Linux 2.6.17-rc6
[linux-2.6/next.git] / block / ll_rw_blk.c
blob7eb36c53f4b7868247141a105ef82e8be3e2d96f
1 /*
2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
4 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> - July2000
7 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
8 */
11 * This handles all read/write requests to block devices
13 #include <linux/config.h>
14 #include <linux/kernel.h>
15 #include <linux/module.h>
16 #include <linux/backing-dev.h>
17 #include <linux/bio.h>
18 #include <linux/blkdev.h>
19 #include <linux/highmem.h>
20 #include <linux/mm.h>
21 #include <linux/kernel_stat.h>
22 #include <linux/string.h>
23 #include <linux/init.h>
24 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
25 #include <linux/completion.h>
26 #include <linux/slab.h>
27 #include <linux/swap.h>
28 #include <linux/writeback.h>
29 #include <linux/interrupt.h>
30 #include <linux/cpu.h>
31 #include <linux/blktrace_api.h>
34 * for max sense size
36 #include <scsi/scsi_cmnd.h>
38 static void blk_unplug_work(void *data);
39 static void blk_unplug_timeout(unsigned long data);
40 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io);
41 static void init_request_from_bio(struct request *req, struct bio *bio);
42 static int __make_request(request_queue_t *q, struct bio *bio);
45 * For the allocated request tables
47 static kmem_cache_t *request_cachep;
50 * For queue allocation
52 static kmem_cache_t *requestq_cachep;
55 * For io context allocations
57 static kmem_cache_t *iocontext_cachep;
59 static wait_queue_head_t congestion_wqh[2] = {
60 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
61 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
65 * Controlling structure to kblockd
67 static struct workqueue_struct *kblockd_workqueue;
69 unsigned long blk_max_low_pfn, blk_max_pfn;
71 EXPORT_SYMBOL(blk_max_low_pfn);
72 EXPORT_SYMBOL(blk_max_pfn);
74 static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
76 /* Amount of time in which a process may batch requests */
77 #define BLK_BATCH_TIME (HZ/50UL)
79 /* Number of requests a "batching" process may submit */
80 #define BLK_BATCH_REQ 32
83 * Return the threshold (number of used requests) at which the queue is
84 * considered to be congested. It include a little hysteresis to keep the
85 * context switch rate down.
87 static inline int queue_congestion_on_threshold(struct request_queue *q)
89 return q->nr_congestion_on;
93 * The threshold at which a queue is considered to be uncongested
95 static inline int queue_congestion_off_threshold(struct request_queue *q)
97 return q->nr_congestion_off;
100 static void blk_queue_congestion_threshold(struct request_queue *q)
102 int nr;
104 nr = q->nr_requests - (q->nr_requests / 8) + 1;
105 if (nr > q->nr_requests)
106 nr = q->nr_requests;
107 q->nr_congestion_on = nr;
109 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
110 if (nr < 1)
111 nr = 1;
112 q->nr_congestion_off = nr;
116 * A queue has just exitted congestion. Note this in the global counter of
117 * congested queues, and wake up anyone who was waiting for requests to be
118 * put back.
120 static void clear_queue_congested(request_queue_t *q, int rw)
122 enum bdi_state bit;
123 wait_queue_head_t *wqh = &congestion_wqh[rw];
125 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
126 clear_bit(bit, &q->backing_dev_info.state);
127 smp_mb__after_clear_bit();
128 if (waitqueue_active(wqh))
129 wake_up(wqh);
133 * A queue has just entered congestion. Flag that in the queue's VM-visible
134 * state flags and increment the global gounter of congested queues.
136 static void set_queue_congested(request_queue_t *q, int rw)
138 enum bdi_state bit;
140 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
141 set_bit(bit, &q->backing_dev_info.state);
145 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
146 * @bdev: device
148 * Locates the passed device's request queue and returns the address of its
149 * backing_dev_info
151 * Will return NULL if the request queue cannot be located.
153 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
155 struct backing_dev_info *ret = NULL;
156 request_queue_t *q = bdev_get_queue(bdev);
158 if (q)
159 ret = &q->backing_dev_info;
160 return ret;
163 EXPORT_SYMBOL(blk_get_backing_dev_info);
165 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
167 q->activity_fn = fn;
168 q->activity_data = data;
171 EXPORT_SYMBOL(blk_queue_activity_fn);
174 * blk_queue_prep_rq - set a prepare_request function for queue
175 * @q: queue
176 * @pfn: prepare_request function
178 * It's possible for a queue to register a prepare_request callback which
179 * is invoked before the request is handed to the request_fn. The goal of
180 * the function is to prepare a request for I/O, it can be used to build a
181 * cdb from the request data for instance.
184 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
186 q->prep_rq_fn = pfn;
189 EXPORT_SYMBOL(blk_queue_prep_rq);
192 * blk_queue_merge_bvec - set a merge_bvec function for queue
193 * @q: queue
194 * @mbfn: merge_bvec_fn
196 * Usually queues have static limitations on the max sectors or segments that
197 * we can put in a request. Stacking drivers may have some settings that
198 * are dynamic, and thus we have to query the queue whether it is ok to
199 * add a new bio_vec to a bio at a given offset or not. If the block device
200 * has such limitations, it needs to register a merge_bvec_fn to control
201 * the size of bio's sent to it. Note that a block device *must* allow a
202 * single page to be added to an empty bio. The block device driver may want
203 * to use the bio_split() function to deal with these bio's. By default
204 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
205 * honored.
207 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
209 q->merge_bvec_fn = mbfn;
212 EXPORT_SYMBOL(blk_queue_merge_bvec);
214 void blk_queue_softirq_done(request_queue_t *q, softirq_done_fn *fn)
216 q->softirq_done_fn = fn;
219 EXPORT_SYMBOL(blk_queue_softirq_done);
222 * blk_queue_make_request - define an alternate make_request function for a device
223 * @q: the request queue for the device to be affected
224 * @mfn: the alternate make_request function
226 * Description:
227 * The normal way for &struct bios to be passed to a device
228 * driver is for them to be collected into requests on a request
229 * queue, and then to allow the device driver to select requests
230 * off that queue when it is ready. This works well for many block
231 * devices. However some block devices (typically virtual devices
232 * such as md or lvm) do not benefit from the processing on the
233 * request queue, and are served best by having the requests passed
234 * directly to them. This can be achieved by providing a function
235 * to blk_queue_make_request().
237 * Caveat:
238 * The driver that does this *must* be able to deal appropriately
239 * with buffers in "highmemory". This can be accomplished by either calling
240 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
241 * blk_queue_bounce() to create a buffer in normal memory.
243 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
246 * set defaults
248 q->nr_requests = BLKDEV_MAX_RQ;
249 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
250 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
251 q->make_request_fn = mfn;
252 q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
253 q->backing_dev_info.state = 0;
254 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
255 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
256 blk_queue_hardsect_size(q, 512);
257 blk_queue_dma_alignment(q, 511);
258 blk_queue_congestion_threshold(q);
259 q->nr_batching = BLK_BATCH_REQ;
261 q->unplug_thresh = 4; /* hmm */
262 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
263 if (q->unplug_delay == 0)
264 q->unplug_delay = 1;
266 INIT_WORK(&q->unplug_work, blk_unplug_work, q);
268 q->unplug_timer.function = blk_unplug_timeout;
269 q->unplug_timer.data = (unsigned long)q;
272 * by default assume old behaviour and bounce for any highmem page
274 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
276 blk_queue_activity_fn(q, NULL, NULL);
279 EXPORT_SYMBOL(blk_queue_make_request);
281 static inline void rq_init(request_queue_t *q, struct request *rq)
283 INIT_LIST_HEAD(&rq->queuelist);
284 INIT_LIST_HEAD(&rq->donelist);
286 rq->errors = 0;
287 rq->rq_status = RQ_ACTIVE;
288 rq->bio = rq->biotail = NULL;
289 rq->ioprio = 0;
290 rq->buffer = NULL;
291 rq->ref_count = 1;
292 rq->q = q;
293 rq->waiting = NULL;
294 rq->special = NULL;
295 rq->data_len = 0;
296 rq->data = NULL;
297 rq->nr_phys_segments = 0;
298 rq->sense = NULL;
299 rq->end_io = NULL;
300 rq->end_io_data = NULL;
301 rq->completion_data = NULL;
305 * blk_queue_ordered - does this queue support ordered writes
306 * @q: the request queue
307 * @ordered: one of QUEUE_ORDERED_*
308 * @prepare_flush_fn: rq setup helper for cache flush ordered writes
310 * Description:
311 * For journalled file systems, doing ordered writes on a commit
312 * block instead of explicitly doing wait_on_buffer (which is bad
313 * for performance) can be a big win. Block drivers supporting this
314 * feature should call this function and indicate so.
317 int blk_queue_ordered(request_queue_t *q, unsigned ordered,
318 prepare_flush_fn *prepare_flush_fn)
320 if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
321 prepare_flush_fn == NULL) {
322 printk(KERN_ERR "blk_queue_ordered: prepare_flush_fn required\n");
323 return -EINVAL;
326 if (ordered != QUEUE_ORDERED_NONE &&
327 ordered != QUEUE_ORDERED_DRAIN &&
328 ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
329 ordered != QUEUE_ORDERED_DRAIN_FUA &&
330 ordered != QUEUE_ORDERED_TAG &&
331 ordered != QUEUE_ORDERED_TAG_FLUSH &&
332 ordered != QUEUE_ORDERED_TAG_FUA) {
333 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
334 return -EINVAL;
337 q->ordered = ordered;
338 q->next_ordered = ordered;
339 q->prepare_flush_fn = prepare_flush_fn;
341 return 0;
344 EXPORT_SYMBOL(blk_queue_ordered);
347 * blk_queue_issue_flush_fn - set function for issuing a flush
348 * @q: the request queue
349 * @iff: the function to be called issuing the flush
351 * Description:
352 * If a driver supports issuing a flush command, the support is notified
353 * to the block layer by defining it through this call.
356 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
358 q->issue_flush_fn = iff;
361 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
364 * Cache flushing for ordered writes handling
366 inline unsigned blk_ordered_cur_seq(request_queue_t *q)
368 if (!q->ordseq)
369 return 0;
370 return 1 << ffz(q->ordseq);
373 unsigned blk_ordered_req_seq(struct request *rq)
375 request_queue_t *q = rq->q;
377 BUG_ON(q->ordseq == 0);
379 if (rq == &q->pre_flush_rq)
380 return QUEUE_ORDSEQ_PREFLUSH;
381 if (rq == &q->bar_rq)
382 return QUEUE_ORDSEQ_BAR;
383 if (rq == &q->post_flush_rq)
384 return QUEUE_ORDSEQ_POSTFLUSH;
386 if ((rq->flags & REQ_ORDERED_COLOR) ==
387 (q->orig_bar_rq->flags & REQ_ORDERED_COLOR))
388 return QUEUE_ORDSEQ_DRAIN;
389 else
390 return QUEUE_ORDSEQ_DONE;
393 void blk_ordered_complete_seq(request_queue_t *q, unsigned seq, int error)
395 struct request *rq;
396 int uptodate;
398 if (error && !q->orderr)
399 q->orderr = error;
401 BUG_ON(q->ordseq & seq);
402 q->ordseq |= seq;
404 if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
405 return;
408 * Okay, sequence complete.
410 rq = q->orig_bar_rq;
411 uptodate = q->orderr ? q->orderr : 1;
413 q->ordseq = 0;
415 end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
416 end_that_request_last(rq, uptodate);
419 static void pre_flush_end_io(struct request *rq, int error)
421 elv_completed_request(rq->q, rq);
422 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
425 static void bar_end_io(struct request *rq, int error)
427 elv_completed_request(rq->q, rq);
428 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
431 static void post_flush_end_io(struct request *rq, int error)
433 elv_completed_request(rq->q, rq);
434 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
437 static void queue_flush(request_queue_t *q, unsigned which)
439 struct request *rq;
440 rq_end_io_fn *end_io;
442 if (which == QUEUE_ORDERED_PREFLUSH) {
443 rq = &q->pre_flush_rq;
444 end_io = pre_flush_end_io;
445 } else {
446 rq = &q->post_flush_rq;
447 end_io = post_flush_end_io;
450 rq_init(q, rq);
451 rq->flags = REQ_HARDBARRIER;
452 rq->elevator_private = NULL;
453 rq->rq_disk = q->bar_rq.rq_disk;
454 rq->rl = NULL;
455 rq->end_io = end_io;
456 q->prepare_flush_fn(q, rq);
458 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
461 static inline struct request *start_ordered(request_queue_t *q,
462 struct request *rq)
464 q->bi_size = 0;
465 q->orderr = 0;
466 q->ordered = q->next_ordered;
467 q->ordseq |= QUEUE_ORDSEQ_STARTED;
470 * Prep proxy barrier request.
472 blkdev_dequeue_request(rq);
473 q->orig_bar_rq = rq;
474 rq = &q->bar_rq;
475 rq_init(q, rq);
476 rq->flags = bio_data_dir(q->orig_bar_rq->bio);
477 rq->flags |= q->ordered & QUEUE_ORDERED_FUA ? REQ_FUA : 0;
478 rq->elevator_private = NULL;
479 rq->rl = NULL;
480 init_request_from_bio(rq, q->orig_bar_rq->bio);
481 rq->end_io = bar_end_io;
484 * Queue ordered sequence. As we stack them at the head, we
485 * need to queue in reverse order. Note that we rely on that
486 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
487 * request gets inbetween ordered sequence.
489 if (q->ordered & QUEUE_ORDERED_POSTFLUSH)
490 queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
491 else
492 q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
494 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
496 if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
497 queue_flush(q, QUEUE_ORDERED_PREFLUSH);
498 rq = &q->pre_flush_rq;
499 } else
500 q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
502 if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
503 q->ordseq |= QUEUE_ORDSEQ_DRAIN;
504 else
505 rq = NULL;
507 return rq;
510 int blk_do_ordered(request_queue_t *q, struct request **rqp)
512 struct request *rq = *rqp;
513 int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
515 if (!q->ordseq) {
516 if (!is_barrier)
517 return 1;
519 if (q->next_ordered != QUEUE_ORDERED_NONE) {
520 *rqp = start_ordered(q, rq);
521 return 1;
522 } else {
524 * This can happen when the queue switches to
525 * ORDERED_NONE while this request is on it.
527 blkdev_dequeue_request(rq);
528 end_that_request_first(rq, -EOPNOTSUPP,
529 rq->hard_nr_sectors);
530 end_that_request_last(rq, -EOPNOTSUPP);
531 *rqp = NULL;
532 return 0;
537 * Ordered sequence in progress
540 /* Special requests are not subject to ordering rules. */
541 if (!blk_fs_request(rq) &&
542 rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
543 return 1;
545 if (q->ordered & QUEUE_ORDERED_TAG) {
546 /* Ordered by tag. Blocking the next barrier is enough. */
547 if (is_barrier && rq != &q->bar_rq)
548 *rqp = NULL;
549 } else {
550 /* Ordered by draining. Wait for turn. */
551 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
552 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
553 *rqp = NULL;
556 return 1;
559 static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
561 request_queue_t *q = bio->bi_private;
562 struct bio_vec *bvec;
563 int i;
566 * This is dry run, restore bio_sector and size. We'll finish
567 * this request again with the original bi_end_io after an
568 * error occurs or post flush is complete.
570 q->bi_size += bytes;
572 if (bio->bi_size)
573 return 1;
575 /* Rewind bvec's */
576 bio->bi_idx = 0;
577 bio_for_each_segment(bvec, bio, i) {
578 bvec->bv_len += bvec->bv_offset;
579 bvec->bv_offset = 0;
582 /* Reset bio */
583 set_bit(BIO_UPTODATE, &bio->bi_flags);
584 bio->bi_size = q->bi_size;
585 bio->bi_sector -= (q->bi_size >> 9);
586 q->bi_size = 0;
588 return 0;
591 static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
592 unsigned int nbytes, int error)
594 request_queue_t *q = rq->q;
595 bio_end_io_t *endio;
596 void *private;
598 if (&q->bar_rq != rq)
599 return 0;
602 * Okay, this is the barrier request in progress, dry finish it.
604 if (error && !q->orderr)
605 q->orderr = error;
607 endio = bio->bi_end_io;
608 private = bio->bi_private;
609 bio->bi_end_io = flush_dry_bio_endio;
610 bio->bi_private = q;
612 bio_endio(bio, nbytes, error);
614 bio->bi_end_io = endio;
615 bio->bi_private = private;
617 return 1;
621 * blk_queue_bounce_limit - set bounce buffer limit for queue
622 * @q: the request queue for the device
623 * @dma_addr: bus address limit
625 * Description:
626 * Different hardware can have different requirements as to what pages
627 * it can do I/O directly to. A low level driver can call
628 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
629 * buffers for doing I/O to pages residing above @page.
631 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
633 unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
634 int dma = 0;
636 q->bounce_gfp = GFP_NOIO;
637 #if BITS_PER_LONG == 64
638 /* Assume anything <= 4GB can be handled by IOMMU.
639 Actually some IOMMUs can handle everything, but I don't
640 know of a way to test this here. */
641 if (bounce_pfn < (0xffffffff>>PAGE_SHIFT))
642 dma = 1;
643 q->bounce_pfn = max_low_pfn;
644 #else
645 if (bounce_pfn < blk_max_low_pfn)
646 dma = 1;
647 q->bounce_pfn = bounce_pfn;
648 #endif
649 if (dma) {
650 init_emergency_isa_pool();
651 q->bounce_gfp = GFP_NOIO | GFP_DMA;
652 q->bounce_pfn = bounce_pfn;
656 EXPORT_SYMBOL(blk_queue_bounce_limit);
659 * blk_queue_max_sectors - set max sectors for a request for this queue
660 * @q: the request queue for the device
661 * @max_sectors: max sectors in the usual 512b unit
663 * Description:
664 * Enables a low level driver to set an upper limit on the size of
665 * received requests.
667 void blk_queue_max_sectors(request_queue_t *q, unsigned int max_sectors)
669 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
670 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
671 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
674 if (BLK_DEF_MAX_SECTORS > max_sectors)
675 q->max_hw_sectors = q->max_sectors = max_sectors;
676 else {
677 q->max_sectors = BLK_DEF_MAX_SECTORS;
678 q->max_hw_sectors = max_sectors;
682 EXPORT_SYMBOL(blk_queue_max_sectors);
685 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
686 * @q: the request queue for the device
687 * @max_segments: max number of segments
689 * Description:
690 * Enables a low level driver to set an upper limit on the number of
691 * physical data segments in a request. This would be the largest sized
692 * scatter list the driver could handle.
694 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
696 if (!max_segments) {
697 max_segments = 1;
698 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
701 q->max_phys_segments = max_segments;
704 EXPORT_SYMBOL(blk_queue_max_phys_segments);
707 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
708 * @q: the request queue for the device
709 * @max_segments: max number of segments
711 * Description:
712 * Enables a low level driver to set an upper limit on the number of
713 * hw data segments in a request. This would be the largest number of
714 * address/length pairs the host adapter can actually give as once
715 * to the device.
717 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
719 if (!max_segments) {
720 max_segments = 1;
721 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
724 q->max_hw_segments = max_segments;
727 EXPORT_SYMBOL(blk_queue_max_hw_segments);
730 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
731 * @q: the request queue for the device
732 * @max_size: max size of segment in bytes
734 * Description:
735 * Enables a low level driver to set an upper limit on the size of a
736 * coalesced segment
738 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
740 if (max_size < PAGE_CACHE_SIZE) {
741 max_size = PAGE_CACHE_SIZE;
742 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
745 q->max_segment_size = max_size;
748 EXPORT_SYMBOL(blk_queue_max_segment_size);
751 * blk_queue_hardsect_size - set hardware sector size for the queue
752 * @q: the request queue for the device
753 * @size: the hardware sector size, in bytes
755 * Description:
756 * This should typically be set to the lowest possible sector size
757 * that the hardware can operate on (possible without reverting to
758 * even internal read-modify-write operations). Usually the default
759 * of 512 covers most hardware.
761 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
763 q->hardsect_size = size;
766 EXPORT_SYMBOL(blk_queue_hardsect_size);
769 * Returns the minimum that is _not_ zero, unless both are zero.
771 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
774 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
775 * @t: the stacking driver (top)
776 * @b: the underlying device (bottom)
778 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
780 /* zero is "infinity" */
781 t->max_sectors = min_not_zero(t->max_sectors,b->max_sectors);
782 t->max_hw_sectors = min_not_zero(t->max_hw_sectors,b->max_hw_sectors);
784 t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
785 t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
786 t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
787 t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
788 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
789 clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags);
792 EXPORT_SYMBOL(blk_queue_stack_limits);
795 * blk_queue_segment_boundary - set boundary rules for segment merging
796 * @q: the request queue for the device
797 * @mask: the memory boundary mask
799 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
801 if (mask < PAGE_CACHE_SIZE - 1) {
802 mask = PAGE_CACHE_SIZE - 1;
803 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
806 q->seg_boundary_mask = mask;
809 EXPORT_SYMBOL(blk_queue_segment_boundary);
812 * blk_queue_dma_alignment - set dma length and memory alignment
813 * @q: the request queue for the device
814 * @mask: alignment mask
816 * description:
817 * set required memory and length aligment for direct dma transactions.
818 * this is used when buiding direct io requests for the queue.
821 void blk_queue_dma_alignment(request_queue_t *q, int mask)
823 q->dma_alignment = mask;
826 EXPORT_SYMBOL(blk_queue_dma_alignment);
829 * blk_queue_find_tag - find a request by its tag and queue
830 * @q: The request queue for the device
831 * @tag: The tag of the request
833 * Notes:
834 * Should be used when a device returns a tag and you want to match
835 * it with a request.
837 * no locks need be held.
839 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
841 struct blk_queue_tag *bqt = q->queue_tags;
843 if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
844 return NULL;
846 return bqt->tag_index[tag];
849 EXPORT_SYMBOL(blk_queue_find_tag);
852 * __blk_queue_free_tags - release tag maintenance info
853 * @q: the request queue for the device
855 * Notes:
856 * blk_cleanup_queue() will take care of calling this function, if tagging
857 * has been used. So there's no need to call this directly.
859 static void __blk_queue_free_tags(request_queue_t *q)
861 struct blk_queue_tag *bqt = q->queue_tags;
863 if (!bqt)
864 return;
866 if (atomic_dec_and_test(&bqt->refcnt)) {
867 BUG_ON(bqt->busy);
868 BUG_ON(!list_empty(&bqt->busy_list));
870 kfree(bqt->tag_index);
871 bqt->tag_index = NULL;
873 kfree(bqt->tag_map);
874 bqt->tag_map = NULL;
876 kfree(bqt);
879 q->queue_tags = NULL;
880 q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
884 * blk_queue_free_tags - release tag maintenance info
885 * @q: the request queue for the device
887 * Notes:
888 * This is used to disabled tagged queuing to a device, yet leave
889 * queue in function.
891 void blk_queue_free_tags(request_queue_t *q)
893 clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
896 EXPORT_SYMBOL(blk_queue_free_tags);
898 static int
899 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
901 struct request **tag_index;
902 unsigned long *tag_map;
903 int nr_ulongs;
905 if (depth > q->nr_requests * 2) {
906 depth = q->nr_requests * 2;
907 printk(KERN_ERR "%s: adjusted depth to %d\n",
908 __FUNCTION__, depth);
911 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
912 if (!tag_index)
913 goto fail;
915 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
916 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
917 if (!tag_map)
918 goto fail;
920 tags->real_max_depth = depth;
921 tags->max_depth = depth;
922 tags->tag_index = tag_index;
923 tags->tag_map = tag_map;
925 return 0;
926 fail:
927 kfree(tag_index);
928 return -ENOMEM;
932 * blk_queue_init_tags - initialize the queue tag info
933 * @q: the request queue for the device
934 * @depth: the maximum queue depth supported
935 * @tags: the tag to use
937 int blk_queue_init_tags(request_queue_t *q, int depth,
938 struct blk_queue_tag *tags)
940 int rc;
942 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
944 if (!tags && !q->queue_tags) {
945 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
946 if (!tags)
947 goto fail;
949 if (init_tag_map(q, tags, depth))
950 goto fail;
952 INIT_LIST_HEAD(&tags->busy_list);
953 tags->busy = 0;
954 atomic_set(&tags->refcnt, 1);
955 } else if (q->queue_tags) {
956 if ((rc = blk_queue_resize_tags(q, depth)))
957 return rc;
958 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
959 return 0;
960 } else
961 atomic_inc(&tags->refcnt);
964 * assign it, all done
966 q->queue_tags = tags;
967 q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
968 return 0;
969 fail:
970 kfree(tags);
971 return -ENOMEM;
974 EXPORT_SYMBOL(blk_queue_init_tags);
977 * blk_queue_resize_tags - change the queueing depth
978 * @q: the request queue for the device
979 * @new_depth: the new max command queueing depth
981 * Notes:
982 * Must be called with the queue lock held.
984 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
986 struct blk_queue_tag *bqt = q->queue_tags;
987 struct request **tag_index;
988 unsigned long *tag_map;
989 int max_depth, nr_ulongs;
991 if (!bqt)
992 return -ENXIO;
995 * if we already have large enough real_max_depth. just
996 * adjust max_depth. *NOTE* as requests with tag value
997 * between new_depth and real_max_depth can be in-flight, tag
998 * map can not be shrunk blindly here.
1000 if (new_depth <= bqt->real_max_depth) {
1001 bqt->max_depth = new_depth;
1002 return 0;
1006 * save the old state info, so we can copy it back
1008 tag_index = bqt->tag_index;
1009 tag_map = bqt->tag_map;
1010 max_depth = bqt->real_max_depth;
1012 if (init_tag_map(q, bqt, new_depth))
1013 return -ENOMEM;
1015 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
1016 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
1017 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
1019 kfree(tag_index);
1020 kfree(tag_map);
1021 return 0;
1024 EXPORT_SYMBOL(blk_queue_resize_tags);
1027 * blk_queue_end_tag - end tag operations for a request
1028 * @q: the request queue for the device
1029 * @rq: the request that has completed
1031 * Description:
1032 * Typically called when end_that_request_first() returns 0, meaning
1033 * all transfers have been done for a request. It's important to call
1034 * this function before end_that_request_last(), as that will put the
1035 * request back on the free list thus corrupting the internal tag list.
1037 * Notes:
1038 * queue lock must be held.
1040 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
1042 struct blk_queue_tag *bqt = q->queue_tags;
1043 int tag = rq->tag;
1045 BUG_ON(tag == -1);
1047 if (unlikely(tag >= bqt->real_max_depth))
1049 * This can happen after tag depth has been reduced.
1050 * FIXME: how about a warning or info message here?
1052 return;
1054 if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
1055 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
1056 __FUNCTION__, tag);
1057 return;
1060 list_del_init(&rq->queuelist);
1061 rq->flags &= ~REQ_QUEUED;
1062 rq->tag = -1;
1064 if (unlikely(bqt->tag_index[tag] == NULL))
1065 printk(KERN_ERR "%s: tag %d is missing\n",
1066 __FUNCTION__, tag);
1068 bqt->tag_index[tag] = NULL;
1069 bqt->busy--;
1072 EXPORT_SYMBOL(blk_queue_end_tag);
1075 * blk_queue_start_tag - find a free tag and assign it
1076 * @q: the request queue for the device
1077 * @rq: the block request that needs tagging
1079 * Description:
1080 * This can either be used as a stand-alone helper, or possibly be
1081 * assigned as the queue &prep_rq_fn (in which case &struct request
1082 * automagically gets a tag assigned). Note that this function
1083 * assumes that any type of request can be queued! if this is not
1084 * true for your device, you must check the request type before
1085 * calling this function. The request will also be removed from
1086 * the request queue, so it's the drivers responsibility to readd
1087 * it if it should need to be restarted for some reason.
1089 * Notes:
1090 * queue lock must be held.
1092 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
1094 struct blk_queue_tag *bqt = q->queue_tags;
1095 int tag;
1097 if (unlikely((rq->flags & REQ_QUEUED))) {
1098 printk(KERN_ERR
1099 "%s: request %p for device [%s] already tagged %d",
1100 __FUNCTION__, rq,
1101 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
1102 BUG();
1105 tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
1106 if (tag >= bqt->max_depth)
1107 return 1;
1109 __set_bit(tag, bqt->tag_map);
1111 rq->flags |= REQ_QUEUED;
1112 rq->tag = tag;
1113 bqt->tag_index[tag] = rq;
1114 blkdev_dequeue_request(rq);
1115 list_add(&rq->queuelist, &bqt->busy_list);
1116 bqt->busy++;
1117 return 0;
1120 EXPORT_SYMBOL(blk_queue_start_tag);
1123 * blk_queue_invalidate_tags - invalidate all pending tags
1124 * @q: the request queue for the device
1126 * Description:
1127 * Hardware conditions may dictate a need to stop all pending requests.
1128 * In this case, we will safely clear the block side of the tag queue and
1129 * readd all requests to the request queue in the right order.
1131 * Notes:
1132 * queue lock must be held.
1134 void blk_queue_invalidate_tags(request_queue_t *q)
1136 struct blk_queue_tag *bqt = q->queue_tags;
1137 struct list_head *tmp, *n;
1138 struct request *rq;
1140 list_for_each_safe(tmp, n, &bqt->busy_list) {
1141 rq = list_entry_rq(tmp);
1143 if (rq->tag == -1) {
1144 printk(KERN_ERR
1145 "%s: bad tag found on list\n", __FUNCTION__);
1146 list_del_init(&rq->queuelist);
1147 rq->flags &= ~REQ_QUEUED;
1148 } else
1149 blk_queue_end_tag(q, rq);
1151 rq->flags &= ~REQ_STARTED;
1152 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1156 EXPORT_SYMBOL(blk_queue_invalidate_tags);
1158 static const char * const rq_flags[] = {
1159 "REQ_RW",
1160 "REQ_FAILFAST",
1161 "REQ_SORTED",
1162 "REQ_SOFTBARRIER",
1163 "REQ_HARDBARRIER",
1164 "REQ_FUA",
1165 "REQ_CMD",
1166 "REQ_NOMERGE",
1167 "REQ_STARTED",
1168 "REQ_DONTPREP",
1169 "REQ_QUEUED",
1170 "REQ_ELVPRIV",
1171 "REQ_PC",
1172 "REQ_BLOCK_PC",
1173 "REQ_SENSE",
1174 "REQ_FAILED",
1175 "REQ_QUIET",
1176 "REQ_SPECIAL",
1177 "REQ_DRIVE_CMD",
1178 "REQ_DRIVE_TASK",
1179 "REQ_DRIVE_TASKFILE",
1180 "REQ_PREEMPT",
1181 "REQ_PM_SUSPEND",
1182 "REQ_PM_RESUME",
1183 "REQ_PM_SHUTDOWN",
1184 "REQ_ORDERED_COLOR",
1187 void blk_dump_rq_flags(struct request *rq, char *msg)
1189 int bit;
1191 printk("%s: dev %s: flags = ", msg,
1192 rq->rq_disk ? rq->rq_disk->disk_name : "?");
1193 bit = 0;
1194 do {
1195 if (rq->flags & (1 << bit))
1196 printk("%s ", rq_flags[bit]);
1197 bit++;
1198 } while (bit < __REQ_NR_BITS);
1200 printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
1201 rq->nr_sectors,
1202 rq->current_nr_sectors);
1203 printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
1205 if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
1206 printk("cdb: ");
1207 for (bit = 0; bit < sizeof(rq->cmd); bit++)
1208 printk("%02x ", rq->cmd[bit]);
1209 printk("\n");
1213 EXPORT_SYMBOL(blk_dump_rq_flags);
1215 void blk_recount_segments(request_queue_t *q, struct bio *bio)
1217 struct bio_vec *bv, *bvprv = NULL;
1218 int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
1219 int high, highprv = 1;
1221 if (unlikely(!bio->bi_io_vec))
1222 return;
1224 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1225 hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
1226 bio_for_each_segment(bv, bio, i) {
1228 * the trick here is making sure that a high page is never
1229 * considered part of another segment, since that might
1230 * change with the bounce page.
1232 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
1233 if (high || highprv)
1234 goto new_hw_segment;
1235 if (cluster) {
1236 if (seg_size + bv->bv_len > q->max_segment_size)
1237 goto new_segment;
1238 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
1239 goto new_segment;
1240 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
1241 goto new_segment;
1242 if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
1243 goto new_hw_segment;
1245 seg_size += bv->bv_len;
1246 hw_seg_size += bv->bv_len;
1247 bvprv = bv;
1248 continue;
1250 new_segment:
1251 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
1252 !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
1253 hw_seg_size += bv->bv_len;
1254 } else {
1255 new_hw_segment:
1256 if (hw_seg_size > bio->bi_hw_front_size)
1257 bio->bi_hw_front_size = hw_seg_size;
1258 hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
1259 nr_hw_segs++;
1262 nr_phys_segs++;
1263 bvprv = bv;
1264 seg_size = bv->bv_len;
1265 highprv = high;
1267 if (hw_seg_size > bio->bi_hw_back_size)
1268 bio->bi_hw_back_size = hw_seg_size;
1269 if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
1270 bio->bi_hw_front_size = hw_seg_size;
1271 bio->bi_phys_segments = nr_phys_segs;
1272 bio->bi_hw_segments = nr_hw_segs;
1273 bio->bi_flags |= (1 << BIO_SEG_VALID);
1277 static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
1278 struct bio *nxt)
1280 if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
1281 return 0;
1283 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
1284 return 0;
1285 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1286 return 0;
1289 * bio and nxt are contigous in memory, check if the queue allows
1290 * these two to be merged into one
1292 if (BIO_SEG_BOUNDARY(q, bio, nxt))
1293 return 1;
1295 return 0;
1298 static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
1299 struct bio *nxt)
1301 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1302 blk_recount_segments(q, bio);
1303 if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
1304 blk_recount_segments(q, nxt);
1305 if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
1306 BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
1307 return 0;
1308 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1309 return 0;
1311 return 1;
1315 * map a request to scatterlist, return number of sg entries setup. Caller
1316 * must make sure sg can hold rq->nr_phys_segments entries
1318 int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
1320 struct bio_vec *bvec, *bvprv;
1321 struct bio *bio;
1322 int nsegs, i, cluster;
1324 nsegs = 0;
1325 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1328 * for each bio in rq
1330 bvprv = NULL;
1331 rq_for_each_bio(bio, rq) {
1333 * for each segment in bio
1335 bio_for_each_segment(bvec, bio, i) {
1336 int nbytes = bvec->bv_len;
1338 if (bvprv && cluster) {
1339 if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
1340 goto new_segment;
1342 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
1343 goto new_segment;
1344 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
1345 goto new_segment;
1347 sg[nsegs - 1].length += nbytes;
1348 } else {
1349 new_segment:
1350 memset(&sg[nsegs],0,sizeof(struct scatterlist));
1351 sg[nsegs].page = bvec->bv_page;
1352 sg[nsegs].length = nbytes;
1353 sg[nsegs].offset = bvec->bv_offset;
1355 nsegs++;
1357 bvprv = bvec;
1358 } /* segments in bio */
1359 } /* bios in rq */
1361 return nsegs;
1364 EXPORT_SYMBOL(blk_rq_map_sg);
1367 * the standard queue merge functions, can be overridden with device
1368 * specific ones if so desired
1371 static inline int ll_new_mergeable(request_queue_t *q,
1372 struct request *req,
1373 struct bio *bio)
1375 int nr_phys_segs = bio_phys_segments(q, bio);
1377 if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1378 req->flags |= REQ_NOMERGE;
1379 if (req == q->last_merge)
1380 q->last_merge = NULL;
1381 return 0;
1385 * A hw segment is just getting larger, bump just the phys
1386 * counter.
1388 req->nr_phys_segments += nr_phys_segs;
1389 return 1;
1392 static inline int ll_new_hw_segment(request_queue_t *q,
1393 struct request *req,
1394 struct bio *bio)
1396 int nr_hw_segs = bio_hw_segments(q, bio);
1397 int nr_phys_segs = bio_phys_segments(q, bio);
1399 if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
1400 || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1401 req->flags |= REQ_NOMERGE;
1402 if (req == q->last_merge)
1403 q->last_merge = NULL;
1404 return 0;
1408 * This will form the start of a new hw segment. Bump both
1409 * counters.
1411 req->nr_hw_segments += nr_hw_segs;
1412 req->nr_phys_segments += nr_phys_segs;
1413 return 1;
1416 static int ll_back_merge_fn(request_queue_t *q, struct request *req,
1417 struct bio *bio)
1419 unsigned short max_sectors;
1420 int len;
1422 if (unlikely(blk_pc_request(req)))
1423 max_sectors = q->max_hw_sectors;
1424 else
1425 max_sectors = q->max_sectors;
1427 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1428 req->flags |= REQ_NOMERGE;
1429 if (req == q->last_merge)
1430 q->last_merge = NULL;
1431 return 0;
1433 if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
1434 blk_recount_segments(q, req->biotail);
1435 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1436 blk_recount_segments(q, bio);
1437 len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
1438 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
1439 !BIOVEC_VIRT_OVERSIZE(len)) {
1440 int mergeable = ll_new_mergeable(q, req, bio);
1442 if (mergeable) {
1443 if (req->nr_hw_segments == 1)
1444 req->bio->bi_hw_front_size = len;
1445 if (bio->bi_hw_segments == 1)
1446 bio->bi_hw_back_size = len;
1448 return mergeable;
1451 return ll_new_hw_segment(q, req, bio);
1454 static int ll_front_merge_fn(request_queue_t *q, struct request *req,
1455 struct bio *bio)
1457 unsigned short max_sectors;
1458 int len;
1460 if (unlikely(blk_pc_request(req)))
1461 max_sectors = q->max_hw_sectors;
1462 else
1463 max_sectors = q->max_sectors;
1466 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1467 req->flags |= REQ_NOMERGE;
1468 if (req == q->last_merge)
1469 q->last_merge = NULL;
1470 return 0;
1472 len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
1473 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1474 blk_recount_segments(q, bio);
1475 if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
1476 blk_recount_segments(q, req->bio);
1477 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
1478 !BIOVEC_VIRT_OVERSIZE(len)) {
1479 int mergeable = ll_new_mergeable(q, req, bio);
1481 if (mergeable) {
1482 if (bio->bi_hw_segments == 1)
1483 bio->bi_hw_front_size = len;
1484 if (req->nr_hw_segments == 1)
1485 req->biotail->bi_hw_back_size = len;
1487 return mergeable;
1490 return ll_new_hw_segment(q, req, bio);
1493 static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
1494 struct request *next)
1496 int total_phys_segments;
1497 int total_hw_segments;
1500 * First check if the either of the requests are re-queued
1501 * requests. Can't merge them if they are.
1503 if (req->special || next->special)
1504 return 0;
1507 * Will it become too large?
1509 if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
1510 return 0;
1512 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
1513 if (blk_phys_contig_segment(q, req->biotail, next->bio))
1514 total_phys_segments--;
1516 if (total_phys_segments > q->max_phys_segments)
1517 return 0;
1519 total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1520 if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
1521 int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
1523 * propagate the combined length to the end of the requests
1525 if (req->nr_hw_segments == 1)
1526 req->bio->bi_hw_front_size = len;
1527 if (next->nr_hw_segments == 1)
1528 next->biotail->bi_hw_back_size = len;
1529 total_hw_segments--;
1532 if (total_hw_segments > q->max_hw_segments)
1533 return 0;
1535 /* Merge is OK... */
1536 req->nr_phys_segments = total_phys_segments;
1537 req->nr_hw_segments = total_hw_segments;
1538 return 1;
1542 * "plug" the device if there are no outstanding requests: this will
1543 * force the transfer to start only after we have put all the requests
1544 * on the list.
1546 * This is called with interrupts off and no requests on the queue and
1547 * with the queue lock held.
1549 void blk_plug_device(request_queue_t *q)
1551 WARN_ON(!irqs_disabled());
1554 * don't plug a stopped queue, it must be paired with blk_start_queue()
1555 * which will restart the queueing
1557 if (blk_queue_stopped(q))
1558 return;
1560 if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
1561 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
1562 blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
1566 EXPORT_SYMBOL(blk_plug_device);
1569 * remove the queue from the plugged list, if present. called with
1570 * queue lock held and interrupts disabled.
1572 int blk_remove_plug(request_queue_t *q)
1574 WARN_ON(!irqs_disabled());
1576 if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1577 return 0;
1579 del_timer(&q->unplug_timer);
1580 return 1;
1583 EXPORT_SYMBOL(blk_remove_plug);
1586 * remove the plug and let it rip..
1588 void __generic_unplug_device(request_queue_t *q)
1590 if (unlikely(blk_queue_stopped(q)))
1591 return;
1593 if (!blk_remove_plug(q))
1594 return;
1596 q->request_fn(q);
1598 EXPORT_SYMBOL(__generic_unplug_device);
1601 * generic_unplug_device - fire a request queue
1602 * @q: The &request_queue_t in question
1604 * Description:
1605 * Linux uses plugging to build bigger requests queues before letting
1606 * the device have at them. If a queue is plugged, the I/O scheduler
1607 * is still adding and merging requests on the queue. Once the queue
1608 * gets unplugged, the request_fn defined for the queue is invoked and
1609 * transfers started.
1611 void generic_unplug_device(request_queue_t *q)
1613 spin_lock_irq(q->queue_lock);
1614 __generic_unplug_device(q);
1615 spin_unlock_irq(q->queue_lock);
1617 EXPORT_SYMBOL(generic_unplug_device);
1619 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1620 struct page *page)
1622 request_queue_t *q = bdi->unplug_io_data;
1625 * devices don't necessarily have an ->unplug_fn defined
1627 if (q->unplug_fn) {
1628 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1629 q->rq.count[READ] + q->rq.count[WRITE]);
1631 q->unplug_fn(q);
1635 static void blk_unplug_work(void *data)
1637 request_queue_t *q = data;
1639 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1640 q->rq.count[READ] + q->rq.count[WRITE]);
1642 q->unplug_fn(q);
1645 static void blk_unplug_timeout(unsigned long data)
1647 request_queue_t *q = (request_queue_t *)data;
1649 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_TIMER, NULL,
1650 q->rq.count[READ] + q->rq.count[WRITE]);
1652 kblockd_schedule_work(&q->unplug_work);
1656 * blk_start_queue - restart a previously stopped queue
1657 * @q: The &request_queue_t in question
1659 * Description:
1660 * blk_start_queue() will clear the stop flag on the queue, and call
1661 * the request_fn for the queue if it was in a stopped state when
1662 * entered. Also see blk_stop_queue(). Queue lock must be held.
1664 void blk_start_queue(request_queue_t *q)
1666 clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1669 * one level of recursion is ok and is much faster than kicking
1670 * the unplug handling
1672 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1673 q->request_fn(q);
1674 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1675 } else {
1676 blk_plug_device(q);
1677 kblockd_schedule_work(&q->unplug_work);
1681 EXPORT_SYMBOL(blk_start_queue);
1684 * blk_stop_queue - stop a queue
1685 * @q: The &request_queue_t in question
1687 * Description:
1688 * The Linux block layer assumes that a block driver will consume all
1689 * entries on the request queue when the request_fn strategy is called.
1690 * Often this will not happen, because of hardware limitations (queue
1691 * depth settings). If a device driver gets a 'queue full' response,
1692 * or if it simply chooses not to queue more I/O at one point, it can
1693 * call this function to prevent the request_fn from being called until
1694 * the driver has signalled it's ready to go again. This happens by calling
1695 * blk_start_queue() to restart queue operations. Queue lock must be held.
1697 void blk_stop_queue(request_queue_t *q)
1699 blk_remove_plug(q);
1700 set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1702 EXPORT_SYMBOL(blk_stop_queue);
1705 * blk_sync_queue - cancel any pending callbacks on a queue
1706 * @q: the queue
1708 * Description:
1709 * The block layer may perform asynchronous callback activity
1710 * on a queue, such as calling the unplug function after a timeout.
1711 * A block device may call blk_sync_queue to ensure that any
1712 * such activity is cancelled, thus allowing it to release resources
1713 * the the callbacks might use. The caller must already have made sure
1714 * that its ->make_request_fn will not re-add plugging prior to calling
1715 * this function.
1718 void blk_sync_queue(struct request_queue *q)
1720 del_timer_sync(&q->unplug_timer);
1721 kblockd_flush();
1723 EXPORT_SYMBOL(blk_sync_queue);
1726 * blk_run_queue - run a single device queue
1727 * @q: The queue to run
1729 void blk_run_queue(struct request_queue *q)
1731 unsigned long flags;
1733 spin_lock_irqsave(q->queue_lock, flags);
1734 blk_remove_plug(q);
1737 * Only recurse once to avoid overrunning the stack, let the unplug
1738 * handling reinvoke the handler shortly if we already got there.
1740 if (!elv_queue_empty(q)) {
1741 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1742 q->request_fn(q);
1743 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1744 } else {
1745 blk_plug_device(q);
1746 kblockd_schedule_work(&q->unplug_work);
1750 spin_unlock_irqrestore(q->queue_lock, flags);
1752 EXPORT_SYMBOL(blk_run_queue);
1755 * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1756 * @kobj: the kobj belonging of the request queue to be released
1758 * Description:
1759 * blk_cleanup_queue is the pair to blk_init_queue() or
1760 * blk_queue_make_request(). It should be called when a request queue is
1761 * being released; typically when a block device is being de-registered.
1762 * Currently, its primary task it to free all the &struct request
1763 * structures that were allocated to the queue and the queue itself.
1765 * Caveat:
1766 * Hopefully the low level driver will have finished any
1767 * outstanding requests first...
1769 static void blk_release_queue(struct kobject *kobj)
1771 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
1772 struct request_list *rl = &q->rq;
1774 blk_sync_queue(q);
1776 if (rl->rq_pool)
1777 mempool_destroy(rl->rq_pool);
1779 if (q->queue_tags)
1780 __blk_queue_free_tags(q);
1782 if (q->blk_trace)
1783 blk_trace_shutdown(q);
1785 kmem_cache_free(requestq_cachep, q);
1788 void blk_put_queue(request_queue_t *q)
1790 kobject_put(&q->kobj);
1792 EXPORT_SYMBOL(blk_put_queue);
1794 void blk_cleanup_queue(request_queue_t * q)
1796 mutex_lock(&q->sysfs_lock);
1797 set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
1798 mutex_unlock(&q->sysfs_lock);
1800 if (q->elevator)
1801 elevator_exit(q->elevator);
1803 blk_put_queue(q);
1806 EXPORT_SYMBOL(blk_cleanup_queue);
1808 static int blk_init_free_list(request_queue_t *q)
1810 struct request_list *rl = &q->rq;
1812 rl->count[READ] = rl->count[WRITE] = 0;
1813 rl->starved[READ] = rl->starved[WRITE] = 0;
1814 rl->elvpriv = 0;
1815 init_waitqueue_head(&rl->wait[READ]);
1816 init_waitqueue_head(&rl->wait[WRITE]);
1818 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1819 mempool_free_slab, request_cachep, q->node);
1821 if (!rl->rq_pool)
1822 return -ENOMEM;
1824 return 0;
1827 request_queue_t *blk_alloc_queue(gfp_t gfp_mask)
1829 return blk_alloc_queue_node(gfp_mask, -1);
1831 EXPORT_SYMBOL(blk_alloc_queue);
1833 static struct kobj_type queue_ktype;
1835 request_queue_t *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
1837 request_queue_t *q;
1839 q = kmem_cache_alloc_node(requestq_cachep, gfp_mask, node_id);
1840 if (!q)
1841 return NULL;
1843 memset(q, 0, sizeof(*q));
1844 init_timer(&q->unplug_timer);
1846 snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
1847 q->kobj.ktype = &queue_ktype;
1848 kobject_init(&q->kobj);
1850 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1851 q->backing_dev_info.unplug_io_data = q;
1853 mutex_init(&q->sysfs_lock);
1855 return q;
1857 EXPORT_SYMBOL(blk_alloc_queue_node);
1860 * blk_init_queue - prepare a request queue for use with a block device
1861 * @rfn: The function to be called to process requests that have been
1862 * placed on the queue.
1863 * @lock: Request queue spin lock
1865 * Description:
1866 * If a block device wishes to use the standard request handling procedures,
1867 * which sorts requests and coalesces adjacent requests, then it must
1868 * call blk_init_queue(). The function @rfn will be called when there
1869 * are requests on the queue that need to be processed. If the device
1870 * supports plugging, then @rfn may not be called immediately when requests
1871 * are available on the queue, but may be called at some time later instead.
1872 * Plugged queues are generally unplugged when a buffer belonging to one
1873 * of the requests on the queue is needed, or due to memory pressure.
1875 * @rfn is not required, or even expected, to remove all requests off the
1876 * queue, but only as many as it can handle at a time. If it does leave
1877 * requests on the queue, it is responsible for arranging that the requests
1878 * get dealt with eventually.
1880 * The queue spin lock must be held while manipulating the requests on the
1881 * request queue.
1883 * Function returns a pointer to the initialized request queue, or NULL if
1884 * it didn't succeed.
1886 * Note:
1887 * blk_init_queue() must be paired with a blk_cleanup_queue() call
1888 * when the block device is deactivated (such as at module unload).
1891 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1893 return blk_init_queue_node(rfn, lock, -1);
1895 EXPORT_SYMBOL(blk_init_queue);
1897 request_queue_t *
1898 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
1900 request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
1902 if (!q)
1903 return NULL;
1905 q->node = node_id;
1906 if (blk_init_free_list(q)) {
1907 kmem_cache_free(requestq_cachep, q);
1908 return NULL;
1912 * if caller didn't supply a lock, they get per-queue locking with
1913 * our embedded lock
1915 if (!lock) {
1916 spin_lock_init(&q->__queue_lock);
1917 lock = &q->__queue_lock;
1920 q->request_fn = rfn;
1921 q->back_merge_fn = ll_back_merge_fn;
1922 q->front_merge_fn = ll_front_merge_fn;
1923 q->merge_requests_fn = ll_merge_requests_fn;
1924 q->prep_rq_fn = NULL;
1925 q->unplug_fn = generic_unplug_device;
1926 q->queue_flags = (1 << QUEUE_FLAG_CLUSTER);
1927 q->queue_lock = lock;
1929 blk_queue_segment_boundary(q, 0xffffffff);
1931 blk_queue_make_request(q, __make_request);
1932 blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1934 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1935 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1938 * all done
1940 if (!elevator_init(q, NULL)) {
1941 blk_queue_congestion_threshold(q);
1942 return q;
1945 blk_put_queue(q);
1946 return NULL;
1948 EXPORT_SYMBOL(blk_init_queue_node);
1950 int blk_get_queue(request_queue_t *q)
1952 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
1953 kobject_get(&q->kobj);
1954 return 0;
1957 return 1;
1960 EXPORT_SYMBOL(blk_get_queue);
1962 static inline void blk_free_request(request_queue_t *q, struct request *rq)
1964 if (rq->flags & REQ_ELVPRIV)
1965 elv_put_request(q, rq);
1966 mempool_free(rq, q->rq.rq_pool);
1969 static inline struct request *
1970 blk_alloc_request(request_queue_t *q, int rw, struct bio *bio,
1971 int priv, gfp_t gfp_mask)
1973 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
1975 if (!rq)
1976 return NULL;
1979 * first three bits are identical in rq->flags and bio->bi_rw,
1980 * see bio.h and blkdev.h
1982 rq->flags = rw;
1984 if (priv) {
1985 if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
1986 mempool_free(rq, q->rq.rq_pool);
1987 return NULL;
1989 rq->flags |= REQ_ELVPRIV;
1992 return rq;
1996 * ioc_batching returns true if the ioc is a valid batching request and
1997 * should be given priority access to a request.
1999 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
2001 if (!ioc)
2002 return 0;
2005 * Make sure the process is able to allocate at least 1 request
2006 * even if the batch times out, otherwise we could theoretically
2007 * lose wakeups.
2009 return ioc->nr_batch_requests == q->nr_batching ||
2010 (ioc->nr_batch_requests > 0
2011 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
2015 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
2016 * will cause the process to be a "batcher" on all queues in the system. This
2017 * is the behaviour we want though - once it gets a wakeup it should be given
2018 * a nice run.
2020 static void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
2022 if (!ioc || ioc_batching(q, ioc))
2023 return;
2025 ioc->nr_batch_requests = q->nr_batching;
2026 ioc->last_waited = jiffies;
2029 static void __freed_request(request_queue_t *q, int rw)
2031 struct request_list *rl = &q->rq;
2033 if (rl->count[rw] < queue_congestion_off_threshold(q))
2034 clear_queue_congested(q, rw);
2036 if (rl->count[rw] + 1 <= q->nr_requests) {
2037 if (waitqueue_active(&rl->wait[rw]))
2038 wake_up(&rl->wait[rw]);
2040 blk_clear_queue_full(q, rw);
2045 * A request has just been released. Account for it, update the full and
2046 * congestion status, wake up any waiters. Called under q->queue_lock.
2048 static void freed_request(request_queue_t *q, int rw, int priv)
2050 struct request_list *rl = &q->rq;
2052 rl->count[rw]--;
2053 if (priv)
2054 rl->elvpriv--;
2056 __freed_request(q, rw);
2058 if (unlikely(rl->starved[rw ^ 1]))
2059 __freed_request(q, rw ^ 1);
2062 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
2064 * Get a free request, queue_lock must be held.
2065 * Returns NULL on failure, with queue_lock held.
2066 * Returns !NULL on success, with queue_lock *not held*.
2068 static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
2069 gfp_t gfp_mask)
2071 struct request *rq = NULL;
2072 struct request_list *rl = &q->rq;
2073 struct io_context *ioc = NULL;
2074 int may_queue, priv;
2076 may_queue = elv_may_queue(q, rw, bio);
2077 if (may_queue == ELV_MQUEUE_NO)
2078 goto rq_starved;
2080 if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
2081 if (rl->count[rw]+1 >= q->nr_requests) {
2082 ioc = current_io_context(GFP_ATOMIC);
2084 * The queue will fill after this allocation, so set
2085 * it as full, and mark this process as "batching".
2086 * This process will be allowed to complete a batch of
2087 * requests, others will be blocked.
2089 if (!blk_queue_full(q, rw)) {
2090 ioc_set_batching(q, ioc);
2091 blk_set_queue_full(q, rw);
2092 } else {
2093 if (may_queue != ELV_MQUEUE_MUST
2094 && !ioc_batching(q, ioc)) {
2096 * The queue is full and the allocating
2097 * process is not a "batcher", and not
2098 * exempted by the IO scheduler
2100 goto out;
2104 set_queue_congested(q, rw);
2108 * Only allow batching queuers to allocate up to 50% over the defined
2109 * limit of requests, otherwise we could have thousands of requests
2110 * allocated with any setting of ->nr_requests
2112 if (rl->count[rw] >= (3 * q->nr_requests / 2))
2113 goto out;
2115 rl->count[rw]++;
2116 rl->starved[rw] = 0;
2118 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
2119 if (priv)
2120 rl->elvpriv++;
2122 spin_unlock_irq(q->queue_lock);
2124 rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
2125 if (unlikely(!rq)) {
2127 * Allocation failed presumably due to memory. Undo anything
2128 * we might have messed up.
2130 * Allocating task should really be put onto the front of the
2131 * wait queue, but this is pretty rare.
2133 spin_lock_irq(q->queue_lock);
2134 freed_request(q, rw, priv);
2137 * in the very unlikely event that allocation failed and no
2138 * requests for this direction was pending, mark us starved
2139 * so that freeing of a request in the other direction will
2140 * notice us. another possible fix would be to split the
2141 * rq mempool into READ and WRITE
2143 rq_starved:
2144 if (unlikely(rl->count[rw] == 0))
2145 rl->starved[rw] = 1;
2147 goto out;
2151 * ioc may be NULL here, and ioc_batching will be false. That's
2152 * OK, if the queue is under the request limit then requests need
2153 * not count toward the nr_batch_requests limit. There will always
2154 * be some limit enforced by BLK_BATCH_TIME.
2156 if (ioc_batching(q, ioc))
2157 ioc->nr_batch_requests--;
2159 rq_init(q, rq);
2160 rq->rl = rl;
2162 blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ);
2163 out:
2164 return rq;
2168 * No available requests for this queue, unplug the device and wait for some
2169 * requests to become available.
2171 * Called with q->queue_lock held, and returns with it unlocked.
2173 static struct request *get_request_wait(request_queue_t *q, int rw,
2174 struct bio *bio)
2176 struct request *rq;
2178 rq = get_request(q, rw, bio, GFP_NOIO);
2179 while (!rq) {
2180 DEFINE_WAIT(wait);
2181 struct request_list *rl = &q->rq;
2183 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
2184 TASK_UNINTERRUPTIBLE);
2186 rq = get_request(q, rw, bio, GFP_NOIO);
2188 if (!rq) {
2189 struct io_context *ioc;
2191 blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
2193 __generic_unplug_device(q);
2194 spin_unlock_irq(q->queue_lock);
2195 io_schedule();
2198 * After sleeping, we become a "batching" process and
2199 * will be able to allocate at least one request, and
2200 * up to a big batch of them for a small period time.
2201 * See ioc_batching, ioc_set_batching
2203 ioc = current_io_context(GFP_NOIO);
2204 ioc_set_batching(q, ioc);
2206 spin_lock_irq(q->queue_lock);
2208 finish_wait(&rl->wait[rw], &wait);
2211 return rq;
2214 struct request *blk_get_request(request_queue_t *q, int rw, gfp_t gfp_mask)
2216 struct request *rq;
2218 BUG_ON(rw != READ && rw != WRITE);
2220 spin_lock_irq(q->queue_lock);
2221 if (gfp_mask & __GFP_WAIT) {
2222 rq = get_request_wait(q, rw, NULL);
2223 } else {
2224 rq = get_request(q, rw, NULL, gfp_mask);
2225 if (!rq)
2226 spin_unlock_irq(q->queue_lock);
2228 /* q->queue_lock is unlocked at this point */
2230 return rq;
2232 EXPORT_SYMBOL(blk_get_request);
2235 * blk_requeue_request - put a request back on queue
2236 * @q: request queue where request should be inserted
2237 * @rq: request to be inserted
2239 * Description:
2240 * Drivers often keep queueing requests until the hardware cannot accept
2241 * more, when that condition happens we need to put the request back
2242 * on the queue. Must be called with queue lock held.
2244 void blk_requeue_request(request_queue_t *q, struct request *rq)
2246 blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
2248 if (blk_rq_tagged(rq))
2249 blk_queue_end_tag(q, rq);
2251 elv_requeue_request(q, rq);
2254 EXPORT_SYMBOL(blk_requeue_request);
2257 * blk_insert_request - insert a special request in to a request queue
2258 * @q: request queue where request should be inserted
2259 * @rq: request to be inserted
2260 * @at_head: insert request at head or tail of queue
2261 * @data: private data
2263 * Description:
2264 * Many block devices need to execute commands asynchronously, so they don't
2265 * block the whole kernel from preemption during request execution. This is
2266 * accomplished normally by inserting aritficial requests tagged as
2267 * REQ_SPECIAL in to the corresponding request queue, and letting them be
2268 * scheduled for actual execution by the request queue.
2270 * We have the option of inserting the head or the tail of the queue.
2271 * Typically we use the tail for new ioctls and so forth. We use the head
2272 * of the queue for things like a QUEUE_FULL message from a device, or a
2273 * host that is unable to accept a particular command.
2275 void blk_insert_request(request_queue_t *q, struct request *rq,
2276 int at_head, void *data)
2278 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2279 unsigned long flags;
2282 * tell I/O scheduler that this isn't a regular read/write (ie it
2283 * must not attempt merges on this) and that it acts as a soft
2284 * barrier
2286 rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
2288 rq->special = data;
2290 spin_lock_irqsave(q->queue_lock, flags);
2293 * If command is tagged, release the tag
2295 if (blk_rq_tagged(rq))
2296 blk_queue_end_tag(q, rq);
2298 drive_stat_acct(rq, rq->nr_sectors, 1);
2299 __elv_add_request(q, rq, where, 0);
2301 if (blk_queue_plugged(q))
2302 __generic_unplug_device(q);
2303 else
2304 q->request_fn(q);
2305 spin_unlock_irqrestore(q->queue_lock, flags);
2308 EXPORT_SYMBOL(blk_insert_request);
2311 * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2312 * @q: request queue where request should be inserted
2313 * @rq: request structure to fill
2314 * @ubuf: the user buffer
2315 * @len: length of user data
2317 * Description:
2318 * Data will be mapped directly for zero copy io, if possible. Otherwise
2319 * a kernel bounce buffer is used.
2321 * A matching blk_rq_unmap_user() must be issued at the end of io, while
2322 * still in process context.
2324 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
2325 * before being submitted to the device, as pages mapped may be out of
2326 * reach. It's the callers responsibility to make sure this happens. The
2327 * original bio must be passed back in to blk_rq_unmap_user() for proper
2328 * unmapping.
2330 int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
2331 unsigned int len)
2333 unsigned long uaddr;
2334 struct bio *bio;
2335 int reading;
2337 if (len > (q->max_hw_sectors << 9))
2338 return -EINVAL;
2339 if (!len || !ubuf)
2340 return -EINVAL;
2342 reading = rq_data_dir(rq) == READ;
2345 * if alignment requirement is satisfied, map in user pages for
2346 * direct dma. else, set up kernel bounce buffers
2348 uaddr = (unsigned long) ubuf;
2349 if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
2350 bio = bio_map_user(q, NULL, uaddr, len, reading);
2351 else
2352 bio = bio_copy_user(q, uaddr, len, reading);
2354 if (!IS_ERR(bio)) {
2355 rq->bio = rq->biotail = bio;
2356 blk_rq_bio_prep(q, rq, bio);
2358 rq->buffer = rq->data = NULL;
2359 rq->data_len = len;
2360 return 0;
2364 * bio is the err-ptr
2366 return PTR_ERR(bio);
2369 EXPORT_SYMBOL(blk_rq_map_user);
2372 * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
2373 * @q: request queue where request should be inserted
2374 * @rq: request to map data to
2375 * @iov: pointer to the iovec
2376 * @iov_count: number of elements in the iovec
2378 * Description:
2379 * Data will be mapped directly for zero copy io, if possible. Otherwise
2380 * a kernel bounce buffer is used.
2382 * A matching blk_rq_unmap_user() must be issued at the end of io, while
2383 * still in process context.
2385 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
2386 * before being submitted to the device, as pages mapped may be out of
2387 * reach. It's the callers responsibility to make sure this happens. The
2388 * original bio must be passed back in to blk_rq_unmap_user() for proper
2389 * unmapping.
2391 int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
2392 struct sg_iovec *iov, int iov_count)
2394 struct bio *bio;
2396 if (!iov || iov_count <= 0)
2397 return -EINVAL;
2399 /* we don't allow misaligned data like bio_map_user() does. If the
2400 * user is using sg, they're expected to know the alignment constraints
2401 * and respect them accordingly */
2402 bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
2403 if (IS_ERR(bio))
2404 return PTR_ERR(bio);
2406 rq->bio = rq->biotail = bio;
2407 blk_rq_bio_prep(q, rq, bio);
2408 rq->buffer = rq->data = NULL;
2409 rq->data_len = bio->bi_size;
2410 return 0;
2413 EXPORT_SYMBOL(blk_rq_map_user_iov);
2416 * blk_rq_unmap_user - unmap a request with user data
2417 * @bio: bio to be unmapped
2418 * @ulen: length of user buffer
2420 * Description:
2421 * Unmap a bio previously mapped by blk_rq_map_user().
2423 int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
2425 int ret = 0;
2427 if (bio) {
2428 if (bio_flagged(bio, BIO_USER_MAPPED))
2429 bio_unmap_user(bio);
2430 else
2431 ret = bio_uncopy_user(bio);
2434 return 0;
2437 EXPORT_SYMBOL(blk_rq_unmap_user);
2440 * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
2441 * @q: request queue where request should be inserted
2442 * @rq: request to fill
2443 * @kbuf: the kernel buffer
2444 * @len: length of user data
2445 * @gfp_mask: memory allocation flags
2447 int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
2448 unsigned int len, gfp_t gfp_mask)
2450 struct bio *bio;
2452 if (len > (q->max_hw_sectors << 9))
2453 return -EINVAL;
2454 if (!len || !kbuf)
2455 return -EINVAL;
2457 bio = bio_map_kern(q, kbuf, len, gfp_mask);
2458 if (IS_ERR(bio))
2459 return PTR_ERR(bio);
2461 if (rq_data_dir(rq) == WRITE)
2462 bio->bi_rw |= (1 << BIO_RW);
2464 rq->bio = rq->biotail = bio;
2465 blk_rq_bio_prep(q, rq, bio);
2467 rq->buffer = rq->data = NULL;
2468 rq->data_len = len;
2469 return 0;
2472 EXPORT_SYMBOL(blk_rq_map_kern);
2475 * blk_execute_rq_nowait - insert a request into queue for execution
2476 * @q: queue to insert the request in
2477 * @bd_disk: matching gendisk
2478 * @rq: request to insert
2479 * @at_head: insert request at head or tail of queue
2480 * @done: I/O completion handler
2482 * Description:
2483 * Insert a fully prepared request at the back of the io scheduler queue
2484 * for execution. Don't wait for completion.
2486 void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
2487 struct request *rq, int at_head,
2488 rq_end_io_fn *done)
2490 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2492 rq->rq_disk = bd_disk;
2493 rq->flags |= REQ_NOMERGE;
2494 rq->end_io = done;
2495 WARN_ON(irqs_disabled());
2496 spin_lock_irq(q->queue_lock);
2497 __elv_add_request(q, rq, where, 1);
2498 __generic_unplug_device(q);
2499 spin_unlock_irq(q->queue_lock);
2501 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
2504 * blk_execute_rq - insert a request into queue for execution
2505 * @q: queue to insert the request in
2506 * @bd_disk: matching gendisk
2507 * @rq: request to insert
2508 * @at_head: insert request at head or tail of queue
2510 * Description:
2511 * Insert a fully prepared request at the back of the io scheduler queue
2512 * for execution and wait for completion.
2514 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2515 struct request *rq, int at_head)
2517 DECLARE_COMPLETION(wait);
2518 char sense[SCSI_SENSE_BUFFERSIZE];
2519 int err = 0;
2522 * we need an extra reference to the request, so we can look at
2523 * it after io completion
2525 rq->ref_count++;
2527 if (!rq->sense) {
2528 memset(sense, 0, sizeof(sense));
2529 rq->sense = sense;
2530 rq->sense_len = 0;
2533 rq->waiting = &wait;
2534 blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
2535 wait_for_completion(&wait);
2536 rq->waiting = NULL;
2538 if (rq->errors)
2539 err = -EIO;
2541 return err;
2544 EXPORT_SYMBOL(blk_execute_rq);
2547 * blkdev_issue_flush - queue a flush
2548 * @bdev: blockdev to issue flush for
2549 * @error_sector: error sector
2551 * Description:
2552 * Issue a flush for the block device in question. Caller can supply
2553 * room for storing the error offset in case of a flush error, if they
2554 * wish to. Caller must run wait_for_completion() on its own.
2556 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2558 request_queue_t *q;
2560 if (bdev->bd_disk == NULL)
2561 return -ENXIO;
2563 q = bdev_get_queue(bdev);
2564 if (!q)
2565 return -ENXIO;
2566 if (!q->issue_flush_fn)
2567 return -EOPNOTSUPP;
2569 return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2572 EXPORT_SYMBOL(blkdev_issue_flush);
2574 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2576 int rw = rq_data_dir(rq);
2578 if (!blk_fs_request(rq) || !rq->rq_disk)
2579 return;
2581 if (!new_io) {
2582 __disk_stat_inc(rq->rq_disk, merges[rw]);
2583 } else {
2584 disk_round_stats(rq->rq_disk);
2585 rq->rq_disk->in_flight++;
2590 * add-request adds a request to the linked list.
2591 * queue lock is held and interrupts disabled, as we muck with the
2592 * request queue list.
2594 static inline void add_request(request_queue_t * q, struct request * req)
2596 drive_stat_acct(req, req->nr_sectors, 1);
2598 if (q->activity_fn)
2599 q->activity_fn(q->activity_data, rq_data_dir(req));
2602 * elevator indicated where it wants this request to be
2603 * inserted at elevator_merge time
2605 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2609 * disk_round_stats() - Round off the performance stats on a struct
2610 * disk_stats.
2612 * The average IO queue length and utilisation statistics are maintained
2613 * by observing the current state of the queue length and the amount of
2614 * time it has been in this state for.
2616 * Normally, that accounting is done on IO completion, but that can result
2617 * in more than a second's worth of IO being accounted for within any one
2618 * second, leading to >100% utilisation. To deal with that, we call this
2619 * function to do a round-off before returning the results when reading
2620 * /proc/diskstats. This accounts immediately for all queue usage up to
2621 * the current jiffies and restarts the counters again.
2623 void disk_round_stats(struct gendisk *disk)
2625 unsigned long now = jiffies;
2627 if (now == disk->stamp)
2628 return;
2630 if (disk->in_flight) {
2631 __disk_stat_add(disk, time_in_queue,
2632 disk->in_flight * (now - disk->stamp));
2633 __disk_stat_add(disk, io_ticks, (now - disk->stamp));
2635 disk->stamp = now;
2638 EXPORT_SYMBOL_GPL(disk_round_stats);
2641 * queue lock must be held
2643 void __blk_put_request(request_queue_t *q, struct request *req)
2645 struct request_list *rl = req->rl;
2647 if (unlikely(!q))
2648 return;
2649 if (unlikely(--req->ref_count))
2650 return;
2652 elv_completed_request(q, req);
2654 req->rq_status = RQ_INACTIVE;
2655 req->rl = NULL;
2658 * Request may not have originated from ll_rw_blk. if not,
2659 * it didn't come out of our reserved rq pools
2661 if (rl) {
2662 int rw = rq_data_dir(req);
2663 int priv = req->flags & REQ_ELVPRIV;
2665 BUG_ON(!list_empty(&req->queuelist));
2667 blk_free_request(q, req);
2668 freed_request(q, rw, priv);
2672 EXPORT_SYMBOL_GPL(__blk_put_request);
2674 void blk_put_request(struct request *req)
2676 unsigned long flags;
2677 request_queue_t *q = req->q;
2680 * Gee, IDE calls in w/ NULL q. Fix IDE and remove the
2681 * following if (q) test.
2683 if (q) {
2684 spin_lock_irqsave(q->queue_lock, flags);
2685 __blk_put_request(q, req);
2686 spin_unlock_irqrestore(q->queue_lock, flags);
2690 EXPORT_SYMBOL(blk_put_request);
2693 * blk_end_sync_rq - executes a completion event on a request
2694 * @rq: request to complete
2695 * @error: end io status of the request
2697 void blk_end_sync_rq(struct request *rq, int error)
2699 struct completion *waiting = rq->waiting;
2701 rq->waiting = NULL;
2702 __blk_put_request(rq->q, rq);
2705 * complete last, if this is a stack request the process (and thus
2706 * the rq pointer) could be invalid right after this complete()
2708 complete(waiting);
2710 EXPORT_SYMBOL(blk_end_sync_rq);
2713 * blk_congestion_wait - wait for a queue to become uncongested
2714 * @rw: READ or WRITE
2715 * @timeout: timeout in jiffies
2717 * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2718 * If no queues are congested then just wait for the next request to be
2719 * returned.
2721 long blk_congestion_wait(int rw, long timeout)
2723 long ret;
2724 DEFINE_WAIT(wait);
2725 wait_queue_head_t *wqh = &congestion_wqh[rw];
2727 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2728 ret = io_schedule_timeout(timeout);
2729 finish_wait(wqh, &wait);
2730 return ret;
2733 EXPORT_SYMBOL(blk_congestion_wait);
2736 * Has to be called with the request spinlock acquired
2738 static int attempt_merge(request_queue_t *q, struct request *req,
2739 struct request *next)
2741 if (!rq_mergeable(req) || !rq_mergeable(next))
2742 return 0;
2745 * not contigious
2747 if (req->sector + req->nr_sectors != next->sector)
2748 return 0;
2750 if (rq_data_dir(req) != rq_data_dir(next)
2751 || req->rq_disk != next->rq_disk
2752 || next->waiting || next->special)
2753 return 0;
2756 * If we are allowed to merge, then append bio list
2757 * from next to rq and release next. merge_requests_fn
2758 * will have updated segment counts, update sector
2759 * counts here.
2761 if (!q->merge_requests_fn(q, req, next))
2762 return 0;
2765 * At this point we have either done a back merge
2766 * or front merge. We need the smaller start_time of
2767 * the merged requests to be the current request
2768 * for accounting purposes.
2770 if (time_after(req->start_time, next->start_time))
2771 req->start_time = next->start_time;
2773 req->biotail->bi_next = next->bio;
2774 req->biotail = next->biotail;
2776 req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2778 elv_merge_requests(q, req, next);
2780 if (req->rq_disk) {
2781 disk_round_stats(req->rq_disk);
2782 req->rq_disk->in_flight--;
2785 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
2787 __blk_put_request(q, next);
2788 return 1;
2791 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2793 struct request *next = elv_latter_request(q, rq);
2795 if (next)
2796 return attempt_merge(q, rq, next);
2798 return 0;
2801 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2803 struct request *prev = elv_former_request(q, rq);
2805 if (prev)
2806 return attempt_merge(q, prev, rq);
2808 return 0;
2811 static void init_request_from_bio(struct request *req, struct bio *bio)
2813 req->flags |= REQ_CMD;
2816 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2818 if (bio_rw_ahead(bio) || bio_failfast(bio))
2819 req->flags |= REQ_FAILFAST;
2822 * REQ_BARRIER implies no merging, but lets make it explicit
2824 if (unlikely(bio_barrier(bio)))
2825 req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2827 req->errors = 0;
2828 req->hard_sector = req->sector = bio->bi_sector;
2829 req->hard_nr_sectors = req->nr_sectors = bio_sectors(bio);
2830 req->current_nr_sectors = req->hard_cur_sectors = bio_cur_sectors(bio);
2831 req->nr_phys_segments = bio_phys_segments(req->q, bio);
2832 req->nr_hw_segments = bio_hw_segments(req->q, bio);
2833 req->buffer = bio_data(bio); /* see ->buffer comment above */
2834 req->waiting = NULL;
2835 req->bio = req->biotail = bio;
2836 req->ioprio = bio_prio(bio);
2837 req->rq_disk = bio->bi_bdev->bd_disk;
2838 req->start_time = jiffies;
2841 static int __make_request(request_queue_t *q, struct bio *bio)
2843 struct request *req;
2844 int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
2845 unsigned short prio;
2846 sector_t sector;
2848 sector = bio->bi_sector;
2849 nr_sectors = bio_sectors(bio);
2850 cur_nr_sectors = bio_cur_sectors(bio);
2851 prio = bio_prio(bio);
2853 rw = bio_data_dir(bio);
2854 sync = bio_sync(bio);
2857 * low level driver can indicate that it wants pages above a
2858 * certain limit bounced to low memory (ie for highmem, or even
2859 * ISA dma in theory)
2861 blk_queue_bounce(q, &bio);
2863 spin_lock_prefetch(q->queue_lock);
2865 barrier = bio_barrier(bio);
2866 if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {
2867 err = -EOPNOTSUPP;
2868 goto end_io;
2871 spin_lock_irq(q->queue_lock);
2873 if (unlikely(barrier) || elv_queue_empty(q))
2874 goto get_rq;
2876 el_ret = elv_merge(q, &req, bio);
2877 switch (el_ret) {
2878 case ELEVATOR_BACK_MERGE:
2879 BUG_ON(!rq_mergeable(req));
2881 if (!q->back_merge_fn(q, req, bio))
2882 break;
2884 blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
2886 req->biotail->bi_next = bio;
2887 req->biotail = bio;
2888 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2889 req->ioprio = ioprio_best(req->ioprio, prio);
2890 drive_stat_acct(req, nr_sectors, 0);
2891 if (!attempt_back_merge(q, req))
2892 elv_merged_request(q, req);
2893 goto out;
2895 case ELEVATOR_FRONT_MERGE:
2896 BUG_ON(!rq_mergeable(req));
2898 if (!q->front_merge_fn(q, req, bio))
2899 break;
2901 blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
2903 bio->bi_next = req->bio;
2904 req->bio = bio;
2907 * may not be valid. if the low level driver said
2908 * it didn't need a bounce buffer then it better
2909 * not touch req->buffer either...
2911 req->buffer = bio_data(bio);
2912 req->current_nr_sectors = cur_nr_sectors;
2913 req->hard_cur_sectors = cur_nr_sectors;
2914 req->sector = req->hard_sector = sector;
2915 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2916 req->ioprio = ioprio_best(req->ioprio, prio);
2917 drive_stat_acct(req, nr_sectors, 0);
2918 if (!attempt_front_merge(q, req))
2919 elv_merged_request(q, req);
2920 goto out;
2922 /* ELV_NO_MERGE: elevator says don't/can't merge. */
2923 default:
2927 get_rq:
2929 * Grab a free request. This is might sleep but can not fail.
2930 * Returns with the queue unlocked.
2932 req = get_request_wait(q, rw, bio);
2935 * After dropping the lock and possibly sleeping here, our request
2936 * may now be mergeable after it had proven unmergeable (above).
2937 * We don't worry about that case for efficiency. It won't happen
2938 * often, and the elevators are able to handle it.
2940 init_request_from_bio(req, bio);
2942 spin_lock_irq(q->queue_lock);
2943 if (elv_queue_empty(q))
2944 blk_plug_device(q);
2945 add_request(q, req);
2946 out:
2947 if (sync)
2948 __generic_unplug_device(q);
2950 spin_unlock_irq(q->queue_lock);
2951 return 0;
2953 end_io:
2954 bio_endio(bio, nr_sectors << 9, err);
2955 return 0;
2959 * If bio->bi_dev is a partition, remap the location
2961 static inline void blk_partition_remap(struct bio *bio)
2963 struct block_device *bdev = bio->bi_bdev;
2965 if (bdev != bdev->bd_contains) {
2966 struct hd_struct *p = bdev->bd_part;
2967 const int rw = bio_data_dir(bio);
2969 p->sectors[rw] += bio_sectors(bio);
2970 p->ios[rw]++;
2972 bio->bi_sector += p->start_sect;
2973 bio->bi_bdev = bdev->bd_contains;
2977 static void handle_bad_sector(struct bio *bio)
2979 char b[BDEVNAME_SIZE];
2981 printk(KERN_INFO "attempt to access beyond end of device\n");
2982 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
2983 bdevname(bio->bi_bdev, b),
2984 bio->bi_rw,
2985 (unsigned long long)bio->bi_sector + bio_sectors(bio),
2986 (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
2988 set_bit(BIO_EOF, &bio->bi_flags);
2992 * generic_make_request: hand a buffer to its device driver for I/O
2993 * @bio: The bio describing the location in memory and on the device.
2995 * generic_make_request() is used to make I/O requests of block
2996 * devices. It is passed a &struct bio, which describes the I/O that needs
2997 * to be done.
2999 * generic_make_request() does not return any status. The
3000 * success/failure status of the request, along with notification of
3001 * completion, is delivered asynchronously through the bio->bi_end_io
3002 * function described (one day) else where.
3004 * The caller of generic_make_request must make sure that bi_io_vec
3005 * are set to describe the memory buffer, and that bi_dev and bi_sector are
3006 * set to describe the device address, and the
3007 * bi_end_io and optionally bi_private are set to describe how
3008 * completion notification should be signaled.
3010 * generic_make_request and the drivers it calls may use bi_next if this
3011 * bio happens to be merged with someone else, and may change bi_dev and
3012 * bi_sector for remaps as it sees fit. So the values of these fields
3013 * should NOT be depended on after the call to generic_make_request.
3015 void generic_make_request(struct bio *bio)
3017 request_queue_t *q;
3018 sector_t maxsector;
3019 int ret, nr_sectors = bio_sectors(bio);
3020 dev_t old_dev;
3022 might_sleep();
3023 /* Test device or partition size, when known. */
3024 maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
3025 if (maxsector) {
3026 sector_t sector = bio->bi_sector;
3028 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
3030 * This may well happen - the kernel calls bread()
3031 * without checking the size of the device, e.g., when
3032 * mounting a device.
3034 handle_bad_sector(bio);
3035 goto end_io;
3040 * Resolve the mapping until finished. (drivers are
3041 * still free to implement/resolve their own stacking
3042 * by explicitly returning 0)
3044 * NOTE: we don't repeat the blk_size check for each new device.
3045 * Stacking drivers are expected to know what they are doing.
3047 maxsector = -1;
3048 old_dev = 0;
3049 do {
3050 char b[BDEVNAME_SIZE];
3052 q = bdev_get_queue(bio->bi_bdev);
3053 if (!q) {
3054 printk(KERN_ERR
3055 "generic_make_request: Trying to access "
3056 "nonexistent block-device %s (%Lu)\n",
3057 bdevname(bio->bi_bdev, b),
3058 (long long) bio->bi_sector);
3059 end_io:
3060 bio_endio(bio, bio->bi_size, -EIO);
3061 break;
3064 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
3065 printk("bio too big device %s (%u > %u)\n",
3066 bdevname(bio->bi_bdev, b),
3067 bio_sectors(bio),
3068 q->max_hw_sectors);
3069 goto end_io;
3072 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
3073 goto end_io;
3076 * If this device has partitions, remap block n
3077 * of partition p to block n+start(p) of the disk.
3079 blk_partition_remap(bio);
3081 if (maxsector != -1)
3082 blk_add_trace_remap(q, bio, old_dev, bio->bi_sector,
3083 maxsector);
3085 blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
3087 maxsector = bio->bi_sector;
3088 old_dev = bio->bi_bdev->bd_dev;
3090 ret = q->make_request_fn(q, bio);
3091 } while (ret);
3094 EXPORT_SYMBOL(generic_make_request);
3097 * submit_bio: submit a bio to the block device layer for I/O
3098 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
3099 * @bio: The &struct bio which describes the I/O
3101 * submit_bio() is very similar in purpose to generic_make_request(), and
3102 * uses that function to do most of the work. Both are fairly rough
3103 * interfaces, @bio must be presetup and ready for I/O.
3106 void submit_bio(int rw, struct bio *bio)
3108 int count = bio_sectors(bio);
3110 BIO_BUG_ON(!bio->bi_size);
3111 BIO_BUG_ON(!bio->bi_io_vec);
3112 bio->bi_rw |= rw;
3113 if (rw & WRITE)
3114 mod_page_state(pgpgout, count);
3115 else
3116 mod_page_state(pgpgin, count);
3118 if (unlikely(block_dump)) {
3119 char b[BDEVNAME_SIZE];
3120 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
3121 current->comm, current->pid,
3122 (rw & WRITE) ? "WRITE" : "READ",
3123 (unsigned long long)bio->bi_sector,
3124 bdevname(bio->bi_bdev,b));
3127 generic_make_request(bio);
3130 EXPORT_SYMBOL(submit_bio);
3132 static void blk_recalc_rq_segments(struct request *rq)
3134 struct bio *bio, *prevbio = NULL;
3135 int nr_phys_segs, nr_hw_segs;
3136 unsigned int phys_size, hw_size;
3137 request_queue_t *q = rq->q;
3139 if (!rq->bio)
3140 return;
3142 phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
3143 rq_for_each_bio(bio, rq) {
3144 /* Force bio hw/phys segs to be recalculated. */
3145 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
3147 nr_phys_segs += bio_phys_segments(q, bio);
3148 nr_hw_segs += bio_hw_segments(q, bio);
3149 if (prevbio) {
3150 int pseg = phys_size + prevbio->bi_size + bio->bi_size;
3151 int hseg = hw_size + prevbio->bi_size + bio->bi_size;
3153 if (blk_phys_contig_segment(q, prevbio, bio) &&
3154 pseg <= q->max_segment_size) {
3155 nr_phys_segs--;
3156 phys_size += prevbio->bi_size + bio->bi_size;
3157 } else
3158 phys_size = 0;
3160 if (blk_hw_contig_segment(q, prevbio, bio) &&
3161 hseg <= q->max_segment_size) {
3162 nr_hw_segs--;
3163 hw_size += prevbio->bi_size + bio->bi_size;
3164 } else
3165 hw_size = 0;
3167 prevbio = bio;
3170 rq->nr_phys_segments = nr_phys_segs;
3171 rq->nr_hw_segments = nr_hw_segs;
3174 static void blk_recalc_rq_sectors(struct request *rq, int nsect)
3176 if (blk_fs_request(rq)) {
3177 rq->hard_sector += nsect;
3178 rq->hard_nr_sectors -= nsect;
3181 * Move the I/O submission pointers ahead if required.
3183 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
3184 (rq->sector <= rq->hard_sector)) {
3185 rq->sector = rq->hard_sector;
3186 rq->nr_sectors = rq->hard_nr_sectors;
3187 rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
3188 rq->current_nr_sectors = rq->hard_cur_sectors;
3189 rq->buffer = bio_data(rq->bio);
3193 * if total number of sectors is less than the first segment
3194 * size, something has gone terribly wrong
3196 if (rq->nr_sectors < rq->current_nr_sectors) {
3197 printk("blk: request botched\n");
3198 rq->nr_sectors = rq->current_nr_sectors;
3203 static int __end_that_request_first(struct request *req, int uptodate,
3204 int nr_bytes)
3206 int total_bytes, bio_nbytes, error, next_idx = 0;
3207 struct bio *bio;
3209 blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE);
3212 * extend uptodate bool to allow < 0 value to be direct io error
3214 error = 0;
3215 if (end_io_error(uptodate))
3216 error = !uptodate ? -EIO : uptodate;
3219 * for a REQ_BLOCK_PC request, we want to carry any eventual
3220 * sense key with us all the way through
3222 if (!blk_pc_request(req))
3223 req->errors = 0;
3225 if (!uptodate) {
3226 if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
3227 printk("end_request: I/O error, dev %s, sector %llu\n",
3228 req->rq_disk ? req->rq_disk->disk_name : "?",
3229 (unsigned long long)req->sector);
3232 if (blk_fs_request(req) && req->rq_disk) {
3233 const int rw = rq_data_dir(req);
3235 disk_stat_add(req->rq_disk, sectors[rw], nr_bytes >> 9);
3238 total_bytes = bio_nbytes = 0;
3239 while ((bio = req->bio) != NULL) {
3240 int nbytes;
3242 if (nr_bytes >= bio->bi_size) {
3243 req->bio = bio->bi_next;
3244 nbytes = bio->bi_size;
3245 if (!ordered_bio_endio(req, bio, nbytes, error))
3246 bio_endio(bio, nbytes, error);
3247 next_idx = 0;
3248 bio_nbytes = 0;
3249 } else {
3250 int idx = bio->bi_idx + next_idx;
3252 if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
3253 blk_dump_rq_flags(req, "__end_that");
3254 printk("%s: bio idx %d >= vcnt %d\n",
3255 __FUNCTION__,
3256 bio->bi_idx, bio->bi_vcnt);
3257 break;
3260 nbytes = bio_iovec_idx(bio, idx)->bv_len;
3261 BIO_BUG_ON(nbytes > bio->bi_size);
3264 * not a complete bvec done
3266 if (unlikely(nbytes > nr_bytes)) {
3267 bio_nbytes += nr_bytes;
3268 total_bytes += nr_bytes;
3269 break;
3273 * advance to the next vector
3275 next_idx++;
3276 bio_nbytes += nbytes;
3279 total_bytes += nbytes;
3280 nr_bytes -= nbytes;
3282 if ((bio = req->bio)) {
3284 * end more in this run, or just return 'not-done'
3286 if (unlikely(nr_bytes <= 0))
3287 break;
3292 * completely done
3294 if (!req->bio)
3295 return 0;
3298 * if the request wasn't completed, update state
3300 if (bio_nbytes) {
3301 if (!ordered_bio_endio(req, bio, bio_nbytes, error))
3302 bio_endio(bio, bio_nbytes, error);
3303 bio->bi_idx += next_idx;
3304 bio_iovec(bio)->bv_offset += nr_bytes;
3305 bio_iovec(bio)->bv_len -= nr_bytes;
3308 blk_recalc_rq_sectors(req, total_bytes >> 9);
3309 blk_recalc_rq_segments(req);
3310 return 1;
3314 * end_that_request_first - end I/O on a request
3315 * @req: the request being processed
3316 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3317 * @nr_sectors: number of sectors to end I/O on
3319 * Description:
3320 * Ends I/O on a number of sectors attached to @req, and sets it up
3321 * for the next range of segments (if any) in the cluster.
3323 * Return:
3324 * 0 - we are done with this request, call end_that_request_last()
3325 * 1 - still buffers pending for this request
3327 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
3329 return __end_that_request_first(req, uptodate, nr_sectors << 9);
3332 EXPORT_SYMBOL(end_that_request_first);
3335 * end_that_request_chunk - end I/O on a request
3336 * @req: the request being processed
3337 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3338 * @nr_bytes: number of bytes to complete
3340 * Description:
3341 * Ends I/O on a number of bytes attached to @req, and sets it up
3342 * for the next range of segments (if any). Like end_that_request_first(),
3343 * but deals with bytes instead of sectors.
3345 * Return:
3346 * 0 - we are done with this request, call end_that_request_last()
3347 * 1 - still buffers pending for this request
3349 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
3351 return __end_that_request_first(req, uptodate, nr_bytes);
3354 EXPORT_SYMBOL(end_that_request_chunk);
3357 * splice the completion data to a local structure and hand off to
3358 * process_completion_queue() to complete the requests
3360 static void blk_done_softirq(struct softirq_action *h)
3362 struct list_head *cpu_list;
3363 LIST_HEAD(local_list);
3365 local_irq_disable();
3366 cpu_list = &__get_cpu_var(blk_cpu_done);
3367 list_splice_init(cpu_list, &local_list);
3368 local_irq_enable();
3370 while (!list_empty(&local_list)) {
3371 struct request *rq = list_entry(local_list.next, struct request, donelist);
3373 list_del_init(&rq->donelist);
3374 rq->q->softirq_done_fn(rq);
3378 #ifdef CONFIG_HOTPLUG_CPU
3380 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
3381 void *hcpu)
3384 * If a CPU goes away, splice its entries to the current CPU
3385 * and trigger a run of the softirq
3387 if (action == CPU_DEAD) {
3388 int cpu = (unsigned long) hcpu;
3390 local_irq_disable();
3391 list_splice_init(&per_cpu(blk_cpu_done, cpu),
3392 &__get_cpu_var(blk_cpu_done));
3393 raise_softirq_irqoff(BLOCK_SOFTIRQ);
3394 local_irq_enable();
3397 return NOTIFY_OK;
3401 static struct notifier_block blk_cpu_notifier = {
3402 .notifier_call = blk_cpu_notify,
3405 #endif /* CONFIG_HOTPLUG_CPU */
3408 * blk_complete_request - end I/O on a request
3409 * @req: the request being processed
3411 * Description:
3412 * Ends all I/O on a request. It does not handle partial completions,
3413 * unless the driver actually implements this in its completionc callback
3414 * through requeueing. Theh actual completion happens out-of-order,
3415 * through a softirq handler. The user must have registered a completion
3416 * callback through blk_queue_softirq_done().
3419 void blk_complete_request(struct request *req)
3421 struct list_head *cpu_list;
3422 unsigned long flags;
3424 BUG_ON(!req->q->softirq_done_fn);
3426 local_irq_save(flags);
3428 cpu_list = &__get_cpu_var(blk_cpu_done);
3429 list_add_tail(&req->donelist, cpu_list);
3430 raise_softirq_irqoff(BLOCK_SOFTIRQ);
3432 local_irq_restore(flags);
3435 EXPORT_SYMBOL(blk_complete_request);
3438 * queue lock must be held
3440 void end_that_request_last(struct request *req, int uptodate)
3442 struct gendisk *disk = req->rq_disk;
3443 int error;
3446 * extend uptodate bool to allow < 0 value to be direct io error
3448 error = 0;
3449 if (end_io_error(uptodate))
3450 error = !uptodate ? -EIO : uptodate;
3452 if (unlikely(laptop_mode) && blk_fs_request(req))
3453 laptop_io_completion();
3456 * Account IO completion. bar_rq isn't accounted as a normal
3457 * IO on queueing nor completion. Accounting the containing
3458 * request is enough.
3460 if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
3461 unsigned long duration = jiffies - req->start_time;
3462 const int rw = rq_data_dir(req);
3464 __disk_stat_inc(disk, ios[rw]);
3465 __disk_stat_add(disk, ticks[rw], duration);
3466 disk_round_stats(disk);
3467 disk->in_flight--;
3469 if (req->end_io)
3470 req->end_io(req, error);
3471 else
3472 __blk_put_request(req->q, req);
3475 EXPORT_SYMBOL(end_that_request_last);
3477 void end_request(struct request *req, int uptodate)
3479 if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3480 add_disk_randomness(req->rq_disk);
3481 blkdev_dequeue_request(req);
3482 end_that_request_last(req, uptodate);
3486 EXPORT_SYMBOL(end_request);
3488 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3490 /* first three bits are identical in rq->flags and bio->bi_rw */
3491 rq->flags |= (bio->bi_rw & 7);
3493 rq->nr_phys_segments = bio_phys_segments(q, bio);
3494 rq->nr_hw_segments = bio_hw_segments(q, bio);
3495 rq->current_nr_sectors = bio_cur_sectors(bio);
3496 rq->hard_cur_sectors = rq->current_nr_sectors;
3497 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3498 rq->buffer = bio_data(bio);
3500 rq->bio = rq->biotail = bio;
3503 EXPORT_SYMBOL(blk_rq_bio_prep);
3505 int kblockd_schedule_work(struct work_struct *work)
3507 return queue_work(kblockd_workqueue, work);
3510 EXPORT_SYMBOL(kblockd_schedule_work);
3512 void kblockd_flush(void)
3514 flush_workqueue(kblockd_workqueue);
3516 EXPORT_SYMBOL(kblockd_flush);
3518 int __init blk_dev_init(void)
3520 int i;
3522 kblockd_workqueue = create_workqueue("kblockd");
3523 if (!kblockd_workqueue)
3524 panic("Failed to create kblockd\n");
3526 request_cachep = kmem_cache_create("blkdev_requests",
3527 sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3529 requestq_cachep = kmem_cache_create("blkdev_queue",
3530 sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3532 iocontext_cachep = kmem_cache_create("blkdev_ioc",
3533 sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3535 for_each_possible_cpu(i)
3536 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
3538 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
3539 #ifdef CONFIG_HOTPLUG_CPU
3540 register_cpu_notifier(&blk_cpu_notifier);
3541 #endif
3543 blk_max_low_pfn = max_low_pfn;
3544 blk_max_pfn = max_pfn;
3546 return 0;
3550 * IO Context helper functions
3552 void put_io_context(struct io_context *ioc)
3554 if (ioc == NULL)
3555 return;
3557 BUG_ON(atomic_read(&ioc->refcount) == 0);
3559 if (atomic_dec_and_test(&ioc->refcount)) {
3560 struct cfq_io_context *cic;
3562 rcu_read_lock();
3563 if (ioc->aic && ioc->aic->dtor)
3564 ioc->aic->dtor(ioc->aic);
3565 if (ioc->cic_root.rb_node != NULL) {
3566 struct rb_node *n = rb_first(&ioc->cic_root);
3568 cic = rb_entry(n, struct cfq_io_context, rb_node);
3569 cic->dtor(ioc);
3571 rcu_read_unlock();
3573 kmem_cache_free(iocontext_cachep, ioc);
3576 EXPORT_SYMBOL(put_io_context);
3578 /* Called by the exitting task */
3579 void exit_io_context(void)
3581 unsigned long flags;
3582 struct io_context *ioc;
3583 struct cfq_io_context *cic;
3585 local_irq_save(flags);
3586 task_lock(current);
3587 ioc = current->io_context;
3588 current->io_context = NULL;
3589 ioc->task = NULL;
3590 task_unlock(current);
3591 local_irq_restore(flags);
3593 if (ioc->aic && ioc->aic->exit)
3594 ioc->aic->exit(ioc->aic);
3595 if (ioc->cic_root.rb_node != NULL) {
3596 cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
3597 cic->exit(ioc);
3600 put_io_context(ioc);
3604 * If the current task has no IO context then create one and initialise it.
3605 * Otherwise, return its existing IO context.
3607 * This returned IO context doesn't have a specifically elevated refcount,
3608 * but since the current task itself holds a reference, the context can be
3609 * used in general code, so long as it stays within `current` context.
3611 struct io_context *current_io_context(gfp_t gfp_flags)
3613 struct task_struct *tsk = current;
3614 struct io_context *ret;
3616 ret = tsk->io_context;
3617 if (likely(ret))
3618 return ret;
3620 ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3621 if (ret) {
3622 atomic_set(&ret->refcount, 1);
3623 ret->task = current;
3624 ret->set_ioprio = NULL;
3625 ret->last_waited = jiffies; /* doesn't matter... */
3626 ret->nr_batch_requests = 0; /* because this is 0 */
3627 ret->aic = NULL;
3628 ret->cic_root.rb_node = NULL;
3629 tsk->io_context = ret;
3632 return ret;
3634 EXPORT_SYMBOL(current_io_context);
3637 * If the current task has no IO context then create one and initialise it.
3638 * If it does have a context, take a ref on it.
3640 * This is always called in the context of the task which submitted the I/O.
3642 struct io_context *get_io_context(gfp_t gfp_flags)
3644 struct io_context *ret;
3645 ret = current_io_context(gfp_flags);
3646 if (likely(ret))
3647 atomic_inc(&ret->refcount);
3648 return ret;
3650 EXPORT_SYMBOL(get_io_context);
3652 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3654 struct io_context *src = *psrc;
3655 struct io_context *dst = *pdst;
3657 if (src) {
3658 BUG_ON(atomic_read(&src->refcount) == 0);
3659 atomic_inc(&src->refcount);
3660 put_io_context(dst);
3661 *pdst = src;
3664 EXPORT_SYMBOL(copy_io_context);
3666 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3668 struct io_context *temp;
3669 temp = *ioc1;
3670 *ioc1 = *ioc2;
3671 *ioc2 = temp;
3673 EXPORT_SYMBOL(swap_io_context);
3676 * sysfs parts below
3678 struct queue_sysfs_entry {
3679 struct attribute attr;
3680 ssize_t (*show)(struct request_queue *, char *);
3681 ssize_t (*store)(struct request_queue *, const char *, size_t);
3684 static ssize_t
3685 queue_var_show(unsigned int var, char *page)
3687 return sprintf(page, "%d\n", var);
3690 static ssize_t
3691 queue_var_store(unsigned long *var, const char *page, size_t count)
3693 char *p = (char *) page;
3695 *var = simple_strtoul(p, &p, 10);
3696 return count;
3699 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3701 return queue_var_show(q->nr_requests, (page));
3704 static ssize_t
3705 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3707 struct request_list *rl = &q->rq;
3708 unsigned long nr;
3709 int ret = queue_var_store(&nr, page, count);
3710 if (nr < BLKDEV_MIN_RQ)
3711 nr = BLKDEV_MIN_RQ;
3713 spin_lock_irq(q->queue_lock);
3714 q->nr_requests = nr;
3715 blk_queue_congestion_threshold(q);
3717 if (rl->count[READ] >= queue_congestion_on_threshold(q))
3718 set_queue_congested(q, READ);
3719 else if (rl->count[READ] < queue_congestion_off_threshold(q))
3720 clear_queue_congested(q, READ);
3722 if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3723 set_queue_congested(q, WRITE);
3724 else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3725 clear_queue_congested(q, WRITE);
3727 if (rl->count[READ] >= q->nr_requests) {
3728 blk_set_queue_full(q, READ);
3729 } else if (rl->count[READ]+1 <= q->nr_requests) {
3730 blk_clear_queue_full(q, READ);
3731 wake_up(&rl->wait[READ]);
3734 if (rl->count[WRITE] >= q->nr_requests) {
3735 blk_set_queue_full(q, WRITE);
3736 } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3737 blk_clear_queue_full(q, WRITE);
3738 wake_up(&rl->wait[WRITE]);
3740 spin_unlock_irq(q->queue_lock);
3741 return ret;
3744 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3746 int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3748 return queue_var_show(ra_kb, (page));
3751 static ssize_t
3752 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3754 unsigned long ra_kb;
3755 ssize_t ret = queue_var_store(&ra_kb, page, count);
3757 spin_lock_irq(q->queue_lock);
3758 if (ra_kb > (q->max_sectors >> 1))
3759 ra_kb = (q->max_sectors >> 1);
3761 q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3762 spin_unlock_irq(q->queue_lock);
3764 return ret;
3767 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3769 int max_sectors_kb = q->max_sectors >> 1;
3771 return queue_var_show(max_sectors_kb, (page));
3774 static ssize_t
3775 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3777 unsigned long max_sectors_kb,
3778 max_hw_sectors_kb = q->max_hw_sectors >> 1,
3779 page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3780 ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3781 int ra_kb;
3783 if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3784 return -EINVAL;
3786 * Take the queue lock to update the readahead and max_sectors
3787 * values synchronously:
3789 spin_lock_irq(q->queue_lock);
3791 * Trim readahead window as well, if necessary:
3793 ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3794 if (ra_kb > max_sectors_kb)
3795 q->backing_dev_info.ra_pages =
3796 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3798 q->max_sectors = max_sectors_kb << 1;
3799 spin_unlock_irq(q->queue_lock);
3801 return ret;
3804 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3806 int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3808 return queue_var_show(max_hw_sectors_kb, (page));
3812 static struct queue_sysfs_entry queue_requests_entry = {
3813 .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3814 .show = queue_requests_show,
3815 .store = queue_requests_store,
3818 static struct queue_sysfs_entry queue_ra_entry = {
3819 .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3820 .show = queue_ra_show,
3821 .store = queue_ra_store,
3824 static struct queue_sysfs_entry queue_max_sectors_entry = {
3825 .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3826 .show = queue_max_sectors_show,
3827 .store = queue_max_sectors_store,
3830 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3831 .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3832 .show = queue_max_hw_sectors_show,
3835 static struct queue_sysfs_entry queue_iosched_entry = {
3836 .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3837 .show = elv_iosched_show,
3838 .store = elv_iosched_store,
3841 static struct attribute *default_attrs[] = {
3842 &queue_requests_entry.attr,
3843 &queue_ra_entry.attr,
3844 &queue_max_hw_sectors_entry.attr,
3845 &queue_max_sectors_entry.attr,
3846 &queue_iosched_entry.attr,
3847 NULL,
3850 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3852 static ssize_t
3853 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3855 struct queue_sysfs_entry *entry = to_queue(attr);
3856 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3857 ssize_t res;
3859 if (!entry->show)
3860 return -EIO;
3861 mutex_lock(&q->sysfs_lock);
3862 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3863 mutex_unlock(&q->sysfs_lock);
3864 return -ENOENT;
3866 res = entry->show(q, page);
3867 mutex_unlock(&q->sysfs_lock);
3868 return res;
3871 static ssize_t
3872 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3873 const char *page, size_t length)
3875 struct queue_sysfs_entry *entry = to_queue(attr);
3876 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3878 ssize_t res;
3880 if (!entry->store)
3881 return -EIO;
3882 mutex_lock(&q->sysfs_lock);
3883 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3884 mutex_unlock(&q->sysfs_lock);
3885 return -ENOENT;
3887 res = entry->store(q, page, length);
3888 mutex_unlock(&q->sysfs_lock);
3889 return res;
3892 static struct sysfs_ops queue_sysfs_ops = {
3893 .show = queue_attr_show,
3894 .store = queue_attr_store,
3897 static struct kobj_type queue_ktype = {
3898 .sysfs_ops = &queue_sysfs_ops,
3899 .default_attrs = default_attrs,
3900 .release = blk_release_queue,
3903 int blk_register_queue(struct gendisk *disk)
3905 int ret;
3907 request_queue_t *q = disk->queue;
3909 if (!q || !q->request_fn)
3910 return -ENXIO;
3912 q->kobj.parent = kobject_get(&disk->kobj);
3914 ret = kobject_add(&q->kobj);
3915 if (ret < 0)
3916 return ret;
3918 kobject_uevent(&q->kobj, KOBJ_ADD);
3920 ret = elv_register_queue(q);
3921 if (ret) {
3922 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3923 kobject_del(&q->kobj);
3924 return ret;
3927 return 0;
3930 void blk_unregister_queue(struct gendisk *disk)
3932 request_queue_t *q = disk->queue;
3934 if (q && q->request_fn) {
3935 elv_unregister_queue(q);
3937 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3938 kobject_del(&q->kobj);
3939 kobject_put(&disk->kobj);