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>
16 unsigned long blk_max_low_pfn
;
17 EXPORT_SYMBOL(blk_max_low_pfn
);
19 unsigned long blk_max_pfn
;
22 * blk_queue_prep_rq - set a prepare_request function for queue
24 * @pfn: prepare_request function
26 * It's possible for a queue to register a prepare_request callback which
27 * is invoked before the request is handed to the request_fn. The goal of
28 * the function is to prepare a request for I/O, it can be used to build a
29 * cdb from the request data for instance.
32 void blk_queue_prep_rq(struct request_queue
*q
, prep_rq_fn
*pfn
)
36 EXPORT_SYMBOL(blk_queue_prep_rq
);
39 * blk_queue_merge_bvec - set a merge_bvec function for queue
41 * @mbfn: merge_bvec_fn
43 * Usually queues have static limitations on the max sectors or segments that
44 * we can put in a request. Stacking drivers may have some settings that
45 * are dynamic, and thus we have to query the queue whether it is ok to
46 * add a new bio_vec to a bio at a given offset or not. If the block device
47 * has such limitations, it needs to register a merge_bvec_fn to control
48 * the size of bio's sent to it. Note that a block device *must* allow a
49 * single page to be added to an empty bio. The block device driver may want
50 * to use the bio_split() function to deal with these bio's. By default
51 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
54 void blk_queue_merge_bvec(struct request_queue
*q
, merge_bvec_fn
*mbfn
)
56 q
->merge_bvec_fn
= mbfn
;
58 EXPORT_SYMBOL(blk_queue_merge_bvec
);
60 void blk_queue_softirq_done(struct request_queue
*q
, softirq_done_fn
*fn
)
62 q
->softirq_done_fn
= fn
;
64 EXPORT_SYMBOL(blk_queue_softirq_done
);
66 void blk_queue_rq_timeout(struct request_queue
*q
, unsigned int timeout
)
68 q
->rq_timeout
= timeout
;
70 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout
);
72 void blk_queue_rq_timed_out(struct request_queue
*q
, rq_timed_out_fn
*fn
)
74 q
->rq_timed_out_fn
= fn
;
76 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out
);
78 void blk_queue_lld_busy(struct request_queue
*q
, lld_busy_fn
*fn
)
82 EXPORT_SYMBOL_GPL(blk_queue_lld_busy
);
85 * blk_set_default_limits - reset limits to default values
86 * @lim: the queue_limits structure to reset
89 * Returns a queue_limit struct to its default state. Can be used by
90 * stacking drivers like DM that stage table swaps and reuse an
91 * existing device queue.
93 void blk_set_default_limits(struct queue_limits
*lim
)
95 lim
->max_segments
= BLK_MAX_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_hw_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_hw_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_hw_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_hw_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_segments - set max hw 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 * hw data segments in a request.
263 void blk_queue_max_segments(struct request_queue
*q
, unsigned short max_segments
)
267 printk(KERN_INFO
"%s: set to minimum %d\n",
268 __func__
, max_segments
);
271 q
->limits
.max_segments
= max_segments
;
273 EXPORT_SYMBOL(blk_queue_max_segments
);
276 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
277 * @q: the request queue for the device
278 * @max_size: max size of segment in bytes
281 * Enables a low level driver to set an upper limit on the size of a
284 void blk_queue_max_segment_size(struct request_queue
*q
, unsigned int max_size
)
286 if (max_size
< PAGE_CACHE_SIZE
) {
287 max_size
= PAGE_CACHE_SIZE
;
288 printk(KERN_INFO
"%s: set to minimum %d\n",
292 q
->limits
.max_segment_size
= max_size
;
294 EXPORT_SYMBOL(blk_queue_max_segment_size
);
297 * blk_queue_logical_block_size - set logical block size for the queue
298 * @q: the request queue for the device
299 * @size: the logical block size, in bytes
302 * This should be set to the lowest possible block size that the
303 * storage device can address. The default of 512 covers most
306 void blk_queue_logical_block_size(struct request_queue
*q
, unsigned short size
)
308 q
->limits
.logical_block_size
= size
;
310 if (q
->limits
.physical_block_size
< size
)
311 q
->limits
.physical_block_size
= size
;
313 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
314 q
->limits
.io_min
= q
->limits
.physical_block_size
;
316 EXPORT_SYMBOL(blk_queue_logical_block_size
);
319 * blk_queue_physical_block_size - set physical block size for the queue
320 * @q: the request queue for the device
321 * @size: the physical block size, in bytes
324 * This should be set to the lowest possible sector size that the
325 * hardware can operate on without reverting to read-modify-write
328 void blk_queue_physical_block_size(struct request_queue
*q
, unsigned short size
)
330 q
->limits
.physical_block_size
= size
;
332 if (q
->limits
.physical_block_size
< q
->limits
.logical_block_size
)
333 q
->limits
.physical_block_size
= q
->limits
.logical_block_size
;
335 if (q
->limits
.io_min
< q
->limits
.physical_block_size
)
336 q
->limits
.io_min
= q
->limits
.physical_block_size
;
338 EXPORT_SYMBOL(blk_queue_physical_block_size
);
341 * blk_queue_alignment_offset - set physical block alignment offset
342 * @q: the request queue for the device
343 * @offset: alignment offset in bytes
346 * Some devices are naturally misaligned to compensate for things like
347 * the legacy DOS partition table 63-sector offset. Low-level drivers
348 * should call this function for devices whose first sector is not
351 void blk_queue_alignment_offset(struct request_queue
*q
, unsigned int offset
)
353 q
->limits
.alignment_offset
=
354 offset
& (q
->limits
.physical_block_size
- 1);
355 q
->limits
.misaligned
= 0;
357 EXPORT_SYMBOL(blk_queue_alignment_offset
);
360 * blk_limits_io_min - set minimum request size for a device
361 * @limits: the queue limits
362 * @min: smallest I/O size in bytes
365 * Some devices have an internal block size bigger than the reported
366 * hardware sector size. This function can be used to signal the
367 * smallest I/O the device can perform without incurring a performance
370 void blk_limits_io_min(struct queue_limits
*limits
, unsigned int min
)
372 limits
->io_min
= min
;
374 if (limits
->io_min
< limits
->logical_block_size
)
375 limits
->io_min
= limits
->logical_block_size
;
377 if (limits
->io_min
< limits
->physical_block_size
)
378 limits
->io_min
= limits
->physical_block_size
;
380 EXPORT_SYMBOL(blk_limits_io_min
);
383 * blk_queue_io_min - set minimum request size for the queue
384 * @q: the request queue for the device
385 * @min: smallest I/O size in bytes
388 * Storage devices may report a granularity or preferred minimum I/O
389 * size which is the smallest request the device can perform without
390 * incurring a performance penalty. For disk drives this is often the
391 * physical block size. For RAID arrays it is often the stripe chunk
392 * size. A properly aligned multiple of minimum_io_size is the
393 * preferred request size for workloads where a high number of I/O
394 * operations is desired.
396 void blk_queue_io_min(struct request_queue
*q
, unsigned int min
)
398 blk_limits_io_min(&q
->limits
, min
);
400 EXPORT_SYMBOL(blk_queue_io_min
);
403 * blk_limits_io_opt - set optimal request size for a device
404 * @limits: the queue limits
405 * @opt: smallest I/O size in bytes
408 * Storage devices may report an optimal I/O size, which is the
409 * device's preferred unit for sustained I/O. This is rarely reported
410 * for disk drives. For RAID arrays it is usually the stripe width or
411 * the internal track size. A properly aligned multiple of
412 * optimal_io_size is the preferred request size for workloads where
413 * sustained throughput is desired.
415 void blk_limits_io_opt(struct queue_limits
*limits
, unsigned int opt
)
417 limits
->io_opt
= opt
;
419 EXPORT_SYMBOL(blk_limits_io_opt
);
422 * blk_queue_io_opt - set optimal request size for the queue
423 * @q: the request queue for the device
424 * @opt: optimal request size in bytes
427 * Storage devices may report an optimal I/O size, which is the
428 * device's preferred unit for sustained I/O. This is rarely reported
429 * for disk drives. For RAID arrays it is usually the stripe width or
430 * the internal track size. A properly aligned multiple of
431 * optimal_io_size is the preferred request size for workloads where
432 * sustained throughput is desired.
434 void blk_queue_io_opt(struct request_queue
*q
, unsigned int opt
)
436 blk_limits_io_opt(&q
->limits
, opt
);
438 EXPORT_SYMBOL(blk_queue_io_opt
);
441 * Returns the minimum that is _not_ zero, unless both are zero.
443 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
446 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
447 * @t: the stacking driver (top)
448 * @b: the underlying device (bottom)
450 void blk_queue_stack_limits(struct request_queue
*t
, struct request_queue
*b
)
452 blk_stack_limits(&t
->limits
, &b
->limits
, 0);
456 else if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
)) {
458 spin_lock_irqsave(t
->queue_lock
, flags
);
459 queue_flag_clear(QUEUE_FLAG_CLUSTER
, t
);
460 spin_unlock_irqrestore(t
->queue_lock
, flags
);
463 EXPORT_SYMBOL(blk_queue_stack_limits
);
466 * blk_stack_limits - adjust queue_limits for stacked devices
467 * @t: the stacking driver limits (top device)
468 * @b: the underlying queue limits (bottom, component device)
469 * @start: first data sector within component device
472 * This function is used by stacking drivers like MD and DM to ensure
473 * that all component devices have compatible block sizes and
474 * alignments. The stacking driver must provide a queue_limits
475 * struct (top) and then iteratively call the stacking function for
476 * all component (bottom) devices. The stacking function will
477 * attempt to combine the values and ensure proper alignment.
479 * Returns 0 if the top and bottom queue_limits are compatible. The
480 * top device's block sizes and alignment offsets may be adjusted to
481 * ensure alignment with the bottom device. If no compatible sizes
482 * and alignments exist, -1 is returned and the resulting top
483 * queue_limits will have the misaligned flag set to indicate that
484 * the alignment_offset is undefined.
486 int blk_stack_limits(struct queue_limits
*t
, struct queue_limits
*b
,
489 unsigned int top
, bottom
, alignment
, ret
= 0;
491 t
->max_sectors
= min_not_zero(t
->max_sectors
, b
->max_sectors
);
492 t
->max_hw_sectors
= min_not_zero(t
->max_hw_sectors
, b
->max_hw_sectors
);
493 t
->bounce_pfn
= min_not_zero(t
->bounce_pfn
, b
->bounce_pfn
);
495 t
->seg_boundary_mask
= min_not_zero(t
->seg_boundary_mask
,
496 b
->seg_boundary_mask
);
498 t
->max_segments
= min_not_zero(t
->max_segments
, b
->max_segments
);
500 t
->max_segment_size
= min_not_zero(t
->max_segment_size
,
501 b
->max_segment_size
);
503 t
->misaligned
|= b
->misaligned
;
505 alignment
= queue_limit_alignment_offset(b
, start
);
507 /* Bottom device has different alignment. Check that it is
508 * compatible with the current top alignment.
510 if (t
->alignment_offset
!= alignment
) {
512 top
= max(t
->physical_block_size
, t
->io_min
)
513 + t
->alignment_offset
;
514 bottom
= max(b
->physical_block_size
, b
->io_min
) + alignment
;
516 /* Verify that top and bottom intervals line up */
517 if (max(top
, bottom
) & (min(top
, bottom
) - 1)) {
523 t
->logical_block_size
= max(t
->logical_block_size
,
524 b
->logical_block_size
);
526 t
->physical_block_size
= max(t
->physical_block_size
,
527 b
->physical_block_size
);
529 t
->io_min
= max(t
->io_min
, b
->io_min
);
530 t
->io_opt
= lcm(t
->io_opt
, b
->io_opt
);
532 t
->no_cluster
|= b
->no_cluster
;
533 t
->discard_zeroes_data
&= b
->discard_zeroes_data
;
535 /* Physical block size a multiple of the logical block size? */
536 if (t
->physical_block_size
& (t
->logical_block_size
- 1)) {
537 t
->physical_block_size
= t
->logical_block_size
;
542 /* Minimum I/O a multiple of the physical block size? */
543 if (t
->io_min
& (t
->physical_block_size
- 1)) {
544 t
->io_min
= t
->physical_block_size
;
549 /* Optimal I/O a multiple of the physical block size? */
550 if (t
->io_opt
& (t
->physical_block_size
- 1)) {
556 /* Find lowest common alignment_offset */
557 t
->alignment_offset
= lcm(t
->alignment_offset
, alignment
)
558 & (max(t
->physical_block_size
, t
->io_min
) - 1);
560 /* Verify that new alignment_offset is on a logical block boundary */
561 if (t
->alignment_offset
& (t
->logical_block_size
- 1)) {
566 /* Discard alignment and granularity */
567 if (b
->discard_granularity
) {
568 alignment
= queue_limit_discard_alignment(b
, start
);
570 if (t
->discard_granularity
!= 0 &&
571 t
->discard_alignment
!= alignment
) {
572 top
= t
->discard_granularity
+ t
->discard_alignment
;
573 bottom
= b
->discard_granularity
+ alignment
;
575 /* Verify that top and bottom intervals line up */
576 if (max(top
, bottom
) & (min(top
, bottom
) - 1))
577 t
->discard_misaligned
= 1;
580 t
->max_discard_sectors
= min_not_zero(t
->max_discard_sectors
,
581 b
->max_discard_sectors
);
582 t
->discard_granularity
= max(t
->discard_granularity
,
583 b
->discard_granularity
);
584 t
->discard_alignment
= lcm(t
->discard_alignment
, alignment
) &
585 (t
->discard_granularity
- 1);
590 EXPORT_SYMBOL(blk_stack_limits
);
593 * bdev_stack_limits - adjust queue limits for stacked drivers
594 * @t: the stacking driver limits (top device)
595 * @bdev: the component block_device (bottom)
596 * @start: first data sector within component device
599 * Merges queue limits for a top device and a block_device. Returns
600 * 0 if alignment didn't change. Returns -1 if adding the bottom
601 * device caused misalignment.
603 int bdev_stack_limits(struct queue_limits
*t
, struct block_device
*bdev
,
606 struct request_queue
*bq
= bdev_get_queue(bdev
);
608 start
+= get_start_sect(bdev
);
610 return blk_stack_limits(t
, &bq
->limits
, start
);
612 EXPORT_SYMBOL(bdev_stack_limits
);
615 * disk_stack_limits - adjust queue limits for stacked drivers
616 * @disk: MD/DM gendisk (top)
617 * @bdev: the underlying block device (bottom)
618 * @offset: offset to beginning of data within component device
621 * Merges the limits for a top level gendisk and a bottom level
624 void disk_stack_limits(struct gendisk
*disk
, struct block_device
*bdev
,
627 struct request_queue
*t
= disk
->queue
;
628 struct request_queue
*b
= bdev_get_queue(bdev
);
630 if (bdev_stack_limits(&t
->limits
, bdev
, offset
>> 9) < 0) {
631 char top
[BDEVNAME_SIZE
], bottom
[BDEVNAME_SIZE
];
633 disk_name(disk
, 0, top
);
634 bdevname(bdev
, bottom
);
636 printk(KERN_NOTICE
"%s: Warning: Device %s is misaligned\n",
642 else if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
)) {
645 spin_lock_irqsave(t
->queue_lock
, flags
);
646 if (!test_bit(QUEUE_FLAG_CLUSTER
, &b
->queue_flags
))
647 queue_flag_clear(QUEUE_FLAG_CLUSTER
, t
);
648 spin_unlock_irqrestore(t
->queue_lock
, flags
);
651 EXPORT_SYMBOL(disk_stack_limits
);
654 * blk_queue_dma_pad - set pad mask
655 * @q: the request queue for the device
660 * Appending pad buffer to a request modifies the last entry of a
661 * scatter list such that it includes the pad buffer.
663 void blk_queue_dma_pad(struct request_queue
*q
, unsigned int mask
)
665 q
->dma_pad_mask
= mask
;
667 EXPORT_SYMBOL(blk_queue_dma_pad
);
670 * blk_queue_update_dma_pad - update pad mask
671 * @q: the request queue for the device
674 * Update dma pad mask.
676 * Appending pad buffer to a request modifies the last entry of a
677 * scatter list such that it includes the pad buffer.
679 void blk_queue_update_dma_pad(struct request_queue
*q
, unsigned int mask
)
681 if (mask
> q
->dma_pad_mask
)
682 q
->dma_pad_mask
= mask
;
684 EXPORT_SYMBOL(blk_queue_update_dma_pad
);
687 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
688 * @q: the request queue for the device
689 * @dma_drain_needed: fn which returns non-zero if drain is necessary
690 * @buf: physically contiguous buffer
691 * @size: size of the buffer in bytes
693 * Some devices have excess DMA problems and can't simply discard (or
694 * zero fill) the unwanted piece of the transfer. They have to have a
695 * real area of memory to transfer it into. The use case for this is
696 * ATAPI devices in DMA mode. If the packet command causes a transfer
697 * bigger than the transfer size some HBAs will lock up if there
698 * aren't DMA elements to contain the excess transfer. What this API
699 * does is adjust the queue so that the buf is always appended
700 * silently to the scatterlist.
702 * Note: This routine adjusts max_hw_segments to make room for appending
703 * the drain buffer. If you call blk_queue_max_segments() after calling
704 * this routine, you must set the limit to one fewer than your device
705 * can support otherwise there won't be room for the drain buffer.
707 int blk_queue_dma_drain(struct request_queue
*q
,
708 dma_drain_needed_fn
*dma_drain_needed
,
709 void *buf
, unsigned int size
)
711 if (queue_max_segments(q
) < 2)
713 /* make room for appending the drain */
714 blk_queue_max_segments(q
, queue_max_segments(q
) - 1);
715 q
->dma_drain_needed
= dma_drain_needed
;
716 q
->dma_drain_buffer
= buf
;
717 q
->dma_drain_size
= size
;
721 EXPORT_SYMBOL_GPL(blk_queue_dma_drain
);
724 * blk_queue_segment_boundary - set boundary rules for segment merging
725 * @q: the request queue for the device
726 * @mask: the memory boundary mask
728 void blk_queue_segment_boundary(struct request_queue
*q
, unsigned long mask
)
730 if (mask
< PAGE_CACHE_SIZE
- 1) {
731 mask
= PAGE_CACHE_SIZE
- 1;
732 printk(KERN_INFO
"%s: set to minimum %lx\n",
736 q
->limits
.seg_boundary_mask
= mask
;
738 EXPORT_SYMBOL(blk_queue_segment_boundary
);
741 * blk_queue_dma_alignment - set dma length and memory alignment
742 * @q: the request queue for the device
743 * @mask: alignment mask
746 * set required memory and length alignment for direct dma transactions.
747 * this is used when building direct io requests for the queue.
750 void blk_queue_dma_alignment(struct request_queue
*q
, int mask
)
752 q
->dma_alignment
= mask
;
754 EXPORT_SYMBOL(blk_queue_dma_alignment
);
757 * blk_queue_update_dma_alignment - update dma length and memory alignment
758 * @q: the request queue for the device
759 * @mask: alignment mask
762 * update required memory and length alignment for direct dma transactions.
763 * If the requested alignment is larger than the current alignment, then
764 * the current queue alignment is updated to the new value, otherwise it
765 * is left alone. The design of this is to allow multiple objects
766 * (driver, device, transport etc) to set their respective
767 * alignments without having them interfere.
770 void blk_queue_update_dma_alignment(struct request_queue
*q
, int mask
)
772 BUG_ON(mask
> PAGE_SIZE
);
774 if (mask
> q
->dma_alignment
)
775 q
->dma_alignment
= mask
;
777 EXPORT_SYMBOL(blk_queue_update_dma_alignment
);
779 static int __init
blk_settings_init(void)
781 blk_max_low_pfn
= max_low_pfn
- 1;
782 blk_max_pfn
= max_pfn
- 1;
785 subsys_initcall(blk_settings_init
);