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
11 * This handles all read/write requests to block devices
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/backing-dev.h>
16 #include <linux/bio.h>
17 #include <linux/blkdev.h>
18 #include <linux/highmem.h>
20 #include <linux/kernel_stat.h>
21 #include <linux/string.h>
22 #include <linux/init.h>
23 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
24 #include <linux/completion.h>
25 #include <linux/slab.h>
26 #include <linux/swap.h>
27 #include <linux/writeback.h>
28 #include <linux/interrupt.h>
29 #include <linux/cpu.h>
30 #include <linux/blktrace_api.h>
35 #include <scsi/scsi_cmnd.h>
37 static void blk_unplug_work(void *data);
38 static void blk_unplug_timeout(unsigned long data);
39 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io);
40 static void init_request_from_bio(struct request *req, struct bio *bio);
41 static int __make_request(request_queue_t *q, struct bio *bio);
44 * For the allocated request tables
46 static kmem_cache_t *request_cachep;
49 * For queue allocation
51 static kmem_cache_t *requestq_cachep;
54 * For io context allocations
56 static kmem_cache_t *iocontext_cachep;
58 static wait_queue_head_t congestion_wqh[2] = {
59 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
60 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
64 * Controlling structure to kblockd
66 static struct workqueue_struct *kblockd_workqueue;
68 unsigned long blk_max_low_pfn, blk_max_pfn;
70 EXPORT_SYMBOL(blk_max_low_pfn);
71 EXPORT_SYMBOL(blk_max_pfn);
73 static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
75 /* Amount of time in which a process may batch requests */
76 #define BLK_BATCH_TIME (HZ/50UL)
78 /* Number of requests a "batching" process may submit */
79 #define BLK_BATCH_REQ 32
82 * Return the threshold (number of used requests) at which the queue is
83 * considered to be congested. It include a little hysteresis to keep the
84 * context switch rate down.
86 static inline int queue_congestion_on_threshold(struct request_queue *q)
88 return q->nr_congestion_on;
92 * The threshold at which a queue is considered to be uncongested
94 static inline int queue_congestion_off_threshold(struct request_queue *q)
96 return q->nr_congestion_off;
99 static void blk_queue_congestion_threshold(struct request_queue *q)
103 nr = q->nr_requests - (q->nr_requests / 8) + 1;
104 if (nr > q->nr_requests)
106 q->nr_congestion_on = nr;
108 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
111 q->nr_congestion_off = nr;
115 * A queue has just exitted congestion. Note this in the global counter of
116 * congested queues, and wake up anyone who was waiting for requests to be
119 static void clear_queue_congested(request_queue_t *q, int rw)
122 wait_queue_head_t *wqh = &congestion_wqh[rw];
124 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
125 clear_bit(bit, &q->backing_dev_info.state);
126 smp_mb__after_clear_bit();
127 if (waitqueue_active(wqh))
132 * A queue has just entered congestion. Flag that in the queue's VM-visible
133 * state flags and increment the global gounter of congested queues.
135 static void set_queue_congested(request_queue_t *q, int rw)
139 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
140 set_bit(bit, &q->backing_dev_info.state);
144 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
147 * Locates the passed device's request queue and returns the address of its
150 * Will return NULL if the request queue cannot be located.
152 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
154 struct backing_dev_info *ret = NULL;
155 request_queue_t *q = bdev_get_queue(bdev);
158 ret = &q->backing_dev_info;
162 EXPORT_SYMBOL(blk_get_backing_dev_info);
164 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
167 q->activity_data = data;
170 EXPORT_SYMBOL(blk_queue_activity_fn);
173 * blk_queue_prep_rq - set a prepare_request function for queue
175 * @pfn: prepare_request function
177 * It's possible for a queue to register a prepare_request callback which
178 * is invoked before the request is handed to the request_fn. The goal of
179 * the function is to prepare a request for I/O, it can be used to build a
180 * cdb from the request data for instance.
183 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
188 EXPORT_SYMBOL(blk_queue_prep_rq);
191 * blk_queue_merge_bvec - set a merge_bvec function for queue
193 * @mbfn: merge_bvec_fn
195 * Usually queues have static limitations on the max sectors or segments that
196 * we can put in a request. Stacking drivers may have some settings that
197 * are dynamic, and thus we have to query the queue whether it is ok to
198 * add a new bio_vec to a bio at a given offset or not. If the block device
199 * has such limitations, it needs to register a merge_bvec_fn to control
200 * the size of bio's sent to it. Note that a block device *must* allow a
201 * single page to be added to an empty bio. The block device driver may want
202 * to use the bio_split() function to deal with these bio's. By default
203 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
206 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
208 q->merge_bvec_fn = mbfn;
211 EXPORT_SYMBOL(blk_queue_merge_bvec);
213 void blk_queue_softirq_done(request_queue_t *q, softirq_done_fn *fn)
215 q->softirq_done_fn = fn;
218 EXPORT_SYMBOL(blk_queue_softirq_done);
221 * blk_queue_make_request - define an alternate make_request function for a device
222 * @q: the request queue for the device to be affected
223 * @mfn: the alternate make_request function
226 * The normal way for &struct bios to be passed to a device
227 * driver is for them to be collected into requests on a request
228 * queue, and then to allow the device driver to select requests
229 * off that queue when it is ready. This works well for many block
230 * devices. However some block devices (typically virtual devices
231 * such as md or lvm) do not benefit from the processing on the
232 * request queue, and are served best by having the requests passed
233 * directly to them. This can be achieved by providing a function
234 * to blk_queue_make_request().
237 * The driver that does this *must* be able to deal appropriately
238 * with buffers in "highmemory". This can be accomplished by either calling
239 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
240 * blk_queue_bounce() to create a buffer in normal memory.
242 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
247 q->nr_requests = BLKDEV_MAX_RQ;
248 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
249 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
250 q->make_request_fn = mfn;
251 q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
252 q->backing_dev_info.state = 0;
253 q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
254 blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
255 blk_queue_hardsect_size(q, 512);
256 blk_queue_dma_alignment(q, 511);
257 blk_queue_congestion_threshold(q);
258 q->nr_batching = BLK_BATCH_REQ;
260 q->unplug_thresh = 4; /* hmm */
261 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
262 if (q->unplug_delay == 0)
265 INIT_WORK(&q->unplug_work, blk_unplug_work, q);
267 q->unplug_timer.function = blk_unplug_timeout;
268 q->unplug_timer.data = (unsigned long)q;
271 * by default assume old behaviour and bounce for any highmem page
273 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
275 blk_queue_activity_fn(q, NULL, NULL);
278 EXPORT_SYMBOL(blk_queue_make_request);
280 static inline void rq_init(request_queue_t *q, struct request *rq)
282 INIT_LIST_HEAD(&rq->queuelist);
283 INIT_LIST_HEAD(&rq->donelist);
286 rq->rq_status = RQ_ACTIVE;
287 rq->bio = rq->biotail = NULL;
288 INIT_HLIST_NODE(&rq->hash);
289 RB_CLEAR_NODE(&rq->rb_node);
298 rq->nr_phys_segments = 0;
301 rq->end_io_data = NULL;
302 rq->completion_data = NULL;
306 * blk_queue_ordered - does this queue support ordered writes
307 * @q: the request queue
308 * @ordered: one of QUEUE_ORDERED_*
309 * @prepare_flush_fn: rq setup helper for cache flush ordered writes
312 * For journalled file systems, doing ordered writes on a commit
313 * block instead of explicitly doing wait_on_buffer (which is bad
314 * for performance) can be a big win. Block drivers supporting this
315 * feature should call this function and indicate so.
318 int blk_queue_ordered(request_queue_t *q, unsigned ordered,
319 prepare_flush_fn *prepare_flush_fn)
321 if (ordered & (QUEUE_ORDERED_PREFLUSH | QUEUE_ORDERED_POSTFLUSH) &&
322 prepare_flush_fn == NULL) {
323 printk(KERN_ERR "blk_queue_ordered: prepare_flush_fn required\n");
327 if (ordered != QUEUE_ORDERED_NONE &&
328 ordered != QUEUE_ORDERED_DRAIN &&
329 ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
330 ordered != QUEUE_ORDERED_DRAIN_FUA &&
331 ordered != QUEUE_ORDERED_TAG &&
332 ordered != QUEUE_ORDERED_TAG_FLUSH &&
333 ordered != QUEUE_ORDERED_TAG_FUA) {
334 printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
338 q->ordered = ordered;
339 q->next_ordered = ordered;
340 q->prepare_flush_fn = prepare_flush_fn;
345 EXPORT_SYMBOL(blk_queue_ordered);
348 * blk_queue_issue_flush_fn - set function for issuing a flush
349 * @q: the request queue
350 * @iff: the function to be called issuing the flush
353 * If a driver supports issuing a flush command, the support is notified
354 * to the block layer by defining it through this call.
357 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
359 q->issue_flush_fn = iff;
362 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
365 * Cache flushing for ordered writes handling
367 inline unsigned blk_ordered_cur_seq(request_queue_t *q)
371 return 1 << ffz(q->ordseq);
374 unsigned blk_ordered_req_seq(struct request *rq)
376 request_queue_t *q = rq->q;
378 BUG_ON(q->ordseq == 0);
380 if (rq == &q->pre_flush_rq)
381 return QUEUE_ORDSEQ_PREFLUSH;
382 if (rq == &q->bar_rq)
383 return QUEUE_ORDSEQ_BAR;
384 if (rq == &q->post_flush_rq)
385 return QUEUE_ORDSEQ_POSTFLUSH;
387 if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
388 (q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
389 return QUEUE_ORDSEQ_DRAIN;
391 return QUEUE_ORDSEQ_DONE;
394 void blk_ordered_complete_seq(request_queue_t *q, unsigned seq, int error)
399 if (error && !q->orderr)
402 BUG_ON(q->ordseq & seq);
405 if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
409 * Okay, sequence complete.
412 uptodate = q->orderr ? q->orderr : 1;
416 end_that_request_first(rq, uptodate, rq->hard_nr_sectors);
417 end_that_request_last(rq, uptodate);
420 static void pre_flush_end_io(struct request *rq, int error)
422 elv_completed_request(rq->q, rq);
423 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
426 static void bar_end_io(struct request *rq, int error)
428 elv_completed_request(rq->q, rq);
429 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
432 static void post_flush_end_io(struct request *rq, int error)
434 elv_completed_request(rq->q, rq);
435 blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
438 static void queue_flush(request_queue_t *q, unsigned which)
441 rq_end_io_fn *end_io;
443 if (which == QUEUE_ORDERED_PREFLUSH) {
444 rq = &q->pre_flush_rq;
445 end_io = pre_flush_end_io;
447 rq = &q->post_flush_rq;
448 end_io = post_flush_end_io;
451 rq->cmd_flags = REQ_HARDBARRIER;
453 rq->elevator_private = NULL;
454 rq->rq_disk = q->bar_rq.rq_disk;
457 q->prepare_flush_fn(q, rq);
459 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
462 static inline struct request *start_ordered(request_queue_t *q,
467 q->ordered = q->next_ordered;
468 q->ordseq |= QUEUE_ORDSEQ_STARTED;
471 * Prep proxy barrier request.
473 blkdev_dequeue_request(rq);
478 if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
479 rq->cmd_flags |= REQ_RW;
480 rq->cmd_flags |= q->ordered & QUEUE_ORDERED_FUA ? REQ_FUA : 0;
481 rq->elevator_private = NULL;
483 init_request_from_bio(rq, q->orig_bar_rq->bio);
484 rq->end_io = bar_end_io;
487 * Queue ordered sequence. As we stack them at the head, we
488 * need to queue in reverse order. Note that we rely on that
489 * no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
490 * request gets inbetween ordered sequence.
492 if (q->ordered & QUEUE_ORDERED_POSTFLUSH)
493 queue_flush(q, QUEUE_ORDERED_POSTFLUSH);
495 q->ordseq |= QUEUE_ORDSEQ_POSTFLUSH;
497 elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
499 if (q->ordered & QUEUE_ORDERED_PREFLUSH) {
500 queue_flush(q, QUEUE_ORDERED_PREFLUSH);
501 rq = &q->pre_flush_rq;
503 q->ordseq |= QUEUE_ORDSEQ_PREFLUSH;
505 if ((q->ordered & QUEUE_ORDERED_TAG) || q->in_flight == 0)
506 q->ordseq |= QUEUE_ORDSEQ_DRAIN;
513 int blk_do_ordered(request_queue_t *q, struct request **rqp)
515 struct request *rq = *rqp;
516 int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
522 if (q->next_ordered != QUEUE_ORDERED_NONE) {
523 *rqp = start_ordered(q, rq);
527 * This can happen when the queue switches to
528 * ORDERED_NONE while this request is on it.
530 blkdev_dequeue_request(rq);
531 end_that_request_first(rq, -EOPNOTSUPP,
532 rq->hard_nr_sectors);
533 end_that_request_last(rq, -EOPNOTSUPP);
540 * Ordered sequence in progress
543 /* Special requests are not subject to ordering rules. */
544 if (!blk_fs_request(rq) &&
545 rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
548 if (q->ordered & QUEUE_ORDERED_TAG) {
549 /* Ordered by tag. Blocking the next barrier is enough. */
550 if (is_barrier && rq != &q->bar_rq)
553 /* Ordered by draining. Wait for turn. */
554 WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
555 if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
562 static int flush_dry_bio_endio(struct bio *bio, unsigned int bytes, int error)
564 request_queue_t *q = bio->bi_private;
565 struct bio_vec *bvec;
569 * This is dry run, restore bio_sector and size. We'll finish
570 * this request again with the original bi_end_io after an
571 * error occurs or post flush is complete.
580 bio_for_each_segment(bvec, bio, i) {
581 bvec->bv_len += bvec->bv_offset;
586 set_bit(BIO_UPTODATE, &bio->bi_flags);
587 bio->bi_size = q->bi_size;
588 bio->bi_sector -= (q->bi_size >> 9);
594 static inline int ordered_bio_endio(struct request *rq, struct bio *bio,
595 unsigned int nbytes, int error)
597 request_queue_t *q = rq->q;
601 if (&q->bar_rq != rq)
605 * Okay, this is the barrier request in progress, dry finish it.
607 if (error && !q->orderr)
610 endio = bio->bi_end_io;
611 private = bio->bi_private;
612 bio->bi_end_io = flush_dry_bio_endio;
615 bio_endio(bio, nbytes, error);
617 bio->bi_end_io = endio;
618 bio->bi_private = private;
624 * blk_queue_bounce_limit - set bounce buffer limit for queue
625 * @q: the request queue for the device
626 * @dma_addr: bus address limit
629 * Different hardware can have different requirements as to what pages
630 * it can do I/O directly to. A low level driver can call
631 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
632 * buffers for doing I/O to pages residing above @page.
634 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
636 unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
639 q->bounce_gfp = GFP_NOIO;
640 #if BITS_PER_LONG == 64
641 /* Assume anything <= 4GB can be handled by IOMMU.
642 Actually some IOMMUs can handle everything, but I don't
643 know of a way to test this here. */
644 if (bounce_pfn < (min_t(u64,0xffffffff,BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
646 q->bounce_pfn = max_low_pfn;
648 if (bounce_pfn < blk_max_low_pfn)
650 q->bounce_pfn = bounce_pfn;
653 init_emergency_isa_pool();
654 q->bounce_gfp = GFP_NOIO | GFP_DMA;
655 q->bounce_pfn = bounce_pfn;
659 EXPORT_SYMBOL(blk_queue_bounce_limit);
662 * blk_queue_max_sectors - set max sectors for a request for this queue
663 * @q: the request queue for the device
664 * @max_sectors: max sectors in the usual 512b unit
667 * Enables a low level driver to set an upper limit on the size of
670 void blk_queue_max_sectors(request_queue_t *q, unsigned int max_sectors)
672 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
673 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
674 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
677 if (BLK_DEF_MAX_SECTORS > max_sectors)
678 q->max_hw_sectors = q->max_sectors = max_sectors;
680 q->max_sectors = BLK_DEF_MAX_SECTORS;
681 q->max_hw_sectors = max_sectors;
685 EXPORT_SYMBOL(blk_queue_max_sectors);
688 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
689 * @q: the request queue for the device
690 * @max_segments: max number of segments
693 * Enables a low level driver to set an upper limit on the number of
694 * physical data segments in a request. This would be the largest sized
695 * scatter list the driver could handle.
697 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
701 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
704 q->max_phys_segments = max_segments;
707 EXPORT_SYMBOL(blk_queue_max_phys_segments);
710 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
711 * @q: the request queue for the device
712 * @max_segments: max number of segments
715 * Enables a low level driver to set an upper limit on the number of
716 * hw data segments in a request. This would be the largest number of
717 * address/length pairs the host adapter can actually give as once
720 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
724 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
727 q->max_hw_segments = max_segments;
730 EXPORT_SYMBOL(blk_queue_max_hw_segments);
733 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
734 * @q: the request queue for the device
735 * @max_size: max size of segment in bytes
738 * Enables a low level driver to set an upper limit on the size of a
741 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
743 if (max_size < PAGE_CACHE_SIZE) {
744 max_size = PAGE_CACHE_SIZE;
745 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
748 q->max_segment_size = max_size;
751 EXPORT_SYMBOL(blk_queue_max_segment_size);
754 * blk_queue_hardsect_size - set hardware sector size for the queue
755 * @q: the request queue for the device
756 * @size: the hardware sector size, in bytes
759 * This should typically be set to the lowest possible sector size
760 * that the hardware can operate on (possible without reverting to
761 * even internal read-modify-write operations). Usually the default
762 * of 512 covers most hardware.
764 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
766 q->hardsect_size = size;
769 EXPORT_SYMBOL(blk_queue_hardsect_size);
772 * Returns the minimum that is _not_ zero, unless both are zero.
774 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
777 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
778 * @t: the stacking driver (top)
779 * @b: the underlying device (bottom)
781 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
783 /* zero is "infinity" */
784 t->max_sectors = min_not_zero(t->max_sectors,b->max_sectors);
785 t->max_hw_sectors = min_not_zero(t->max_hw_sectors,b->max_hw_sectors);
787 t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
788 t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
789 t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
790 t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
791 if (!test_bit(QUEUE_FLAG_CLUSTER, &b->queue_flags))
792 clear_bit(QUEUE_FLAG_CLUSTER, &t->queue_flags);
795 EXPORT_SYMBOL(blk_queue_stack_limits);
798 * blk_queue_segment_boundary - set boundary rules for segment merging
799 * @q: the request queue for the device
800 * @mask: the memory boundary mask
802 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
804 if (mask < PAGE_CACHE_SIZE - 1) {
805 mask = PAGE_CACHE_SIZE - 1;
806 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
809 q->seg_boundary_mask = mask;
812 EXPORT_SYMBOL(blk_queue_segment_boundary);
815 * blk_queue_dma_alignment - set dma length and memory alignment
816 * @q: the request queue for the device
817 * @mask: alignment mask
820 * set required memory and length aligment for direct dma transactions.
821 * this is used when buiding direct io requests for the queue.
824 void blk_queue_dma_alignment(request_queue_t *q, int mask)
826 q->dma_alignment = mask;
829 EXPORT_SYMBOL(blk_queue_dma_alignment);
832 * blk_queue_find_tag - find a request by its tag and queue
833 * @q: The request queue for the device
834 * @tag: The tag of the request
837 * Should be used when a device returns a tag and you want to match
840 * no locks need be held.
842 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
844 struct blk_queue_tag *bqt = q->queue_tags;
846 if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
849 return bqt->tag_index[tag];
852 EXPORT_SYMBOL(blk_queue_find_tag);
855 * __blk_free_tags - release a given set of tag maintenance info
856 * @bqt: the tag map to free
858 * Tries to free the specified @bqt@. Returns true if it was
859 * actually freed and false if there are still references using it
861 static int __blk_free_tags(struct blk_queue_tag *bqt)
865 retval = atomic_dec_and_test(&bqt->refcnt);
868 BUG_ON(!list_empty(&bqt->busy_list));
870 kfree(bqt->tag_index);
871 bqt->tag_index = NULL;
884 * __blk_queue_free_tags - release tag maintenance info
885 * @q: the request queue for the device
888 * blk_cleanup_queue() will take care of calling this function, if tagging
889 * has been used. So there's no need to call this directly.
891 static void __blk_queue_free_tags(request_queue_t *q)
893 struct blk_queue_tag *bqt = q->queue_tags;
898 __blk_free_tags(bqt);
900 q->queue_tags = NULL;
901 q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
906 * blk_free_tags - release a given set of tag maintenance info
907 * @bqt: the tag map to free
909 * For externally managed @bqt@ frees the map. Callers of this
910 * function must guarantee to have released all the queues that
911 * might have been using this tag map.
913 void blk_free_tags(struct blk_queue_tag *bqt)
915 if (unlikely(!__blk_free_tags(bqt)))
918 EXPORT_SYMBOL(blk_free_tags);
921 * blk_queue_free_tags - release tag maintenance info
922 * @q: the request queue for the device
925 * This is used to disabled tagged queuing to a device, yet leave
928 void blk_queue_free_tags(request_queue_t *q)
930 clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
933 EXPORT_SYMBOL(blk_queue_free_tags);
936 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
938 struct request **tag_index;
939 unsigned long *tag_map;
942 if (q && depth > q->nr_requests * 2) {
943 depth = q->nr_requests * 2;
944 printk(KERN_ERR "%s: adjusted depth to %d\n",
945 __FUNCTION__, depth);
948 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC);
952 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG;
953 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC);
957 tags->real_max_depth = depth;
958 tags->max_depth = depth;
959 tags->tag_index = tag_index;
960 tags->tag_map = tag_map;
968 static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
971 struct blk_queue_tag *tags;
973 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
977 if (init_tag_map(q, tags, depth))
980 INIT_LIST_HEAD(&tags->busy_list);
982 atomic_set(&tags->refcnt, 1);
990 * blk_init_tags - initialize the tag info for an external tag map
991 * @depth: the maximum queue depth supported
992 * @tags: the tag to use
994 struct blk_queue_tag *blk_init_tags(int depth)
996 return __blk_queue_init_tags(NULL, depth);
998 EXPORT_SYMBOL(blk_init_tags);
1001 * blk_queue_init_tags - initialize the queue tag info
1002 * @q: the request queue for the device
1003 * @depth: the maximum queue depth supported
1004 * @tags: the tag to use
1006 int blk_queue_init_tags(request_queue_t *q, int depth,
1007 struct blk_queue_tag *tags)
1011 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
1013 if (!tags && !q->queue_tags) {
1014 tags = __blk_queue_init_tags(q, depth);
1018 } else if (q->queue_tags) {
1019 if ((rc = blk_queue_resize_tags(q, depth)))
1021 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
1024 atomic_inc(&tags->refcnt);
1027 * assign it, all done
1029 q->queue_tags = tags;
1030 q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
1037 EXPORT_SYMBOL(blk_queue_init_tags);
1040 * blk_queue_resize_tags - change the queueing depth
1041 * @q: the request queue for the device
1042 * @new_depth: the new max command queueing depth
1045 * Must be called with the queue lock held.
1047 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
1049 struct blk_queue_tag *bqt = q->queue_tags;
1050 struct request **tag_index;
1051 unsigned long *tag_map;
1052 int max_depth, nr_ulongs;
1058 * if we already have large enough real_max_depth. just
1059 * adjust max_depth. *NOTE* as requests with tag value
1060 * between new_depth and real_max_depth can be in-flight, tag
1061 * map can not be shrunk blindly here.
1063 if (new_depth <= bqt->real_max_depth) {
1064 bqt->max_depth = new_depth;
1069 * Currently cannot replace a shared tag map with a new
1070 * one, so error out if this is the case
1072 if (atomic_read(&bqt->refcnt) != 1)
1076 * save the old state info, so we can copy it back
1078 tag_index = bqt->tag_index;
1079 tag_map = bqt->tag_map;
1080 max_depth = bqt->real_max_depth;
1082 if (init_tag_map(q, bqt, new_depth))
1085 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
1086 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG;
1087 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long));
1094 EXPORT_SYMBOL(blk_queue_resize_tags);
1097 * blk_queue_end_tag - end tag operations for a request
1098 * @q: the request queue for the device
1099 * @rq: the request that has completed
1102 * Typically called when end_that_request_first() returns 0, meaning
1103 * all transfers have been done for a request. It's important to call
1104 * this function before end_that_request_last(), as that will put the
1105 * request back on the free list thus corrupting the internal tag list.
1108 * queue lock must be held.
1110 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
1112 struct blk_queue_tag *bqt = q->queue_tags;
1117 if (unlikely(tag >= bqt->real_max_depth))
1119 * This can happen after tag depth has been reduced.
1120 * FIXME: how about a warning or info message here?
1124 if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
1125 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
1130 list_del_init(&rq->queuelist);
1131 rq->cmd_flags &= ~REQ_QUEUED;
1134 if (unlikely(bqt->tag_index[tag] == NULL))
1135 printk(KERN_ERR "%s: tag %d is missing\n",
1138 bqt->tag_index[tag] = NULL;
1142 EXPORT_SYMBOL(blk_queue_end_tag);
1145 * blk_queue_start_tag - find a free tag and assign it
1146 * @q: the request queue for the device
1147 * @rq: the block request that needs tagging
1150 * This can either be used as a stand-alone helper, or possibly be
1151 * assigned as the queue &prep_rq_fn (in which case &struct request
1152 * automagically gets a tag assigned). Note that this function
1153 * assumes that any type of request can be queued! if this is not
1154 * true for your device, you must check the request type before
1155 * calling this function. The request will also be removed from
1156 * the request queue, so it's the drivers responsibility to readd
1157 * it if it should need to be restarted for some reason.
1160 * queue lock must be held.
1162 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
1164 struct blk_queue_tag *bqt = q->queue_tags;
1167 if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
1169 "%s: request %p for device [%s] already tagged %d",
1171 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
1175 tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
1176 if (tag >= bqt->max_depth)
1179 __set_bit(tag, bqt->tag_map);
1181 rq->cmd_flags |= REQ_QUEUED;
1183 bqt->tag_index[tag] = rq;
1184 blkdev_dequeue_request(rq);
1185 list_add(&rq->queuelist, &bqt->busy_list);
1190 EXPORT_SYMBOL(blk_queue_start_tag);
1193 * blk_queue_invalidate_tags - invalidate all pending tags
1194 * @q: the request queue for the device
1197 * Hardware conditions may dictate a need to stop all pending requests.
1198 * In this case, we will safely clear the block side of the tag queue and
1199 * readd all requests to the request queue in the right order.
1202 * queue lock must be held.
1204 void blk_queue_invalidate_tags(request_queue_t *q)
1206 struct blk_queue_tag *bqt = q->queue_tags;
1207 struct list_head *tmp, *n;
1210 list_for_each_safe(tmp, n, &bqt->busy_list) {
1211 rq = list_entry_rq(tmp);
1213 if (rq->tag == -1) {
1215 "%s: bad tag found on list\n", __FUNCTION__);
1216 list_del_init(&rq->queuelist);
1217 rq->cmd_flags &= ~REQ_QUEUED;
1219 blk_queue_end_tag(q, rq);
1221 rq->cmd_flags &= ~REQ_STARTED;
1222 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1226 EXPORT_SYMBOL(blk_queue_invalidate_tags);
1228 void blk_dump_rq_flags(struct request *rq, char *msg)
1232 printk("%s: dev %s: type=%x, flags=%x\n", msg,
1233 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
1236 printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
1238 rq->current_nr_sectors);
1239 printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
1241 if (blk_pc_request(rq)) {
1243 for (bit = 0; bit < sizeof(rq->cmd); bit++)
1244 printk("%02x ", rq->cmd[bit]);
1249 EXPORT_SYMBOL(blk_dump_rq_flags);
1251 void blk_recount_segments(request_queue_t *q, struct bio *bio)
1253 struct bio_vec *bv, *bvprv = NULL;
1254 int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
1255 int high, highprv = 1;
1257 if (unlikely(!bio->bi_io_vec))
1260 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1261 hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
1262 bio_for_each_segment(bv, bio, i) {
1264 * the trick here is making sure that a high page is never
1265 * considered part of another segment, since that might
1266 * change with the bounce page.
1268 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
1269 if (high || highprv)
1270 goto new_hw_segment;
1272 if (seg_size + bv->bv_len > q->max_segment_size)
1274 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
1276 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
1278 if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
1279 goto new_hw_segment;
1281 seg_size += bv->bv_len;
1282 hw_seg_size += bv->bv_len;
1287 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
1288 !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
1289 hw_seg_size += bv->bv_len;
1292 if (hw_seg_size > bio->bi_hw_front_size)
1293 bio->bi_hw_front_size = hw_seg_size;
1294 hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
1300 seg_size = bv->bv_len;
1303 if (hw_seg_size > bio->bi_hw_back_size)
1304 bio->bi_hw_back_size = hw_seg_size;
1305 if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
1306 bio->bi_hw_front_size = hw_seg_size;
1307 bio->bi_phys_segments = nr_phys_segs;
1308 bio->bi_hw_segments = nr_hw_segs;
1309 bio->bi_flags |= (1 << BIO_SEG_VALID);
1313 static int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
1316 if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
1319 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
1321 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1325 * bio and nxt are contigous in memory, check if the queue allows
1326 * these two to be merged into one
1328 if (BIO_SEG_BOUNDARY(q, bio, nxt))
1334 static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
1337 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1338 blk_recount_segments(q, bio);
1339 if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
1340 blk_recount_segments(q, nxt);
1341 if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
1342 BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
1344 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
1351 * map a request to scatterlist, return number of sg entries setup. Caller
1352 * must make sure sg can hold rq->nr_phys_segments entries
1354 int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
1356 struct bio_vec *bvec, *bvprv;
1358 int nsegs, i, cluster;
1361 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1364 * for each bio in rq
1367 rq_for_each_bio(bio, rq) {
1369 * for each segment in bio
1371 bio_for_each_segment(bvec, bio, i) {
1372 int nbytes = bvec->bv_len;
1374 if (bvprv && cluster) {
1375 if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
1378 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
1380 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
1383 sg[nsegs - 1].length += nbytes;
1386 memset(&sg[nsegs],0,sizeof(struct scatterlist));
1387 sg[nsegs].page = bvec->bv_page;
1388 sg[nsegs].length = nbytes;
1389 sg[nsegs].offset = bvec->bv_offset;
1394 } /* segments in bio */
1400 EXPORT_SYMBOL(blk_rq_map_sg);
1403 * the standard queue merge functions, can be overridden with device
1404 * specific ones if so desired
1407 static inline int ll_new_mergeable(request_queue_t *q,
1408 struct request *req,
1411 int nr_phys_segs = bio_phys_segments(q, bio);
1413 if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1414 req->cmd_flags |= REQ_NOMERGE;
1415 if (req == q->last_merge)
1416 q->last_merge = NULL;
1421 * A hw segment is just getting larger, bump just the phys
1424 req->nr_phys_segments += nr_phys_segs;
1428 static inline int ll_new_hw_segment(request_queue_t *q,
1429 struct request *req,
1432 int nr_hw_segs = bio_hw_segments(q, bio);
1433 int nr_phys_segs = bio_phys_segments(q, bio);
1435 if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
1436 || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1437 req->cmd_flags |= REQ_NOMERGE;
1438 if (req == q->last_merge)
1439 q->last_merge = NULL;
1444 * This will form the start of a new hw segment. Bump both
1447 req->nr_hw_segments += nr_hw_segs;
1448 req->nr_phys_segments += nr_phys_segs;
1452 static int ll_back_merge_fn(request_queue_t *q, struct request *req,
1455 unsigned short max_sectors;
1458 if (unlikely(blk_pc_request(req)))
1459 max_sectors = q->max_hw_sectors;
1461 max_sectors = q->max_sectors;
1463 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1464 req->cmd_flags |= REQ_NOMERGE;
1465 if (req == q->last_merge)
1466 q->last_merge = NULL;
1469 if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
1470 blk_recount_segments(q, req->biotail);
1471 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1472 blk_recount_segments(q, bio);
1473 len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
1474 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
1475 !BIOVEC_VIRT_OVERSIZE(len)) {
1476 int mergeable = ll_new_mergeable(q, req, bio);
1479 if (req->nr_hw_segments == 1)
1480 req->bio->bi_hw_front_size = len;
1481 if (bio->bi_hw_segments == 1)
1482 bio->bi_hw_back_size = len;
1487 return ll_new_hw_segment(q, req, bio);
1490 static int ll_front_merge_fn(request_queue_t *q, struct request *req,
1493 unsigned short max_sectors;
1496 if (unlikely(blk_pc_request(req)))
1497 max_sectors = q->max_hw_sectors;
1499 max_sectors = q->max_sectors;
1502 if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
1503 req->cmd_flags |= REQ_NOMERGE;
1504 if (req == q->last_merge)
1505 q->last_merge = NULL;
1508 len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
1509 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1510 blk_recount_segments(q, bio);
1511 if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
1512 blk_recount_segments(q, req->bio);
1513 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
1514 !BIOVEC_VIRT_OVERSIZE(len)) {
1515 int mergeable = ll_new_mergeable(q, req, bio);
1518 if (bio->bi_hw_segments == 1)
1519 bio->bi_hw_front_size = len;
1520 if (req->nr_hw_segments == 1)
1521 req->biotail->bi_hw_back_size = len;
1526 return ll_new_hw_segment(q, req, bio);
1529 static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
1530 struct request *next)
1532 int total_phys_segments;
1533 int total_hw_segments;
1536 * First check if the either of the requests are re-queued
1537 * requests. Can't merge them if they are.
1539 if (req->special || next->special)
1543 * Will it become too large?
1545 if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
1548 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
1549 if (blk_phys_contig_segment(q, req->biotail, next->bio))
1550 total_phys_segments--;
1552 if (total_phys_segments > q->max_phys_segments)
1555 total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1556 if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
1557 int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
1559 * propagate the combined length to the end of the requests
1561 if (req->nr_hw_segments == 1)
1562 req->bio->bi_hw_front_size = len;
1563 if (next->nr_hw_segments == 1)
1564 next->biotail->bi_hw_back_size = len;
1565 total_hw_segments--;
1568 if (total_hw_segments > q->max_hw_segments)
1571 /* Merge is OK... */
1572 req->nr_phys_segments = total_phys_segments;
1573 req->nr_hw_segments = total_hw_segments;
1578 * "plug" the device if there are no outstanding requests: this will
1579 * force the transfer to start only after we have put all the requests
1582 * This is called with interrupts off and no requests on the queue and
1583 * with the queue lock held.
1585 void blk_plug_device(request_queue_t *q)
1587 WARN_ON(!irqs_disabled());
1590 * don't plug a stopped queue, it must be paired with blk_start_queue()
1591 * which will restart the queueing
1593 if (blk_queue_stopped(q))
1596 if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags)) {
1597 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
1598 blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG);
1602 EXPORT_SYMBOL(blk_plug_device);
1605 * remove the queue from the plugged list, if present. called with
1606 * queue lock held and interrupts disabled.
1608 int blk_remove_plug(request_queue_t *q)
1610 WARN_ON(!irqs_disabled());
1612 if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1615 del_timer(&q->unplug_timer);
1619 EXPORT_SYMBOL(blk_remove_plug);
1622 * remove the plug and let it rip..
1624 void __generic_unplug_device(request_queue_t *q)
1626 if (unlikely(blk_queue_stopped(q)))
1629 if (!blk_remove_plug(q))
1634 EXPORT_SYMBOL(__generic_unplug_device);
1637 * generic_unplug_device - fire a request queue
1638 * @q: The &request_queue_t in question
1641 * Linux uses plugging to build bigger requests queues before letting
1642 * the device have at them. If a queue is plugged, the I/O scheduler
1643 * is still adding and merging requests on the queue. Once the queue
1644 * gets unplugged, the request_fn defined for the queue is invoked and
1645 * transfers started.
1647 void generic_unplug_device(request_queue_t *q)
1649 spin_lock_irq(q->queue_lock);
1650 __generic_unplug_device(q);
1651 spin_unlock_irq(q->queue_lock);
1653 EXPORT_SYMBOL(generic_unplug_device);
1655 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1658 request_queue_t *q = bdi->unplug_io_data;
1661 * devices don't necessarily have an ->unplug_fn defined
1664 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1665 q->rq.count[READ] + q->rq.count[WRITE]);
1671 static void blk_unplug_work(void *data)
1673 request_queue_t *q = data;
1675 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL,
1676 q->rq.count[READ] + q->rq.count[WRITE]);
1681 static void blk_unplug_timeout(unsigned long data)
1683 request_queue_t *q = (request_queue_t *)data;
1685 blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_TIMER, NULL,
1686 q->rq.count[READ] + q->rq.count[WRITE]);
1688 kblockd_schedule_work(&q->unplug_work);
1692 * blk_start_queue - restart a previously stopped queue
1693 * @q: The &request_queue_t in question
1696 * blk_start_queue() will clear the stop flag on the queue, and call
1697 * the request_fn for the queue if it was in a stopped state when
1698 * entered. Also see blk_stop_queue(). Queue lock must be held.
1700 void blk_start_queue(request_queue_t *q)
1702 WARN_ON(!irqs_disabled());
1704 clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1707 * one level of recursion is ok and is much faster than kicking
1708 * the unplug handling
1710 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1712 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1715 kblockd_schedule_work(&q->unplug_work);
1719 EXPORT_SYMBOL(blk_start_queue);
1722 * blk_stop_queue - stop a queue
1723 * @q: The &request_queue_t in question
1726 * The Linux block layer assumes that a block driver will consume all
1727 * entries on the request queue when the request_fn strategy is called.
1728 * Often this will not happen, because of hardware limitations (queue
1729 * depth settings). If a device driver gets a 'queue full' response,
1730 * or if it simply chooses not to queue more I/O at one point, it can
1731 * call this function to prevent the request_fn from being called until
1732 * the driver has signalled it's ready to go again. This happens by calling
1733 * blk_start_queue() to restart queue operations. Queue lock must be held.
1735 void blk_stop_queue(request_queue_t *q)
1738 set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1740 EXPORT_SYMBOL(blk_stop_queue);
1743 * blk_sync_queue - cancel any pending callbacks on a queue
1747 * The block layer may perform asynchronous callback activity
1748 * on a queue, such as calling the unplug function after a timeout.
1749 * A block device may call blk_sync_queue to ensure that any
1750 * such activity is cancelled, thus allowing it to release resources
1751 * the the callbacks might use. The caller must already have made sure
1752 * that its ->make_request_fn will not re-add plugging prior to calling
1756 void blk_sync_queue(struct request_queue *q)
1758 del_timer_sync(&q->unplug_timer);
1761 EXPORT_SYMBOL(blk_sync_queue);
1764 * blk_run_queue - run a single device queue
1765 * @q: The queue to run
1767 void blk_run_queue(struct request_queue *q)
1769 unsigned long flags;
1771 spin_lock_irqsave(q->queue_lock, flags);
1775 * Only recurse once to avoid overrunning the stack, let the unplug
1776 * handling reinvoke the handler shortly if we already got there.
1778 if (!elv_queue_empty(q)) {
1779 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1781 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1784 kblockd_schedule_work(&q->unplug_work);
1788 spin_unlock_irqrestore(q->queue_lock, flags);
1790 EXPORT_SYMBOL(blk_run_queue);
1793 * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1794 * @kobj: the kobj belonging of the request queue to be released
1797 * blk_cleanup_queue is the pair to blk_init_queue() or
1798 * blk_queue_make_request(). It should be called when a request queue is
1799 * being released; typically when a block device is being de-registered.
1800 * Currently, its primary task it to free all the &struct request
1801 * structures that were allocated to the queue and the queue itself.
1804 * Hopefully the low level driver will have finished any
1805 * outstanding requests first...
1807 static void blk_release_queue(struct kobject *kobj)
1809 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
1810 struct request_list *rl = &q->rq;
1815 mempool_destroy(rl->rq_pool);
1818 __blk_queue_free_tags(q);
1820 blk_trace_shutdown(q);
1822 kmem_cache_free(requestq_cachep, q);
1825 void blk_put_queue(request_queue_t *q)
1827 kobject_put(&q->kobj);
1829 EXPORT_SYMBOL(blk_put_queue);
1831 void blk_cleanup_queue(request_queue_t * q)
1833 mutex_lock(&q->sysfs_lock);
1834 set_bit(QUEUE_FLAG_DEAD, &q->queue_flags);
1835 mutex_unlock(&q->sysfs_lock);
1838 elevator_exit(q->elevator);
1843 EXPORT_SYMBOL(blk_cleanup_queue);
1845 static int blk_init_free_list(request_queue_t *q)
1847 struct request_list *rl = &q->rq;
1849 rl->count[READ] = rl->count[WRITE] = 0;
1850 rl->starved[READ] = rl->starved[WRITE] = 0;
1852 init_waitqueue_head(&rl->wait[READ]);
1853 init_waitqueue_head(&rl->wait[WRITE]);
1855 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
1856 mempool_free_slab, request_cachep, q->node);
1864 request_queue_t *blk_alloc_queue(gfp_t gfp_mask)
1866 return blk_alloc_queue_node(gfp_mask, -1);
1868 EXPORT_SYMBOL(blk_alloc_queue);
1870 static struct kobj_type queue_ktype;
1872 request_queue_t *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
1876 q = kmem_cache_alloc_node(requestq_cachep, gfp_mask, node_id);
1880 memset(q, 0, sizeof(*q));
1881 init_timer(&q->unplug_timer);
1883 snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
1884 q->kobj.ktype = &queue_ktype;
1885 kobject_init(&q->kobj);
1887 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1888 q->backing_dev_info.unplug_io_data = q;
1890 mutex_init(&q->sysfs_lock);
1894 EXPORT_SYMBOL(blk_alloc_queue_node);
1897 * blk_init_queue - prepare a request queue for use with a block device
1898 * @rfn: The function to be called to process requests that have been
1899 * placed on the queue.
1900 * @lock: Request queue spin lock
1903 * If a block device wishes to use the standard request handling procedures,
1904 * which sorts requests and coalesces adjacent requests, then it must
1905 * call blk_init_queue(). The function @rfn will be called when there
1906 * are requests on the queue that need to be processed. If the device
1907 * supports plugging, then @rfn may not be called immediately when requests
1908 * are available on the queue, but may be called at some time later instead.
1909 * Plugged queues are generally unplugged when a buffer belonging to one
1910 * of the requests on the queue is needed, or due to memory pressure.
1912 * @rfn is not required, or even expected, to remove all requests off the
1913 * queue, but only as many as it can handle at a time. If it does leave
1914 * requests on the queue, it is responsible for arranging that the requests
1915 * get dealt with eventually.
1917 * The queue spin lock must be held while manipulating the requests on the
1918 * request queue; this lock will be taken also from interrupt context, so irq
1919 * disabling is needed for it.
1921 * Function returns a pointer to the initialized request queue, or NULL if
1922 * it didn't succeed.
1925 * blk_init_queue() must be paired with a blk_cleanup_queue() call
1926 * when the block device is deactivated (such as at module unload).
1929 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1931 return blk_init_queue_node(rfn, lock, -1);
1933 EXPORT_SYMBOL(blk_init_queue);
1936 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
1938 request_queue_t *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
1944 if (blk_init_free_list(q)) {
1945 kmem_cache_free(requestq_cachep, q);
1950 * if caller didn't supply a lock, they get per-queue locking with
1954 spin_lock_init(&q->__queue_lock);
1955 lock = &q->__queue_lock;
1958 q->request_fn = rfn;
1959 q->back_merge_fn = ll_back_merge_fn;
1960 q->front_merge_fn = ll_front_merge_fn;
1961 q->merge_requests_fn = ll_merge_requests_fn;
1962 q->prep_rq_fn = NULL;
1963 q->unplug_fn = generic_unplug_device;
1964 q->queue_flags = (1 << QUEUE_FLAG_CLUSTER);
1965 q->queue_lock = lock;
1967 blk_queue_segment_boundary(q, 0xffffffff);
1969 blk_queue_make_request(q, __make_request);
1970 blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1972 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1973 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1978 if (!elevator_init(q, NULL)) {
1979 blk_queue_congestion_threshold(q);
1986 EXPORT_SYMBOL(blk_init_queue_node);
1988 int blk_get_queue(request_queue_t *q)
1990 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
1991 kobject_get(&q->kobj);
1998 EXPORT_SYMBOL(blk_get_queue);
2000 static inline void blk_free_request(request_queue_t *q, struct request *rq)
2002 if (rq->cmd_flags & REQ_ELVPRIV)
2003 elv_put_request(q, rq);
2004 mempool_free(rq, q->rq.rq_pool);
2007 static inline struct request *
2008 blk_alloc_request(request_queue_t *q, int rw, struct bio *bio,
2009 int priv, gfp_t gfp_mask)
2011 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
2017 * first three bits are identical in rq->cmd_flags and bio->bi_rw,
2018 * see bio.h and blkdev.h
2023 if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
2024 mempool_free(rq, q->rq.rq_pool);
2027 rq->cmd_flags |= REQ_ELVPRIV;
2034 * ioc_batching returns true if the ioc is a valid batching request and
2035 * should be given priority access to a request.
2037 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
2043 * Make sure the process is able to allocate at least 1 request
2044 * even if the batch times out, otherwise we could theoretically
2047 return ioc->nr_batch_requests == q->nr_batching ||
2048 (ioc->nr_batch_requests > 0
2049 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
2053 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
2054 * will cause the process to be a "batcher" on all queues in the system. This
2055 * is the behaviour we want though - once it gets a wakeup it should be given
2058 static void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
2060 if (!ioc || ioc_batching(q, ioc))
2063 ioc->nr_batch_requests = q->nr_batching;
2064 ioc->last_waited = jiffies;
2067 static void __freed_request(request_queue_t *q, int rw)
2069 struct request_list *rl = &q->rq;
2071 if (rl->count[rw] < queue_congestion_off_threshold(q))
2072 clear_queue_congested(q, rw);
2074 if (rl->count[rw] + 1 <= q->nr_requests) {
2075 if (waitqueue_active(&rl->wait[rw]))
2076 wake_up(&rl->wait[rw]);
2078 blk_clear_queue_full(q, rw);
2083 * A request has just been released. Account for it, update the full and
2084 * congestion status, wake up any waiters. Called under q->queue_lock.
2086 static void freed_request(request_queue_t *q, int rw, int priv)
2088 struct request_list *rl = &q->rq;
2094 __freed_request(q, rw);
2096 if (unlikely(rl->starved[rw ^ 1]))
2097 __freed_request(q, rw ^ 1);
2100 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
2102 * Get a free request, queue_lock must be held.
2103 * Returns NULL on failure, with queue_lock held.
2104 * Returns !NULL on success, with queue_lock *not held*.
2106 static struct request *get_request(request_queue_t *q, int rw, struct bio *bio,
2109 struct request *rq = NULL;
2110 struct request_list *rl = &q->rq;
2111 struct io_context *ioc = NULL;
2112 int may_queue, priv;
2114 may_queue = elv_may_queue(q, rw, bio);
2115 if (may_queue == ELV_MQUEUE_NO)
2118 if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) {
2119 if (rl->count[rw]+1 >= q->nr_requests) {
2120 ioc = current_io_context(GFP_ATOMIC);
2122 * The queue will fill after this allocation, so set
2123 * it as full, and mark this process as "batching".
2124 * This process will be allowed to complete a batch of
2125 * requests, others will be blocked.
2127 if (!blk_queue_full(q, rw)) {
2128 ioc_set_batching(q, ioc);
2129 blk_set_queue_full(q, rw);
2131 if (may_queue != ELV_MQUEUE_MUST
2132 && !ioc_batching(q, ioc)) {
2134 * The queue is full and the allocating
2135 * process is not a "batcher", and not
2136 * exempted by the IO scheduler
2142 set_queue_congested(q, rw);
2146 * Only allow batching queuers to allocate up to 50% over the defined
2147 * limit of requests, otherwise we could have thousands of requests
2148 * allocated with any setting of ->nr_requests
2150 if (rl->count[rw] >= (3 * q->nr_requests / 2))
2154 rl->starved[rw] = 0;
2156 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
2160 spin_unlock_irq(q->queue_lock);
2162 rq = blk_alloc_request(q, rw, bio, priv, gfp_mask);
2163 if (unlikely(!rq)) {
2165 * Allocation failed presumably due to memory. Undo anything
2166 * we might have messed up.
2168 * Allocating task should really be put onto the front of the
2169 * wait queue, but this is pretty rare.
2171 spin_lock_irq(q->queue_lock);
2172 freed_request(q, rw, priv);
2175 * in the very unlikely event that allocation failed and no
2176 * requests for this direction was pending, mark us starved
2177 * so that freeing of a request in the other direction will
2178 * notice us. another possible fix would be to split the
2179 * rq mempool into READ and WRITE
2182 if (unlikely(rl->count[rw] == 0))
2183 rl->starved[rw] = 1;
2189 * ioc may be NULL here, and ioc_batching will be false. That's
2190 * OK, if the queue is under the request limit then requests need
2191 * not count toward the nr_batch_requests limit. There will always
2192 * be some limit enforced by BLK_BATCH_TIME.
2194 if (ioc_batching(q, ioc))
2195 ioc->nr_batch_requests--;
2200 blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ);
2206 * No available requests for this queue, unplug the device and wait for some
2207 * requests to become available.
2209 * Called with q->queue_lock held, and returns with it unlocked.
2211 static struct request *get_request_wait(request_queue_t *q, int rw,
2216 rq = get_request(q, rw, bio, GFP_NOIO);
2219 struct request_list *rl = &q->rq;
2221 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
2222 TASK_UNINTERRUPTIBLE);
2224 rq = get_request(q, rw, bio, GFP_NOIO);
2227 struct io_context *ioc;
2229 blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
2231 __generic_unplug_device(q);
2232 spin_unlock_irq(q->queue_lock);
2236 * After sleeping, we become a "batching" process and
2237 * will be able to allocate at least one request, and
2238 * up to a big batch of them for a small period time.
2239 * See ioc_batching, ioc_set_batching
2241 ioc = current_io_context(GFP_NOIO);
2242 ioc_set_batching(q, ioc);
2244 spin_lock_irq(q->queue_lock);
2246 finish_wait(&rl->wait[rw], &wait);
2252 struct request *blk_get_request(request_queue_t *q, int rw, gfp_t gfp_mask)
2256 BUG_ON(rw != READ && rw != WRITE);
2258 spin_lock_irq(q->queue_lock);
2259 if (gfp_mask & __GFP_WAIT) {
2260 rq = get_request_wait(q, rw, NULL);
2262 rq = get_request(q, rw, NULL, gfp_mask);
2264 spin_unlock_irq(q->queue_lock);
2266 /* q->queue_lock is unlocked at this point */
2270 EXPORT_SYMBOL(blk_get_request);
2273 * blk_requeue_request - put a request back on queue
2274 * @q: request queue where request should be inserted
2275 * @rq: request to be inserted
2278 * Drivers often keep queueing requests until the hardware cannot accept
2279 * more, when that condition happens we need to put the request back
2280 * on the queue. Must be called with queue lock held.
2282 void blk_requeue_request(request_queue_t *q, struct request *rq)
2284 blk_add_trace_rq(q, rq, BLK_TA_REQUEUE);
2286 if (blk_rq_tagged(rq))
2287 blk_queue_end_tag(q, rq);
2289 elv_requeue_request(q, rq);
2292 EXPORT_SYMBOL(blk_requeue_request);
2295 * blk_insert_request - insert a special request in to a request queue
2296 * @q: request queue where request should be inserted
2297 * @rq: request to be inserted
2298 * @at_head: insert request at head or tail of queue
2299 * @data: private data
2302 * Many block devices need to execute commands asynchronously, so they don't
2303 * block the whole kernel from preemption during request execution. This is
2304 * accomplished normally by inserting aritficial requests tagged as
2305 * REQ_SPECIAL in to the corresponding request queue, and letting them be
2306 * scheduled for actual execution by the request queue.
2308 * We have the option of inserting the head or the tail of the queue.
2309 * Typically we use the tail for new ioctls and so forth. We use the head
2310 * of the queue for things like a QUEUE_FULL message from a device, or a
2311 * host that is unable to accept a particular command.
2313 void blk_insert_request(request_queue_t *q, struct request *rq,
2314 int at_head, void *data)
2316 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2317 unsigned long flags;
2320 * tell I/O scheduler that this isn't a regular read/write (ie it
2321 * must not attempt merges on this) and that it acts as a soft
2324 rq->cmd_type = REQ_TYPE_SPECIAL;
2325 rq->cmd_flags |= REQ_SOFTBARRIER;
2329 spin_lock_irqsave(q->queue_lock, flags);
2332 * If command is tagged, release the tag
2334 if (blk_rq_tagged(rq))
2335 blk_queue_end_tag(q, rq);
2337 drive_stat_acct(rq, rq->nr_sectors, 1);
2338 __elv_add_request(q, rq, where, 0);
2340 if (blk_queue_plugged(q))
2341 __generic_unplug_device(q);
2344 spin_unlock_irqrestore(q->queue_lock, flags);
2347 EXPORT_SYMBOL(blk_insert_request);
2350 * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2351 * @q: request queue where request should be inserted
2352 * @rq: request structure to fill
2353 * @ubuf: the user buffer
2354 * @len: length of user data
2357 * Data will be mapped directly for zero copy io, if possible. Otherwise
2358 * a kernel bounce buffer is used.
2360 * A matching blk_rq_unmap_user() must be issued at the end of io, while
2361 * still in process context.
2363 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
2364 * before being submitted to the device, as pages mapped may be out of
2365 * reach. It's the callers responsibility to make sure this happens. The
2366 * original bio must be passed back in to blk_rq_unmap_user() for proper
2369 int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
2372 unsigned long uaddr;
2376 if (len > (q->max_hw_sectors << 9))
2381 reading = rq_data_dir(rq) == READ;
2384 * if alignment requirement is satisfied, map in user pages for
2385 * direct dma. else, set up kernel bounce buffers
2387 uaddr = (unsigned long) ubuf;
2388 if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
2389 bio = bio_map_user(q, NULL, uaddr, len, reading);
2391 bio = bio_copy_user(q, uaddr, len, reading);
2394 rq->bio = rq->biotail = bio;
2395 blk_rq_bio_prep(q, rq, bio);
2397 rq->buffer = rq->data = NULL;
2403 * bio is the err-ptr
2405 return PTR_ERR(bio);
2408 EXPORT_SYMBOL(blk_rq_map_user);
2411 * blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
2412 * @q: request queue where request should be inserted
2413 * @rq: request to map data to
2414 * @iov: pointer to the iovec
2415 * @iov_count: number of elements in the iovec
2418 * Data will be mapped directly for zero copy io, if possible. Otherwise
2419 * a kernel bounce buffer is used.
2421 * A matching blk_rq_unmap_user() must be issued at the end of io, while
2422 * still in process context.
2424 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
2425 * before being submitted to the device, as pages mapped may be out of
2426 * reach. It's the callers responsibility to make sure this happens. The
2427 * original bio must be passed back in to blk_rq_unmap_user() for proper
2430 int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
2431 struct sg_iovec *iov, int iov_count)
2435 if (!iov || iov_count <= 0)
2438 /* we don't allow misaligned data like bio_map_user() does. If the
2439 * user is using sg, they're expected to know the alignment constraints
2440 * and respect them accordingly */
2441 bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
2443 return PTR_ERR(bio);
2445 rq->bio = rq->biotail = bio;
2446 blk_rq_bio_prep(q, rq, bio);
2447 rq->buffer = rq->data = NULL;
2448 rq->data_len = bio->bi_size;
2452 EXPORT_SYMBOL(blk_rq_map_user_iov);
2455 * blk_rq_unmap_user - unmap a request with user data
2456 * @bio: bio to be unmapped
2457 * @ulen: length of user buffer
2460 * Unmap a bio previously mapped by blk_rq_map_user().
2462 int blk_rq_unmap_user(struct bio *bio, unsigned int ulen)
2467 if (bio_flagged(bio, BIO_USER_MAPPED))
2468 bio_unmap_user(bio);
2470 ret = bio_uncopy_user(bio);
2476 EXPORT_SYMBOL(blk_rq_unmap_user);
2479 * blk_rq_map_kern - map kernel data to a request, for REQ_BLOCK_PC usage
2480 * @q: request queue where request should be inserted
2481 * @rq: request to fill
2482 * @kbuf: the kernel buffer
2483 * @len: length of user data
2484 * @gfp_mask: memory allocation flags
2486 int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
2487 unsigned int len, gfp_t gfp_mask)
2491 if (len > (q->max_hw_sectors << 9))
2496 bio = bio_map_kern(q, kbuf, len, gfp_mask);
2498 return PTR_ERR(bio);
2500 if (rq_data_dir(rq) == WRITE)
2501 bio->bi_rw |= (1 << BIO_RW);
2503 rq->bio = rq->biotail = bio;
2504 blk_rq_bio_prep(q, rq, bio);
2506 rq->buffer = rq->data = NULL;
2511 EXPORT_SYMBOL(blk_rq_map_kern);
2514 * blk_execute_rq_nowait - insert a request into queue for execution
2515 * @q: queue to insert the request in
2516 * @bd_disk: matching gendisk
2517 * @rq: request to insert
2518 * @at_head: insert request at head or tail of queue
2519 * @done: I/O completion handler
2522 * Insert a fully prepared request at the back of the io scheduler queue
2523 * for execution. Don't wait for completion.
2525 void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
2526 struct request *rq, int at_head,
2529 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
2531 rq->rq_disk = bd_disk;
2532 rq->cmd_flags |= REQ_NOMERGE;
2534 WARN_ON(irqs_disabled());
2535 spin_lock_irq(q->queue_lock);
2536 __elv_add_request(q, rq, where, 1);
2537 __generic_unplug_device(q);
2538 spin_unlock_irq(q->queue_lock);
2540 EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
2543 * blk_execute_rq - insert a request into queue for execution
2544 * @q: queue to insert the request in
2545 * @bd_disk: matching gendisk
2546 * @rq: request to insert
2547 * @at_head: insert request at head or tail of queue
2550 * Insert a fully prepared request at the back of the io scheduler queue
2551 * for execution and wait for completion.
2553 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2554 struct request *rq, int at_head)
2556 DECLARE_COMPLETION_ONSTACK(wait);
2557 char sense[SCSI_SENSE_BUFFERSIZE];
2561 * we need an extra reference to the request, so we can look at
2562 * it after io completion
2567 memset(sense, 0, sizeof(sense));
2572 rq->waiting = &wait;
2573 blk_execute_rq_nowait(q, bd_disk, rq, at_head, blk_end_sync_rq);
2574 wait_for_completion(&wait);
2583 EXPORT_SYMBOL(blk_execute_rq);
2586 * blkdev_issue_flush - queue a flush
2587 * @bdev: blockdev to issue flush for
2588 * @error_sector: error sector
2591 * Issue a flush for the block device in question. Caller can supply
2592 * room for storing the error offset in case of a flush error, if they
2593 * wish to. Caller must run wait_for_completion() on its own.
2595 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2599 if (bdev->bd_disk == NULL)
2602 q = bdev_get_queue(bdev);
2605 if (!q->issue_flush_fn)
2608 return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2611 EXPORT_SYMBOL(blkdev_issue_flush);
2613 static void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2615 int rw = rq_data_dir(rq);
2617 if (!blk_fs_request(rq) || !rq->rq_disk)
2621 __disk_stat_inc(rq->rq_disk, merges[rw]);
2623 disk_round_stats(rq->rq_disk);
2624 rq->rq_disk->in_flight++;
2629 * add-request adds a request to the linked list.
2630 * queue lock is held and interrupts disabled, as we muck with the
2631 * request queue list.
2633 static inline void add_request(request_queue_t * q, struct request * req)
2635 drive_stat_acct(req, req->nr_sectors, 1);
2638 q->activity_fn(q->activity_data, rq_data_dir(req));
2641 * elevator indicated where it wants this request to be
2642 * inserted at elevator_merge time
2644 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2648 * disk_round_stats() - Round off the performance stats on a struct
2651 * The average IO queue length and utilisation statistics are maintained
2652 * by observing the current state of the queue length and the amount of
2653 * time it has been in this state for.
2655 * Normally, that accounting is done on IO completion, but that can result
2656 * in more than a second's worth of IO being accounted for within any one
2657 * second, leading to >100% utilisation. To deal with that, we call this
2658 * function to do a round-off before returning the results when reading
2659 * /proc/diskstats. This accounts immediately for all queue usage up to
2660 * the current jiffies and restarts the counters again.
2662 void disk_round_stats(struct gendisk *disk)
2664 unsigned long now = jiffies;
2666 if (now == disk->stamp)
2669 if (disk->in_flight) {
2670 __disk_stat_add(disk, time_in_queue,
2671 disk->in_flight * (now - disk->stamp));
2672 __disk_stat_add(disk, io_ticks, (now - disk->stamp));
2677 EXPORT_SYMBOL_GPL(disk_round_stats);
2680 * queue lock must be held
2682 void __blk_put_request(request_queue_t *q, struct request *req)
2684 struct request_list *rl = req->rl;
2688 if (unlikely(--req->ref_count))
2691 elv_completed_request(q, req);
2693 req->rq_status = RQ_INACTIVE;
2697 * Request may not have originated from ll_rw_blk. if not,
2698 * it didn't come out of our reserved rq pools
2701 int rw = rq_data_dir(req);
2702 int priv = req->cmd_flags & REQ_ELVPRIV;
2704 BUG_ON(!list_empty(&req->queuelist));
2705 BUG_ON(!hlist_unhashed(&req->hash));
2707 blk_free_request(q, req);
2708 freed_request(q, rw, priv);
2712 EXPORT_SYMBOL_GPL(__blk_put_request);
2714 void blk_put_request(struct request *req)
2716 unsigned long flags;
2717 request_queue_t *q = req->q;
2720 * Gee, IDE calls in w/ NULL q. Fix IDE and remove the
2721 * following if (q) test.
2724 spin_lock_irqsave(q->queue_lock, flags);
2725 __blk_put_request(q, req);
2726 spin_unlock_irqrestore(q->queue_lock, flags);
2730 EXPORT_SYMBOL(blk_put_request);
2733 * blk_end_sync_rq - executes a completion event on a request
2734 * @rq: request to complete
2735 * @error: end io status of the request
2737 void blk_end_sync_rq(struct request *rq, int error)
2739 struct completion *waiting = rq->waiting;
2742 __blk_put_request(rq->q, rq);
2745 * complete last, if this is a stack request the process (and thus
2746 * the rq pointer) could be invalid right after this complete()
2750 EXPORT_SYMBOL(blk_end_sync_rq);
2753 * blk_congestion_wait - wait for a queue to become uncongested
2754 * @rw: READ or WRITE
2755 * @timeout: timeout in jiffies
2757 * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2758 * If no queues are congested then just wait for the next request to be
2761 long blk_congestion_wait(int rw, long timeout)
2765 wait_queue_head_t *wqh = &congestion_wqh[rw];
2767 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2768 ret = io_schedule_timeout(timeout);
2769 finish_wait(wqh, &wait);
2773 EXPORT_SYMBOL(blk_congestion_wait);
2776 * blk_congestion_end - wake up sleepers on a congestion queue
2777 * @rw: READ or WRITE
2779 void blk_congestion_end(int rw)
2781 wait_queue_head_t *wqh = &congestion_wqh[rw];
2783 if (waitqueue_active(wqh))
2788 * Has to be called with the request spinlock acquired
2790 static int attempt_merge(request_queue_t *q, struct request *req,
2791 struct request *next)
2793 if (!rq_mergeable(req) || !rq_mergeable(next))
2799 if (req->sector + req->nr_sectors != next->sector)
2802 if (rq_data_dir(req) != rq_data_dir(next)
2803 || req->rq_disk != next->rq_disk
2804 || next->waiting || next->special)
2808 * If we are allowed to merge, then append bio list
2809 * from next to rq and release next. merge_requests_fn
2810 * will have updated segment counts, update sector
2813 if (!q->merge_requests_fn(q, req, next))
2817 * At this point we have either done a back merge
2818 * or front merge. We need the smaller start_time of
2819 * the merged requests to be the current request
2820 * for accounting purposes.
2822 if (time_after(req->start_time, next->start_time))
2823 req->start_time = next->start_time;
2825 req->biotail->bi_next = next->bio;
2826 req->biotail = next->biotail;
2828 req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2830 elv_merge_requests(q, req, next);
2833 disk_round_stats(req->rq_disk);
2834 req->rq_disk->in_flight--;
2837 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
2839 __blk_put_request(q, next);
2843 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2845 struct request *next = elv_latter_request(q, rq);
2848 return attempt_merge(q, rq, next);
2853 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2855 struct request *prev = elv_former_request(q, rq);
2858 return attempt_merge(q, prev, rq);
2863 static void init_request_from_bio(struct request *req, struct bio *bio)
2865 req->cmd_type = REQ_TYPE_FS;
2868 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2870 if (bio_rw_ahead(bio) || bio_failfast(bio))
2871 req->cmd_flags |= REQ_FAILFAST;
2874 * REQ_BARRIER implies no merging, but lets make it explicit
2876 if (unlikely(bio_barrier(bio)))
2877 req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2880 req->cmd_flags |= REQ_RW_SYNC;
2883 req->hard_sector = req->sector = bio->bi_sector;
2884 req->hard_nr_sectors = req->nr_sectors = bio_sectors(bio);
2885 req->current_nr_sectors = req->hard_cur_sectors = bio_cur_sectors(bio);
2886 req->nr_phys_segments = bio_phys_segments(req->q, bio);
2887 req->nr_hw_segments = bio_hw_segments(req->q, bio);
2888 req->buffer = bio_data(bio); /* see ->buffer comment above */
2889 req->waiting = NULL;
2890 req->bio = req->biotail = bio;
2891 req->ioprio = bio_prio(bio);
2892 req->rq_disk = bio->bi_bdev->bd_disk;
2893 req->start_time = jiffies;
2896 static int __make_request(request_queue_t *q, struct bio *bio)
2898 struct request *req;
2899 int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err, sync;
2900 unsigned short prio;
2903 sector = bio->bi_sector;
2904 nr_sectors = bio_sectors(bio);
2905 cur_nr_sectors = bio_cur_sectors(bio);
2906 prio = bio_prio(bio);
2908 rw = bio_data_dir(bio);
2909 sync = bio_sync(bio);
2912 * low level driver can indicate that it wants pages above a
2913 * certain limit bounced to low memory (ie for highmem, or even
2914 * ISA dma in theory)
2916 blk_queue_bounce(q, &bio);
2918 spin_lock_prefetch(q->queue_lock);
2920 barrier = bio_barrier(bio);
2921 if (unlikely(barrier) && (q->next_ordered == QUEUE_ORDERED_NONE)) {
2926 spin_lock_irq(q->queue_lock);
2928 if (unlikely(barrier) || elv_queue_empty(q))
2931 el_ret = elv_merge(q, &req, bio);
2933 case ELEVATOR_BACK_MERGE:
2934 BUG_ON(!rq_mergeable(req));
2936 if (!q->back_merge_fn(q, req, bio))
2939 blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE);
2941 req->biotail->bi_next = bio;
2943 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2944 req->ioprio = ioprio_best(req->ioprio, prio);
2945 drive_stat_acct(req, nr_sectors, 0);
2946 if (!attempt_back_merge(q, req))
2947 elv_merged_request(q, req, el_ret);
2950 case ELEVATOR_FRONT_MERGE:
2951 BUG_ON(!rq_mergeable(req));
2953 if (!q->front_merge_fn(q, req, bio))
2956 blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE);
2958 bio->bi_next = req->bio;
2962 * may not be valid. if the low level driver said
2963 * it didn't need a bounce buffer then it better
2964 * not touch req->buffer either...
2966 req->buffer = bio_data(bio);
2967 req->current_nr_sectors = cur_nr_sectors;
2968 req->hard_cur_sectors = cur_nr_sectors;
2969 req->sector = req->hard_sector = sector;
2970 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2971 req->ioprio = ioprio_best(req->ioprio, prio);
2972 drive_stat_acct(req, nr_sectors, 0);
2973 if (!attempt_front_merge(q, req))
2974 elv_merged_request(q, req, el_ret);
2977 /* ELV_NO_MERGE: elevator says don't/can't merge. */
2984 * Grab a free request. This is might sleep but can not fail.
2985 * Returns with the queue unlocked.
2987 req = get_request_wait(q, rw, bio);
2990 * After dropping the lock and possibly sleeping here, our request
2991 * may now be mergeable after it had proven unmergeable (above).
2992 * We don't worry about that case for efficiency. It won't happen
2993 * often, and the elevators are able to handle it.
2995 init_request_from_bio(req, bio);
2997 spin_lock_irq(q->queue_lock);
2998 if (elv_queue_empty(q))
3000 add_request(q, req);
3003 __generic_unplug_device(q);
3005 spin_unlock_irq(q->queue_lock);
3009 bio_endio(bio, nr_sectors << 9, err);
3014 * If bio->bi_dev is a partition, remap the location
3016 static inline void blk_partition_remap(struct bio *bio)
3018 struct block_device *bdev = bio->bi_bdev;
3020 if (bdev != bdev->bd_contains) {
3021 struct hd_struct *p = bdev->bd_part;
3022 const int rw = bio_data_dir(bio);
3024 p->sectors[rw] += bio_sectors(bio);
3027 bio->bi_sector += p->start_sect;
3028 bio->bi_bdev = bdev->bd_contains;
3032 static void handle_bad_sector(struct bio *bio)
3034 char b[BDEVNAME_SIZE];
3036 printk(KERN_INFO "attempt to access beyond end of device\n");
3037 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
3038 bdevname(bio->bi_bdev, b),
3040 (unsigned long long)bio->bi_sector + bio_sectors(bio),
3041 (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
3043 set_bit(BIO_EOF, &bio->bi_flags);
3047 * generic_make_request: hand a buffer to its device driver for I/O
3048 * @bio: The bio describing the location in memory and on the device.
3050 * generic_make_request() is used to make I/O requests of block
3051 * devices. It is passed a &struct bio, which describes the I/O that needs
3054 * generic_make_request() does not return any status. The
3055 * success/failure status of the request, along with notification of
3056 * completion, is delivered asynchronously through the bio->bi_end_io
3057 * function described (one day) else where.
3059 * The caller of generic_make_request must make sure that bi_io_vec
3060 * are set to describe the memory buffer, and that bi_dev and bi_sector are
3061 * set to describe the device address, and the
3062 * bi_end_io and optionally bi_private are set to describe how
3063 * completion notification should be signaled.
3065 * generic_make_request and the drivers it calls may use bi_next if this
3066 * bio happens to be merged with someone else, and may change bi_dev and
3067 * bi_sector for remaps as it sees fit. So the values of these fields
3068 * should NOT be depended on after the call to generic_make_request.
3070 void generic_make_request(struct bio *bio)
3074 int ret, nr_sectors = bio_sectors(bio);
3078 /* Test device or partition size, when known. */
3079 maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
3081 sector_t sector = bio->bi_sector;
3083 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
3085 * This may well happen - the kernel calls bread()
3086 * without checking the size of the device, e.g., when
3087 * mounting a device.
3089 handle_bad_sector(bio);
3095 * Resolve the mapping until finished. (drivers are
3096 * still free to implement/resolve their own stacking
3097 * by explicitly returning 0)
3099 * NOTE: we don't repeat the blk_size check for each new device.
3100 * Stacking drivers are expected to know what they are doing.
3105 char b[BDEVNAME_SIZE];
3107 q = bdev_get_queue(bio->bi_bdev);
3110 "generic_make_request: Trying to access "
3111 "nonexistent block-device %s (%Lu)\n",
3112 bdevname(bio->bi_bdev, b),
3113 (long long) bio->bi_sector);
3115 bio_endio(bio, bio->bi_size, -EIO);
3119 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
3120 printk("bio too big device %s (%u > %u)\n",
3121 bdevname(bio->bi_bdev, b),
3127 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
3131 * If this device has partitions, remap block n
3132 * of partition p to block n+start(p) of the disk.
3134 blk_partition_remap(bio);
3136 if (maxsector != -1)
3137 blk_add_trace_remap(q, bio, old_dev, bio->bi_sector,
3140 blk_add_trace_bio(q, bio, BLK_TA_QUEUE);
3142 maxsector = bio->bi_sector;
3143 old_dev = bio->bi_bdev->bd_dev;
3145 ret = q->make_request_fn(q, bio);
3149 EXPORT_SYMBOL(generic_make_request);
3152 * submit_bio: submit a bio to the block device layer for I/O
3153 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
3154 * @bio: The &struct bio which describes the I/O
3156 * submit_bio() is very similar in purpose to generic_make_request(), and
3157 * uses that function to do most of the work. Both are fairly rough
3158 * interfaces, @bio must be presetup and ready for I/O.
3161 void submit_bio(int rw, struct bio *bio)
3163 int count = bio_sectors(bio);
3165 BIO_BUG_ON(!bio->bi_size);
3166 BIO_BUG_ON(!bio->bi_io_vec);
3169 count_vm_events(PGPGOUT, count);
3171 count_vm_events(PGPGIN, count);
3173 if (unlikely(block_dump)) {
3174 char b[BDEVNAME_SIZE];
3175 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
3176 current->comm, current->pid,
3177 (rw & WRITE) ? "WRITE" : "READ",
3178 (unsigned long long)bio->bi_sector,
3179 bdevname(bio->bi_bdev,b));
3182 generic_make_request(bio);
3185 EXPORT_SYMBOL(submit_bio);
3187 static void blk_recalc_rq_segments(struct request *rq)
3189 struct bio *bio, *prevbio = NULL;
3190 int nr_phys_segs, nr_hw_segs;
3191 unsigned int phys_size, hw_size;
3192 request_queue_t *q = rq->q;
3197 phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
3198 rq_for_each_bio(bio, rq) {
3199 /* Force bio hw/phys segs to be recalculated. */
3200 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
3202 nr_phys_segs += bio_phys_segments(q, bio);
3203 nr_hw_segs += bio_hw_segments(q, bio);
3205 int pseg = phys_size + prevbio->bi_size + bio->bi_size;
3206 int hseg = hw_size + prevbio->bi_size + bio->bi_size;
3208 if (blk_phys_contig_segment(q, prevbio, bio) &&
3209 pseg <= q->max_segment_size) {
3211 phys_size += prevbio->bi_size + bio->bi_size;
3215 if (blk_hw_contig_segment(q, prevbio, bio) &&
3216 hseg <= q->max_segment_size) {
3218 hw_size += prevbio->bi_size + bio->bi_size;
3225 rq->nr_phys_segments = nr_phys_segs;
3226 rq->nr_hw_segments = nr_hw_segs;
3229 static void blk_recalc_rq_sectors(struct request *rq, int nsect)
3231 if (blk_fs_request(rq)) {
3232 rq->hard_sector += nsect;
3233 rq->hard_nr_sectors -= nsect;
3236 * Move the I/O submission pointers ahead if required.
3238 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
3239 (rq->sector <= rq->hard_sector)) {
3240 rq->sector = rq->hard_sector;
3241 rq->nr_sectors = rq->hard_nr_sectors;
3242 rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
3243 rq->current_nr_sectors = rq->hard_cur_sectors;
3244 rq->buffer = bio_data(rq->bio);
3248 * if total number of sectors is less than the first segment
3249 * size, something has gone terribly wrong
3251 if (rq->nr_sectors < rq->current_nr_sectors) {
3252 printk("blk: request botched\n");
3253 rq->nr_sectors = rq->current_nr_sectors;
3258 static int __end_that_request_first(struct request *req, int uptodate,
3261 int total_bytes, bio_nbytes, error, next_idx = 0;
3264 blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE);
3267 * extend uptodate bool to allow < 0 value to be direct io error
3270 if (end_io_error(uptodate))
3271 error = !uptodate ? -EIO : uptodate;
3274 * for a REQ_BLOCK_PC request, we want to carry any eventual
3275 * sense key with us all the way through
3277 if (!blk_pc_request(req))
3281 if (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))
3282 printk("end_request: I/O error, dev %s, sector %llu\n",
3283 req->rq_disk ? req->rq_disk->disk_name : "?",
3284 (unsigned long long)req->sector);
3287 if (blk_fs_request(req) && req->rq_disk) {
3288 const int rw = rq_data_dir(req);
3290 disk_stat_add(req->rq_disk, sectors[rw], nr_bytes >> 9);
3293 total_bytes = bio_nbytes = 0;
3294 while ((bio = req->bio) != NULL) {
3297 if (nr_bytes >= bio->bi_size) {
3298 req->bio = bio->bi_next;
3299 nbytes = bio->bi_size;
3300 if (!ordered_bio_endio(req, bio, nbytes, error))
3301 bio_endio(bio, nbytes, error);
3305 int idx = bio->bi_idx + next_idx;
3307 if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
3308 blk_dump_rq_flags(req, "__end_that");
3309 printk("%s: bio idx %d >= vcnt %d\n",
3311 bio->bi_idx, bio->bi_vcnt);
3315 nbytes = bio_iovec_idx(bio, idx)->bv_len;
3316 BIO_BUG_ON(nbytes > bio->bi_size);
3319 * not a complete bvec done
3321 if (unlikely(nbytes > nr_bytes)) {
3322 bio_nbytes += nr_bytes;
3323 total_bytes += nr_bytes;
3328 * advance to the next vector
3331 bio_nbytes += nbytes;
3334 total_bytes += nbytes;
3337 if ((bio = req->bio)) {
3339 * end more in this run, or just return 'not-done'
3341 if (unlikely(nr_bytes <= 0))
3353 * if the request wasn't completed, update state
3356 if (!ordered_bio_endio(req, bio, bio_nbytes, error))
3357 bio_endio(bio, bio_nbytes, error);
3358 bio->bi_idx += next_idx;
3359 bio_iovec(bio)->bv_offset += nr_bytes;
3360 bio_iovec(bio)->bv_len -= nr_bytes;
3363 blk_recalc_rq_sectors(req, total_bytes >> 9);
3364 blk_recalc_rq_segments(req);
3369 * end_that_request_first - end I/O on a request
3370 * @req: the request being processed
3371 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3372 * @nr_sectors: number of sectors to end I/O on
3375 * Ends I/O on a number of sectors attached to @req, and sets it up
3376 * for the next range of segments (if any) in the cluster.
3379 * 0 - we are done with this request, call end_that_request_last()
3380 * 1 - still buffers pending for this request
3382 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
3384 return __end_that_request_first(req, uptodate, nr_sectors << 9);
3387 EXPORT_SYMBOL(end_that_request_first);
3390 * end_that_request_chunk - end I/O on a request
3391 * @req: the request being processed
3392 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3393 * @nr_bytes: number of bytes to complete
3396 * Ends I/O on a number of bytes attached to @req, and sets it up
3397 * for the next range of segments (if any). Like end_that_request_first(),
3398 * but deals with bytes instead of sectors.
3401 * 0 - we are done with this request, call end_that_request_last()
3402 * 1 - still buffers pending for this request
3404 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
3406 return __end_that_request_first(req, uptodate, nr_bytes);
3409 EXPORT_SYMBOL(end_that_request_chunk);
3412 * splice the completion data to a local structure and hand off to
3413 * process_completion_queue() to complete the requests
3415 static void blk_done_softirq(struct softirq_action *h)
3417 struct list_head *cpu_list, local_list;
3419 local_irq_disable();
3420 cpu_list = &__get_cpu_var(blk_cpu_done);
3421 list_replace_init(cpu_list, &local_list);
3424 while (!list_empty(&local_list)) {
3425 struct request *rq = list_entry(local_list.next, struct request, donelist);
3427 list_del_init(&rq->donelist);
3428 rq->q->softirq_done_fn(rq);
3432 #ifdef CONFIG_HOTPLUG_CPU
3434 static int blk_cpu_notify(struct notifier_block *self, unsigned long action,
3438 * If a CPU goes away, splice its entries to the current CPU
3439 * and trigger a run of the softirq
3441 if (action == CPU_DEAD) {
3442 int cpu = (unsigned long) hcpu;
3444 local_irq_disable();
3445 list_splice_init(&per_cpu(blk_cpu_done, cpu),
3446 &__get_cpu_var(blk_cpu_done));
3447 raise_softirq_irqoff(BLOCK_SOFTIRQ);
3455 static struct notifier_block __devinitdata blk_cpu_notifier = {
3456 .notifier_call = blk_cpu_notify,
3459 #endif /* CONFIG_HOTPLUG_CPU */
3462 * blk_complete_request - end I/O on a request
3463 * @req: the request being processed
3466 * Ends all I/O on a request. It does not handle partial completions,
3467 * unless the driver actually implements this in its completion callback
3468 * through requeueing. Theh actual completion happens out-of-order,
3469 * through a softirq handler. The user must have registered a completion
3470 * callback through blk_queue_softirq_done().
3473 void blk_complete_request(struct request *req)
3475 struct list_head *cpu_list;
3476 unsigned long flags;
3478 BUG_ON(!req->q->softirq_done_fn);
3480 local_irq_save(flags);
3482 cpu_list = &__get_cpu_var(blk_cpu_done);
3483 list_add_tail(&req->donelist, cpu_list);
3484 raise_softirq_irqoff(BLOCK_SOFTIRQ);
3486 local_irq_restore(flags);
3489 EXPORT_SYMBOL(blk_complete_request);
3492 * queue lock must be held
3494 void end_that_request_last(struct request *req, int uptodate)
3496 struct gendisk *disk = req->rq_disk;
3500 * extend uptodate bool to allow < 0 value to be direct io error
3503 if (end_io_error(uptodate))
3504 error = !uptodate ? -EIO : uptodate;
3506 if (unlikely(laptop_mode) && blk_fs_request(req))
3507 laptop_io_completion();
3510 * Account IO completion. bar_rq isn't accounted as a normal
3511 * IO on queueing nor completion. Accounting the containing
3512 * request is enough.
3514 if (disk && blk_fs_request(req) && req != &req->q->bar_rq) {
3515 unsigned long duration = jiffies - req->start_time;
3516 const int rw = rq_data_dir(req);
3518 __disk_stat_inc(disk, ios[rw]);
3519 __disk_stat_add(disk, ticks[rw], duration);
3520 disk_round_stats(disk);
3524 req->end_io(req, error);
3526 __blk_put_request(req->q, req);
3529 EXPORT_SYMBOL(end_that_request_last);
3531 void end_request(struct request *req, int uptodate)
3533 if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3534 add_disk_randomness(req->rq_disk);
3535 blkdev_dequeue_request(req);
3536 end_that_request_last(req, uptodate);
3540 EXPORT_SYMBOL(end_request);
3542 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3544 /* first two bits are identical in rq->cmd_flags and bio->bi_rw */
3545 rq->cmd_flags |= (bio->bi_rw & 3);
3547 rq->nr_phys_segments = bio_phys_segments(q, bio);
3548 rq->nr_hw_segments = bio_hw_segments(q, bio);
3549 rq->current_nr_sectors = bio_cur_sectors(bio);
3550 rq->hard_cur_sectors = rq->current_nr_sectors;
3551 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3552 rq->buffer = bio_data(bio);
3554 rq->bio = rq->biotail = bio;
3557 EXPORT_SYMBOL(blk_rq_bio_prep);
3559 int kblockd_schedule_work(struct work_struct *work)
3561 return queue_work(kblockd_workqueue, work);
3564 EXPORT_SYMBOL(kblockd_schedule_work);
3566 void kblockd_flush(void)
3568 flush_workqueue(kblockd_workqueue);
3570 EXPORT_SYMBOL(kblockd_flush);
3572 int __init blk_dev_init(void)
3576 kblockd_workqueue = create_workqueue("kblockd");
3577 if (!kblockd_workqueue)
3578 panic("Failed to create kblockd\n");
3580 request_cachep = kmem_cache_create("blkdev_requests",
3581 sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3583 requestq_cachep = kmem_cache_create("blkdev_queue",
3584 sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3586 iocontext_cachep = kmem_cache_create("blkdev_ioc",
3587 sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3589 for_each_possible_cpu(i)
3590 INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i));
3592 open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
3593 register_hotcpu_notifier(&blk_cpu_notifier);
3595 blk_max_low_pfn = max_low_pfn;
3596 blk_max_pfn = max_pfn;
3602 * IO Context helper functions
3604 void put_io_context(struct io_context *ioc)
3609 BUG_ON(atomic_read(&ioc->refcount) == 0);
3611 if (atomic_dec_and_test(&ioc->refcount)) {
3612 struct cfq_io_context *cic;
3615 if (ioc->aic && ioc->aic->dtor)
3616 ioc->aic->dtor(ioc->aic);
3617 if (ioc->cic_root.rb_node != NULL) {
3618 struct rb_node *n = rb_first(&ioc->cic_root);
3620 cic = rb_entry(n, struct cfq_io_context, rb_node);
3625 kmem_cache_free(iocontext_cachep, ioc);
3628 EXPORT_SYMBOL(put_io_context);
3630 /* Called by the exitting task */
3631 void exit_io_context(void)
3633 unsigned long flags;
3634 struct io_context *ioc;
3635 struct cfq_io_context *cic;
3637 local_irq_save(flags);
3639 ioc = current->io_context;
3640 current->io_context = NULL;
3642 task_unlock(current);
3643 local_irq_restore(flags);
3645 if (ioc->aic && ioc->aic->exit)
3646 ioc->aic->exit(ioc->aic);
3647 if (ioc->cic_root.rb_node != NULL) {
3648 cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
3652 put_io_context(ioc);
3656 * If the current task has no IO context then create one and initialise it.
3657 * Otherwise, return its existing IO context.
3659 * This returned IO context doesn't have a specifically elevated refcount,
3660 * but since the current task itself holds a reference, the context can be
3661 * used in general code, so long as it stays within `current` context.
3663 struct io_context *current_io_context(gfp_t gfp_flags)
3665 struct task_struct *tsk = current;
3666 struct io_context *ret;
3668 ret = tsk->io_context;
3672 ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3674 atomic_set(&ret->refcount, 1);
3675 ret->task = current;
3676 ret->set_ioprio = NULL;
3677 ret->last_waited = jiffies; /* doesn't matter... */
3678 ret->nr_batch_requests = 0; /* because this is 0 */
3680 ret->cic_root.rb_node = NULL;
3681 /* make sure set_task_ioprio() sees the settings above */
3683 tsk->io_context = ret;
3688 EXPORT_SYMBOL(current_io_context);
3691 * If the current task has no IO context then create one and initialise it.
3692 * If it does have a context, take a ref on it.
3694 * This is always called in the context of the task which submitted the I/O.
3696 struct io_context *get_io_context(gfp_t gfp_flags)
3698 struct io_context *ret;
3699 ret = current_io_context(gfp_flags);
3701 atomic_inc(&ret->refcount);
3704 EXPORT_SYMBOL(get_io_context);
3706 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3708 struct io_context *src = *psrc;
3709 struct io_context *dst = *pdst;
3712 BUG_ON(atomic_read(&src->refcount) == 0);
3713 atomic_inc(&src->refcount);
3714 put_io_context(dst);
3718 EXPORT_SYMBOL(copy_io_context);
3720 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3722 struct io_context *temp;
3727 EXPORT_SYMBOL(swap_io_context);
3732 struct queue_sysfs_entry {
3733 struct attribute attr;
3734 ssize_t (*show)(struct request_queue *, char *);
3735 ssize_t (*store)(struct request_queue *, const char *, size_t);
3739 queue_var_show(unsigned int var, char *page)
3741 return sprintf(page, "%d\n", var);
3745 queue_var_store(unsigned long *var, const char *page, size_t count)
3747 char *p = (char *) page;
3749 *var = simple_strtoul(p, &p, 10);
3753 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3755 return queue_var_show(q->nr_requests, (page));
3759 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3761 struct request_list *rl = &q->rq;
3763 int ret = queue_var_store(&nr, page, count);
3764 if (nr < BLKDEV_MIN_RQ)
3767 spin_lock_irq(q->queue_lock);
3768 q->nr_requests = nr;
3769 blk_queue_congestion_threshold(q);
3771 if (rl->count[READ] >= queue_congestion_on_threshold(q))
3772 set_queue_congested(q, READ);
3773 else if (rl->count[READ] < queue_congestion_off_threshold(q))
3774 clear_queue_congested(q, READ);
3776 if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3777 set_queue_congested(q, WRITE);
3778 else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3779 clear_queue_congested(q, WRITE);
3781 if (rl->count[READ] >= q->nr_requests) {
3782 blk_set_queue_full(q, READ);
3783 } else if (rl->count[READ]+1 <= q->nr_requests) {
3784 blk_clear_queue_full(q, READ);
3785 wake_up(&rl->wait[READ]);
3788 if (rl->count[WRITE] >= q->nr_requests) {
3789 blk_set_queue_full(q, WRITE);
3790 } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3791 blk_clear_queue_full(q, WRITE);
3792 wake_up(&rl->wait[WRITE]);
3794 spin_unlock_irq(q->queue_lock);
3798 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3800 int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3802 return queue_var_show(ra_kb, (page));
3806 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3808 unsigned long ra_kb;
3809 ssize_t ret = queue_var_store(&ra_kb, page, count);
3811 spin_lock_irq(q->queue_lock);
3812 if (ra_kb > (q->max_sectors >> 1))
3813 ra_kb = (q->max_sectors >> 1);
3815 q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3816 spin_unlock_irq(q->queue_lock);
3821 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3823 int max_sectors_kb = q->max_sectors >> 1;
3825 return queue_var_show(max_sectors_kb, (page));
3829 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3831 unsigned long max_sectors_kb,
3832 max_hw_sectors_kb = q->max_hw_sectors >> 1,
3833 page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3834 ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3837 if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3840 * Take the queue lock to update the readahead and max_sectors
3841 * values synchronously:
3843 spin_lock_irq(q->queue_lock);
3845 * Trim readahead window as well, if necessary:
3847 ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3848 if (ra_kb > max_sectors_kb)
3849 q->backing_dev_info.ra_pages =
3850 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3852 q->max_sectors = max_sectors_kb << 1;
3853 spin_unlock_irq(q->queue_lock);
3858 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3860 int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3862 return queue_var_show(max_hw_sectors_kb, (page));
3866 static struct queue_sysfs_entry queue_requests_entry = {
3867 .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3868 .show = queue_requests_show,
3869 .store = queue_requests_store,
3872 static struct queue_sysfs_entry queue_ra_entry = {
3873 .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3874 .show = queue_ra_show,
3875 .store = queue_ra_store,
3878 static struct queue_sysfs_entry queue_max_sectors_entry = {
3879 .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3880 .show = queue_max_sectors_show,
3881 .store = queue_max_sectors_store,
3884 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3885 .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3886 .show = queue_max_hw_sectors_show,
3889 static struct queue_sysfs_entry queue_iosched_entry = {
3890 .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3891 .show = elv_iosched_show,
3892 .store = elv_iosched_store,
3895 static struct attribute *default_attrs[] = {
3896 &queue_requests_entry.attr,
3897 &queue_ra_entry.attr,
3898 &queue_max_hw_sectors_entry.attr,
3899 &queue_max_sectors_entry.attr,
3900 &queue_iosched_entry.attr,
3904 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3907 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3909 struct queue_sysfs_entry *entry = to_queue(attr);
3910 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3915 mutex_lock(&q->sysfs_lock);
3916 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3917 mutex_unlock(&q->sysfs_lock);
3920 res = entry->show(q, page);
3921 mutex_unlock(&q->sysfs_lock);
3926 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3927 const char *page, size_t length)
3929 struct queue_sysfs_entry *entry = to_queue(attr);
3930 request_queue_t *q = container_of(kobj, struct request_queue, kobj);
3936 mutex_lock(&q->sysfs_lock);
3937 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
3938 mutex_unlock(&q->sysfs_lock);
3941 res = entry->store(q, page, length);
3942 mutex_unlock(&q->sysfs_lock);
3946 static struct sysfs_ops queue_sysfs_ops = {
3947 .show = queue_attr_show,
3948 .store = queue_attr_store,
3951 static struct kobj_type queue_ktype = {
3952 .sysfs_ops = &queue_sysfs_ops,
3953 .default_attrs = default_attrs,
3954 .release = blk_release_queue,
3957 int blk_register_queue(struct gendisk *disk)
3961 request_queue_t *q = disk->queue;
3963 if (!q || !q->request_fn)
3966 q->kobj.parent = kobject_get(&disk->kobj);
3968 ret = kobject_add(&q->kobj);
3972 kobject_uevent(&q->kobj, KOBJ_ADD);
3974 ret = elv_register_queue(q);
3976 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3977 kobject_del(&q->kobj);
3984 void blk_unregister_queue(struct gendisk *disk)
3986 request_queue_t *q = disk->queue;
3988 if (q && q->request_fn) {
3989 elv_unregister_queue(q);
3991 kobject_uevent(&q->kobj, KOBJ_REMOVE);
3992 kobject_del(&q->kobj);
3993 kobject_put(&disk->kobj);