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/jiffies.h>
15 unsigned long blk_max_low_pfn;
16 EXPORT_SYMBOL(blk_max_low_pfn);
18 unsigned long blk_max_pfn;
21 * blk_queue_prep_rq - set a prepare_request function for queue
23 * @pfn: prepare_request function
25 * It's possible for a queue to register a prepare_request callback which
26 * is invoked before the request is handed to the request_fn. The goal of
27 * the function is to prepare a request for I/O, it can be used to build a
28 * cdb from the request data for instance.
31 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
35 EXPORT_SYMBOL(blk_queue_prep_rq);
38 * blk_queue_merge_bvec - set a merge_bvec function for queue
40 * @mbfn: merge_bvec_fn
42 * Usually queues have static limitations on the max sectors or segments that
43 * we can put in a request. Stacking drivers may have some settings that
44 * are dynamic, and thus we have to query the queue whether it is ok to
45 * add a new bio_vec to a bio at a given offset or not. If the block device
46 * has such limitations, it needs to register a merge_bvec_fn to control
47 * the size of bio's sent to it. Note that a block device *must* allow a
48 * single page to be added to an empty bio. The block device driver may want
49 * to use the bio_split() function to deal with these bio's. By default
50 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
53 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
55 q->merge_bvec_fn = mbfn;
57 EXPORT_SYMBOL(blk_queue_merge_bvec);
59 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
61 q->softirq_done_fn = fn;
63 EXPORT_SYMBOL(blk_queue_softirq_done);
65 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
67 q->rq_timeout = timeout;
69 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
71 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
73 q->rq_timed_out_fn = fn;
75 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
77 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
81 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
84 * blk_set_default_limits - reset limits to default values
85 * @lim: the queue_limits structure to reset
88 * Returns a queue_limit struct to its default state. Can be used by
89 * stacking drivers like DM that stage table swaps and reuse an
90 * existing device queue.
92 void blk_set_default_limits(struct queue_limits *lim)
94 lim->max_phys_segments = MAX_PHYS_SEGMENTS;
95 lim->max_hw_segments = MAX_HW_SEGMENTS;
96 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
97 lim->max_segment_size = MAX_SEGMENT_SIZE;
98 lim->max_sectors = BLK_DEF_MAX_SECTORS;
99 lim->max_hw_sectors = INT_MAX;
100 lim->max_discard_sectors = 0;
101 lim->discard_granularity = 0;
102 lim->discard_alignment = 0;
103 lim->discard_misaligned = 0;
104 lim->discard_zeroes_data = -1;
105 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
106 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
107 lim->alignment_offset = 0;
112 EXPORT_SYMBOL(blk_set_default_limits);
115 * blk_queue_make_request - define an alternate make_request function for a device
116 * @q: the request queue for the device to be affected
117 * @mfn: the alternate make_request function
120 * The normal way for &struct bios to be passed to a device
121 * driver is for them to be collected into requests on a request
122 * queue, and then to allow the device driver to select requests
123 * off that queue when it is ready. This works well for many block
124 * devices. However some block devices (typically virtual devices
125 * such as md or lvm) do not benefit from the processing on the
126 * request queue, and are served best by having the requests passed
127 * directly to them. This can be achieved by providing a function
128 * to blk_queue_make_request().
131 * The driver that does this *must* be able to deal appropriately
132 * with buffers in "highmemory". This can be accomplished by either calling
133 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
134 * blk_queue_bounce() to create a buffer in normal memory.
136 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
141 q->nr_requests = BLKDEV_MAX_RQ;
143 q->make_request_fn = mfn;
144 blk_queue_dma_alignment(q, 511);
145 blk_queue_congestion_threshold(q);
146 q->nr_batching = BLK_BATCH_REQ;
148 q->unplug_thresh = 4; /* hmm */
149 q->unplug_delay = msecs_to_jiffies(3); /* 3 milliseconds */
150 if (q->unplug_delay == 0)
153 q->unplug_timer.function = blk_unplug_timeout;
154 q->unplug_timer.data = (unsigned long)q;
156 blk_set_default_limits(&q->limits);
157 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
160 * If the caller didn't supply a lock, fall back to our embedded
164 q->queue_lock = &q->__queue_lock;
167 * by default assume old behaviour and bounce for any highmem page
169 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
171 EXPORT_SYMBOL(blk_queue_make_request);
174 * blk_queue_bounce_limit - set bounce buffer limit for queue
175 * @q: the request queue for the device
176 * @dma_mask: the maximum address the device can handle
179 * Different hardware can have different requirements as to what pages
180 * it can do I/O directly to. A low level driver can call
181 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
182 * buffers for doing I/O to pages residing above @dma_mask.
184 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
186 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
189 q->bounce_gfp = GFP_NOIO;
190 #if BITS_PER_LONG == 64
192 * Assume anything <= 4GB can be handled by IOMMU. Actually
193 * some IOMMUs can handle everything, but I don't know of a
194 * way to test this here.
196 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
198 q->limits.bounce_pfn = max_low_pfn;
200 if (b_pfn < blk_max_low_pfn)
202 q->limits.bounce_pfn = b_pfn;
205 init_emergency_isa_pool();
206 q->bounce_gfp = GFP_NOIO | GFP_DMA;
207 q->limits.bounce_pfn = b_pfn;
210 EXPORT_SYMBOL(blk_queue_bounce_limit);
213 * blk_queue_max_sectors - set max sectors for a request for this queue
214 * @q: the request queue for the device
215 * @max_sectors: max sectors in the usual 512b unit
218 * Enables a low level driver to set an upper limit on the size of
221 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
223 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
224 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
225 printk(KERN_INFO "%s: set to minimum %d\n",
226 __func__, max_sectors);
229 if (BLK_DEF_MAX_SECTORS > max_sectors)
230 q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;
232 q->limits.max_sectors = BLK_DEF_MAX_SECTORS;
233 q->limits.max_hw_sectors = max_sectors;
236 EXPORT_SYMBOL(blk_queue_max_sectors);
238 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_sectors)
240 if (BLK_DEF_MAX_SECTORS > max_sectors)
241 q->limits.max_hw_sectors = BLK_DEF_MAX_SECTORS;
243 q->limits.max_hw_sectors = max_sectors;
245 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
248 * blk_queue_max_discard_sectors - set max sectors for a single discard
249 * @q: the request queue for the device
250 * @max_discard_sectors: maximum number of sectors to discard
252 void blk_queue_max_discard_sectors(struct request_queue *q,
253 unsigned int max_discard_sectors)
255 q->limits.max_discard_sectors = max_discard_sectors;
257 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
260 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
261 * @q: the request queue for the device
262 * @max_segments: max number of segments
265 * Enables a low level driver to set an upper limit on the number of
266 * physical data segments in a request. This would be the largest sized
267 * scatter list the driver could handle.
269 void blk_queue_max_phys_segments(struct request_queue *q,
270 unsigned short max_segments)
274 printk(KERN_INFO "%s: set to minimum %d\n",
275 __func__, max_segments);
278 q->limits.max_phys_segments = max_segments;
280 EXPORT_SYMBOL(blk_queue_max_phys_segments);
283 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
284 * @q: the request queue for the device
285 * @max_segments: max number of segments
288 * Enables a low level driver to set an upper limit on the number of
289 * hw data segments in a request. This would be the largest number of
290 * address/length pairs the host adapter can actually give at once
293 void blk_queue_max_hw_segments(struct request_queue *q,
294 unsigned short max_segments)
298 printk(KERN_INFO "%s: set to minimum %d\n",
299 __func__, max_segments);
302 q->limits.max_hw_segments = max_segments;
304 EXPORT_SYMBOL(blk_queue_max_hw_segments);
307 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
308 * @q: the request queue for the device
309 * @max_size: max size of segment in bytes
312 * Enables a low level driver to set an upper limit on the size of a
315 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
317 if (max_size < PAGE_CACHE_SIZE) {
318 max_size = PAGE_CACHE_SIZE;
319 printk(KERN_INFO "%s: set to minimum %d\n",
323 q->limits.max_segment_size = max_size;
325 EXPORT_SYMBOL(blk_queue_max_segment_size);
328 * blk_queue_logical_block_size - set logical block size for the queue
329 * @q: the request queue for the device
330 * @size: the logical block size, in bytes
333 * This should be set to the lowest possible block size that the
334 * storage device can address. The default of 512 covers most
337 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
339 q->limits.logical_block_size = size;
341 if (q->limits.physical_block_size < size)
342 q->limits.physical_block_size = size;
344 if (q->limits.io_min < q->limits.physical_block_size)
345 q->limits.io_min = q->limits.physical_block_size;
347 EXPORT_SYMBOL(blk_queue_logical_block_size);
350 * blk_queue_physical_block_size - set physical block size for the queue
351 * @q: the request queue for the device
352 * @size: the physical block size, in bytes
355 * This should be set to the lowest possible sector size that the
356 * hardware can operate on without reverting to read-modify-write
359 void blk_queue_physical_block_size(struct request_queue *q, unsigned short size)
361 q->limits.physical_block_size = size;
363 if (q->limits.physical_block_size < q->limits.logical_block_size)
364 q->limits.physical_block_size = q->limits.logical_block_size;
366 if (q->limits.io_min < q->limits.physical_block_size)
367 q->limits.io_min = q->limits.physical_block_size;
369 EXPORT_SYMBOL(blk_queue_physical_block_size);
372 * blk_queue_alignment_offset - set physical block alignment offset
373 * @q: the request queue for the device
374 * @offset: alignment offset in bytes
377 * Some devices are naturally misaligned to compensate for things like
378 * the legacy DOS partition table 63-sector offset. Low-level drivers
379 * should call this function for devices whose first sector is not
382 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
384 q->limits.alignment_offset =
385 offset & (q->limits.physical_block_size - 1);
386 q->limits.misaligned = 0;
388 EXPORT_SYMBOL(blk_queue_alignment_offset);
391 * blk_limits_io_min - set minimum request size for a device
392 * @limits: the queue limits
393 * @min: smallest I/O size in bytes
396 * Some devices have an internal block size bigger than the reported
397 * hardware sector size. This function can be used to signal the
398 * smallest I/O the device can perform without incurring a performance
401 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
403 limits->io_min = min;
405 if (limits->io_min < limits->logical_block_size)
406 limits->io_min = limits->logical_block_size;
408 if (limits->io_min < limits->physical_block_size)
409 limits->io_min = limits->physical_block_size;
411 EXPORT_SYMBOL(blk_limits_io_min);
414 * blk_queue_io_min - set minimum request size for the queue
415 * @q: the request queue for the device
416 * @min: smallest I/O size in bytes
419 * Storage devices may report a granularity or preferred minimum I/O
420 * size which is the smallest request the device can perform without
421 * incurring a performance penalty. For disk drives this is often the
422 * physical block size. For RAID arrays it is often the stripe chunk
423 * size. A properly aligned multiple of minimum_io_size is the
424 * preferred request size for workloads where a high number of I/O
425 * operations is desired.
427 void blk_queue_io_min(struct request_queue *q, unsigned int min)
429 blk_limits_io_min(&q->limits, min);
431 EXPORT_SYMBOL(blk_queue_io_min);
434 * blk_limits_io_opt - set optimal request size for a device
435 * @limits: the queue limits
436 * @opt: smallest I/O size in bytes
439 * Storage devices may report an optimal I/O size, which is the
440 * device's preferred unit for sustained I/O. This is rarely reported
441 * for disk drives. For RAID arrays it is usually the stripe width or
442 * the internal track size. A properly aligned multiple of
443 * optimal_io_size is the preferred request size for workloads where
444 * sustained throughput is desired.
446 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
448 limits->io_opt = opt;
450 EXPORT_SYMBOL(blk_limits_io_opt);
453 * blk_queue_io_opt - set optimal request size for the queue
454 * @q: the request queue for the device
455 * @opt: optimal request size in bytes
458 * Storage devices may report an optimal I/O size, which is the
459 * device's preferred unit for sustained I/O. This is rarely reported
460 * for disk drives. For RAID arrays it is usually the stripe width or
461 * the internal track size. A properly aligned multiple of
462 * optimal_io_size is the preferred request size for workloads where
463 * sustained throughput is desired.
465 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
467 blk_limits_io_opt(&q->limits, opt);
469 EXPORT_SYMBOL(blk_queue_io_opt);
472 * Returns the minimum that is _not_ zero, unless both are zero.
474 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
477 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
478 * @t: the stacking driver (top)
479 * @b: the underlying device (bottom)
481 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
483 blk_stack_limits(&t->limits, &b->limits, 0);
487 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
489 spin_lock_irqsave(t->queue_lock, flags);
490 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
491 spin_unlock_irqrestore(t->queue_lock, flags);
494 EXPORT_SYMBOL(blk_queue_stack_limits);
496 static unsigned int lcm(unsigned int a, unsigned int b)
499 return (a * b) / gcd(a, b);
507 * blk_stack_limits - adjust queue_limits for stacked devices
508 * @t: the stacking driver limits (top device)
509 * @b: the underlying queue limits (bottom, component device)
510 * @start: first data sector within component device
513 * This function is used by stacking drivers like MD and DM to ensure
514 * that all component devices have compatible block sizes and
515 * alignments. The stacking driver must provide a queue_limits
516 * struct (top) and then iteratively call the stacking function for
517 * all component (bottom) devices. The stacking function will
518 * attempt to combine the values and ensure proper alignment.
520 * Returns 0 if the top and bottom queue_limits are compatible. The
521 * top device's block sizes and alignment offsets may be adjusted to
522 * ensure alignment with the bottom device. If no compatible sizes
523 * and alignments exist, -1 is returned and the resulting top
524 * queue_limits will have the misaligned flag set to indicate that
525 * the alignment_offset is undefined.
527 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
530 unsigned int top, bottom, alignment, ret = 0;
532 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
533 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
534 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
536 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
537 b->seg_boundary_mask);
539 t->max_phys_segments = min_not_zero(t->max_phys_segments,
540 b->max_phys_segments);
542 t->max_hw_segments = min_not_zero(t->max_hw_segments,
545 t->max_segment_size = min_not_zero(t->max_segment_size,
546 b->max_segment_size);
548 t->misaligned |= b->misaligned;
550 alignment = queue_limit_alignment_offset(b, start);
552 /* Bottom device has different alignment. Check that it is
553 * compatible with the current top alignment.
555 if (t->alignment_offset != alignment) {
557 top = max(t->physical_block_size, t->io_min)
558 + t->alignment_offset;
559 bottom = max(b->physical_block_size, b->io_min) + alignment;
561 /* Verify that top and bottom intervals line up */
562 if (max(top, bottom) & (min(top, bottom) - 1)) {
568 t->logical_block_size = max(t->logical_block_size,
569 b->logical_block_size);
571 t->physical_block_size = max(t->physical_block_size,
572 b->physical_block_size);
574 t->io_min = max(t->io_min, b->io_min);
575 t->io_opt = lcm(t->io_opt, b->io_opt);
577 t->no_cluster |= b->no_cluster;
578 t->discard_zeroes_data &= b->discard_zeroes_data;
580 /* Physical block size a multiple of the logical block size? */
581 if (t->physical_block_size & (t->logical_block_size - 1)) {
582 t->physical_block_size = t->logical_block_size;
587 /* Minimum I/O a multiple of the physical block size? */
588 if (t->io_min & (t->physical_block_size - 1)) {
589 t->io_min = t->physical_block_size;
594 /* Optimal I/O a multiple of the physical block size? */
595 if (t->io_opt & (t->physical_block_size - 1)) {
601 /* Find lowest common alignment_offset */
602 t->alignment_offset = lcm(t->alignment_offset, alignment)
603 & (max(t->physical_block_size, t->io_min) - 1);
605 /* Verify that new alignment_offset is on a logical block boundary */
606 if (t->alignment_offset & (t->logical_block_size - 1)) {
611 /* Discard alignment and granularity */
612 if (b->discard_granularity) {
613 alignment = queue_limit_discard_alignment(b, start);
615 if (t->discard_granularity != 0 &&
616 t->discard_alignment != alignment) {
617 top = t->discard_granularity + t->discard_alignment;
618 bottom = b->discard_granularity + alignment;
620 /* Verify that top and bottom intervals line up */
621 if (max(top, bottom) & (min(top, bottom) - 1))
622 t->discard_misaligned = 1;
625 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
626 b->max_discard_sectors);
627 t->discard_granularity = max(t->discard_granularity,
628 b->discard_granularity);
629 t->discard_alignment = lcm(t->discard_alignment, alignment) &
630 (t->discard_granularity - 1);
635 EXPORT_SYMBOL(blk_stack_limits);
638 * bdev_stack_limits - adjust queue limits for stacked drivers
639 * @t: the stacking driver limits (top device)
640 * @bdev: the component block_device (bottom)
641 * @start: first data sector within component device
644 * Merges queue limits for a top device and a block_device. Returns
645 * 0 if alignment didn't change. Returns -1 if adding the bottom
646 * device caused misalignment.
648 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
651 struct request_queue *bq = bdev_get_queue(bdev);
653 start += get_start_sect(bdev);
655 return blk_stack_limits(t, &bq->limits, start);
657 EXPORT_SYMBOL(bdev_stack_limits);
660 * disk_stack_limits - adjust queue limits for stacked drivers
661 * @disk: MD/DM gendisk (top)
662 * @bdev: the underlying block device (bottom)
663 * @offset: offset to beginning of data within component device
666 * Merges the limits for a top level gendisk and a bottom level
669 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
672 struct request_queue *t = disk->queue;
673 struct request_queue *b = bdev_get_queue(bdev);
675 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
676 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
678 disk_name(disk, 0, top);
679 bdevname(bdev, bottom);
681 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
687 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
690 spin_lock_irqsave(t->queue_lock, flags);
691 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
692 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
693 spin_unlock_irqrestore(t->queue_lock, flags);
696 EXPORT_SYMBOL(disk_stack_limits);
699 * blk_queue_dma_pad - set pad mask
700 * @q: the request queue for the device
705 * Appending pad buffer to a request modifies the last entry of a
706 * scatter list such that it includes the pad buffer.
708 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
710 q->dma_pad_mask = mask;
712 EXPORT_SYMBOL(blk_queue_dma_pad);
715 * blk_queue_update_dma_pad - update pad mask
716 * @q: the request queue for the device
719 * Update dma pad mask.
721 * Appending pad buffer to a request modifies the last entry of a
722 * scatter list such that it includes the pad buffer.
724 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
726 if (mask > q->dma_pad_mask)
727 q->dma_pad_mask = mask;
729 EXPORT_SYMBOL(blk_queue_update_dma_pad);
732 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
733 * @q: the request queue for the device
734 * @dma_drain_needed: fn which returns non-zero if drain is necessary
735 * @buf: physically contiguous buffer
736 * @size: size of the buffer in bytes
738 * Some devices have excess DMA problems and can't simply discard (or
739 * zero fill) the unwanted piece of the transfer. They have to have a
740 * real area of memory to transfer it into. The use case for this is
741 * ATAPI devices in DMA mode. If the packet command causes a transfer
742 * bigger than the transfer size some HBAs will lock up if there
743 * aren't DMA elements to contain the excess transfer. What this API
744 * does is adjust the queue so that the buf is always appended
745 * silently to the scatterlist.
747 * Note: This routine adjusts max_hw_segments to make room for
748 * appending the drain buffer. If you call
749 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
750 * calling this routine, you must set the limit to one fewer than your
751 * device can support otherwise there won't be room for the drain
754 int blk_queue_dma_drain(struct request_queue *q,
755 dma_drain_needed_fn *dma_drain_needed,
756 void *buf, unsigned int size)
758 if (queue_max_hw_segments(q) < 2 || queue_max_phys_segments(q) < 2)
760 /* make room for appending the drain */
761 blk_queue_max_hw_segments(q, queue_max_hw_segments(q) - 1);
762 blk_queue_max_phys_segments(q, queue_max_phys_segments(q) - 1);
763 q->dma_drain_needed = dma_drain_needed;
764 q->dma_drain_buffer = buf;
765 q->dma_drain_size = size;
769 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
772 * blk_queue_segment_boundary - set boundary rules for segment merging
773 * @q: the request queue for the device
774 * @mask: the memory boundary mask
776 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
778 if (mask < PAGE_CACHE_SIZE - 1) {
779 mask = PAGE_CACHE_SIZE - 1;
780 printk(KERN_INFO "%s: set to minimum %lx\n",
784 q->limits.seg_boundary_mask = mask;
786 EXPORT_SYMBOL(blk_queue_segment_boundary);
789 * blk_queue_dma_alignment - set dma length and memory alignment
790 * @q: the request queue for the device
791 * @mask: alignment mask
794 * set required memory and length alignment for direct dma transactions.
795 * this is used when building direct io requests for the queue.
798 void blk_queue_dma_alignment(struct request_queue *q, int mask)
800 q->dma_alignment = mask;
802 EXPORT_SYMBOL(blk_queue_dma_alignment);
805 * blk_queue_update_dma_alignment - update dma length and memory alignment
806 * @q: the request queue for the device
807 * @mask: alignment mask
810 * update required memory and length alignment for direct dma transactions.
811 * If the requested alignment is larger than the current alignment, then
812 * the current queue alignment is updated to the new value, otherwise it
813 * is left alone. The design of this is to allow multiple objects
814 * (driver, device, transport etc) to set their respective
815 * alignments without having them interfere.
818 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
820 BUG_ON(mask > PAGE_SIZE);
822 if (mask > q->dma_alignment)
823 q->dma_alignment = mask;
825 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
827 static int __init blk_settings_init(void)
829 blk_max_low_pfn = max_low_pfn - 1;
830 blk_max_pfn = max_pfn - 1;
833 subsys_initcall(blk_settings_init);