1 // SPDX-License-Identifier: GPL-2.0
3 * Functions related to setting various queue properties from drivers
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/init.h>
9 #include <linux/blkdev.h>
10 #include <linux/memblock.h> /* for max_pfn/max_low_pfn */
11 #include <linux/gcd.h>
12 #include <linux/lcm.h>
13 #include <linux/jiffies.h>
14 #include <linux/gfp.h>
15 #include <linux/dma-mapping.h>
20 unsigned long blk_max_low_pfn;
21 EXPORT_SYMBOL(blk_max_low_pfn);
23 unsigned long blk_max_pfn;
25 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
27 q->rq_timeout = timeout;
29 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
32 * blk_set_default_limits - reset limits to default values
33 * @lim: the queue_limits structure to reset
36 * Returns a queue_limit struct to its default state.
38 void blk_set_default_limits(struct queue_limits *lim)
40 lim->max_segments = BLK_MAX_SEGMENTS;
41 lim->max_discard_segments = 1;
42 lim->max_integrity_segments = 0;
43 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
44 lim->virt_boundary_mask = 0;
45 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
46 lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
47 lim->max_dev_sectors = 0;
48 lim->chunk_sectors = 0;
49 lim->max_write_same_sectors = 0;
50 lim->max_write_zeroes_sectors = 0;
51 lim->max_zone_append_sectors = 0;
52 lim->max_discard_sectors = 0;
53 lim->max_hw_discard_sectors = 0;
54 lim->discard_granularity = 0;
55 lim->discard_alignment = 0;
56 lim->discard_misaligned = 0;
57 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
58 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
59 lim->alignment_offset = 0;
62 lim->zoned = BLK_ZONED_NONE;
64 EXPORT_SYMBOL(blk_set_default_limits);
67 * blk_set_stacking_limits - set default limits for stacking devices
68 * @lim: the queue_limits structure to reset
71 * Returns a queue_limit struct to its default state. Should be used
72 * by stacking drivers like DM that have no internal limits.
74 void blk_set_stacking_limits(struct queue_limits *lim)
76 blk_set_default_limits(lim);
78 /* Inherit limits from component devices */
79 lim->max_segments = USHRT_MAX;
80 lim->max_discard_segments = USHRT_MAX;
81 lim->max_hw_sectors = UINT_MAX;
82 lim->max_segment_size = UINT_MAX;
83 lim->max_sectors = UINT_MAX;
84 lim->max_dev_sectors = UINT_MAX;
85 lim->max_write_same_sectors = UINT_MAX;
86 lim->max_write_zeroes_sectors = UINT_MAX;
87 lim->max_zone_append_sectors = UINT_MAX;
89 EXPORT_SYMBOL(blk_set_stacking_limits);
92 * blk_queue_bounce_limit - set bounce buffer limit for queue
93 * @q: the request queue for the device
94 * @max_addr: the maximum address the device can handle
97 * Different hardware can have different requirements as to what pages
98 * it can do I/O directly to. A low level driver can call
99 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
100 * buffers for doing I/O to pages residing above @max_addr.
102 void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr)
104 unsigned long b_pfn = max_addr >> PAGE_SHIFT;
107 q->bounce_gfp = GFP_NOIO;
108 #if BITS_PER_LONG == 64
110 * Assume anything <= 4GB can be handled by IOMMU. Actually
111 * some IOMMUs can handle everything, but I don't know of a
112 * way to test this here.
114 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
116 q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
118 if (b_pfn < blk_max_low_pfn)
120 q->limits.bounce_pfn = b_pfn;
123 init_emergency_isa_pool();
124 q->bounce_gfp = GFP_NOIO | GFP_DMA;
125 q->limits.bounce_pfn = b_pfn;
128 EXPORT_SYMBOL(blk_queue_bounce_limit);
131 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
132 * @q: the request queue for the device
133 * @max_hw_sectors: max hardware sectors in the usual 512b unit
136 * Enables a low level driver to set a hard upper limit,
137 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
138 * the device driver based upon the capabilities of the I/O
141 * max_dev_sectors is a hard limit imposed by the storage device for
142 * READ/WRITE requests. It is set by the disk driver.
144 * max_sectors is a soft limit imposed by the block layer for
145 * filesystem type requests. This value can be overridden on a
146 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
147 * The soft limit can not exceed max_hw_sectors.
149 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
151 struct queue_limits *limits = &q->limits;
152 unsigned int max_sectors;
154 if ((max_hw_sectors << 9) < PAGE_SIZE) {
155 max_hw_sectors = 1 << (PAGE_SHIFT - 9);
156 printk(KERN_INFO "%s: set to minimum %d\n",
157 __func__, max_hw_sectors);
160 limits->max_hw_sectors = max_hw_sectors;
161 max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
162 max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
163 limits->max_sectors = max_sectors;
164 q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9);
166 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
169 * blk_queue_chunk_sectors - set size of the chunk for this queue
170 * @q: the request queue for the device
171 * @chunk_sectors: chunk sectors in the usual 512b unit
174 * If a driver doesn't want IOs to cross a given chunk size, it can set
175 * this limit and prevent merging across chunks. Note that the block layer
176 * must accept a page worth of data at any offset. So if the crossing of
177 * chunks is a hard limitation in the driver, it must still be prepared
178 * to split single page bios.
180 void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
182 q->limits.chunk_sectors = chunk_sectors;
184 EXPORT_SYMBOL(blk_queue_chunk_sectors);
187 * blk_queue_max_discard_sectors - set max sectors for a single discard
188 * @q: the request queue for the device
189 * @max_discard_sectors: maximum number of sectors to discard
191 void blk_queue_max_discard_sectors(struct request_queue *q,
192 unsigned int max_discard_sectors)
194 q->limits.max_hw_discard_sectors = max_discard_sectors;
195 q->limits.max_discard_sectors = max_discard_sectors;
197 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
200 * blk_queue_max_write_same_sectors - set max sectors for a single write same
201 * @q: the request queue for the device
202 * @max_write_same_sectors: maximum number of sectors to write per command
204 void blk_queue_max_write_same_sectors(struct request_queue *q,
205 unsigned int max_write_same_sectors)
207 q->limits.max_write_same_sectors = max_write_same_sectors;
209 EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
212 * blk_queue_max_write_zeroes_sectors - set max sectors for a single
214 * @q: the request queue for the device
215 * @max_write_zeroes_sectors: maximum number of sectors to write per command
217 void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
218 unsigned int max_write_zeroes_sectors)
220 q->limits.max_write_zeroes_sectors = max_write_zeroes_sectors;
222 EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
225 * blk_queue_max_zone_append_sectors - set max sectors for a single zone append
226 * @q: the request queue for the device
227 * @max_zone_append_sectors: maximum number of sectors to write per command
229 void blk_queue_max_zone_append_sectors(struct request_queue *q,
230 unsigned int max_zone_append_sectors)
232 unsigned int max_sectors;
234 if (WARN_ON(!blk_queue_is_zoned(q)))
237 max_sectors = min(q->limits.max_hw_sectors, max_zone_append_sectors);
238 max_sectors = min(q->limits.chunk_sectors, max_sectors);
241 * Signal eventual driver bugs resulting in the max_zone_append sectors limit
242 * being 0 due to a 0 argument, the chunk_sectors limit (zone size) not set,
243 * or the max_hw_sectors limit not set.
245 WARN_ON(!max_sectors);
247 q->limits.max_zone_append_sectors = max_sectors;
249 EXPORT_SYMBOL_GPL(blk_queue_max_zone_append_sectors);
252 * blk_queue_max_segments - set max hw segments for a request for this queue
253 * @q: the request queue for the device
254 * @max_segments: max number of segments
257 * Enables a low level driver to set an upper limit on the number of
258 * hw data segments in a request.
260 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
264 printk(KERN_INFO "%s: set to minimum %d\n",
265 __func__, max_segments);
268 q->limits.max_segments = max_segments;
270 EXPORT_SYMBOL(blk_queue_max_segments);
273 * blk_queue_max_discard_segments - set max segments for discard requests
274 * @q: the request queue for the device
275 * @max_segments: max number of segments
278 * Enables a low level driver to set an upper limit on the number of
279 * segments in a discard request.
281 void blk_queue_max_discard_segments(struct request_queue *q,
282 unsigned short max_segments)
284 q->limits.max_discard_segments = max_segments;
286 EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments);
289 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
290 * @q: the request queue for the device
291 * @max_size: max size of segment in bytes
294 * Enables a low level driver to set an upper limit on the size of a
297 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
299 if (max_size < PAGE_SIZE) {
300 max_size = PAGE_SIZE;
301 printk(KERN_INFO "%s: set to minimum %d\n",
305 /* see blk_queue_virt_boundary() for the explanation */
306 WARN_ON_ONCE(q->limits.virt_boundary_mask);
308 q->limits.max_segment_size = max_size;
310 EXPORT_SYMBOL(blk_queue_max_segment_size);
313 * blk_queue_logical_block_size - set logical block size for the queue
314 * @q: the request queue for the device
315 * @size: the logical block size, in bytes
318 * This should be set to the lowest possible block size that the
319 * storage device can address. The default of 512 covers most
322 void blk_queue_logical_block_size(struct request_queue *q, unsigned int size)
324 q->limits.logical_block_size = size;
326 if (q->limits.physical_block_size < size)
327 q->limits.physical_block_size = size;
329 if (q->limits.io_min < q->limits.physical_block_size)
330 q->limits.io_min = q->limits.physical_block_size;
332 EXPORT_SYMBOL(blk_queue_logical_block_size);
335 * blk_queue_physical_block_size - set physical block size for the queue
336 * @q: the request queue for the device
337 * @size: the physical block size, in bytes
340 * This should be set to the lowest possible sector size that the
341 * hardware can operate on without reverting to read-modify-write
344 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
346 q->limits.physical_block_size = size;
348 if (q->limits.physical_block_size < q->limits.logical_block_size)
349 q->limits.physical_block_size = q->limits.logical_block_size;
351 if (q->limits.io_min < q->limits.physical_block_size)
352 q->limits.io_min = q->limits.physical_block_size;
354 EXPORT_SYMBOL(blk_queue_physical_block_size);
357 * blk_queue_alignment_offset - set physical block alignment offset
358 * @q: the request queue for the device
359 * @offset: alignment offset in bytes
362 * Some devices are naturally misaligned to compensate for things like
363 * the legacy DOS partition table 63-sector offset. Low-level drivers
364 * should call this function for devices whose first sector is not
367 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
369 q->limits.alignment_offset =
370 offset & (q->limits.physical_block_size - 1);
371 q->limits.misaligned = 0;
373 EXPORT_SYMBOL(blk_queue_alignment_offset);
376 * blk_limits_io_min - set minimum request size for a device
377 * @limits: the queue limits
378 * @min: smallest I/O size in bytes
381 * Some devices have an internal block size bigger than the reported
382 * hardware sector size. This function can be used to signal the
383 * smallest I/O the device can perform without incurring a performance
386 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
388 limits->io_min = min;
390 if (limits->io_min < limits->logical_block_size)
391 limits->io_min = limits->logical_block_size;
393 if (limits->io_min < limits->physical_block_size)
394 limits->io_min = limits->physical_block_size;
396 EXPORT_SYMBOL(blk_limits_io_min);
399 * blk_queue_io_min - set minimum request size for the queue
400 * @q: the request queue for the device
401 * @min: smallest I/O size in bytes
404 * Storage devices may report a granularity or preferred minimum I/O
405 * size which is the smallest request the device can perform without
406 * incurring a performance penalty. For disk drives this is often the
407 * physical block size. For RAID arrays it is often the stripe chunk
408 * size. A properly aligned multiple of minimum_io_size is the
409 * preferred request size for workloads where a high number of I/O
410 * operations is desired.
412 void blk_queue_io_min(struct request_queue *q, unsigned int min)
414 blk_limits_io_min(&q->limits, min);
416 EXPORT_SYMBOL(blk_queue_io_min);
419 * blk_limits_io_opt - set optimal request size for a device
420 * @limits: the queue limits
421 * @opt: smallest I/O size in bytes
424 * Storage devices may report an optimal I/O size, which is the
425 * device's preferred unit for sustained I/O. This is rarely reported
426 * for disk drives. For RAID arrays it is usually the stripe width or
427 * the internal track size. A properly aligned multiple of
428 * optimal_io_size is the preferred request size for workloads where
429 * sustained throughput is desired.
431 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
433 limits->io_opt = opt;
435 EXPORT_SYMBOL(blk_limits_io_opt);
438 * blk_queue_io_opt - set optimal request size for the queue
439 * @q: the request queue for the device
440 * @opt: optimal request size in bytes
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.
450 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
452 blk_limits_io_opt(&q->limits, opt);
454 EXPORT_SYMBOL(blk_queue_io_opt);
457 * blk_stack_limits - adjust queue_limits for stacked devices
458 * @t: the stacking driver limits (top device)
459 * @b: the underlying queue limits (bottom, component device)
460 * @start: first data sector within component device
463 * This function is used by stacking drivers like MD and DM to ensure
464 * that all component devices have compatible block sizes and
465 * alignments. The stacking driver must provide a queue_limits
466 * struct (top) and then iteratively call the stacking function for
467 * all component (bottom) devices. The stacking function will
468 * attempt to combine the values and ensure proper alignment.
470 * Returns 0 if the top and bottom queue_limits are compatible. The
471 * top device's block sizes and alignment offsets may be adjusted to
472 * ensure alignment with the bottom device. If no compatible sizes
473 * and alignments exist, -1 is returned and the resulting top
474 * queue_limits will have the misaligned flag set to indicate that
475 * the alignment_offset is undefined.
477 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
480 unsigned int top, bottom, alignment, ret = 0;
482 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
483 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
484 t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
485 t->max_write_same_sectors = min(t->max_write_same_sectors,
486 b->max_write_same_sectors);
487 t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors,
488 b->max_write_zeroes_sectors);
489 t->max_zone_append_sectors = min(t->max_zone_append_sectors,
490 b->max_zone_append_sectors);
491 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
493 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
494 b->seg_boundary_mask);
495 t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask,
496 b->virt_boundary_mask);
498 t->max_segments = min_not_zero(t->max_segments, b->max_segments);
499 t->max_discard_segments = min_not_zero(t->max_discard_segments,
500 b->max_discard_segments);
501 t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
502 b->max_integrity_segments);
504 t->max_segment_size = min_not_zero(t->max_segment_size,
505 b->max_segment_size);
507 t->misaligned |= b->misaligned;
509 alignment = queue_limit_alignment_offset(b, start);
511 /* Bottom device has different alignment. Check that it is
512 * compatible with the current top alignment.
514 if (t->alignment_offset != alignment) {
516 top = max(t->physical_block_size, t->io_min)
517 + t->alignment_offset;
518 bottom = max(b->physical_block_size, b->io_min) + alignment;
520 /* Verify that top and bottom intervals line up */
521 if (max(top, bottom) % min(top, bottom)) {
527 t->logical_block_size = max(t->logical_block_size,
528 b->logical_block_size);
530 t->physical_block_size = max(t->physical_block_size,
531 b->physical_block_size);
533 t->io_min = max(t->io_min, b->io_min);
534 t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
535 t->chunk_sectors = lcm_not_zero(t->chunk_sectors, b->chunk_sectors);
537 /* Physical block size a multiple of the logical block size? */
538 if (t->physical_block_size & (t->logical_block_size - 1)) {
539 t->physical_block_size = t->logical_block_size;
544 /* Minimum I/O a multiple of the physical block size? */
545 if (t->io_min & (t->physical_block_size - 1)) {
546 t->io_min = t->physical_block_size;
551 /* Optimal I/O a multiple of the physical block size? */
552 if (t->io_opt & (t->physical_block_size - 1)) {
558 /* chunk_sectors a multiple of the physical block size? */
559 if ((t->chunk_sectors << 9) & (t->physical_block_size - 1)) {
560 t->chunk_sectors = 0;
565 t->raid_partial_stripes_expensive =
566 max(t->raid_partial_stripes_expensive,
567 b->raid_partial_stripes_expensive);
569 /* Find lowest common alignment_offset */
570 t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
571 % max(t->physical_block_size, t->io_min);
573 /* Verify that new alignment_offset is on a logical block boundary */
574 if (t->alignment_offset & (t->logical_block_size - 1)) {
579 /* Discard alignment and granularity */
580 if (b->discard_granularity) {
581 alignment = queue_limit_discard_alignment(b, start);
583 if (t->discard_granularity != 0 &&
584 t->discard_alignment != alignment) {
585 top = t->discard_granularity + t->discard_alignment;
586 bottom = b->discard_granularity + alignment;
588 /* Verify that top and bottom intervals line up */
589 if ((max(top, bottom) % min(top, bottom)) != 0)
590 t->discard_misaligned = 1;
593 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
594 b->max_discard_sectors);
595 t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
596 b->max_hw_discard_sectors);
597 t->discard_granularity = max(t->discard_granularity,
598 b->discard_granularity);
599 t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
600 t->discard_granularity;
603 t->zoned = max(t->zoned, b->zoned);
606 EXPORT_SYMBOL(blk_stack_limits);
609 * disk_stack_limits - adjust queue limits for stacked drivers
610 * @disk: MD/DM gendisk (top)
611 * @bdev: the underlying block device (bottom)
612 * @offset: offset to beginning of data within component device
615 * Merges the limits for a top level gendisk and a bottom level
618 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
621 struct request_queue *t = disk->queue;
623 if (blk_stack_limits(&t->limits, &bdev_get_queue(bdev)->limits,
624 get_start_sect(bdev) + (offset >> 9)) < 0) {
625 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
627 disk_name(disk, 0, top);
628 bdevname(bdev, bottom);
630 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
634 t->backing_dev_info->io_pages =
635 t->limits.max_sectors >> (PAGE_SHIFT - 9);
637 EXPORT_SYMBOL(disk_stack_limits);
640 * blk_queue_update_dma_pad - update pad mask
641 * @q: the request queue for the device
644 * Update dma pad mask.
646 * Appending pad buffer to a request modifies the last entry of a
647 * scatter list such that it includes the pad buffer.
649 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
651 if (mask > q->dma_pad_mask)
652 q->dma_pad_mask = mask;
654 EXPORT_SYMBOL(blk_queue_update_dma_pad);
657 * blk_queue_segment_boundary - set boundary rules for segment merging
658 * @q: the request queue for the device
659 * @mask: the memory boundary mask
661 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
663 if (mask < PAGE_SIZE - 1) {
664 mask = PAGE_SIZE - 1;
665 printk(KERN_INFO "%s: set to minimum %lx\n",
669 q->limits.seg_boundary_mask = mask;
671 EXPORT_SYMBOL(blk_queue_segment_boundary);
674 * blk_queue_virt_boundary - set boundary rules for bio merging
675 * @q: the request queue for the device
676 * @mask: the memory boundary mask
678 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
680 q->limits.virt_boundary_mask = mask;
683 * Devices that require a virtual boundary do not support scatter/gather
684 * I/O natively, but instead require a descriptor list entry for each
685 * page (which might not be idential to the Linux PAGE_SIZE). Because
686 * of that they are not limited by our notion of "segment size".
689 q->limits.max_segment_size = UINT_MAX;
691 EXPORT_SYMBOL(blk_queue_virt_boundary);
694 * blk_queue_dma_alignment - set dma length and memory alignment
695 * @q: the request queue for the device
696 * @mask: alignment mask
699 * set required memory and length alignment for direct dma transactions.
700 * this is used when building direct io requests for the queue.
703 void blk_queue_dma_alignment(struct request_queue *q, int mask)
705 q->dma_alignment = mask;
707 EXPORT_SYMBOL(blk_queue_dma_alignment);
710 * blk_queue_update_dma_alignment - update dma length and memory alignment
711 * @q: the request queue for the device
712 * @mask: alignment mask
715 * update required memory and length alignment for direct dma transactions.
716 * If the requested alignment is larger than the current alignment, then
717 * the current queue alignment is updated to the new value, otherwise it
718 * is left alone. The design of this is to allow multiple objects
719 * (driver, device, transport etc) to set their respective
720 * alignments without having them interfere.
723 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
725 BUG_ON(mask > PAGE_SIZE);
727 if (mask > q->dma_alignment)
728 q->dma_alignment = mask;
730 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
733 * blk_set_queue_depth - tell the block layer about the device queue depth
734 * @q: the request queue for the device
735 * @depth: queue depth
738 void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
740 q->queue_depth = depth;
741 rq_qos_queue_depth_changed(q);
743 EXPORT_SYMBOL(blk_set_queue_depth);
746 * blk_queue_write_cache - configure queue's write cache
747 * @q: the request queue for the device
748 * @wc: write back cache on or off
749 * @fua: device supports FUA writes, if true
751 * Tell the block layer about the write cache of @q.
753 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
756 blk_queue_flag_set(QUEUE_FLAG_WC, q);
758 blk_queue_flag_clear(QUEUE_FLAG_WC, q);
760 blk_queue_flag_set(QUEUE_FLAG_FUA, q);
762 blk_queue_flag_clear(QUEUE_FLAG_FUA, q);
764 wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
766 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
769 * blk_queue_required_elevator_features - Set a queue required elevator features
770 * @q: the request queue for the target device
771 * @features: Required elevator features OR'ed together
773 * Tell the block layer that for the device controlled through @q, only the
774 * only elevators that can be used are those that implement at least the set of
775 * features specified by @features.
777 void blk_queue_required_elevator_features(struct request_queue *q,
778 unsigned int features)
780 q->required_elevator_features = features;
782 EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features);
785 * blk_queue_can_use_dma_map_merging - configure queue for merging segments.
786 * @q: the request queue for the device
787 * @dev: the device pointer for dma
789 * Tell the block layer about merging the segments by dma map of @q.
791 bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
794 unsigned long boundary = dma_get_merge_boundary(dev);
799 /* No need to update max_segment_size. see blk_queue_virt_boundary() */
800 blk_queue_virt_boundary(q, boundary);
804 EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
806 static int __init blk_settings_init(void)
808 blk_max_low_pfn = max_low_pfn - 1;
809 blk_max_pfn = max_pfn - 1;
812 subsys_initcall(blk_settings_init);