2
* Functions related to setting various queue properties from drivers
4
#include <linux/kernel.h>
5
#include <linux/module.h>
6
#include <linux/init.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>
17
unsigned long blk_max_low_pfn;
18
EXPORT_SYMBOL(blk_max_low_pfn);
20
unsigned long blk_max_pfn;
23
* blk_queue_prep_rq - set a prepare_request function for queue
25
* @pfn: prepare_request function
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.
33
void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
37
EXPORT_SYMBOL(blk_queue_prep_rq);
40
* blk_queue_unprep_rq - set an unprepare_request function for queue
42
* @ufn: unprepare_request function
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.
50
void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn)
52
q->unprep_rq_fn = ufn;
54
EXPORT_SYMBOL(blk_queue_unprep_rq);
57
* blk_queue_merge_bvec - set a merge_bvec function for queue
59
* @mbfn: merge_bvec_fn
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
72
void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
74
q->merge_bvec_fn = mbfn;
76
EXPORT_SYMBOL(blk_queue_merge_bvec);
78
void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
80
q->softirq_done_fn = fn;
82
EXPORT_SYMBOL(blk_queue_softirq_done);
84
void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
86
q->rq_timeout = timeout;
88
EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
90
void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
92
q->rq_timed_out_fn = fn;
94
EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
96
void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
100
EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
103
* blk_set_default_limits - reset limits to default values
104
* @lim: the queue_limits structure to reset
107
* Returns a queue_limit struct to its default state. Can be used by
108
* stacking drivers like DM that stage table swaps and reuse an
109
* existing device queue.
111
void blk_set_default_limits(struct queue_limits *lim)
113
lim->max_segments = BLK_MAX_SEGMENTS;
114
lim->max_integrity_segments = 0;
115
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
116
lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
117
lim->max_sectors = BLK_DEF_MAX_SECTORS;
118
lim->max_hw_sectors = INT_MAX;
119
lim->max_discard_sectors = 0;
120
lim->discard_granularity = 0;
121
lim->discard_alignment = 0;
122
lim->discard_misaligned = 0;
123
lim->discard_zeroes_data = 1;
124
lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
125
lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
126
lim->alignment_offset = 0;
131
EXPORT_SYMBOL(blk_set_default_limits);
134
* blk_queue_make_request - define an alternate make_request function for a device
135
* @q: the request queue for the device to be affected
136
* @mfn: the alternate make_request function
139
* The normal way for &struct bios to be passed to a device
140
* driver is for them to be collected into requests on a request
141
* queue, and then to allow the device driver to select requests
142
* off that queue when it is ready. This works well for many block
143
* devices. However some block devices (typically virtual devices
144
* such as md or lvm) do not benefit from the processing on the
145
* request queue, and are served best by having the requests passed
146
* directly to them. This can be achieved by providing a function
147
* to blk_queue_make_request().
150
* The driver that does this *must* be able to deal appropriately
151
* with buffers in "highmemory". This can be accomplished by either calling
152
* __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
153
* blk_queue_bounce() to create a buffer in normal memory.
155
void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
160
q->nr_requests = BLKDEV_MAX_RQ;
162
q->make_request_fn = mfn;
163
blk_queue_dma_alignment(q, 511);
164
blk_queue_congestion_threshold(q);
165
q->nr_batching = BLK_BATCH_REQ;
167
blk_set_default_limits(&q->limits);
168
blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
169
q->limits.discard_zeroes_data = 0;
172
* by default assume old behaviour and bounce for any highmem page
174
blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
176
EXPORT_SYMBOL(blk_queue_make_request);
179
* blk_queue_bounce_limit - set bounce buffer limit for queue
180
* @q: the request queue for the device
181
* @dma_mask: the maximum address the device can handle
184
* Different hardware can have different requirements as to what pages
185
* it can do I/O directly to. A low level driver can call
186
* blk_queue_bounce_limit to have lower memory pages allocated as bounce
187
* buffers for doing I/O to pages residing above @dma_mask.
189
void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
191
unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
194
q->bounce_gfp = GFP_NOIO;
195
#if BITS_PER_LONG == 64
197
* Assume anything <= 4GB can be handled by IOMMU. Actually
198
* some IOMMUs can handle everything, but I don't know of a
199
* way to test this here.
201
if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
203
q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
205
if (b_pfn < blk_max_low_pfn)
207
q->limits.bounce_pfn = b_pfn;
210
init_emergency_isa_pool();
211
q->bounce_gfp = GFP_NOIO | GFP_DMA;
212
q->limits.bounce_pfn = b_pfn;
215
EXPORT_SYMBOL(blk_queue_bounce_limit);
218
* blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
219
* @limits: the queue limits
220
* @max_hw_sectors: max hardware sectors in the usual 512b unit
223
* Enables a low level driver to set a hard upper limit,
224
* max_hw_sectors, on the size of requests. max_hw_sectors is set by
225
* the device driver based upon the combined capabilities of I/O
226
* controller and storage device.
228
* max_sectors is a soft limit imposed by the block layer for
229
* filesystem type requests. This value can be overridden on a
230
* per-device basis in /sys/block/<device>/queue/max_sectors_kb.
231
* The soft limit can not exceed max_hw_sectors.
233
void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
235
if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
236
max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
237
printk(KERN_INFO "%s: set to minimum %d\n",
238
__func__, max_hw_sectors);
241
limits->max_hw_sectors = max_hw_sectors;
242
limits->max_sectors = min_t(unsigned int, max_hw_sectors,
243
BLK_DEF_MAX_SECTORS);
245
EXPORT_SYMBOL(blk_limits_max_hw_sectors);
248
* blk_queue_max_hw_sectors - set max sectors for a request for this queue
249
* @q: the request queue for the device
250
* @max_hw_sectors: max hardware sectors in the usual 512b unit
253
* See description for blk_limits_max_hw_sectors().
255
void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
257
blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
259
EXPORT_SYMBOL(blk_queue_max_hw_sectors);
262
* blk_queue_max_discard_sectors - set max sectors for a single discard
263
* @q: the request queue for the device
264
* @max_discard_sectors: maximum number of sectors to discard
266
void blk_queue_max_discard_sectors(struct request_queue *q,
267
unsigned int max_discard_sectors)
269
q->limits.max_discard_sectors = max_discard_sectors;
271
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
274
* blk_queue_max_segments - set max hw segments for a request for this queue
275
* @q: the request queue for the device
276
* @max_segments: max number of segments
279
* Enables a low level driver to set an upper limit on the number of
280
* hw data segments in a request.
282
void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
286
printk(KERN_INFO "%s: set to minimum %d\n",
287
__func__, max_segments);
290
q->limits.max_segments = max_segments;
292
EXPORT_SYMBOL(blk_queue_max_segments);
295
* blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
296
* @q: the request queue for the device
297
* @max_size: max size of segment in bytes
300
* Enables a low level driver to set an upper limit on the size of a
303
void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
305
if (max_size < PAGE_CACHE_SIZE) {
306
max_size = PAGE_CACHE_SIZE;
307
printk(KERN_INFO "%s: set to minimum %d\n",
311
q->limits.max_segment_size = max_size;
313
EXPORT_SYMBOL(blk_queue_max_segment_size);
316
* blk_queue_logical_block_size - set logical block size for the queue
317
* @q: the request queue for the device
318
* @size: the logical block size, in bytes
321
* This should be set to the lowest possible block size that the
322
* storage device can address. The default of 512 covers most
325
void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
327
q->limits.logical_block_size = size;
329
if (q->limits.physical_block_size < size)
330
q->limits.physical_block_size = size;
332
if (q->limits.io_min < q->limits.physical_block_size)
333
q->limits.io_min = q->limits.physical_block_size;
335
EXPORT_SYMBOL(blk_queue_logical_block_size);
338
* blk_queue_physical_block_size - set physical block size for the queue
339
* @q: the request queue for the device
340
* @size: the physical block size, in bytes
343
* This should be set to the lowest possible sector size that the
344
* hardware can operate on without reverting to read-modify-write
347
void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
349
q->limits.physical_block_size = size;
351
if (q->limits.physical_block_size < q->limits.logical_block_size)
352
q->limits.physical_block_size = q->limits.logical_block_size;
354
if (q->limits.io_min < q->limits.physical_block_size)
355
q->limits.io_min = q->limits.physical_block_size;
357
EXPORT_SYMBOL(blk_queue_physical_block_size);
360
* blk_queue_alignment_offset - set physical block alignment offset
361
* @q: the request queue for the device
362
* @offset: alignment offset in bytes
365
* Some devices are naturally misaligned to compensate for things like
366
* the legacy DOS partition table 63-sector offset. Low-level drivers
367
* should call this function for devices whose first sector is not
370
void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
372
q->limits.alignment_offset =
373
offset & (q->limits.physical_block_size - 1);
374
q->limits.misaligned = 0;
376
EXPORT_SYMBOL(blk_queue_alignment_offset);
379
* blk_limits_io_min - set minimum request size for a device
380
* @limits: the queue limits
381
* @min: smallest I/O size in bytes
384
* Some devices have an internal block size bigger than the reported
385
* hardware sector size. This function can be used to signal the
386
* smallest I/O the device can perform without incurring a performance
389
void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
391
limits->io_min = min;
393
if (limits->io_min < limits->logical_block_size)
394
limits->io_min = limits->logical_block_size;
396
if (limits->io_min < limits->physical_block_size)
397
limits->io_min = limits->physical_block_size;
399
EXPORT_SYMBOL(blk_limits_io_min);
402
* blk_queue_io_min - set minimum request size for the queue
403
* @q: the request queue for the device
404
* @min: smallest I/O size in bytes
407
* Storage devices may report a granularity or preferred minimum I/O
408
* size which is the smallest request the device can perform without
409
* incurring a performance penalty. For disk drives this is often the
410
* physical block size. For RAID arrays it is often the stripe chunk
411
* size. A properly aligned multiple of minimum_io_size is the
412
* preferred request size for workloads where a high number of I/O
413
* operations is desired.
415
void blk_queue_io_min(struct request_queue *q, unsigned int min)
417
blk_limits_io_min(&q->limits, min);
419
EXPORT_SYMBOL(blk_queue_io_min);
422
* blk_limits_io_opt - set optimal request size for a device
423
* @limits: the queue limits
424
* @opt: smallest I/O size in bytes
427
* Storage devices may report an optimal I/O size, which is the
428
* device's preferred unit for sustained I/O. This is rarely reported
429
* for disk drives. For RAID arrays it is usually the stripe width or
430
* the internal track size. A properly aligned multiple of
431
* optimal_io_size is the preferred request size for workloads where
432
* sustained throughput is desired.
434
void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
436
limits->io_opt = opt;
438
EXPORT_SYMBOL(blk_limits_io_opt);
441
* blk_queue_io_opt - set optimal request size for the queue
442
* @q: the request queue for the device
443
* @opt: optimal request size in bytes
446
* Storage devices may report an optimal I/O size, which is the
447
* device's preferred unit for sustained I/O. This is rarely reported
448
* for disk drives. For RAID arrays it is usually the stripe width or
449
* the internal track size. A properly aligned multiple of
450
* optimal_io_size is the preferred request size for workloads where
451
* sustained throughput is desired.
453
void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
455
blk_limits_io_opt(&q->limits, opt);
457
EXPORT_SYMBOL(blk_queue_io_opt);
460
* blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
461
* @t: the stacking driver (top)
462
* @b: the underlying device (bottom)
464
void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
466
blk_stack_limits(&t->limits, &b->limits, 0);
468
EXPORT_SYMBOL(blk_queue_stack_limits);
471
* blk_stack_limits - adjust queue_limits for stacked devices
472
* @t: the stacking driver limits (top device)
473
* @b: the underlying queue limits (bottom, component device)
474
* @start: first data sector within component device
477
* This function is used by stacking drivers like MD and DM to ensure
478
* that all component devices have compatible block sizes and
479
* alignments. The stacking driver must provide a queue_limits
480
* struct (top) and then iteratively call the stacking function for
481
* all component (bottom) devices. The stacking function will
482
* attempt to combine the values and ensure proper alignment.
484
* Returns 0 if the top and bottom queue_limits are compatible. The
485
* top device's block sizes and alignment offsets may be adjusted to
486
* ensure alignment with the bottom device. If no compatible sizes
487
* and alignments exist, -1 is returned and the resulting top
488
* queue_limits will have the misaligned flag set to indicate that
489
* the alignment_offset is undefined.
491
int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
494
unsigned int top, bottom, alignment, ret = 0;
496
t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
497
t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
498
t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
500
t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
501
b->seg_boundary_mask);
503
t->max_segments = min_not_zero(t->max_segments, b->max_segments);
504
t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
505
b->max_integrity_segments);
507
t->max_segment_size = min_not_zero(t->max_segment_size,
508
b->max_segment_size);
510
t->misaligned |= b->misaligned;
512
alignment = queue_limit_alignment_offset(b, start);
514
/* Bottom device has different alignment. Check that it is
515
* compatible with the current top alignment.
517
if (t->alignment_offset != alignment) {
519
top = max(t->physical_block_size, t->io_min)
520
+ t->alignment_offset;
521
bottom = max(b->physical_block_size, b->io_min) + alignment;
523
/* Verify that top and bottom intervals line up */
524
if (max(top, bottom) & (min(top, bottom) - 1)) {
530
t->logical_block_size = max(t->logical_block_size,
531
b->logical_block_size);
533
t->physical_block_size = max(t->physical_block_size,
534
b->physical_block_size);
536
t->io_min = max(t->io_min, b->io_min);
537
t->io_opt = lcm(t->io_opt, b->io_opt);
539
t->cluster &= b->cluster;
540
t->discard_zeroes_data &= b->discard_zeroes_data;
542
/* Physical block size a multiple of the logical block size? */
543
if (t->physical_block_size & (t->logical_block_size - 1)) {
544
t->physical_block_size = t->logical_block_size;
549
/* Minimum I/O a multiple of the physical block size? */
550
if (t->io_min & (t->physical_block_size - 1)) {
551
t->io_min = t->physical_block_size;
556
/* Optimal I/O a multiple of the physical block size? */
557
if (t->io_opt & (t->physical_block_size - 1)) {
563
/* Find lowest common alignment_offset */
564
t->alignment_offset = lcm(t->alignment_offset, alignment)
565
& (max(t->physical_block_size, t->io_min) - 1);
567
/* Verify that new alignment_offset is on a logical block boundary */
568
if (t->alignment_offset & (t->logical_block_size - 1)) {
573
/* Discard alignment and granularity */
574
if (b->discard_granularity) {
575
alignment = queue_limit_discard_alignment(b, start);
577
if (t->discard_granularity != 0 &&
578
t->discard_alignment != alignment) {
579
top = t->discard_granularity + t->discard_alignment;
580
bottom = b->discard_granularity + alignment;
582
/* Verify that top and bottom intervals line up */
583
if (max(top, bottom) & (min(top, bottom) - 1))
584
t->discard_misaligned = 1;
587
t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
588
b->max_discard_sectors);
589
t->discard_granularity = max(t->discard_granularity,
590
b->discard_granularity);
591
t->discard_alignment = lcm(t->discard_alignment, alignment) &
592
(t->discard_granularity - 1);
597
EXPORT_SYMBOL(blk_stack_limits);
600
* bdev_stack_limits - adjust queue limits for stacked drivers
601
* @t: the stacking driver limits (top device)
602
* @bdev: the component block_device (bottom)
603
* @start: first data sector within component device
606
* Merges queue limits for a top device and a block_device. Returns
607
* 0 if alignment didn't change. Returns -1 if adding the bottom
608
* device caused misalignment.
610
int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
613
struct request_queue *bq = bdev_get_queue(bdev);
615
start += get_start_sect(bdev);
617
return blk_stack_limits(t, &bq->limits, start);
619
EXPORT_SYMBOL(bdev_stack_limits);
622
* disk_stack_limits - adjust queue limits for stacked drivers
623
* @disk: MD/DM gendisk (top)
624
* @bdev: the underlying block device (bottom)
625
* @offset: offset to beginning of data within component device
628
* Merges the limits for a top level gendisk and a bottom level
631
void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
634
struct request_queue *t = disk->queue;
636
if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
637
char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
639
disk_name(disk, 0, top);
640
bdevname(bdev, bottom);
642
printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
646
EXPORT_SYMBOL(disk_stack_limits);
649
* blk_queue_dma_pad - set pad mask
650
* @q: the request queue for the device
655
* Appending pad buffer to a request modifies the last entry of a
656
* scatter list such that it includes the pad buffer.
658
void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
660
q->dma_pad_mask = mask;
662
EXPORT_SYMBOL(blk_queue_dma_pad);
665
* blk_queue_update_dma_pad - update pad mask
666
* @q: the request queue for the device
669
* Update dma pad mask.
671
* Appending pad buffer to a request modifies the last entry of a
672
* scatter list such that it includes the pad buffer.
674
void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
676
if (mask > q->dma_pad_mask)
677
q->dma_pad_mask = mask;
679
EXPORT_SYMBOL(blk_queue_update_dma_pad);
682
* blk_queue_dma_drain - Set up a drain buffer for excess dma.
683
* @q: the request queue for the device
684
* @dma_drain_needed: fn which returns non-zero if drain is necessary
685
* @buf: physically contiguous buffer
686
* @size: size of the buffer in bytes
688
* Some devices have excess DMA problems and can't simply discard (or
689
* zero fill) the unwanted piece of the transfer. They have to have a
690
* real area of memory to transfer it into. The use case for this is
691
* ATAPI devices in DMA mode. If the packet command causes a transfer
692
* bigger than the transfer size some HBAs will lock up if there
693
* aren't DMA elements to contain the excess transfer. What this API
694
* does is adjust the queue so that the buf is always appended
695
* silently to the scatterlist.
697
* Note: This routine adjusts max_hw_segments to make room for appending
698
* the drain buffer. If you call blk_queue_max_segments() after calling
699
* this routine, you must set the limit to one fewer than your device
700
* can support otherwise there won't be room for the drain buffer.
702
int blk_queue_dma_drain(struct request_queue *q,
703
dma_drain_needed_fn *dma_drain_needed,
704
void *buf, unsigned int size)
706
if (queue_max_segments(q) < 2)
708
/* make room for appending the drain */
709
blk_queue_max_segments(q, queue_max_segments(q) - 1);
710
q->dma_drain_needed = dma_drain_needed;
711
q->dma_drain_buffer = buf;
712
q->dma_drain_size = size;
716
EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
719
* blk_queue_segment_boundary - set boundary rules for segment merging
720
* @q: the request queue for the device
721
* @mask: the memory boundary mask
723
void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
725
if (mask < PAGE_CACHE_SIZE - 1) {
726
mask = PAGE_CACHE_SIZE - 1;
727
printk(KERN_INFO "%s: set to minimum %lx\n",
731
q->limits.seg_boundary_mask = mask;
733
EXPORT_SYMBOL(blk_queue_segment_boundary);
736
* blk_queue_dma_alignment - set dma length and memory alignment
737
* @q: the request queue for the device
738
* @mask: alignment mask
741
* set required memory and length alignment for direct dma transactions.
742
* this is used when building direct io requests for the queue.
745
void blk_queue_dma_alignment(struct request_queue *q, int mask)
747
q->dma_alignment = mask;
749
EXPORT_SYMBOL(blk_queue_dma_alignment);
752
* blk_queue_update_dma_alignment - update dma length and memory alignment
753
* @q: the request queue for the device
754
* @mask: alignment mask
757
* update required memory and length alignment for direct dma transactions.
758
* If the requested alignment is larger than the current alignment, then
759
* the current queue alignment is updated to the new value, otherwise it
760
* is left alone. The design of this is to allow multiple objects
761
* (driver, device, transport etc) to set their respective
762
* alignments without having them interfere.
765
void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
767
BUG_ON(mask > PAGE_SIZE);
769
if (mask > q->dma_alignment)
770
q->dma_alignment = mask;
772
EXPORT_SYMBOL(blk_queue_update_dma_alignment);
775
* blk_queue_flush - configure queue's cache flush capability
776
* @q: the request queue for the device
777
* @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
779
* Tell block layer cache flush capability of @q. If it supports
780
* flushing, REQ_FLUSH should be set. If it supports bypassing
781
* write cache for individual writes, REQ_FUA should be set.
783
void blk_queue_flush(struct request_queue *q, unsigned int flush)
785
WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
787
if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
790
q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
792
EXPORT_SYMBOL_GPL(blk_queue_flush);
794
void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
796
q->flush_not_queueable = !queueable;
798
EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
800
static int __init blk_settings_init(void)
802
blk_max_low_pfn = max_low_pfn - 1;
803
blk_max_pfn = max_pfn - 1;
806
subsys_initcall(blk_settings_init);