lib/string.c: simplify stricmp()
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / block / blk-settings.c
blob31e7a9375c1333cc35ab40d565c5c1ed4e8703e7
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/jiffies.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_segments = BLK_MAX_SEGMENTS;
95 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
96 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
97 lim->max_sectors = BLK_DEF_MAX_SECTORS;
98 lim->max_hw_sectors = INT_MAX;
99 lim->max_discard_sectors = 0;
100 lim->discard_granularity = 0;
101 lim->discard_alignment = 0;
102 lim->discard_misaligned = 0;
103 lim->discard_zeroes_data = -1;
104 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
105 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
106 lim->alignment_offset = 0;
107 lim->io_opt = 0;
108 lim->misaligned = 0;
109 lim->no_cluster = 0;
111 EXPORT_SYMBOL(blk_set_default_limits);
114 * blk_queue_make_request - define an alternate make_request function for a device
115 * @q: the request queue for the device to be affected
116 * @mfn: the alternate make_request function
118 * Description:
119 * The normal way for &struct bios to be passed to a device
120 * driver is for them to be collected into requests on a request
121 * queue, and then to allow the device driver to select requests
122 * off that queue when it is ready. This works well for many block
123 * devices. However some block devices (typically virtual devices
124 * such as md or lvm) do not benefit from the processing on the
125 * request queue, and are served best by having the requests passed
126 * directly to them. This can be achieved by providing a function
127 * to blk_queue_make_request().
129 * Caveat:
130 * The driver that does this *must* be able to deal appropriately
131 * with buffers in "highmemory". This can be accomplished by either calling
132 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
133 * blk_queue_bounce() to create a buffer in normal memory.
135 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
138 * set defaults
140 q->nr_requests = BLKDEV_MAX_RQ;
142 q->make_request_fn = mfn;
143 blk_queue_dma_alignment(q, 511);
144 blk_queue_congestion_threshold(q);
145 q->nr_batching = BLK_BATCH_REQ;
147 q->unplug_thresh = 4; /* hmm */
148 q->unplug_delay = msecs_to_jiffies(3); /* 3 milliseconds */
149 if (q->unplug_delay == 0)
150 q->unplug_delay = 1;
152 q->unplug_timer.function = blk_unplug_timeout;
153 q->unplug_timer.data = (unsigned long)q;
155 blk_set_default_limits(&q->limits);
156 blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
159 * If the caller didn't supply a lock, fall back to our embedded
160 * per-queue locks
162 if (!q->queue_lock)
163 q->queue_lock = &q->__queue_lock;
166 * by default assume old behaviour and bounce for any highmem page
168 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
170 EXPORT_SYMBOL(blk_queue_make_request);
173 * blk_queue_bounce_limit - set bounce buffer limit for queue
174 * @q: the request queue for the device
175 * @dma_mask: the maximum address the device can handle
177 * Description:
178 * Different hardware can have different requirements as to what pages
179 * it can do I/O directly to. A low level driver can call
180 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
181 * buffers for doing I/O to pages residing above @dma_mask.
183 void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
185 unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
186 int dma = 0;
188 q->bounce_gfp = GFP_NOIO;
189 #if BITS_PER_LONG == 64
191 * Assume anything <= 4GB can be handled by IOMMU. Actually
192 * some IOMMUs can handle everything, but I don't know of a
193 * way to test this here.
195 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
196 dma = 1;
197 q->limits.bounce_pfn = max_low_pfn;
198 #else
199 if (b_pfn < blk_max_low_pfn)
200 dma = 1;
201 q->limits.bounce_pfn = b_pfn;
202 #endif
203 if (dma) {
204 init_emergency_isa_pool();
205 q->bounce_gfp = GFP_NOIO | GFP_DMA;
206 q->limits.bounce_pfn = b_pfn;
209 EXPORT_SYMBOL(blk_queue_bounce_limit);
212 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
213 * @q: the request queue for the device
214 * @max_hw_sectors: max hardware sectors in the usual 512b unit
216 * Description:
217 * Enables a low level driver to set a hard upper limit,
218 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
219 * the device driver based upon the combined capabilities of I/O
220 * controller and storage device.
222 * max_sectors is a soft limit imposed by the block layer for
223 * filesystem type requests. This value can be overridden on a
224 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
225 * The soft limit can not exceed max_hw_sectors.
227 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
229 if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
230 max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
231 printk(KERN_INFO "%s: set to minimum %d\n",
232 __func__, max_hw_sectors);
235 q->limits.max_hw_sectors = max_hw_sectors;
236 q->limits.max_sectors = min_t(unsigned int, max_hw_sectors,
237 BLK_DEF_MAX_SECTORS);
239 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
242 * blk_queue_max_discard_sectors - set max sectors for a single discard
243 * @q: the request queue for the device
244 * @max_discard_sectors: maximum number of sectors to discard
246 void blk_queue_max_discard_sectors(struct request_queue *q,
247 unsigned int max_discard_sectors)
249 q->limits.max_discard_sectors = max_discard_sectors;
251 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
254 * blk_queue_max_segments - set max hw segments for a request for this queue
255 * @q: the request queue for the device
256 * @max_segments: max number of segments
258 * Description:
259 * Enables a low level driver to set an upper limit on the number of
260 * hw data segments in a request.
262 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
264 if (!max_segments) {
265 max_segments = 1;
266 printk(KERN_INFO "%s: set to minimum %d\n",
267 __func__, max_segments);
270 q->limits.max_segments = max_segments;
272 EXPORT_SYMBOL(blk_queue_max_segments);
275 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
276 * @q: the request queue for the device
277 * @max_size: max size of segment in bytes
279 * Description:
280 * Enables a low level driver to set an upper limit on the size of a
281 * coalesced segment
283 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
285 if (max_size < PAGE_CACHE_SIZE) {
286 max_size = PAGE_CACHE_SIZE;
287 printk(KERN_INFO "%s: set to minimum %d\n",
288 __func__, max_size);
291 q->limits.max_segment_size = max_size;
293 EXPORT_SYMBOL(blk_queue_max_segment_size);
296 * blk_queue_logical_block_size - set logical block size for the queue
297 * @q: the request queue for the device
298 * @size: the logical block size, in bytes
300 * Description:
301 * This should be set to the lowest possible block size that the
302 * storage device can address. The default of 512 covers most
303 * hardware.
305 void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
307 q->limits.logical_block_size = size;
309 if (q->limits.physical_block_size < size)
310 q->limits.physical_block_size = size;
312 if (q->limits.io_min < q->limits.physical_block_size)
313 q->limits.io_min = q->limits.physical_block_size;
315 EXPORT_SYMBOL(blk_queue_logical_block_size);
318 * blk_queue_physical_block_size - set physical block size for the queue
319 * @q: the request queue for the device
320 * @size: the physical block size, in bytes
322 * Description:
323 * This should be set to the lowest possible sector size that the
324 * hardware can operate on without reverting to read-modify-write
325 * operations.
327 void blk_queue_physical_block_size(struct request_queue *q, unsigned short size)
329 q->limits.physical_block_size = size;
331 if (q->limits.physical_block_size < q->limits.logical_block_size)
332 q->limits.physical_block_size = q->limits.logical_block_size;
334 if (q->limits.io_min < q->limits.physical_block_size)
335 q->limits.io_min = q->limits.physical_block_size;
337 EXPORT_SYMBOL(blk_queue_physical_block_size);
340 * blk_queue_alignment_offset - set physical block alignment offset
341 * @q: the request queue for the device
342 * @offset: alignment offset in bytes
344 * Description:
345 * Some devices are naturally misaligned to compensate for things like
346 * the legacy DOS partition table 63-sector offset. Low-level drivers
347 * should call this function for devices whose first sector is not
348 * naturally aligned.
350 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
352 q->limits.alignment_offset =
353 offset & (q->limits.physical_block_size - 1);
354 q->limits.misaligned = 0;
356 EXPORT_SYMBOL(blk_queue_alignment_offset);
359 * blk_limits_io_min - set minimum request size for a device
360 * @limits: the queue limits
361 * @min: smallest I/O size in bytes
363 * Description:
364 * Some devices have an internal block size bigger than the reported
365 * hardware sector size. This function can be used to signal the
366 * smallest I/O the device can perform without incurring a performance
367 * penalty.
369 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
371 limits->io_min = min;
373 if (limits->io_min < limits->logical_block_size)
374 limits->io_min = limits->logical_block_size;
376 if (limits->io_min < limits->physical_block_size)
377 limits->io_min = limits->physical_block_size;
379 EXPORT_SYMBOL(blk_limits_io_min);
382 * blk_queue_io_min - set minimum request size for the queue
383 * @q: the request queue for the device
384 * @min: smallest I/O size in bytes
386 * Description:
387 * Storage devices may report a granularity or preferred minimum I/O
388 * size which is the smallest request the device can perform without
389 * incurring a performance penalty. For disk drives this is often the
390 * physical block size. For RAID arrays it is often the stripe chunk
391 * size. A properly aligned multiple of minimum_io_size is the
392 * preferred request size for workloads where a high number of I/O
393 * operations is desired.
395 void blk_queue_io_min(struct request_queue *q, unsigned int min)
397 blk_limits_io_min(&q->limits, min);
399 EXPORT_SYMBOL(blk_queue_io_min);
402 * blk_limits_io_opt - set optimal request size for a device
403 * @limits: the queue limits
404 * @opt: smallest I/O size in bytes
406 * Description:
407 * Storage devices may report an optimal I/O size, which is the
408 * device's preferred unit for sustained I/O. This is rarely reported
409 * for disk drives. For RAID arrays it is usually the stripe width or
410 * the internal track size. A properly aligned multiple of
411 * optimal_io_size is the preferred request size for workloads where
412 * sustained throughput is desired.
414 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
416 limits->io_opt = opt;
418 EXPORT_SYMBOL(blk_limits_io_opt);
421 * blk_queue_io_opt - set optimal request size for the queue
422 * @q: the request queue for the device
423 * @opt: optimal request size in bytes
425 * Description:
426 * Storage devices may report an optimal I/O size, which is the
427 * device's preferred unit for sustained I/O. This is rarely reported
428 * for disk drives. For RAID arrays it is usually the stripe width or
429 * the internal track size. A properly aligned multiple of
430 * optimal_io_size is the preferred request size for workloads where
431 * sustained throughput is desired.
433 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
435 blk_limits_io_opt(&q->limits, opt);
437 EXPORT_SYMBOL(blk_queue_io_opt);
440 * Returns the minimum that is _not_ zero, unless both are zero.
442 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
445 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
446 * @t: the stacking driver (top)
447 * @b: the underlying device (bottom)
449 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
451 blk_stack_limits(&t->limits, &b->limits, 0);
453 if (!t->queue_lock)
454 WARN_ON_ONCE(1);
455 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
456 unsigned long flags;
457 spin_lock_irqsave(t->queue_lock, flags);
458 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
459 spin_unlock_irqrestore(t->queue_lock, flags);
462 EXPORT_SYMBOL(blk_queue_stack_limits);
464 static unsigned int lcm(unsigned int a, unsigned int b)
466 if (a && b)
467 return (a * b) / gcd(a, b);
468 else if (b)
469 return b;
471 return a;
475 * blk_stack_limits - adjust queue_limits for stacked devices
476 * @t: the stacking driver limits (top device)
477 * @b: the underlying queue limits (bottom, component device)
478 * @start: first data sector within component device
480 * Description:
481 * This function is used by stacking drivers like MD and DM to ensure
482 * that all component devices have compatible block sizes and
483 * alignments. The stacking driver must provide a queue_limits
484 * struct (top) and then iteratively call the stacking function for
485 * all component (bottom) devices. The stacking function will
486 * attempt to combine the values and ensure proper alignment.
488 * Returns 0 if the top and bottom queue_limits are compatible. The
489 * top device's block sizes and alignment offsets may be adjusted to
490 * ensure alignment with the bottom device. If no compatible sizes
491 * and alignments exist, -1 is returned and the resulting top
492 * queue_limits will have the misaligned flag set to indicate that
493 * the alignment_offset is undefined.
495 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
496 sector_t start)
498 unsigned int top, bottom, alignment, ret = 0;
500 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
501 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
502 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
504 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
505 b->seg_boundary_mask);
507 t->max_segments = min_not_zero(t->max_segments, b->max_segments);
509 t->max_segment_size = min_not_zero(t->max_segment_size,
510 b->max_segment_size);
512 t->misaligned |= b->misaligned;
514 alignment = queue_limit_alignment_offset(b, start);
516 /* Bottom device has different alignment. Check that it is
517 * compatible with the current top alignment.
519 if (t->alignment_offset != alignment) {
521 top = max(t->physical_block_size, t->io_min)
522 + t->alignment_offset;
523 bottom = max(b->physical_block_size, b->io_min) + alignment;
525 /* Verify that top and bottom intervals line up */
526 if (max(top, bottom) & (min(top, bottom) - 1)) {
527 t->misaligned = 1;
528 ret = -1;
532 t->logical_block_size = max(t->logical_block_size,
533 b->logical_block_size);
535 t->physical_block_size = max(t->physical_block_size,
536 b->physical_block_size);
538 t->io_min = max(t->io_min, b->io_min);
539 t->io_opt = lcm(t->io_opt, b->io_opt);
541 t->no_cluster |= b->no_cluster;
542 t->discard_zeroes_data &= b->discard_zeroes_data;
544 /* Physical block size a multiple of the logical block size? */
545 if (t->physical_block_size & (t->logical_block_size - 1)) {
546 t->physical_block_size = t->logical_block_size;
547 t->misaligned = 1;
548 ret = -1;
551 /* Minimum I/O a multiple of the physical block size? */
552 if (t->io_min & (t->physical_block_size - 1)) {
553 t->io_min = t->physical_block_size;
554 t->misaligned = 1;
555 ret = -1;
558 /* Optimal I/O a multiple of the physical block size? */
559 if (t->io_opt & (t->physical_block_size - 1)) {
560 t->io_opt = 0;
561 t->misaligned = 1;
562 ret = -1;
565 /* Find lowest common alignment_offset */
566 t->alignment_offset = lcm(t->alignment_offset, alignment)
567 & (max(t->physical_block_size, t->io_min) - 1);
569 /* Verify that new alignment_offset is on a logical block boundary */
570 if (t->alignment_offset & (t->logical_block_size - 1)) {
571 t->misaligned = 1;
572 ret = -1;
575 /* Discard alignment and granularity */
576 if (b->discard_granularity) {
577 alignment = queue_limit_discard_alignment(b, start);
579 if (t->discard_granularity != 0 &&
580 t->discard_alignment != alignment) {
581 top = t->discard_granularity + t->discard_alignment;
582 bottom = b->discard_granularity + alignment;
584 /* Verify that top and bottom intervals line up */
585 if (max(top, bottom) & (min(top, bottom) - 1))
586 t->discard_misaligned = 1;
589 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
590 b->max_discard_sectors);
591 t->discard_granularity = max(t->discard_granularity,
592 b->discard_granularity);
593 t->discard_alignment = lcm(t->discard_alignment, alignment) &
594 (t->discard_granularity - 1);
597 return ret;
599 EXPORT_SYMBOL(blk_stack_limits);
602 * bdev_stack_limits - adjust queue limits for stacked drivers
603 * @t: the stacking driver limits (top device)
604 * @bdev: the component block_device (bottom)
605 * @start: first data sector within component device
607 * Description:
608 * Merges queue limits for a top device and a block_device. Returns
609 * 0 if alignment didn't change. Returns -1 if adding the bottom
610 * device caused misalignment.
612 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
613 sector_t start)
615 struct request_queue *bq = bdev_get_queue(bdev);
617 start += get_start_sect(bdev);
619 return blk_stack_limits(t, &bq->limits, start);
621 EXPORT_SYMBOL(bdev_stack_limits);
624 * disk_stack_limits - adjust queue limits for stacked drivers
625 * @disk: MD/DM gendisk (top)
626 * @bdev: the underlying block device (bottom)
627 * @offset: offset to beginning of data within component device
629 * Description:
630 * Merges the limits for a top level gendisk and a bottom level
631 * block_device.
633 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
634 sector_t offset)
636 struct request_queue *t = disk->queue;
637 struct request_queue *b = bdev_get_queue(bdev);
639 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
640 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
642 disk_name(disk, 0, top);
643 bdevname(bdev, bottom);
645 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
646 top, bottom);
649 if (!t->queue_lock)
650 WARN_ON_ONCE(1);
651 else if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags)) {
652 unsigned long flags;
654 spin_lock_irqsave(t->queue_lock, flags);
655 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
656 queue_flag_clear(QUEUE_FLAG_CLUSTER, t);
657 spin_unlock_irqrestore(t->queue_lock, flags);
660 EXPORT_SYMBOL(disk_stack_limits);
663 * blk_queue_dma_pad - set pad mask
664 * @q: the request queue for the device
665 * @mask: pad mask
667 * Set dma pad mask.
669 * Appending pad buffer to a request modifies the last entry of a
670 * scatter list such that it includes the pad buffer.
672 void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
674 q->dma_pad_mask = mask;
676 EXPORT_SYMBOL(blk_queue_dma_pad);
679 * blk_queue_update_dma_pad - update pad mask
680 * @q: the request queue for the device
681 * @mask: pad mask
683 * Update dma pad mask.
685 * Appending pad buffer to a request modifies the last entry of a
686 * scatter list such that it includes the pad buffer.
688 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
690 if (mask > q->dma_pad_mask)
691 q->dma_pad_mask = mask;
693 EXPORT_SYMBOL(blk_queue_update_dma_pad);
696 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
697 * @q: the request queue for the device
698 * @dma_drain_needed: fn which returns non-zero if drain is necessary
699 * @buf: physically contiguous buffer
700 * @size: size of the buffer in bytes
702 * Some devices have excess DMA problems and can't simply discard (or
703 * zero fill) the unwanted piece of the transfer. They have to have a
704 * real area of memory to transfer it into. The use case for this is
705 * ATAPI devices in DMA mode. If the packet command causes a transfer
706 * bigger than the transfer size some HBAs will lock up if there
707 * aren't DMA elements to contain the excess transfer. What this API
708 * does is adjust the queue so that the buf is always appended
709 * silently to the scatterlist.
711 * Note: This routine adjusts max_hw_segments to make room for appending
712 * the drain buffer. If you call blk_queue_max_segments() after calling
713 * this routine, you must set the limit to one fewer than your device
714 * can support otherwise there won't be room for the drain buffer.
716 int blk_queue_dma_drain(struct request_queue *q,
717 dma_drain_needed_fn *dma_drain_needed,
718 void *buf, unsigned int size)
720 if (queue_max_segments(q) < 2)
721 return -EINVAL;
722 /* make room for appending the drain */
723 blk_queue_max_segments(q, queue_max_segments(q) - 1);
724 q->dma_drain_needed = dma_drain_needed;
725 q->dma_drain_buffer = buf;
726 q->dma_drain_size = size;
728 return 0;
730 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
733 * blk_queue_segment_boundary - set boundary rules for segment merging
734 * @q: the request queue for the device
735 * @mask: the memory boundary mask
737 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
739 if (mask < PAGE_CACHE_SIZE - 1) {
740 mask = PAGE_CACHE_SIZE - 1;
741 printk(KERN_INFO "%s: set to minimum %lx\n",
742 __func__, mask);
745 q->limits.seg_boundary_mask = mask;
747 EXPORT_SYMBOL(blk_queue_segment_boundary);
750 * blk_queue_dma_alignment - set dma length and memory alignment
751 * @q: the request queue for the device
752 * @mask: alignment mask
754 * description:
755 * set required memory and length alignment for direct dma transactions.
756 * this is used when building direct io requests for the queue.
759 void blk_queue_dma_alignment(struct request_queue *q, int mask)
761 q->dma_alignment = mask;
763 EXPORT_SYMBOL(blk_queue_dma_alignment);
766 * blk_queue_update_dma_alignment - update dma length and memory alignment
767 * @q: the request queue for the device
768 * @mask: alignment mask
770 * description:
771 * update required memory and length alignment for direct dma transactions.
772 * If the requested alignment is larger than the current alignment, then
773 * the current queue alignment is updated to the new value, otherwise it
774 * is left alone. The design of this is to allow multiple objects
775 * (driver, device, transport etc) to set their respective
776 * alignments without having them interfere.
779 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
781 BUG_ON(mask > PAGE_SIZE);
783 if (mask > q->dma_alignment)
784 q->dma_alignment = mask;
786 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
788 static int __init blk_settings_init(void)
790 blk_max_low_pfn = max_low_pfn - 1;
791 blk_max_pfn = max_pfn - 1;
792 return 0;
794 subsys_initcall(blk_settings_init);