dm crypt: separate essiv allocation from initialisation
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / block / blk-settings.c
blob66d4aa8799b7517de258e3e334a69372154580a9
1 /*
2 * Functions related to setting various queue properties from drivers
3 */
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
7 #include <linux/bio.h>
8 #include <linux/blkdev.h>
9 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
10 #include <linux/gcd.h>
12 #include "blk.h"
14 unsigned long blk_max_low_pfn;
15 EXPORT_SYMBOL(blk_max_low_pfn);
17 unsigned long blk_max_pfn;
19 /**
20 * blk_queue_prep_rq - set a prepare_request function for queue
21 * @q: 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)
32 q->prep_rq_fn = pfn;
34 EXPORT_SYMBOL(blk_queue_prep_rq);
36 /**
37 * blk_queue_merge_bvec - set a merge_bvec function for queue
38 * @q: 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
50 * honored.
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)
78 q->lld_busy_fn = fn;
80 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
82 /**
83 * blk_set_default_limits - reset limits to default values
84 * @lim: the queue_limits structure to reset
86 * Description:
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 = SAFE_MAX_SECTORS;
100 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
101 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
102 lim->alignment_offset = 0;
103 lim->io_opt = 0;
104 lim->misaligned = 0;
105 lim->no_cluster = 0;
107 EXPORT_SYMBOL(blk_set_default_limits);
110 * blk_queue_make_request - define an alternate make_request function for a device
111 * @q: the request queue for the device to be affected
112 * @mfn: the alternate make_request function
114 * Description:
115 * The normal way for &struct bios to be passed to a device
116 * driver is for them to be collected into requests on a request
117 * queue, and then to allow the device driver to select requests
118 * off that queue when it is ready. This works well for many block
119 * devices. However some block devices (typically virtual devices
120 * such as md or lvm) do not benefit from the processing on the
121 * request queue, and are served best by having the requests passed
122 * directly to them. This can be achieved by providing a function
123 * to blk_queue_make_request().
125 * Caveat:
126 * The driver that does this *must* be able to deal appropriately
127 * with buffers in "highmemory". This can be accomplished by either calling
128 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
129 * blk_queue_bounce() to create a buffer in normal memory.
131 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
134 * set defaults
136 q->nr_requests = BLKDEV_MAX_RQ;
138 q->make_request_fn = mfn;
139 blk_queue_dma_alignment(q, 511);
140 blk_queue_congestion_threshold(q);
141 q->nr_batching = BLK_BATCH_REQ;
143 q->unplug_thresh = 4; /* hmm */
144 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
145 if (q->unplug_delay == 0)
146 q->unplug_delay = 1;
148 q->unplug_timer.function = blk_unplug_timeout;
149 q->unplug_timer.data = (unsigned long)q;
151 blk_set_default_limits(&q->limits);
152 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
155 * If the caller didn't supply a lock, fall back to our embedded
156 * per-queue locks
158 if (!q->queue_lock)
159 q->queue_lock = &q->__queue_lock;
162 * by default assume old behaviour and bounce for any highmem page
164 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
166 EXPORT_SYMBOL(blk_queue_make_request);
169 * blk_queue_bounce_limit - set bounce buffer limit for queue
170 * @q: the request queue for the device
171 * @dma_mask: the maximum address the device can handle
173 * Description:
174 * Different hardware can have different requirements as to what pages
175 * it can do I/O directly to. A low level driver can call
176 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
177 * buffers for doing I/O to pages residing above @dma_mask.
179 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
181 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
182 int dma = 0;
184 q->bounce_gfp = GFP_NOIO;
185 #if BITS_PER_LONG == 64
187 * Assume anything <= 4GB can be handled by IOMMU. Actually
188 * some IOMMUs can handle everything, but I don't know of a
189 * way to test this here.
191 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
192 dma = 1;
193 q->limits.bounce_pfn = max_low_pfn;
194 #else
195 if (b_pfn < blk_max_low_pfn)
196 dma = 1;
197 q->limits.bounce_pfn = b_pfn;
198 #endif
199 if (dma) {
200 init_emergency_isa_pool();
201 q->bounce_gfp = GFP_NOIO | GFP_DMA;
202 q->limits.bounce_pfn = b_pfn;
205 EXPORT_SYMBOL(blk_queue_bounce_limit);
208 * blk_queue_max_sectors - set max sectors for a request for this queue
209 * @q: the request queue for the device
210 * @max_sectors: max sectors in the usual 512b unit
212 * Description:
213 * Enables a low level driver to set an upper limit on the size of
214 * received requests.
216 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
218 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
219 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
220 printk(KERN_INFO "%s: set to minimum %d\n",
221 __func__, max_sectors);
224 if (BLK_DEF_MAX_SECTORS > max_sectors)
225 q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;
226 else {
227 q->limits.max_sectors = BLK_DEF_MAX_SECTORS;
228 q->limits.max_hw_sectors = max_sectors;
231 EXPORT_SYMBOL(blk_queue_max_sectors);
233 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_sectors)
235 if (BLK_DEF_MAX_SECTORS > max_sectors)
236 q->limits.max_hw_sectors = BLK_DEF_MAX_SECTORS;
237 else
238 q->limits.max_hw_sectors = 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_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
259 * Description:
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)
267 if (!max_segments) {
268 max_segments = 1;
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
282 * Description:
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
286 * to the device.
288 void blk_queue_max_hw_segments(struct request_queue *q,
289 unsigned short max_segments)
291 if (!max_segments) {
292 max_segments = 1;
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
306 * Description:
307 * Enables a low level driver to set an upper limit on the size of a
308 * coalesced segment
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",
315 __func__, max_size);
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
327 * Description:
328 * This should be set to the lowest possible block size that the
329 * storage device can address. The default of 512 covers most
330 * hardware.
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
349 * Description:
350 * This should be set to the lowest possible sector size that the
351 * hardware can operate on without reverting to read-modify-write
352 * operations.
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
371 * Description:
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
375 * naturally aligned.
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
390 * Description:
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
394 * penalty.
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
413 * Description:
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
433 * Description:
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
452 * Description:
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);
480 if (!t->queue_lock)
481 WARN_ON_ONCE(1);
482 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
483 unsigned long 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);
492 * blk_stack_limits - adjust queue_limits for stacked devices
493 * @t: the stacking driver limits (top)
494 * @b: the underlying queue limits (bottom)
495 * @offset: offset to beginning of data within component device
497 * Description:
498 * Merges two queue_limit structs. Returns 0 if alignment didn't
499 * change. Returns -1 if adding the bottom device caused
500 * misalignment.
502 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
503 sector_t offset)
505 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
506 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
507 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
509 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
510 b->seg_boundary_mask);
512 t->max_phys_segments = min_not_zero(t->max_phys_segments,
513 b->max_phys_segments);
515 t->max_hw_segments = min_not_zero(t->max_hw_segments,
516 b->max_hw_segments);
518 t->max_segment_size = min_not_zero(t->max_segment_size,
519 b->max_segment_size);
521 t->logical_block_size = max(t->logical_block_size,
522 b->logical_block_size);
524 t->physical_block_size = max(t->physical_block_size,
525 b->physical_block_size);
527 t->io_min = max(t->io_min, b->io_min);
528 t->no_cluster |= b->no_cluster;
530 /* Bottom device offset aligned? */
531 if (offset &&
532 (offset & (b->physical_block_size - 1)) != b->alignment_offset) {
533 t->misaligned = 1;
534 return -1;
537 /* If top has no alignment offset, inherit from bottom */
538 if (!t->alignment_offset)
539 t->alignment_offset =
540 b->alignment_offset & (b->physical_block_size - 1);
542 /* Top device aligned on logical block boundary? */
543 if (t->alignment_offset & (t->logical_block_size - 1)) {
544 t->misaligned = 1;
545 return -1;
548 /* Find lcm() of optimal I/O size */
549 if (t->io_opt && b->io_opt)
550 t->io_opt = (t->io_opt * b->io_opt) / gcd(t->io_opt, b->io_opt);
551 else if (b->io_opt)
552 t->io_opt = b->io_opt;
554 /* Verify that optimal I/O size is a multiple of io_min */
555 if (t->io_min && t->io_opt % t->io_min)
556 return -1;
558 return 0;
560 EXPORT_SYMBOL(blk_stack_limits);
563 * disk_stack_limits - adjust queue limits for stacked drivers
564 * @disk: MD/DM gendisk (top)
565 * @bdev: the underlying block device (bottom)
566 * @offset: offset to beginning of data within component device
568 * Description:
569 * Merges the limits for two queues. Returns 0 if alignment
570 * didn't change. Returns -1 if adding the bottom device caused
571 * misalignment.
573 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
574 sector_t offset)
576 struct request_queue *t = disk->queue;
577 struct request_queue *b = bdev_get_queue(bdev);
579 offset += get_start_sect(bdev) << 9;
581 if (blk_stack_limits(&t->limits, &b->limits, offset) < 0) {
582 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
584 disk_name(disk, 0, top);
585 bdevname(bdev, bottom);
587 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
588 top, bottom);
591 if (!t->queue_lock)
592 WARN_ON_ONCE(1);
593 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
594 unsigned long flags;
596 spin_lock_irqsave(t->queue_lock, flags);
597 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
598 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
599 spin_unlock_irqrestore(t->queue_lock, flags);
602 EXPORT_SYMBOL(disk_stack_limits);
605 * blk_queue_dma_pad - set pad mask
606 * @q: the request queue for the device
607 * @mask: pad mask
609 * Set dma pad mask.
611 * Appending pad buffer to a request modifies the last entry of a
612 * scatter list such that it includes the pad buffer.
614 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
616 q->dma_pad_mask = mask;
618 EXPORT_SYMBOL(blk_queue_dma_pad);
621 * blk_queue_update_dma_pad - update pad mask
622 * @q: the request queue for the device
623 * @mask: pad mask
625 * Update dma pad mask.
627 * Appending pad buffer to a request modifies the last entry of a
628 * scatter list such that it includes the pad buffer.
630 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
632 if (mask > q->dma_pad_mask)
633 q->dma_pad_mask = mask;
635 EXPORT_SYMBOL(blk_queue_update_dma_pad);
638 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
639 * @q: the request queue for the device
640 * @dma_drain_needed: fn which returns non-zero if drain is necessary
641 * @buf: physically contiguous buffer
642 * @size: size of the buffer in bytes
644 * Some devices have excess DMA problems and can't simply discard (or
645 * zero fill) the unwanted piece of the transfer. They have to have a
646 * real area of memory to transfer it into. The use case for this is
647 * ATAPI devices in DMA mode. If the packet command causes a transfer
648 * bigger than the transfer size some HBAs will lock up if there
649 * aren't DMA elements to contain the excess transfer. What this API
650 * does is adjust the queue so that the buf is always appended
651 * silently to the scatterlist.
653 * Note: This routine adjusts max_hw_segments to make room for
654 * appending the drain buffer. If you call
655 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
656 * calling this routine, you must set the limit to one fewer than your
657 * device can support otherwise there won't be room for the drain
658 * buffer.
660 int blk_queue_dma_drain(struct request_queue *q,
661 dma_drain_needed_fn *dma_drain_needed,
662 void *buf, unsigned int size)
664 if (queue_max_hw_segments(q) < 2 || queue_max_phys_segments(q) < 2)
665 return -EINVAL;
666 /* make room for appending the drain */
667 blk_queue_max_hw_segments(q, queue_max_hw_segments(q) - 1);
668 blk_queue_max_phys_segments(q, queue_max_phys_segments(q) - 1);
669 q->dma_drain_needed = dma_drain_needed;
670 q->dma_drain_buffer = buf;
671 q->dma_drain_size = size;
673 return 0;
675 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
678 * blk_queue_segment_boundary - set boundary rules for segment merging
679 * @q: the request queue for the device
680 * @mask: the memory boundary mask
682 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
684 if (mask < PAGE_CACHE_SIZE - 1) {
685 mask = PAGE_CACHE_SIZE - 1;
686 printk(KERN_INFO "%s: set to minimum %lx\n",
687 __func__, mask);
690 q->limits.seg_boundary_mask = mask;
692 EXPORT_SYMBOL(blk_queue_segment_boundary);
695 * blk_queue_dma_alignment - set dma length and memory alignment
696 * @q: the request queue for the device
697 * @mask: alignment mask
699 * description:
700 * set required memory and length alignment for direct dma transactions.
701 * this is used when building direct io requests for the queue.
704 void blk_queue_dma_alignment(struct request_queue *q, int mask)
706 q->dma_alignment = mask;
708 EXPORT_SYMBOL(blk_queue_dma_alignment);
711 * blk_queue_update_dma_alignment - update dma length and memory alignment
712 * @q: the request queue for the device
713 * @mask: alignment mask
715 * description:
716 * update required memory and length alignment for direct dma transactions.
717 * If the requested alignment is larger than the current alignment, then
718 * the current queue alignment is updated to the new value, otherwise it
719 * is left alone. The design of this is to allow multiple objects
720 * (driver, device, transport etc) to set their respective
721 * alignments without having them interfere.
724 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
726 BUG_ON(mask > PAGE_SIZE);
728 if (mask > q->dma_alignment)
729 q->dma_alignment = mask;
731 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
733 static int __init blk_settings_init(void)
735 blk_max_low_pfn = max_low_pfn - 1;
736 blk_max_pfn = max_pfn - 1;
737 return 0;
739 subsys_initcall(blk_settings_init);