency_isa_pool();
 190                q->bounce_gfp = GFP_NOIO | GFP_DMA;
 191                q->bounce_pfn = b_pfn;
 192        }
 193}
 194EXPORT_SYMBOL(blk_queue_bounce_limit);
 195
 196/**
 197 * blk_queue_max_sectors - set max sectors for a request for this queue
 198 * @q:  the request queue for the device
 199 * @max_sectors:  max sectors in the usual 512b unit
 200 *
 201 * Description:
 202 *    Enables a low level driver to set an upper limit on the size of
 203 *    received requests.
 204 **/
 205void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
 206{
 207        if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
 208                max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
 209                printk(KERN_INFO "%s: set to minimum %d\n",
 210                       __func__, max_sectors);
 211        }
 212
 213        if (BLK_DEF_MAX_SECTORS > max_sectors)
 214                q->max_hw_sectors = q->max_sectors = max_sectors;
 215        else {
 216                q->max_sectors = BLK_DEF_MAX_SECTORS;
 217                q->max_hw_sectors = max_sectors;
 218        }
 219}
 220EXPORT_SYMBOL(blk_queue_max_sectors);
 221
 222/**
 223 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
 224 * @q:  the request queue for the device
 225 * @max_segments:  max number of segments
 226 *
 227 * Description:
 228 *    Enables a low level driver to set an upper limit on the number of
 229 *    physical data segments in a request.  This would be the largest sized
 230 *    scatter list the driver could handle.
 231 **/
 232void blk_queue_max_phys_segments(struct request_queue *q,
 233                                 unsigned short max_segments)
 234{
 235        if (!max_segments) {
 236                max_segments = 1;
 237                printk(KERN_INFO "%s: set to minimum %d\n",
 238                       __func__, max_segments);
 239        }
 240
 241        q->max_phys_segments = max_segments;
 242}
 243EXPORT_SYMBOL(blk_queue_max_phys_segments);
 244
 245/**
 246 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
 247 * @q:  the request queue for the device
 248 * @max_segments:  max number of segments
 249 *
 250 * Description:
 251 *    Enables a low level driver to set an upper limit on the number of
 252 *    hw data segments in a request.  This would be the largest number of
 253 *    address/length pairs the host adapter can actually give at once
 254 *    to the device.
 255 **/
 256void blk_queue_max_hw_segments(struct request_queue *q,
 257                               unsigned short max_segments)
 258{
 259        if (!max_segments) {
 260                max_segments = 1;
 261                printk(KERN_INFO "%s: set to minimum %d\n",
 262                       __func__, max_segments);
 263        }
 264
 265        q->max_hw_segments = max_segments;
 266}
 267EXPORT_SYMBOL(blk_queue_max_hw_segments);
 268
 269/**
 270 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
 271 * @q:  the request queue for the device
 272 * @max_size:  max size of segment in bytes
 273 *
 274 * Description:
 275 *    Enables a low level driver to set an upper limit on the size of a
 276 *    coalesced segment
 277 **/
 278void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
 279{
 280        if (max_size < PAGE_CACHE_SIZE) {
 281                max_size = PAGE_CACHE_SIZE;
 282                printk(KERN_INFO "%s: set to minimum %d\n",
 283                       __func__, max_size);
 284        }
 285
 286        q->max_segment_size = max_size;
 287}
 288EXPORT_SYMBOL(blk_queue_max_segment_size);
 289
 290/**
 291 * blk_queue_hardsect_size - set hardware sector size for the queue
 292 * @q:  the request queue for the device
 293 * @size:  the hardware sector size, in bytes
 294 *
 295 * Description:
 296 *   This should typically be set to the lowest possible sector size
 297 *   that the hardware can operate on (possible without reverting to
 298 *   even internal read-modify-write operations). Usually the default
 299 *   of 512 covers most hardware.
 300 **/
 301void blk_queue_hardsect_size(struct request_queue *q, unsigned short size)
 302{
 303        q->hardsect_size = size;
 304}
 305EXPORT_SYMBOL(blk_queue_hardsect_size);
 306
 307/*
 308 * Returns the minimum that is _not_ zero, unless both are zero.
 309 */
 310#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
 311
 312/**
 313 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
 314 * @t:  the stacking driver (top)
 315 * @b:  the underlying device (bottom)
 316 **/
 317void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
 318{
 319        /* zero is "infinity" */
 320        t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
 321        t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
 322        t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask, b->seg_boundary_mask);
 323
 324        t->max_phys_segments = min_not_zero(t->max_phys_segments, b->max_phys_segments);
 325        t->max_hw_segments = min_not_zero(t->max_hw_segments, b->max_hw_segments);
 326        t->max_segment_size = min_not_zero(t->max_segment_size, b->max_segment_size);
 327        t->hardsect_size = max(t->hardsect_size, b->hardsect_size);
 328        if (!t->queue_lock)
 329                WARN_ON_ONCE(1);
 330        else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
 331                unsigned long flags;
 332                spin_lock_irqsave(t->queue_lock, flags);
 333                queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
 334                spin_unlock_irqrestore(t->queue_lock, flags);
 335        }
 336}
 337EXPORT_SYMBOL(blk_queue_stack_limits);
 338
 339/**
 340 * blk_queue_dma_pad - set pad mask
 341 * @q:     the request queue for the device
 342 * @mask:  pad mask
 343 *
 344 * Set dma pad mask.
 345 *
 346 * Appending pad buffer to a request modifies the last entry of a
 347 * scatter list such that it includes the pad buffer.
 348 **/
 349void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
 350{
 351        q->dma_pad_mask = mask;
 352}
 353EXPORT_SYMBOL(blk_queue_dma_pad);
 354
 355/**
 356 * blk_queue_update_dma_pad - update pad mask
 357 * @q:     the request queue for the device
 358 * @mask:  pad mask
 359 *
 360 * Update dma pad mask.
 361 *
 362 * Appending pad buffer to a request modifies the last entry of a
 363 * scatter list such that it includes the pad buffer.
 364 **/
 365void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
 366{
 367        if (mask > q->dma_pad_mask)
 368                q->dma_pad_mask = mask;
 369}
 370EXPORT_SYMBOL(blk_queue_update_dma_pad);
 371
 372/**
 373 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
 374 * @q:  the request queue for the device
 375 * @dma_drain_needed: fn which returns non-zero if drain is necessary
 376 * @buf:        physically contiguous buffer
 377 * @size:       size of the buffer in bytes
 378 *
 379 * Some devices have excess DMA problems and can't simply discard (or
 380 * zero fill) the unwanted piece of the transfer.  They have to have a
 381 * real area of memory to transfer it into.  The use case for this is
 382 * ATAPI devices in DMA mode.  If the packet command causes a transfer
 383 * bigger than the transfer size some HBAs will lock up if there
 384 * aren't DMA elements to contain the excess transfer.  What this API
 385 * does is adjust the queue so that the buf is always appended
 386 * silently to the scatterlist.
 387 *
 388 * Note: This routine adjusts max_hw_segments to make room for
 389 * appending the drain buffer.  If you call
 390 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
 391 * calling this routine, you must set the limit to one fewer than your
 392 * device can support otherwise there won't be room for the drain
 393 * buffer.
 394 */
 395int blk_queue_dma_drain(struct request_queue *q,
 396                               dma_drain_needed_fn *dma_drain_needed,
 397                               void *buf, unsigned int size)
 398{
 399        if (q->max_hw_segments < 2 || q->max_phys_segments < 2)
 400                return -EINVAL;
 401        /* make room for appending the drain */
 402        --q->max_hw_segments;
 403        --q->max_phys_segments;
 404        q->dma_drain_needed = dma_drain_needed;
 405        q->dma_drain_buffer = buf;
 406        q->dma_drain_size = size;
 407
 408        return 0;
 409}
 410EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
 411
 412/**
 413 * blk_queue_segment_boundary - set boundary rules for segment merging
 414 * @q:  the request queue for the device
 415 * @mask:  the memory boundary mask
 416 **/
 417void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
 418{
 419        if (mask < PAGE_CACHE_SIZE - 1) {
 420                mask = PAGE_CACHE_SIZE - 1;
 421                printk(KERN_INFO "%s: set to minimum %lx\n",
 422                       __func__, mask);
 423        }
 424
 425        q->seg_boundary_mask = mask;
 426}
 427EXPORT_SYMBOL(blk_queue_segment_boundary);
 428
 429/**
 430 * blk_queue_dma_alignment - set dma length and memory alignment
 431 * @q:     the request queue for the device
 432 * @mask:  alignment mask
 433 *
 434 * description:
 435 *    set required memory and length alignment for direct dma transactions.
 436 *    this is used when building direct io requests for the queue.
 437 *
 438 **/
 439void blk_queue_dma_alignment(struct request_queue *q, int mask)
 440{
 441        q->dma_alignment = mask;
 442}
 443EXPORT_SYMBOL(blk_queue_dma_alignment);
 444
 445/**
 446 * blk_queue_update_dma_alignment - update dma length and memory alignment
 447 * @q:     the request queue for the device
 448 * @mask:  alignment mask
 449 *
 450 * description:
 451 *    update required memory and length alignment for direct dma transactions.
 452 *    If the requested alignment is larger than the current alignment, then
 453 *    the current queue alignment is updated to the new value, otherwise it
 454 *    is left alone.  The design of this is to allow multiple objects
 455 *    (driver, device, transport etc) to set their respective
 456 *    alignments without having them interfere.
 457 *
 458 **/
 459void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
 460{
 461        BUG_ON(mask > PAGE_SIZE);
 462
 463        if (mask > q->dma_alignment)
 464                q->dma_alignment = mask;
 465}
 466EXPORT_SYMBOL(blk_queue_update_dma_alignment);
 467
 468static int __init blk_settings_init(void)
 469{
 470        blk_max_low_pfn = max_low_pfn - 1;
 471        blk_max_pfn = max_pfn - 1;
 472        return 0;
 473}
 474subsys_initcall(blk_settings_init);
 475