1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Functions related to setting various queue properties from drivers
4 */
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/init.h>
8 #include <linux/bio.h>
9 #include <linux/blkdev.h>
10 #include <linux/memblock.h> /* for max_pfn/max_low_pfn */
11 #include <linux/gcd.h>
12 #include <linux/lcm.h>
13 #include <linux/jiffies.h>
14 #include <linux/gfp.h>
15 #include <linux/dma-mapping.h>
16
17 #include "blk.h"
18 #include "blk-wbt.h"
19
20 unsigned long blk_max_low_pfn;
21 EXPORT_SYMBOL(blk_max_low_pfn);
22
23 unsigned long blk_max_pfn;
24
25 void blk_queue_rq_timeout(struct request_queue *q, unsigned int timeout)
26 {
27 q->rq_timeout = timeout;
28 }
29 EXPORT_SYMBOL_GPL(blk_queue_rq_timeout);
30
31 /**
32 * blk_set_default_limits - reset limits to default values
33 * @lim: the queue_limits structure to reset
34 *
35 * Description:
36 * Returns a queue_limit struct to its default state.
37 */
38 void blk_set_default_limits(struct queue_limits *lim)
39 {
40 lim->max_segments = BLK_MAX_SEGMENTS;
41 lim->max_discard_segments = 1;
42 lim->max_integrity_segments = 0;
43 lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
44 lim->virt_boundary_mask = 0;
45 lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
46 lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
47 lim->max_dev_sectors = 0;
48 lim->chunk_sectors = 0;
49 lim->max_write_same_sectors = 0;
50 lim->max_write_zeroes_sectors = 0;
51 lim->max_discard_sectors = 0;
52 lim->max_hw_discard_sectors = 0;
53 lim->discard_granularity = 0;
54 lim->discard_alignment = 0;
55 lim->discard_misaligned = 0;
56 lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
57 lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
58 lim->alignment_offset = 0;
59 lim->io_opt = 0;
60 lim->misaligned = 0;
61 lim->zoned = BLK_ZONED_NONE;
62 }
63 EXPORT_SYMBOL(blk_set_default_limits);
64
65 /**
66 * blk_set_stacking_limits - set default limits for stacking devices
67 * @lim: the queue_limits structure to reset
68 *
69 * Description:
70 * Returns a queue_limit struct to its default state. Should be used
71 * by stacking drivers like DM that have no internal limits.
72 */
73 void blk_set_stacking_limits(struct queue_limits *lim)
74 {
75 blk_set_default_limits(lim);
76
77 /* Inherit limits from component devices */
78 lim->max_segments = USHRT_MAX;
79 lim->max_discard_segments = USHRT_MAX;
80 lim->max_hw_sectors = UINT_MAX;
81 lim->max_segment_size = UINT_MAX;
82 lim->max_sectors = UINT_MAX;
83 lim->max_dev_sectors = UINT_MAX;
84 lim->max_write_same_sectors = UINT_MAX;
85 lim->max_write_zeroes_sectors = UINT_MAX;
86 }
87 EXPORT_SYMBOL(blk_set_stacking_limits);
88
89 /**
90 * blk_queue_make_request - define an alternate make_request function for a device
91 * @q: the request queue for the device to be affected
92 * @mfn: the alternate make_request function
93 *
94 * Description:
95 * The normal way for &struct bios to be passed to a device
96 * driver is for them to be collected into requests on a request
97 * queue, and then to allow the device driver to select requests
98 * off that queue when it is ready. This works well for many block
99 * devices. However some block devices (typically virtual devices
100 * such as md or lvm) do not benefit from the processing on the
101 * request queue, and are served best by having the requests passed
102 * directly to them. This can be achieved by providing a function
103 * to blk_queue_make_request().
104 *
105 * Caveat:
106 * The driver that does this *must* be able to deal appropriately
107 * with buffers in "highmemory". This can be accomplished by either calling
108 * kmap_atomic() to get a temporary kernel mapping, or by calling
109 * blk_queue_bounce() to create a buffer in normal memory.
110 **/
111 void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
112 {
113 /*
114 * set defaults
115 */
116 q->nr_requests = BLKDEV_MAX_RQ;
117
118 q->make_request_fn = mfn;
119 blk_queue_dma_alignment(q, 511);
120
121 blk_set_default_limits(&q->limits);
122 }
123 EXPORT_SYMBOL(blk_queue_make_request);
124
125 /**
126 * blk_queue_bounce_limit - set bounce buffer limit for queue
127 * @q: the request queue for the device
128 * @max_addr: the maximum address the device can handle
129 *
130 * Description:
131 * Different hardware can have different requirements as to what pages
132 * it can do I/O directly to. A low level driver can call
133 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
134 * buffers for doing I/O to pages residing above @max_addr.
135 **/
136 void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr)
137 {
138 unsigned long b_pfn = max_addr >> PAGE_SHIFT;
139 int dma = 0;
140
141 q->bounce_gfp = GFP_NOIO;
142 #if BITS_PER_LONG == 64
143 /*
144 * Assume anything <= 4GB can be handled by IOMMU. Actually
145 * some IOMMUs can handle everything, but I don't know of a
146 * way to test this here.
147 */
148 if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
149 dma = 1;
150 q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
151 #else
152 if (b_pfn < blk_max_low_pfn)
153 dma = 1;
154 q->limits.bounce_pfn = b_pfn;
155 #endif
156 if (dma) {
157 init_emergency_isa_pool();
158 q->bounce_gfp = GFP_NOIO | GFP_DMA;
159 q->limits.bounce_pfn = b_pfn;
160 }
161 }
162 EXPORT_SYMBOL(blk_queue_bounce_limit);
163
164 /**
165 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
166 * @q: the request queue for the device
167 * @max_hw_sectors: max hardware sectors in the usual 512b unit
168 *
169 * Description:
170 * Enables a low level driver to set a hard upper limit,
171 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
172 * the device driver based upon the capabilities of the I/O
173 * controller.
174 *
175 * max_dev_sectors is a hard limit imposed by the storage device for
176 * READ/WRITE requests. It is set by the disk driver.
177 *
178 * max_sectors is a soft limit imposed by the block layer for
179 * filesystem type requests. This value can be overridden on a
180 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
181 * The soft limit can not exceed max_hw_sectors.
182 **/
183 void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
184 {
185 struct queue_limits *limits = &q->limits;
186 unsigned int max_sectors;
187
188 if ((max_hw_sectors << 9) < PAGE_SIZE) {
189 max_hw_sectors = 1 << (PAGE_SHIFT - 9);
190 printk(KERN_INFO "%s: set to minimum %d\n",
191 __func__, max_hw_sectors);
192 }
193
194 limits->max_hw_sectors = max_hw_sectors;
195 max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
196 max_sectors = min_t(unsigned int, max_sectors, BLK_DEF_MAX_SECTORS);
197 limits->max_sectors = max_sectors;
198 q->backing_dev_info->io_pages = max_sectors >> (PAGE_SHIFT - 9);
199 }
200 EXPORT_SYMBOL(blk_queue_max_hw_sectors);
201
202 /**
203 * blk_queue_chunk_sectors - set size of the chunk for this queue
204 * @q: the request queue for the device
205 * @chunk_sectors: chunk sectors in the usual 512b unit
206 *
207 * Description:
208 * If a driver doesn't want IOs to cross a given chunk size, it can set
209 * this limit and prevent merging across chunks. Note that the chunk size
210 * must currently be a power-of-2 in sectors. Also note that the block
211 * layer must accept a page worth of data at any offset. So if the
212 * crossing of chunks is a hard limitation in the driver, it must still be
213 * prepared to split single page bios.
214 **/
215 void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors)
216 {
217 BUG_ON(!is_power_of_2(chunk_sectors));
218 q->limits.chunk_sectors = chunk_sectors;
219 }
220 EXPORT_SYMBOL(blk_queue_chunk_sectors);
221
222 /**
223 * blk_queue_max_discard_sectors - set max sectors for a single discard
224 * @q: the request queue for the device
225 * @max_discard_sectors: maximum number of sectors to discard
226 **/
227 void blk_queue_max_discard_sectors(struct request_queue *q,
228 unsigned int max_discard_sectors)
229 {
230 q->limits.max_hw_discard_sectors = max_discard_sectors;
231 q->limits.max_discard_sectors = max_discard_sectors;
232 }
233 EXPORT_SYMBOL(blk_queue_max_discard_sectors);
234
235 /**
236 * blk_queue_max_write_same_sectors - set max sectors for a single write same
237 * @q: the request queue for the device
238 * @max_write_same_sectors: maximum number of sectors to write per command
239 **/
240 void blk_queue_max_write_same_sectors(struct request_queue *q,
241 unsigned int max_write_same_sectors)
242 {
243 q->limits.max_write_same_sectors = max_write_same_sectors;
244 }
245 EXPORT_SYMBOL(blk_queue_max_write_same_sectors);
246
247 /**
248 * blk_queue_max_write_zeroes_sectors - set max sectors for a single
249 * write zeroes
250 * @q: the request queue for the device
251 * @max_write_zeroes_sectors: maximum number of sectors to write per command
252 **/
253 void blk_queue_max_write_zeroes_sectors(struct request_queue *q,
254 unsigned int max_write_zeroes_sectors)
255 {
256 q->limits.max_write_zeroes_sectors = max_write_zeroes_sectors;
257 }
258 EXPORT_SYMBOL(blk_queue_max_write_zeroes_sectors);
259
260 /**
261 * blk_queue_max_segments - set max hw segments for a request for this queue
262 * @q: the request queue for the device
263 * @max_segments: max number of segments
264 *
265 * Description:
266 * Enables a low level driver to set an upper limit on the number of
267 * hw data segments in a request.
268 **/
269 void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
270 {
271 if (!max_segments) {
272 max_segments = 1;
273 printk(KERN_INFO "%s: set to minimum %d\n",
274 __func__, max_segments);
275 }
276
277 q->limits.max_segments = max_segments;
278 }
279 EXPORT_SYMBOL(blk_queue_max_segments);
280
281 /**
282 * blk_queue_max_discard_segments - set max segments for discard requests
283 * @q: the request queue for the device
284 * @max_segments: max number of segments
285 *
286 * Description:
287 * Enables a low level driver to set an upper limit on the number of
288 * segments in a discard request.
289 **/
290 void blk_queue_max_discard_segments(struct request_queue *q,
291 unsigned short max_segments)
292 {
293 q->limits.max_discard_segments = max_segments;
294 }
295 EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments);
296
297 /**
298 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
299 * @q: the request queue for the device
300 * @max_size: max size of segment in bytes
301 *
302 * Description:
303 * Enables a low level driver to set an upper limit on the size of a
304 * coalesced segment
305 **/
306 void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
307 {
308 if (max_size < PAGE_SIZE) {
309 max_size = PAGE_SIZE;
310 printk(KERN_INFO "%s: set to minimum %d\n",
311 __func__, max_size);
312 }
313
314 /* see blk_queue_virt_boundary() for the explanation */
315 WARN_ON_ONCE(q->limits.virt_boundary_mask);
316
317 q->limits.max_segment_size = max_size;
318 }
319 EXPORT_SYMBOL(blk_queue_max_segment_size);
320
321 /**
322 * blk_queue_logical_block_size - set logical block size for the queue
323 * @q: the request queue for the device
324 * @size: the logical block size, in bytes
325 *
326 * Description:
327 * This should be set to the lowest possible block size that the
328 * storage device can address. The default of 512 covers most
329 * hardware.
330 **/
331 void blk_queue_logical_block_size(struct request_queue *q, unsigned int size)
332 {
333 q->limits.logical_block_size = size;
334
335 if (q->limits.physical_block_size < size)
336 q->limits.physical_block_size = size;
337
338 if (q->limits.io_min < q->limits.physical_block_size)
339 q->limits.io_min = q->limits.physical_block_size;
340 }
341 EXPORT_SYMBOL(blk_queue_logical_block_size);
342
343 /**
344 * blk_queue_physical_block_size - set physical block size for the queue
345 * @q: the request queue for the device
346 * @size: the physical block size, in bytes
347 *
348 * Description:
349 * This should be set to the lowest possible sector size that the
350 * hardware can operate on without reverting to read-modify-write
351 * operations.
352 */
353 void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
354 {
355 q->limits.physical_block_size = size;
356
357 if (q->limits.physical_block_size < q->limits.logical_block_size)
358 q->limits.physical_block_size = q->limits.logical_block_size;
359
360 if (q->limits.io_min < q->limits.physical_block_size)
361 q->limits.io_min = q->limits.physical_block_size;
362 }
363 EXPORT_SYMBOL(blk_queue_physical_block_size);
364
365 /**
366 * blk_queue_alignment_offset - set physical block alignment offset
367 * @q: the request queue for the device
368 * @offset: alignment offset in bytes
369 *
370 * Description:
371 * Some devices are naturally misaligned to compensate for things like
372 * the legacy DOS partition table 63-sector offset. Low-level drivers
373 * should call this function for devices whose first sector is not
374 * naturally aligned.
375 */
376 void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
377 {
378 q->limits.alignment_offset =
379 offset & (q->limits.physical_block_size - 1);
380 q->limits.misaligned = 0;
381 }
382 EXPORT_SYMBOL(blk_queue_alignment_offset);
383
384 /**
385 * blk_limits_io_min - set minimum request size for a device
386 * @limits: the queue limits
387 * @min: smallest I/O size in bytes
388 *
389 * Description:
390 * Some devices have an internal block size bigger than the reported
391 * hardware sector size. This function can be used to signal the
392 * smallest I/O the device can perform without incurring a performance
393 * penalty.
394 */
395 void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
396 {
397 limits->io_min = min;
398
399 if (limits->io_min < limits->logical_block_size)
400 limits->io_min = limits->logical_block_size;
401
402 if (limits->io_min < limits->physical_block_size)
403 limits->io_min = limits->physical_block_size;
404 }
405 EXPORT_SYMBOL(blk_limits_io_min);
406
407 /**
408 * blk_queue_io_min - set minimum request size for the queue
409 * @q: the request queue for the device
410 * @min: smallest I/O size in bytes
411 *
412 * Description:
413 * Storage devices may report a granularity or preferred minimum I/O
414 * size which is the smallest request the device can perform without
415 * incurring a performance penalty. For disk drives this is often the
416 * physical block size. For RAID arrays it is often the stripe chunk
417 * size. A properly aligned multiple of minimum_io_size is the
418 * preferred request size for workloads where a high number of I/O
419 * operations is desired.
420 */
421 void blk_queue_io_min(struct request_queue *q, unsigned int min)
422 {
423 blk_limits_io_min(&q->limits, min);
424 }
425 EXPORT_SYMBOL(blk_queue_io_min);
426
427 /**
428 * blk_limits_io_opt - set optimal request size for a device
429 * @limits: the queue limits
430 * @opt: smallest I/O size in bytes
431 *
432 * Description:
433 * Storage devices may report an optimal I/O size, which is the
434 * device's preferred unit for sustained I/O. This is rarely reported
435 * for disk drives. For RAID arrays it is usually the stripe width or
436 * the internal track size. A properly aligned multiple of
437 * optimal_io_size is the preferred request size for workloads where
438 * sustained throughput is desired.
439 */
440 void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
441 {
442 limits->io_opt = opt;
443 }
444 EXPORT_SYMBOL(blk_limits_io_opt);
445
446 /**
447 * blk_queue_io_opt - set optimal request size for the queue
448 * @q: the request queue for the device
449 * @opt: optimal request size in bytes
450 *
451 * Description:
452 * Storage devices may report an optimal I/O size, which is the
453 * device's preferred unit for sustained I/O. This is rarely reported
454 * for disk drives. For RAID arrays it is usually the stripe width or
455 * the internal track size. A properly aligned multiple of
456 * optimal_io_size is the preferred request size for workloads where
457 * sustained throughput is desired.
458 */
459 void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
460 {
461 blk_limits_io_opt(&q->limits, opt);
462 }
463 EXPORT_SYMBOL(blk_queue_io_opt);
464
465 /**
466 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
467 * @t: the stacking driver (top)
468 * @b: the underlying device (bottom)
469 **/
470 void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
471 {
472 blk_stack_limits(&t->limits, &b->limits, 0);
473 }
474 EXPORT_SYMBOL(blk_queue_stack_limits);
475
476 /**
477 * blk_stack_limits - adjust queue_limits for stacked devices
478 * @t: the stacking driver limits (top device)
479 * @b: the underlying queue limits (bottom, component device)
480 * @start: first data sector within component device
481 *
482 * Description:
483 * This function is used by stacking drivers like MD and DM to ensure
484 * that all component devices have compatible block sizes and
485 * alignments. The stacking driver must provide a queue_limits
486 * struct (top) and then iteratively call the stacking function for
487 * all component (bottom) devices. The stacking function will
488 * attempt to combine the values and ensure proper alignment.
489 *
490 * Returns 0 if the top and bottom queue_limits are compatible. The
491 * top device's block sizes and alignment offsets may be adjusted to
492 * ensure alignment with the bottom device. If no compatible sizes
493 * and alignments exist, -1 is returned and the resulting top
494 * queue_limits will have the misaligned flag set to indicate that
495 * the alignment_offset is undefined.
496 */
497 int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
498 sector_t start)
499 {
500 unsigned int top, bottom, alignment, ret = 0;
501
502 t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
503 t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
504 t->max_dev_sectors = min_not_zero(t->max_dev_sectors, b->max_dev_sectors);
505 t->max_write_same_sectors = min(t->max_write_same_sectors,
506 b->max_write_same_sectors);
507 t->max_write_zeroes_sectors = min(t->max_write_zeroes_sectors,
508 b->max_write_zeroes_sectors);
509 t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
510
511 t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
512 b->seg_boundary_mask);
513 t->virt_boundary_mask = min_not_zero(t->virt_boundary_mask,
514 b->virt_boundary_mask);
515
516 t->max_segments = min_not_zero(t->max_segments, b->max_segments);
517 t->max_discard_segments = min_not_zero(t->max_discard_segments,
518 b->max_discard_segments);
519 t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
520 b->max_integrity_segments);
521
522 t->max_segment_size = min_not_zero(t->max_segment_size,
523 b->max_segment_size);
524
525 t->misaligned |= b->misaligned;
526
527 alignment = queue_limit_alignment_offset(b, start);
528
529 /* Bottom device has different alignment. Check that it is
530 * compatible with the current top alignment.
531 */
532 if (t->alignment_offset != alignment) {
533
534 top = max(t->physical_block_size, t->io_min)
535 + t->alignment_offset;
536 bottom = max(b->physical_block_size, b->io_min) + alignment;
537
538 /* Verify that top and bottom intervals line up */
539 if (max(top, bottom) % min(top, bottom)) {
540 t->misaligned = 1;
541 ret = -1;
542 }
543 }
544
545 t->logical_block_size = max(t->logical_block_size,
546 b->logical_block_size);
547
548 t->physical_block_size = max(t->physical_block_size,
549 b->physical_block_size);
550
551 t->io_min = max(t->io_min, b->io_min);
552 t->io_opt = lcm_not_zero(t->io_opt, b->io_opt);
553
554 /* Physical block size a multiple of the logical block size? */
555 if (t->physical_block_size & (t->logical_block_size - 1)) {
556 t->physical_block_size = t->logical_block_size;
557 t->misaligned = 1;
558 ret = -1;
559 }
560
561 /* Minimum I/O a multiple of the physical block size? */
562 if (t->io_min & (t->physical_block_size - 1)) {
563 t->io_min = t->physical_block_size;
564 t->misaligned = 1;
565 ret = -1;
566 }
567
568 /* Optimal I/O a multiple of the physical block size? */
569 if (t->io_opt & (t->physical_block_size - 1)) {
570 t->io_opt = 0;
571 t->misaligned = 1;
572 ret = -1;
573 }
574
575 t->raid_partial_stripes_expensive =
576 max(t->raid_partial_stripes_expensive,
577 b->raid_partial_stripes_expensive);
578
579 /* Find lowest common alignment_offset */
580 t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
581 % max(t->physical_block_size, t->io_min);
582
583 /* Verify that new alignment_offset is on a logical block boundary */
584 if (t->alignment_offset & (t->logical_block_size - 1)) {
585 t->misaligned = 1;
586 ret = -1;
587 }
588
589 /* Discard alignment and granularity */
590 if (b->discard_granularity) {
591 alignment = queue_limit_discard_alignment(b, start);
592
593 if (t->discard_granularity != 0 &&
594 t->discard_alignment != alignment) {
595 top = t->discard_granularity + t->discard_alignment;
596 bottom = b->discard_granularity + alignment;
597
598 /* Verify that top and bottom intervals line up */
599 if ((max(top, bottom) % min(top, bottom)) != 0)
600 t->discard_misaligned = 1;
601 }
602
603 t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
604 b->max_discard_sectors);
605 t->max_hw_discard_sectors = min_not_zero(t->max_hw_discard_sectors,
606 b->max_hw_discard_sectors);
607 t->discard_granularity = max(t->discard_granularity,
608 b->discard_granularity);
609 t->discard_alignment = lcm_not_zero(t->discard_alignment, alignment) %
610 t->discard_granularity;
611 }
612
613 if (b->chunk_sectors)
614 t->chunk_sectors = min_not_zero(t->chunk_sectors,
615 b->chunk_sectors);
616
617 return ret;
618 }
619 EXPORT_SYMBOL(blk_stack_limits);
620
621 /**
622 * bdev_stack_limits - adjust queue limits for stacked drivers
623 * @t: the stacking driver limits (top device)
624 * @bdev: the component block_device (bottom)
625 * @start: first data sector within component device
626 *
627 * Description:
628 * Merges queue limits for a top device and a block_device. Returns
629 * 0 if alignment didn't change. Returns -1 if adding the bottom
630 * device caused misalignment.
631 */
632 int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
633 sector_t start)
634 {
635 struct request_queue *bq = bdev_get_queue(bdev);
636
637 start += get_start_sect(bdev);
638
639 return blk_stack_limits(t, &bq->limits, start);
640 }
641 EXPORT_SYMBOL(bdev_stack_limits);
642
643 /**
644 * disk_stack_limits - adjust queue limits for stacked drivers
645 * @disk: MD/DM gendisk (top)
646 * @bdev: the underlying block device (bottom)
647 * @offset: offset to beginning of data within component device
648 *
649 * Description:
650 * Merges the limits for a top level gendisk and a bottom level
651 * block_device.
652 */
653 void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
654 sector_t offset)
655 {
656 struct request_queue *t = disk->queue;
657
658 if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
659 char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
660
661 disk_name(disk, 0, top);
662 bdevname(bdev, bottom);
663
664 printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
665 top, bottom);
666 }
667
668 t->backing_dev_info->io_pages =
669 t->limits.max_sectors >> (PAGE_SHIFT - 9);
670 }
671 EXPORT_SYMBOL(disk_stack_limits);
672
673 /**
674 * blk_queue_update_dma_pad - update pad mask
675 * @q: the request queue for the device
676 * @mask: pad mask
677 *
678 * Update dma pad mask.
679 *
680 * Appending pad buffer to a request modifies the last entry of a
681 * scatter list such that it includes the pad buffer.
682 **/
683 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
684 {
685 if (mask > q->dma_pad_mask)
686 q->dma_pad_mask = mask;
687 }
688 EXPORT_SYMBOL(blk_queue_update_dma_pad);
689
690 /**
691 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
692 * @q: the request queue for the device
693 * @dma_drain_needed: fn which returns non-zero if drain is necessary
694 * @buf: physically contiguous buffer
695 * @size: size of the buffer in bytes
696 *
697 * Some devices have excess DMA problems and can't simply discard (or
698 * zero fill) the unwanted piece of the transfer. They have to have a
699 * real area of memory to transfer it into. The use case for this is
700 * ATAPI devices in DMA mode. If the packet command causes a transfer
701 * bigger than the transfer size some HBAs will lock up if there
702 * aren't DMA elements to contain the excess transfer. What this API
703 * does is adjust the queue so that the buf is always appended
704 * silently to the scatterlist.
705 *
706 * Note: This routine adjusts max_hw_segments to make room for appending
707 * the drain buffer. If you call blk_queue_max_segments() after calling
708 * this routine, you must set the limit to one fewer than your device
709 * can support otherwise there won't be room for the drain buffer.
710 */
711 int blk_queue_dma_drain(struct request_queue *q,
712 dma_drain_needed_fn *dma_drain_needed,
713 void *buf, unsigned int size)
714 {
715 if (queue_max_segments(q) < 2)
716 return -EINVAL;
717 /* make room for appending the drain */
718 blk_queue_max_segments(q, queue_max_segments(q) - 1);
719 q->dma_drain_needed = dma_drain_needed;
720 q->dma_drain_buffer = buf;
721 q->dma_drain_size = size;
722
723 return 0;
724 }
725 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
726
727 /**
728 * blk_queue_segment_boundary - set boundary rules for segment merging
729 * @q: the request queue for the device
730 * @mask: the memory boundary mask
731 **/
732 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
733 {
734 if (mask < PAGE_SIZE - 1) {
735 mask = PAGE_SIZE - 1;
736 printk(KERN_INFO "%s: set to minimum %lx\n",
737 __func__, mask);
738 }
739
740 q->limits.seg_boundary_mask = mask;
741 }
742 EXPORT_SYMBOL(blk_queue_segment_boundary);
743
744 /**
745 * blk_queue_virt_boundary - set boundary rules for bio merging
746 * @q: the request queue for the device
747 * @mask: the memory boundary mask
748 **/
749 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
750 {
751 q->limits.virt_boundary_mask = mask;
752
753 /*
754 * Devices that require a virtual boundary do not support scatter/gather
755 * I/O natively, but instead require a descriptor list entry for each
756 * page (which might not be idential to the Linux PAGE_SIZE). Because
757 * of that they are not limited by our notion of "segment size".
758 */
759 if (mask)
760 q->limits.max_segment_size = UINT_MAX;
761 }
762 EXPORT_SYMBOL(blk_queue_virt_boundary);
763
764 /**
765 * blk_queue_dma_alignment - set dma length and memory alignment
766 * @q: the request queue for the device
767 * @mask: alignment mask
768 *
769 * description:
770 * set required memory and length alignment for direct dma transactions.
771 * this is used when building direct io requests for the queue.
772 *
773 **/
774 void blk_queue_dma_alignment(struct request_queue *q, int mask)
775 {
776 q->dma_alignment = mask;
777 }
778 EXPORT_SYMBOL(blk_queue_dma_alignment);
779
780 /**
781 * blk_queue_update_dma_alignment - update dma length and memory alignment
782 * @q: the request queue for the device
783 * @mask: alignment mask
784 *
785 * description:
786 * update required memory and length alignment for direct dma transactions.
787 * If the requested alignment is larger than the current alignment, then
788 * the current queue alignment is updated to the new value, otherwise it
789 * is left alone. The design of this is to allow multiple objects
790 * (driver, device, transport etc) to set their respective
791 * alignments without having them interfere.
792 *
793 **/
794 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
795 {
796 BUG_ON(mask > PAGE_SIZE);
797
798 if (mask > q->dma_alignment)
799 q->dma_alignment = mask;
800 }
801 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
802
803 /**
804 * blk_set_queue_depth - tell the block layer about the device queue depth
805 * @q: the request queue for the device
806 * @depth: queue depth
807 *
808 */
809 void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
810 {
811 q->queue_depth = depth;
812 rq_qos_queue_depth_changed(q);
813 }
814 EXPORT_SYMBOL(blk_set_queue_depth);
815
816 /**
817 * blk_queue_write_cache - configure queue's write cache
818 * @q: the request queue for the device
819 * @wc: write back cache on or off
820 * @fua: device supports FUA writes, if true
821 *
822 * Tell the block layer about the write cache of @q.
823 */
824 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
825 {
826 if (wc)
827 blk_queue_flag_set(QUEUE_FLAG_WC, q);
828 else
829 blk_queue_flag_clear(QUEUE_FLAG_WC, q);
830 if (fua)
831 blk_queue_flag_set(QUEUE_FLAG_FUA, q);
832 else
833 blk_queue_flag_clear(QUEUE_FLAG_FUA, q);
834
835 wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
836 }
837 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
838
839 /**
840 * blk_queue_required_elevator_features - Set a queue required elevator features
841 * @q: the request queue for the target device
842 * @features: Required elevator features OR'ed together
843 *
844 * Tell the block layer that for the device controlled through @q, only the
845 * only elevators that can be used are those that implement at least the set of
846 * features specified by @features.
847 */
848 void blk_queue_required_elevator_features(struct request_queue *q,
849 unsigned int features)
850 {
851 q->required_elevator_features = features;
852 }
853 EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features);
854
855 /**
856 * blk_queue_can_use_dma_map_merging - configure queue for merging segments.
857 * @q: the request queue for the device
858 * @dev: the device pointer for dma
859 *
860 * Tell the block layer about merging the segments by dma map of @q.
861 */
862 bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
863 struct device *dev)
864 {
865 unsigned long boundary = dma_get_merge_boundary(dev);
866
867 if (!boundary)
868 return false;
869
870 /* No need to update max_segment_size. see blk_queue_virt_boundary() */
871 blk_queue_virt_boundary(q, boundary);
872
873 return true;
874 }
875 EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
876
877 static int __init blk_settings_init(void)
878 {
879 blk_max_low_pfn = max_low_pfn - 1;
880 blk_max_pfn = max_pfn - 1;
881 return 0;
882 }
883 subsys_initcall(blk_settings_init);