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>
14 unsigned long blk_max_low_pfn
;
15 EXPORT_SYMBOL(blk_max_low_pfn
);
17 unsigned long blk_max_pfn
;
20 * blk_queue_prep_rq - set a prepare_request function for queue
22 * @pfn: prepare_request function
24 * It's possible for a queue to register a prepare_request callback which
25 * is invoked before the request is handed to the request_fn. The goal of
26 * the function is to prepare a request for I/O, it can be used to build a
27 * cdb from the request data for instance.
30 void blk_queue_prep_rq(struct request_queue
*q
, prep_rq_fn
*pfn
)
34 EXPORT_SYMBOL(blk_queue_prep_rq
);
37 * blk_queue_merge_bvec - set a merge_bvec function for queue
39 * @mbfn: merge_bvec_fn
41 * Usually queues have static limitations on the max sectors or segments that
42 * we can put in a request. Stacking drivers may have some settings that
43 * are dynamic, and thus we have to query the queue whether it is ok to
44 * add a new bio_vec to a bio at a given offset or not. If the block device
45 * has such limitations, it needs to register a merge_bvec_fn to control
46 * the size of bio's sent to it. Note that a block device *must* allow a
47 * single page to be added to an empty bio. The block device driver may want
48 * to use the bio_split() function to deal with these bio's. By default
49 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
52 void blk_queue_merge_bvec(struct request_queue
*q
, merge_bvec_fn
*mbfn
)
54 q
->merge_bvec_fn
= mbfn
;
56 EXPORT_SYMBOL(blk_queue_merge_bvec
);
58 void blk_queue_softirq_done(struct request_queue
*q
, softirq_done_fn
*fn
)
60 q
->softirq_done_fn
= fn
;
62 EXPORT_SYMBOL(blk_queue_softirq_done
);
64 void blk_queue_rq_timeout(struct request_queue
*q
, unsigned int timeout
)
66 q
->rq_timeout
= timeout
;
68 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout
);
70 void blk_queue_rq_timed_out(struct request_queue
*q
, rq_timed_out_fn
*fn
)
72 q
->rq_timed_out_fn
= fn
;
74 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out
);
76 void blk_queue_lld_busy(struct request_queue
*q
, lld_busy_fn
*fn
)
80 EXPORT_SYMBOL_GPL(blk_queue_lld_busy
);
83 * blk_set_default_limits - reset limits to default values
84 * @lim: the queue_limits structure to reset
87 * Returns a queue_limit struct to its default state. Can be used by
88 * stacking drivers like DM that stage table swaps and reuse an
89 * existing device queue.
91 void blk_set_default_limits(struct queue_limits
*lim
)
93 lim
->max_phys_segments
= MAX_PHYS_SEGMENTS
;
94 lim
->max_hw_segments
= MAX_HW_SEGMENTS
;
95 lim
->seg_boundary_mask
= BLK_SEG_BOUNDARY_MASK
;
96 lim
->max_segment_size
= MAX_SEGMENT_SIZE
;
97 lim
->max_sectors
= BLK_DEF_MAX_SECTORS
;
98 lim
->max_hw_sectors
= INT_MAX
;
99 lim
->max_discard_sectors
= 0;
100 lim
->discard_granularity
= 0;
101 lim
->discard_alignment
= 0;
102 lim
->discard_misaligned
= 0;
103 lim
->logical_block_size
= lim
->physical_block_size
= lim
->io_min
= 512;
104 lim
->bounce_pfn
= (unsigned long)(BLK_BOUNCE_ANY
>> PAGE_SHIFT
);
105 lim
->alignment_offset
= 0;
110 EXPORT_SYMBOL(blk_set_default_limits
);
113 * blk_queue_make_request - define an alternate make_request function for a device
114 * @q: the request queue for the device to be affected
115 * @mfn: the alternate make_request function
118 * The normal way for &struct bios to be passed to a device
119 * driver is for them to be collected into requests on a request
120 * queue, and then to allow the device driver to select requests
121 * off that queue when it is ready. This works well for many block
122 * devices. However some block devices (typically virtual devices
123 * such as md or lvm) do not benefit from the processing on the
124 * request queue, and are served best by having the requests passed
125 * directly to them. This can be achieved by providing a function
126 * to blk_queue_make_request().
129 * The driver that does this *must* be able to deal appropriately
130 * with buffers in "highmemory". This can be accomplished by either calling
131 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
132 * blk_queue_bounce() to create a buffer in normal memory.
134 void blk_queue_make_request(struct request_queue
*q
, make_request_fn
*mfn
)
139 q
->nr_requests
= BLKDEV_MAX_RQ
;
141 q
->make_request_fn
= mfn
;
142 blk_queue_dma_alignment(q
, 511);
143 blk_queue_congestion_threshold(q
);
144 q
->nr_batching
= BLK_BATCH_REQ
;
146 q
->unplug_thresh
= 4; /* hmm */
147 q
->unplug_delay
= (3 * HZ
) / 1000; /* 3 milliseconds */
148 if (q
->unplug_delay
== 0)
151 q
->unplug_timer
.function
= blk_unplug_timeout
;
152 q
->unplug_timer
.data
= (unsigned long)q
;
154 blk_set_default_limits(&q
->limits
);
155 blk_queue_max_sectors(q
, SAFE_MAX_SECTORS
);
158 * If the caller didn't supply a lock, fall back to our embedded
162 q
->queue_lock
= &q
->__queue_lock
;
165 * by default assume old behaviour and bounce for any highmem page
167 blk_queue_bounce_limit(q
, BLK_BOUNCE_HIGH
);
169 EXPORT_SYMBOL(blk_queue_make_request
);
172 * blk_queue_bounce_limit - set bounce buffer limit for queue
173 * @q: the request queue for the device
174 * @dma_mask: the maximum address the device can handle
177 * Different hardware can have different requirements as to what pages
178 * it can do I/O directly to. A low level driver can call
179 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
180 * buffers for doing I/O to pages residing above @dma_mask.
182 void blk_queue_bounce_limit(struct request_queue
*q
, u64 dma_mask
)
184 unsigned long b_pfn
= dma_mask
>> PAGE_SHIFT
;
187 q
->bounce_gfp
= GFP_NOIO
;
188 #if BITS_PER_LONG == 64
190 * Assume anything <= 4GB can be handled by IOMMU. Actually
191 * some IOMMUs can handle everything, but I don't know of a
192 * way to test this here.
194 if (b_pfn
< (min_t(u64
, 0xffffffffUL
, BLK_BOUNCE_HIGH
) >> PAGE_SHIFT
))
196 q
->limits
.bounce_pfn
= max_low_pfn
;
198 if (b_pfn
< blk_max_low_pfn
)
200 q
->limits
.bounce_pfn
= b_pfn
;
203 init_emergency_isa_pool();
204 q
->bounce_gfp
= GFP_NOIO
| GFP_DMA
;
205 q
->limits
.bounce_pfn
= b_pfn
;
208 EXPORT_SYMBOL(blk_queue_bounce_limit
);
211 * blk_queue_max_sectors - set max sectors for a request for this queue
212 * @q: the request queue for the device
213 * @max_sectors: max sectors in the usual 512b unit
216 * Enables a low level driver to set an upper limit on the size of
219 void blk_queue_max_sectors(struct request_queue
*q
, unsigned int max_sectors
)
221 if ((max_sectors
<< 9) < PAGE_CACHE_SIZE
) {
222 max_sectors
= 1 << (PAGE_CACHE_SHIFT
- 9);
223 printk(KERN_INFO
"%s: set to minimum %d\n",
224 __func__
, max_sectors
);
227 if (BLK_DEF_MAX_SECTORS
> max_sectors
)
228 q
->limits
.max_hw_sectors
= q
->limits
.max_sectors
= max_sectors
;
230 q
->limits
.max_sectors
= BLK_DEF_MAX_SECTORS
;
231 q
->limits
.max_hw_sectors
= max_sectors
;
234 EXPORT_SYMBOL(blk_queue_max_sectors
);
236 void blk_queue_max_hw_sectors(struct request_queue
*q
, unsigned int max_sectors
)
238 if (BLK_DEF_MAX_SECTORS
> max_sectors
)
239 q
->limits
.max_hw_sectors
= BLK_DEF_MAX_SECTORS
;
241 q
->limits
.max_hw_sectors
= max_sectors
;
243 EXPORT_SYMBOL(blk_queue_max_hw_sectors
);
246 * blk_queue_max_discard_sectors - set max sectors for a single discard
247 * @q: the request queue for the device
248 * @max_discard_sectors: maximum number of sectors to discard
250 void blk_queue_max_discard_sectors(struct request_queue
*q
,
251 unsigned int max_discard_sectors
)
253 q
->limits
.max_discard_sectors
= max_discard_sectors
;
255 EXPORT_SYMBOL(blk_queue_max_discard_sectors
);
258 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
259 * @q: the request queue for the device
260 * @max_segments: max number of segments
263 * Enables a low level driver to set an upper limit on the number of
264 * physical data segments in a request. This would be the largest sized
265 * scatter list the driver could handle.
267 void blk_queue_max_phys_segments(struct request_queue
*q
,
268 unsigned short max_segments
)
272 printk(KERN_INFO
"%s: set to minimum %d\n",
273 __func__
, max_segments
);
276 q
->limits
.max_phys_segments
= max_segments
;
278 EXPORT_SYMBOL(blk_queue_max_phys_segments
);
281 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
282 * @q: the request queue for the device
283 * @max_segments: max number of segments
286 * Enables a low level driver to set an upper limit on the number of
287 * hw data segments in a request. This would be the largest number of
288 * address/length pairs the host adapter can actually give at once
291 void blk_queue_max_hw_segments(struct request_queue
*q
,
292 unsigned short max_segments
)
296 printk(KERN_INFO
"%s: set to minimum %d\n",
297 __func__
, max_segments
);
300 q
->limits
.max_hw_segments
= max_segments
;
302 EXPORT_SYMBOL(blk_queue_max_hw_segments
);
305 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
306 * @q: the request queue for the device
307 * @max_size: max size of segment in bytes
310 * Enables a low level driver to set an upper limit on the size of a
313 void blk_queue_max_segment_size(struct request_queue
*q
, unsigned int max_size
)
315 if (max_size
< PAGE_CACHE_SIZE
) {
316 max_size
= PAGE_CACHE_SIZE
;
317 printk(KERN_INFO
"%s: set to minimum %d\n",
321 q
->limits
.max_segment_size
= max_size
;
323 EXPORT_SYMBOL(blk_queue_max_segment_size
);
326 * blk_queue_logical_block_size - set logical block size for the queue
327 * @q: the request queue for the device
328 * @size: the logical block size, in bytes
331 * This should be set to the lowest possible block size that the
332 * storage device can address. The default of 512 covers most
335 void blk_queue_logical_block_size(struct request_queue
*q
, unsigned short size
)
337 q
->limits
.logical_block_size
= size
;
339 if (q
->limits
.physical_block_size
< size
)
340 q
->limits
.physical_block_size
= size
;
342 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
343 q
->limits
.io_min
= q
->limits
.physical_block_size
;
345 EXPORT_SYMBOL(blk_queue_logical_block_size
);
348 * blk_queue_physical_block_size - set physical block size for the queue
349 * @q: the request queue for the device
350 * @size: the physical block size, in bytes
353 * This should be set to the lowest possible sector size that the
354 * hardware can operate on without reverting to read-modify-write
357 void blk_queue_physical_block_size(struct request_queue
*q
, unsigned short size
)
359 q
->limits
.physical_block_size
= size
;
361 if (q
->limits
.physical_block_size
< q
->limits
.logical_block_size
)
362 q
->limits
.physical_block_size
= q
->limits
.logical_block_size
;
364 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
365 q
->limits
.io_min
= q
->limits
.physical_block_size
;
367 EXPORT_SYMBOL(blk_queue_physical_block_size
);
370 * blk_queue_alignment_offset - set physical block alignment offset
371 * @q: the request queue for the device
372 * @offset: alignment offset in bytes
375 * Some devices are naturally misaligned to compensate for things like
376 * the legacy DOS partition table 63-sector offset. Low-level drivers
377 * should call this function for devices whose first sector is not
380 void blk_queue_alignment_offset(struct request_queue
*q
, unsigned int offset
)
382 q
->limits
.alignment_offset
=
383 offset
& (q
->limits
.physical_block_size
- 1);
384 q
->limits
.misaligned
= 0;
386 EXPORT_SYMBOL(blk_queue_alignment_offset
);
389 * blk_limits_io_min - set minimum request size for a device
390 * @limits: the queue limits
391 * @min: smallest I/O size in bytes
394 * Some devices have an internal block size bigger than the reported
395 * hardware sector size. This function can be used to signal the
396 * smallest I/O the device can perform without incurring a performance
399 void blk_limits_io_min(struct queue_limits
*limits
, unsigned int min
)
401 limits
->io_min
= min
;
403 if (limits
->io_min
< limits
->logical_block_size
)
404 limits
->io_min
= limits
->logical_block_size
;
406 if (limits
->io_min
< limits
->physical_block_size
)
407 limits
->io_min
= limits
->physical_block_size
;
409 EXPORT_SYMBOL(blk_limits_io_min
);
412 * blk_queue_io_min - set minimum request size for the queue
413 * @q: the request queue for the device
414 * @min: smallest I/O size in bytes
417 * Storage devices may report a granularity or preferred minimum I/O
418 * size which is the smallest request the device can perform without
419 * incurring a performance penalty. For disk drives this is often the
420 * physical block size. For RAID arrays it is often the stripe chunk
421 * size. A properly aligned multiple of minimum_io_size is the
422 * preferred request size for workloads where a high number of I/O
423 * operations is desired.
425 void blk_queue_io_min(struct request_queue
*q
, unsigned int min
)
427 blk_limits_io_min(&q
->limits
, min
);
429 EXPORT_SYMBOL(blk_queue_io_min
);
432 * blk_limits_io_opt - set optimal request size for a device
433 * @limits: the queue limits
434 * @opt: smallest I/O size in bytes
437 * Storage devices may report an optimal I/O size, which is the
438 * device's preferred unit for sustained I/O. This is rarely reported
439 * for disk drives. For RAID arrays it is usually the stripe width or
440 * the internal track size. A properly aligned multiple of
441 * optimal_io_size is the preferred request size for workloads where
442 * sustained throughput is desired.
444 void blk_limits_io_opt(struct queue_limits
*limits
, unsigned int opt
)
446 limits
->io_opt
= opt
;
448 EXPORT_SYMBOL(blk_limits_io_opt
);
451 * blk_queue_io_opt - set optimal request size for the queue
452 * @q: the request queue for the device
453 * @opt: optimal request size in bytes
456 * Storage devices may report an optimal I/O size, which is the
457 * device's preferred unit for sustained I/O. This is rarely reported
458 * for disk drives. For RAID arrays it is usually the stripe width or
459 * the internal track size. A properly aligned multiple of
460 * optimal_io_size is the preferred request size for workloads where
461 * sustained throughput is desired.
463 void blk_queue_io_opt(struct request_queue
*q
, unsigned int opt
)
465 blk_limits_io_opt(&q
->limits
, opt
);
467 EXPORT_SYMBOL(blk_queue_io_opt
);
470 * Returns the minimum that is _not_ zero, unless both are zero.
472 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
475 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
476 * @t: the stacking driver (top)
477 * @b: the underlying device (bottom)
479 void blk_queue_stack_limits(struct request_queue
*t
, struct request_queue
*b
)
481 blk_stack_limits(&t
->limits
, &b
->limits
, 0);
485 else if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
)) {
487 spin_lock_irqsave(t
->queue_lock
, flags
);
488 queue_flag_clear(QUEUE_FLAG_CLUSTER
, t
);
489 spin_unlock_irqrestore(t
->queue_lock
, flags
);
492 EXPORT_SYMBOL(blk_queue_stack_limits
);
494 static unsigned int lcm(unsigned int a
, unsigned int b
)
497 return (a
* b
) / gcd(a
, b
);
505 * blk_stack_limits - adjust queue_limits for stacked devices
506 * @t: the stacking driver limits (top)
507 * @b: the underlying queue limits (bottom)
508 * @offset: offset to beginning of data within component device
511 * Merges two queue_limit structs. Returns 0 if alignment didn't
512 * change. Returns -1 if adding the bottom device caused
515 int blk_stack_limits(struct queue_limits
*t
, struct queue_limits
*b
,
522 t
->max_sectors
= min_not_zero(t
->max_sectors
, b
->max_sectors
);
523 t
->max_hw_sectors
= min_not_zero(t
->max_hw_sectors
, b
->max_hw_sectors
);
524 t
->bounce_pfn
= min_not_zero(t
->bounce_pfn
, b
->bounce_pfn
);
526 t
->seg_boundary_mask
= min_not_zero(t
->seg_boundary_mask
,
527 b
->seg_boundary_mask
);
529 t
->max_phys_segments
= min_not_zero(t
->max_phys_segments
,
530 b
->max_phys_segments
);
532 t
->max_hw_segments
= min_not_zero(t
->max_hw_segments
,
535 t
->max_segment_size
= min_not_zero(t
->max_segment_size
,
536 b
->max_segment_size
);
538 t
->logical_block_size
= max(t
->logical_block_size
,
539 b
->logical_block_size
);
541 t
->physical_block_size
= max(t
->physical_block_size
,
542 b
->physical_block_size
);
544 t
->io_min
= max(t
->io_min
, b
->io_min
);
545 t
->no_cluster
|= b
->no_cluster
;
547 /* Bottom device offset aligned? */
549 (offset
& (b
->physical_block_size
- 1)) != b
->alignment_offset
) {
555 (offset
& (b
->discard_granularity
- 1)) != b
->discard_alignment
) {
556 t
->discard_misaligned
= 1;
560 /* If top has no alignment offset, inherit from bottom */
561 if (!t
->alignment_offset
)
562 t
->alignment_offset
=
563 b
->alignment_offset
& (b
->physical_block_size
- 1);
565 if (!t
->discard_alignment
)
566 t
->discard_alignment
=
567 b
->discard_alignment
& (b
->discard_granularity
- 1);
569 /* Top device aligned on logical block boundary? */
570 if (t
->alignment_offset
& (t
->logical_block_size
- 1)) {
575 /* Find lcm() of optimal I/O size and granularity */
576 t
->io_opt
= lcm(t
->io_opt
, b
->io_opt
);
577 t
->discard_granularity
= lcm(t
->discard_granularity
,
578 b
->discard_granularity
);
580 /* Verify that optimal I/O size is a multiple of io_min */
581 if (t
->io_min
&& t
->io_opt
% t
->io_min
)
586 EXPORT_SYMBOL(blk_stack_limits
);
589 * disk_stack_limits - adjust queue limits for stacked drivers
590 * @disk: MD/DM gendisk (top)
591 * @bdev: the underlying block device (bottom)
592 * @offset: offset to beginning of data within component device
595 * Merges the limits for two queues. Returns 0 if alignment
596 * didn't change. Returns -1 if adding the bottom device caused
599 void disk_stack_limits(struct gendisk
*disk
, struct block_device
*bdev
,
602 struct request_queue
*t
= disk
->queue
;
603 struct request_queue
*b
= bdev_get_queue(bdev
);
605 offset
+= get_start_sect(bdev
) << 9;
607 if (blk_stack_limits(&t
->limits
, &b
->limits
, offset
) < 0) {
608 char top
[BDEVNAME_SIZE
], bottom
[BDEVNAME_SIZE
];
610 disk_name(disk
, 0, top
);
611 bdevname(bdev
, bottom
);
613 printk(KERN_NOTICE
"%s: Warning: Device %s is misaligned\n",
619 else if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
)) {
622 spin_lock_irqsave(t
->queue_lock
, flags
);
623 if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
))
624 queue_flag_clear(QUEUE_FLAG_CLUSTER
, t
);
625 spin_unlock_irqrestore(t
->queue_lock
, flags
);
628 EXPORT_SYMBOL(disk_stack_limits
);
631 * blk_queue_dma_pad - set pad mask
632 * @q: the request queue for the device
637 * Appending pad buffer to a request modifies the last entry of a
638 * scatter list such that it includes the pad buffer.
640 void blk_queue_dma_pad(struct request_queue
*q
, unsigned int mask
)
642 q
->dma_pad_mask
= mask
;
644 EXPORT_SYMBOL(blk_queue_dma_pad
);
647 * blk_queue_update_dma_pad - update pad mask
648 * @q: the request queue for the device
651 * Update dma pad mask.
653 * Appending pad buffer to a request modifies the last entry of a
654 * scatter list such that it includes the pad buffer.
656 void blk_queue_update_dma_pad(struct request_queue
*q
, unsigned int mask
)
658 if (mask
> q
->dma_pad_mask
)
659 q
->dma_pad_mask
= mask
;
661 EXPORT_SYMBOL(blk_queue_update_dma_pad
);
664 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
665 * @q: the request queue for the device
666 * @dma_drain_needed: fn which returns non-zero if drain is necessary
667 * @buf: physically contiguous buffer
668 * @size: size of the buffer in bytes
670 * Some devices have excess DMA problems and can't simply discard (or
671 * zero fill) the unwanted piece of the transfer. They have to have a
672 * real area of memory to transfer it into. The use case for this is
673 * ATAPI devices in DMA mode. If the packet command causes a transfer
674 * bigger than the transfer size some HBAs will lock up if there
675 * aren't DMA elements to contain the excess transfer. What this API
676 * does is adjust the queue so that the buf is always appended
677 * silently to the scatterlist.
679 * Note: This routine adjusts max_hw_segments to make room for
680 * appending the drain buffer. If you call
681 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
682 * calling this routine, you must set the limit to one fewer than your
683 * device can support otherwise there won't be room for the drain
686 int blk_queue_dma_drain(struct request_queue
*q
,
687 dma_drain_needed_fn
*dma_drain_needed
,
688 void *buf
, unsigned int size
)
690 if (queue_max_hw_segments(q
) < 2 || queue_max_phys_segments(q
) < 2)
692 /* make room for appending the drain */
693 blk_queue_max_hw_segments(q
, queue_max_hw_segments(q
) - 1);
694 blk_queue_max_phys_segments(q
, queue_max_phys_segments(q
) - 1);
695 q
->dma_drain_needed
= dma_drain_needed
;
696 q
->dma_drain_buffer
= buf
;
697 q
->dma_drain_size
= size
;
701 EXPORT_SYMBOL_GPL(blk_queue_dma_drain
);
704 * blk_queue_segment_boundary - set boundary rules for segment merging
705 * @q: the request queue for the device
706 * @mask: the memory boundary mask
708 void blk_queue_segment_boundary(struct request_queue
*q
, unsigned long mask
)
710 if (mask
< PAGE_CACHE_SIZE
- 1) {
711 mask
= PAGE_CACHE_SIZE
- 1;
712 printk(KERN_INFO
"%s: set to minimum %lx\n",
716 q
->limits
.seg_boundary_mask
= mask
;
718 EXPORT_SYMBOL(blk_queue_segment_boundary
);
721 * blk_queue_dma_alignment - set dma length and memory alignment
722 * @q: the request queue for the device
723 * @mask: alignment mask
726 * set required memory and length alignment for direct dma transactions.
727 * this is used when building direct io requests for the queue.
730 void blk_queue_dma_alignment(struct request_queue
*q
, int mask
)
732 q
->dma_alignment
= mask
;
734 EXPORT_SYMBOL(blk_queue_dma_alignment
);
737 * blk_queue_update_dma_alignment - update dma length and memory alignment
738 * @q: the request queue for the device
739 * @mask: alignment mask
742 * update required memory and length alignment for direct dma transactions.
743 * If the requested alignment is larger than the current alignment, then
744 * the current queue alignment is updated to the new value, otherwise it
745 * is left alone. The design of this is to allow multiple objects
746 * (driver, device, transport etc) to set their respective
747 * alignments without having them interfere.
750 void blk_queue_update_dma_alignment(struct request_queue
*q
, int mask
)
752 BUG_ON(mask
> PAGE_SIZE
);
754 if (mask
> q
->dma_alignment
)
755 q
->dma_alignment
= mask
;
757 EXPORT_SYMBOL(blk_queue_update_dma_alignment
);
759 static int __init
blk_settings_init(void)
761 blk_max_low_pfn
= max_low_pfn
- 1;
762 blk_max_pfn
= max_pfn
- 1;
765 subsys_initcall(blk_settings_init
);