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>
18 unsigned long blk_max_low_pfn;
19 EXPORT_SYMBOL(blk_max_low_pfn);
21 unsigned long blk_max_pfn;
24 * blk_queue_prep_rq - set a prepare_request function for queue
26 * @pfn: prepare_request function
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.
34 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
38 EXPORT_SYMBOL(blk_queue_prep_rq);
41 * blk_queue_unprep_rq - set an unprepare_request function for queue
43 * @ufn: unprepare_request function
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.
51 void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn)
53 q->unprep_rq_fn = ufn;
55 EXPORT_SYMBOL(blk_queue_unprep_rq);
57 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
59 q->softirq_done_fn = fn;
61 EXPORT_SYMBOL(blk_queue_softirq_done);
63 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
65 q->rq_timeout = timeout;
67 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
69 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
71 q->rq_timed_out_fn = fn;
73 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
75 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
79 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
82 * blk_set_default_limits - reset limits to default values
83 * @lim: the queue_limits structure to reset
86 * Returns a queue_limit struct to its default state.
88 void blk_set_default_limits(struct queue_limits *lim)
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;
112 lim->zoned = BLK_ZONED_NONE;
114 EXPORT_SYMBOL(blk_set_default_limits);
117 * blk_set_stacking_limits - set default limits for stacking devices
118 * @lim: the queue_limits structure to reset
121 * Returns a queue_limit struct to its default state. Should be used
122 * by stacking drivers like DM that have no internal limits.
124 void blk_set_stacking_limits(struct queue_limits *lim)
126 blk_set_default_limits(lim);
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;
138 EXPORT_SYMBOL(blk_set_stacking_limits);
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
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().
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.
162 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
167 q->nr_requests = BLKDEV_MAX_RQ;
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;
174 blk_set_default_limits(&q->limits);
177 * by default assume old behaviour and bounce for any highmem page
179 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
181 EXPORT_SYMBOL(blk_queue_make_request);
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
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.
194 void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr)
196 unsigned long b_pfn = max_addr >> PAGE_SHIFT;
199 q->bounce_gfp = GFP_NOIO;
200 #if BITS_PER_LONG == 64
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.
206 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
208 q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
210 if (b_pfn < blk_max_low_pfn)
212 q->limits.bounce_pfn = b_pfn;
215 init_emergency_isa_pool();
216 q->bounce_gfp = GFP_NOIO | GFP_DMA;
217 q->limits.bounce_pfn = b_pfn;
220 EXPORT_SYMBOL(blk_queue_bounce_limit);
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
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
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.
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.
241 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
243 struct queue_limits *limits = &q->limits;
244 unsigned int max_sectors;
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);
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;
257 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
260 * blk_queue_chunk_sectors - set size of the chunk for this queue
261 * @q: the request queue for the device
262 * @chunk_sectors: chunk sectors in the usual 512b unit
265 * If a driver doesn't want IOs to cross a given chunk size, it can set
266 * this limit and prevent merging across chunks. Note that the chunk size
267 * must currently be a power-of-2 in sectors. Also note that the block
268 * layer must accept a page worth of data at any offset. So if the
269 * crossing of chunks is a hard limitation in the driver, it must still be
270 * prepared to split single page bios.
272 void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
274 BUG_ON(!is_power_of_2(chunk_sectors));
275 q->limits.chunk_sectors = chunk_sectors;
277 EXPORT_SYMBOL(blk_queue_chunk_sectors);
280 * blk_queue_max_discard_sectors - set max sectors for a single discard
281 * @q: the request queue for the device
282 * @max_discard_sectors: maximum number of sectors to discard
284 void blk_queue_max_discard_sectors(struct request_queue *q,
285 unsigned int max_discard_sectors)
287 q->limits.max_hw_discard_sectors = max_discard_sectors;
288 q->limits.max_discard_sectors = max_discard_sectors;
290 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
293 * blk_queue_max_write_same_sectors - set max sectors for a single write same
294 * @q: the request queue for the device
295 * @max_write_same_sectors: maximum number of sectors to write per command
297 void blk_queue_max_write_same_sectors(struct request_queue *q,
298 unsigned int max_write_same_sectors)
300 q->limits.max_write_same_sectors = max_write_same_sectors;
302 EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
305 * blk_queue_max_write_zeroes_sectors - set max sectors for a single
307 * @q: the request queue for the device
308 * @max_write_zeroes_sectors: maximum number of sectors to write per command
310 void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
311 unsigned int max_write_zeroes_sectors)
313 q->limits.max_write_zeroes_sectors = max_write_zeroes_sectors;
315 EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
318 * blk_queue_max_segments - set max hw segments for a request for this queue
319 * @q: the request queue for the device
320 * @max_segments: max number of segments
323 * Enables a low level driver to set an upper limit on the number of
324 * hw data segments in a request.
326 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
330 printk(KERN_INFO "%s: set to minimum %d\n",
331 __func__, max_segments);
334 q->limits.max_segments = max_segments;
336 EXPORT_SYMBOL(blk_queue_max_segments);
339 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
340 * @q: the request queue for the device
341 * @max_size: max size of segment in bytes
344 * Enables a low level driver to set an upper limit on the size of a
347 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
349 if (max_size < PAGE_SIZE) {
350 max_size = PAGE_SIZE;
351 printk(KERN_INFO "%s: set to minimum %d\n",
355 q->limits.max_segment_size = max_size;
357 EXPORT_SYMBOL(blk_queue_max_segment_size);
360 * blk_queue_logical_block_size - set logical block size for the queue
361 * @q: the request queue for the device
362 * @size: the logical block size, in bytes
365 * This should be set to the lowest possible block size that the
366 * storage device can address. The default of 512 covers most
369 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
371 q->limits.logical_block_size = size;
373 if (q->limits.physical_block_size < size)
374 q->limits.physical_block_size = size;
376 if (q->limits.io_min < q->limits.physical_block_size)
377 q->limits.io_min = q->limits.physical_block_size;
379 EXPORT_SYMBOL(blk_queue_logical_block_size);
382 * blk_queue_physical_block_size - set physical block size for the queue
383 * @q: the request queue for the device
384 * @size: the physical block size, in bytes
387 * This should be set to the lowest possible sector size that the
388 * hardware can operate on without reverting to read-modify-write
391 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
393 q->limits.physical_block_size = size;
395 if (q->limits.physical_block_size < q->limits.logical_block_size)
396 q->limits.physical_block_size = q->limits.logical_block_size;
398 if (q->limits.io_min < q->limits.physical_block_size)
399 q->limits.io_min = q->limits.physical_block_size;
401 EXPORT_SYMBOL(blk_queue_physical_block_size);
404 * blk_queue_alignment_offset - set physical block alignment offset
405 * @q: the request queue for the device
406 * @offset: alignment offset in bytes
409 * Some devices are naturally misaligned to compensate for things like
410 * the legacy DOS partition table 63-sector offset. Low-level drivers
411 * should call this function for devices whose first sector is not
414 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
416 q->limits.alignment_offset =
417 offset & (q->limits.physical_block_size - 1);
418 q->limits.misaligned = 0;
420 EXPORT_SYMBOL(blk_queue_alignment_offset);
423 * blk_limits_io_min - set minimum request size for a device
424 * @limits: the queue limits
425 * @min: smallest I/O size in bytes
428 * Some devices have an internal block size bigger than the reported
429 * hardware sector size. This function can be used to signal the
430 * smallest I/O the device can perform without incurring a performance
433 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
435 limits->io_min = min;
437 if (limits->io_min < limits->logical_block_size)
438 limits->io_min = limits->logical_block_size;
440 if (limits->io_min < limits->physical_block_size)
441 limits->io_min = limits->physical_block_size;
443 EXPORT_SYMBOL(blk_limits_io_min);
446 * blk_queue_io_min - set minimum request size for the queue
447 * @q: the request queue for the device
448 * @min: smallest I/O size in bytes
451 * Storage devices may report a granularity or preferred minimum I/O
452 * size which is the smallest request the device can perform without
453 * incurring a performance penalty. For disk drives this is often the
454 * physical block size. For RAID arrays it is often the stripe chunk
455 * size. A properly aligned multiple of minimum_io_size is the
456 * preferred request size for workloads where a high number of I/O
457 * operations is desired.
459 void blk_queue_io_min(struct request_queue *q, unsigned int min)
461 blk_limits_io_min(&q->limits, min);
463 EXPORT_SYMBOL(blk_queue_io_min);
466 * blk_limits_io_opt - set optimal request size for a device
467 * @limits: the queue limits
468 * @opt: smallest I/O size in bytes
471 * Storage devices may report an optimal I/O size, which is the
472 * device's preferred unit for sustained I/O. This is rarely reported
473 * for disk drives. For RAID arrays it is usually the stripe width or
474 * the internal track size. A properly aligned multiple of
475 * optimal_io_size is the preferred request size for workloads where
476 * sustained throughput is desired.
478 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
480 limits->io_opt = opt;
482 EXPORT_SYMBOL(blk_limits_io_opt);
485 * blk_queue_io_opt - set optimal request size for the queue
486 * @q: the request queue for the device
487 * @opt: optimal request size in bytes
490 * Storage devices may report an optimal I/O size, which is the
491 * device's preferred unit for sustained I/O. This is rarely reported
492 * for disk drives. For RAID arrays it is usually the stripe width or
493 * the internal track size. A properly aligned multiple of
494 * optimal_io_size is the preferred request size for workloads where
495 * sustained throughput is desired.
497 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
499 blk_limits_io_opt(&q->limits, opt);
501 EXPORT_SYMBOL(blk_queue_io_opt);
504 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
505 * @t: the stacking driver (top)
506 * @b: the underlying device (bottom)
508 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
510 blk_stack_limits(&t->limits, &b->limits, 0);
512 EXPORT_SYMBOL(blk_queue_stack_limits);
515 * blk_stack_limits - adjust queue_limits for stacked devices
516 * @t: the stacking driver limits (top device)
517 * @b: the underlying queue limits (bottom, component device)
518 * @start: first data sector within component device
521 * This function is used by stacking drivers like MD and DM to ensure
522 * that all component devices have compatible block sizes and
523 * alignments. The stacking driver must provide a queue_limits
524 * struct (top) and then iteratively call the stacking function for
525 * all component (bottom) devices. The stacking function will
526 * attempt to combine the values and ensure proper alignment.
528 * Returns 0 if the top and bottom queue_limits are compatible. The
529 * top device's block sizes and alignment offsets may be adjusted to
530 * ensure alignment with the bottom device. If no compatible sizes
531 * and alignments exist, -1 is returned and the resulting top
532 * queue_limits will have the misaligned flag set to indicate that
533 * the alignment_offset is undefined.
535 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
538 unsigned int top, bottom, alignment, ret = 0;
540 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
541 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
542 t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
543 t->max_write_same_sectors = min(t->max_write_same_sectors,
544 b->max_write_same_sectors);
545 t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors,
546 b->max_write_zeroes_sectors);
547 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
549 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
550 b->seg_boundary_mask);
551 t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask,
552 b->virt_boundary_mask);
554 t->max_segments = min_not_zero(t->max_segments, b->max_segments);
555 t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
556 b->max_integrity_segments);
558 t->max_segment_size = min_not_zero(t->max_segment_size,
559 b->max_segment_size);
561 t->misaligned |= b->misaligned;
563 alignment = queue_limit_alignment_offset(b, start);
565 /* Bottom device has different alignment. Check that it is
566 * compatible with the current top alignment.
568 if (t->alignment_offset != alignment) {
570 top = max(t->physical_block_size, t->io_min)
571 + t->alignment_offset;
572 bottom = max(b->physical_block_size, b->io_min) + alignment;
574 /* Verify that top and bottom intervals line up */
575 if (max(top, bottom) % min(top, bottom)) {
581 t->logical_block_size = max(t->logical_block_size,
582 b->logical_block_size);
584 t->physical_block_size = max(t->physical_block_size,
585 b->physical_block_size);
587 t->io_min = max(t->io_min, b->io_min);
588 t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
590 t->cluster &= b->cluster;
591 t->discard_zeroes_data &= b->discard_zeroes_data;
593 /* Physical block size a multiple of the logical block size? */
594 if (t->physical_block_size & (t->logical_block_size - 1)) {
595 t->physical_block_size = t->logical_block_size;
600 /* Minimum I/O a multiple of the physical block size? */
601 if (t->io_min & (t->physical_block_size - 1)) {
602 t->io_min = t->physical_block_size;
607 /* Optimal I/O a multiple of the physical block size? */
608 if (t->io_opt & (t->physical_block_size - 1)) {
614 t->raid_partial_stripes_expensive =
615 max(t->raid_partial_stripes_expensive,
616 b->raid_partial_stripes_expensive);
618 /* Find lowest common alignment_offset */
619 t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
620 % max(t->physical_block_size, t->io_min);
622 /* Verify that new alignment_offset is on a logical block boundary */
623 if (t->alignment_offset & (t->logical_block_size - 1)) {
628 /* Discard alignment and granularity */
629 if (b->discard_granularity) {
630 alignment = queue_limit_discard_alignment(b, start);
632 if (t->discard_granularity != 0 &&
633 t->discard_alignment != alignment) {
634 top = t->discard_granularity + t->discard_alignment;
635 bottom = b->discard_granularity + alignment;
637 /* Verify that top and bottom intervals line up */
638 if ((max(top, bottom) % min(top, bottom)) != 0)
639 t->discard_misaligned = 1;
642 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
643 b->max_discard_sectors);
644 t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
645 b->max_hw_discard_sectors);
646 t->discard_granularity = max(t->discard_granularity,
647 b->discard_granularity);
648 t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
649 t->discard_granularity;
652 if (b->chunk_sectors)
653 t->chunk_sectors = min_not_zero(t->chunk_sectors,
658 EXPORT_SYMBOL(blk_stack_limits);
661 * bdev_stack_limits - adjust queue limits for stacked drivers
662 * @t: the stacking driver limits (top device)
663 * @bdev: the component block_device (bottom)
664 * @start: first data sector within component device
667 * Merges queue limits for a top device and a block_device. Returns
668 * 0 if alignment didn't change. Returns -1 if adding the bottom
669 * device caused misalignment.
671 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
674 struct request_queue *bq = bdev_get_queue(bdev);
676 start += get_start_sect(bdev);
678 return blk_stack_limits(t, &bq->limits, start);
680 EXPORT_SYMBOL(bdev_stack_limits);
683 * disk_stack_limits - adjust queue limits for stacked drivers
684 * @disk: MD/DM gendisk (top)
685 * @bdev: the underlying block device (bottom)
686 * @offset: offset to beginning of data within component device
689 * Merges the limits for a top level gendisk and a bottom level
692 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
695 struct request_queue *t = disk->queue;
697 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
698 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
700 disk_name(disk, 0, top);
701 bdevname(bdev, bottom);
703 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
707 EXPORT_SYMBOL(disk_stack_limits);
710 * blk_queue_dma_pad - set pad mask
711 * @q: the request queue for the device
716 * Appending pad buffer to a request modifies the last entry of a
717 * scatter list such that it includes the pad buffer.
719 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
721 q->dma_pad_mask = mask;
723 EXPORT_SYMBOL(blk_queue_dma_pad);
726 * blk_queue_update_dma_pad - update pad mask
727 * @q: the request queue for the device
730 * Update dma pad mask.
732 * Appending pad buffer to a request modifies the last entry of a
733 * scatter list such that it includes the pad buffer.
735 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
737 if (mask > q->dma_pad_mask)
738 q->dma_pad_mask = mask;
740 EXPORT_SYMBOL(blk_queue_update_dma_pad);
743 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
744 * @q: the request queue for the device
745 * @dma_drain_needed: fn which returns non-zero if drain is necessary
746 * @buf: physically contiguous buffer
747 * @size: size of the buffer in bytes
749 * Some devices have excess DMA problems and can't simply discard (or
750 * zero fill) the unwanted piece of the transfer. They have to have a
751 * real area of memory to transfer it into. The use case for this is
752 * ATAPI devices in DMA mode. If the packet command causes a transfer
753 * bigger than the transfer size some HBAs will lock up if there
754 * aren't DMA elements to contain the excess transfer. What this API
755 * does is adjust the queue so that the buf is always appended
756 * silently to the scatterlist.
758 * Note: This routine adjusts max_hw_segments to make room for appending
759 * the drain buffer. If you call blk_queue_max_segments() after calling
760 * this routine, you must set the limit to one fewer than your device
761 * can support otherwise there won't be room for the drain buffer.
763 int blk_queue_dma_drain(struct request_queue *q,
764 dma_drain_needed_fn *dma_drain_needed,
765 void *buf, unsigned int size)
767 if (queue_max_segments(q) < 2)
769 /* make room for appending the drain */
770 blk_queue_max_segments(q, queue_max_segments(q) - 1);
771 q->dma_drain_needed = dma_drain_needed;
772 q->dma_drain_buffer = buf;
773 q->dma_drain_size = size;
777 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
780 * blk_queue_segment_boundary - set boundary rules for segment merging
781 * @q: the request queue for the device
782 * @mask: the memory boundary mask
784 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
786 if (mask < PAGE_SIZE - 1) {
787 mask = PAGE_SIZE - 1;
788 printk(KERN_INFO "%s: set to minimum %lx\n",
792 q->limits.seg_boundary_mask = mask;
794 EXPORT_SYMBOL(blk_queue_segment_boundary);
797 * blk_queue_virt_boundary - set boundary rules for bio merging
798 * @q: the request queue for the device
799 * @mask: the memory boundary mask
801 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
803 q->limits.virt_boundary_mask = mask;
805 EXPORT_SYMBOL(blk_queue_virt_boundary);
808 * blk_queue_dma_alignment - set dma length and memory alignment
809 * @q: the request queue for the device
810 * @mask: alignment mask
813 * set required memory and length alignment for direct dma transactions.
814 * this is used when building direct io requests for the queue.
817 void blk_queue_dma_alignment(struct request_queue *q, int mask)
819 q->dma_alignment = mask;
821 EXPORT_SYMBOL(blk_queue_dma_alignment);
824 * blk_queue_update_dma_alignment - update dma length and memory alignment
825 * @q: the request queue for the device
826 * @mask: alignment mask
829 * update required memory and length alignment for direct dma transactions.
830 * If the requested alignment is larger than the current alignment, then
831 * the current queue alignment is updated to the new value, otherwise it
832 * is left alone. The design of this is to allow multiple objects
833 * (driver, device, transport etc) to set their respective
834 * alignments without having them interfere.
837 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
839 BUG_ON(mask > PAGE_SIZE);
841 if (mask > q->dma_alignment)
842 q->dma_alignment = mask;
844 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
846 void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
848 spin_lock_irq(q->queue_lock);
850 clear_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
852 set_bit(QUEUE_FLAG_FLUSH_NQ, &q->queue_flags);
853 spin_unlock_irq(q->queue_lock);
855 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
858 * blk_set_queue_depth - tell the block layer about the device queue depth
859 * @q: the request queue for the device
860 * @depth: queue depth
863 void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
865 q->queue_depth = depth;
866 wbt_set_queue_depth(q->rq_wb, depth);
868 EXPORT_SYMBOL(blk_set_queue_depth);
871 * blk_queue_write_cache - configure queue's write cache
872 * @q: the request queue for the device
873 * @wc: write back cache on or off
874 * @fua: device supports FUA writes, if true
876 * Tell the block layer about the write cache of @q.
878 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
880 spin_lock_irq(q->queue_lock);
882 queue_flag_set(QUEUE_FLAG_WC, q);
884 queue_flag_clear(QUEUE_FLAG_WC, q);
886 queue_flag_set(QUEUE_FLAG_FUA, q);
888 queue_flag_clear(QUEUE_FLAG_FUA, q);
889 spin_unlock_irq(q->queue_lock);
891 wbt_set_write_cache(q->rq_wb, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
893 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
895 static int __init blk_settings_init(void)
897 blk_max_low_pfn = max_low_pfn - 1;
898 blk_max_pfn = max_pfn - 1;
901 subsys_initcall(blk_settings_init);