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.
109 void blk_set_default_limits(struct queue_limits *lim)
111 lim->max_segments = BLK_MAX_SEGMENTS;
112 lim->max_integrity_segments = 0;
113 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
114 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
115 lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
116 lim->max_discard_sectors = 0;
117 lim->discard_granularity = 0;
118 lim->discard_alignment = 0;
119 lim->discard_misaligned = 0;
120 lim->discard_zeroes_data = 0;
121 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
122 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
123 lim->alignment_offset = 0;
128 EXPORT_SYMBOL(blk_set_default_limits);
131 * blk_set_stacking_limits - set default limits for stacking devices
132 * @lim: the queue_limits structure to reset
135 * Returns a queue_limit struct to its default state. Should be used
136 * by stacking drivers like DM that have no internal limits.
138 void blk_set_stacking_limits(struct queue_limits *lim)
140 blk_set_default_limits(lim);
142 /* Inherit limits from component devices */
143 lim->discard_zeroes_data = 1;
144 lim->max_segments = USHRT_MAX;
145 lim->max_hw_sectors = UINT_MAX;
147 lim->max_sectors = BLK_DEF_MAX_SECTORS;
149 EXPORT_SYMBOL(blk_set_stacking_limits);
152 * blk_queue_make_request - define an alternate make_request function for a device
153 * @q: the request queue for the device to be affected
154 * @mfn: the alternate make_request function
157 * The normal way for &struct bios to be passed to a device
158 * driver is for them to be collected into requests on a request
159 * queue, and then to allow the device driver to select requests
160 * off that queue when it is ready. This works well for many block
161 * devices. However some block devices (typically virtual devices
162 * such as md or lvm) do not benefit from the processing on the
163 * request queue, and are served best by having the requests passed
164 * directly to them. This can be achieved by providing a function
165 * to blk_queue_make_request().
168 * The driver that does this *must* be able to deal appropriately
169 * with buffers in "highmemory". This can be accomplished by either calling
170 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
171 * blk_queue_bounce() to create a buffer in normal memory.
173 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
178 q->nr_requests = BLKDEV_MAX_RQ;
180 q->make_request_fn = mfn;
181 blk_queue_dma_alignment(q, 511);
182 blk_queue_congestion_threshold(q);
183 q->nr_batching = BLK_BATCH_REQ;
185 blk_set_default_limits(&q->limits);
188 * by default assume old behaviour and bounce for any highmem page
190 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
192 EXPORT_SYMBOL(blk_queue_make_request);
195 * blk_queue_bounce_limit - set bounce buffer limit for queue
196 * @q: the request queue for the device
197 * @dma_mask: the maximum address the device can handle
200 * Different hardware can have different requirements as to what pages
201 * it can do I/O directly to. A low level driver can call
202 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
203 * buffers for doing I/O to pages residing above @dma_mask.
205 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
207 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
210 q->bounce_gfp = GFP_NOIO;
211 #if BITS_PER_LONG == 64
213 * Assume anything <= 4GB can be handled by IOMMU. Actually
214 * some IOMMUs can handle everything, but I don't know of a
215 * way to test this here.
217 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
219 q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
221 if (b_pfn < blk_max_low_pfn)
223 q->limits.bounce_pfn = b_pfn;
226 init_emergency_isa_pool();
227 q->bounce_gfp = GFP_NOIO | GFP_DMA;
228 q->limits.bounce_pfn = b_pfn;
231 EXPORT_SYMBOL(blk_queue_bounce_limit);
234 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
235 * @limits: the queue limits
236 * @max_hw_sectors: max hardware sectors in the usual 512b unit
239 * Enables a low level driver to set a hard upper limit,
240 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
241 * the device driver based upon the combined capabilities of I/O
242 * controller and storage device.
244 * max_sectors is a soft limit imposed by the block layer for
245 * filesystem type requests. This value can be overridden on a
246 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
247 * The soft limit can not exceed max_hw_sectors.
249 void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
251 if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
252 max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
253 printk(KERN_INFO "%s: set to minimum %d\n",
254 __func__, max_hw_sectors);
257 limits->max_hw_sectors = max_hw_sectors;
258 limits->max_sectors = min_t(unsigned int, max_hw_sectors,
259 BLK_DEF_MAX_SECTORS);
261 EXPORT_SYMBOL(blk_limits_max_hw_sectors);
264 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
265 * @q: the request queue for the device
266 * @max_hw_sectors: max hardware sectors in the usual 512b unit
269 * See description for blk_limits_max_hw_sectors().
271 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
273 blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
275 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
278 * blk_queue_max_discard_sectors - set max sectors for a single discard
279 * @q: the request queue for the device
280 * @max_discard_sectors: maximum number of sectors to discard
282 void blk_queue_max_discard_sectors(struct request_queue *q,
283 unsigned int max_discard_sectors)
285 q->limits.max_discard_sectors = max_discard_sectors;
287 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
290 * blk_queue_max_segments - set max hw segments for a request for this queue
291 * @q: the request queue for the device
292 * @max_segments: max number of segments
295 * Enables a low level driver to set an upper limit on the number of
296 * hw data segments in a request.
298 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
302 printk(KERN_INFO "%s: set to minimum %d\n",
303 __func__, max_segments);
306 q->limits.max_segments = max_segments;
308 EXPORT_SYMBOL(blk_queue_max_segments);
311 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
312 * @q: the request queue for the device
313 * @max_size: max size of segment in bytes
316 * Enables a low level driver to set an upper limit on the size of a
319 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
321 if (max_size < PAGE_CACHE_SIZE) {
322 max_size = PAGE_CACHE_SIZE;
323 printk(KERN_INFO "%s: set to minimum %d\n",
327 q->limits.max_segment_size = max_size;
329 EXPORT_SYMBOL(blk_queue_max_segment_size);
332 * blk_queue_logical_block_size - set logical block size for the queue
333 * @q: the request queue for the device
334 * @size: the logical block size, in bytes
337 * This should be set to the lowest possible block size that the
338 * storage device can address. The default of 512 covers most
341 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
343 q->limits.logical_block_size = size;
345 if (q->limits.physical_block_size < size)
346 q->limits.physical_block_size = size;
348 if (q->limits.io_min < q->limits.physical_block_size)
349 q->limits.io_min = q->limits.physical_block_size;
351 EXPORT_SYMBOL(blk_queue_logical_block_size);
354 * blk_queue_physical_block_size - set physical block size for the queue
355 * @q: the request queue for the device
356 * @size: the physical block size, in bytes
359 * This should be set to the lowest possible sector size that the
360 * hardware can operate on without reverting to read-modify-write
363 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
365 q->limits.physical_block_size = size;
367 if (q->limits.physical_block_size < q->limits.logical_block_size)
368 q->limits.physical_block_size = q->limits.logical_block_size;
370 if (q->limits.io_min < q->limits.physical_block_size)
371 q->limits.io_min = q->limits.physical_block_size;
373 EXPORT_SYMBOL(blk_queue_physical_block_size);
376 * blk_queue_alignment_offset - set physical block alignment offset
377 * @q: the request queue for the device
378 * @offset: alignment offset in bytes
381 * Some devices are naturally misaligned to compensate for things like
382 * the legacy DOS partition table 63-sector offset. Low-level drivers
383 * should call this function for devices whose first sector is not
386 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
388 q->limits.alignment_offset =
389 offset & (q->limits.physical_block_size - 1);
390 q->limits.misaligned = 0;
392 EXPORT_SYMBOL(blk_queue_alignment_offset);
395 * blk_limits_io_min - set minimum request size for a device
396 * @limits: the queue limits
397 * @min: smallest I/O size in bytes
400 * Some devices have an internal block size bigger than the reported
401 * hardware sector size. This function can be used to signal the
402 * smallest I/O the device can perform without incurring a performance
405 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
407 limits->io_min = min;
409 if (limits->io_min < limits->logical_block_size)
410 limits->io_min = limits->logical_block_size;
412 if (limits->io_min < limits->physical_block_size)
413 limits->io_min = limits->physical_block_size;
415 EXPORT_SYMBOL(blk_limits_io_min);
418 * blk_queue_io_min - set minimum request size for the queue
419 * @q: the request queue for the device
420 * @min: smallest I/O size in bytes
423 * Storage devices may report a granularity or preferred minimum I/O
424 * size which is the smallest request the device can perform without
425 * incurring a performance penalty. For disk drives this is often the
426 * physical block size. For RAID arrays it is often the stripe chunk
427 * size. A properly aligned multiple of minimum_io_size is the
428 * preferred request size for workloads where a high number of I/O
429 * operations is desired.
431 void blk_queue_io_min(struct request_queue *q, unsigned int min)
433 blk_limits_io_min(&q->limits, min);
435 EXPORT_SYMBOL(blk_queue_io_min);
438 * blk_limits_io_opt - set optimal request size for a device
439 * @limits: the queue limits
440 * @opt: smallest I/O size in bytes
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_limits_io_opt(struct queue_limits *limits, unsigned int opt)
452 limits->io_opt = opt;
454 EXPORT_SYMBOL(blk_limits_io_opt);
457 * blk_queue_io_opt - set optimal request size for the queue
458 * @q: the request queue for the device
459 * @opt: optimal request size in bytes
462 * Storage devices may report an optimal I/O size, which is the
463 * device's preferred unit for sustained I/O. This is rarely reported
464 * for disk drives. For RAID arrays it is usually the stripe width or
465 * the internal track size. A properly aligned multiple of
466 * optimal_io_size is the preferred request size for workloads where
467 * sustained throughput is desired.
469 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
471 blk_limits_io_opt(&q->limits, opt);
473 EXPORT_SYMBOL(blk_queue_io_opt);
476 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
477 * @t: the stacking driver (top)
478 * @b: the underlying device (bottom)
480 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
482 blk_stack_limits(&t->limits, &b->limits, 0);
484 EXPORT_SYMBOL(blk_queue_stack_limits);
487 * blk_stack_limits - adjust queue_limits for stacked devices
488 * @t: the stacking driver limits (top device)
489 * @b: the underlying queue limits (bottom, component device)
490 * @start: first data sector within component device
493 * This function is used by stacking drivers like MD and DM to ensure
494 * that all component devices have compatible block sizes and
495 * alignments. The stacking driver must provide a queue_limits
496 * struct (top) and then iteratively call the stacking function for
497 * all component (bottom) devices. The stacking function will
498 * attempt to combine the values and ensure proper alignment.
500 * Returns 0 if the top and bottom queue_limits are compatible. The
501 * top device's block sizes and alignment offsets may be adjusted to
502 * ensure alignment with the bottom device. If no compatible sizes
503 * and alignments exist, -1 is returned and the resulting top
504 * queue_limits will have the misaligned flag set to indicate that
505 * the alignment_offset is undefined.
507 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
510 unsigned int top, bottom, alignment, ret = 0;
512 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
513 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
514 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
516 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
517 b->seg_boundary_mask);
519 t->max_segments = min_not_zero(t->max_segments, b->max_segments);
520 t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
521 b->max_integrity_segments);
523 t->max_segment_size = min_not_zero(t->max_segment_size,
524 b->max_segment_size);
526 t->misaligned |= b->misaligned;
528 alignment = queue_limit_alignment_offset(b, start);
530 /* Bottom device has different alignment. Check that it is
531 * compatible with the current top alignment.
533 if (t->alignment_offset != alignment) {
535 top = max(t->physical_block_size, t->io_min)
536 + t->alignment_offset;
537 bottom = max(b->physical_block_size, b->io_min) + alignment;
539 /* Verify that top and bottom intervals line up */
540 if (max(top, bottom) & (min(top, bottom) - 1)) {
546 t->logical_block_size = max(t->logical_block_size,
547 b->logical_block_size);
549 t->physical_block_size = max(t->physical_block_size,
550 b->physical_block_size);
552 t->io_min = max(t->io_min, b->io_min);
553 t->io_opt = lcm(t->io_opt, b->io_opt);
555 t->cluster &= b->cluster;
556 t->discard_zeroes_data &= b->discard_zeroes_data;
558 /* Physical block size a multiple of the logical block size? */
559 if (t->physical_block_size & (t->logical_block_size - 1)) {
560 t->physical_block_size = t->logical_block_size;
565 /* Minimum I/O a multiple of the physical block size? */
566 if (t->io_min & (t->physical_block_size - 1)) {
567 t->io_min = t->physical_block_size;
572 /* Optimal I/O a multiple of the physical block size? */
573 if (t->io_opt & (t->physical_block_size - 1)) {
579 /* Find lowest common alignment_offset */
580 t->alignment_offset = lcm(t->alignment_offset, alignment)
581 & (max(t->physical_block_size, t->io_min) - 1);
583 /* Verify that new alignment_offset is on a logical block boundary */
584 if (t->alignment_offset & (t->logical_block_size - 1)) {
589 /* Discard alignment and granularity */
590 if (b->discard_granularity) {
591 alignment = queue_limit_discard_alignment(b, start);
593 if (t->discard_granularity != 0 &&
594 t->discard_alignment != alignment) {
595 top = t->discard_granularity + t->discard_alignment;
596 bottom = b->discard_granularity + alignment;
598 /* Verify that top and bottom intervals line up */
599 if (max(top, bottom) & (min(top, bottom) - 1))
600 t->discard_misaligned = 1;
603 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
604 b->max_discard_sectors);
605 t->discard_granularity = max(t->discard_granularity,
606 b->discard_granularity);
607 t->discard_alignment = lcm(t->discard_alignment, alignment) &
608 (t->discard_granularity - 1);
613 EXPORT_SYMBOL(blk_stack_limits);
616 * bdev_stack_limits - adjust queue limits for stacked drivers
617 * @t: the stacking driver limits (top device)
618 * @bdev: the component block_device (bottom)
619 * @start: first data sector within component device
622 * Merges queue limits for a top device and a block_device. Returns
623 * 0 if alignment didn't change. Returns -1 if adding the bottom
624 * device caused misalignment.
626 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
629 struct request_queue *bq = bdev_get_queue(bdev);
631 start += get_start_sect(bdev);
633 return blk_stack_limits(t, &bq->limits, start);
635 EXPORT_SYMBOL(bdev_stack_limits);
638 * disk_stack_limits - adjust queue limits for stacked drivers
639 * @disk: MD/DM gendisk (top)
640 * @bdev: the underlying block device (bottom)
641 * @offset: offset to beginning of data within component device
644 * Merges the limits for a top level gendisk and a bottom level
647 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
650 struct request_queue *t = disk->queue;
652 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
653 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
655 disk_name(disk, 0, top);
656 bdevname(bdev, bottom);
658 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
662 EXPORT_SYMBOL(disk_stack_limits);
665 * blk_queue_dma_pad - set pad mask
666 * @q: the request queue for the device
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_dma_pad(struct request_queue *q, unsigned int mask)
676 q->dma_pad_mask = mask;
678 EXPORT_SYMBOL(blk_queue_dma_pad);
681 * blk_queue_update_dma_pad - update pad mask
682 * @q: the request queue for the device
685 * Update dma pad mask.
687 * Appending pad buffer to a request modifies the last entry of a
688 * scatter list such that it includes the pad buffer.
690 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
692 if (mask > q->dma_pad_mask)
693 q->dma_pad_mask = mask;
695 EXPORT_SYMBOL(blk_queue_update_dma_pad);
698 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
699 * @q: the request queue for the device
700 * @dma_drain_needed: fn which returns non-zero if drain is necessary
701 * @buf: physically contiguous buffer
702 * @size: size of the buffer in bytes
704 * Some devices have excess DMA problems and can't simply discard (or
705 * zero fill) the unwanted piece of the transfer. They have to have a
706 * real area of memory to transfer it into. The use case for this is
707 * ATAPI devices in DMA mode. If the packet command causes a transfer
708 * bigger than the transfer size some HBAs will lock up if there
709 * aren't DMA elements to contain the excess transfer. What this API
710 * does is adjust the queue so that the buf is always appended
711 * silently to the scatterlist.
713 * Note: This routine adjusts max_hw_segments to make room for appending
714 * the drain buffer. If you call blk_queue_max_segments() after calling
715 * this routine, you must set the limit to one fewer than your device
716 * can support otherwise there won't be room for the drain buffer.
718 int blk_queue_dma_drain(struct request_queue *q,
719 dma_drain_needed_fn *dma_drain_needed,
720 void *buf, unsigned int size)
722 if (queue_max_segments(q) < 2)
724 /* make room for appending the drain */
725 blk_queue_max_segments(q, queue_max_segments(q) - 1);
726 q->dma_drain_needed = dma_drain_needed;
727 q->dma_drain_buffer = buf;
728 q->dma_drain_size = size;
732 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
735 * blk_queue_segment_boundary - set boundary rules for segment merging
736 * @q: the request queue for the device
737 * @mask: the memory boundary mask
739 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
741 if (mask < PAGE_CACHE_SIZE - 1) {
742 mask = PAGE_CACHE_SIZE - 1;
743 printk(KERN_INFO "%s: set to minimum %lx\n",
747 q->limits.seg_boundary_mask = mask;
749 EXPORT_SYMBOL(blk_queue_segment_boundary);
752 * blk_queue_dma_alignment - set dma length and memory alignment
753 * @q: the request queue for the device
754 * @mask: alignment mask
757 * set required memory and length alignment for direct dma transactions.
758 * this is used when building direct io requests for the queue.
761 void blk_queue_dma_alignment(struct request_queue *q, int mask)
763 q->dma_alignment = mask;
765 EXPORT_SYMBOL(blk_queue_dma_alignment);
768 * blk_queue_update_dma_alignment - update dma length and memory alignment
769 * @q: the request queue for the device
770 * @mask: alignment mask
773 * update required memory and length alignment for direct dma transactions.
774 * If the requested alignment is larger than the current alignment, then
775 * the current queue alignment is updated to the new value, otherwise it
776 * is left alone. The design of this is to allow multiple objects
777 * (driver, device, transport etc) to set their respective
778 * alignments without having them interfere.
781 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
783 BUG_ON(mask > PAGE_SIZE);
785 if (mask > q->dma_alignment)
786 q->dma_alignment = mask;
788 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
791 * blk_queue_flush - configure queue's cache flush capability
792 * @q: the request queue for the device
793 * @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
795 * Tell block layer cache flush capability of @q. If it supports
796 * flushing, REQ_FLUSH should be set. If it supports bypassing
797 * write cache for individual writes, REQ_FUA should be set.
799 void blk_queue_flush(struct request_queue *q, unsigned int flush)
801 WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
803 if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
806 q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
808 EXPORT_SYMBOL_GPL(blk_queue_flush);
810 void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
812 q->flush_not_queueable = !queueable;
814 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
816 static int __init blk_settings_init(void)
818 blk_max_low_pfn = max_low_pfn - 1;
819 blk_max_pfn = max_pfn - 1;
822 subsys_initcall(blk_settings_init);