2 * Functions related to setting various queue properties from drivers
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
8 #include <linux/blkdev.h>
9 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
10 #include <linux/gcd.h>
11 #include <linux/lcm.h>
12 #include <linux/jiffies.h>
13 #include <linux/gfp.h>
17 unsigned long blk_max_low_pfn
;
18 EXPORT_SYMBOL(blk_max_low_pfn
);
20 unsigned long blk_max_pfn
;
23 * blk_queue_prep_rq - set a prepare_request function for queue
25 * @pfn: prepare_request function
27 * It's possible for a queue to register a prepare_request callback which
28 * is invoked before the request is handed to the request_fn. The goal of
29 * the function is to prepare a request for I/O, it can be used to build a
30 * cdb from the request data for instance.
33 void blk_queue_prep_rq(struct request_queue
*q
, prep_rq_fn
*pfn
)
37 EXPORT_SYMBOL(blk_queue_prep_rq
);
40 * blk_queue_merge_bvec - set a merge_bvec function for queue
42 * @mbfn: merge_bvec_fn
44 * Usually queues have static limitations on the max sectors or segments that
45 * we can put in a request. Stacking drivers may have some settings that
46 * are dynamic, and thus we have to query the queue whether it is ok to
47 * add a new bio_vec to a bio at a given offset or not. If the block device
48 * has such limitations, it needs to register a merge_bvec_fn to control
49 * the size of bio's sent to it. Note that a block device *must* allow a
50 * single page to be added to an empty bio. The block device driver may want
51 * to use the bio_split() function to deal with these bio's. By default
52 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
55 void blk_queue_merge_bvec(struct request_queue
*q
, merge_bvec_fn
*mbfn
)
57 q
->merge_bvec_fn
= mbfn
;
59 EXPORT_SYMBOL(blk_queue_merge_bvec
);
61 void blk_queue_softirq_done(struct request_queue
*q
, softirq_done_fn
*fn
)
63 q
->softirq_done_fn
= fn
;
65 EXPORT_SYMBOL(blk_queue_softirq_done
);
67 void blk_queue_rq_timeout(struct request_queue
*q
, unsigned int timeout
)
69 q
->rq_timeout
= timeout
;
71 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout
);
73 void blk_queue_rq_timed_out(struct request_queue
*q
, rq_timed_out_fn
*fn
)
75 q
->rq_timed_out_fn
= fn
;
77 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out
);
79 void blk_queue_lld_busy(struct request_queue
*q
, lld_busy_fn
*fn
)
83 EXPORT_SYMBOL_GPL(blk_queue_lld_busy
);
86 * blk_set_default_limits - reset limits to default values
87 * @lim: the queue_limits structure to reset
90 * Returns a queue_limit struct to its default state. Can be used by
91 * stacking drivers like DM that stage table swaps and reuse an
92 * existing device queue.
94 void blk_set_default_limits(struct queue_limits
*lim
)
96 lim
->max_segments
= BLK_MAX_SEGMENTS
;
97 lim
->seg_boundary_mask
= BLK_SEG_BOUNDARY_MASK
;
98 lim
->max_segment_size
= BLK_MAX_SEGMENT_SIZE
;
99 lim
->max_sectors
= BLK_DEF_MAX_SECTORS
;
100 lim
->max_hw_sectors
= INT_MAX
;
101 lim
->max_discard_sectors
= 0;
102 lim
->discard_granularity
= 0;
103 lim
->discard_alignment
= 0;
104 lim
->discard_misaligned
= 0;
105 lim
->discard_zeroes_data
= -1;
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;
113 EXPORT_SYMBOL(blk_set_default_limits
);
116 * blk_queue_make_request - define an alternate make_request function for a device
117 * @q: the request queue for the device to be affected
118 * @mfn: the alternate make_request function
121 * The normal way for &struct bios to be passed to a device
122 * driver is for them to be collected into requests on a request
123 * queue, and then to allow the device driver to select requests
124 * off that queue when it is ready. This works well for many block
125 * devices. However some block devices (typically virtual devices
126 * such as md or lvm) do not benefit from the processing on the
127 * request queue, and are served best by having the requests passed
128 * directly to them. This can be achieved by providing a function
129 * to blk_queue_make_request().
132 * The driver that does this *must* be able to deal appropriately
133 * with buffers in "highmemory". This can be accomplished by either calling
134 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
135 * blk_queue_bounce() to create a buffer in normal memory.
137 void blk_queue_make_request(struct request_queue
*q
, make_request_fn
*mfn
)
142 q
->nr_requests
= BLKDEV_MAX_RQ
;
144 q
->make_request_fn
= mfn
;
145 blk_queue_dma_alignment(q
, 511);
146 blk_queue_congestion_threshold(q
);
147 q
->nr_batching
= BLK_BATCH_REQ
;
149 q
->unplug_thresh
= 4; /* hmm */
150 q
->unplug_delay
= msecs_to_jiffies(3); /* 3 milliseconds */
151 if (q
->unplug_delay
== 0)
154 q
->unplug_timer
.function
= blk_unplug_timeout
;
155 q
->unplug_timer
.data
= (unsigned long)q
;
157 blk_set_default_limits(&q
->limits
);
158 blk_queue_max_hw_sectors(q
, BLK_SAFE_MAX_SECTORS
);
161 * If the caller didn't supply a lock, fall back to our embedded
165 q
->queue_lock
= &q
->__queue_lock
;
168 * by default assume old behaviour and bounce for any highmem page
170 blk_queue_bounce_limit(q
, BLK_BOUNCE_HIGH
);
172 EXPORT_SYMBOL(blk_queue_make_request
);
175 * blk_queue_bounce_limit - set bounce buffer limit for queue
176 * @q: the request queue for the device
177 * @dma_mask: the maximum address the device can handle
180 * Different hardware can have different requirements as to what pages
181 * it can do I/O directly to. A low level driver can call
182 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
183 * buffers for doing I/O to pages residing above @dma_mask.
185 void blk_queue_bounce_limit(struct request_queue
*q
, u64 dma_mask
)
187 unsigned long b_pfn
= dma_mask
>> PAGE_SHIFT
;
190 q
->bounce_gfp
= GFP_NOIO
;
191 #if BITS_PER_LONG == 64
193 * Assume anything <= 4GB can be handled by IOMMU. Actually
194 * some IOMMUs can handle everything, but I don't know of a
195 * way to test this here.
197 if (b_pfn
< (min_t(u64
, 0xffffffffUL
, BLK_BOUNCE_HIGH
) >> PAGE_SHIFT
))
199 q
->limits
.bounce_pfn
= max_low_pfn
;
201 if (b_pfn
< blk_max_low_pfn
)
203 q
->limits
.bounce_pfn
= b_pfn
;
206 init_emergency_isa_pool();
207 q
->bounce_gfp
= GFP_NOIO
| GFP_DMA
;
208 q
->limits
.bounce_pfn
= b_pfn
;
211 EXPORT_SYMBOL(blk_queue_bounce_limit
);
214 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
215 * @q: the request queue for the device
216 * @max_hw_sectors: max hardware sectors in the usual 512b unit
219 * Enables a low level driver to set a hard upper limit,
220 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
221 * the device driver based upon the combined capabilities of I/O
222 * controller and storage device.
224 * max_sectors is a soft limit imposed by the block layer for
225 * filesystem type requests. This value can be overridden on a
226 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
227 * The soft limit can not exceed max_hw_sectors.
229 void blk_queue_max_hw_sectors(struct request_queue
*q
, unsigned int max_hw_sectors
)
231 if ((max_hw_sectors
<< 9) < PAGE_CACHE_SIZE
) {
232 max_hw_sectors
= 1 << (PAGE_CACHE_SHIFT
- 9);
233 printk(KERN_INFO
"%s: set to minimum %d\n",
234 __func__
, max_hw_sectors
);
237 q
->limits
.max_hw_sectors
= max_hw_sectors
;
238 q
->limits
.max_sectors
= min_t(unsigned int, max_hw_sectors
,
239 BLK_DEF_MAX_SECTORS
);
241 EXPORT_SYMBOL(blk_queue_max_hw_sectors
);
244 * blk_queue_max_discard_sectors - set max sectors for a single discard
245 * @q: the request queue for the device
246 * @max_discard_sectors: maximum number of sectors to discard
248 void blk_queue_max_discard_sectors(struct request_queue
*q
,
249 unsigned int max_discard_sectors
)
251 q
->limits
.max_discard_sectors
= max_discard_sectors
;
253 EXPORT_SYMBOL(blk_queue_max_discard_sectors
);
256 * blk_queue_max_segments - set max hw segments for a request for this queue
257 * @q: the request queue for the device
258 * @max_segments: max number of segments
261 * Enables a low level driver to set an upper limit on the number of
262 * hw data segments in a request.
264 void blk_queue_max_segments(struct request_queue
*q
, unsigned short max_segments
)
268 printk(KERN_INFO
"%s: set to minimum %d\n",
269 __func__
, max_segments
);
272 q
->limits
.max_segments
= max_segments
;
274 EXPORT_SYMBOL(blk_queue_max_segments
);
277 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
278 * @q: the request queue for the device
279 * @max_size: max size of segment in bytes
282 * Enables a low level driver to set an upper limit on the size of a
285 void blk_queue_max_segment_size(struct request_queue
*q
, unsigned int max_size
)
287 if (max_size
< PAGE_CACHE_SIZE
) {
288 max_size
= PAGE_CACHE_SIZE
;
289 printk(KERN_INFO
"%s: set to minimum %d\n",
293 q
->limits
.max_segment_size
= max_size
;
295 EXPORT_SYMBOL(blk_queue_max_segment_size
);
298 * blk_queue_logical_block_size - set logical block size for the queue
299 * @q: the request queue for the device
300 * @size: the logical block size, in bytes
303 * This should be set to the lowest possible block size that the
304 * storage device can address. The default of 512 covers most
307 void blk_queue_logical_block_size(struct request_queue
*q
, unsigned short size
)
309 q
->limits
.logical_block_size
= size
;
311 if (q
->limits
.physical_block_size
< size
)
312 q
->limits
.physical_block_size
= size
;
314 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
315 q
->limits
.io_min
= q
->limits
.physical_block_size
;
317 EXPORT_SYMBOL(blk_queue_logical_block_size
);
320 * blk_queue_physical_block_size - set physical block size for the queue
321 * @q: the request queue for the device
322 * @size: the physical block size, in bytes
325 * This should be set to the lowest possible sector size that the
326 * hardware can operate on without reverting to read-modify-write
329 void blk_queue_physical_block_size(struct request_queue
*q
, unsigned int size
)
331 q
->limits
.physical_block_size
= size
;
333 if (q
->limits
.physical_block_size
< q
->limits
.logical_block_size
)
334 q
->limits
.physical_block_size
= q
->limits
.logical_block_size
;
336 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
337 q
->limits
.io_min
= q
->limits
.physical_block_size
;
339 EXPORT_SYMBOL(blk_queue_physical_block_size
);
342 * blk_queue_alignment_offset - set physical block alignment offset
343 * @q: the request queue for the device
344 * @offset: alignment offset in bytes
347 * Some devices are naturally misaligned to compensate for things like
348 * the legacy DOS partition table 63-sector offset. Low-level drivers
349 * should call this function for devices whose first sector is not
352 void blk_queue_alignment_offset(struct request_queue
*q
, unsigned int offset
)
354 q
->limits
.alignment_offset
=
355 offset
& (q
->limits
.physical_block_size
- 1);
356 q
->limits
.misaligned
= 0;
358 EXPORT_SYMBOL(blk_queue_alignment_offset
);
361 * blk_limits_io_min - set minimum request size for a device
362 * @limits: the queue limits
363 * @min: smallest I/O size in bytes
366 * Some devices have an internal block size bigger than the reported
367 * hardware sector size. This function can be used to signal the
368 * smallest I/O the device can perform without incurring a performance
371 void blk_limits_io_min(struct queue_limits
*limits
, unsigned int min
)
373 limits
->io_min
= min
;
375 if (limits
->io_min
< limits
->logical_block_size
)
376 limits
->io_min
= limits
->logical_block_size
;
378 if (limits
->io_min
< limits
->physical_block_size
)
379 limits
->io_min
= limits
->physical_block_size
;
381 EXPORT_SYMBOL(blk_limits_io_min
);
384 * blk_queue_io_min - set minimum request size for the queue
385 * @q: the request queue for the device
386 * @min: smallest I/O size in bytes
389 * Storage devices may report a granularity or preferred minimum I/O
390 * size which is the smallest request the device can perform without
391 * incurring a performance penalty. For disk drives this is often the
392 * physical block size. For RAID arrays it is often the stripe chunk
393 * size. A properly aligned multiple of minimum_io_size is the
394 * preferred request size for workloads where a high number of I/O
395 * operations is desired.
397 void blk_queue_io_min(struct request_queue
*q
, unsigned int min
)
399 blk_limits_io_min(&q
->limits
, min
);
401 EXPORT_SYMBOL(blk_queue_io_min
);
404 * blk_limits_io_opt - set optimal request size for a device
405 * @limits: the queue limits
406 * @opt: smallest I/O size in bytes
409 * Storage devices may report an optimal I/O size, which is the
410 * device's preferred unit for sustained I/O. This is rarely reported
411 * for disk drives. For RAID arrays it is usually the stripe width or
412 * the internal track size. A properly aligned multiple of
413 * optimal_io_size is the preferred request size for workloads where
414 * sustained throughput is desired.
416 void blk_limits_io_opt(struct queue_limits
*limits
, unsigned int opt
)
418 limits
->io_opt
= opt
;
420 EXPORT_SYMBOL(blk_limits_io_opt
);
423 * blk_queue_io_opt - set optimal request size for the queue
424 * @q: the request queue for the device
425 * @opt: optimal request size in bytes
428 * Storage devices may report an optimal I/O size, which is the
429 * device's preferred unit for sustained I/O. This is rarely reported
430 * for disk drives. For RAID arrays it is usually the stripe width or
431 * the internal track size. A properly aligned multiple of
432 * optimal_io_size is the preferred request size for workloads where
433 * sustained throughput is desired.
435 void blk_queue_io_opt(struct request_queue
*q
, unsigned int opt
)
437 blk_limits_io_opt(&q
->limits
, opt
);
439 EXPORT_SYMBOL(blk_queue_io_opt
);
442 * Returns the minimum that is _not_ zero, unless both are zero.
444 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
447 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
448 * @t: the stacking driver (top)
449 * @b: the underlying device (bottom)
451 void blk_queue_stack_limits(struct request_queue
*t
, struct request_queue
*b
)
453 blk_stack_limits(&t
->limits
, &b
->limits
, 0);
455 EXPORT_SYMBOL(blk_queue_stack_limits
);
458 * blk_stack_limits - adjust queue_limits for stacked devices
459 * @t: the stacking driver limits (top device)
460 * @b: the underlying queue limits (bottom, component device)
461 * @start: first data sector within component device
464 * This function is used by stacking drivers like MD and DM to ensure
465 * that all component devices have compatible block sizes and
466 * alignments. The stacking driver must provide a queue_limits
467 * struct (top) and then iteratively call the stacking function for
468 * all component (bottom) devices. The stacking function will
469 * attempt to combine the values and ensure proper alignment.
471 * Returns 0 if the top and bottom queue_limits are compatible. The
472 * top device's block sizes and alignment offsets may be adjusted to
473 * ensure alignment with the bottom device. If no compatible sizes
474 * and alignments exist, -1 is returned and the resulting top
475 * queue_limits will have the misaligned flag set to indicate that
476 * the alignment_offset is undefined.
478 int blk_stack_limits(struct queue_limits
*t
, struct queue_limits
*b
,
481 unsigned int top
, bottom
, alignment
, ret
= 0;
483 t
->max_sectors
= min_not_zero(t
->max_sectors
, b
->max_sectors
);
484 t
->max_hw_sectors
= min_not_zero(t
->max_hw_sectors
, b
->max_hw_sectors
);
485 t
->bounce_pfn
= min_not_zero(t
->bounce_pfn
, b
->bounce_pfn
);
487 t
->seg_boundary_mask
= min_not_zero(t
->seg_boundary_mask
,
488 b
->seg_boundary_mask
);
490 t
->max_segments
= min_not_zero(t
->max_segments
, b
->max_segments
);
492 t
->max_segment_size
= min_not_zero(t
->max_segment_size
,
493 b
->max_segment_size
);
495 t
->misaligned
|= b
->misaligned
;
497 alignment
= queue_limit_alignment_offset(b
, start
);
499 /* Bottom device has different alignment. Check that it is
500 * compatible with the current top alignment.
502 if (t
->alignment_offset
!= alignment
) {
504 top
= max(t
->physical_block_size
, t
->io_min
)
505 + t
->alignment_offset
;
506 bottom
= max(b
->physical_block_size
, b
->io_min
) + alignment
;
508 /* Verify that top and bottom intervals line up */
509 if (max(top
, bottom
) & (min(top
, bottom
) - 1)) {
515 t
->logical_block_size
= max(t
->logical_block_size
,
516 b
->logical_block_size
);
518 t
->physical_block_size
= max(t
->physical_block_size
,
519 b
->physical_block_size
);
521 t
->io_min
= max(t
->io_min
, b
->io_min
);
522 t
->io_opt
= lcm(t
->io_opt
, b
->io_opt
);
524 t
->cluster
&= b
->cluster
;
525 t
->discard_zeroes_data
&= b
->discard_zeroes_data
;
527 /* Physical block size a multiple of the logical block size? */
528 if (t
->physical_block_size
& (t
->logical_block_size
- 1)) {
529 t
->physical_block_size
= t
->logical_block_size
;
534 /* Minimum I/O a multiple of the physical block size? */
535 if (t
->io_min
& (t
->physical_block_size
- 1)) {
536 t
->io_min
= t
->physical_block_size
;
541 /* Optimal I/O a multiple of the physical block size? */
542 if (t
->io_opt
& (t
->physical_block_size
- 1)) {
548 /* Find lowest common alignment_offset */
549 t
->alignment_offset
= lcm(t
->alignment_offset
, alignment
)
550 & (max(t
->physical_block_size
, t
->io_min
) - 1);
552 /* Verify that new alignment_offset is on a logical block boundary */
553 if (t
->alignment_offset
& (t
->logical_block_size
- 1)) {
558 /* Discard alignment and granularity */
559 if (b
->discard_granularity
) {
560 alignment
= queue_limit_discard_alignment(b
, start
);
562 if (t
->discard_granularity
!= 0 &&
563 t
->discard_alignment
!= alignment
) {
564 top
= t
->discard_granularity
+ t
->discard_alignment
;
565 bottom
= b
->discard_granularity
+ alignment
;
567 /* Verify that top and bottom intervals line up */
568 if (max(top
, bottom
) & (min(top
, bottom
) - 1))
569 t
->discard_misaligned
= 1;
572 t
->max_discard_sectors
= min_not_zero(t
->max_discard_sectors
,
573 b
->max_discard_sectors
);
574 t
->discard_granularity
= max(t
->discard_granularity
,
575 b
->discard_granularity
);
576 t
->discard_alignment
= lcm(t
->discard_alignment
, alignment
) &
577 (t
->discard_granularity
- 1);
582 EXPORT_SYMBOL(blk_stack_limits
);
585 * bdev_stack_limits - adjust queue limits for stacked drivers
586 * @t: the stacking driver limits (top device)
587 * @bdev: the component block_device (bottom)
588 * @start: first data sector within component device
591 * Merges queue limits for a top device and a block_device. Returns
592 * 0 if alignment didn't change. Returns -1 if adding the bottom
593 * device caused misalignment.
595 int bdev_stack_limits(struct queue_limits
*t
, struct block_device
*bdev
,
598 struct request_queue
*bq
= bdev_get_queue(bdev
);
600 start
+= get_start_sect(bdev
);
602 return blk_stack_limits(t
, &bq
->limits
, start
);
604 EXPORT_SYMBOL(bdev_stack_limits
);
607 * disk_stack_limits - adjust queue limits for stacked drivers
608 * @disk: MD/DM gendisk (top)
609 * @bdev: the underlying block device (bottom)
610 * @offset: offset to beginning of data within component device
613 * Merges the limits for a top level gendisk and a bottom level
616 void disk_stack_limits(struct gendisk
*disk
, struct block_device
*bdev
,
619 struct request_queue
*t
= disk
->queue
;
621 if (bdev_stack_limits(&t
->limits
, bdev
, offset
>> 9) < 0) {
622 char top
[BDEVNAME_SIZE
], bottom
[BDEVNAME_SIZE
];
624 disk_name(disk
, 0, top
);
625 bdevname(bdev
, bottom
);
627 printk(KERN_NOTICE
"%s: Warning: Device %s is misaligned\n",
631 EXPORT_SYMBOL(disk_stack_limits
);
634 * blk_queue_dma_pad - set pad mask
635 * @q: the request queue for the device
640 * Appending pad buffer to a request modifies the last entry of a
641 * scatter list such that it includes the pad buffer.
643 void blk_queue_dma_pad(struct request_queue
*q
, unsigned int mask
)
645 q
->dma_pad_mask
= mask
;
647 EXPORT_SYMBOL(blk_queue_dma_pad
);
650 * blk_queue_update_dma_pad - update pad mask
651 * @q: the request queue for the device
654 * Update dma pad mask.
656 * Appending pad buffer to a request modifies the last entry of a
657 * scatter list such that it includes the pad buffer.
659 void blk_queue_update_dma_pad(struct request_queue
*q
, unsigned int mask
)
661 if (mask
> q
->dma_pad_mask
)
662 q
->dma_pad_mask
= mask
;
664 EXPORT_SYMBOL(blk_queue_update_dma_pad
);
667 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
668 * @q: the request queue for the device
669 * @dma_drain_needed: fn which returns non-zero if drain is necessary
670 * @buf: physically contiguous buffer
671 * @size: size of the buffer in bytes
673 * Some devices have excess DMA problems and can't simply discard (or
674 * zero fill) the unwanted piece of the transfer. They have to have a
675 * real area of memory to transfer it into. The use case for this is
676 * ATAPI devices in DMA mode. If the packet command causes a transfer
677 * bigger than the transfer size some HBAs will lock up if there
678 * aren't DMA elements to contain the excess transfer. What this API
679 * does is adjust the queue so that the buf is always appended
680 * silently to the scatterlist.
682 * Note: This routine adjusts max_hw_segments to make room for appending
683 * the drain buffer. If you call blk_queue_max_segments() after calling
684 * this routine, you must set the limit to one fewer than your device
685 * can support otherwise there won't be room for the drain buffer.
687 int blk_queue_dma_drain(struct request_queue
*q
,
688 dma_drain_needed_fn
*dma_drain_needed
,
689 void *buf
, unsigned int size
)
691 if (queue_max_segments(q
) < 2)
693 /* make room for appending the drain */
694 blk_queue_max_segments(q
, queue_max_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
);