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 = BLK_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, BLK_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_hw_sectors: max hardware sectors in the usual 512b unit
218 * Enables a low level driver to set a hard upper limit,
219 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
220 * the device driver based upon the combined capabilities of I/O
221 * controller and storage device.
223 * max_sectors is a soft limit imposed by the block layer for
224 * filesystem type requests. This value can be overridden on a
225 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
226 * The soft limit can not exceed max_hw_sectors.
228 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_hw_sectors)
230 if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
231 max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
232 printk(KERN_INFO "%s: set to minimum %d\n",
233 __func__, max_hw_sectors);
236 q->limits.max_hw_sectors = max_hw_sectors;
237 q->limits.max_sectors = min_t(unsigned int, max_hw_sectors,
238 BLK_DEF_MAX_SECTORS);
240 EXPORT_SYMBOL(blk_queue_max_sectors);
243 * blk_queue_max_discard_sectors - set max sectors for a single discard
244 * @q: the request queue for the device
245 * @max_discard_sectors: maximum number of sectors to discard
247 void blk_queue_max_discard_sectors(struct request_queue *q,
248 unsigned int max_discard_sectors)
250 q->limits.max_discard_sectors = max_discard_sectors;
252 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
255 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
256 * @q: the request queue for the device
257 * @max_segments: max number of segments
260 * Enables a low level driver to set an upper limit on the number of
261 * physical data segments in a request. This would be the largest sized
262 * scatter list the driver could handle.
264 void blk_queue_max_phys_segments(struct request_queue *q,
265 unsigned short max_segments)
269 printk(KERN_INFO "%s: set to minimum %d\n",
270 __func__, max_segments);
273 q->limits.max_phys_segments = max_segments;
275 EXPORT_SYMBOL(blk_queue_max_phys_segments);
278 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
279 * @q: the request queue for the device
280 * @max_segments: max number of segments
283 * Enables a low level driver to set an upper limit on the number of
284 * hw data segments in a request. This would be the largest number of
285 * address/length pairs the host adapter can actually give at once
288 void blk_queue_max_hw_segments(struct request_queue *q,
289 unsigned short max_segments)
293 printk(KERN_INFO "%s: set to minimum %d\n",
294 __func__, max_segments);
297 q->limits.max_hw_segments = max_segments;
299 EXPORT_SYMBOL(blk_queue_max_hw_segments);
302 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
303 * @q: the request queue for the device
304 * @max_size: max size of segment in bytes
307 * Enables a low level driver to set an upper limit on the size of a
310 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
312 if (max_size < PAGE_CACHE_SIZE) {
313 max_size = PAGE_CACHE_SIZE;
314 printk(KERN_INFO "%s: set to minimum %d\n",
318 q->limits.max_segment_size = max_size;
320 EXPORT_SYMBOL(blk_queue_max_segment_size);
323 * blk_queue_logical_block_size - set logical block size for the queue
324 * @q: the request queue for the device
325 * @size: the logical block size, in bytes
328 * This should be set to the lowest possible block size that the
329 * storage device can address. The default of 512 covers most
332 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
334 q->limits.logical_block_size = size;
336 if (q->limits.physical_block_size < size)
337 q->limits.physical_block_size = size;
339 if (q->limits.io_min < q->limits.physical_block_size)
340 q->limits.io_min = q->limits.physical_block_size;
342 EXPORT_SYMBOL(blk_queue_logical_block_size);
345 * blk_queue_physical_block_size - set physical block size for the queue
346 * @q: the request queue for the device
347 * @size: the physical block size, in bytes
350 * This should be set to the lowest possible sector size that the
351 * hardware can operate on without reverting to read-modify-write
354 void blk_queue_physical_block_size(struct request_queue *q, unsigned short size)
356 q->limits.physical_block_size = size;
358 if (q->limits.physical_block_size < q->limits.logical_block_size)
359 q->limits.physical_block_size = q->limits.logical_block_size;
361 if (q->limits.io_min < q->limits.physical_block_size)
362 q->limits.io_min = q->limits.physical_block_size;
364 EXPORT_SYMBOL(blk_queue_physical_block_size);
367 * blk_queue_alignment_offset - set physical block alignment offset
368 * @q: the request queue for the device
369 * @offset: alignment offset in bytes
372 * Some devices are naturally misaligned to compensate for things like
373 * the legacy DOS partition table 63-sector offset. Low-level drivers
374 * should call this function for devices whose first sector is not
377 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
379 q->limits.alignment_offset =
380 offset & (q->limits.physical_block_size - 1);
381 q->limits.misaligned = 0;
383 EXPORT_SYMBOL(blk_queue_alignment_offset);
386 * blk_limits_io_min - set minimum request size for a device
387 * @limits: the queue limits
388 * @min: smallest I/O size in bytes
391 * Some devices have an internal block size bigger than the reported
392 * hardware sector size. This function can be used to signal the
393 * smallest I/O the device can perform without incurring a performance
396 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
398 limits->io_min = min;
400 if (limits->io_min < limits->logical_block_size)
401 limits->io_min = limits->logical_block_size;
403 if (limits->io_min < limits->physical_block_size)
404 limits->io_min = limits->physical_block_size;
406 EXPORT_SYMBOL(blk_limits_io_min);
409 * blk_queue_io_min - set minimum request size for the queue
410 * @q: the request queue for the device
411 * @min: smallest I/O size in bytes
414 * Storage devices may report a granularity or preferred minimum I/O
415 * size which is the smallest request the device can perform without
416 * incurring a performance penalty. For disk drives this is often the
417 * physical block size. For RAID arrays it is often the stripe chunk
418 * size. A properly aligned multiple of minimum_io_size is the
419 * preferred request size for workloads where a high number of I/O
420 * operations is desired.
422 void blk_queue_io_min(struct request_queue *q, unsigned int min)
424 blk_limits_io_min(&q->limits, min);
426 EXPORT_SYMBOL(blk_queue_io_min);
429 * blk_limits_io_opt - set optimal request size for a device
430 * @limits: the queue limits
431 * @opt: smallest I/O size in bytes
434 * Storage devices may report an optimal I/O size, which is the
435 * device's preferred unit for sustained I/O. This is rarely reported
436 * for disk drives. For RAID arrays it is usually the stripe width or
437 * the internal track size. A properly aligned multiple of
438 * optimal_io_size is the preferred request size for workloads where
439 * sustained throughput is desired.
441 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
443 limits->io_opt = opt;
445 EXPORT_SYMBOL(blk_limits_io_opt);
448 * blk_queue_io_opt - set optimal request size for the queue
449 * @q: the request queue for the device
450 * @opt: optimal request size in bytes
453 * Storage devices may report an optimal I/O size, which is the
454 * device's preferred unit for sustained I/O. This is rarely reported
455 * for disk drives. For RAID arrays it is usually the stripe width or
456 * the internal track size. A properly aligned multiple of
457 * optimal_io_size is the preferred request size for workloads where
458 * sustained throughput is desired.
460 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
462 blk_limits_io_opt(&q->limits, opt);
464 EXPORT_SYMBOL(blk_queue_io_opt);
467 * Returns the minimum that is _not_ zero, unless both are zero.
469 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
472 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
473 * @t: the stacking driver (top)
474 * @b: the underlying device (bottom)
476 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
478 blk_stack_limits(&t->limits, &b->limits, 0);
482 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
484 spin_lock_irqsave(t->queue_lock, flags);
485 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
486 spin_unlock_irqrestore(t->queue_lock, flags);
489 EXPORT_SYMBOL(blk_queue_stack_limits);
491 static unsigned int lcm(unsigned int a, unsigned int b)
494 return (a * b) / gcd(a, b);
502 * blk_stack_limits - adjust queue_limits for stacked devices
503 * @t: the stacking driver limits (top device)
504 * @b: the underlying queue limits (bottom, component device)
505 * @start: first data sector within component device
508 * This function is used by stacking drivers like MD and DM to ensure
509 * that all component devices have compatible block sizes and
510 * alignments. The stacking driver must provide a queue_limits
511 * struct (top) and then iteratively call the stacking function for
512 * all component (bottom) devices. The stacking function will
513 * attempt to combine the values and ensure proper alignment.
515 * Returns 0 if the top and bottom queue_limits are compatible. The
516 * top device's block sizes and alignment offsets may be adjusted to
517 * ensure alignment with the bottom device. If no compatible sizes
518 * and alignments exist, -1 is returned and the resulting top
519 * queue_limits will have the misaligned flag set to indicate that
520 * the alignment_offset is undefined.
522 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
525 unsigned int top, bottom, alignment, ret = 0;
527 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
528 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
529 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
531 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
532 b->seg_boundary_mask);
534 t->max_phys_segments = min_not_zero(t->max_phys_segments,
535 b->max_phys_segments);
537 t->max_hw_segments = min_not_zero(t->max_hw_segments,
540 t->max_segment_size = min_not_zero(t->max_segment_size,
541 b->max_segment_size);
543 t->misaligned |= b->misaligned;
545 alignment = queue_limit_alignment_offset(b, start);
547 /* Bottom device has different alignment. Check that it is
548 * compatible with the current top alignment.
550 if (t->alignment_offset != alignment) {
552 top = max(t->physical_block_size, t->io_min)
553 + t->alignment_offset;
554 bottom = max(b->physical_block_size, b->io_min) + alignment;
556 /* Verify that top and bottom intervals line up */
557 if (max(top, bottom) & (min(top, bottom) - 1)) {
563 t->logical_block_size = max(t->logical_block_size,
564 b->logical_block_size);
566 t->physical_block_size = max(t->physical_block_size,
567 b->physical_block_size);
569 t->io_min = max(t->io_min, b->io_min);
570 t->io_opt = lcm(t->io_opt, b->io_opt);
572 t->no_cluster |= b->no_cluster;
573 t->discard_zeroes_data &= b->discard_zeroes_data;
575 /* Physical block size a multiple of the logical block size? */
576 if (t->physical_block_size & (t->logical_block_size - 1)) {
577 t->physical_block_size = t->logical_block_size;
582 /* Minimum I/O a multiple of the physical block size? */
583 if (t->io_min & (t->physical_block_size - 1)) {
584 t->io_min = t->physical_block_size;
589 /* Optimal I/O a multiple of the physical block size? */
590 if (t->io_opt & (t->physical_block_size - 1)) {
596 /* Find lowest common alignment_offset */
597 t->alignment_offset = lcm(t->alignment_offset, alignment)
598 & (max(t->physical_block_size, t->io_min) - 1);
600 /* Verify that new alignment_offset is on a logical block boundary */
601 if (t->alignment_offset & (t->logical_block_size - 1)) {
606 /* Discard alignment and granularity */
607 if (b->discard_granularity) {
608 alignment = queue_limit_discard_alignment(b, start);
610 if (t->discard_granularity != 0 &&
611 t->discard_alignment != alignment) {
612 top = t->discard_granularity + t->discard_alignment;
613 bottom = b->discard_granularity + alignment;
615 /* Verify that top and bottom intervals line up */
616 if (max(top, bottom) & (min(top, bottom) - 1))
617 t->discard_misaligned = 1;
620 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
621 b->max_discard_sectors);
622 t->discard_granularity = max(t->discard_granularity,
623 b->discard_granularity);
624 t->discard_alignment = lcm(t->discard_alignment, alignment) &
625 (t->discard_granularity - 1);
630 EXPORT_SYMBOL(blk_stack_limits);
633 * bdev_stack_limits - adjust queue limits for stacked drivers
634 * @t: the stacking driver limits (top device)
635 * @bdev: the component block_device (bottom)
636 * @start: first data sector within component device
639 * Merges queue limits for a top device and a block_device. Returns
640 * 0 if alignment didn't change. Returns -1 if adding the bottom
641 * device caused misalignment.
643 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
646 struct request_queue *bq = bdev_get_queue(bdev);
648 start += get_start_sect(bdev);
650 return blk_stack_limits(t, &bq->limits, start);
652 EXPORT_SYMBOL(bdev_stack_limits);
655 * disk_stack_limits - adjust queue limits for stacked drivers
656 * @disk: MD/DM gendisk (top)
657 * @bdev: the underlying block device (bottom)
658 * @offset: offset to beginning of data within component device
661 * Merges the limits for a top level gendisk and a bottom level
664 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
667 struct request_queue *t = disk->queue;
668 struct request_queue *b = bdev_get_queue(bdev);
670 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
671 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
673 disk_name(disk, 0, top);
674 bdevname(bdev, bottom);
676 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
682 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
685 spin_lock_irqsave(t->queue_lock, flags);
686 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
687 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
688 spin_unlock_irqrestore(t->queue_lock, flags);
691 EXPORT_SYMBOL(disk_stack_limits);
694 * blk_queue_dma_pad - set pad mask
695 * @q: the request queue for the device
700 * Appending pad buffer to a request modifies the last entry of a
701 * scatter list such that it includes the pad buffer.
703 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
705 q->dma_pad_mask = mask;
707 EXPORT_SYMBOL(blk_queue_dma_pad);
710 * blk_queue_update_dma_pad - update pad mask
711 * @q: the request queue for the device
714 * Update dma pad mask.
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_update_dma_pad(struct request_queue *q, unsigned int mask)
721 if (mask > q->dma_pad_mask)
722 q->dma_pad_mask = mask;
724 EXPORT_SYMBOL(blk_queue_update_dma_pad);
727 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
728 * @q: the request queue for the device
729 * @dma_drain_needed: fn which returns non-zero if drain is necessary
730 * @buf: physically contiguous buffer
731 * @size: size of the buffer in bytes
733 * Some devices have excess DMA problems and can't simply discard (or
734 * zero fill) the unwanted piece of the transfer. They have to have a
735 * real area of memory to transfer it into. The use case for this is
736 * ATAPI devices in DMA mode. If the packet command causes a transfer
737 * bigger than the transfer size some HBAs will lock up if there
738 * aren't DMA elements to contain the excess transfer. What this API
739 * does is adjust the queue so that the buf is always appended
740 * silently to the scatterlist.
742 * Note: This routine adjusts max_hw_segments to make room for
743 * appending the drain buffer. If you call
744 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
745 * calling this routine, you must set the limit to one fewer than your
746 * device can support otherwise there won't be room for the drain
749 int blk_queue_dma_drain(struct request_queue *q,
750 dma_drain_needed_fn *dma_drain_needed,
751 void *buf, unsigned int size)
753 if (queue_max_hw_segments(q) < 2 || queue_max_phys_segments(q) < 2)
755 /* make room for appending the drain */
756 blk_queue_max_hw_segments(q, queue_max_hw_segments(q) - 1);
757 blk_queue_max_phys_segments(q, queue_max_phys_segments(q) - 1);
758 q->dma_drain_needed = dma_drain_needed;
759 q->dma_drain_buffer = buf;
760 q->dma_drain_size = size;
764 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
767 * blk_queue_segment_boundary - set boundary rules for segment merging
768 * @q: the request queue for the device
769 * @mask: the memory boundary mask
771 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
773 if (mask < PAGE_CACHE_SIZE - 1) {
774 mask = PAGE_CACHE_SIZE - 1;
775 printk(KERN_INFO "%s: set to minimum %lx\n",
779 q->limits.seg_boundary_mask = mask;
781 EXPORT_SYMBOL(blk_queue_segment_boundary);
784 * blk_queue_dma_alignment - set dma length and memory alignment
785 * @q: the request queue for the device
786 * @mask: alignment mask
789 * set required memory and length alignment for direct dma transactions.
790 * this is used when building direct io requests for the queue.
793 void blk_queue_dma_alignment(struct request_queue *q, int mask)
795 q->dma_alignment = mask;
797 EXPORT_SYMBOL(blk_queue_dma_alignment);
800 * blk_queue_update_dma_alignment - update dma length and memory alignment
801 * @q: the request queue for the device
802 * @mask: alignment mask
805 * update required memory and length alignment for direct dma transactions.
806 * If the requested alignment is larger than the current alignment, then
807 * the current queue alignment is updated to the new value, otherwise it
808 * is left alone. The design of this is to allow multiple objects
809 * (driver, device, transport etc) to set their respective
810 * alignments without having them interfere.
813 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
815 BUG_ON(mask > PAGE_SIZE);
817 if (mask > q->dma_alignment)
818 q->dma_alignment = mask;
820 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
822 static int __init blk_settings_init(void)
824 blk_max_low_pfn = max_low_pfn - 1;
825 blk_max_pfn = max_pfn - 1;
828 subsys_initcall(blk_settings_init);