platform-drivers: x86: fix common misspellings
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / block / blk-settings.c
blob112c4f7c7121f6e9602f50f407a89c9082f323a2
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>
11 #include <linux/lcm.h>
13 #include "blk.h"
15 unsigned long blk_max_low_pfn;
16 EXPORT_SYMBOL(blk_max_low_pfn);
18 unsigned long blk_max_pfn;
20 /**
21 * blk_queue_prep_rq - set a prepare_request function for queue
22 * @q: queue
23 * @pfn: prepare_request function
25 * It's possible for a queue to register a prepare_request callback which
26 * is invoked before the request is handed to the request_fn. The goal of
27 * the function is to prepare a request for I/O, it can be used to build a
28 * cdb from the request data for instance.
31 void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
33 q->prep_rq_fn = pfn;
35 EXPORT_SYMBOL(blk_queue_prep_rq);
37 /**
38 * blk_queue_merge_bvec - set a merge_bvec function for queue
39 * @q: queue
40 * @mbfn: merge_bvec_fn
42 * Usually queues have static limitations on the max sectors or segments that
43 * we can put in a request. Stacking drivers may have some settings that
44 * are dynamic, and thus we have to query the queue whether it is ok to
45 * add a new bio_vec to a bio at a given offset or not. If the block device
46 * has such limitations, it needs to register a merge_bvec_fn to control
47 * the size of bio's sent to it. Note that a block device *must* allow a
48 * single page to be added to an empty bio. The block device driver may want
49 * to use the bio_split() function to deal with these bio's. By default
50 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
51 * honored.
53 void blk_queue_merge_bvec(struct request_queue *q, merge_bvec_fn *mbfn)
55 q->merge_bvec_fn = mbfn;
57 EXPORT_SYMBOL(blk_queue_merge_bvec);
59 void blk_queue_softirq_done(struct request_queue *q, softirq_done_fn *fn)
61 q->softirq_done_fn = fn;
63 EXPORT_SYMBOL(blk_queue_softirq_done);
65 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
67 q->rq_timeout = timeout;
69 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
71 void blk_queue_rq_timed_out(struct request_queue *q, rq_timed_out_fn *fn)
73 q->rq_timed_out_fn = fn;
75 EXPORT_SYMBOL_GPL(blk_queue_rq_timed_out);
77 void blk_queue_lld_busy(struct request_queue *q, lld_busy_fn *fn)
79 q->lld_busy_fn = fn;
81 EXPORT_SYMBOL_GPL(blk_queue_lld_busy);
83 /**
84 * blk_set_default_limits - reset limits to default values
85 * @lim: the queue_limits structure to reset
87 * Description:
88 * Returns a queue_limit struct to its default state. Can be used by
89 * stacking drivers like DM that stage table swaps and reuse an
90 * existing device queue.
92 void blk_set_default_limits(struct queue_limits *lim)
94 lim->max_phys_segments = MAX_PHYS_SEGMENTS;
95 lim->max_hw_segments = MAX_HW_SEGMENTS;
96 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
97 lim->max_segment_size = MAX_SEGMENT_SIZE;
98 lim->max_sectors = BLK_DEF_MAX_SECTORS;
99 lim->max_hw_sectors = INT_MAX;
100 lim->max_discard_sectors = SAFE_MAX_SECTORS;
101 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
102 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
103 lim->alignment_offset = 0;
104 lim->io_opt = 0;
105 lim->misaligned = 0;
106 lim->cluster = 1;
108 EXPORT_SYMBOL(blk_set_default_limits);
111 * blk_queue_make_request - define an alternate make_request function for a device
112 * @q: the request queue for the device to be affected
113 * @mfn: the alternate make_request function
115 * Description:
116 * The normal way for &struct bios to be passed to a device
117 * driver is for them to be collected into requests on a request
118 * queue, and then to allow the device driver to select requests
119 * off that queue when it is ready. This works well for many block
120 * devices. However some block devices (typically virtual devices
121 * such as md or lvm) do not benefit from the processing on the
122 * request queue, and are served best by having the requests passed
123 * directly to them. This can be achieved by providing a function
124 * to blk_queue_make_request().
126 * Caveat:
127 * The driver that does this *must* be able to deal appropriately
128 * with buffers in "highmemory". This can be accomplished by either calling
129 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
130 * blk_queue_bounce() to create a buffer in normal memory.
132 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
135 * set defaults
137 q->nr_requests = BLKDEV_MAX_RQ;
139 q->make_request_fn = mfn;
140 blk_queue_dma_alignment(q, 511);
141 blk_queue_congestion_threshold(q);
142 q->nr_batching = BLK_BATCH_REQ;
144 q->unplug_thresh = 4; /* hmm */
145 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
146 if (q->unplug_delay == 0)
147 q->unplug_delay = 1;
149 q->unplug_timer.function = blk_unplug_timeout;
150 q->unplug_timer.data = (unsigned long)q;
152 blk_set_default_limits(&q->limits);
153 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
156 * If the caller didn't supply a lock, fall back to our embedded
157 * per-queue locks
159 if (!q->queue_lock)
160 q->queue_lock = &q->__queue_lock;
163 * by default assume old behaviour and bounce for any highmem page
165 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
167 EXPORT_SYMBOL(blk_queue_make_request);
170 * blk_queue_bounce_limit - set bounce buffer limit for queue
171 * @q: the request queue for the device
172 * @dma_mask: the maximum address the device can handle
174 * Description:
175 * Different hardware can have different requirements as to what pages
176 * it can do I/O directly to. A low level driver can call
177 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
178 * buffers for doing I/O to pages residing above @dma_mask.
180 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
182 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
183 int dma = 0;
185 q->bounce_gfp = GFP_NOIO;
186 #if BITS_PER_LONG == 64
188 * Assume anything <= 4GB can be handled by IOMMU. Actually
189 * some IOMMUs can handle everything, but I don't know of a
190 * way to test this here.
192 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
193 dma = 1;
194 q->limits.bounce_pfn = max_low_pfn;
195 #else
196 if (b_pfn < blk_max_low_pfn)
197 dma = 1;
198 q->limits.bounce_pfn = b_pfn;
199 #endif
200 if (dma) {
201 init_emergency_isa_pool();
202 q->bounce_gfp = GFP_NOIO | GFP_DMA;
203 q->limits.bounce_pfn = b_pfn;
206 EXPORT_SYMBOL(blk_queue_bounce_limit);
209 * blk_queue_max_sectors - set max sectors for a request for this queue
210 * @q: the request queue for the device
211 * @max_sectors: max sectors in the usual 512b unit
213 * Description:
214 * Enables a low level driver to set an upper limit on the size of
215 * received requests.
217 void blk_queue_max_sectors(struct request_queue *q, unsigned int max_sectors)
219 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
220 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
221 printk(KERN_INFO "%s: set to minimum %d\n",
222 __func__, max_sectors);
225 if (BLK_DEF_MAX_SECTORS > max_sectors)
226 q->limits.max_hw_sectors = q->limits.max_sectors = max_sectors;
227 else {
228 q->limits.max_sectors = BLK_DEF_MAX_SECTORS;
229 q->limits.max_hw_sectors = max_sectors;
232 EXPORT_SYMBOL(blk_queue_max_sectors);
234 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_sectors)
236 if (BLK_DEF_MAX_SECTORS > max_sectors)
237 q->limits.max_hw_sectors = BLK_DEF_MAX_SECTORS;
238 else
239 q->limits.max_hw_sectors = 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_phys_segments - set max phys segments for a request for this queue
257 * @q: the request queue for the device
258 * @max_segments: max number of segments
260 * Description:
261 * Enables a low level driver to set an upper limit on the number of
262 * physical data segments in a request. This would be the largest sized
263 * scatter list the driver could handle.
265 void blk_queue_max_phys_segments(struct request_queue *q,
266 unsigned short max_segments)
268 if (!max_segments) {
269 max_segments = 1;
270 printk(KERN_INFO "%s: set to minimum %d\n",
271 __func__, max_segments);
274 q->limits.max_phys_segments = max_segments;
276 EXPORT_SYMBOL(blk_queue_max_phys_segments);
279 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
280 * @q: the request queue for the device
281 * @max_segments: max number of segments
283 * Description:
284 * Enables a low level driver to set an upper limit on the number of
285 * hw data segments in a request. This would be the largest number of
286 * address/length pairs the host adapter can actually give at once
287 * to the device.
289 void blk_queue_max_hw_segments(struct request_queue *q,
290 unsigned short max_segments)
292 if (!max_segments) {
293 max_segments = 1;
294 printk(KERN_INFO "%s: set to minimum %d\n",
295 __func__, max_segments);
298 q->limits.max_hw_segments = max_segments;
300 EXPORT_SYMBOL(blk_queue_max_hw_segments);
303 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
304 * @q: the request queue for the device
305 * @max_size: max size of segment in bytes
307 * Description:
308 * Enables a low level driver to set an upper limit on the size of a
309 * coalesced segment
311 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
313 if (max_size < PAGE_CACHE_SIZE) {
314 max_size = PAGE_CACHE_SIZE;
315 printk(KERN_INFO "%s: set to minimum %d\n",
316 __func__, max_size);
319 q->limits.max_segment_size = max_size;
321 EXPORT_SYMBOL(blk_queue_max_segment_size);
324 * blk_queue_logical_block_size - set logical block size for the queue
325 * @q: the request queue for the device
326 * @size: the logical block size, in bytes
328 * Description:
329 * This should be set to the lowest possible block size that the
330 * storage device can address. The default of 512 covers most
331 * hardware.
333 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
335 q->limits.logical_block_size = size;
337 if (q->limits.physical_block_size < size)
338 q->limits.physical_block_size = size;
340 if (q->limits.io_min < q->limits.physical_block_size)
341 q->limits.io_min = q->limits.physical_block_size;
343 EXPORT_SYMBOL(blk_queue_logical_block_size);
346 * blk_queue_physical_block_size - set physical block size for the queue
347 * @q: the request queue for the device
348 * @size: the physical block size, in bytes
350 * Description:
351 * This should be set to the lowest possible sector size that the
352 * hardware can operate on without reverting to read-modify-write
353 * operations.
355 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
357 q->limits.physical_block_size = size;
359 if (q->limits.physical_block_size < q->limits.logical_block_size)
360 q->limits.physical_block_size = q->limits.logical_block_size;
362 if (q->limits.io_min < q->limits.physical_block_size)
363 q->limits.io_min = q->limits.physical_block_size;
365 EXPORT_SYMBOL(blk_queue_physical_block_size);
368 * blk_queue_alignment_offset - set physical block alignment offset
369 * @q: the request queue for the device
370 * @offset: alignment offset in bytes
372 * Description:
373 * Some devices are naturally misaligned to compensate for things like
374 * the legacy DOS partition table 63-sector offset. Low-level drivers
375 * should call this function for devices whose first sector is not
376 * naturally aligned.
378 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
380 q->limits.alignment_offset =
381 offset & (q->limits.physical_block_size - 1);
382 q->limits.misaligned = 0;
384 EXPORT_SYMBOL(blk_queue_alignment_offset);
387 * blk_limits_io_min - set minimum request size for a device
388 * @limits: the queue limits
389 * @min: smallest I/O size in bytes
391 * Description:
392 * Some devices have an internal block size bigger than the reported
393 * hardware sector size. This function can be used to signal the
394 * smallest I/O the device can perform without incurring a performance
395 * penalty.
397 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
399 limits->io_min = min;
401 if (limits->io_min < limits->logical_block_size)
402 limits->io_min = limits->logical_block_size;
404 if (limits->io_min < limits->physical_block_size)
405 limits->io_min = limits->physical_block_size;
407 EXPORT_SYMBOL(blk_limits_io_min);
410 * blk_queue_io_min - set minimum request size for the queue
411 * @q: the request queue for the device
412 * @min: smallest I/O size in bytes
414 * Description:
415 * Storage devices may report a granularity or preferred minimum I/O
416 * size which is the smallest request the device can perform without
417 * incurring a performance penalty. For disk drives this is often the
418 * physical block size. For RAID arrays it is often the stripe chunk
419 * size. A properly aligned multiple of minimum_io_size is the
420 * preferred request size for workloads where a high number of I/O
421 * operations is desired.
423 void blk_queue_io_min(struct request_queue *q, unsigned int min)
425 blk_limits_io_min(&q->limits, min);
427 EXPORT_SYMBOL(blk_queue_io_min);
430 * blk_limits_io_opt - set optimal request size for a device
431 * @limits: the queue limits
432 * @opt: smallest I/O size in bytes
434 * Description:
435 * Storage devices may report an optimal I/O size, which is the
436 * device's preferred unit for sustained I/O. This is rarely reported
437 * for disk drives. For RAID arrays it is usually the stripe width or
438 * the internal track size. A properly aligned multiple of
439 * optimal_io_size is the preferred request size for workloads where
440 * sustained throughput is desired.
442 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
444 limits->io_opt = opt;
446 EXPORT_SYMBOL(blk_limits_io_opt);
449 * blk_queue_io_opt - set optimal request size for the queue
450 * @q: the request queue for the device
451 * @opt: optimal request size in bytes
453 * Description:
454 * Storage devices may report an optimal I/O size, which is the
455 * device's preferred unit for sustained I/O. This is rarely reported
456 * for disk drives. For RAID arrays it is usually the stripe width or
457 * the internal track size. A properly aligned multiple of
458 * optimal_io_size is the preferred request size for workloads where
459 * sustained throughput is desired.
461 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
463 blk_limits_io_opt(&q->limits, opt);
465 EXPORT_SYMBOL(blk_queue_io_opt);
468 * Returns the minimum that is _not_ zero, unless both are zero.
470 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
473 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
474 * @t: the stacking driver (top)
475 * @b: the underlying device (bottom)
477 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
479 blk_stack_limits(&t->limits, &b->limits, 0);
481 EXPORT_SYMBOL(blk_queue_stack_limits);
484 * blk_stack_limits - adjust queue_limits for stacked devices
485 * @t: the stacking driver limits (top device)
486 * @b: the underlying queue limits (bottom, component device)
487 * @offset: offset to beginning of data within component device
489 * Description:
490 * This function is used by stacking drivers like MD and DM to ensure
491 * that all component devices have compatible block sizes and
492 * alignments. The stacking driver must provide a queue_limits
493 * struct (top) and then iteratively call the stacking function for
494 * all component (bottom) devices. The stacking function will
495 * attempt to combine the values and ensure proper alignment.
497 * Returns 0 if the top and bottom queue_limits are compatible. The
498 * top device's block sizes and alignment offsets may be adjusted to
499 * ensure alignment with the bottom device. If no compatible sizes
500 * and alignments exist, -1 is returned and the resulting top
501 * queue_limits will have the misaligned flag set to indicate that
502 * the alignment_offset is undefined.
504 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
505 sector_t offset)
507 sector_t alignment;
508 unsigned int top, bottom, ret = 0;
510 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
511 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
512 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
514 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
515 b->seg_boundary_mask);
517 t->max_phys_segments = min_not_zero(t->max_phys_segments,
518 b->max_phys_segments);
520 t->max_hw_segments = min_not_zero(t->max_hw_segments,
521 b->max_hw_segments);
523 t->max_segment_size = min_not_zero(t->max_segment_size,
524 b->max_segment_size);
526 t->misaligned |= b->misaligned;
528 alignment = queue_limit_alignment_offset(b, offset);
530 /* Bottom device has different alignment. Check that it is
531 * compatible with the current top alignment.
533 if (t->alignment_offset != alignment) {
535 top = max(t->physical_block_size, t->io_min)
536 + t->alignment_offset;
537 bottom = max(b->physical_block_size, b->io_min) + alignment;
539 /* Verify that top and bottom intervals line up */
540 if (max(top, bottom) & (min(top, bottom) - 1)) {
541 t->misaligned = 1;
542 ret = -1;
546 t->logical_block_size = max(t->logical_block_size,
547 b->logical_block_size);
549 t->physical_block_size = max(t->physical_block_size,
550 b->physical_block_size);
552 t->io_min = max(t->io_min, b->io_min);
553 t->io_opt = lcm(t->io_opt, b->io_opt);
555 t->cluster &= b->cluster;
557 /* Physical block size a multiple of the logical block size? */
558 if (t->physical_block_size & (t->logical_block_size - 1)) {
559 t->physical_block_size = t->logical_block_size;
560 t->misaligned = 1;
561 ret = -1;
564 /* Minimum I/O a multiple of the physical block size? */
565 if (t->io_min & (t->physical_block_size - 1)) {
566 t->io_min = t->physical_block_size;
567 t->misaligned = 1;
568 ret = -1;
571 /* Optimal I/O a multiple of the physical block size? */
572 if (t->io_opt & (t->physical_block_size - 1)) {
573 t->io_opt = 0;
574 t->misaligned = 1;
575 ret = -1;
578 /* Find lowest common alignment_offset */
579 t->alignment_offset = lcm(t->alignment_offset, alignment)
580 & (max(t->physical_block_size, t->io_min) - 1);
582 /* Verify that new alignment_offset is on a logical block boundary */
583 if (t->alignment_offset & (t->logical_block_size - 1)) {
584 t->misaligned = 1;
585 ret = -1;
588 /* Discard */
589 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
590 b->max_discard_sectors);
592 return ret;
594 EXPORT_SYMBOL(blk_stack_limits);
597 * bdev_stack_limits - adjust queue limits for stacked drivers
598 * @t: the stacking driver limits (top device)
599 * @bdev: the component block_device (bottom)
600 * @start: first data sector within component device
602 * Description:
603 * Merges queue limits for a top device and a block_device. Returns
604 * 0 if alignment didn't change. Returns -1 if adding the bottom
605 * device caused misalignment.
607 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
608 sector_t start)
610 struct request_queue *bq = bdev_get_queue(bdev);
612 start += get_start_sect(bdev);
614 return blk_stack_limits(t, &bq->limits, start << 9);
616 EXPORT_SYMBOL(bdev_stack_limits);
619 * disk_stack_limits - adjust queue limits for stacked drivers
620 * @disk: MD/DM gendisk (top)
621 * @bdev: the underlying block device (bottom)
622 * @offset: offset to beginning of data within component device
624 * Description:
625 * Merges the limits for two queues. Returns 0 if alignment
626 * didn't change. Returns -1 if adding the bottom device caused
627 * misalignment.
629 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
630 sector_t offset)
632 struct request_queue *t = disk->queue;
633 struct request_queue *b = bdev_get_queue(bdev);
635 offset += get_start_sect(bdev) << 9;
637 if (blk_stack_limits(&t->limits, &b->limits, offset) < 0) {
638 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
640 disk_name(disk, 0, top);
641 bdevname(bdev, bottom);
643 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
644 top, bottom);
647 EXPORT_SYMBOL(disk_stack_limits);
650 * blk_queue_dma_pad - set pad mask
651 * @q: the request queue for the device
652 * @mask: pad mask
654 * Set 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_dma_pad(struct request_queue *q, unsigned int mask)
661 q->dma_pad_mask = mask;
663 EXPORT_SYMBOL(blk_queue_dma_pad);
666 * blk_queue_update_dma_pad - update pad mask
667 * @q: the request queue for the device
668 * @mask: pad mask
670 * Update dma pad mask.
672 * Appending pad buffer to a request modifies the last entry of a
673 * scatter list such that it includes the pad buffer.
675 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
677 if (mask > q->dma_pad_mask)
678 q->dma_pad_mask = mask;
680 EXPORT_SYMBOL(blk_queue_update_dma_pad);
683 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
684 * @q: the request queue for the device
685 * @dma_drain_needed: fn which returns non-zero if drain is necessary
686 * @buf: physically contiguous buffer
687 * @size: size of the buffer in bytes
689 * Some devices have excess DMA problems and can't simply discard (or
690 * zero fill) the unwanted piece of the transfer. They have to have a
691 * real area of memory to transfer it into. The use case for this is
692 * ATAPI devices in DMA mode. If the packet command causes a transfer
693 * bigger than the transfer size some HBAs will lock up if there
694 * aren't DMA elements to contain the excess transfer. What this API
695 * does is adjust the queue so that the buf is always appended
696 * silently to the scatterlist.
698 * Note: This routine adjusts max_hw_segments to make room for
699 * appending the drain buffer. If you call
700 * blk_queue_max_hw_segments() or blk_queue_max_phys_segments() after
701 * calling this routine, you must set the limit to one fewer than your
702 * device can support otherwise there won't be room for the drain
703 * buffer.
705 int blk_queue_dma_drain(struct request_queue *q,
706 dma_drain_needed_fn *dma_drain_needed,
707 void *buf, unsigned int size)
709 if (queue_max_hw_segments(q) < 2 || queue_max_phys_segments(q) < 2)
710 return -EINVAL;
711 /* make room for appending the drain */
712 blk_queue_max_hw_segments(q, queue_max_hw_segments(q) - 1);
713 blk_queue_max_phys_segments(q, queue_max_phys_segments(q) - 1);
714 q->dma_drain_needed = dma_drain_needed;
715 q->dma_drain_buffer = buf;
716 q->dma_drain_size = size;
718 return 0;
720 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
723 * blk_queue_segment_boundary - set boundary rules for segment merging
724 * @q: the request queue for the device
725 * @mask: the memory boundary mask
727 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
729 if (mask < PAGE_CACHE_SIZE - 1) {
730 mask = PAGE_CACHE_SIZE - 1;
731 printk(KERN_INFO "%s: set to minimum %lx\n",
732 __func__, mask);
735 q->limits.seg_boundary_mask = mask;
737 EXPORT_SYMBOL(blk_queue_segment_boundary);
740 * blk_queue_dma_alignment - set dma length and memory alignment
741 * @q: the request queue for the device
742 * @mask: alignment mask
744 * description:
745 * set required memory and length alignment for direct dma transactions.
746 * this is used when building direct io requests for the queue.
749 void blk_queue_dma_alignment(struct request_queue *q, int mask)
751 q->dma_alignment = mask;
753 EXPORT_SYMBOL(blk_queue_dma_alignment);
756 * blk_queue_update_dma_alignment - update dma length and memory alignment
757 * @q: the request queue for the device
758 * @mask: alignment mask
760 * description:
761 * update required memory and length alignment for direct dma transactions.
762 * If the requested alignment is larger than the current alignment, then
763 * the current queue alignment is updated to the new value, otherwise it
764 * is left alone. The design of this is to allow multiple objects
765 * (driver, device, transport etc) to set their respective
766 * alignments without having them interfere.
769 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
771 BUG_ON(mask > PAGE_SIZE);
773 if (mask > q->dma_alignment)
774 q->dma_alignment = mask;
776 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
778 static int __init blk_settings_init(void)
780 blk_max_low_pfn = max_low_pfn - 1;
781 blk_max_pfn = max_pfn - 1;
782 return 0;
784 subsys_initcall(blk_settings_init);