Root/block/blk-settings.c

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

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