2 * linux/drivers/block/ll_rw_blk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
6 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
7 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
8 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> - July2000
9 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
13 * This handles all read/write requests to block devices
15 #include <linux/config.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/backing-dev.h>
19 #include <linux/bio.h>
20 #include <linux/blkdev.h>
21 #include <linux/highmem.h>
23 #include <linux/kernel_stat.h>
24 #include <linux/string.h>
25 #include <linux/init.h>
26 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
27 #include <linux/completion.h>
28 #include <linux/slab.h>
29 #include <linux/swap.h>
30 #include <linux/writeback.h>
35 #include <scsi/scsi_cmnd.h>
37 static void blk_unplug_work(void *data);
38 static void blk_unplug_timeout(unsigned long data);
41 * For the allocated request tables
43 static kmem_cache_t *request_cachep;
46 * For queue allocation
48 static kmem_cache_t *requestq_cachep;
51 * For io context allocations
53 static kmem_cache_t *iocontext_cachep;
55 static wait_queue_head_t congestion_wqh[2] = {
56 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
57 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
61 * Controlling structure to kblockd
63 static struct workqueue_struct *kblockd_workqueue;
65 unsigned long blk_max_low_pfn, blk_max_pfn;
67 EXPORT_SYMBOL(blk_max_low_pfn);
68 EXPORT_SYMBOL(blk_max_pfn);
70 /* Amount of time in which a process may batch requests */
71 #define BLK_BATCH_TIME (HZ/50UL)
73 /* Number of requests a "batching" process may submit */
74 #define BLK_BATCH_REQ 32
77 * Return the threshold (number of used requests) at which the queue is
78 * considered to be congested. It include a little hysteresis to keep the
79 * context switch rate down.
81 static inline int queue_congestion_on_threshold(struct request_queue *q)
83 return q->nr_congestion_on;
87 * The threshold at which a queue is considered to be uncongested
89 static inline int queue_congestion_off_threshold(struct request_queue *q)
91 return q->nr_congestion_off;
94 static void blk_queue_congestion_threshold(struct request_queue *q)
98 nr = q->nr_requests - (q->nr_requests / 8) + 1;
99 if (nr > q->nr_requests)
101 q->nr_congestion_on = nr;
103 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
106 q->nr_congestion_off = nr;
110 * A queue has just exitted congestion. Note this in the global counter of
111 * congested queues, and wake up anyone who was waiting for requests to be
114 static void clear_queue_congested(request_queue_t *q, int rw)
117 wait_queue_head_t *wqh = &congestion_wqh[rw];
119 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
120 clear_bit(bit, &q->backing_dev_info.state);
121 smp_mb__after_clear_bit();
122 if (waitqueue_active(wqh))
127 * A queue has just entered congestion. Flag that in the queue's VM-visible
128 * state flags and increment the global gounter of congested queues.
130 static void set_queue_congested(request_queue_t *q, int rw)
134 bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
135 set_bit(bit, &q->backing_dev_info.state);
139 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
142 * Locates the passed device's request queue and returns the address of its
145 * Will return NULL if the request queue cannot be located.
147 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
149 struct backing_dev_info *ret = NULL;
150 request_queue_t *q = bdev_get_queue(bdev);
153 ret = &q->backing_dev_info;
157 EXPORT_SYMBOL(blk_get_backing_dev_info);
159 void blk_queue_activity_fn(request_queue_t *q, activity_fn *fn, void *data)
162 q->activity_data = data;
165 EXPORT_SYMBOL(blk_queue_activity_fn);
168 * blk_queue_prep_rq - set a prepare_request function for queue
170 * @pfn: prepare_request function
172 * It's possible for a queue to register a prepare_request callback which
173 * is invoked before the request is handed to the request_fn. The goal of
174 * the function is to prepare a request for I/O, it can be used to build a
175 * cdb from the request data for instance.
178 void blk_queue_prep_rq(request_queue_t *q, prep_rq_fn *pfn)
183 EXPORT_SYMBOL(blk_queue_prep_rq);
186 * blk_queue_merge_bvec - set a merge_bvec function for queue
188 * @mbfn: merge_bvec_fn
190 * Usually queues have static limitations on the max sectors or segments that
191 * we can put in a request. Stacking drivers may have some settings that
192 * are dynamic, and thus we have to query the queue whether it is ok to
193 * add a new bio_vec to a bio at a given offset or not. If the block device
194 * has such limitations, it needs to register a merge_bvec_fn to control
195 * the size of bio's sent to it. Note that a block device *must* allow a
196 * single page to be added to an empty bio. The block device driver may want
197 * to use the bio_split() function to deal with these bio's. By default
198 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
201 void blk_queue_merge_bvec(request_queue_t *q, merge_bvec_fn *mbfn)
203 q->merge_bvec_fn = mbfn;
206 EXPORT_SYMBOL(blk_queue_merge_bvec);
209 * blk_queue_make_request - define an alternate make_request function for a device
210 * @q: the request queue for the device to be affected
211 * @mfn: the alternate make_request function
214 * The normal way for &struct bios to be passed to a device
215 * driver is for them to be collected into requests on a request
216 * queue, and then to allow the device driver to select requests
217 * off that queue when it is ready. This works well for many block
218 * devices. However some block devices (typically virtual devices
219 * such as md or lvm) do not benefit from the processing on the
220 * request queue, and are served best by having the requests passed
221 * directly to them. This can be achieved by providing a function
222 * to blk_queue_make_request().
225 * The driver that does this *must* be able to deal appropriately
226 * with buffers in "highmemory". This can be accomplished by either calling
227 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
228 * blk_queue_bounce() to create a buffer in normal memory.
230 void blk_queue_make_request(request_queue_t * q, make_request_fn * mfn)
235 q->nr_requests = BLKDEV_MAX_RQ;
236 q->max_phys_segments = MAX_PHYS_SEGMENTS;
237 q->max_hw_segments = MAX_HW_SEGMENTS;
238 q->make_request_fn = mfn;
239 q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
240 q->backing_dev_info.state = 0;
241 q->backing_dev_info.memory_backed = 0;
242 blk_queue_max_sectors(q, MAX_SECTORS);
243 blk_queue_hardsect_size(q, 512);
244 blk_queue_dma_alignment(q, 511);
245 blk_queue_congestion_threshold(q);
246 q->nr_batching = BLK_BATCH_REQ;
248 q->unplug_thresh = 4; /* hmm */
249 q->unplug_delay = (3 * HZ) / 1000; /* 3 milliseconds */
250 if (q->unplug_delay == 0)
253 INIT_WORK(&q->unplug_work, blk_unplug_work, q);
255 q->unplug_timer.function = blk_unplug_timeout;
256 q->unplug_timer.data = (unsigned long)q;
259 * by default assume old behaviour and bounce for any highmem page
261 blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
263 blk_queue_activity_fn(q, NULL, NULL);
265 INIT_LIST_HEAD(&q->drain_list);
268 EXPORT_SYMBOL(blk_queue_make_request);
271 * blk_queue_ordered - does this queue support ordered writes
272 * @q: the request queue
276 * For journalled file systems, doing ordered writes on a commit
277 * block instead of explicitly doing wait_on_buffer (which is bad
278 * for performance) can be a big win. Block drivers supporting this
279 * feature should call this function and indicate so.
282 void blk_queue_ordered(request_queue_t *q, int flag)
285 set_bit(QUEUE_FLAG_ORDERED, &q->queue_flags);
287 clear_bit(QUEUE_FLAG_ORDERED, &q->queue_flags);
290 EXPORT_SYMBOL(blk_queue_ordered);
293 * blk_queue_issue_flush_fn - set function for issuing a flush
294 * @q: the request queue
295 * @iff: the function to be called issuing the flush
298 * If a driver supports issuing a flush command, the support is notified
299 * to the block layer by defining it through this call.
302 void blk_queue_issue_flush_fn(request_queue_t *q, issue_flush_fn *iff)
304 q->issue_flush_fn = iff;
307 EXPORT_SYMBOL(blk_queue_issue_flush_fn);
310 * blk_queue_bounce_limit - set bounce buffer limit for queue
311 * @q: the request queue for the device
312 * @dma_addr: bus address limit
315 * Different hardware can have different requirements as to what pages
316 * it can do I/O directly to. A low level driver can call
317 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
318 * buffers for doing I/O to pages residing above @page. By default
319 * the block layer sets this to the highest numbered "low" memory page.
321 void blk_queue_bounce_limit(request_queue_t *q, u64 dma_addr)
323 unsigned long bounce_pfn = dma_addr >> PAGE_SHIFT;
326 * set appropriate bounce gfp mask -- unfortunately we don't have a
327 * full 4GB zone, so we have to resort to low memory for any bounces.
328 * ISA has its own < 16MB zone.
330 if (bounce_pfn < blk_max_low_pfn) {
331 BUG_ON(dma_addr < BLK_BOUNCE_ISA);
332 init_emergency_isa_pool();
333 q->bounce_gfp = GFP_NOIO | GFP_DMA;
335 q->bounce_gfp = GFP_NOIO;
337 q->bounce_pfn = bounce_pfn;
340 EXPORT_SYMBOL(blk_queue_bounce_limit);
343 * blk_queue_max_sectors - set max sectors for a request for this queue
344 * @q: the request queue for the device
345 * @max_sectors: max sectors in the usual 512b unit
348 * Enables a low level driver to set an upper limit on the size of
351 void blk_queue_max_sectors(request_queue_t *q, unsigned short max_sectors)
353 if ((max_sectors << 9) < PAGE_CACHE_SIZE) {
354 max_sectors = 1 << (PAGE_CACHE_SHIFT - 9);
355 printk("%s: set to minimum %d\n", __FUNCTION__, max_sectors);
358 q->max_sectors = q->max_hw_sectors = max_sectors;
361 EXPORT_SYMBOL(blk_queue_max_sectors);
364 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
365 * @q: the request queue for the device
366 * @max_segments: max number of segments
369 * Enables a low level driver to set an upper limit on the number of
370 * physical data segments in a request. This would be the largest sized
371 * scatter list the driver could handle.
373 void blk_queue_max_phys_segments(request_queue_t *q, unsigned short max_segments)
377 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
380 q->max_phys_segments = max_segments;
383 EXPORT_SYMBOL(blk_queue_max_phys_segments);
386 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
387 * @q: the request queue for the device
388 * @max_segments: max number of segments
391 * Enables a low level driver to set an upper limit on the number of
392 * hw data segments in a request. This would be the largest number of
393 * address/length pairs the host adapter can actually give as once
396 void blk_queue_max_hw_segments(request_queue_t *q, unsigned short max_segments)
400 printk("%s: set to minimum %d\n", __FUNCTION__, max_segments);
403 q->max_hw_segments = max_segments;
406 EXPORT_SYMBOL(blk_queue_max_hw_segments);
409 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
410 * @q: the request queue for the device
411 * @max_size: max size of segment in bytes
414 * Enables a low level driver to set an upper limit on the size of a
417 void blk_queue_max_segment_size(request_queue_t *q, unsigned int max_size)
419 if (max_size < PAGE_CACHE_SIZE) {
420 max_size = PAGE_CACHE_SIZE;
421 printk("%s: set to minimum %d\n", __FUNCTION__, max_size);
424 q->max_segment_size = max_size;
427 EXPORT_SYMBOL(blk_queue_max_segment_size);
430 * blk_queue_hardsect_size - set hardware sector size for the queue
431 * @q: the request queue for the device
432 * @size: the hardware sector size, in bytes
435 * This should typically be set to the lowest possible sector size
436 * that the hardware can operate on (possible without reverting to
437 * even internal read-modify-write operations). Usually the default
438 * of 512 covers most hardware.
440 void blk_queue_hardsect_size(request_queue_t *q, unsigned short size)
442 q->hardsect_size = size;
445 EXPORT_SYMBOL(blk_queue_hardsect_size);
448 * Returns the minimum that is _not_ zero, unless both are zero.
450 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
453 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
454 * @t: the stacking driver (top)
455 * @b: the underlying device (bottom)
457 void blk_queue_stack_limits(request_queue_t *t, request_queue_t *b)
459 /* zero is "infinity" */
460 t->max_sectors = t->max_hw_sectors =
461 min_not_zero(t->max_sectors,b->max_sectors);
463 t->max_phys_segments = min(t->max_phys_segments,b->max_phys_segments);
464 t->max_hw_segments = min(t->max_hw_segments,b->max_hw_segments);
465 t->max_segment_size = min(t->max_segment_size,b->max_segment_size);
466 t->hardsect_size = max(t->hardsect_size,b->hardsect_size);
469 EXPORT_SYMBOL(blk_queue_stack_limits);
472 * blk_queue_segment_boundary - set boundary rules for segment merging
473 * @q: the request queue for the device
474 * @mask: the memory boundary mask
476 void blk_queue_segment_boundary(request_queue_t *q, unsigned long mask)
478 if (mask < PAGE_CACHE_SIZE - 1) {
479 mask = PAGE_CACHE_SIZE - 1;
480 printk("%s: set to minimum %lx\n", __FUNCTION__, mask);
483 q->seg_boundary_mask = mask;
486 EXPORT_SYMBOL(blk_queue_segment_boundary);
489 * blk_queue_dma_alignment - set dma length and memory alignment
490 * @q: the request queue for the device
491 * @mask: alignment mask
494 * set required memory and length aligment for direct dma transactions.
495 * this is used when buiding direct io requests for the queue.
498 void blk_queue_dma_alignment(request_queue_t *q, int mask)
500 q->dma_alignment = mask;
503 EXPORT_SYMBOL(blk_queue_dma_alignment);
506 * blk_queue_find_tag - find a request by its tag and queue
508 * @q: The request queue for the device
509 * @tag: The tag of the request
512 * Should be used when a device returns a tag and you want to match
515 * no locks need be held.
517 struct request *blk_queue_find_tag(request_queue_t *q, int tag)
519 struct blk_queue_tag *bqt = q->queue_tags;
521 if (unlikely(bqt == NULL || tag >= bqt->real_max_depth))
524 return bqt->tag_index[tag];
527 EXPORT_SYMBOL(blk_queue_find_tag);
530 * __blk_queue_free_tags - release tag maintenance info
531 * @q: the request queue for the device
534 * blk_cleanup_queue() will take care of calling this function, if tagging
535 * has been used. So there's no need to call this directly.
537 static void __blk_queue_free_tags(request_queue_t *q)
539 struct blk_queue_tag *bqt = q->queue_tags;
544 if (atomic_dec_and_test(&bqt->refcnt)) {
546 BUG_ON(!list_empty(&bqt->busy_list));
548 kfree(bqt->tag_index);
549 bqt->tag_index = NULL;
557 q->queue_tags = NULL;
558 q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED);
562 * blk_queue_free_tags - release tag maintenance info
563 * @q: the request queue for the device
566 * This is used to disabled tagged queuing to a device, yet leave
569 void blk_queue_free_tags(request_queue_t *q)
571 clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
574 EXPORT_SYMBOL(blk_queue_free_tags);
577 init_tag_map(request_queue_t *q, struct blk_queue_tag *tags, int depth)
580 struct request **tag_index;
581 unsigned long *tag_map;
583 if (depth > q->nr_requests * 2) {
584 depth = q->nr_requests * 2;
585 printk(KERN_ERR "%s: adjusted depth to %d\n",
586 __FUNCTION__, depth);
589 tag_index = kmalloc(depth * sizeof(struct request *), GFP_ATOMIC);
593 bits = (depth / BLK_TAGS_PER_LONG) + 1;
594 tag_map = kmalloc(bits * sizeof(unsigned long), GFP_ATOMIC);
598 memset(tag_index, 0, depth * sizeof(struct request *));
599 memset(tag_map, 0, bits * sizeof(unsigned long));
600 tags->max_depth = depth;
601 tags->real_max_depth = bits * BITS_PER_LONG;
602 tags->tag_index = tag_index;
603 tags->tag_map = tag_map;
606 * set the upper bits if the depth isn't a multiple of the word size
608 for (i = depth; i < bits * BLK_TAGS_PER_LONG; i++)
609 __set_bit(i, tag_map);
618 * blk_queue_init_tags - initialize the queue tag info
619 * @q: the request queue for the device
620 * @depth: the maximum queue depth supported
622 int blk_queue_init_tags(request_queue_t *q, int depth,
623 struct blk_queue_tag *tags)
627 BUG_ON(tags && q->queue_tags && tags != q->queue_tags);
629 if (!tags && !q->queue_tags) {
630 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC);
634 if (init_tag_map(q, tags, depth))
637 INIT_LIST_HEAD(&tags->busy_list);
639 atomic_set(&tags->refcnt, 1);
640 } else if (q->queue_tags) {
641 if ((rc = blk_queue_resize_tags(q, depth)))
643 set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags);
646 atomic_inc(&tags->refcnt);
649 * assign it, all done
651 q->queue_tags = tags;
652 q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);
659 EXPORT_SYMBOL(blk_queue_init_tags);
662 * blk_queue_resize_tags - change the queueing depth
663 * @q: the request queue for the device
664 * @new_depth: the new max command queueing depth
667 * Must be called with the queue lock held.
669 int blk_queue_resize_tags(request_queue_t *q, int new_depth)
671 struct blk_queue_tag *bqt = q->queue_tags;
672 struct request **tag_index;
673 unsigned long *tag_map;
680 * don't bother sizing down
682 if (new_depth <= bqt->real_max_depth) {
683 bqt->max_depth = new_depth;
688 * save the old state info, so we can copy it back
690 tag_index = bqt->tag_index;
691 tag_map = bqt->tag_map;
692 max_depth = bqt->real_max_depth;
694 if (init_tag_map(q, bqt, new_depth))
697 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *));
698 bits = max_depth / BLK_TAGS_PER_LONG;
699 memcpy(bqt->tag_map, tag_map, bits * sizeof(unsigned long));
706 EXPORT_SYMBOL(blk_queue_resize_tags);
709 * blk_queue_end_tag - end tag operations for a request
710 * @q: the request queue for the device
711 * @rq: the request that has completed
714 * Typically called when end_that_request_first() returns 0, meaning
715 * all transfers have been done for a request. It's important to call
716 * this function before end_that_request_last(), as that will put the
717 * request back on the free list thus corrupting the internal tag list.
720 * queue lock must be held.
722 void blk_queue_end_tag(request_queue_t *q, struct request *rq)
724 struct blk_queue_tag *bqt = q->queue_tags;
729 if (unlikely(tag >= bqt->real_max_depth))
732 if (unlikely(!__test_and_clear_bit(tag, bqt->tag_map))) {
733 printk("attempt to clear non-busy tag (%d)\n", tag);
737 list_del_init(&rq->queuelist);
738 rq->flags &= ~REQ_QUEUED;
741 if (unlikely(bqt->tag_index[tag] == NULL))
742 printk("tag %d is missing\n", tag);
744 bqt->tag_index[tag] = NULL;
748 EXPORT_SYMBOL(blk_queue_end_tag);
751 * blk_queue_start_tag - find a free tag and assign it
752 * @q: the request queue for the device
753 * @rq: the block request that needs tagging
756 * This can either be used as a stand-alone helper, or possibly be
757 * assigned as the queue &prep_rq_fn (in which case &struct request
758 * automagically gets a tag assigned). Note that this function
759 * assumes that any type of request can be queued! if this is not
760 * true for your device, you must check the request type before
761 * calling this function. The request will also be removed from
762 * the request queue, so it's the drivers responsibility to readd
763 * it if it should need to be restarted for some reason.
766 * queue lock must be held.
768 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
770 struct blk_queue_tag *bqt = q->queue_tags;
771 unsigned long *map = bqt->tag_map;
774 if (unlikely((rq->flags & REQ_QUEUED))) {
776 "request %p for device [%s] already tagged %d",
777 rq, rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag);
781 for (map = bqt->tag_map; *map == -1UL; map++) {
782 tag += BLK_TAGS_PER_LONG;
784 if (tag >= bqt->max_depth)
789 __set_bit(tag, bqt->tag_map);
791 rq->flags |= REQ_QUEUED;
793 bqt->tag_index[tag] = rq;
794 blkdev_dequeue_request(rq);
795 list_add(&rq->queuelist, &bqt->busy_list);
800 EXPORT_SYMBOL(blk_queue_start_tag);
803 * blk_queue_invalidate_tags - invalidate all pending tags
804 * @q: the request queue for the device
807 * Hardware conditions may dictate a need to stop all pending requests.
808 * In this case, we will safely clear the block side of the tag queue and
809 * readd all requests to the request queue in the right order.
812 * queue lock must be held.
814 void blk_queue_invalidate_tags(request_queue_t *q)
816 struct blk_queue_tag *bqt = q->queue_tags;
817 struct list_head *tmp, *n;
820 list_for_each_safe(tmp, n, &bqt->busy_list) {
821 rq = list_entry_rq(tmp);
824 printk("bad tag found on list\n");
825 list_del_init(&rq->queuelist);
826 rq->flags &= ~REQ_QUEUED;
828 blk_queue_end_tag(q, rq);
830 rq->flags &= ~REQ_STARTED;
831 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
835 EXPORT_SYMBOL(blk_queue_invalidate_tags);
837 static char *rq_flags[] = {
855 "REQ_DRIVE_TASKFILE",
862 void blk_dump_rq_flags(struct request *rq, char *msg)
866 printk("%s: dev %s: flags = ", msg,
867 rq->rq_disk ? rq->rq_disk->disk_name : "?");
870 if (rq->flags & (1 << bit))
871 printk("%s ", rq_flags[bit]);
873 } while (bit < __REQ_NR_BITS);
875 printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq->sector,
877 rq->current_nr_sectors);
878 printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq->bio, rq->biotail, rq->buffer, rq->data, rq->data_len);
880 if (rq->flags & (REQ_BLOCK_PC | REQ_PC)) {
882 for (bit = 0; bit < sizeof(rq->cmd); bit++)
883 printk("%02x ", rq->cmd[bit]);
888 EXPORT_SYMBOL(blk_dump_rq_flags);
890 void blk_recount_segments(request_queue_t *q, struct bio *bio)
892 struct bio_vec *bv, *bvprv = NULL;
893 int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
894 int high, highprv = 1;
896 if (unlikely(!bio->bi_io_vec))
899 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
900 hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
901 bio_for_each_segment(bv, bio, i) {
903 * the trick here is making sure that a high page is never
904 * considered part of another segment, since that might
905 * change with the bounce page.
907 high = page_to_pfn(bv->bv_page) >= q->bounce_pfn;
911 if (seg_size + bv->bv_len > q->max_segment_size)
913 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
915 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
917 if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
920 seg_size += bv->bv_len;
921 hw_seg_size += bv->bv_len;
926 if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
927 !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
928 hw_seg_size += bv->bv_len;
931 if (hw_seg_size > bio->bi_hw_front_size)
932 bio->bi_hw_front_size = hw_seg_size;
933 hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
939 seg_size = bv->bv_len;
942 if (hw_seg_size > bio->bi_hw_back_size)
943 bio->bi_hw_back_size = hw_seg_size;
944 if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
945 bio->bi_hw_front_size = hw_seg_size;
946 bio->bi_phys_segments = nr_phys_segs;
947 bio->bi_hw_segments = nr_hw_segs;
948 bio->bi_flags |= (1 << BIO_SEG_VALID);
952 int blk_phys_contig_segment(request_queue_t *q, struct bio *bio,
955 if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
958 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
960 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
964 * bio and nxt are contigous in memory, check if the queue allows
965 * these two to be merged into one
967 if (BIO_SEG_BOUNDARY(q, bio, nxt))
973 EXPORT_SYMBOL(blk_phys_contig_segment);
975 int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
978 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
979 blk_recount_segments(q, bio);
980 if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
981 blk_recount_segments(q, nxt);
982 if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
983 BIOVEC_VIRT_OVERSIZE(bio->bi_hw_front_size + bio->bi_hw_back_size))
985 if (bio->bi_size + nxt->bi_size > q->max_segment_size)
991 EXPORT_SYMBOL(blk_hw_contig_segment);
994 * map a request to scatterlist, return number of sg entries setup. Caller
995 * must make sure sg can hold rq->nr_phys_segments entries
997 int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg)
999 struct bio_vec *bvec, *bvprv;
1001 int nsegs, i, cluster;
1004 cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
1007 * for each bio in rq
1010 rq_for_each_bio(bio, rq) {
1012 * for each segment in bio
1014 bio_for_each_segment(bvec, bio, i) {
1015 int nbytes = bvec->bv_len;
1017 if (bvprv && cluster) {
1018 if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
1021 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
1023 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
1026 sg[nsegs - 1].length += nbytes;
1029 memset(&sg[nsegs],0,sizeof(struct scatterlist));
1030 sg[nsegs].page = bvec->bv_page;
1031 sg[nsegs].length = nbytes;
1032 sg[nsegs].offset = bvec->bv_offset;
1037 } /* segments in bio */
1043 EXPORT_SYMBOL(blk_rq_map_sg);
1046 * the standard queue merge functions, can be overridden with device
1047 * specific ones if so desired
1050 static inline int ll_new_mergeable(request_queue_t *q,
1051 struct request *req,
1054 int nr_phys_segs = bio_phys_segments(q, bio);
1056 if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1057 req->flags |= REQ_NOMERGE;
1058 if (req == q->last_merge)
1059 q->last_merge = NULL;
1064 * A hw segment is just getting larger, bump just the phys
1067 req->nr_phys_segments += nr_phys_segs;
1071 static inline int ll_new_hw_segment(request_queue_t *q,
1072 struct request *req,
1075 int nr_hw_segs = bio_hw_segments(q, bio);
1076 int nr_phys_segs = bio_phys_segments(q, bio);
1078 if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
1079 || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
1080 req->flags |= REQ_NOMERGE;
1081 if (req == q->last_merge)
1082 q->last_merge = NULL;
1087 * This will form the start of a new hw segment. Bump both
1090 req->nr_hw_segments += nr_hw_segs;
1091 req->nr_phys_segments += nr_phys_segs;
1095 static int ll_back_merge_fn(request_queue_t *q, struct request *req,
1100 if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
1101 req->flags |= REQ_NOMERGE;
1102 if (req == q->last_merge)
1103 q->last_merge = NULL;
1106 if (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
1107 blk_recount_segments(q, req->biotail);
1108 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1109 blk_recount_segments(q, bio);
1110 len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
1111 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
1112 !BIOVEC_VIRT_OVERSIZE(len)) {
1113 int mergeable = ll_new_mergeable(q, req, bio);
1116 if (req->nr_hw_segments == 1)
1117 req->bio->bi_hw_front_size = len;
1118 if (bio->bi_hw_segments == 1)
1119 bio->bi_hw_back_size = len;
1124 return ll_new_hw_segment(q, req, bio);
1127 static int ll_front_merge_fn(request_queue_t *q, struct request *req,
1132 if (req->nr_sectors + bio_sectors(bio) > q->max_sectors) {
1133 req->flags |= REQ_NOMERGE;
1134 if (req == q->last_merge)
1135 q->last_merge = NULL;
1138 len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
1139 if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
1140 blk_recount_segments(q, bio);
1141 if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
1142 blk_recount_segments(q, req->bio);
1143 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
1144 !BIOVEC_VIRT_OVERSIZE(len)) {
1145 int mergeable = ll_new_mergeable(q, req, bio);
1148 if (bio->bi_hw_segments == 1)
1149 bio->bi_hw_front_size = len;
1150 if (req->nr_hw_segments == 1)
1151 req->biotail->bi_hw_back_size = len;
1156 return ll_new_hw_segment(q, req, bio);
1159 static int ll_merge_requests_fn(request_queue_t *q, struct request *req,
1160 struct request *next)
1162 int total_phys_segments = req->nr_phys_segments +next->nr_phys_segments;
1163 int total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1166 * First check if the either of the requests are re-queued
1167 * requests. Can't merge them if they are.
1169 if (req->special || next->special)
1173 * Will it become to large?
1175 if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
1178 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
1179 if (blk_phys_contig_segment(q, req->biotail, next->bio))
1180 total_phys_segments--;
1182 if (total_phys_segments > q->max_phys_segments)
1185 total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
1186 if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
1187 int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
1189 * propagate the combined length to the end of the requests
1191 if (req->nr_hw_segments == 1)
1192 req->bio->bi_hw_front_size = len;
1193 if (next->nr_hw_segments == 1)
1194 next->biotail->bi_hw_back_size = len;
1195 total_hw_segments--;
1198 if (total_hw_segments > q->max_hw_segments)
1201 /* Merge is OK... */
1202 req->nr_phys_segments = total_phys_segments;
1203 req->nr_hw_segments = total_hw_segments;
1208 * "plug" the device if there are no outstanding requests: this will
1209 * force the transfer to start only after we have put all the requests
1212 * This is called with interrupts off and no requests on the queue and
1213 * with the queue lock held.
1215 void blk_plug_device(request_queue_t *q)
1217 WARN_ON(!irqs_disabled());
1220 * don't plug a stopped queue, it must be paired with blk_start_queue()
1221 * which will restart the queueing
1223 if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
1226 if (!test_and_set_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1227 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
1230 EXPORT_SYMBOL(blk_plug_device);
1233 * remove the queue from the plugged list, if present. called with
1234 * queue lock held and interrupts disabled.
1236 int blk_remove_plug(request_queue_t *q)
1238 WARN_ON(!irqs_disabled());
1240 if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags))
1243 del_timer(&q->unplug_timer);
1247 EXPORT_SYMBOL(blk_remove_plug);
1250 * remove the plug and let it rip..
1252 void __generic_unplug_device(request_queue_t *q)
1254 if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
1257 if (!blk_remove_plug(q))
1261 * was plugged, fire request_fn if queue has stuff to do
1263 if (elv_next_request(q))
1266 EXPORT_SYMBOL(__generic_unplug_device);
1269 * generic_unplug_device - fire a request queue
1270 * @q: The &request_queue_t in question
1273 * Linux uses plugging to build bigger requests queues before letting
1274 * the device have at them. If a queue is plugged, the I/O scheduler
1275 * is still adding and merging requests on the queue. Once the queue
1276 * gets unplugged, the request_fn defined for the queue is invoked and
1277 * transfers started.
1279 void generic_unplug_device(request_queue_t *q)
1281 spin_lock_irq(q->queue_lock);
1282 __generic_unplug_device(q);
1283 spin_unlock_irq(q->queue_lock);
1285 EXPORT_SYMBOL(generic_unplug_device);
1287 static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
1290 request_queue_t *q = bdi->unplug_io_data;
1293 * devices don't necessarily have an ->unplug_fn defined
1299 static void blk_unplug_work(void *data)
1301 request_queue_t *q = data;
1306 static void blk_unplug_timeout(unsigned long data)
1308 request_queue_t *q = (request_queue_t *)data;
1310 kblockd_schedule_work(&q->unplug_work);
1314 * blk_start_queue - restart a previously stopped queue
1315 * @q: The &request_queue_t in question
1318 * blk_start_queue() will clear the stop flag on the queue, and call
1319 * the request_fn for the queue if it was in a stopped state when
1320 * entered. Also see blk_stop_queue(). Queue lock must be held.
1322 void blk_start_queue(request_queue_t *q)
1324 clear_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1327 * one level of recursion is ok and is much faster than kicking
1328 * the unplug handling
1330 if (!test_and_set_bit(QUEUE_FLAG_REENTER, &q->queue_flags)) {
1332 clear_bit(QUEUE_FLAG_REENTER, &q->queue_flags);
1335 kblockd_schedule_work(&q->unplug_work);
1339 EXPORT_SYMBOL(blk_start_queue);
1342 * blk_stop_queue - stop a queue
1343 * @q: The &request_queue_t in question
1346 * The Linux block layer assumes that a block driver will consume all
1347 * entries on the request queue when the request_fn strategy is called.
1348 * Often this will not happen, because of hardware limitations (queue
1349 * depth settings). If a device driver gets a 'queue full' response,
1350 * or if it simply chooses not to queue more I/O at one point, it can
1351 * call this function to prevent the request_fn from being called until
1352 * the driver has signalled it's ready to go again. This happens by calling
1353 * blk_start_queue() to restart queue operations. Queue lock must be held.
1355 void blk_stop_queue(request_queue_t *q)
1358 set_bit(QUEUE_FLAG_STOPPED, &q->queue_flags);
1360 EXPORT_SYMBOL(blk_stop_queue);
1363 * blk_sync_queue - cancel any pending callbacks on a queue
1367 * The block layer may perform asynchronous callback activity
1368 * on a queue, such as calling the unplug function after a timeout.
1369 * A block device may call blk_sync_queue to ensure that any
1370 * such activity is cancelled, thus allowing it to release resources
1371 * the the callbacks might use. The caller must already have made sure
1372 * that its ->make_request_fn will not re-add plugging prior to calling
1376 void blk_sync_queue(struct request_queue *q)
1378 del_timer_sync(&q->unplug_timer);
1381 EXPORT_SYMBOL(blk_sync_queue);
1384 * blk_run_queue - run a single device queue
1385 * @q: The queue to run
1387 void blk_run_queue(struct request_queue *q)
1389 unsigned long flags;
1391 spin_lock_irqsave(q->queue_lock, flags);
1394 spin_unlock_irqrestore(q->queue_lock, flags);
1396 EXPORT_SYMBOL(blk_run_queue);
1399 * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1400 * @q: the request queue to be released
1403 * blk_cleanup_queue is the pair to blk_init_queue() or
1404 * blk_queue_make_request(). It should be called when a request queue is
1405 * being released; typically when a block device is being de-registered.
1406 * Currently, its primary task it to free all the &struct request
1407 * structures that were allocated to the queue and the queue itself.
1410 * Hopefully the low level driver will have finished any
1411 * outstanding requests first...
1413 void blk_cleanup_queue(request_queue_t * q)
1415 struct request_list *rl = &q->rq;
1417 if (!atomic_dec_and_test(&q->refcnt))
1421 elevator_exit(q->elevator);
1426 mempool_destroy(rl->rq_pool);
1429 __blk_queue_free_tags(q);
1431 kmem_cache_free(requestq_cachep, q);
1434 EXPORT_SYMBOL(blk_cleanup_queue);
1436 static int blk_init_free_list(request_queue_t *q)
1438 struct request_list *rl = &q->rq;
1440 rl->count[READ] = rl->count[WRITE] = 0;
1441 rl->starved[READ] = rl->starved[WRITE] = 0;
1442 init_waitqueue_head(&rl->wait[READ]);
1443 init_waitqueue_head(&rl->wait[WRITE]);
1444 init_waitqueue_head(&rl->drain);
1446 rl->rq_pool = mempool_create(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, request_cachep);
1454 static int __make_request(request_queue_t *, struct bio *);
1456 request_queue_t *blk_alloc_queue(int gfp_mask)
1458 request_queue_t *q = kmem_cache_alloc(requestq_cachep, gfp_mask);
1463 memset(q, 0, sizeof(*q));
1464 init_timer(&q->unplug_timer);
1465 atomic_set(&q->refcnt, 1);
1467 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
1468 q->backing_dev_info.unplug_io_data = q;
1473 EXPORT_SYMBOL(blk_alloc_queue);
1476 * blk_init_queue - prepare a request queue for use with a block device
1477 * @rfn: The function to be called to process requests that have been
1478 * placed on the queue.
1479 * @lock: Request queue spin lock
1482 * If a block device wishes to use the standard request handling procedures,
1483 * which sorts requests and coalesces adjacent requests, then it must
1484 * call blk_init_queue(). The function @rfn will be called when there
1485 * are requests on the queue that need to be processed. If the device
1486 * supports plugging, then @rfn may not be called immediately when requests
1487 * are available on the queue, but may be called at some time later instead.
1488 * Plugged queues are generally unplugged when a buffer belonging to one
1489 * of the requests on the queue is needed, or due to memory pressure.
1491 * @rfn is not required, or even expected, to remove all requests off the
1492 * queue, but only as many as it can handle at a time. If it does leave
1493 * requests on the queue, it is responsible for arranging that the requests
1494 * get dealt with eventually.
1496 * The queue spin lock must be held while manipulating the requests on the
1499 * Function returns a pointer to the initialized request queue, or NULL if
1500 * it didn't succeed.
1503 * blk_init_queue() must be paired with a blk_cleanup_queue() call
1504 * when the block device is deactivated (such as at module unload).
1506 request_queue_t *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
1508 request_queue_t *q = blk_alloc_queue(GFP_KERNEL);
1513 if (blk_init_free_list(q))
1516 q->request_fn = rfn;
1517 q->back_merge_fn = ll_back_merge_fn;
1518 q->front_merge_fn = ll_front_merge_fn;
1519 q->merge_requests_fn = ll_merge_requests_fn;
1520 q->prep_rq_fn = NULL;
1521 q->unplug_fn = generic_unplug_device;
1522 q->queue_flags = (1 << QUEUE_FLAG_CLUSTER);
1523 q->queue_lock = lock;
1525 blk_queue_segment_boundary(q, 0xffffffff);
1527 blk_queue_make_request(q, __make_request);
1528 blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE);
1530 blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
1531 blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
1536 if (!elevator_init(q, NULL)) {
1537 blk_queue_congestion_threshold(q);
1541 blk_cleanup_queue(q);
1543 kmem_cache_free(requestq_cachep, q);
1547 EXPORT_SYMBOL(blk_init_queue);
1549 int blk_get_queue(request_queue_t *q)
1551 if (!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)) {
1552 atomic_inc(&q->refcnt);
1559 EXPORT_SYMBOL(blk_get_queue);
1561 static inline void blk_free_request(request_queue_t *q, struct request *rq)
1563 elv_put_request(q, rq);
1564 mempool_free(rq, q->rq.rq_pool);
1567 static inline struct request *blk_alloc_request(request_queue_t *q, int rw,
1570 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
1576 * first three bits are identical in rq->flags and bio->bi_rw,
1577 * see bio.h and blkdev.h
1581 if (!elv_set_request(q, rq, gfp_mask))
1584 mempool_free(rq, q->rq.rq_pool);
1589 * ioc_batching returns true if the ioc is a valid batching request and
1590 * should be given priority access to a request.
1592 static inline int ioc_batching(request_queue_t *q, struct io_context *ioc)
1598 * Make sure the process is able to allocate at least 1 request
1599 * even if the batch times out, otherwise we could theoretically
1602 return ioc->nr_batch_requests == q->nr_batching ||
1603 (ioc->nr_batch_requests > 0
1604 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
1608 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
1609 * will cause the process to be a "batcher" on all queues in the system. This
1610 * is the behaviour we want though - once it gets a wakeup it should be given
1613 void ioc_set_batching(request_queue_t *q, struct io_context *ioc)
1615 if (!ioc || ioc_batching(q, ioc))
1618 ioc->nr_batch_requests = q->nr_batching;
1619 ioc->last_waited = jiffies;
1622 static void __freed_request(request_queue_t *q, int rw)
1624 struct request_list *rl = &q->rq;
1626 if (rl->count[rw] < queue_congestion_off_threshold(q))
1627 clear_queue_congested(q, rw);
1629 if (rl->count[rw] + 1 <= q->nr_requests) {
1631 if (waitqueue_active(&rl->wait[rw]))
1632 wake_up(&rl->wait[rw]);
1634 blk_clear_queue_full(q, rw);
1639 * A request has just been released. Account for it, update the full and
1640 * congestion status, wake up any waiters. Called under q->queue_lock.
1642 static void freed_request(request_queue_t *q, int rw)
1644 struct request_list *rl = &q->rq;
1648 __freed_request(q, rw);
1650 if (unlikely(rl->starved[rw ^ 1]))
1651 __freed_request(q, rw ^ 1);
1653 if (!rl->count[READ] && !rl->count[WRITE]) {
1655 if (unlikely(waitqueue_active(&rl->drain)))
1656 wake_up(&rl->drain);
1660 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
1662 * Get a free request, queue_lock must not be held
1664 static struct request *get_request(request_queue_t *q, int rw, int gfp_mask)
1666 struct request *rq = NULL;
1667 struct request_list *rl = &q->rq;
1668 struct io_context *ioc = get_io_context(gfp_mask);
1670 if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)))
1673 spin_lock_irq(q->queue_lock);
1674 if (rl->count[rw]+1 >= q->nr_requests) {
1676 * The queue will fill after this allocation, so set it as
1677 * full, and mark this process as "batching". This process
1678 * will be allowed to complete a batch of requests, others
1681 if (!blk_queue_full(q, rw)) {
1682 ioc_set_batching(q, ioc);
1683 blk_set_queue_full(q, rw);
1687 switch (elv_may_queue(q, rw)) {
1690 case ELV_MQUEUE_MAY:
1692 case ELV_MQUEUE_MUST:
1696 if (blk_queue_full(q, rw) && !ioc_batching(q, ioc)) {
1698 * The queue is full and the allocating process is not a
1699 * "batcher", and not exempted by the IO scheduler
1701 spin_unlock_irq(q->queue_lock);
1707 rl->starved[rw] = 0;
1708 if (rl->count[rw] >= queue_congestion_on_threshold(q))
1709 set_queue_congested(q, rw);
1710 spin_unlock_irq(q->queue_lock);
1712 rq = blk_alloc_request(q, rw, gfp_mask);
1715 * Allocation failed presumably due to memory. Undo anything
1716 * we might have messed up.
1718 * Allocating task should really be put onto the front of the
1719 * wait queue, but this is pretty rare.
1721 spin_lock_irq(q->queue_lock);
1722 freed_request(q, rw);
1725 * in the very unlikely event that allocation failed and no
1726 * requests for this direction was pending, mark us starved
1727 * so that freeing of a request in the other direction will
1728 * notice us. another possible fix would be to split the
1729 * rq mempool into READ and WRITE
1732 if (unlikely(rl->count[rw] == 0))
1733 rl->starved[rw] = 1;
1735 spin_unlock_irq(q->queue_lock);
1739 if (ioc_batching(q, ioc))
1740 ioc->nr_batch_requests--;
1742 INIT_LIST_HEAD(&rq->queuelist);
1745 rq->rq_status = RQ_ACTIVE;
1746 rq->bio = rq->biotail = NULL;
1758 put_io_context(ioc);
1763 * No available requests for this queue, unplug the device and wait for some
1764 * requests to become available.
1766 static struct request *get_request_wait(request_queue_t *q, int rw)
1771 generic_unplug_device(q);
1773 struct request_list *rl = &q->rq;
1775 prepare_to_wait_exclusive(&rl->wait[rw], &wait,
1776 TASK_UNINTERRUPTIBLE);
1778 rq = get_request(q, rw, GFP_NOIO);
1781 struct io_context *ioc;
1786 * After sleeping, we become a "batching" process and
1787 * will be able to allocate at least one request, and
1788 * up to a big batch of them for a small period time.
1789 * See ioc_batching, ioc_set_batching
1791 ioc = get_io_context(GFP_NOIO);
1792 ioc_set_batching(q, ioc);
1793 put_io_context(ioc);
1795 finish_wait(&rl->wait[rw], &wait);
1801 struct request *blk_get_request(request_queue_t *q, int rw, int gfp_mask)
1805 BUG_ON(rw != READ && rw != WRITE);
1807 if (gfp_mask & __GFP_WAIT)
1808 rq = get_request_wait(q, rw);
1810 rq = get_request(q, rw, gfp_mask);
1815 EXPORT_SYMBOL(blk_get_request);
1818 * blk_requeue_request - put a request back on queue
1819 * @q: request queue where request should be inserted
1820 * @rq: request to be inserted
1823 * Drivers often keep queueing requests until the hardware cannot accept
1824 * more, when that condition happens we need to put the request back
1825 * on the queue. Must be called with queue lock held.
1827 void blk_requeue_request(request_queue_t *q, struct request *rq)
1829 if (blk_rq_tagged(rq))
1830 blk_queue_end_tag(q, rq);
1832 elv_requeue_request(q, rq);
1835 EXPORT_SYMBOL(blk_requeue_request);
1838 * blk_insert_request - insert a special request in to a request queue
1839 * @q: request queue where request should be inserted
1840 * @rq: request to be inserted
1841 * @at_head: insert request at head or tail of queue
1842 * @data: private data
1843 * @reinsert: true if request it a reinsertion of previously processed one
1846 * Many block devices need to execute commands asynchronously, so they don't
1847 * block the whole kernel from preemption during request execution. This is
1848 * accomplished normally by inserting aritficial requests tagged as
1849 * REQ_SPECIAL in to the corresponding request queue, and letting them be
1850 * scheduled for actual execution by the request queue.
1852 * We have the option of inserting the head or the tail of the queue.
1853 * Typically we use the tail for new ioctls and so forth. We use the head
1854 * of the queue for things like a QUEUE_FULL message from a device, or a
1855 * host that is unable to accept a particular command.
1857 void blk_insert_request(request_queue_t *q, struct request *rq,
1858 int at_head, void *data, int reinsert)
1860 unsigned long flags;
1863 * tell I/O scheduler that this isn't a regular read/write (ie it
1864 * must not attempt merges on this) and that it acts as a soft
1867 rq->flags |= REQ_SPECIAL | REQ_SOFTBARRIER;
1871 spin_lock_irqsave(q->queue_lock, flags);
1874 * If command is tagged, release the tag
1877 blk_requeue_request(q, rq);
1879 int where = ELEVATOR_INSERT_BACK;
1882 where = ELEVATOR_INSERT_FRONT;
1884 if (blk_rq_tagged(rq))
1885 blk_queue_end_tag(q, rq);
1887 drive_stat_acct(rq, rq->nr_sectors, 1);
1888 __elv_add_request(q, rq, where, 0);
1890 if (blk_queue_plugged(q))
1891 __generic_unplug_device(q);
1894 spin_unlock_irqrestore(q->queue_lock, flags);
1897 EXPORT_SYMBOL(blk_insert_request);
1900 * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
1901 * @q: request queue where request should be inserted
1902 * @rw: READ or WRITE data
1903 * @ubuf: the user buffer
1904 * @len: length of user data
1907 * Data will be mapped directly for zero copy io, if possible. Otherwise
1908 * a kernel bounce buffer is used.
1910 * A matching blk_rq_unmap_user() must be issued at the end of io, while
1911 * still in process context.
1913 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
1914 * before being submitted to the device, as pages mapped may be out of
1915 * reach. It's the callers responsibility to make sure this happens. The
1916 * original bio must be passed back in to blk_rq_unmap_user() for proper
1919 struct request *blk_rq_map_user(request_queue_t *q, int rw, void __user *ubuf,
1922 unsigned long uaddr;
1926 if (len > (q->max_sectors << 9))
1927 return ERR_PTR(-EINVAL);
1928 if ((!len && ubuf) || (len && !ubuf))
1929 return ERR_PTR(-EINVAL);
1931 rq = blk_get_request(q, rw, __GFP_WAIT);
1933 return ERR_PTR(-ENOMEM);
1936 * if alignment requirement is satisfied, map in user pages for
1937 * direct dma. else, set up kernel bounce buffers
1939 uaddr = (unsigned long) ubuf;
1940 if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
1941 bio = bio_map_user(q, NULL, uaddr, len, rw == READ);
1943 bio = bio_copy_user(q, uaddr, len, rw == READ);
1946 rq->bio = rq->biotail = bio;
1947 blk_rq_bio_prep(q, rq, bio);
1949 rq->buffer = rq->data = NULL;
1955 * bio is the err-ptr
1957 blk_put_request(rq);
1958 return (struct request *) bio;
1961 EXPORT_SYMBOL(blk_rq_map_user);
1964 * blk_rq_unmap_user - unmap a request with user data
1965 * @rq: request to be unmapped
1966 * @ubuf: user buffer
1967 * @ulen: length of user buffer
1970 * Unmap a request previously mapped by blk_rq_map_user().
1972 int blk_rq_unmap_user(struct request *rq, struct bio *bio, unsigned int ulen)
1977 if (bio_flagged(bio, BIO_USER_MAPPED))
1978 bio_unmap_user(bio);
1980 ret = bio_uncopy_user(bio);
1983 blk_put_request(rq);
1987 EXPORT_SYMBOL(blk_rq_unmap_user);
1990 * blk_execute_rq - insert a request into queue for execution
1991 * @q: queue to insert the request in
1992 * @bd_disk: matching gendisk
1993 * @rq: request to insert
1996 * Insert a fully prepared request at the back of the io scheduler queue
1999 int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
2002 DECLARE_COMPLETION(wait);
2003 char sense[SCSI_SENSE_BUFFERSIZE];
2006 rq->rq_disk = bd_disk;
2009 * we need an extra reference to the request, so we can look at
2010 * it after io completion
2015 memset(sense, 0, sizeof(sense));
2020 rq->flags |= REQ_NOMERGE;
2022 rq->waiting = &wait;
2023 elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
2024 generic_unplug_device(q);
2025 wait_for_completion(rq->waiting);
2034 EXPORT_SYMBOL(blk_execute_rq);
2037 * blkdev_issue_flush - queue a flush
2038 * @bdev: blockdev to issue flush for
2039 * @error_sector: error sector
2042 * Issue a flush for the block device in question. Caller can supply
2043 * room for storing the error offset in case of a flush error, if they
2044 * wish to. Caller must run wait_for_completion() on its own.
2046 int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
2050 if (bdev->bd_disk == NULL)
2053 q = bdev_get_queue(bdev);
2056 if (!q->issue_flush_fn)
2059 return q->issue_flush_fn(q, bdev->bd_disk, error_sector);
2062 EXPORT_SYMBOL(blkdev_issue_flush);
2065 * blkdev_scsi_issue_flush_fn - issue flush for SCSI devices
2068 * @error_sector: error offset
2071 * Devices understanding the SCSI command set, can use this function as
2072 * a helper for issuing a cache flush. Note: driver is required to store
2073 * the error offset (in case of error flushing) in ->sector of struct
2076 int blkdev_scsi_issue_flush_fn(request_queue_t *q, struct gendisk *disk,
2077 sector_t *error_sector)
2079 struct request *rq = blk_get_request(q, WRITE, __GFP_WAIT);
2082 rq->flags |= REQ_BLOCK_PC | REQ_SOFTBARRIER;
2084 memset(rq->cmd, 0, sizeof(rq->cmd));
2089 rq->timeout = 60 * HZ;
2091 ret = blk_execute_rq(q, disk, rq);
2093 if (ret && error_sector)
2094 *error_sector = rq->sector;
2096 blk_put_request(rq);
2100 EXPORT_SYMBOL(blkdev_scsi_issue_flush_fn);
2102 void drive_stat_acct(struct request *rq, int nr_sectors, int new_io)
2104 int rw = rq_data_dir(rq);
2106 if (!blk_fs_request(rq) || !rq->rq_disk)
2110 __disk_stat_add(rq->rq_disk, read_sectors, nr_sectors);
2112 __disk_stat_inc(rq->rq_disk, read_merges);
2113 } else if (rw == WRITE) {
2114 __disk_stat_add(rq->rq_disk, write_sectors, nr_sectors);
2116 __disk_stat_inc(rq->rq_disk, write_merges);
2119 disk_round_stats(rq->rq_disk);
2120 rq->rq_disk->in_flight++;
2125 * add-request adds a request to the linked list.
2126 * queue lock is held and interrupts disabled, as we muck with the
2127 * request queue list.
2129 static inline void add_request(request_queue_t * q, struct request * req)
2131 drive_stat_acct(req, req->nr_sectors, 1);
2134 q->activity_fn(q->activity_data, rq_data_dir(req));
2137 * elevator indicated where it wants this request to be
2138 * inserted at elevator_merge time
2140 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
2144 * disk_round_stats() - Round off the performance stats on a struct
2147 * The average IO queue length and utilisation statistics are maintained
2148 * by observing the current state of the queue length and the amount of
2149 * time it has been in this state for.
2151 * Normally, that accounting is done on IO completion, but that can result
2152 * in more than a second's worth of IO being accounted for within any one
2153 * second, leading to >100% utilisation. To deal with that, we call this
2154 * function to do a round-off before returning the results when reading
2155 * /proc/diskstats. This accounts immediately for all queue usage up to
2156 * the current jiffies and restarts the counters again.
2158 void disk_round_stats(struct gendisk *disk)
2160 unsigned long now = jiffies;
2162 __disk_stat_add(disk, time_in_queue,
2163 disk->in_flight * (now - disk->stamp));
2166 if (disk->in_flight)
2167 __disk_stat_add(disk, io_ticks, (now - disk->stamp_idle));
2168 disk->stamp_idle = now;
2172 * queue lock must be held
2174 void __blk_put_request(request_queue_t *q, struct request *req)
2176 struct request_list *rl = req->rl;
2180 if (unlikely(--req->ref_count))
2183 req->rq_status = RQ_INACTIVE;
2188 * Request may not have originated from ll_rw_blk. if not,
2189 * it didn't come out of our reserved rq pools
2192 int rw = rq_data_dir(req);
2194 elv_completed_request(q, req);
2196 BUG_ON(!list_empty(&req->queuelist));
2198 blk_free_request(q, req);
2199 freed_request(q, rw);
2203 void blk_put_request(struct request *req)
2206 * if req->rl isn't set, this request didnt originate from the
2207 * block layer, so it's safe to just disregard it
2210 unsigned long flags;
2211 request_queue_t *q = req->q;
2213 spin_lock_irqsave(q->queue_lock, flags);
2214 __blk_put_request(q, req);
2215 spin_unlock_irqrestore(q->queue_lock, flags);
2219 EXPORT_SYMBOL(blk_put_request);
2222 * blk_congestion_wait - wait for a queue to become uncongested
2223 * @rw: READ or WRITE
2224 * @timeout: timeout in jiffies
2226 * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2227 * If no queues are congested then just wait for the next request to be
2230 long blk_congestion_wait(int rw, long timeout)
2234 wait_queue_head_t *wqh = &congestion_wqh[rw];
2236 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
2237 ret = io_schedule_timeout(timeout);
2238 finish_wait(wqh, &wait);
2242 EXPORT_SYMBOL(blk_congestion_wait);
2245 * Has to be called with the request spinlock acquired
2247 static int attempt_merge(request_queue_t *q, struct request *req,
2248 struct request *next)
2250 if (!rq_mergeable(req) || !rq_mergeable(next))
2256 if (req->sector + req->nr_sectors != next->sector)
2259 if (rq_data_dir(req) != rq_data_dir(next)
2260 || req->rq_disk != next->rq_disk
2261 || next->waiting || next->special)
2265 * If we are allowed to merge, then append bio list
2266 * from next to rq and release next. merge_requests_fn
2267 * will have updated segment counts, update sector
2270 if (!q->merge_requests_fn(q, req, next))
2274 * At this point we have either done a back merge
2275 * or front merge. We need the smaller start_time of
2276 * the merged requests to be the current request
2277 * for accounting purposes.
2279 if (time_after(req->start_time, next->start_time))
2280 req->start_time = next->start_time;
2282 req->biotail->bi_next = next->bio;
2283 req->biotail = next->biotail;
2285 req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
2287 elv_merge_requests(q, req, next);
2290 disk_round_stats(req->rq_disk);
2291 req->rq_disk->in_flight--;
2294 __blk_put_request(q, next);
2298 static inline int attempt_back_merge(request_queue_t *q, struct request *rq)
2300 struct request *next = elv_latter_request(q, rq);
2303 return attempt_merge(q, rq, next);
2308 static inline int attempt_front_merge(request_queue_t *q, struct request *rq)
2310 struct request *prev = elv_former_request(q, rq);
2313 return attempt_merge(q, prev, rq);
2319 * blk_attempt_remerge - attempt to remerge active head with next request
2320 * @q: The &request_queue_t belonging to the device
2321 * @rq: The head request (usually)
2324 * For head-active devices, the queue can easily be unplugged so quickly
2325 * that proper merging is not done on the front request. This may hurt
2326 * performance greatly for some devices. The block layer cannot safely
2327 * do merging on that first request for these queues, but the driver can
2328 * call this function and make it happen any way. Only the driver knows
2329 * when it is safe to do so.
2331 void blk_attempt_remerge(request_queue_t *q, struct request *rq)
2333 unsigned long flags;
2335 spin_lock_irqsave(q->queue_lock, flags);
2336 attempt_back_merge(q, rq);
2337 spin_unlock_irqrestore(q->queue_lock, flags);
2340 EXPORT_SYMBOL(blk_attempt_remerge);
2343 * Non-locking blk_attempt_remerge variant.
2345 void __blk_attempt_remerge(request_queue_t *q, struct request *rq)
2347 attempt_back_merge(q, rq);
2350 EXPORT_SYMBOL(__blk_attempt_remerge);
2352 static int __make_request(request_queue_t *q, struct bio *bio)
2354 struct request *req, *freereq = NULL;
2355 int el_ret, rw, nr_sectors, cur_nr_sectors, barrier, err;
2358 sector = bio->bi_sector;
2359 nr_sectors = bio_sectors(bio);
2360 cur_nr_sectors = bio_cur_sectors(bio);
2362 rw = bio_data_dir(bio);
2365 * low level driver can indicate that it wants pages above a
2366 * certain limit bounced to low memory (ie for highmem, or even
2367 * ISA dma in theory)
2369 blk_queue_bounce(q, &bio);
2371 spin_lock_prefetch(q->queue_lock);
2373 barrier = bio_barrier(bio);
2374 if (barrier && !(q->queue_flags & (1 << QUEUE_FLAG_ORDERED))) {
2380 spin_lock_irq(q->queue_lock);
2382 if (elv_queue_empty(q)) {
2389 el_ret = elv_merge(q, &req, bio);
2391 case ELEVATOR_BACK_MERGE:
2392 BUG_ON(!rq_mergeable(req));
2394 if (!q->back_merge_fn(q, req, bio))
2397 req->biotail->bi_next = bio;
2399 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2400 drive_stat_acct(req, nr_sectors, 0);
2401 if (!attempt_back_merge(q, req))
2402 elv_merged_request(q, req);
2405 case ELEVATOR_FRONT_MERGE:
2406 BUG_ON(!rq_mergeable(req));
2408 if (!q->front_merge_fn(q, req, bio))
2411 bio->bi_next = req->bio;
2415 * may not be valid. if the low level driver said
2416 * it didn't need a bounce buffer then it better
2417 * not touch req->buffer either...
2419 req->buffer = bio_data(bio);
2420 req->current_nr_sectors = cur_nr_sectors;
2421 req->hard_cur_sectors = cur_nr_sectors;
2422 req->sector = req->hard_sector = sector;
2423 req->nr_sectors = req->hard_nr_sectors += nr_sectors;
2424 drive_stat_acct(req, nr_sectors, 0);
2425 if (!attempt_front_merge(q, req))
2426 elv_merged_request(q, req);
2430 * elevator says don't/can't merge. get new request
2432 case ELEVATOR_NO_MERGE:
2436 printk("elevator returned crap (%d)\n", el_ret);
2441 * Grab a free request from the freelist - if that is empty, check
2442 * if we are doing read ahead and abort instead of blocking for
2450 spin_unlock_irq(q->queue_lock);
2451 if ((freereq = get_request(q, rw, GFP_ATOMIC)) == NULL) {
2456 if (bio_rw_ahead(bio))
2459 freereq = get_request_wait(q, rw);
2464 req->flags |= REQ_CMD;
2467 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2469 if (bio_rw_ahead(bio) || bio_failfast(bio))
2470 req->flags |= REQ_FAILFAST;
2473 * REQ_BARRIER implies no merging, but lets make it explicit
2476 req->flags |= (REQ_HARDBARRIER | REQ_NOMERGE);
2479 req->hard_sector = req->sector = sector;
2480 req->hard_nr_sectors = req->nr_sectors = nr_sectors;
2481 req->current_nr_sectors = req->hard_cur_sectors = cur_nr_sectors;
2482 req->nr_phys_segments = bio_phys_segments(q, bio);
2483 req->nr_hw_segments = bio_hw_segments(q, bio);
2484 req->buffer = bio_data(bio); /* see ->buffer comment above */
2485 req->waiting = NULL;
2486 req->bio = req->biotail = bio;
2487 req->rq_disk = bio->bi_bdev->bd_disk;
2488 req->start_time = jiffies;
2490 add_request(q, req);
2493 __blk_put_request(q, freereq);
2495 __generic_unplug_device(q);
2497 spin_unlock_irq(q->queue_lock);
2501 bio_endio(bio, nr_sectors << 9, err);
2506 * If bio->bi_dev is a partition, remap the location
2508 static inline void blk_partition_remap(struct bio *bio)
2510 struct block_device *bdev = bio->bi_bdev;
2512 if (bdev != bdev->bd_contains) {
2513 struct hd_struct *p = bdev->bd_part;
2515 switch (bio->bi_rw) {
2517 p->read_sectors += bio_sectors(bio);
2521 p->write_sectors += bio_sectors(bio);
2525 bio->bi_sector += p->start_sect;
2526 bio->bi_bdev = bdev->bd_contains;
2530 void blk_finish_queue_drain(request_queue_t *q)
2532 struct request_list *rl = &q->rq;
2535 spin_lock_irq(q->queue_lock);
2536 clear_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2538 while (!list_empty(&q->drain_list)) {
2539 rq = list_entry_rq(q->drain_list.next);
2541 list_del_init(&rq->queuelist);
2542 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
2545 spin_unlock_irq(q->queue_lock);
2547 wake_up(&rl->wait[0]);
2548 wake_up(&rl->wait[1]);
2549 wake_up(&rl->drain);
2552 static int wait_drain(request_queue_t *q, struct request_list *rl, int dispatch)
2554 int wait = rl->count[READ] + rl->count[WRITE];
2557 wait += !list_empty(&q->queue_head);
2563 * We rely on the fact that only requests allocated through blk_alloc_request()
2564 * have io scheduler private data structures associated with them. Any other
2565 * type of request (allocated on stack or through kmalloc()) should not go
2566 * to the io scheduler core, but be attached to the queue head instead.
2568 void blk_wait_queue_drained(request_queue_t *q, int wait_dispatch)
2570 struct request_list *rl = &q->rq;
2573 spin_lock_irq(q->queue_lock);
2574 set_bit(QUEUE_FLAG_DRAIN, &q->queue_flags);
2576 while (wait_drain(q, rl, wait_dispatch)) {
2577 prepare_to_wait(&rl->drain, &wait, TASK_UNINTERRUPTIBLE);
2579 if (wait_drain(q, rl, wait_dispatch)) {
2580 __generic_unplug_device(q);
2581 spin_unlock_irq(q->queue_lock);
2583 spin_lock_irq(q->queue_lock);
2586 finish_wait(&rl->drain, &wait);
2589 spin_unlock_irq(q->queue_lock);
2593 * block waiting for the io scheduler being started again.
2595 static inline void block_wait_queue_running(request_queue_t *q)
2599 while (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
2600 struct request_list *rl = &q->rq;
2602 prepare_to_wait_exclusive(&rl->drain, &wait,
2603 TASK_UNINTERRUPTIBLE);
2606 * re-check the condition. avoids using prepare_to_wait()
2607 * in the fast path (queue is running)
2609 if (test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))
2612 finish_wait(&rl->drain, &wait);
2616 static void handle_bad_sector(struct bio *bio)
2618 char b[BDEVNAME_SIZE];
2620 printk(KERN_INFO "attempt to access beyond end of device\n");
2621 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
2622 bdevname(bio->bi_bdev, b),
2624 (unsigned long long)bio->bi_sector + bio_sectors(bio),
2625 (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
2627 set_bit(BIO_EOF, &bio->bi_flags);
2631 * generic_make_request: hand a buffer to its device driver for I/O
2632 * @bio: The bio describing the location in memory and on the device.
2634 * generic_make_request() is used to make I/O requests of block
2635 * devices. It is passed a &struct bio, which describes the I/O that needs
2638 * generic_make_request() does not return any status. The
2639 * success/failure status of the request, along with notification of
2640 * completion, is delivered asynchronously through the bio->bi_end_io
2641 * function described (one day) else where.
2643 * The caller of generic_make_request must make sure that bi_io_vec
2644 * are set to describe the memory buffer, and that bi_dev and bi_sector are
2645 * set to describe the device address, and the
2646 * bi_end_io and optionally bi_private are set to describe how
2647 * completion notification should be signaled.
2649 * generic_make_request and the drivers it calls may use bi_next if this
2650 * bio happens to be merged with someone else, and may change bi_dev and
2651 * bi_sector for remaps as it sees fit. So the values of these fields
2652 * should NOT be depended on after the call to generic_make_request.
2654 void generic_make_request(struct bio *bio)
2658 int ret, nr_sectors = bio_sectors(bio);
2661 /* Test device or partition size, when known. */
2662 maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
2664 sector_t sector = bio->bi_sector;
2666 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
2668 * This may well happen - the kernel calls bread()
2669 * without checking the size of the device, e.g., when
2670 * mounting a device.
2672 handle_bad_sector(bio);
2678 * Resolve the mapping until finished. (drivers are
2679 * still free to implement/resolve their own stacking
2680 * by explicitly returning 0)
2682 * NOTE: we don't repeat the blk_size check for each new device.
2683 * Stacking drivers are expected to know what they are doing.
2686 char b[BDEVNAME_SIZE];
2688 q = bdev_get_queue(bio->bi_bdev);
2691 "generic_make_request: Trying to access "
2692 "nonexistent block-device %s (%Lu)\n",
2693 bdevname(bio->bi_bdev, b),
2694 (long long) bio->bi_sector);
2696 bio_endio(bio, bio->bi_size, -EIO);
2700 if (unlikely(bio_sectors(bio) > q->max_hw_sectors)) {
2701 printk("bio too big device %s (%u > %u)\n",
2702 bdevname(bio->bi_bdev, b),
2708 if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))
2711 block_wait_queue_running(q);
2714 * If this device has partitions, remap block n
2715 * of partition p to block n+start(p) of the disk.
2717 blk_partition_remap(bio);
2719 ret = q->make_request_fn(q, bio);
2723 EXPORT_SYMBOL(generic_make_request);
2726 * submit_bio: submit a bio to the block device layer for I/O
2727 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
2728 * @bio: The &struct bio which describes the I/O
2730 * submit_bio() is very similar in purpose to generic_make_request(), and
2731 * uses that function to do most of the work. Both are fairly rough
2732 * interfaces, @bio must be presetup and ready for I/O.
2735 void submit_bio(int rw, struct bio *bio)
2737 int count = bio_sectors(bio);
2739 BIO_BUG_ON(!bio->bi_size);
2740 BIO_BUG_ON(!bio->bi_io_vec);
2743 mod_page_state(pgpgout, count);
2745 mod_page_state(pgpgin, count);
2747 if (unlikely(block_dump)) {
2748 char b[BDEVNAME_SIZE];
2749 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
2750 current->comm, current->pid,
2751 (rw & WRITE) ? "WRITE" : "READ",
2752 (unsigned long long)bio->bi_sector,
2753 bdevname(bio->bi_bdev,b));
2756 generic_make_request(bio);
2759 EXPORT_SYMBOL(submit_bio);
2761 void blk_recalc_rq_segments(struct request *rq)
2763 struct bio *bio, *prevbio = NULL;
2764 int nr_phys_segs, nr_hw_segs;
2765 unsigned int phys_size, hw_size;
2766 request_queue_t *q = rq->q;
2771 phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
2772 rq_for_each_bio(bio, rq) {
2773 /* Force bio hw/phys segs to be recalculated. */
2774 bio->bi_flags &= ~(1 << BIO_SEG_VALID);
2776 nr_phys_segs += bio_phys_segments(q, bio);
2777 nr_hw_segs += bio_hw_segments(q, bio);
2779 int pseg = phys_size + prevbio->bi_size + bio->bi_size;
2780 int hseg = hw_size + prevbio->bi_size + bio->bi_size;
2782 if (blk_phys_contig_segment(q, prevbio, bio) &&
2783 pseg <= q->max_segment_size) {
2785 phys_size += prevbio->bi_size + bio->bi_size;
2789 if (blk_hw_contig_segment(q, prevbio, bio) &&
2790 hseg <= q->max_segment_size) {
2792 hw_size += prevbio->bi_size + bio->bi_size;
2799 rq->nr_phys_segments = nr_phys_segs;
2800 rq->nr_hw_segments = nr_hw_segs;
2803 void blk_recalc_rq_sectors(struct request *rq, int nsect)
2805 if (blk_fs_request(rq)) {
2806 rq->hard_sector += nsect;
2807 rq->hard_nr_sectors -= nsect;
2810 * Move the I/O submission pointers ahead if required.
2812 if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
2813 (rq->sector <= rq->hard_sector)) {
2814 rq->sector = rq->hard_sector;
2815 rq->nr_sectors = rq->hard_nr_sectors;
2816 rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
2817 rq->current_nr_sectors = rq->hard_cur_sectors;
2818 rq->buffer = bio_data(rq->bio);
2822 * if total number of sectors is less than the first segment
2823 * size, something has gone terribly wrong
2825 if (rq->nr_sectors < rq->current_nr_sectors) {
2826 printk("blk: request botched\n");
2827 rq->nr_sectors = rq->current_nr_sectors;
2832 static int __end_that_request_first(struct request *req, int uptodate,
2835 int total_bytes, bio_nbytes, error, next_idx = 0;
2839 * extend uptodate bool to allow < 0 value to be direct io error
2842 if (end_io_error(uptodate))
2843 error = !uptodate ? -EIO : uptodate;
2846 * for a REQ_BLOCK_PC request, we want to carry any eventual
2847 * sense key with us all the way through
2849 if (!blk_pc_request(req))
2853 if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
2854 printk("end_request: I/O error, dev %s, sector %llu\n",
2855 req->rq_disk ? req->rq_disk->disk_name : "?",
2856 (unsigned long long)req->sector);
2859 total_bytes = bio_nbytes = 0;
2860 while ((bio = req->bio) != NULL) {
2863 if (nr_bytes >= bio->bi_size) {
2864 req->bio = bio->bi_next;
2865 nbytes = bio->bi_size;
2866 bio_endio(bio, nbytes, error);
2870 int idx = bio->bi_idx + next_idx;
2872 if (unlikely(bio->bi_idx >= bio->bi_vcnt)) {
2873 blk_dump_rq_flags(req, "__end_that");
2874 printk("%s: bio idx %d >= vcnt %d\n",
2876 bio->bi_idx, bio->bi_vcnt);
2880 nbytes = bio_iovec_idx(bio, idx)->bv_len;
2881 BIO_BUG_ON(nbytes > bio->bi_size);
2884 * not a complete bvec done
2886 if (unlikely(nbytes > nr_bytes)) {
2887 bio_nbytes += nr_bytes;
2888 total_bytes += nr_bytes;
2893 * advance to the next vector
2896 bio_nbytes += nbytes;
2899 total_bytes += nbytes;
2902 if ((bio = req->bio)) {
2904 * end more in this run, or just return 'not-done'
2906 if (unlikely(nr_bytes <= 0))
2918 * if the request wasn't completed, update state
2921 bio_endio(bio, bio_nbytes, error);
2922 bio->bi_idx += next_idx;
2923 bio_iovec(bio)->bv_offset += nr_bytes;
2924 bio_iovec(bio)->bv_len -= nr_bytes;
2927 blk_recalc_rq_sectors(req, total_bytes >> 9);
2928 blk_recalc_rq_segments(req);
2933 * end_that_request_first - end I/O on a request
2934 * @req: the request being processed
2935 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
2936 * @nr_sectors: number of sectors to end I/O on
2939 * Ends I/O on a number of sectors attached to @req, and sets it up
2940 * for the next range of segments (if any) in the cluster.
2943 * 0 - we are done with this request, call end_that_request_last()
2944 * 1 - still buffers pending for this request
2946 int end_that_request_first(struct request *req, int uptodate, int nr_sectors)
2948 return __end_that_request_first(req, uptodate, nr_sectors << 9);
2951 EXPORT_SYMBOL(end_that_request_first);
2954 * end_that_request_chunk - end I/O on a request
2955 * @req: the request being processed
2956 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
2957 * @nr_bytes: number of bytes to complete
2960 * Ends I/O on a number of bytes attached to @req, and sets it up
2961 * for the next range of segments (if any). Like end_that_request_first(),
2962 * but deals with bytes instead of sectors.
2965 * 0 - we are done with this request, call end_that_request_last()
2966 * 1 - still buffers pending for this request
2968 int end_that_request_chunk(struct request *req, int uptodate, int nr_bytes)
2970 return __end_that_request_first(req, uptodate, nr_bytes);
2973 EXPORT_SYMBOL(end_that_request_chunk);
2976 * queue lock must be held
2978 void end_that_request_last(struct request *req)
2980 struct gendisk *disk = req->rq_disk;
2981 struct completion *waiting = req->waiting;
2983 if (unlikely(laptop_mode) && blk_fs_request(req))
2984 laptop_io_completion();
2986 if (disk && blk_fs_request(req)) {
2987 unsigned long duration = jiffies - req->start_time;
2988 switch (rq_data_dir(req)) {
2990 __disk_stat_inc(disk, writes);
2991 __disk_stat_add(disk, write_ticks, duration);
2994 __disk_stat_inc(disk, reads);
2995 __disk_stat_add(disk, read_ticks, duration);
2998 disk_round_stats(disk);
3001 __blk_put_request(req->q, req);
3002 /* Do this LAST! The structure may be freed immediately afterwards */
3007 EXPORT_SYMBOL(end_that_request_last);
3009 void end_request(struct request *req, int uptodate)
3011 if (!end_that_request_first(req, uptodate, req->hard_cur_sectors)) {
3012 add_disk_randomness(req->rq_disk);
3013 blkdev_dequeue_request(req);
3014 end_that_request_last(req);
3018 EXPORT_SYMBOL(end_request);
3020 void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct bio *bio)
3022 /* first three bits are identical in rq->flags and bio->bi_rw */
3023 rq->flags |= (bio->bi_rw & 7);
3025 rq->nr_phys_segments = bio_phys_segments(q, bio);
3026 rq->nr_hw_segments = bio_hw_segments(q, bio);
3027 rq->current_nr_sectors = bio_cur_sectors(bio);
3028 rq->hard_cur_sectors = rq->current_nr_sectors;
3029 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio);
3030 rq->buffer = bio_data(bio);
3032 rq->bio = rq->biotail = bio;
3035 EXPORT_SYMBOL(blk_rq_bio_prep);
3037 int kblockd_schedule_work(struct work_struct *work)
3039 return queue_work(kblockd_workqueue, work);
3042 EXPORT_SYMBOL(kblockd_schedule_work);
3044 void kblockd_flush(void)
3046 flush_workqueue(kblockd_workqueue);
3048 EXPORT_SYMBOL(kblockd_flush);
3050 int __init blk_dev_init(void)
3052 kblockd_workqueue = create_workqueue("kblockd");
3053 if (!kblockd_workqueue)
3054 panic("Failed to create kblockd\n");
3056 request_cachep = kmem_cache_create("blkdev_requests",
3057 sizeof(struct request), 0, SLAB_PANIC, NULL, NULL);
3059 requestq_cachep = kmem_cache_create("blkdev_queue",
3060 sizeof(request_queue_t), 0, SLAB_PANIC, NULL, NULL);
3062 iocontext_cachep = kmem_cache_create("blkdev_ioc",
3063 sizeof(struct io_context), 0, SLAB_PANIC, NULL, NULL);
3065 blk_max_low_pfn = max_low_pfn;
3066 blk_max_pfn = max_pfn;
3072 * IO Context helper functions
3074 void put_io_context(struct io_context *ioc)
3079 BUG_ON(atomic_read(&ioc->refcount) == 0);
3081 if (atomic_dec_and_test(&ioc->refcount)) {
3082 if (ioc->aic && ioc->aic->dtor)
3083 ioc->aic->dtor(ioc->aic);
3084 if (ioc->cic && ioc->cic->dtor)
3085 ioc->cic->dtor(ioc->cic);
3087 kmem_cache_free(iocontext_cachep, ioc);
3090 EXPORT_SYMBOL(put_io_context);
3092 /* Called by the exitting task */
3093 void exit_io_context(void)
3095 unsigned long flags;
3096 struct io_context *ioc;
3098 local_irq_save(flags);
3099 ioc = current->io_context;
3100 current->io_context = NULL;
3101 local_irq_restore(flags);
3103 if (ioc->aic && ioc->aic->exit)
3104 ioc->aic->exit(ioc->aic);
3105 if (ioc->cic && ioc->cic->exit)
3106 ioc->cic->exit(ioc->cic);
3108 put_io_context(ioc);
3112 * If the current task has no IO context then create one and initialise it.
3113 * If it does have a context, take a ref on it.
3115 * This is always called in the context of the task which submitted the I/O.
3116 * But weird things happen, so we disable local interrupts to ensure exclusive
3117 * access to *current.
3119 struct io_context *get_io_context(int gfp_flags)
3121 struct task_struct *tsk = current;
3122 unsigned long flags;
3123 struct io_context *ret;
3125 local_irq_save(flags);
3126 ret = tsk->io_context;
3130 local_irq_restore(flags);
3132 ret = kmem_cache_alloc(iocontext_cachep, gfp_flags);
3134 atomic_set(&ret->refcount, 1);
3135 ret->pid = tsk->pid;
3136 ret->last_waited = jiffies; /* doesn't matter... */
3137 ret->nr_batch_requests = 0; /* because this is 0 */
3140 spin_lock_init(&ret->lock);
3142 local_irq_save(flags);
3145 * very unlikely, someone raced with us in setting up the task
3146 * io context. free new context and just grab a reference.
3148 if (!tsk->io_context)
3149 tsk->io_context = ret;
3151 kmem_cache_free(iocontext_cachep, ret);
3152 ret = tsk->io_context;
3156 atomic_inc(&ret->refcount);
3157 local_irq_restore(flags);
3162 EXPORT_SYMBOL(get_io_context);
3164 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
3166 struct io_context *src = *psrc;
3167 struct io_context *dst = *pdst;
3170 BUG_ON(atomic_read(&src->refcount) == 0);
3171 atomic_inc(&src->refcount);
3172 put_io_context(dst);
3176 EXPORT_SYMBOL(copy_io_context);
3178 void swap_io_context(struct io_context **ioc1, struct io_context **ioc2)
3180 struct io_context *temp;
3185 EXPORT_SYMBOL(swap_io_context);
3190 struct queue_sysfs_entry {
3191 struct attribute attr;
3192 ssize_t (*show)(struct request_queue *, char *);
3193 ssize_t (*store)(struct request_queue *, const char *, size_t);
3197 queue_var_show(unsigned int var, char *page)
3199 return sprintf(page, "%d\n", var);
3203 queue_var_store(unsigned long *var, const char *page, size_t count)
3205 char *p = (char *) page;
3207 *var = simple_strtoul(p, &p, 10);
3211 static ssize_t queue_requests_show(struct request_queue *q, char *page)
3213 return queue_var_show(q->nr_requests, (page));
3217 queue_requests_store(struct request_queue *q, const char *page, size_t count)
3219 struct request_list *rl = &q->rq;
3221 int ret = queue_var_store(&q->nr_requests, page, count);
3222 if (q->nr_requests < BLKDEV_MIN_RQ)
3223 q->nr_requests = BLKDEV_MIN_RQ;
3224 blk_queue_congestion_threshold(q);
3226 if (rl->count[READ] >= queue_congestion_on_threshold(q))
3227 set_queue_congested(q, READ);
3228 else if (rl->count[READ] < queue_congestion_off_threshold(q))
3229 clear_queue_congested(q, READ);
3231 if (rl->count[WRITE] >= queue_congestion_on_threshold(q))
3232 set_queue_congested(q, WRITE);
3233 else if (rl->count[WRITE] < queue_congestion_off_threshold(q))
3234 clear_queue_congested(q, WRITE);
3236 if (rl->count[READ] >= q->nr_requests) {
3237 blk_set_queue_full(q, READ);
3238 } else if (rl->count[READ]+1 <= q->nr_requests) {
3239 blk_clear_queue_full(q, READ);
3240 wake_up(&rl->wait[READ]);
3243 if (rl->count[WRITE] >= q->nr_requests) {
3244 blk_set_queue_full(q, WRITE);
3245 } else if (rl->count[WRITE]+1 <= q->nr_requests) {
3246 blk_clear_queue_full(q, WRITE);
3247 wake_up(&rl->wait[WRITE]);
3252 static ssize_t queue_ra_show(struct request_queue *q, char *page)
3254 int ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3256 return queue_var_show(ra_kb, (page));
3260 queue_ra_store(struct request_queue *q, const char *page, size_t count)
3262 unsigned long ra_kb;
3263 ssize_t ret = queue_var_store(&ra_kb, page, count);
3265 spin_lock_irq(q->queue_lock);
3266 if (ra_kb > (q->max_sectors >> 1))
3267 ra_kb = (q->max_sectors >> 1);
3269 q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
3270 spin_unlock_irq(q->queue_lock);
3275 static ssize_t queue_max_sectors_show(struct request_queue *q, char *page)
3277 int max_sectors_kb = q->max_sectors >> 1;
3279 return queue_var_show(max_sectors_kb, (page));
3283 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
3285 unsigned long max_sectors_kb,
3286 max_hw_sectors_kb = q->max_hw_sectors >> 1,
3287 page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
3288 ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
3291 if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
3294 * Take the queue lock to update the readahead and max_sectors
3295 * values synchronously:
3297 spin_lock_irq(q->queue_lock);
3299 * Trim readahead window as well, if necessary:
3301 ra_kb = q->backing_dev_info.ra_pages << (PAGE_CACHE_SHIFT - 10);
3302 if (ra_kb > max_sectors_kb)
3303 q->backing_dev_info.ra_pages =
3304 max_sectors_kb >> (PAGE_CACHE_SHIFT - 10);
3306 q->max_sectors = max_sectors_kb << 1;
3307 spin_unlock_irq(q->queue_lock);
3312 static ssize_t queue_max_hw_sectors_show(struct request_queue *q, char *page)
3314 int max_hw_sectors_kb = q->max_hw_sectors >> 1;
3316 return queue_var_show(max_hw_sectors_kb, (page));
3320 static struct queue_sysfs_entry queue_requests_entry = {
3321 .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
3322 .show = queue_requests_show,
3323 .store = queue_requests_store,
3326 static struct queue_sysfs_entry queue_ra_entry = {
3327 .attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
3328 .show = queue_ra_show,
3329 .store = queue_ra_store,
3332 static struct queue_sysfs_entry queue_max_sectors_entry = {
3333 .attr = {.name = "max_sectors_kb", .mode = S_IRUGO | S_IWUSR },
3334 .show = queue_max_sectors_show,
3335 .store = queue_max_sectors_store,
3338 static struct queue_sysfs_entry queue_max_hw_sectors_entry = {
3339 .attr = {.name = "max_hw_sectors_kb", .mode = S_IRUGO },
3340 .show = queue_max_hw_sectors_show,
3343 static struct queue_sysfs_entry queue_iosched_entry = {
3344 .attr = {.name = "scheduler", .mode = S_IRUGO | S_IWUSR },
3345 .show = elv_iosched_show,
3346 .store = elv_iosched_store,
3349 static struct attribute *default_attrs[] = {
3350 &queue_requests_entry.attr,
3351 &queue_ra_entry.attr,
3352 &queue_max_hw_sectors_entry.attr,
3353 &queue_max_sectors_entry.attr,
3354 &queue_iosched_entry.attr,
3358 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3361 queue_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
3363 struct queue_sysfs_entry *entry = to_queue(attr);
3364 struct request_queue *q;
3366 q = container_of(kobj, struct request_queue, kobj);
3370 return entry->show(q, page);
3374 queue_attr_store(struct kobject *kobj, struct attribute *attr,
3375 const char *page, size_t length)
3377 struct queue_sysfs_entry *entry = to_queue(attr);
3378 struct request_queue *q;
3380 q = container_of(kobj, struct request_queue, kobj);
3384 return entry->store(q, page, length);
3387 static struct sysfs_ops queue_sysfs_ops = {
3388 .show = queue_attr_show,
3389 .store = queue_attr_store,
3392 struct kobj_type queue_ktype = {
3393 .sysfs_ops = &queue_sysfs_ops,
3394 .default_attrs = default_attrs,
3397 int blk_register_queue(struct gendisk *disk)
3401 request_queue_t *q = disk->queue;
3403 if (!q || !q->request_fn)
3406 q->kobj.parent = kobject_get(&disk->kobj);
3407 if (!q->kobj.parent)
3410 snprintf(q->kobj.name, KOBJ_NAME_LEN, "%s", "queue");
3411 q->kobj.ktype = &queue_ktype;
3413 ret = kobject_register(&q->kobj);
3417 ret = elv_register_queue(q);
3419 kobject_unregister(&q->kobj);
3426 void blk_unregister_queue(struct gendisk *disk)
3428 request_queue_t *q = disk->queue;
3430 if (q && q->request_fn) {
3431 elv_unregister_queue(q);
3433 kobject_unregister(&q->kobj);
3434 kobject_put(&disk->kobj);