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

Archive Download this file



interactive