xref: /openbmc/linux/block/blk-settings.c (revision 50df3be7)
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 short 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 EXPORT_SYMBOL(disk_stack_limits);
669 
670 /**
671  * blk_queue_update_dma_pad - update pad mask
672  * @q:     the request queue for the device
673  * @mask:  pad mask
674  *
675  * Update dma pad mask.
676  *
677  * Appending pad buffer to a request modifies the last entry of a
678  * scatter list such that it includes the pad buffer.
679  **/
680 void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
681 {
682 	if (mask > q->dma_pad_mask)
683 		q->dma_pad_mask = mask;
684 }
685 EXPORT_SYMBOL(blk_queue_update_dma_pad);
686 
687 /**
688  * blk_queue_dma_drain - Set up a drain buffer for excess dma.
689  * @q:  the request queue for the device
690  * @dma_drain_needed: fn which returns non-zero if drain is necessary
691  * @buf:	physically contiguous buffer
692  * @size:	size of the buffer in bytes
693  *
694  * Some devices have excess DMA problems and can't simply discard (or
695  * zero fill) the unwanted piece of the transfer.  They have to have a
696  * real area of memory to transfer it into.  The use case for this is
697  * ATAPI devices in DMA mode.  If the packet command causes a transfer
698  * bigger than the transfer size some HBAs will lock up if there
699  * aren't DMA elements to contain the excess transfer.  What this API
700  * does is adjust the queue so that the buf is always appended
701  * silently to the scatterlist.
702  *
703  * Note: This routine adjusts max_hw_segments to make room for appending
704  * the drain buffer.  If you call blk_queue_max_segments() after calling
705  * this routine, you must set the limit to one fewer than your device
706  * can support otherwise there won't be room for the drain buffer.
707  */
708 int blk_queue_dma_drain(struct request_queue *q,
709 			       dma_drain_needed_fn *dma_drain_needed,
710 			       void *buf, unsigned int size)
711 {
712 	if (queue_max_segments(q) < 2)
713 		return -EINVAL;
714 	/* make room for appending the drain */
715 	blk_queue_max_segments(q, queue_max_segments(q) - 1);
716 	q->dma_drain_needed = dma_drain_needed;
717 	q->dma_drain_buffer = buf;
718 	q->dma_drain_size = size;
719 
720 	return 0;
721 }
722 EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
723 
724 /**
725  * blk_queue_segment_boundary - set boundary rules for segment merging
726  * @q:  the request queue for the device
727  * @mask:  the memory boundary mask
728  **/
729 void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
730 {
731 	if (mask < PAGE_SIZE - 1) {
732 		mask = PAGE_SIZE - 1;
733 		printk(KERN_INFO "%s: set to minimum %lx\n",
734 		       __func__, mask);
735 	}
736 
737 	q->limits.seg_boundary_mask = mask;
738 }
739 EXPORT_SYMBOL(blk_queue_segment_boundary);
740 
741 /**
742  * blk_queue_virt_boundary - set boundary rules for bio merging
743  * @q:  the request queue for the device
744  * @mask:  the memory boundary mask
745  **/
746 void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask)
747 {
748 	q->limits.virt_boundary_mask = mask;
749 
750 	/*
751 	 * Devices that require a virtual boundary do not support scatter/gather
752 	 * I/O natively, but instead require a descriptor list entry for each
753 	 * page (which might not be idential to the Linux PAGE_SIZE).  Because
754 	 * of that they are not limited by our notion of "segment size".
755 	 */
756 	if (mask)
757 		q->limits.max_segment_size = UINT_MAX;
758 }
759 EXPORT_SYMBOL(blk_queue_virt_boundary);
760 
761 /**
762  * blk_queue_dma_alignment - set dma length and memory alignment
763  * @q:     the request queue for the device
764  * @mask:  alignment mask
765  *
766  * description:
767  *    set required memory and length alignment for direct dma transactions.
768  *    this is used when building direct io requests for the queue.
769  *
770  **/
771 void blk_queue_dma_alignment(struct request_queue *q, int mask)
772 {
773 	q->dma_alignment = mask;
774 }
775 EXPORT_SYMBOL(blk_queue_dma_alignment);
776 
777 /**
778  * blk_queue_update_dma_alignment - update dma length and memory alignment
779  * @q:     the request queue for the device
780  * @mask:  alignment mask
781  *
782  * description:
783  *    update required memory and length alignment for direct dma transactions.
784  *    If the requested alignment is larger than the current alignment, then
785  *    the current queue alignment is updated to the new value, otherwise it
786  *    is left alone.  The design of this is to allow multiple objects
787  *    (driver, device, transport etc) to set their respective
788  *    alignments without having them interfere.
789  *
790  **/
791 void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
792 {
793 	BUG_ON(mask > PAGE_SIZE);
794 
795 	if (mask > q->dma_alignment)
796 		q->dma_alignment = mask;
797 }
798 EXPORT_SYMBOL(blk_queue_update_dma_alignment);
799 
800 /**
801  * blk_set_queue_depth - tell the block layer about the device queue depth
802  * @q:		the request queue for the device
803  * @depth:		queue depth
804  *
805  */
806 void blk_set_queue_depth(struct request_queue *q, unsigned int depth)
807 {
808 	q->queue_depth = depth;
809 	rq_qos_queue_depth_changed(q);
810 }
811 EXPORT_SYMBOL(blk_set_queue_depth);
812 
813 /**
814  * blk_queue_write_cache - configure queue's write cache
815  * @q:		the request queue for the device
816  * @wc:		write back cache on or off
817  * @fua:	device supports FUA writes, if true
818  *
819  * Tell the block layer about the write cache of @q.
820  */
821 void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
822 {
823 	if (wc)
824 		blk_queue_flag_set(QUEUE_FLAG_WC, q);
825 	else
826 		blk_queue_flag_clear(QUEUE_FLAG_WC, q);
827 	if (fua)
828 		blk_queue_flag_set(QUEUE_FLAG_FUA, q);
829 	else
830 		blk_queue_flag_clear(QUEUE_FLAG_FUA, q);
831 
832 	wbt_set_write_cache(q, test_bit(QUEUE_FLAG_WC, &q->queue_flags));
833 }
834 EXPORT_SYMBOL_GPL(blk_queue_write_cache);
835 
836 /**
837  * blk_queue_required_elevator_features - Set a queue required elevator features
838  * @q:		the request queue for the target device
839  * @features:	Required elevator features OR'ed together
840  *
841  * Tell the block layer that for the device controlled through @q, only the
842  * only elevators that can be used are those that implement at least the set of
843  * features specified by @features.
844  */
845 void blk_queue_required_elevator_features(struct request_queue *q,
846 					  unsigned int features)
847 {
848 	q->required_elevator_features = features;
849 }
850 EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features);
851 
852 /**
853  * blk_queue_can_use_dma_map_merging - configure queue for merging segments.
854  * @q:		the request queue for the device
855  * @dev:	the device pointer for dma
856  *
857  * Tell the block layer about merging the segments by dma map of @q.
858  */
859 bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
860 				       struct device *dev)
861 {
862 	unsigned long boundary = dma_get_merge_boundary(dev);
863 
864 	if (!boundary)
865 		return false;
866 
867 	/* No need to update max_segment_size. see blk_queue_virt_boundary() */
868 	blk_queue_virt_boundary(q, boundary);
869 
870 	return true;
871 }
872 EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
873 
874 static int __init blk_settings_init(void)
875 {
876 	blk_max_low_pfn = max_low_pfn - 1;
877 	blk_max_pfn = max_pfn - 1;
878 	return 0;
879 }
880 subsys_initcall(blk_settings_init);
881