Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/block/blk-settings.c

  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 #include "blk-wbt.h"
 17 
 18 unsigned long blk_max_low_pfn;
 19 EXPORT_SYMBOL(blk_max_low_pfn);
 20 
 21 unsigned long blk_max_pfn;
 22 
 23 /**
 24  * blk_queue_prep_rq - set a prepare_request function for queue
 25  * @q:          queue
 26  * @pfn:        prepare_request function
 27  *
 28  * It's possible for a queue to register a prepare_request callback which
 29  * is invoked before the request is handed to the request_fn. The goal of
 30  * the function is to prepare a request for I/O, it can be used to build a
 31  * cdb from the request data for instance.
 32  *
 33  */
 34 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
 35 {
 36         q->prep_rq_fn = pfn;
 37 }
 38 EXPORT_SYMBOL(blk_queue_prep_rq);
 39 
 40 /**
 41  * blk_queue_unprep_rq - set an unprepare_request function for queue
 42  * @q:          queue
 43  * @ufn:        unprepare_request function
 44  *
 45  * It's possible for a queue to register an unprepare_request callback
 46  * which is invoked before the request is finally completed. The goal
 47  * of the function is to deallocate any data that was allocated in the
 48  * prepare_request callback.
 49  *
 50  */
 51 void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn)
 52 {
 53         q->unprep_rq_fn = ufn;
 54 }
 55 EXPORT_SYMBOL(blk_queue_unprep_rq);
 56 
 57 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
 58 {
 59         q->softirq_done_fn = fn;
 60 }
 61 EXPORT_SYMBOL(blk_queue_softirq_done);
 62 
 63 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
 64 {
 65         q->rq_timeout = timeout;
 66 }
 67 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
 68 
 69 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
 70 {
 71         q->rq_timed_out_fn = fn;
 72 }
 73 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
 74 
 75 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
 76 {
 77         q->lld_busy_fn = fn;
 78 }
 79 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
 80 
 81 /**
 82  * blk_set_default_limits - reset limits to default values
 83  * @lim:  the queue_limits structure to reset
 84  *
 85  * Description:
 86  *   Returns a queue_limit struct to its default state.
 87  */
 88 void blk_set_default_limits(struct queue_limits *lim)
 89 {
 90         lim->max_segments = BLK_MAX_SEGMENTS;
 91         lim->max_integrity_segments = 0;
 92         lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
 93         lim->virt_boundary_mask = 0;
 94         lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
 95         lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
 96         lim->max_dev_sectors = 0;
 97         lim->chunk_sectors = 0;
 98         lim->max_write_same_sectors = 0;
 99         lim->max_write_zeroes_sectors = 0;
100         lim->max_discard_sectors = 0;
101         lim->max_hw_discard_sectors = 0;
102         lim->discard_granularity = 0;
103         lim->discard_alignment = 0;
104         lim->discard_misaligned = 0;
105         lim->discard_zeroes_data = 0;
106         lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
107         lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
108         lim->alignment_offset = 0;
109         lim->io_opt = 0;
110         lim->misaligned = 0;
111         lim->cluster = 1;
112         lim->zoned = BLK_ZONED_NONE;
113 }
114 EXPORT_SYMBOL(blk_set_default_limits);
115 
116 /**
117  * blk_set_stacking_limits - set default limits for stacking devices
118  * @lim:  the queue_limits structure to reset
119  *
120  * Description:
121  *   Returns a queue_limit struct to its default state. Should be used
122  *   by stacking drivers like DM that have no internal limits.
123  */
124 void blk_set_stacking_limits(struct queue_limits *lim)
125 {
126         blk_set_default_limits(lim);
127 
128         /* Inherit limits from component devices */
129         lim->discard_zeroes_data = 1;
130         lim->max_segments = USHRT_MAX;
131         lim->max_hw_sectors = UINT_MAX;
132         lim->max_segment_size = UINT_MAX;
133         lim->max_sectors = UINT_MAX;
134         lim->max_dev_sectors = UINT_MAX;
135         lim->max_write_same_sectors = UINT_MAX;
136         lim->max_write_zeroes_sectors = UINT_MAX;
137 }
138 EXPORT_SYMBOL(blk_set_stacking_limits);
139 
140 /**
141  * blk_queue_make_request - define an alternate make_request function for a device
142  * @q:  the request queue for the device to be affected
143  * @mfn: the alternate make_request function
144  *
145  * Description:
146  *    The normal way for &struct bios to be passed to a device
147  *    driver is for them to be collected into requests on a request
148  *    queue, and then to allow the device driver to select requests
149  *    off that queue when it is ready.  This works well for many block
150  *    devices. However some block devices (typically virtual devices
151  *    such as md or lvm) do not benefit from the processing on the
152  *    request queue, and are served best by having the requests passed
153  *    directly to them.  This can be achieved by providing a function
154  *    to blk_queue_make_request().
155  *
156  * Caveat:
157  *    The driver that does this *must* be able to deal appropriately
158  *    with buffers in "highmemory". This can be accomplished by either calling
159  *    __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
160  *    blk_queue_bounce() to create a buffer in normal memory.
161  **/
162 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
163 {
164         /*
165          * set defaults
166          */
167         q->nr_requests = BLKDEV_MAX_RQ;
168 
169         q->make_request_fn = mfn;
170         blk_queue_dma_alignment(q, 511);
171         blk_queue_congestion_threshold(q);
172         q->nr_batching = BLK_BATCH_REQ;
173 
174         blk_set_default_limits(&q->limits);
175 
176         /*
177          * by default assume old behaviour and bounce for any highmem page
178          */
179         blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
180 }
181 EXPORT_SYMBOL(blk_queue_make_request);
182 
183 /**
184  * blk_queue_bounce_limit - set bounce buffer limit for queue
185  * @q: the request queue for the device
186  * @max_addr: the maximum address the device can handle
187  *
188  * Description:
189  *    Different hardware can have different requirements as to what pages
190  *    it can do I/O directly to. A low level driver can call
191  *    blk_queue_bounce_limit to have lower memory pages allocated as bounce
192  *    buffers for doing I/O to pages residing above @max_addr.
193  **/
194 void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr)
195 {
196         unsigned long b_pfn = max_addr >> PAGE_SHIFT;
197         int dma = 0;
198 
199         q->bounce_gfp = GFP_NOIO;
200 #if BITS_PER_LONG == 64
201         /*
202          * Assume anything <= 4GB can be handled by IOMMU.  Actually
203          * some IOMMUs can handle everything, but I don't know of a
204          * way to test this here.
205          */
206         if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
207                 dma = 1;
208         q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
209 #else
210         if (b_pfn < blk_max_low_pfn)
211                 dma = 1;
212         q->limits.bounce_pfn = b_pfn;
213 #endif
214         if (dma) {
215                 init_emergency_isa_pool();
216                 q->bounce_gfp = GFP_NOIO | GFP_DMA;
217                 q->limits.bounce_pfn = b_pfn;
218         }
219 }
220 EXPORT_SYMBOL(blk_queue_bounce_limit);
221 
222 /**
223  * blk_queue_max_hw_sectors - set max sectors for a request for this queue
224  * @q:  the request queue for the device
225  * @max_hw_sectors:  max hardware sectors in the usual 512b unit
226  *
227  * Description:
228  *    Enables a low level driver to set a hard upper limit,
229  *    max_hw_sectors, on the size of requests.  max_hw_sectors is set by
230  *    the device driver based upon the capabilities of the I/O
231  *    controller.
232  *
233  *    max_dev_sectors is a hard limit imposed by the storage device for
234  *    READ/WRITE requests. It is set by the disk driver.
235  *
236  *    max_sectors is a soft limit imposed by the block layer for
237  *    filesystem type requests.  This value can be overridden on a
238  *    per-device basis in /sys/block/<device>/queue/max_sectors_kb.
239  *    The soft limit can not exceed max_hw_sectors.
240  **/
241 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
242 {
243         struct queue_limits *limits = &q->limits;
244         unsigned int max_sectors;
245 
246         if ((max_hw_sectors << 9) < PAGE_SIZE) {
247                 max_hw_sectors = 1 << (PAGE_SHIFT - 9);
248                 printk(KERN_INFO "%s: set to minimum %d\n",
249                        __func__, max_hw_sectors);
250         }
251 
252         limits->max_hw_sectors = max_hw_sectors;
253         max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
254         max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
255         limits->max_sectors = max_sectors;
256         q->backing_dev_info.io_pages = max_sectors >> (PAGE_SHIFT - 9);
257 }
258 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
259 
260 /**
261  * blk_queue_chunk_sectors - set size of the chunk for this queue
262  * @q:  the request queue for the device
263  * @chunk_sectors:  chunk sectors in the usual 512b unit
264  *
265  * Description:
266  *    If a driver doesn't want IOs to cross a given chunk size, it can set
267  *    this limit and prevent merging across chunks. Note that the chunk size
268  *    must currently be a power-of-2 in sectors. Also note that the block
269  *    layer must accept a page worth of data at any offset. So if the
270  *    crossing of chunks is a hard limitation in the driver, it must still be
271  *    prepared to split single page bios.
272  **/
273 void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
274 {
275         BUG_ON(!is_power_of_2(chunk_sectors));
276         q->limits.chunk_sectors = chunk_sectors;
277 }
278 EXPORT_SYMBOL(blk_queue_chunk_sectors);
279 
280 /**
281  * blk_queue_max_discard_sectors - set max sectors for a single discard
282  * @q:  the request queue for the device
283  * @max_discard_sectors: maximum number of sectors to discard
284  **/
285 void blk_queue_max_discard_sectors(struct request_queue *q,
286                 unsigned int max_discard_sectors)
287 {
288         q->limits.max_hw_discard_sectors = max_discard_sectors;
289         q->limits.max_discard_sectors = max_discard_sectors;
290 }
291 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
292 
293 /**
294  * blk_queue_max_write_same_sectors - set max sectors for a single write same
295  * @q:  the request queue for the device
296  * @max_write_same_sectors: maximum number of sectors to write per command
297  **/
298 void blk_queue_max_write_same_sectors(struct request_queue *q,
299                                       unsigned int max_write_same_sectors)
300 {
301         q->limits.max_write_same_sectors = max_write_same_sectors;
302 }
303 EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
304 
305 /**
306  * blk_queue_max_write_zeroes_sectors - set max sectors for a single
307  *                                      write zeroes
308  * @q:  the request queue for the device
309  * @max_write_zeroes_sectors: maximum number of sectors to write per command
310  **/
311 void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
312                 unsigned int max_write_zeroes_sectors)
313 {
314         q->limits.max_write_zeroes_sectors = max_write_zeroes_sectors;
315 }
316 EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
317 
318 /**
319  * blk_queue_max_segments - set max hw segments for a request for this queue
320  * @q:  the request queue for the device
321  * @max_segments:  max number of segments
322  *
323  * Description:
324  *    Enables a low level driver to set an upper limit on the number of
325  *    hw data segments in a request.
326  **/
327 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
328 {
329         if (!max_segments) {
330                 max_segments = 1;
331                 printk(KERN_INFO "%s: set to minimum %d\n",
332                        __func__, max_segments);
333         }
334 
335         q->limits.max_segments = max_segments;
336 }
337 EXPORT_SYMBOL(blk_queue_max_segments);
338 
339 /**
340  * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
341  * @q:  the request queue for the device
342  * @max_size:  max size of segment in bytes
343  *
344  * Description:
345  *    Enables a low level driver to set an upper limit on the size of a
346  *    coalesced segment
347  **/
348 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
349 {
350         if (max_size < PAGE_SIZE) {
351                 max_size = PAGE_SIZE;
352                 printk(KERN_INFO "%s: set to minimum %d\n",
353                        __func__, max_size);
354         }
355 
356         q->limits.max_segment_size = max_size;
357 }
358 EXPORT_SYMBOL(blk_queue_max_segment_size);
359 
360 /**
361  * blk_queue_logical_block_size - set logical block size for the queue
362  * @q:  the request queue for the device
363  * @size:  the logical block size, in bytes
364  *
365  * Description:
366  *   This should be set to the lowest possible block size that the
367  *   storage device can address.  The default of 512 covers most
368  *   hardware.
369  **/
370 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
371 {
372         q->limits.logical_block_size = size;
373 
374         if (q->limits.physical_block_size < size)
375                 q->limits.physical_block_size = size;
376 
377         if (q->limits.io_min < q->limits.physical_block_size)
378                 q->limits.io_min = q->limits.physical_block_size;
379 }
380 EXPORT_SYMBOL(blk_queue_logical_block_size);
381 
382 /**
383  * blk_queue_physical_block_size - set physical block size for the queue
384  * @q:  the request queue for the device
385  * @size:  the physical block size, in bytes
386  *
387  * Description:
388  *   This should be set to the lowest possible sector size that the
389  *   hardware can operate on without reverting to read-modify-write
390  *   operations.
391  */
392 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
393 {
394         q->limits.physical_block_size = size;
395 
396         if (q->limits.physical_block_size < q->limits.logical_block_size)
397                 q->limits.physical_block_size = q->limits.logical_block_size;
398 
399         if (q->limits.io_min < q->limits.physical_block_size)
400                 q->limits.io_min = q->limits.physical_block_size;
401 }
402 EXPORT_SYMBOL(blk_queue_physical_block_size);
403 
404 /**
405  * blk_queue_alignment_offset - set physical block alignment offset
406  * @q:  the request queue for the device
407  * @offset: alignment offset in bytes
408  *
409  * Description:
410  *   Some devices are naturally misaligned to compensate for things like
411  *   the legacy DOS partition table 63-sector offset.  Low-level drivers
412  *   should call this function for devices whose first sector is not
413  *   naturally aligned.
414  */
415 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
416 {
417         q->limits.alignment_offset =
418                 offset & (q->limits.physical_block_size - 1);
419         q->limits.misaligned = 0;
420 }
421 EXPORT_SYMBOL(blk_queue_alignment_offset);
422 
423 /**
424  * blk_limits_io_min - set minimum request size for a device
425  * @limits: the queue limits
426  * @min:  smallest I/O size in bytes
427  *
428  * Description:
429  *   Some devices have an internal block size bigger than the reported
430  *   hardware sector size.  This function can be used to signal the
431  *   smallest I/O the device can perform without incurring a performance
432  *   penalty.
433  */
434 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
435 {
436         limits->io_min = min;
437 
438         if (limits->io_min < limits->logical_block_size)
439                 limits->io_min = limits->logical_block_size;
440 
441         if (limits->io_min < limits->physical_block_size)
442                 limits->io_min = limits->physical_block_size;
443 }
444 EXPORT_SYMBOL(blk_limits_io_min);
445 
446 /**
447  * blk_queue_io_min - set minimum request size for the queue
448  * @q:  the request queue for the device
449  * @min:  smallest I/O size in bytes
450  *
451  * Description:
452  *   Storage devices may report a granularity or preferred minimum I/O
453  *   size which is the smallest request the device can perform without
454  *   incurring a performance penalty.  For disk drives this is often the
455  *   physical block size.  For RAID arrays it is often the stripe chunk
456  *   size.  A properly aligned multiple of minimum_io_size is the
457  *   preferred request size for workloads where a high number of I/O
458  *   operations is desired.
459  */
460 void blk_queue_io_min(struct request_queue *q, unsigned int min)
461 {
462         blk_limits_io_min(&q->limits, min);
463 }
464 EXPORT_SYMBOL(blk_queue_io_min);
465 
466 /**
467  * blk_limits_io_opt - set optimal request size for a device
468  * @limits: the queue limits
469  * @opt:  smallest I/O size in bytes
470  *
471  * Description:
472  *   Storage devices may report an optimal I/O size, which is the
473  *   device's preferred unit for sustained I/O.  This is rarely reported
474  *   for disk drives.  For RAID arrays it is usually the stripe width or
475  *   the internal track size.  A properly aligned multiple of
476  *   optimal_io_size is the preferred request size for workloads where
477  *   sustained throughput is desired.
478  */
479 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
480 {
481         limits->io_opt = opt;
482 }
483 EXPORT_SYMBOL(blk_limits_io_opt);
484 
485 /**
486  * blk_queue_io_opt - set optimal request size for the queue
487  * @q:  the request queue for the device
488  * @opt:  optimal request size in bytes
489  *
490  * Description:
491  *   Storage devices may report an optimal I/O size, which is the
492  *   device's preferred unit for sustained I/O.  This is rarely reported
493  *   for disk drives.  For RAID arrays it is usually the stripe width or
494  *   the internal track size.  A properly aligned multiple of
495  *   optimal_io_size is the preferred request size for workloads where
496  *   sustained throughput is desired.
497  */
498 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
499 {
500         blk_limits_io_opt(&q->limits, opt);
501 }
502 EXPORT_SYMBOL(blk_queue_io_opt);
503 
504 /**
505  * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
506  * @t:  the stacking driver (top)
507  * @b:  the underlying device (bottom)
508  **/
509 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
510 {
511         blk_stack_limits(&t->limits, &b->limits, 0);
512 }
513 EXPORT_SYMBOL(blk_queue_stack_limits);
514 
515 /**
516  * blk_stack_limits - adjust queue_limits for stacked devices
517  * @t:  the stacking driver limits (top device)
518  * @b:  the underlying queue limits (bottom, component device)
519  * @start:  first data sector within component device
520  *
521  * Description:
522  *    This function is used by stacking drivers like MD and DM to ensure
523  *    that all component devices have compatible block sizes and
524  *    alignments.  The stacking driver must provide a queue_limits
525  *    struct (top) and then iteratively call the stacking function for
526  *    all component (bottom) devices.  The stacking function will
527  *    attempt to combine the values and ensure proper alignment.
528  *
529  *    Returns 0 if the top and bottom queue_limits are compatible.  The
530  *    top device's block sizes and alignment offsets may be adjusted to
531  *    ensure alignment with the bottom device. If no compatible sizes
532  *    and alignments exist, -1 is returned and the resulting top
533  *    queue_limits will have the misaligned flag set to indicate that
534  *    the alignment_offset is undefined.
535  */
536 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
537                      sector_t start)
538 {
539         unsigned int top, bottom, alignment, ret = 0;
540 
541         t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
542         t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
543         t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
544         t->max_write_same_sectors = min(t->max_write_same_sectors,
545                                         b->max_write_same_sectors);
546         t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors,
547                                         b->max_write_zeroes_sectors);
548         t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
549 
550         t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
551                                             b->seg_boundary_mask);
552         t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask,
553                                             b->virt_boundary_mask);
554 
555         t->max_segments = min_not_zero(t->max_segments, b->max_segments);
556         t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
557                                                  b->max_integrity_segments);
558 
559         t->max_segment_size = min_not_zero(t->max_segment_size,
560                                            b->max_segment_size);
561 
562         t->misaligned |= b->misaligned;
563 
564         alignment = queue_limit_alignment_offset(b, start);
565 
566         /* Bottom device has different alignment.  Check that it is
567          * compatible with the current top alignment.
568          */
569         if (t->alignment_offset != alignment) {
570 
571                 top = max(t->physical_block_size, t->io_min)
572                         + t->alignment_offset;
573                 bottom = max(b->physical_block_size, b->io_min) + alignment;
574 
575                 /* Verify that top and bottom intervals line up */
576                 if (max(top, bottom) % min(top, bottom)) {
577                         t->misaligned = 1;
578                         ret = -1;
579                 }
580         }
581 
582         t->logical_block_size = max(t->logical_block_size,
583                                     b->logical_block_size);
584 
585         t->physical_block_size = max(t->physical_block_size,
586                                      b->physical_block_size);
587 
588         t->io_min = max(t->io_min, b->io_min);
589         t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
590 
591         t->cluster &= b->cluster;
592         t->discard_zeroes_data &= b->discard_zeroes_data;
593 
594         /* Physical block size a multiple of the logical block size? */
595         if (t->physical_block_size & (t->logical_block_size - 1)) {
596                 t->physical_block_size = t->logical_block_size;
597                 t->misaligned = 1;
598                 ret = -1;
599         }
600 
601         /* Minimum I/O a multiple of the physical block size? */
602         if (t->io_min & (t->physical_block_size - 1)) {
603                 t->io_min = t->physical_block_size;
604                 t->misaligned = 1;
605                 ret = -1;
606         }
607 
608         /* Optimal I/O a multiple of the physical block size? */
609         if (t->io_opt & (t->physical_block_size - 1)) {
610                 t->io_opt = 0;
611                 t->misaligned = 1;
612                 ret = -1;
613         }
614 
615         t->raid_partial_stripes_expensive =
616                 max(t->raid_partial_stripes_expensive,
617                     b->raid_partial_stripes_expensive);
618 
619         /* Find lowest common alignment_offset */
620         t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
621                 % max(t->physical_block_size, t->io_min);
622 
623         /* Verify that new alignment_offset is on a logical block boundary */
624         if (t->alignment_offset & (t->logical_block_size - 1)) {
625                 t->misaligned = 1;
626                 ret = -1;
627         }
628 
629         /* Discard alignment and granularity */
630         if (b->discard_granularity) {
631                 alignment = queue_limit_discard_alignment(b, start);
632 
633                 if (t->discard_granularity != 0 &&
634                     t->discard_alignment != alignment) {
635                         top = t->discard_granularity + t->discard_alignment;
636                         bottom = b->discard_granularity + alignment;
637 
638                         /* Verify that top and bottom intervals line up */
639                         if ((max(top, bottom) % min(top, bottom)) != 0)
640                                 t->discard_misaligned = 1;
641                 }
642 
643                 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
644                                                       b->max_discard_sectors);
645                 t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
646                                                          b->max_hw_discard_sectors);
647                 t->discard_granularity = max(t->discard_granularity,
648                                              b->discard_granularity);
649                 t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
650                         t->discard_granularity;
651         }
652 
653         if (b->chunk_sectors)
654                 t->chunk_sectors = min_not_zero(t->chunk_sectors,
655                                                 b->chunk_sectors);
656 
657         return ret;
658 }
659 EXPORT_SYMBOL(blk_stack_limits);
660 
661 /**
662  * bdev_stack_limits - adjust queue limits for stacked drivers
663  * @t:  the stacking driver limits (top device)
664  * @bdev:  the component block_device (bottom)
665  * @start:  first data sector within component device
666  *
667  * Description:
668  *    Merges queue limits for a top device and a block_device.  Returns
669  *    0 if alignment didn't change.  Returns -1 if adding the bottom
670  *    device caused misalignment.
671  */
672 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
673                       sector_t start)
674 {
675         struct request_queue *bq = bdev_get_queue(bdev);
676 
677         start += get_start_sect(bdev);
678 
679         return blk_stack_limits(t, &bq->limits, start);
680 }
681 EXPORT_SYMBOL(bdev_stack_limits);
682 
683 /**
684  * disk_stack_limits - adjust queue limits for stacked drivers
685  * @disk:  MD/DM gendisk (top)
686  * @bdev:  the underlying block device (bottom)
687  * @offset:  offset to beginning of data within component device
688  *
689  * Description:
690  *    Merges the limits for a top level gendisk and a bottom level
691  *    block_device.
692  */
693 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
694                        sector_t offset)
695 {
696         struct request_queue *t = disk->queue;
697 
698         if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
699                 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
700 
701                 disk_name(disk, 0, top);
702                 bdevname(bdev, bottom);
703 
704                 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
705                        top, bottom);
706         }
707 }
708 EXPORT_SYMBOL(disk_stack_limits);
709 
710 /**
711  * blk_queue_dma_pad - set pad mask
712  * @q:     the request queue for the device
713  * @mask:  pad mask
714  *
715  * Set dma pad mask.
716  *
717  * Appending pad buffer to a request modifies the last entry of a
718  * scatter list such that it includes the pad buffer.
719  **/
720 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
721 {
722         q->dma_pad_mask = mask;
723 }
724 EXPORT_SYMBOL(blk_queue_dma_pad);
725 
726 /**
727  * blk_queue_update_dma_pad - update pad mask
728  * @q:     the request queue for the device
729  * @mask:  pad mask
730  *
731  * Update dma pad mask.
732  *
733  * Appending pad buffer to a request modifies the last entry of a
734  * scatter list such that it includes the pad buffer.
735  **/
736 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
737 {
738         if (mask > q->dma_pad_mask)
739                 q->dma_pad_mask = mask;
740 }
741 EXPORT_SYMBOL(blk_queue_update_dma_pad);
742 
743 /**
744  * blk_queue_dma_drain - Set up a drain buffer for excess dma.
745  * @q:  the request queue for the device
746  * @dma_drain_needed: fn which returns non-zero if drain is necessary
747  * @buf:        physically contiguous buffer
748  * @size:       size of the buffer in bytes
749  *
750  * Some devices have excess DMA problems and can't simply discard (or
751  * zero fill) the unwanted piece of the transfer.  They have to have a
752  * real area of memory to transfer it into.  The use case for this is
753  * ATAPI devices in DMA mode.  If the packet command causes a transfer
754  * bigger than the transfer size some HBAs will lock up if there
755  * aren't DMA elements to contain the excess transfer.  What this API
756  * does is adjust the queue so that the buf is always appended
757  * silently to the scatterlist.
758  *
759  * Note: This routine adjusts max_hw_segments to make room for appending
760  * the drain buffer.  If you call blk_queue_max_segments() after calling
761  * this routine, you must set the limit to one fewer than your device
762  * can support otherwise there won't be room for the drain buffer.
763  */
764 int blk_queue_dma_drain(struct request_queue *q,
765                                dma_drain_needed_fn *dma_drain_needed,
766                                void *buf, unsigned int size)
767 {
768         if (queue_max_segments(q) < 2)
769                 return -EINVAL;
770         /* make room for appending the drain */
771         blk_queue_max_segments(q, queue_max_segments(q) - 1);
772         q->dma_drain_needed = dma_drain_needed;
773         q->dma_drain_buffer = buf;
774         q->dma_drain_size = size;
775 
776         return 0;
777 }
778 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
779 
780 /**
781  * blk_queue_segment_boundary - set boundary rules for segment merging
782  * @q:  the request queue for the device
783  * @mask:  the memory boundary mask
784  **/
785 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
786 {
787         if (mask < PAGE_SIZE - 1) {
788                 mask = PAGE_SIZE - 1;
789                 printk(KERN_INFO "%s: set to minimum %lx\n",
790                        __func__, mask);
791         }
792 
793         q->limits.seg_boundary_mask = mask;
794 }
795 EXPORT_SYMBOL(blk_queue_segment_boundary);
796 
797 /**
798  * blk_queue_virt_boundary - set boundary rules for bio merging
799  * @q:  the request queue for the device
800  * @mask:  the memory boundary mask
801  **/
802 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
803 {
804         q->limits.virt_boundary_mask = mask;
805 }
806 EXPORT_SYMBOL(blk_queue_virt_boundary);
807 
808 /**
809  * blk_queue_dma_alignment - set dma length and memory alignment
810  * @q:     the request queue for the device
811  * @mask:  alignment mask
812  *
813  * description:
814  *    set required memory and length alignment for direct dma transactions.
815  *    this is used when building direct io requests for the queue.
816  *
817  **/
818 void blk_queue_dma_alignment(struct request_queue *q, int mask)
819 {
820         q->dma_alignment = mask;
821 }
822 EXPORT_SYMBOL(blk_queue_dma_alignment);
823 
824 /**
825  * blk_queue_update_dma_alignment - update dma length and memory alignment
826  * @q:     the request queue for the device
827  * @mask:  alignment mask
828  *
829  * description:
830  *    update required memory and length alignment for direct dma transactions.
831  *    If the requested alignment is larger than the current alignment, then
832  *    the current queue alignment is updated to the new value, otherwise it
833  *    is left alone.  The design of this is to allow multiple objects
834  *    (driver, device, transport etc) to set their respective
835  *    alignments without having them interfere.
836  *
837  **/
838 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
839 {
840         BUG_ON(mask > PAGE_SIZE);
841 
842         if (mask > q->dma_alignment)
843                 q->dma_alignment = mask;
844 }
845 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
846 
847 void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
848 {
849         spin_lock_irq(q->queue_lock);
850         if (queueable)
851                 clear_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
852         else
853                 set_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
854         spin_unlock_irq(q->queue_lock);
855 }
856 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
857 
858 /**
859  * blk_set_queue_depth - tell the block layer about the device queue depth
860  * @q:          the request queue for the device
861  * @depth:              queue depth
862  *
863  */
864 void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
865 {
866         q->queue_depth = depth;
867         wbt_set_queue_depth(q->rq_wb, depth);
868 }
869 EXPORT_SYMBOL(blk_set_queue_depth);
870 
871 /**
872  * blk_queue_write_cache - configure queue's write cache
873  * @q:          the request queue for the device
874  * @wc:         write back cache on or off
875  * @fua:        device supports FUA writes, if true
876  *
877  * Tell the block layer about the write cache of @q.
878  */
879 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
880 {
881         spin_lock_irq(q->queue_lock);
882         if (wc)
883                 queue_flag_set(QUEUE_FLAG_WC, q);
884         else
885                 queue_flag_clear(QUEUE_FLAG_WC, q);
886         if (fua)
887                 queue_flag_set(QUEUE_FLAG_FUA, q);
888         else
889                 queue_flag_clear(QUEUE_FLAG_FUA, q);
890         spin_unlock_irq(q->queue_lock);
891 
892         wbt_set_write_cache(q->rq_wb, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
893 }
894 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
895 
896 static int __init blk_settings_init(void)
897 {
898         blk_max_low_pfn = max_low_pfn - 1;
899         blk_max_pfn = max_pfn - 1;
900         return 0;
901 }
902 subsys_initcall(blk_settings_init);
903 

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