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. Can be used by
108 * stacking drivers like DM that stage table swaps and reuse an
109 * existing device queue.
110 */
111void blk_set_default_limits(struct queue_limits *lim)
112{
113    lim->max_segments = BLK_MAX_SEGMENTS;
114    lim->max_integrity_segments = 0;
115    lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
116    lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
117    lim->max_sectors = BLK_DEF_MAX_SECTORS;
118    lim->max_hw_sectors = INT_MAX;
119    lim->max_discard_sectors = 0;
120    lim->discard_granularity = 0;
121    lim->discard_alignment = 0;
122    lim->discard_misaligned = 0;
123    lim->discard_zeroes_data = -1;
124    lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
125    lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
126    lim->alignment_offset = 0;
127    lim->io_opt = 0;
128    lim->misaligned = 0;
129    lim->cluster = 1;
130}
131EXPORT_SYMBOL(blk_set_default_limits);
132
133/**
134 * blk_queue_make_request - define an alternate make_request function for a device
135 * @q: the request queue for the device to be affected
136 * @mfn: the alternate make_request function
137 *
138 * Description:
139 * The normal way for &struct bios to be passed to a device
140 * driver is for them to be collected into requests on a request
141 * queue, and then to allow the device driver to select requests
142 * off that queue when it is ready. This works well for many block
143 * devices. However some block devices (typically virtual devices
144 * such as md or lvm) do not benefit from the processing on the
145 * request queue, and are served best by having the requests passed
146 * directly to them. This can be achieved by providing a function
147 * to blk_queue_make_request().
148 *
149 * Caveat:
150 * The driver that does this *must* be able to deal appropriately
151 * with buffers in "highmemory". This can be accomplished by either calling
152 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
153 * blk_queue_bounce() to create a buffer in normal memory.
154 **/
155void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
156{
157    /*
158     * set defaults
159     */
160    q->nr_requests = BLKDEV_MAX_RQ;
161
162    q->make_request_fn = mfn;
163    blk_queue_dma_alignment(q, 511);
164    blk_queue_congestion_threshold(q);
165    q->nr_batching = BLK_BATCH_REQ;
166
167    q->unplug_thresh = 4; /* hmm */
168    q->unplug_delay = msecs_to_jiffies(3); /* 3 milliseconds */
169    if (q->unplug_delay == 0)
170        q->unplug_delay = 1;
171
172    q->unplug_timer.function = blk_unplug_timeout;
173    q->unplug_timer.data = (unsigned long)q;
174
175    blk_set_default_limits(&q->limits);
176    blk_queue_max_hw_sectors(q, BLK_SAFE_MAX_SECTORS);
177
178    /*
179     * If the caller didn't supply a lock, fall back to our embedded
180     * per-queue locks
181     */
182    if (!q->queue_lock)
183        q->queue_lock = &q->__queue_lock;
184
185    /*
186     * by default assume old behaviour and bounce for any highmem page
187     */
188    blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
189}
190EXPORT_SYMBOL(blk_queue_make_request);
191
192/**
193 * blk_queue_bounce_limit - set bounce buffer limit for queue
194 * @q: the request queue for the device
195 * @dma_mask: the maximum address the device can handle
196 *
197 * Description:
198 * Different hardware can have different requirements as to what pages
199 * it can do I/O directly to. A low level driver can call
200 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
201 * buffers for doing I/O to pages residing above @dma_mask.
202 **/
203void blk_queue_bounce_limit(struct request_queue *q, u64 dma_mask)
204{
205    unsigned long b_pfn = dma_mask >> PAGE_SHIFT;
206    int dma = 0;
207
208    q->bounce_gfp = GFP_NOIO;
209#if BITS_PER_LONG == 64
210    /*
211     * Assume anything <= 4GB can be handled by IOMMU. Actually
212     * some IOMMUs can handle everything, but I don't know of a
213     * way to test this here.
214     */
215    if (b_pfn < (min_t(u64, 0xffffffffUL, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
216        dma = 1;
217    q->limits.bounce_pfn = max(max_low_pfn, b_pfn);
218#else
219    if (b_pfn < blk_max_low_pfn)
220        dma = 1;
221    q->limits.bounce_pfn = b_pfn;
222#endif
223    if (dma) {
224        init_emergency_isa_pool();
225        q->bounce_gfp = GFP_NOIO | GFP_DMA;
226        q->limits.bounce_pfn = b_pfn;
227    }
228}
229EXPORT_SYMBOL(blk_queue_bounce_limit);
230
231/**
232 * blk_limits_max_hw_sectors - set hard and soft limit of max sectors for request
233 * @limits: the queue limits
234 * @max_hw_sectors: max hardware sectors in the usual 512b unit
235 *
236 * Description:
237 * Enables a low level driver to set a hard upper limit,
238 * max_hw_sectors, on the size of requests. max_hw_sectors is set by
239 * the device driver based upon the combined capabilities of I/O
240 * controller and storage device.
241 *
242 * max_sectors is a soft limit imposed by the block layer for
243 * filesystem type requests. This value can be overridden on a
244 * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
245 * The soft limit can not exceed max_hw_sectors.
246 **/
247void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
248{
249    if ((max_hw_sectors << 9) < PAGE_CACHE_SIZE) {
250        max_hw_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
251        printk(KERN_INFO "%s: set to minimum %d\n",
252               __func__, max_hw_sectors);
253    }
254
255    limits->max_hw_sectors = max_hw_sectors;
256    limits->max_sectors = min_t(unsigned int, max_hw_sectors,
257                    BLK_DEF_MAX_SECTORS);
258}
259EXPORT_SYMBOL(blk_limits_max_hw_sectors);
260
261/**
262 * blk_queue_max_hw_sectors - set max sectors for a request for this queue
263 * @q: the request queue for the device
264 * @max_hw_sectors: max hardware sectors in the usual 512b unit
265 *
266 * Description:
267 * See description for blk_limits_max_hw_sectors().
268 **/
269void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors)
270{
271    blk_limits_max_hw_sectors(&q->limits, max_hw_sectors);
272}
273EXPORT_SYMBOL(blk_queue_max_hw_sectors);
274
275/**
276 * blk_queue_max_discard_sectors - set max sectors for a single discard
277 * @q: the request queue for the device
278 * @max_discard_sectors: maximum number of sectors to discard
279 **/
280void blk_queue_max_discard_sectors(struct request_queue *q,
281        unsigned int max_discard_sectors)
282{
283    q->limits.max_discard_sectors = max_discard_sectors;
284}
285EXPORT_SYMBOL(blk_queue_max_discard_sectors);
286
287/**
288 * blk_queue_max_segments - set max hw segments for a request for this queue
289 * @q: the request queue for the device
290 * @max_segments: max number of segments
291 *
292 * Description:
293 * Enables a low level driver to set an upper limit on the number of
294 * hw data segments in a request.
295 **/
296void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments)
297{
298    if (!max_segments) {
299        max_segments = 1;
300        printk(KERN_INFO "%s: set to minimum %d\n",
301               __func__, max_segments);
302    }
303
304    q->limits.max_segments = max_segments;
305}
306EXPORT_SYMBOL(blk_queue_max_segments);
307
308/**
309 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
310 * @q: the request queue for the device
311 * @max_size: max size of segment in bytes
312 *
313 * Description:
314 * Enables a low level driver to set an upper limit on the size of a
315 * coalesced segment
316 **/
317void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size)
318{
319    if (max_size < PAGE_CACHE_SIZE) {
320        max_size = PAGE_CACHE_SIZE;
321        printk(KERN_INFO "%s: set to minimum %d\n",
322               __func__, max_size);
323    }
324
325    q->limits.max_segment_size = max_size;
326}
327EXPORT_SYMBOL(blk_queue_max_segment_size);
328
329/**
330 * blk_queue_logical_block_size - set logical block size for the queue
331 * @q: the request queue for the device
332 * @size: the logical block size, in bytes
333 *
334 * Description:
335 * This should be set to the lowest possible block size that the
336 * storage device can address. The default of 512 covers most
337 * hardware.
338 **/
339void blk_queue_logical_block_size(struct request_queue *q, unsigned short size)
340{
341    q->limits.logical_block_size = size;
342
343    if (q->limits.physical_block_size < size)
344        q->limits.physical_block_size = size;
345
346    if (q->limits.io_min < q->limits.physical_block_size)
347        q->limits.io_min = q->limits.physical_block_size;
348}
349EXPORT_SYMBOL(blk_queue_logical_block_size);
350
351/**
352 * blk_queue_physical_block_size - set physical block size for the queue
353 * @q: the request queue for the device
354 * @size: the physical block size, in bytes
355 *
356 * Description:
357 * This should be set to the lowest possible sector size that the
358 * hardware can operate on without reverting to read-modify-write
359 * operations.
360 */
361void blk_queue_physical_block_size(struct request_queue *q, unsigned int size)
362{
363    q->limits.physical_block_size = size;
364
365    if (q->limits.physical_block_size < q->limits.logical_block_size)
366        q->limits.physical_block_size = q->limits.logical_block_size;
367
368    if (q->limits.io_min < q->limits.physical_block_size)
369        q->limits.io_min = q->limits.physical_block_size;
370}
371EXPORT_SYMBOL(blk_queue_physical_block_size);
372
373/**
374 * blk_queue_alignment_offset - set physical block alignment offset
375 * @q: the request queue for the device
376 * @offset: alignment offset in bytes
377 *
378 * Description:
379 * Some devices are naturally misaligned to compensate for things like
380 * the legacy DOS partition table 63-sector offset. Low-level drivers
381 * should call this function for devices whose first sector is not
382 * naturally aligned.
383 */
384void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset)
385{
386    q->limits.alignment_offset =
387        offset & (q->limits.physical_block_size - 1);
388    q->limits.misaligned = 0;
389}
390EXPORT_SYMBOL(blk_queue_alignment_offset);
391
392/**
393 * blk_limits_io_min - set minimum request size for a device
394 * @limits: the queue limits
395 * @min: smallest I/O size in bytes
396 *
397 * Description:
398 * Some devices have an internal block size bigger than the reported
399 * hardware sector size. This function can be used to signal the
400 * smallest I/O the device can perform without incurring a performance
401 * penalty.
402 */
403void blk_limits_io_min(struct queue_limits *limits, unsigned int min)
404{
405    limits->io_min = min;
406
407    if (limits->io_min < limits->logical_block_size)
408        limits->io_min = limits->logical_block_size;
409
410    if (limits->io_min < limits->physical_block_size)
411        limits->io_min = limits->physical_block_size;
412}
413EXPORT_SYMBOL(blk_limits_io_min);
414
415/**
416 * blk_queue_io_min - set minimum request size for the queue
417 * @q: the request queue for the device
418 * @min: smallest I/O size in bytes
419 *
420 * Description:
421 * Storage devices may report a granularity or preferred minimum I/O
422 * size which is the smallest request the device can perform without
423 * incurring a performance penalty. For disk drives this is often the
424 * physical block size. For RAID arrays it is often the stripe chunk
425 * size. A properly aligned multiple of minimum_io_size is the
426 * preferred request size for workloads where a high number of I/O
427 * operations is desired.
428 */
429void blk_queue_io_min(struct request_queue *q, unsigned int min)
430{
431    blk_limits_io_min(&q->limits, min);
432}
433EXPORT_SYMBOL(blk_queue_io_min);
434
435/**
436 * blk_limits_io_opt - set optimal request size for a device
437 * @limits: the queue limits
438 * @opt: smallest I/O size in bytes
439 *
440 * Description:
441 * Storage devices may report an optimal I/O size, which is the
442 * device's preferred unit for sustained I/O. This is rarely reported
443 * for disk drives. For RAID arrays it is usually the stripe width or
444 * the internal track size. A properly aligned multiple of
445 * optimal_io_size is the preferred request size for workloads where
446 * sustained throughput is desired.
447 */
448void blk_limits_io_opt(struct queue_limits *limits, unsigned int opt)
449{
450    limits->io_opt = opt;
451}
452EXPORT_SYMBOL(blk_limits_io_opt);
453
454/**
455 * blk_queue_io_opt - set optimal request size for the queue
456 * @q: the request queue for the device
457 * @opt: optimal request size in bytes
458 *
459 * Description:
460 * Storage devices may report an optimal I/O size, which is the
461 * device's preferred unit for sustained I/O. This is rarely reported
462 * for disk drives. For RAID arrays it is usually the stripe width or
463 * the internal track size. A properly aligned multiple of
464 * optimal_io_size is the preferred request size for workloads where
465 * sustained throughput is desired.
466 */
467void blk_queue_io_opt(struct request_queue *q, unsigned int opt)
468{
469    blk_limits_io_opt(&q->limits, opt);
470}
471EXPORT_SYMBOL(blk_queue_io_opt);
472
473/**
474 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
475 * @t: the stacking driver (top)
476 * @b: the underlying device (bottom)
477 **/
478void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b)
479{
480    blk_stack_limits(&t->limits, &b->limits, 0);
481}
482EXPORT_SYMBOL(blk_queue_stack_limits);
483
484/**
485 * blk_stack_limits - adjust queue_limits for stacked devices
486 * @t: the stacking driver limits (top device)
487 * @b: the underlying queue limits (bottom, component device)
488 * @start: first data sector within component device
489 *
490 * Description:
491 * This function is used by stacking drivers like MD and DM to ensure
492 * that all component devices have compatible block sizes and
493 * alignments. The stacking driver must provide a queue_limits
494 * struct (top) and then iteratively call the stacking function for
495 * all component (bottom) devices. The stacking function will
496 * attempt to combine the values and ensure proper alignment.
497 *
498 * Returns 0 if the top and bottom queue_limits are compatible. The
499 * top device's block sizes and alignment offsets may be adjusted to
500 * ensure alignment with the bottom device. If no compatible sizes
501 * and alignments exist, -1 is returned and the resulting top
502 * queue_limits will have the misaligned flag set to indicate that
503 * the alignment_offset is undefined.
504 */
505int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
506             sector_t start)
507{
508    unsigned int top, bottom, alignment, ret = 0;
509
510    t->max_sectors = min_not_zero(t->max_sectors, b->max_sectors);
511    t->max_hw_sectors = min_not_zero(t->max_hw_sectors, b->max_hw_sectors);
512    t->bounce_pfn = min_not_zero(t->bounce_pfn, b->bounce_pfn);
513
514    t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
515                        b->seg_boundary_mask);
516
517    t->max_segments = min_not_zero(t->max_segments, b->max_segments);
518    t->max_integrity_segments = min_not_zero(t->max_integrity_segments,
519                         b->max_integrity_segments);
520
521    t->max_segment_size = min_not_zero(t->max_segment_size,
522                       b->max_segment_size);
523
524    t->misaligned |= b->misaligned;
525
526    alignment = queue_limit_alignment_offset(b, start);
527
528    /* Bottom device has different alignment. Check that it is
529     * compatible with the current top alignment.
530     */
531    if (t->alignment_offset != alignment) {
532
533        top = max(t->physical_block_size, t->io_min)
534            + t->alignment_offset;
535        bottom = max(b->physical_block_size, b->io_min) + alignment;
536
537        /* Verify that top and bottom intervals line up */
538        if (max(top, bottom) & (min(top, bottom) - 1)) {
539            t->misaligned = 1;
540            ret = -1;
541        }
542    }
543
544    t->logical_block_size = max(t->logical_block_size,
545                    b->logical_block_size);
546
547    t->physical_block_size = max(t->physical_block_size,
548                     b->physical_block_size);
549
550    t->io_min = max(t->io_min, b->io_min);
551    t->io_opt = lcm(t->io_opt, b->io_opt);
552
553    t->cluster &= b->cluster;
554    t->discard_zeroes_data &= b->discard_zeroes_data;
555
556    /* Physical block size a multiple of the logical block size? */
557    if (t->physical_block_size & (t->logical_block_size - 1)) {
558        t->physical_block_size = t->logical_block_size;
559        t->misaligned = 1;
560        ret = -1;
561    }
562
563    /* Minimum I/O a multiple of the physical block size? */
564    if (t->io_min & (t->physical_block_size - 1)) {
565        t->io_min = t->physical_block_size;
566        t->misaligned = 1;
567        ret = -1;
568    }
569
570    /* Optimal I/O a multiple of the physical block size? */
571    if (t->io_opt & (t->physical_block_size - 1)) {
572        t->io_opt = 0;
573        t->misaligned = 1;
574        ret = -1;
575    }
576
577    /* Find lowest common alignment_offset */
578    t->alignment_offset = lcm(t->alignment_offset, alignment)
579        & (max(t->physical_block_size, t->io_min) - 1);
580
581    /* Verify that new alignment_offset is on a logical block boundary */
582    if (t->alignment_offset & (t->logical_block_size - 1)) {
583        t->misaligned = 1;
584        ret = -1;
585    }
586
587    /* Discard alignment and granularity */
588    if (b->discard_granularity) {
589        alignment = queue_limit_discard_alignment(b, start);
590
591        if (t->discard_granularity != 0 &&
592            t->discard_alignment != alignment) {
593            top = t->discard_granularity + t->discard_alignment;
594            bottom = b->discard_granularity + alignment;
595
596            /* Verify that top and bottom intervals line up */
597            if (max(top, bottom) & (min(top, bottom) - 1))
598                t->discard_misaligned = 1;
599        }
600
601        t->max_discard_sectors = min_not_zero(t->max_discard_sectors,
602                              b->max_discard_sectors);
603        t->discard_granularity = max(t->discard_granularity,
604                         b->discard_granularity);
605        t->discard_alignment = lcm(t->discard_alignment, alignment) &
606            (t->discard_granularity - 1);
607    }
608
609    return ret;
610}
611EXPORT_SYMBOL(blk_stack_limits);
612
613/**
614 * bdev_stack_limits - adjust queue limits for stacked drivers
615 * @t: the stacking driver limits (top device)
616 * @bdev: the component block_device (bottom)
617 * @start: first data sector within component device
618 *
619 * Description:
620 * Merges queue limits for a top device and a block_device. Returns
621 * 0 if alignment didn't change. Returns -1 if adding the bottom
622 * device caused misalignment.
623 */
624int bdev_stack_limits(struct queue_limits *t, struct block_device *bdev,
625              sector_t start)
626{
627    struct request_queue *bq = bdev_get_queue(bdev);
628
629    start += get_start_sect(bdev);
630
631    return blk_stack_limits(t, &bq->limits, start);
632}
633EXPORT_SYMBOL(bdev_stack_limits);
634
635/**
636 * disk_stack_limits - adjust queue limits for stacked drivers
637 * @disk: MD/DM gendisk (top)
638 * @bdev: the underlying block device (bottom)
639 * @offset: offset to beginning of data within component device
640 *
641 * Description:
642 * Merges the limits for a top level gendisk and a bottom level
643 * block_device.
644 */
645void disk_stack_limits(struct gendisk *disk, struct block_device *bdev,
646               sector_t offset)
647{
648    struct request_queue *t = disk->queue;
649
650    if (bdev_stack_limits(&t->limits, bdev, offset >> 9) < 0) {
651        char top[BDEVNAME_SIZE], bottom[BDEVNAME_SIZE];
652
653        disk_name(disk, 0, top);
654        bdevname(bdev, bottom);
655
656        printk(KERN_NOTICE "%s: Warning: Device %s is misaligned\n",
657               top, bottom);
658    }
659}
660EXPORT_SYMBOL(disk_stack_limits);
661
662/**
663 * blk_queue_dma_pad - set pad mask
664 * @q: the request queue for the device
665 * @mask: pad mask
666 *
667 * Set dma pad mask.
668 *
669 * Appending pad buffer to a request modifies the last entry of a
670 * scatter list such that it includes the pad buffer.
671 **/
672void blk_queue_dma_pad(struct request_queue *q, unsigned int mask)
673{
674    q->dma_pad_mask = mask;
675}
676EXPORT_SYMBOL(blk_queue_dma_pad);
677
678/**
679 * blk_queue_update_dma_pad - update pad mask
680 * @q: the request queue for the device
681 * @mask: pad mask
682 *
683 * Update dma pad mask.
684 *
685 * Appending pad buffer to a request modifies the last entry of a
686 * scatter list such that it includes the pad buffer.
687 **/
688void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask)
689{
690    if (mask > q->dma_pad_mask)
691        q->dma_pad_mask = mask;
692}
693EXPORT_SYMBOL(blk_queue_update_dma_pad);
694
695/**
696 * blk_queue_dma_drain - Set up a drain buffer for excess dma.
697 * @q: the request queue for the device
698 * @dma_drain_needed: fn which returns non-zero if drain is necessary
699 * @buf: physically contiguous buffer
700 * @size: size of the buffer in bytes
701 *
702 * Some devices have excess DMA problems and can't simply discard (or
703 * zero fill) the unwanted piece of the transfer. They have to have a
704 * real area of memory to transfer it into. The use case for this is
705 * ATAPI devices in DMA mode. If the packet command causes a transfer
706 * bigger than the transfer size some HBAs will lock up if there
707 * aren't DMA elements to contain the excess transfer. What this API
708 * does is adjust the queue so that the buf is always appended
709 * silently to the scatterlist.
710 *
711 * Note: This routine adjusts max_hw_segments to make room for appending
712 * the drain buffer. If you call blk_queue_max_segments() after calling
713 * this routine, you must set the limit to one fewer than your device
714 * can support otherwise there won't be room for the drain buffer.
715 */
716int blk_queue_dma_drain(struct request_queue *q,
717                   dma_drain_needed_fn *dma_drain_needed,
718                   void *buf, unsigned int size)
719{
720    if (queue_max_segments(q) < 2)
721        return -EINVAL;
722    /* make room for appending the drain */
723    blk_queue_max_segments(q, queue_max_segments(q) - 1);
724    q->dma_drain_needed = dma_drain_needed;
725    q->dma_drain_buffer = buf;
726    q->dma_drain_size = size;
727
728    return 0;
729}
730EXPORT_SYMBOL_GPL(blk_queue_dma_drain);
731
732/**
733 * blk_queue_segment_boundary - set boundary rules for segment merging
734 * @q: the request queue for the device
735 * @mask: the memory boundary mask
736 **/
737void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask)
738{
739    if (mask < PAGE_CACHE_SIZE - 1) {
740        mask = PAGE_CACHE_SIZE - 1;
741        printk(KERN_INFO "%s: set to minimum %lx\n",
742               __func__, mask);
743    }
744
745    q->limits.seg_boundary_mask = mask;
746}
747EXPORT_SYMBOL(blk_queue_segment_boundary);
748
749/**
750 * blk_queue_dma_alignment - set dma length and memory alignment
751 * @q: the request queue for the device
752 * @mask: alignment mask
753 *
754 * description:
755 * set required memory and length alignment for direct dma transactions.
756 * this is used when building direct io requests for the queue.
757 *
758 **/
759void blk_queue_dma_alignment(struct request_queue *q, int mask)
760{
761    q->dma_alignment = mask;
762}
763EXPORT_SYMBOL(blk_queue_dma_alignment);
764
765/**
766 * blk_queue_update_dma_alignment - update dma length and memory alignment
767 * @q: the request queue for the device
768 * @mask: alignment mask
769 *
770 * description:
771 * update required memory and length alignment for direct dma transactions.
772 * If the requested alignment is larger than the current alignment, then
773 * the current queue alignment is updated to the new value, otherwise it
774 * is left alone. The design of this is to allow multiple objects
775 * (driver, device, transport etc) to set their respective
776 * alignments without having them interfere.
777 *
778 **/
779void blk_queue_update_dma_alignment(struct request_queue *q, int mask)
780{
781    BUG_ON(mask > PAGE_SIZE);
782
783    if (mask > q->dma_alignment)
784        q->dma_alignment = mask;
785}
786EXPORT_SYMBOL(blk_queue_update_dma_alignment);
787
788/**
789 * blk_queue_flush - configure queue's cache flush capability
790 * @q: the request queue for the device
791 * @flush: 0, REQ_FLUSH or REQ_FLUSH | REQ_FUA
792 *
793 * Tell block layer cache flush capability of @q. If it supports
794 * flushing, REQ_FLUSH should be set. If it supports bypassing
795 * write cache for individual writes, REQ_FUA should be set.
796 */
797void blk_queue_flush(struct request_queue *q, unsigned int flush)
798{
799    WARN_ON_ONCE(flush & ~(REQ_FLUSH | REQ_FUA));
800
801    if (WARN_ON_ONCE(!(flush & REQ_FLUSH) && (flush & REQ_FUA)))
802        flush &= ~REQ_FUA;
803
804    q->flush_flags = flush & (REQ_FLUSH | REQ_FUA);
805}
806EXPORT_SYMBOL_GPL(blk_queue_flush);
807
808static int __init blk_settings_init(void)
809{
810    blk_max_low_pfn = max_low_pfn - 1;
811    blk_max_pfn = max_pfn - 1;
812    return 0;
813}
814subsys_initcall(blk_settings_init);
815

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