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>
31 #include <linux/blkdev.h>
36 #include <scsi/scsi_cmnd.h>
38 static void blk_unplug_work(void *data
);
39 static void blk_unplug_timeout(unsigned long data
);
42 * For the allocated request tables
44 static kmem_cache_t
*request_cachep
;
47 * For queue allocation
49 static kmem_cache_t
*requestq_cachep
;
52 * For io context allocations
54 static kmem_cache_t
*iocontext_cachep
;
56 static wait_queue_head_t congestion_wqh
[2] = {
57 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh
[0]),
58 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh
[1])
62 * Controlling structure to kblockd
64 static struct workqueue_struct
*kblockd_workqueue
;
66 unsigned long blk_max_low_pfn
, blk_max_pfn
;
68 EXPORT_SYMBOL(blk_max_low_pfn
);
69 EXPORT_SYMBOL(blk_max_pfn
);
71 /* Amount of time in which a process may batch requests */
72 #define BLK_BATCH_TIME (HZ/50UL)
74 /* Number of requests a "batching" process may submit */
75 #define BLK_BATCH_REQ 32
78 * Return the threshold (number of used requests) at which the queue is
79 * considered to be congested. It include a little hysteresis to keep the
80 * context switch rate down.
82 static inline int queue_congestion_on_threshold(struct request_queue
*q
)
84 return q
->nr_congestion_on
;
88 * The threshold at which a queue is considered to be uncongested
90 static inline int queue_congestion_off_threshold(struct request_queue
*q
)
92 return q
->nr_congestion_off
;
95 static void blk_queue_congestion_threshold(struct request_queue
*q
)
99 nr
= q
->nr_requests
- (q
->nr_requests
/ 8) + 1;
100 if (nr
> q
->nr_requests
)
102 q
->nr_congestion_on
= nr
;
104 nr
= q
->nr_requests
- (q
->nr_requests
/ 8) - (q
->nr_requests
/ 16) - 1;
107 q
->nr_congestion_off
= nr
;
111 * A queue has just exitted congestion. Note this in the global counter of
112 * congested queues, and wake up anyone who was waiting for requests to be
115 static void clear_queue_congested(request_queue_t
*q
, int rw
)
118 wait_queue_head_t
*wqh
= &congestion_wqh
[rw
];
120 bit
= (rw
== WRITE
) ? BDI_write_congested
: BDI_read_congested
;
121 clear_bit(bit
, &q
->backing_dev_info
.state
);
122 smp_mb__after_clear_bit();
123 if (waitqueue_active(wqh
))
128 * A queue has just entered congestion. Flag that in the queue's VM-visible
129 * state flags and increment the global gounter of congested queues.
131 static void set_queue_congested(request_queue_t
*q
, int rw
)
135 bit
= (rw
== WRITE
) ? BDI_write_congested
: BDI_read_congested
;
136 set_bit(bit
, &q
->backing_dev_info
.state
);
140 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
143 * Locates the passed device's request queue and returns the address of its
146 * Will return NULL if the request queue cannot be located.
148 struct backing_dev_info
*blk_get_backing_dev_info(struct block_device
*bdev
)
150 struct backing_dev_info
*ret
= NULL
;
151 request_queue_t
*q
= bdev_get_queue(bdev
);
154 ret
= &q
->backing_dev_info
;
158 EXPORT_SYMBOL(blk_get_backing_dev_info
);
160 void blk_queue_activity_fn(request_queue_t
*q
, activity_fn
*fn
, void *data
)
163 q
->activity_data
= data
;
166 EXPORT_SYMBOL(blk_queue_activity_fn
);
169 * blk_queue_prep_rq - set a prepare_request function for queue
171 * @pfn: prepare_request function
173 * It's possible for a queue to register a prepare_request callback which
174 * is invoked before the request is handed to the request_fn. The goal of
175 * the function is to prepare a request for I/O, it can be used to build a
176 * cdb from the request data for instance.
179 void blk_queue_prep_rq(request_queue_t
*q
, prep_rq_fn
*pfn
)
184 EXPORT_SYMBOL(blk_queue_prep_rq
);
187 * blk_queue_merge_bvec - set a merge_bvec function for queue
189 * @mbfn: merge_bvec_fn
191 * Usually queues have static limitations on the max sectors or segments that
192 * we can put in a request. Stacking drivers may have some settings that
193 * are dynamic, and thus we have to query the queue whether it is ok to
194 * add a new bio_vec to a bio at a given offset or not. If the block device
195 * has such limitations, it needs to register a merge_bvec_fn to control
196 * the size of bio's sent to it. Note that a block device *must* allow a
197 * single page to be added to an empty bio. The block device driver may want
198 * to use the bio_split() function to deal with these bio's. By default
199 * no merge_bvec_fn is defined for a queue, and only the fixed limits are
202 void blk_queue_merge_bvec(request_queue_t
*q
, merge_bvec_fn
*mbfn
)
204 q
->merge_bvec_fn
= mbfn
;
207 EXPORT_SYMBOL(blk_queue_merge_bvec
);
210 * blk_queue_make_request - define an alternate make_request function for a device
211 * @q: the request queue for the device to be affected
212 * @mfn: the alternate make_request function
215 * The normal way for &struct bios to be passed to a device
216 * driver is for them to be collected into requests on a request
217 * queue, and then to allow the device driver to select requests
218 * off that queue when it is ready. This works well for many block
219 * devices. However some block devices (typically virtual devices
220 * such as md or lvm) do not benefit from the processing on the
221 * request queue, and are served best by having the requests passed
222 * directly to them. This can be achieved by providing a function
223 * to blk_queue_make_request().
226 * The driver that does this *must* be able to deal appropriately
227 * with buffers in "highmemory". This can be accomplished by either calling
228 * __bio_kmap_atomic() to get a temporary kernel mapping, or by calling
229 * blk_queue_bounce() to create a buffer in normal memory.
231 void blk_queue_make_request(request_queue_t
* q
, make_request_fn
* mfn
)
236 q
->nr_requests
= BLKDEV_MAX_RQ
;
237 q
->max_phys_segments
= MAX_PHYS_SEGMENTS
;
238 q
->max_hw_segments
= MAX_HW_SEGMENTS
;
239 q
->make_request_fn
= mfn
;
240 q
->backing_dev_info
.ra_pages
= (VM_MAX_READAHEAD
* 1024) / PAGE_CACHE_SIZE
;
241 q
->backing_dev_info
.state
= 0;
242 q
->backing_dev_info
.capabilities
= BDI_CAP_MAP_COPY
;
243 blk_queue_max_sectors(q
, MAX_SECTORS
);
244 blk_queue_hardsect_size(q
, 512);
245 blk_queue_dma_alignment(q
, 511);
246 blk_queue_congestion_threshold(q
);
247 q
->nr_batching
= BLK_BATCH_REQ
;
249 q
->unplug_thresh
= 4; /* hmm */
250 q
->unplug_delay
= (3 * HZ
) / 1000; /* 3 milliseconds */
251 if (q
->unplug_delay
== 0)
254 INIT_WORK(&q
->unplug_work
, blk_unplug_work
, q
);
256 q
->unplug_timer
.function
= blk_unplug_timeout
;
257 q
->unplug_timer
.data
= (unsigned long)q
;
260 * by default assume old behaviour and bounce for any highmem page
262 blk_queue_bounce_limit(q
, BLK_BOUNCE_HIGH
);
264 blk_queue_activity_fn(q
, NULL
, NULL
);
266 INIT_LIST_HEAD(&q
->drain_list
);
269 EXPORT_SYMBOL(blk_queue_make_request
);
271 static inline void rq_init(request_queue_t
*q
, struct request
*rq
)
273 INIT_LIST_HEAD(&rq
->queuelist
);
276 rq
->rq_status
= RQ_ACTIVE
;
277 rq
->bio
= rq
->biotail
= NULL
;
287 rq
->end_io_data
= NULL
;
291 * blk_queue_ordered - does this queue support ordered writes
292 * @q: the request queue
296 * For journalled file systems, doing ordered writes on a commit
297 * block instead of explicitly doing wait_on_buffer (which is bad
298 * for performance) can be a big win. Block drivers supporting this
299 * feature should call this function and indicate so.
302 void blk_queue_ordered(request_queue_t
*q
, int flag
)
305 case QUEUE_ORDERED_NONE
:
307 kmem_cache_free(request_cachep
, q
->flush_rq
);
311 case QUEUE_ORDERED_TAG
:
314 case QUEUE_ORDERED_FLUSH
:
317 q
->flush_rq
= kmem_cache_alloc(request_cachep
,
321 printk("blk_queue_ordered: bad value %d\n", flag
);
326 EXPORT_SYMBOL(blk_queue_ordered
);
329 * blk_queue_issue_flush_fn - set function for issuing a flush
330 * @q: the request queue
331 * @iff: the function to be called issuing the flush
334 * If a driver supports issuing a flush command, the support is notified
335 * to the block layer by defining it through this call.
338 void blk_queue_issue_flush_fn(request_queue_t
*q
, issue_flush_fn
*iff
)
340 q
->issue_flush_fn
= iff
;
343 EXPORT_SYMBOL(blk_queue_issue_flush_fn
);
346 * Cache flushing for ordered writes handling
348 static void blk_pre_flush_end_io(struct request
*flush_rq
)
350 struct request
*rq
= flush_rq
->end_io_data
;
351 request_queue_t
*q
= rq
->q
;
353 rq
->flags
|= REQ_BAR_PREFLUSH
;
355 if (!flush_rq
->errors
)
356 elv_requeue_request(q
, rq
);
358 q
->end_flush_fn(q
, flush_rq
);
359 clear_bit(QUEUE_FLAG_FLUSH
, &q
->queue_flags
);
364 static void blk_post_flush_end_io(struct request
*flush_rq
)
366 struct request
*rq
= flush_rq
->end_io_data
;
367 request_queue_t
*q
= rq
->q
;
369 rq
->flags
|= REQ_BAR_POSTFLUSH
;
371 q
->end_flush_fn(q
, flush_rq
);
372 clear_bit(QUEUE_FLAG_FLUSH
, &q
->queue_flags
);
376 struct request
*blk_start_pre_flush(request_queue_t
*q
, struct request
*rq
)
378 struct request
*flush_rq
= q
->flush_rq
;
380 BUG_ON(!blk_barrier_rq(rq
));
382 if (test_and_set_bit(QUEUE_FLAG_FLUSH
, &q
->queue_flags
))
385 rq_init(q
, flush_rq
);
386 flush_rq
->elevator_private
= NULL
;
387 flush_rq
->flags
= REQ_BAR_FLUSH
;
388 flush_rq
->rq_disk
= rq
->rq_disk
;
392 * prepare_flush returns 0 if no flush is needed, just mark both
393 * pre and post flush as done in that case
395 if (!q
->prepare_flush_fn(q
, flush_rq
)) {
396 rq
->flags
|= REQ_BAR_PREFLUSH
| REQ_BAR_POSTFLUSH
;
397 clear_bit(QUEUE_FLAG_FLUSH
, &q
->queue_flags
);
402 * some drivers dequeue requests right away, some only after io
403 * completion. make sure the request is dequeued.
405 if (!list_empty(&rq
->queuelist
))
406 blkdev_dequeue_request(rq
);
408 elv_deactivate_request(q
, rq
);
410 flush_rq
->end_io_data
= rq
;
411 flush_rq
->end_io
= blk_pre_flush_end_io
;
413 __elv_add_request(q
, flush_rq
, ELEVATOR_INSERT_FRONT
, 0);
417 static void blk_start_post_flush(request_queue_t
*q
, struct request
*rq
)
419 struct request
*flush_rq
= q
->flush_rq
;
421 BUG_ON(!blk_barrier_rq(rq
));
423 rq_init(q
, flush_rq
);
424 flush_rq
->elevator_private
= NULL
;
425 flush_rq
->flags
= REQ_BAR_FLUSH
;
426 flush_rq
->rq_disk
= rq
->rq_disk
;
429 if (q
->prepare_flush_fn(q
, flush_rq
)) {
430 flush_rq
->end_io_data
= rq
;
431 flush_rq
->end_io
= blk_post_flush_end_io
;
433 __elv_add_request(q
, flush_rq
, ELEVATOR_INSERT_FRONT
, 0);
438 static inline int blk_check_end_barrier(request_queue_t
*q
, struct request
*rq
,
441 if (sectors
> rq
->nr_sectors
)
442 sectors
= rq
->nr_sectors
;
444 rq
->nr_sectors
-= sectors
;
445 return rq
->nr_sectors
;
448 static int __blk_complete_barrier_rq(request_queue_t
*q
, struct request
*rq
,
449 int sectors
, int queue_locked
)
451 if (q
->ordered
!= QUEUE_ORDERED_FLUSH
)
453 if (!blk_fs_request(rq
) || !blk_barrier_rq(rq
))
455 if (blk_barrier_postflush(rq
))
458 if (!blk_check_end_barrier(q
, rq
, sectors
)) {
459 unsigned long flags
= 0;
462 spin_lock_irqsave(q
->queue_lock
, flags
);
464 blk_start_post_flush(q
, rq
);
467 spin_unlock_irqrestore(q
->queue_lock
, flags
);
474 * blk_complete_barrier_rq - complete possible barrier request
475 * @q: the request queue for the device
477 * @sectors: number of sectors to complete
480 * Used in driver end_io handling to determine whether to postpone
481 * completion of a barrier request until a post flush has been done. This
482 * is the unlocked variant, used if the caller doesn't already hold the
485 int blk_complete_barrier_rq(request_queue_t
*q
, struct request
*rq
, int sectors
)
487 return __blk_complete_barrier_rq(q
, rq
, sectors
, 0);
489 EXPORT_SYMBOL(blk_complete_barrier_rq
);
492 * blk_complete_barrier_rq_locked - complete possible barrier request
493 * @q: the request queue for the device
495 * @sectors: number of sectors to complete
498 * See blk_complete_barrier_rq(). This variant must be used if the caller
499 * holds the queue lock.
501 int blk_complete_barrier_rq_locked(request_queue_t
*q
, struct request
*rq
,
504 return __blk_complete_barrier_rq(q
, rq
, sectors
, 1);
506 EXPORT_SYMBOL(blk_complete_barrier_rq_locked
);
509 * blk_queue_bounce_limit - set bounce buffer limit for queue
510 * @q: the request queue for the device
511 * @dma_addr: bus address limit
514 * Different hardware can have different requirements as to what pages
515 * it can do I/O directly to. A low level driver can call
516 * blk_queue_bounce_limit to have lower memory pages allocated as bounce
517 * buffers for doing I/O to pages residing above @page. By default
518 * the block layer sets this to the highest numbered "low" memory page.
520 void blk_queue_bounce_limit(request_queue_t
*q
, u64 dma_addr
)
522 unsigned long bounce_pfn
= dma_addr
>> PAGE_SHIFT
;
525 * set appropriate bounce gfp mask -- unfortunately we don't have a
526 * full 4GB zone, so we have to resort to low memory for any bounces.
527 * ISA has its own < 16MB zone.
529 if (bounce_pfn
< blk_max_low_pfn
) {
530 BUG_ON(dma_addr
< BLK_BOUNCE_ISA
);
531 init_emergency_isa_pool();
532 q
->bounce_gfp
= GFP_NOIO
| GFP_DMA
;
534 q
->bounce_gfp
= GFP_NOIO
;
536 q
->bounce_pfn
= bounce_pfn
;
539 EXPORT_SYMBOL(blk_queue_bounce_limit
);
542 * blk_queue_max_sectors - set max sectors for a request for this queue
543 * @q: the request queue for the device
544 * @max_sectors: max sectors in the usual 512b unit
547 * Enables a low level driver to set an upper limit on the size of
550 void blk_queue_max_sectors(request_queue_t
*q
, unsigned short max_sectors
)
552 if ((max_sectors
<< 9) < PAGE_CACHE_SIZE
) {
553 max_sectors
= 1 << (PAGE_CACHE_SHIFT
- 9);
554 printk("%s: set to minimum %d\n", __FUNCTION__
, max_sectors
);
557 q
->max_sectors
= q
->max_hw_sectors
= max_sectors
;
560 EXPORT_SYMBOL(blk_queue_max_sectors
);
563 * blk_queue_max_phys_segments - set max phys segments for a request for this queue
564 * @q: the request queue for the device
565 * @max_segments: max number of segments
568 * Enables a low level driver to set an upper limit on the number of
569 * physical data segments in a request. This would be the largest sized
570 * scatter list the driver could handle.
572 void blk_queue_max_phys_segments(request_queue_t
*q
, unsigned short max_segments
)
576 printk("%s: set to minimum %d\n", __FUNCTION__
, max_segments
);
579 q
->max_phys_segments
= max_segments
;
582 EXPORT_SYMBOL(blk_queue_max_phys_segments
);
585 * blk_queue_max_hw_segments - set max hw segments for a request for this queue
586 * @q: the request queue for the device
587 * @max_segments: max number of segments
590 * Enables a low level driver to set an upper limit on the number of
591 * hw data segments in a request. This would be the largest number of
592 * address/length pairs the host adapter can actually give as once
595 void blk_queue_max_hw_segments(request_queue_t
*q
, unsigned short max_segments
)
599 printk("%s: set to minimum %d\n", __FUNCTION__
, max_segments
);
602 q
->max_hw_segments
= max_segments
;
605 EXPORT_SYMBOL(blk_queue_max_hw_segments
);
608 * blk_queue_max_segment_size - set max segment size for blk_rq_map_sg
609 * @q: the request queue for the device
610 * @max_size: max size of segment in bytes
613 * Enables a low level driver to set an upper limit on the size of a
616 void blk_queue_max_segment_size(request_queue_t
*q
, unsigned int max_size
)
618 if (max_size
< PAGE_CACHE_SIZE
) {
619 max_size
= PAGE_CACHE_SIZE
;
620 printk("%s: set to minimum %d\n", __FUNCTION__
, max_size
);
623 q
->max_segment_size
= max_size
;
626 EXPORT_SYMBOL(blk_queue_max_segment_size
);
629 * blk_queue_hardsect_size - set hardware sector size for the queue
630 * @q: the request queue for the device
631 * @size: the hardware sector size, in bytes
634 * This should typically be set to the lowest possible sector size
635 * that the hardware can operate on (possible without reverting to
636 * even internal read-modify-write operations). Usually the default
637 * of 512 covers most hardware.
639 void blk_queue_hardsect_size(request_queue_t
*q
, unsigned short size
)
641 q
->hardsect_size
= size
;
644 EXPORT_SYMBOL(blk_queue_hardsect_size
);
647 * Returns the minimum that is _not_ zero, unless both are zero.
649 #define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
652 * blk_queue_stack_limits - inherit underlying queue limits for stacked drivers
653 * @t: the stacking driver (top)
654 * @b: the underlying device (bottom)
656 void blk_queue_stack_limits(request_queue_t
*t
, request_queue_t
*b
)
658 /* zero is "infinity" */
659 t
->max_sectors
= t
->max_hw_sectors
=
660 min_not_zero(t
->max_sectors
,b
->max_sectors
);
662 t
->max_phys_segments
= min(t
->max_phys_segments
,b
->max_phys_segments
);
663 t
->max_hw_segments
= min(t
->max_hw_segments
,b
->max_hw_segments
);
664 t
->max_segment_size
= min(t
->max_segment_size
,b
->max_segment_size
);
665 t
->hardsect_size
= max(t
->hardsect_size
,b
->hardsect_size
);
668 EXPORT_SYMBOL(blk_queue_stack_limits
);
671 * blk_queue_segment_boundary - set boundary rules for segment merging
672 * @q: the request queue for the device
673 * @mask: the memory boundary mask
675 void blk_queue_segment_boundary(request_queue_t
*q
, unsigned long mask
)
677 if (mask
< PAGE_CACHE_SIZE
- 1) {
678 mask
= PAGE_CACHE_SIZE
- 1;
679 printk("%s: set to minimum %lx\n", __FUNCTION__
, mask
);
682 q
->seg_boundary_mask
= mask
;
685 EXPORT_SYMBOL(blk_queue_segment_boundary
);
688 * blk_queue_dma_alignment - set dma length and memory alignment
689 * @q: the request queue for the device
690 * @mask: alignment mask
693 * set required memory and length aligment for direct dma transactions.
694 * this is used when buiding direct io requests for the queue.
697 void blk_queue_dma_alignment(request_queue_t
*q
, int mask
)
699 q
->dma_alignment
= mask
;
702 EXPORT_SYMBOL(blk_queue_dma_alignment
);
705 * blk_queue_find_tag - find a request by its tag and queue
707 * @q: The request queue for the device
708 * @tag: The tag of the request
711 * Should be used when a device returns a tag and you want to match
714 * no locks need be held.
716 struct request
*blk_queue_find_tag(request_queue_t
*q
, int tag
)
718 struct blk_queue_tag
*bqt
= q
->queue_tags
;
720 if (unlikely(bqt
== NULL
|| tag
>= bqt
->max_depth
))
723 return bqt
->tag_index
[tag
];
726 EXPORT_SYMBOL(blk_queue_find_tag
);
729 * __blk_queue_free_tags - release tag maintenance info
730 * @q: the request queue for the device
733 * blk_cleanup_queue() will take care of calling this function, if tagging
734 * has been used. So there's no need to call this directly.
736 static void __blk_queue_free_tags(request_queue_t
*q
)
738 struct blk_queue_tag
*bqt
= q
->queue_tags
;
743 if (atomic_dec_and_test(&bqt
->refcnt
)) {
745 BUG_ON(!list_empty(&bqt
->busy_list
));
747 kfree(bqt
->tag_index
);
748 bqt
->tag_index
= NULL
;
756 q
->queue_tags
= NULL
;
757 q
->queue_flags
&= ~(1 << QUEUE_FLAG_QUEUED
);
761 * blk_queue_free_tags - release tag maintenance info
762 * @q: the request queue for the device
765 * This is used to disabled tagged queuing to a device, yet leave
768 void blk_queue_free_tags(request_queue_t
*q
)
770 clear_bit(QUEUE_FLAG_QUEUED
, &q
->queue_flags
);
773 EXPORT_SYMBOL(blk_queue_free_tags
);
776 init_tag_map(request_queue_t
*q
, struct blk_queue_tag
*tags
, int depth
)
778 struct request
**tag_index
;
779 unsigned long *tag_map
;
782 if (depth
> q
->nr_requests
* 2) {
783 depth
= q
->nr_requests
* 2;
784 printk(KERN_ERR
"%s: adjusted depth to %d\n",
785 __FUNCTION__
, depth
);
788 tag_index
= kmalloc(depth
* sizeof(struct request
*), GFP_ATOMIC
);
792 nr_ulongs
= ALIGN(depth
, BITS_PER_LONG
) / BITS_PER_LONG
;
793 tag_map
= kmalloc(nr_ulongs
* sizeof(unsigned long), GFP_ATOMIC
);
797 memset(tag_index
, 0, depth
* sizeof(struct request
*));
798 memset(tag_map
, 0, nr_ulongs
* sizeof(unsigned long));
799 tags
->max_depth
= depth
;
800 tags
->tag_index
= tag_index
;
801 tags
->tag_map
= tag_map
;
810 * blk_queue_init_tags - initialize the queue tag info
811 * @q: the request queue for the device
812 * @depth: the maximum queue depth supported
813 * @tags: the tag to use
815 int blk_queue_init_tags(request_queue_t
*q
, int depth
,
816 struct blk_queue_tag
*tags
)
820 BUG_ON(tags
&& q
->queue_tags
&& tags
!= q
->queue_tags
);
822 if (!tags
&& !q
->queue_tags
) {
823 tags
= kmalloc(sizeof(struct blk_queue_tag
), GFP_ATOMIC
);
827 if (init_tag_map(q
, tags
, depth
))
830 INIT_LIST_HEAD(&tags
->busy_list
);
832 atomic_set(&tags
->refcnt
, 1);
833 } else if (q
->queue_tags
) {
834 if ((rc
= blk_queue_resize_tags(q
, depth
)))
836 set_bit(QUEUE_FLAG_QUEUED
, &q
->queue_flags
);
839 atomic_inc(&tags
->refcnt
);
842 * assign it, all done
844 q
->queue_tags
= tags
;
845 q
->queue_flags
|= (1 << QUEUE_FLAG_QUEUED
);
852 EXPORT_SYMBOL(blk_queue_init_tags
);
855 * blk_queue_resize_tags - change the queueing depth
856 * @q: the request queue for the device
857 * @new_depth: the new max command queueing depth
860 * Must be called with the queue lock held.
862 int blk_queue_resize_tags(request_queue_t
*q
, int new_depth
)
864 struct blk_queue_tag
*bqt
= q
->queue_tags
;
865 struct request
**tag_index
;
866 unsigned long *tag_map
;
867 int max_depth
, nr_ulongs
;
873 * save the old state info, so we can copy it back
875 tag_index
= bqt
->tag_index
;
876 tag_map
= bqt
->tag_map
;
877 max_depth
= bqt
->max_depth
;
879 if (init_tag_map(q
, bqt
, new_depth
))
882 memcpy(bqt
->tag_index
, tag_index
, max_depth
* sizeof(struct request
*));
883 nr_ulongs
= ALIGN(max_depth
, BITS_PER_LONG
) / BITS_PER_LONG
;
884 memcpy(bqt
->tag_map
, tag_map
, nr_ulongs
* sizeof(unsigned long));
891 EXPORT_SYMBOL(blk_queue_resize_tags
);
894 * blk_queue_end_tag - end tag operations for a request
895 * @q: the request queue for the device
896 * @rq: the request that has completed
899 * Typically called when end_that_request_first() returns 0, meaning
900 * all transfers have been done for a request. It's important to call
901 * this function before end_that_request_last(), as that will put the
902 * request back on the free list thus corrupting the internal tag list.
905 * queue lock must be held.
907 void blk_queue_end_tag(request_queue_t
*q
, struct request
*rq
)
909 struct blk_queue_tag
*bqt
= q
->queue_tags
;
914 if (unlikely(tag
>= bqt
->max_depth
))
916 * This can happen after tag depth has been reduced.
917 * FIXME: how about a warning or info message here?
921 if (unlikely(!__test_and_clear_bit(tag
, bqt
->tag_map
))) {
922 printk(KERN_ERR
"%s: attempt to clear non-busy tag (%d)\n",
927 list_del_init(&rq
->queuelist
);
928 rq
->flags
&= ~REQ_QUEUED
;
931 if (unlikely(bqt
->tag_index
[tag
] == NULL
))
932 printk(KERN_ERR
"%s: tag %d is missing\n",
935 bqt
->tag_index
[tag
] = NULL
;
939 EXPORT_SYMBOL(blk_queue_end_tag
);
942 * blk_queue_start_tag - find a free tag and assign it
943 * @q: the request queue for the device
944 * @rq: the block request that needs tagging
947 * This can either be used as a stand-alone helper, or possibly be
948 * assigned as the queue &prep_rq_fn (in which case &struct request
949 * automagically gets a tag assigned). Note that this function
950 * assumes that any type of request can be queued! if this is not
951 * true for your device, you must check the request type before
952 * calling this function. The request will also be removed from
953 * the request queue, so it's the drivers responsibility to readd
954 * it if it should need to be restarted for some reason.
957 * queue lock must be held.
959 int blk_queue_start_tag(request_queue_t
*q
, struct request
*rq
)
961 struct blk_queue_tag
*bqt
= q
->queue_tags
;
964 if (unlikely((rq
->flags
& REQ_QUEUED
))) {
966 "%s: request %p for device [%s] already tagged %d",
968 rq
->rq_disk
? rq
->rq_disk
->disk_name
: "?", rq
->tag
);
972 tag
= find_first_zero_bit(bqt
->tag_map
, bqt
->max_depth
);
973 if (tag
>= bqt
->max_depth
)
976 __set_bit(tag
, bqt
->tag_map
);
978 rq
->flags
|= REQ_QUEUED
;
980 bqt
->tag_index
[tag
] = rq
;
981 blkdev_dequeue_request(rq
);
982 list_add(&rq
->queuelist
, &bqt
->busy_list
);
987 EXPORT_SYMBOL(blk_queue_start_tag
);
990 * blk_queue_invalidate_tags - invalidate all pending tags
991 * @q: the request queue for the device
994 * Hardware conditions may dictate a need to stop all pending requests.
995 * In this case, we will safely clear the block side of the tag queue and
996 * readd all requests to the request queue in the right order.
999 * queue lock must be held.
1001 void blk_queue_invalidate_tags(request_queue_t
*q
)
1003 struct blk_queue_tag
*bqt
= q
->queue_tags
;
1004 struct list_head
*tmp
, *n
;
1007 list_for_each_safe(tmp
, n
, &bqt
->busy_list
) {
1008 rq
= list_entry_rq(tmp
);
1010 if (rq
->tag
== -1) {
1012 "%s: bad tag found on list\n", __FUNCTION__
);
1013 list_del_init(&rq
->queuelist
);
1014 rq
->flags
&= ~REQ_QUEUED
;
1016 blk_queue_end_tag(q
, rq
);
1018 rq
->flags
&= ~REQ_STARTED
;
1019 __elv_add_request(q
, rq
, ELEVATOR_INSERT_BACK
, 0);
1023 EXPORT_SYMBOL(blk_queue_invalidate_tags
);
1025 static char *rq_flags
[] = {
1043 "REQ_DRIVE_TASKFILE",
1050 void blk_dump_rq_flags(struct request
*rq
, char *msg
)
1054 printk("%s: dev %s: flags = ", msg
,
1055 rq
->rq_disk
? rq
->rq_disk
->disk_name
: "?");
1058 if (rq
->flags
& (1 << bit
))
1059 printk("%s ", rq_flags
[bit
]);
1061 } while (bit
< __REQ_NR_BITS
);
1063 printk("\nsector %llu, nr/cnr %lu/%u\n", (unsigned long long)rq
->sector
,
1065 rq
->current_nr_sectors
);
1066 printk("bio %p, biotail %p, buffer %p, data %p, len %u\n", rq
->bio
, rq
->biotail
, rq
->buffer
, rq
->data
, rq
->data_len
);
1068 if (rq
->flags
& (REQ_BLOCK_PC
| REQ_PC
)) {
1070 for (bit
= 0; bit
< sizeof(rq
->cmd
); bit
++)
1071 printk("%02x ", rq
->cmd
[bit
]);
1076 EXPORT_SYMBOL(blk_dump_rq_flags
);
1078 void blk_recount_segments(request_queue_t
*q
, struct bio
*bio
)
1080 struct bio_vec
*bv
, *bvprv
= NULL
;
1081 int i
, nr_phys_segs
, nr_hw_segs
, seg_size
, hw_seg_size
, cluster
;
1082 int high
, highprv
= 1;
1084 if (unlikely(!bio
->bi_io_vec
))
1087 cluster
= q
->queue_flags
& (1 << QUEUE_FLAG_CLUSTER
);
1088 hw_seg_size
= seg_size
= nr_phys_segs
= nr_hw_segs
= 0;
1089 bio_for_each_segment(bv
, bio
, i
) {
1091 * the trick here is making sure that a high page is never
1092 * considered part of another segment, since that might
1093 * change with the bounce page.
1095 high
= page_to_pfn(bv
->bv_page
) >= q
->bounce_pfn
;
1096 if (high
|| highprv
)
1097 goto new_hw_segment
;
1099 if (seg_size
+ bv
->bv_len
> q
->max_segment_size
)
1101 if (!BIOVEC_PHYS_MERGEABLE(bvprv
, bv
))
1103 if (!BIOVEC_SEG_BOUNDARY(q
, bvprv
, bv
))
1105 if (BIOVEC_VIRT_OVERSIZE(hw_seg_size
+ bv
->bv_len
))
1106 goto new_hw_segment
;
1108 seg_size
+= bv
->bv_len
;
1109 hw_seg_size
+= bv
->bv_len
;
1114 if (BIOVEC_VIRT_MERGEABLE(bvprv
, bv
) &&
1115 !BIOVEC_VIRT_OVERSIZE(hw_seg_size
+ bv
->bv_len
)) {
1116 hw_seg_size
+= bv
->bv_len
;
1119 if (hw_seg_size
> bio
->bi_hw_front_size
)
1120 bio
->bi_hw_front_size
= hw_seg_size
;
1121 hw_seg_size
= BIOVEC_VIRT_START_SIZE(bv
) + bv
->bv_len
;
1127 seg_size
= bv
->bv_len
;
1130 if (hw_seg_size
> bio
->bi_hw_back_size
)
1131 bio
->bi_hw_back_size
= hw_seg_size
;
1132 if (nr_hw_segs
== 1 && hw_seg_size
> bio
->bi_hw_front_size
)
1133 bio
->bi_hw_front_size
= hw_seg_size
;
1134 bio
->bi_phys_segments
= nr_phys_segs
;
1135 bio
->bi_hw_segments
= nr_hw_segs
;
1136 bio
->bi_flags
|= (1 << BIO_SEG_VALID
);
1140 int blk_phys_contig_segment(request_queue_t
*q
, struct bio
*bio
,
1143 if (!(q
->queue_flags
& (1 << QUEUE_FLAG_CLUSTER
)))
1146 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio
), __BVEC_START(nxt
)))
1148 if (bio
->bi_size
+ nxt
->bi_size
> q
->max_segment_size
)
1152 * bio and nxt are contigous in memory, check if the queue allows
1153 * these two to be merged into one
1155 if (BIO_SEG_BOUNDARY(q
, bio
, nxt
))
1161 EXPORT_SYMBOL(blk_phys_contig_segment
);
1163 int blk_hw_contig_segment(request_queue_t
*q
, struct bio
*bio
,
1166 if (unlikely(!bio_flagged(bio
, BIO_SEG_VALID
)))
1167 blk_recount_segments(q
, bio
);
1168 if (unlikely(!bio_flagged(nxt
, BIO_SEG_VALID
)))
1169 blk_recount_segments(q
, nxt
);
1170 if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio
), __BVEC_START(nxt
)) ||
1171 BIOVEC_VIRT_OVERSIZE(bio
->bi_hw_front_size
+ bio
->bi_hw_back_size
))
1173 if (bio
->bi_size
+ nxt
->bi_size
> q
->max_segment_size
)
1179 EXPORT_SYMBOL(blk_hw_contig_segment
);
1182 * map a request to scatterlist, return number of sg entries setup. Caller
1183 * must make sure sg can hold rq->nr_phys_segments entries
1185 int blk_rq_map_sg(request_queue_t
*q
, struct request
*rq
, struct scatterlist
*sg
)
1187 struct bio_vec
*bvec
, *bvprv
;
1189 int nsegs
, i
, cluster
;
1192 cluster
= q
->queue_flags
& (1 << QUEUE_FLAG_CLUSTER
);
1195 * for each bio in rq
1198 rq_for_each_bio(bio
, rq
) {
1200 * for each segment in bio
1202 bio_for_each_segment(bvec
, bio
, i
) {
1203 int nbytes
= bvec
->bv_len
;
1205 if (bvprv
&& cluster
) {
1206 if (sg
[nsegs
- 1].length
+ nbytes
> q
->max_segment_size
)
1209 if (!BIOVEC_PHYS_MERGEABLE(bvprv
, bvec
))
1211 if (!BIOVEC_SEG_BOUNDARY(q
, bvprv
, bvec
))
1214 sg
[nsegs
- 1].length
+= nbytes
;
1217 memset(&sg
[nsegs
],0,sizeof(struct scatterlist
));
1218 sg
[nsegs
].page
= bvec
->bv_page
;
1219 sg
[nsegs
].length
= nbytes
;
1220 sg
[nsegs
].offset
= bvec
->bv_offset
;
1225 } /* segments in bio */
1231 EXPORT_SYMBOL(blk_rq_map_sg
);
1234 * the standard queue merge functions, can be overridden with device
1235 * specific ones if so desired
1238 static inline int ll_new_mergeable(request_queue_t
*q
,
1239 struct request
*req
,
1242 int nr_phys_segs
= bio_phys_segments(q
, bio
);
1244 if (req
->nr_phys_segments
+ nr_phys_segs
> q
->max_phys_segments
) {
1245 req
->flags
|= REQ_NOMERGE
;
1246 if (req
== q
->last_merge
)
1247 q
->last_merge
= NULL
;
1252 * A hw segment is just getting larger, bump just the phys
1255 req
->nr_phys_segments
+= nr_phys_segs
;
1259 static inline int ll_new_hw_segment(request_queue_t
*q
,
1260 struct request
*req
,
1263 int nr_hw_segs
= bio_hw_segments(q
, bio
);
1264 int nr_phys_segs
= bio_phys_segments(q
, bio
);
1266 if (req
->nr_hw_segments
+ nr_hw_segs
> q
->max_hw_segments
1267 || req
->nr_phys_segments
+ nr_phys_segs
> q
->max_phys_segments
) {
1268 req
->flags
|= REQ_NOMERGE
;
1269 if (req
== q
->last_merge
)
1270 q
->last_merge
= NULL
;
1275 * This will form the start of a new hw segment. Bump both
1278 req
->nr_hw_segments
+= nr_hw_segs
;
1279 req
->nr_phys_segments
+= nr_phys_segs
;
1283 static int ll_back_merge_fn(request_queue_t
*q
, struct request
*req
,
1288 if (req
->nr_sectors
+ bio_sectors(bio
) > q
->max_sectors
) {
1289 req
->flags
|= REQ_NOMERGE
;
1290 if (req
== q
->last_merge
)
1291 q
->last_merge
= NULL
;
1294 if (unlikely(!bio_flagged(req
->biotail
, BIO_SEG_VALID
)))
1295 blk_recount_segments(q
, req
->biotail
);
1296 if (unlikely(!bio_flagged(bio
, BIO_SEG_VALID
)))
1297 blk_recount_segments(q
, bio
);
1298 len
= req
->biotail
->bi_hw_back_size
+ bio
->bi_hw_front_size
;
1299 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req
->biotail
), __BVEC_START(bio
)) &&
1300 !BIOVEC_VIRT_OVERSIZE(len
)) {
1301 int mergeable
= ll_new_mergeable(q
, req
, bio
);
1304 if (req
->nr_hw_segments
== 1)
1305 req
->bio
->bi_hw_front_size
= len
;
1306 if (bio
->bi_hw_segments
== 1)
1307 bio
->bi_hw_back_size
= len
;
1312 return ll_new_hw_segment(q
, req
, bio
);
1315 static int ll_front_merge_fn(request_queue_t
*q
, struct request
*req
,
1320 if (req
->nr_sectors
+ bio_sectors(bio
) > q
->max_sectors
) {
1321 req
->flags
|= REQ_NOMERGE
;
1322 if (req
== q
->last_merge
)
1323 q
->last_merge
= NULL
;
1326 len
= bio
->bi_hw_back_size
+ req
->bio
->bi_hw_front_size
;
1327 if (unlikely(!bio_flagged(bio
, BIO_SEG_VALID
)))
1328 blk_recount_segments(q
, bio
);
1329 if (unlikely(!bio_flagged(req
->bio
, BIO_SEG_VALID
)))
1330 blk_recount_segments(q
, req
->bio
);
1331 if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio
), __BVEC_START(req
->bio
)) &&
1332 !BIOVEC_VIRT_OVERSIZE(len
)) {
1333 int mergeable
= ll_new_mergeable(q
, req
, bio
);
1336 if (bio
->bi_hw_segments
== 1)
1337 bio
->bi_hw_front_size
= len
;
1338 if (req
->nr_hw_segments
== 1)
1339 req
->biotail
->bi_hw_back_size
= len
;
1344 return ll_new_hw_segment(q
, req
, bio
);
1347 static int ll_merge_requests_fn(request_queue_t
*q
, struct request
*req
,
1348 struct request
*next
)
1350 int total_phys_segments
= req
->nr_phys_segments
+next
->nr_phys_segments
;
1351 int total_hw_segments
= req
->nr_hw_segments
+ next
->nr_hw_segments
;
1354 * First check if the either of the requests are re-queued
1355 * requests. Can't merge them if they are.
1357 if (req
->special
|| next
->special
)
1361 * Will it become to large?
1363 if ((req
->nr_sectors
+ next
->nr_sectors
) > q
->max_sectors
)
1366 total_phys_segments
= req
->nr_phys_segments
+ next
->nr_phys_segments
;
1367 if (blk_phys_contig_segment(q
, req
->biotail
, next
->bio
))
1368 total_phys_segments
--;
1370 if (total_phys_segments
> q
->max_phys_segments
)
1373 total_hw_segments
= req
->nr_hw_segments
+ next
->nr_hw_segments
;
1374 if (blk_hw_contig_segment(q
, req
->biotail
, next
->bio
)) {
1375 int len
= req
->biotail
->bi_hw_back_size
+ next
->bio
->bi_hw_front_size
;
1377 * propagate the combined length to the end of the requests
1379 if (req
->nr_hw_segments
== 1)
1380 req
->bio
->bi_hw_front_size
= len
;
1381 if (next
->nr_hw_segments
== 1)
1382 next
->biotail
->bi_hw_back_size
= len
;
1383 total_hw_segments
--;
1386 if (total_hw_segments
> q
->max_hw_segments
)
1389 /* Merge is OK... */
1390 req
->nr_phys_segments
= total_phys_segments
;
1391 req
->nr_hw_segments
= total_hw_segments
;
1396 * "plug" the device if there are no outstanding requests: this will
1397 * force the transfer to start only after we have put all the requests
1400 * This is called with interrupts off and no requests on the queue and
1401 * with the queue lock held.
1403 void blk_plug_device(request_queue_t
*q
)
1405 WARN_ON(!irqs_disabled());
1408 * don't plug a stopped queue, it must be paired with blk_start_queue()
1409 * which will restart the queueing
1411 if (test_bit(QUEUE_FLAG_STOPPED
, &q
->queue_flags
))
1414 if (!test_and_set_bit(QUEUE_FLAG_PLUGGED
, &q
->queue_flags
))
1415 mod_timer(&q
->unplug_timer
, jiffies
+ q
->unplug_delay
);
1418 EXPORT_SYMBOL(blk_plug_device
);
1421 * remove the queue from the plugged list, if present. called with
1422 * queue lock held and interrupts disabled.
1424 int blk_remove_plug(request_queue_t
*q
)
1426 WARN_ON(!irqs_disabled());
1428 if (!test_and_clear_bit(QUEUE_FLAG_PLUGGED
, &q
->queue_flags
))
1431 del_timer(&q
->unplug_timer
);
1435 EXPORT_SYMBOL(blk_remove_plug
);
1438 * remove the plug and let it rip..
1440 void __generic_unplug_device(request_queue_t
*q
)
1442 if (unlikely(test_bit(QUEUE_FLAG_STOPPED
, &q
->queue_flags
)))
1445 if (!blk_remove_plug(q
))
1449 * was plugged, fire request_fn if queue has stuff to do
1451 if (elv_next_request(q
))
1454 EXPORT_SYMBOL(__generic_unplug_device
);
1457 * generic_unplug_device - fire a request queue
1458 * @q: The &request_queue_t in question
1461 * Linux uses plugging to build bigger requests queues before letting
1462 * the device have at them. If a queue is plugged, the I/O scheduler
1463 * is still adding and merging requests on the queue. Once the queue
1464 * gets unplugged, the request_fn defined for the queue is invoked and
1465 * transfers started.
1467 void generic_unplug_device(request_queue_t
*q
)
1469 spin_lock_irq(q
->queue_lock
);
1470 __generic_unplug_device(q
);
1471 spin_unlock_irq(q
->queue_lock
);
1473 EXPORT_SYMBOL(generic_unplug_device
);
1475 static void blk_backing_dev_unplug(struct backing_dev_info
*bdi
,
1478 request_queue_t
*q
= bdi
->unplug_io_data
;
1481 * devices don't necessarily have an ->unplug_fn defined
1487 static void blk_unplug_work(void *data
)
1489 request_queue_t
*q
= data
;
1494 static void blk_unplug_timeout(unsigned long data
)
1496 request_queue_t
*q
= (request_queue_t
*)data
;
1498 kblockd_schedule_work(&q
->unplug_work
);
1502 * blk_start_queue - restart a previously stopped queue
1503 * @q: The &request_queue_t in question
1506 * blk_start_queue() will clear the stop flag on the queue, and call
1507 * the request_fn for the queue if it was in a stopped state when
1508 * entered. Also see blk_stop_queue(). Queue lock must be held.
1510 void blk_start_queue(request_queue_t
*q
)
1512 clear_bit(QUEUE_FLAG_STOPPED
, &q
->queue_flags
);
1515 * one level of recursion is ok and is much faster than kicking
1516 * the unplug handling
1518 if (!test_and_set_bit(QUEUE_FLAG_REENTER
, &q
->queue_flags
)) {
1520 clear_bit(QUEUE_FLAG_REENTER
, &q
->queue_flags
);
1523 kblockd_schedule_work(&q
->unplug_work
);
1527 EXPORT_SYMBOL(blk_start_queue
);
1530 * blk_stop_queue - stop a queue
1531 * @q: The &request_queue_t in question
1534 * The Linux block layer assumes that a block driver will consume all
1535 * entries on the request queue when the request_fn strategy is called.
1536 * Often this will not happen, because of hardware limitations (queue
1537 * depth settings). If a device driver gets a 'queue full' response,
1538 * or if it simply chooses not to queue more I/O at one point, it can
1539 * call this function to prevent the request_fn from being called until
1540 * the driver has signalled it's ready to go again. This happens by calling
1541 * blk_start_queue() to restart queue operations. Queue lock must be held.
1543 void blk_stop_queue(request_queue_t
*q
)
1546 set_bit(QUEUE_FLAG_STOPPED
, &q
->queue_flags
);
1548 EXPORT_SYMBOL(blk_stop_queue
);
1551 * blk_sync_queue - cancel any pending callbacks on a queue
1555 * The block layer may perform asynchronous callback activity
1556 * on a queue, such as calling the unplug function after a timeout.
1557 * A block device may call blk_sync_queue to ensure that any
1558 * such activity is cancelled, thus allowing it to release resources
1559 * the the callbacks might use. The caller must already have made sure
1560 * that its ->make_request_fn will not re-add plugging prior to calling
1564 void blk_sync_queue(struct request_queue
*q
)
1566 del_timer_sync(&q
->unplug_timer
);
1569 EXPORT_SYMBOL(blk_sync_queue
);
1572 * blk_run_queue - run a single device queue
1573 * @q: The queue to run
1575 void blk_run_queue(struct request_queue
*q
)
1577 unsigned long flags
;
1579 spin_lock_irqsave(q
->queue_lock
, flags
);
1581 if (!elv_queue_empty(q
))
1583 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1585 EXPORT_SYMBOL(blk_run_queue
);
1588 * blk_cleanup_queue: - release a &request_queue_t when it is no longer needed
1589 * @q: the request queue to be released
1592 * blk_cleanup_queue is the pair to blk_init_queue() or
1593 * blk_queue_make_request(). It should be called when a request queue is
1594 * being released; typically when a block device is being de-registered.
1595 * Currently, its primary task it to free all the &struct request
1596 * structures that were allocated to the queue and the queue itself.
1599 * Hopefully the low level driver will have finished any
1600 * outstanding requests first...
1602 void blk_cleanup_queue(request_queue_t
* q
)
1604 struct request_list
*rl
= &q
->rq
;
1606 if (!atomic_dec_and_test(&q
->refcnt
))
1610 elevator_exit(q
->elevator
);
1615 mempool_destroy(rl
->rq_pool
);
1618 __blk_queue_free_tags(q
);
1620 blk_queue_ordered(q
, QUEUE_ORDERED_NONE
);
1622 kmem_cache_free(requestq_cachep
, q
);
1625 EXPORT_SYMBOL(blk_cleanup_queue
);
1627 static int blk_init_free_list(request_queue_t
*q
)
1629 struct request_list
*rl
= &q
->rq
;
1631 rl
->count
[READ
] = rl
->count
[WRITE
] = 0;
1632 rl
->starved
[READ
] = rl
->starved
[WRITE
] = 0;
1633 init_waitqueue_head(&rl
->wait
[READ
]);
1634 init_waitqueue_head(&rl
->wait
[WRITE
]);
1635 init_waitqueue_head(&rl
->drain
);
1637 rl
->rq_pool
= mempool_create_node(BLKDEV_MIN_RQ
, mempool_alloc_slab
,
1638 mempool_free_slab
, request_cachep
, q
->node
);
1646 static int __make_request(request_queue_t
*, struct bio
*);
1648 request_queue_t
*blk_alloc_queue(int gfp_mask
)
1650 return blk_alloc_queue_node(gfp_mask
, -1);
1652 EXPORT_SYMBOL(blk_alloc_queue
);
1654 request_queue_t
*blk_alloc_queue_node(int gfp_mask
, int node_id
)
1658 q
= kmem_cache_alloc_node(requestq_cachep
, gfp_mask
, node_id
);
1662 memset(q
, 0, sizeof(*q
));
1663 init_timer(&q
->unplug_timer
);
1664 atomic_set(&q
->refcnt
, 1);
1666 q
->backing_dev_info
.unplug_io_fn
= blk_backing_dev_unplug
;
1667 q
->backing_dev_info
.unplug_io_data
= q
;
1671 EXPORT_SYMBOL(blk_alloc_queue_node
);
1674 * blk_init_queue - prepare a request queue for use with a block device
1675 * @rfn: The function to be called to process requests that have been
1676 * placed on the queue.
1677 * @lock: Request queue spin lock
1680 * If a block device wishes to use the standard request handling procedures,
1681 * which sorts requests and coalesces adjacent requests, then it must
1682 * call blk_init_queue(). The function @rfn will be called when there
1683 * are requests on the queue that need to be processed. If the device
1684 * supports plugging, then @rfn may not be called immediately when requests
1685 * are available on the queue, but may be called at some time later instead.
1686 * Plugged queues are generally unplugged when a buffer belonging to one
1687 * of the requests on the queue is needed, or due to memory pressure.
1689 * @rfn is not required, or even expected, to remove all requests off the
1690 * queue, but only as many as it can handle at a time. If it does leave
1691 * requests on the queue, it is responsible for arranging that the requests
1692 * get dealt with eventually.
1694 * The queue spin lock must be held while manipulating the requests on the
1697 * Function returns a pointer to the initialized request queue, or NULL if
1698 * it didn't succeed.
1701 * blk_init_queue() must be paired with a blk_cleanup_queue() call
1702 * when the block device is deactivated (such as at module unload).
1705 request_queue_t
*blk_init_queue(request_fn_proc
*rfn
, spinlock_t
*lock
)
1707 return blk_init_queue_node(rfn
, lock
, -1);
1709 EXPORT_SYMBOL(blk_init_queue
);
1712 blk_init_queue_node(request_fn_proc
*rfn
, spinlock_t
*lock
, int node_id
)
1714 request_queue_t
*q
= blk_alloc_queue_node(GFP_KERNEL
, node_id
);
1720 if (blk_init_free_list(q
))
1724 * if caller didn't supply a lock, they get per-queue locking with
1728 spin_lock_init(&q
->__queue_lock
);
1729 lock
= &q
->__queue_lock
;
1732 q
->request_fn
= rfn
;
1733 q
->back_merge_fn
= ll_back_merge_fn
;
1734 q
->front_merge_fn
= ll_front_merge_fn
;
1735 q
->merge_requests_fn
= ll_merge_requests_fn
;
1736 q
->prep_rq_fn
= NULL
;
1737 q
->unplug_fn
= generic_unplug_device
;
1738 q
->queue_flags
= (1 << QUEUE_FLAG_CLUSTER
);
1739 q
->queue_lock
= lock
;
1741 blk_queue_segment_boundary(q
, 0xffffffff);
1743 blk_queue_make_request(q
, __make_request
);
1744 blk_queue_max_segment_size(q
, MAX_SEGMENT_SIZE
);
1746 blk_queue_max_hw_segments(q
, MAX_HW_SEGMENTS
);
1747 blk_queue_max_phys_segments(q
, MAX_PHYS_SEGMENTS
);
1752 if (!elevator_init(q
, NULL
)) {
1753 blk_queue_congestion_threshold(q
);
1757 blk_cleanup_queue(q
);
1759 kmem_cache_free(requestq_cachep
, q
);
1762 EXPORT_SYMBOL(blk_init_queue_node
);
1764 int blk_get_queue(request_queue_t
*q
)
1766 if (likely(!test_bit(QUEUE_FLAG_DEAD
, &q
->queue_flags
))) {
1767 atomic_inc(&q
->refcnt
);
1774 EXPORT_SYMBOL(blk_get_queue
);
1776 static inline void blk_free_request(request_queue_t
*q
, struct request
*rq
)
1778 elv_put_request(q
, rq
);
1779 mempool_free(rq
, q
->rq
.rq_pool
);
1782 static inline struct request
*blk_alloc_request(request_queue_t
*q
, int rw
,
1785 struct request
*rq
= mempool_alloc(q
->rq
.rq_pool
, gfp_mask
);
1791 * first three bits are identical in rq->flags and bio->bi_rw,
1792 * see bio.h and blkdev.h
1796 if (!elv_set_request(q
, rq
, gfp_mask
))
1799 mempool_free(rq
, q
->rq
.rq_pool
);
1804 * ioc_batching returns true if the ioc is a valid batching request and
1805 * should be given priority access to a request.
1807 static inline int ioc_batching(request_queue_t
*q
, struct io_context
*ioc
)
1813 * Make sure the process is able to allocate at least 1 request
1814 * even if the batch times out, otherwise we could theoretically
1817 return ioc
->nr_batch_requests
== q
->nr_batching
||
1818 (ioc
->nr_batch_requests
> 0
1819 && time_before(jiffies
, ioc
->last_waited
+ BLK_BATCH_TIME
));
1823 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
1824 * will cause the process to be a "batcher" on all queues in the system. This
1825 * is the behaviour we want though - once it gets a wakeup it should be given
1828 void ioc_set_batching(request_queue_t
*q
, struct io_context
*ioc
)
1830 if (!ioc
|| ioc_batching(q
, ioc
))
1833 ioc
->nr_batch_requests
= q
->nr_batching
;
1834 ioc
->last_waited
= jiffies
;
1837 static void __freed_request(request_queue_t
*q
, int rw
)
1839 struct request_list
*rl
= &q
->rq
;
1841 if (rl
->count
[rw
] < queue_congestion_off_threshold(q
))
1842 clear_queue_congested(q
, rw
);
1844 if (rl
->count
[rw
] + 1 <= q
->nr_requests
) {
1845 if (waitqueue_active(&rl
->wait
[rw
]))
1846 wake_up(&rl
->wait
[rw
]);
1848 blk_clear_queue_full(q
, rw
);
1853 * A request has just been released. Account for it, update the full and
1854 * congestion status, wake up any waiters. Called under q->queue_lock.
1856 static void freed_request(request_queue_t
*q
, int rw
)
1858 struct request_list
*rl
= &q
->rq
;
1862 __freed_request(q
, rw
);
1864 if (unlikely(rl
->starved
[rw
^ 1]))
1865 __freed_request(q
, rw
^ 1);
1867 if (!rl
->count
[READ
] && !rl
->count
[WRITE
]) {
1869 if (unlikely(waitqueue_active(&rl
->drain
)))
1870 wake_up(&rl
->drain
);
1874 #define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist)
1876 * Get a free request, queue_lock must not be held
1878 static struct request
*get_request(request_queue_t
*q
, int rw
, int gfp_mask
)
1880 struct request
*rq
= NULL
;
1881 struct request_list
*rl
= &q
->rq
;
1882 struct io_context
*ioc
= get_io_context(gfp_mask
);
1884 if (unlikely(test_bit(QUEUE_FLAG_DRAIN
, &q
->queue_flags
)))
1887 spin_lock_irq(q
->queue_lock
);
1888 if (rl
->count
[rw
]+1 >= q
->nr_requests
) {
1890 * The queue will fill after this allocation, so set it as
1891 * full, and mark this process as "batching". This process
1892 * will be allowed to complete a batch of requests, others
1895 if (!blk_queue_full(q
, rw
)) {
1896 ioc_set_batching(q
, ioc
);
1897 blk_set_queue_full(q
, rw
);
1901 switch (elv_may_queue(q
, rw
)) {
1904 case ELV_MQUEUE_MAY
:
1906 case ELV_MQUEUE_MUST
:
1910 if (blk_queue_full(q
, rw
) && !ioc_batching(q
, ioc
)) {
1912 * The queue is full and the allocating process is not a
1913 * "batcher", and not exempted by the IO scheduler
1915 spin_unlock_irq(q
->queue_lock
);
1921 rl
->starved
[rw
] = 0;
1922 if (rl
->count
[rw
] >= queue_congestion_on_threshold(q
))
1923 set_queue_congested(q
, rw
);
1924 spin_unlock_irq(q
->queue_lock
);
1926 rq
= blk_alloc_request(q
, rw
, gfp_mask
);
1929 * Allocation failed presumably due to memory. Undo anything
1930 * we might have messed up.
1932 * Allocating task should really be put onto the front of the
1933 * wait queue, but this is pretty rare.
1935 spin_lock_irq(q
->queue_lock
);
1936 freed_request(q
, rw
);
1939 * in the very unlikely event that allocation failed and no
1940 * requests for this direction was pending, mark us starved
1941 * so that freeing of a request in the other direction will
1942 * notice us. another possible fix would be to split the
1943 * rq mempool into READ and WRITE
1946 if (unlikely(rl
->count
[rw
] == 0))
1947 rl
->starved
[rw
] = 1;
1949 spin_unlock_irq(q
->queue_lock
);
1953 if (ioc_batching(q
, ioc
))
1954 ioc
->nr_batch_requests
--;
1959 put_io_context(ioc
);
1964 * No available requests for this queue, unplug the device and wait for some
1965 * requests to become available.
1967 static struct request
*get_request_wait(request_queue_t
*q
, int rw
)
1972 generic_unplug_device(q
);
1974 struct request_list
*rl
= &q
->rq
;
1976 prepare_to_wait_exclusive(&rl
->wait
[rw
], &wait
,
1977 TASK_UNINTERRUPTIBLE
);
1979 rq
= get_request(q
, rw
, GFP_NOIO
);
1982 struct io_context
*ioc
;
1987 * After sleeping, we become a "batching" process and
1988 * will be able to allocate at least one request, and
1989 * up to a big batch of them for a small period time.
1990 * See ioc_batching, ioc_set_batching
1992 ioc
= get_io_context(GFP_NOIO
);
1993 ioc_set_batching(q
, ioc
);
1994 put_io_context(ioc
);
1996 finish_wait(&rl
->wait
[rw
], &wait
);
2002 struct request
*blk_get_request(request_queue_t
*q
, int rw
, int gfp_mask
)
2006 BUG_ON(rw
!= READ
&& rw
!= WRITE
);
2008 if (gfp_mask
& __GFP_WAIT
)
2009 rq
= get_request_wait(q
, rw
);
2011 rq
= get_request(q
, rw
, gfp_mask
);
2016 EXPORT_SYMBOL(blk_get_request
);
2019 * blk_requeue_request - put a request back on queue
2020 * @q: request queue where request should be inserted
2021 * @rq: request to be inserted
2024 * Drivers often keep queueing requests until the hardware cannot accept
2025 * more, when that condition happens we need to put the request back
2026 * on the queue. Must be called with queue lock held.
2028 void blk_requeue_request(request_queue_t
*q
, struct request
*rq
)
2030 if (blk_rq_tagged(rq
))
2031 blk_queue_end_tag(q
, rq
);
2033 elv_requeue_request(q
, rq
);
2036 EXPORT_SYMBOL(blk_requeue_request
);
2039 * blk_insert_request - insert a special request in to a request queue
2040 * @q: request queue where request should be inserted
2041 * @rq: request to be inserted
2042 * @at_head: insert request at head or tail of queue
2043 * @data: private data
2046 * Many block devices need to execute commands asynchronously, so they don't
2047 * block the whole kernel from preemption during request execution. This is
2048 * accomplished normally by inserting aritficial requests tagged as
2049 * REQ_SPECIAL in to the corresponding request queue, and letting them be
2050 * scheduled for actual execution by the request queue.
2052 * We have the option of inserting the head or the tail of the queue.
2053 * Typically we use the tail for new ioctls and so forth. We use the head
2054 * of the queue for things like a QUEUE_FULL message from a device, or a
2055 * host that is unable to accept a particular command.
2057 void blk_insert_request(request_queue_t
*q
, struct request
*rq
,
2058 int at_head
, void *data
)
2060 int where
= at_head
? ELEVATOR_INSERT_FRONT
: ELEVATOR_INSERT_BACK
;
2061 unsigned long flags
;
2064 * tell I/O scheduler that this isn't a regular read/write (ie it
2065 * must not attempt merges on this) and that it acts as a soft
2068 rq
->flags
|= REQ_SPECIAL
| REQ_SOFTBARRIER
;
2072 spin_lock_irqsave(q
->queue_lock
, flags
);
2075 * If command is tagged, release the tag
2077 if (blk_rq_tagged(rq
))
2078 blk_queue_end_tag(q
, rq
);
2080 drive_stat_acct(rq
, rq
->nr_sectors
, 1);
2081 __elv_add_request(q
, rq
, where
, 0);
2083 if (blk_queue_plugged(q
))
2084 __generic_unplug_device(q
);
2087 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2090 EXPORT_SYMBOL(blk_insert_request
);
2093 * blk_rq_map_user - map user data to a request, for REQ_BLOCK_PC usage
2094 * @q: request queue where request should be inserted
2095 * @rw: READ or WRITE data
2096 * @ubuf: the user buffer
2097 * @len: length of user data
2100 * Data will be mapped directly for zero copy io, if possible. Otherwise
2101 * a kernel bounce buffer is used.
2103 * A matching blk_rq_unmap_user() must be issued at the end of io, while
2104 * still in process context.
2106 * Note: The mapped bio may need to be bounced through blk_queue_bounce()
2107 * before being submitted to the device, as pages mapped may be out of
2108 * reach. It's the callers responsibility to make sure this happens. The
2109 * original bio must be passed back in to blk_rq_unmap_user() for proper
2112 struct request
*blk_rq_map_user(request_queue_t
*q
, int rw
, void __user
*ubuf
,
2115 unsigned long uaddr
;
2119 if (len
> (q
->max_sectors
<< 9))
2120 return ERR_PTR(-EINVAL
);
2121 if ((!len
&& ubuf
) || (len
&& !ubuf
))
2122 return ERR_PTR(-EINVAL
);
2124 rq
= blk_get_request(q
, rw
, __GFP_WAIT
);
2126 return ERR_PTR(-ENOMEM
);
2129 * if alignment requirement is satisfied, map in user pages for
2130 * direct dma. else, set up kernel bounce buffers
2132 uaddr
= (unsigned long) ubuf
;
2133 if (!(uaddr
& queue_dma_alignment(q
)) && !(len
& queue_dma_alignment(q
)))
2134 bio
= bio_map_user(q
, NULL
, uaddr
, len
, rw
== READ
);
2136 bio
= bio_copy_user(q
, uaddr
, len
, rw
== READ
);
2139 rq
->bio
= rq
->biotail
= bio
;
2140 blk_rq_bio_prep(q
, rq
, bio
);
2142 rq
->buffer
= rq
->data
= NULL
;
2148 * bio is the err-ptr
2150 blk_put_request(rq
);
2151 return (struct request
*) bio
;
2154 EXPORT_SYMBOL(blk_rq_map_user
);
2157 * blk_rq_unmap_user - unmap a request with user data
2158 * @rq: request to be unmapped
2159 * @bio: bio for the request
2160 * @ulen: length of user buffer
2163 * Unmap a request previously mapped by blk_rq_map_user().
2165 int blk_rq_unmap_user(struct request
*rq
, struct bio
*bio
, unsigned int ulen
)
2170 if (bio_flagged(bio
, BIO_USER_MAPPED
))
2171 bio_unmap_user(bio
);
2173 ret
= bio_uncopy_user(bio
);
2176 blk_put_request(rq
);
2180 EXPORT_SYMBOL(blk_rq_unmap_user
);
2183 * blk_execute_rq - insert a request into queue for execution
2184 * @q: queue to insert the request in
2185 * @bd_disk: matching gendisk
2186 * @rq: request to insert
2189 * Insert a fully prepared request at the back of the io scheduler queue
2192 int blk_execute_rq(request_queue_t
*q
, struct gendisk
*bd_disk
,
2195 DECLARE_COMPLETION(wait
);
2196 char sense
[SCSI_SENSE_BUFFERSIZE
];
2199 rq
->rq_disk
= bd_disk
;
2202 * we need an extra reference to the request, so we can look at
2203 * it after io completion
2208 memset(sense
, 0, sizeof(sense
));
2213 rq
->flags
|= REQ_NOMERGE
;
2214 rq
->waiting
= &wait
;
2215 rq
->end_io
= blk_end_sync_rq
;
2216 elv_add_request(q
, rq
, ELEVATOR_INSERT_BACK
, 1);
2217 generic_unplug_device(q
);
2218 wait_for_completion(&wait
);
2227 EXPORT_SYMBOL(blk_execute_rq
);
2230 * blkdev_issue_flush - queue a flush
2231 * @bdev: blockdev to issue flush for
2232 * @error_sector: error sector
2235 * Issue a flush for the block device in question. Caller can supply
2236 * room for storing the error offset in case of a flush error, if they
2237 * wish to. Caller must run wait_for_completion() on its own.
2239 int blkdev_issue_flush(struct block_device
*bdev
, sector_t
*error_sector
)
2243 if (bdev
->bd_disk
== NULL
)
2246 q
= bdev_get_queue(bdev
);
2249 if (!q
->issue_flush_fn
)
2252 return q
->issue_flush_fn(q
, bdev
->bd_disk
, error_sector
);
2255 EXPORT_SYMBOL(blkdev_issue_flush
);
2258 * blkdev_scsi_issue_flush_fn - issue flush for SCSI devices
2261 * @error_sector: error offset
2264 * Devices understanding the SCSI command set, can use this function as
2265 * a helper for issuing a cache flush. Note: driver is required to store
2266 * the error offset (in case of error flushing) in ->sector of struct
2269 int blkdev_scsi_issue_flush_fn(request_queue_t
*q
, struct gendisk
*disk
,
2270 sector_t
*error_sector
)
2272 struct request
*rq
= blk_get_request(q
, WRITE
, __GFP_WAIT
);
2275 rq
->flags
|= REQ_BLOCK_PC
| REQ_SOFTBARRIER
;
2277 memset(rq
->cmd
, 0, sizeof(rq
->cmd
));
2282 rq
->timeout
= 60 * HZ
;
2284 ret
= blk_execute_rq(q
, disk
, rq
);
2286 if (ret
&& error_sector
)
2287 *error_sector
= rq
->sector
;
2289 blk_put_request(rq
);
2293 EXPORT_SYMBOL(blkdev_scsi_issue_flush_fn
);
2295 void drive_stat_acct(struct request
*rq
, int nr_sectors
, int new_io
)
2297 int rw
= rq_data_dir(rq
);
2299 if (!blk_fs_request(rq
) || !rq
->rq_disk
)
2303 __disk_stat_add(rq
->rq_disk
, read_sectors
, nr_sectors
);
2305 __disk_stat_inc(rq
->rq_disk
, read_merges
);
2306 } else if (rw
== WRITE
) {
2307 __disk_stat_add(rq
->rq_disk
, write_sectors
, nr_sectors
);
2309 __disk_stat_inc(rq
->rq_disk
, write_merges
);
2312 disk_round_stats(rq
->rq_disk
);
2313 rq
->rq_disk
->in_flight
++;
2318 * add-request adds a request to the linked list.
2319 * queue lock is held and interrupts disabled, as we muck with the
2320 * request queue list.
2322 static inline void add_request(request_queue_t
* q
, struct request
* req
)
2324 drive_stat_acct(req
, req
->nr_sectors
, 1);
2327 q
->activity_fn(q
->activity_data
, rq_data_dir(req
));
2330 * elevator indicated where it wants this request to be
2331 * inserted at elevator_merge time
2333 __elv_add_request(q
, req
, ELEVATOR_INSERT_SORT
, 0);
2337 * disk_round_stats() - Round off the performance stats on a struct
2340 * The average IO queue length and utilisation statistics are maintained
2341 * by observing the current state of the queue length and the amount of
2342 * time it has been in this state for.
2344 * Normally, that accounting is done on IO completion, but that can result
2345 * in more than a second's worth of IO being accounted for within any one
2346 * second, leading to >100% utilisation. To deal with that, we call this
2347 * function to do a round-off before returning the results when reading
2348 * /proc/diskstats. This accounts immediately for all queue usage up to
2349 * the current jiffies and restarts the counters again.
2351 void disk_round_stats(struct gendisk
*disk
)
2353 unsigned long now
= jiffies
;
2355 __disk_stat_add(disk
, time_in_queue
,
2356 disk
->in_flight
* (now
- disk
->stamp
));
2359 if (disk
->in_flight
)
2360 __disk_stat_add(disk
, io_ticks
, (now
- disk
->stamp_idle
));
2361 disk
->stamp_idle
= now
;
2365 * queue lock must be held
2367 static void __blk_put_request(request_queue_t
*q
, struct request
*req
)
2369 struct request_list
*rl
= req
->rl
;
2373 if (unlikely(--req
->ref_count
))
2376 req
->rq_status
= RQ_INACTIVE
;
2381 * Request may not have originated from ll_rw_blk. if not,
2382 * it didn't come out of our reserved rq pools
2385 int rw
= rq_data_dir(req
);
2387 elv_completed_request(q
, req
);
2389 BUG_ON(!list_empty(&req
->queuelist
));
2391 blk_free_request(q
, req
);
2392 freed_request(q
, rw
);
2396 void blk_put_request(struct request
*req
)
2399 * if req->rl isn't set, this request didnt originate from the
2400 * block layer, so it's safe to just disregard it
2403 unsigned long flags
;
2404 request_queue_t
*q
= req
->q
;
2406 spin_lock_irqsave(q
->queue_lock
, flags
);
2407 __blk_put_request(q
, req
);
2408 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2412 EXPORT_SYMBOL(blk_put_request
);
2415 * blk_end_sync_rq - executes a completion event on a request
2416 * @rq: request to complete
2418 void blk_end_sync_rq(struct request
*rq
)
2420 struct completion
*waiting
= rq
->waiting
;
2423 __blk_put_request(rq
->q
, rq
);
2426 * complete last, if this is a stack request the process (and thus
2427 * the rq pointer) could be invalid right after this complete()
2431 EXPORT_SYMBOL(blk_end_sync_rq
);
2434 * blk_congestion_wait - wait for a queue to become uncongested
2435 * @rw: READ or WRITE
2436 * @timeout: timeout in jiffies
2438 * Waits for up to @timeout jiffies for a queue (any queue) to exit congestion.
2439 * If no queues are congested then just wait for the next request to be
2442 long blk_congestion_wait(int rw
, long timeout
)
2446 wait_queue_head_t
*wqh
= &congestion_wqh
[rw
];
2448 prepare_to_wait(wqh
, &wait
, TASK_UNINTERRUPTIBLE
);
2449 ret
= io_schedule_timeout(timeout
);
2450 finish_wait(wqh
, &wait
);
2454 EXPORT_SYMBOL(blk_congestion_wait
);
2457 * Has to be called with the request spinlock acquired
2459 static int attempt_merge(request_queue_t
*q
, struct request
*req
,
2460 struct request
*next
)
2462 if (!rq_mergeable(req
) || !rq_mergeable(next
))
2468 if (req
->sector
+ req
->nr_sectors
!= next
->sector
)
2471 if (rq_data_dir(req
) != rq_data_dir(next
)
2472 || req
->rq_disk
!= next
->rq_disk
2473 || next
->waiting
|| next
->special
)
2477 * If we are allowed to merge, then append bio list
2478 * from next to rq and release next. merge_requests_fn
2479 * will have updated segment counts, update sector
2482 if (!q
->merge_requests_fn(q
, req
, next
))
2486 * At this point we have either done a back merge
2487 * or front merge. We need the smaller start_time of
2488 * the merged requests to be the current request
2489 * for accounting purposes.
2491 if (time_after(req
->start_time
, next
->start_time
))
2492 req
->start_time
= next
->start_time
;
2494 req
->biotail
->bi_next
= next
->bio
;
2495 req
->biotail
= next
->biotail
;
2497 req
->nr_sectors
= req
->hard_nr_sectors
+= next
->hard_nr_sectors
;
2499 elv_merge_requests(q
, req
, next
);
2502 disk_round_stats(req
->rq_disk
);
2503 req
->rq_disk
->in_flight
--;
2506 __blk_put_request(q
, next
);
2510 static inline int attempt_back_merge(request_queue_t
*q
, struct request
*rq
)
2512 struct request
*next
= elv_latter_request(q
, rq
);
2515 return attempt_merge(q
, rq
, next
);
2520 static inline int attempt_front_merge(request_queue_t
*q
, struct request
*rq
)
2522 struct request
*prev
= elv_former_request(q
, rq
);
2525 return attempt_merge(q
, prev
, rq
);
2531 * blk_attempt_remerge - attempt to remerge active head with next request
2532 * @q: The &request_queue_t belonging to the device
2533 * @rq: The head request (usually)
2536 * For head-active devices, the queue can easily be unplugged so quickly
2537 * that proper merging is not done on the front request. This may hurt
2538 * performance greatly for some devices. The block layer cannot safely
2539 * do merging on that first request for these queues, but the driver can
2540 * call this function and make it happen any way. Only the driver knows
2541 * when it is safe to do so.
2543 void blk_attempt_remerge(request_queue_t
*q
, struct request
*rq
)
2545 unsigned long flags
;
2547 spin_lock_irqsave(q
->queue_lock
, flags
);
2548 attempt_back_merge(q
, rq
);
2549 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2552 EXPORT_SYMBOL(blk_attempt_remerge
);
2555 * Non-locking blk_attempt_remerge variant.
2557 void __blk_attempt_remerge(request_queue_t
*q
, struct request
*rq
)
2559 attempt_back_merge(q
, rq
);
2562 EXPORT_SYMBOL(__blk_attempt_remerge
);
2564 static int __make_request(request_queue_t
*q
, struct bio
*bio
)
2566 struct request
*req
, *freereq
= NULL
;
2567 int el_ret
, rw
, nr_sectors
, cur_nr_sectors
, barrier
, err
, sync
;
2570 sector
= bio
->bi_sector
;
2571 nr_sectors
= bio_sectors(bio
);
2572 cur_nr_sectors
= bio_cur_sectors(bio
);
2574 rw
= bio_data_dir(bio
);
2575 sync
= bio_sync(bio
);
2578 * low level driver can indicate that it wants pages above a
2579 * certain limit bounced to low memory (ie for highmem, or even
2580 * ISA dma in theory)
2582 blk_queue_bounce(q
, &bio
);
2584 spin_lock_prefetch(q
->queue_lock
);
2586 barrier
= bio_barrier(bio
);
2587 if (unlikely(barrier
) && (q
->ordered
== QUEUE_ORDERED_NONE
)) {
2593 spin_lock_irq(q
->queue_lock
);
2595 if (elv_queue_empty(q
)) {
2602 el_ret
= elv_merge(q
, &req
, bio
);
2604 case ELEVATOR_BACK_MERGE
:
2605 BUG_ON(!rq_mergeable(req
));
2607 if (!q
->back_merge_fn(q
, req
, bio
))
2610 req
->biotail
->bi_next
= bio
;
2612 req
->nr_sectors
= req
->hard_nr_sectors
+= nr_sectors
;
2613 drive_stat_acct(req
, nr_sectors
, 0);
2614 if (!attempt_back_merge(q
, req
))
2615 elv_merged_request(q
, req
);
2618 case ELEVATOR_FRONT_MERGE
:
2619 BUG_ON(!rq_mergeable(req
));
2621 if (!q
->front_merge_fn(q
, req
, bio
))
2624 bio
->bi_next
= req
->bio
;
2628 * may not be valid. if the low level driver said
2629 * it didn't need a bounce buffer then it better
2630 * not touch req->buffer either...
2632 req
->buffer
= bio_data(bio
);
2633 req
->current_nr_sectors
= cur_nr_sectors
;
2634 req
->hard_cur_sectors
= cur_nr_sectors
;
2635 req
->sector
= req
->hard_sector
= sector
;
2636 req
->nr_sectors
= req
->hard_nr_sectors
+= nr_sectors
;
2637 drive_stat_acct(req
, nr_sectors
, 0);
2638 if (!attempt_front_merge(q
, req
))
2639 elv_merged_request(q
, req
);
2643 * elevator says don't/can't merge. get new request
2645 case ELEVATOR_NO_MERGE
:
2649 printk("elevator returned crap (%d)\n", el_ret
);
2654 * Grab a free request from the freelist - if that is empty, check
2655 * if we are doing read ahead and abort instead of blocking for
2663 spin_unlock_irq(q
->queue_lock
);
2664 if ((freereq
= get_request(q
, rw
, GFP_ATOMIC
)) == NULL
) {
2669 if (bio_rw_ahead(bio
))
2672 freereq
= get_request_wait(q
, rw
);
2677 req
->flags
|= REQ_CMD
;
2680 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST)
2682 if (bio_rw_ahead(bio
) || bio_failfast(bio
))
2683 req
->flags
|= REQ_FAILFAST
;
2686 * REQ_BARRIER implies no merging, but lets make it explicit
2688 if (unlikely(barrier
))
2689 req
->flags
|= (REQ_HARDBARRIER
| REQ_NOMERGE
);
2692 req
->hard_sector
= req
->sector
= sector
;
2693 req
->hard_nr_sectors
= req
->nr_sectors
= nr_sectors
;
2694 req
->current_nr_sectors
= req
->hard_cur_sectors
= cur_nr_sectors
;
2695 req
->nr_phys_segments
= bio_phys_segments(q
, bio
);
2696 req
->nr_hw_segments
= bio_hw_segments(q
, bio
);
2697 req
->buffer
= bio_data(bio
); /* see ->buffer comment above */
2698 req
->waiting
= NULL
;
2699 req
->bio
= req
->biotail
= bio
;
2700 req
->rq_disk
= bio
->bi_bdev
->bd_disk
;
2701 req
->start_time
= jiffies
;
2703 add_request(q
, req
);
2706 __blk_put_request(q
, freereq
);
2708 __generic_unplug_device(q
);
2710 spin_unlock_irq(q
->queue_lock
);
2714 bio_endio(bio
, nr_sectors
<< 9, err
);
2719 * If bio->bi_dev is a partition, remap the location
2721 static inline void blk_partition_remap(struct bio
*bio
)
2723 struct block_device
*bdev
= bio
->bi_bdev
;
2725 if (bdev
!= bdev
->bd_contains
) {
2726 struct hd_struct
*p
= bdev
->bd_part
;
2728 switch (bio
->bi_rw
) {
2730 p
->read_sectors
+= bio_sectors(bio
);
2734 p
->write_sectors
+= bio_sectors(bio
);
2738 bio
->bi_sector
+= p
->start_sect
;
2739 bio
->bi_bdev
= bdev
->bd_contains
;
2743 void blk_finish_queue_drain(request_queue_t
*q
)
2745 struct request_list
*rl
= &q
->rq
;
2748 spin_lock_irq(q
->queue_lock
);
2749 clear_bit(QUEUE_FLAG_DRAIN
, &q
->queue_flags
);
2751 while (!list_empty(&q
->drain_list
)) {
2752 rq
= list_entry_rq(q
->drain_list
.next
);
2754 list_del_init(&rq
->queuelist
);
2755 __elv_add_request(q
, rq
, ELEVATOR_INSERT_BACK
, 1);
2758 spin_unlock_irq(q
->queue_lock
);
2760 wake_up(&rl
->wait
[0]);
2761 wake_up(&rl
->wait
[1]);
2762 wake_up(&rl
->drain
);
2765 static int wait_drain(request_queue_t
*q
, struct request_list
*rl
, int dispatch
)
2767 int wait
= rl
->count
[READ
] + rl
->count
[WRITE
];
2770 wait
+= !list_empty(&q
->queue_head
);
2776 * We rely on the fact that only requests allocated through blk_alloc_request()
2777 * have io scheduler private data structures associated with them. Any other
2778 * type of request (allocated on stack or through kmalloc()) should not go
2779 * to the io scheduler core, but be attached to the queue head instead.
2781 void blk_wait_queue_drained(request_queue_t
*q
, int wait_dispatch
)
2783 struct request_list
*rl
= &q
->rq
;
2786 spin_lock_irq(q
->queue_lock
);
2787 set_bit(QUEUE_FLAG_DRAIN
, &q
->queue_flags
);
2789 while (wait_drain(q
, rl
, wait_dispatch
)) {
2790 prepare_to_wait(&rl
->drain
, &wait
, TASK_UNINTERRUPTIBLE
);
2792 if (wait_drain(q
, rl
, wait_dispatch
)) {
2793 __generic_unplug_device(q
);
2794 spin_unlock_irq(q
->queue_lock
);
2796 spin_lock_irq(q
->queue_lock
);
2799 finish_wait(&rl
->drain
, &wait
);
2802 spin_unlock_irq(q
->queue_lock
);
2806 * block waiting for the io scheduler being started again.
2808 static inline void block_wait_queue_running(request_queue_t
*q
)
2812 while (unlikely(test_bit(QUEUE_FLAG_DRAIN
, &q
->queue_flags
))) {
2813 struct request_list
*rl
= &q
->rq
;
2815 prepare_to_wait_exclusive(&rl
->drain
, &wait
,
2816 TASK_UNINTERRUPTIBLE
);
2819 * re-check the condition. avoids using prepare_to_wait()
2820 * in the fast path (queue is running)
2822 if (test_bit(QUEUE_FLAG_DRAIN
, &q
->queue_flags
))
2825 finish_wait(&rl
->drain
, &wait
);
2829 static void handle_bad_sector(struct bio
*bio
)
2831 char b
[BDEVNAME_SIZE
];
2833 printk(KERN_INFO
"attempt to access beyond end of device\n");
2834 printk(KERN_INFO
"%s: rw=%ld, want=%Lu, limit=%Lu\n",
2835 bdevname(bio
->bi_bdev
, b
),
2837 (unsigned long long)bio
->bi_sector
+ bio_sectors(bio
),
2838 (long long)(bio
->bi_bdev
->bd_inode
->i_size
>> 9));
2840 set_bit(BIO_EOF
, &bio
->bi_flags
);
2844 * generic_make_request: hand a buffer to its device driver for I/O
2845 * @bio: The bio describing the location in memory and on the device.
2847 * generic_make_request() is used to make I/O requests of block
2848 * devices. It is passed a &struct bio, which describes the I/O that needs
2851 * generic_make_request() does not return any status. The
2852 * success/failure status of the request, along with notification of
2853 * completion, is delivered asynchronously through the bio->bi_end_io
2854 * function described (one day) else where.
2856 * The caller of generic_make_request must make sure that bi_io_vec
2857 * are set to describe the memory buffer, and that bi_dev and bi_sector are
2858 * set to describe the device address, and the
2859 * bi_end_io and optionally bi_private are set to describe how
2860 * completion notification should be signaled.
2862 * generic_make_request and the drivers it calls may use bi_next if this
2863 * bio happens to be merged with someone else, and may change bi_dev and
2864 * bi_sector for remaps as it sees fit. So the values of these fields
2865 * should NOT be depended on after the call to generic_make_request.
2867 void generic_make_request(struct bio
*bio
)
2871 int ret
, nr_sectors
= bio_sectors(bio
);
2874 /* Test device or partition size, when known. */
2875 maxsector
= bio
->bi_bdev
->bd_inode
->i_size
>> 9;
2877 sector_t sector
= bio
->bi_sector
;
2879 if (maxsector
< nr_sectors
|| maxsector
- nr_sectors
< sector
) {
2881 * This may well happen - the kernel calls bread()
2882 * without checking the size of the device, e.g., when
2883 * mounting a device.
2885 handle_bad_sector(bio
);
2891 * Resolve the mapping until finished. (drivers are
2892 * still free to implement/resolve their own stacking
2893 * by explicitly returning 0)
2895 * NOTE: we don't repeat the blk_size check for each new device.
2896 * Stacking drivers are expected to know what they are doing.
2899 char b
[BDEVNAME_SIZE
];
2901 q
= bdev_get_queue(bio
->bi_bdev
);
2904 "generic_make_request: Trying to access "
2905 "nonexistent block-device %s (%Lu)\n",
2906 bdevname(bio
->bi_bdev
, b
),
2907 (long long) bio
->bi_sector
);
2909 bio_endio(bio
, bio
->bi_size
, -EIO
);
2913 if (unlikely(bio_sectors(bio
) > q
->max_hw_sectors
)) {
2914 printk("bio too big device %s (%u > %u)\n",
2915 bdevname(bio
->bi_bdev
, b
),
2921 if (unlikely(test_bit(QUEUE_FLAG_DEAD
, &q
->queue_flags
)))
2924 block_wait_queue_running(q
);
2927 * If this device has partitions, remap block n
2928 * of partition p to block n+start(p) of the disk.
2930 blk_partition_remap(bio
);
2932 ret
= q
->make_request_fn(q
, bio
);
2936 EXPORT_SYMBOL(generic_make_request
);
2939 * submit_bio: submit a bio to the block device layer for I/O
2940 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
2941 * @bio: The &struct bio which describes the I/O
2943 * submit_bio() is very similar in purpose to generic_make_request(), and
2944 * uses that function to do most of the work. Both are fairly rough
2945 * interfaces, @bio must be presetup and ready for I/O.
2948 void submit_bio(int rw
, struct bio
*bio
)
2950 int count
= bio_sectors(bio
);
2952 BIO_BUG_ON(!bio
->bi_size
);
2953 BIO_BUG_ON(!bio
->bi_io_vec
);
2956 mod_page_state(pgpgout
, count
);
2958 mod_page_state(pgpgin
, count
);
2960 if (unlikely(block_dump
)) {
2961 char b
[BDEVNAME_SIZE
];
2962 printk(KERN_DEBUG
"%s(%d): %s block %Lu on %s\n",
2963 current
->comm
, current
->pid
,
2964 (rw
& WRITE
) ? "WRITE" : "READ",
2965 (unsigned long long)bio
->bi_sector
,
2966 bdevname(bio
->bi_bdev
,b
));
2969 generic_make_request(bio
);
2972 EXPORT_SYMBOL(submit_bio
);
2974 void blk_recalc_rq_segments(struct request
*rq
)
2976 struct bio
*bio
, *prevbio
= NULL
;
2977 int nr_phys_segs
, nr_hw_segs
;
2978 unsigned int phys_size
, hw_size
;
2979 request_queue_t
*q
= rq
->q
;
2984 phys_size
= hw_size
= nr_phys_segs
= nr_hw_segs
= 0;
2985 rq_for_each_bio(bio
, rq
) {
2986 /* Force bio hw/phys segs to be recalculated. */
2987 bio
->bi_flags
&= ~(1 << BIO_SEG_VALID
);
2989 nr_phys_segs
+= bio_phys_segments(q
, bio
);
2990 nr_hw_segs
+= bio_hw_segments(q
, bio
);
2992 int pseg
= phys_size
+ prevbio
->bi_size
+ bio
->bi_size
;
2993 int hseg
= hw_size
+ prevbio
->bi_size
+ bio
->bi_size
;
2995 if (blk_phys_contig_segment(q
, prevbio
, bio
) &&
2996 pseg
<= q
->max_segment_size
) {
2998 phys_size
+= prevbio
->bi_size
+ bio
->bi_size
;
3002 if (blk_hw_contig_segment(q
, prevbio
, bio
) &&
3003 hseg
<= q
->max_segment_size
) {
3005 hw_size
+= prevbio
->bi_size
+ bio
->bi_size
;
3012 rq
->nr_phys_segments
= nr_phys_segs
;
3013 rq
->nr_hw_segments
= nr_hw_segs
;
3016 void blk_recalc_rq_sectors(struct request
*rq
, int nsect
)
3018 if (blk_fs_request(rq
)) {
3019 rq
->hard_sector
+= nsect
;
3020 rq
->hard_nr_sectors
-= nsect
;
3023 * Move the I/O submission pointers ahead if required.
3025 if ((rq
->nr_sectors
>= rq
->hard_nr_sectors
) &&
3026 (rq
->sector
<= rq
->hard_sector
)) {
3027 rq
->sector
= rq
->hard_sector
;
3028 rq
->nr_sectors
= rq
->hard_nr_sectors
;
3029 rq
->hard_cur_sectors
= bio_cur_sectors(rq
->bio
);
3030 rq
->current_nr_sectors
= rq
->hard_cur_sectors
;
3031 rq
->buffer
= bio_data(rq
->bio
);
3035 * if total number of sectors is less than the first segment
3036 * size, something has gone terribly wrong
3038 if (rq
->nr_sectors
< rq
->current_nr_sectors
) {
3039 printk("blk: request botched\n");
3040 rq
->nr_sectors
= rq
->current_nr_sectors
;
3045 static int __end_that_request_first(struct request
*req
, int uptodate
,
3048 int total_bytes
, bio_nbytes
, error
, next_idx
= 0;
3052 * extend uptodate bool to allow < 0 value to be direct io error
3055 if (end_io_error(uptodate
))
3056 error
= !uptodate
? -EIO
: uptodate
;
3059 * for a REQ_BLOCK_PC request, we want to carry any eventual
3060 * sense key with us all the way through
3062 if (!blk_pc_request(req
))
3066 if (blk_fs_request(req
) && !(req
->flags
& REQ_QUIET
))
3067 printk("end_request: I/O error, dev %s, sector %llu\n",
3068 req
->rq_disk
? req
->rq_disk
->disk_name
: "?",
3069 (unsigned long long)req
->sector
);
3072 total_bytes
= bio_nbytes
= 0;
3073 while ((bio
= req
->bio
) != NULL
) {
3076 if (nr_bytes
>= bio
->bi_size
) {
3077 req
->bio
= bio
->bi_next
;
3078 nbytes
= bio
->bi_size
;
3079 bio_endio(bio
, nbytes
, error
);
3083 int idx
= bio
->bi_idx
+ next_idx
;
3085 if (unlikely(bio
->bi_idx
>= bio
->bi_vcnt
)) {
3086 blk_dump_rq_flags(req
, "__end_that");
3087 printk("%s: bio idx %d >= vcnt %d\n",
3089 bio
->bi_idx
, bio
->bi_vcnt
);
3093 nbytes
= bio_iovec_idx(bio
, idx
)->bv_len
;
3094 BIO_BUG_ON(nbytes
> bio
->bi_size
);
3097 * not a complete bvec done
3099 if (unlikely(nbytes
> nr_bytes
)) {
3100 bio_nbytes
+= nr_bytes
;
3101 total_bytes
+= nr_bytes
;
3106 * advance to the next vector
3109 bio_nbytes
+= nbytes
;
3112 total_bytes
+= nbytes
;
3115 if ((bio
= req
->bio
)) {
3117 * end more in this run, or just return 'not-done'
3119 if (unlikely(nr_bytes
<= 0))
3131 * if the request wasn't completed, update state
3134 bio_endio(bio
, bio_nbytes
, error
);
3135 bio
->bi_idx
+= next_idx
;
3136 bio_iovec(bio
)->bv_offset
+= nr_bytes
;
3137 bio_iovec(bio
)->bv_len
-= nr_bytes
;
3140 blk_recalc_rq_sectors(req
, total_bytes
>> 9);
3141 blk_recalc_rq_segments(req
);
3146 * end_that_request_first - end I/O on a request
3147 * @req: the request being processed
3148 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3149 * @nr_sectors: number of sectors to end I/O on
3152 * Ends I/O on a number of sectors attached to @req, and sets it up
3153 * for the next range of segments (if any) in the cluster.
3156 * 0 - we are done with this request, call end_that_request_last()
3157 * 1 - still buffers pending for this request
3159 int end_that_request_first(struct request
*req
, int uptodate
, int nr_sectors
)
3161 return __end_that_request_first(req
, uptodate
, nr_sectors
<< 9);
3164 EXPORT_SYMBOL(end_that_request_first
);
3167 * end_that_request_chunk - end I/O on a request
3168 * @req: the request being processed
3169 * @uptodate: 1 for success, 0 for I/O error, < 0 for specific error
3170 * @nr_bytes: number of bytes to complete
3173 * Ends I/O on a number of bytes attached to @req, and sets it up
3174 * for the next range of segments (if any). Like end_that_request_first(),
3175 * but deals with bytes instead of sectors.
3178 * 0 - we are done with this request, call end_that_request_last()
3179 * 1 - still buffers pending for this request
3181 int end_that_request_chunk(struct request
*req
, int uptodate
, int nr_bytes
)
3183 return __end_that_request_first(req
, uptodate
, nr_bytes
);
3186 EXPORT_SYMBOL(end_that_request_chunk
);
3189 * queue lock must be held
3191 void end_that_request_last(struct request
*req
)
3193 struct gendisk
*disk
= req
->rq_disk
;
3195 if (unlikely(laptop_mode
) && blk_fs_request(req
))
3196 laptop_io_completion();
3198 if (disk
&& blk_fs_request(req
)) {
3199 unsigned long duration
= jiffies
- req
->start_time
;
3200 switch (rq_data_dir(req
)) {
3202 __disk_stat_inc(disk
, writes
);
3203 __disk_stat_add(disk
, write_ticks
, duration
);
3206 __disk_stat_inc(disk
, reads
);
3207 __disk_stat_add(disk
, read_ticks
, duration
);
3210 disk_round_stats(disk
);
3216 __blk_put_request(req
->q
, req
);
3219 EXPORT_SYMBOL(end_that_request_last
);
3221 void end_request(struct request
*req
, int uptodate
)
3223 if (!end_that_request_first(req
, uptodate
, req
->hard_cur_sectors
)) {
3224 add_disk_randomness(req
->rq_disk
);
3225 blkdev_dequeue_request(req
);
3226 end_that_request_last(req
);
3230 EXPORT_SYMBOL(end_request
);
3232 void blk_rq_bio_prep(request_queue_t
*q
, struct request
*rq
, struct bio
*bio
)
3234 /* first three bits are identical in rq->flags and bio->bi_rw */
3235 rq
->flags
|= (bio
->bi_rw
& 7);
3237 rq
->nr_phys_segments
= bio_phys_segments(q
, bio
);
3238 rq
->nr_hw_segments
= bio_hw_segments(q
, bio
);
3239 rq
->current_nr_sectors
= bio_cur_sectors(bio
);
3240 rq
->hard_cur_sectors
= rq
->current_nr_sectors
;
3241 rq
->hard_nr_sectors
= rq
->nr_sectors
= bio_sectors(bio
);
3242 rq
->buffer
= bio_data(bio
);
3244 rq
->bio
= rq
->biotail
= bio
;
3247 EXPORT_SYMBOL(blk_rq_bio_prep
);
3249 int kblockd_schedule_work(struct work_struct
*work
)
3251 return queue_work(kblockd_workqueue
, work
);
3254 EXPORT_SYMBOL(kblockd_schedule_work
);
3256 void kblockd_flush(void)
3258 flush_workqueue(kblockd_workqueue
);
3260 EXPORT_SYMBOL(kblockd_flush
);
3262 int __init
blk_dev_init(void)
3264 kblockd_workqueue
= create_workqueue("kblockd");
3265 if (!kblockd_workqueue
)
3266 panic("Failed to create kblockd\n");
3268 request_cachep
= kmem_cache_create("blkdev_requests",
3269 sizeof(struct request
), 0, SLAB_PANIC
, NULL
, NULL
);
3271 requestq_cachep
= kmem_cache_create("blkdev_queue",
3272 sizeof(request_queue_t
), 0, SLAB_PANIC
, NULL
, NULL
);
3274 iocontext_cachep
= kmem_cache_create("blkdev_ioc",
3275 sizeof(struct io_context
), 0, SLAB_PANIC
, NULL
, NULL
);
3277 blk_max_low_pfn
= max_low_pfn
;
3278 blk_max_pfn
= max_pfn
;
3284 * IO Context helper functions
3286 void put_io_context(struct io_context
*ioc
)
3291 BUG_ON(atomic_read(&ioc
->refcount
) == 0);
3293 if (atomic_dec_and_test(&ioc
->refcount
)) {
3294 if (ioc
->aic
&& ioc
->aic
->dtor
)
3295 ioc
->aic
->dtor(ioc
->aic
);
3296 if (ioc
->cic
&& ioc
->cic
->dtor
)
3297 ioc
->cic
->dtor(ioc
->cic
);
3299 kmem_cache_free(iocontext_cachep
, ioc
);
3302 EXPORT_SYMBOL(put_io_context
);
3304 /* Called by the exitting task */
3305 void exit_io_context(void)
3307 unsigned long flags
;
3308 struct io_context
*ioc
;
3310 local_irq_save(flags
);
3311 ioc
= current
->io_context
;
3312 current
->io_context
= NULL
;
3313 local_irq_restore(flags
);
3315 if (ioc
->aic
&& ioc
->aic
->exit
)
3316 ioc
->aic
->exit(ioc
->aic
);
3317 if (ioc
->cic
&& ioc
->cic
->exit
)
3318 ioc
->cic
->exit(ioc
->cic
);
3320 put_io_context(ioc
);
3324 * If the current task has no IO context then create one and initialise it.
3325 * If it does have a context, take a ref on it.
3327 * This is always called in the context of the task which submitted the I/O.
3328 * But weird things happen, so we disable local interrupts to ensure exclusive
3329 * access to *current.
3331 struct io_context
*get_io_context(int gfp_flags
)
3333 struct task_struct
*tsk
= current
;
3334 unsigned long flags
;
3335 struct io_context
*ret
;
3337 local_irq_save(flags
);
3338 ret
= tsk
->io_context
;
3342 local_irq_restore(flags
);
3344 ret
= kmem_cache_alloc(iocontext_cachep
, gfp_flags
);
3346 atomic_set(&ret
->refcount
, 1);
3347 ret
->pid
= tsk
->pid
;
3348 ret
->last_waited
= jiffies
; /* doesn't matter... */
3349 ret
->nr_batch_requests
= 0; /* because this is 0 */
3352 spin_lock_init(&ret
->lock
);
3354 local_irq_save(flags
);
3357 * very unlikely, someone raced with us in setting up the task
3358 * io context. free new context and just grab a reference.
3360 if (!tsk
->io_context
)
3361 tsk
->io_context
= ret
;
3363 kmem_cache_free(iocontext_cachep
, ret
);
3364 ret
= tsk
->io_context
;
3368 atomic_inc(&ret
->refcount
);
3369 local_irq_restore(flags
);
3374 EXPORT_SYMBOL(get_io_context
);
3376 void copy_io_context(struct io_context
**pdst
, struct io_context
**psrc
)
3378 struct io_context
*src
= *psrc
;
3379 struct io_context
*dst
= *pdst
;
3382 BUG_ON(atomic_read(&src
->refcount
) == 0);
3383 atomic_inc(&src
->refcount
);
3384 put_io_context(dst
);
3388 EXPORT_SYMBOL(copy_io_context
);
3390 void swap_io_context(struct io_context
**ioc1
, struct io_context
**ioc2
)
3392 struct io_context
*temp
;
3397 EXPORT_SYMBOL(swap_io_context
);
3402 struct queue_sysfs_entry
{
3403 struct attribute attr
;
3404 ssize_t (*show
)(struct request_queue
*, char *);
3405 ssize_t (*store
)(struct request_queue
*, const char *, size_t);
3409 queue_var_show(unsigned int var
, char *page
)
3411 return sprintf(page
, "%d\n", var
);
3415 queue_var_store(unsigned long *var
, const char *page
, size_t count
)
3417 char *p
= (char *) page
;
3419 *var
= simple_strtoul(p
, &p
, 10);
3423 static ssize_t
queue_requests_show(struct request_queue
*q
, char *page
)
3425 return queue_var_show(q
->nr_requests
, (page
));
3429 queue_requests_store(struct request_queue
*q
, const char *page
, size_t count
)
3431 struct request_list
*rl
= &q
->rq
;
3433 int ret
= queue_var_store(&q
->nr_requests
, page
, count
);
3434 if (q
->nr_requests
< BLKDEV_MIN_RQ
)
3435 q
->nr_requests
= BLKDEV_MIN_RQ
;
3436 blk_queue_congestion_threshold(q
);
3438 if (rl
->count
[READ
] >= queue_congestion_on_threshold(q
))
3439 set_queue_congested(q
, READ
);
3440 else if (rl
->count
[READ
] < queue_congestion_off_threshold(q
))
3441 clear_queue_congested(q
, READ
);
3443 if (rl
->count
[WRITE
] >= queue_congestion_on_threshold(q
))
3444 set_queue_congested(q
, WRITE
);
3445 else if (rl
->count
[WRITE
] < queue_congestion_off_threshold(q
))
3446 clear_queue_congested(q
, WRITE
);
3448 if (rl
->count
[READ
] >= q
->nr_requests
) {
3449 blk_set_queue_full(q
, READ
);
3450 } else if (rl
->count
[READ
]+1 <= q
->nr_requests
) {
3451 blk_clear_queue_full(q
, READ
);
3452 wake_up(&rl
->wait
[READ
]);
3455 if (rl
->count
[WRITE
] >= q
->nr_requests
) {
3456 blk_set_queue_full(q
, WRITE
);
3457 } else if (rl
->count
[WRITE
]+1 <= q
->nr_requests
) {
3458 blk_clear_queue_full(q
, WRITE
);
3459 wake_up(&rl
->wait
[WRITE
]);
3464 static ssize_t
queue_ra_show(struct request_queue
*q
, char *page
)
3466 int ra_kb
= q
->backing_dev_info
.ra_pages
<< (PAGE_CACHE_SHIFT
- 10);
3468 return queue_var_show(ra_kb
, (page
));
3472 queue_ra_store(struct request_queue
*q
, const char *page
, size_t count
)
3474 unsigned long ra_kb
;
3475 ssize_t ret
= queue_var_store(&ra_kb
, page
, count
);
3477 spin_lock_irq(q
->queue_lock
);
3478 if (ra_kb
> (q
->max_sectors
>> 1))
3479 ra_kb
= (q
->max_sectors
>> 1);
3481 q
->backing_dev_info
.ra_pages
= ra_kb
>> (PAGE_CACHE_SHIFT
- 10);
3482 spin_unlock_irq(q
->queue_lock
);
3487 static ssize_t
queue_max_sectors_show(struct request_queue
*q
, char *page
)
3489 int max_sectors_kb
= q
->max_sectors
>> 1;
3491 return queue_var_show(max_sectors_kb
, (page
));
3495 queue_max_sectors_store(struct request_queue
*q
, const char *page
, size_t count
)
3497 unsigned long max_sectors_kb
,
3498 max_hw_sectors_kb
= q
->max_hw_sectors
>> 1,
3499 page_kb
= 1 << (PAGE_CACHE_SHIFT
- 10);
3500 ssize_t ret
= queue_var_store(&max_sectors_kb
, page
, count
);
3503 if (max_sectors_kb
> max_hw_sectors_kb
|| max_sectors_kb
< page_kb
)
3506 * Take the queue lock to update the readahead and max_sectors
3507 * values synchronously:
3509 spin_lock_irq(q
->queue_lock
);
3511 * Trim readahead window as well, if necessary:
3513 ra_kb
= q
->backing_dev_info
.ra_pages
<< (PAGE_CACHE_SHIFT
- 10);
3514 if (ra_kb
> max_sectors_kb
)
3515 q
->backing_dev_info
.ra_pages
=
3516 max_sectors_kb
>> (PAGE_CACHE_SHIFT
- 10);
3518 q
->max_sectors
= max_sectors_kb
<< 1;
3519 spin_unlock_irq(q
->queue_lock
);
3524 static ssize_t
queue_max_hw_sectors_show(struct request_queue
*q
, char *page
)
3526 int max_hw_sectors_kb
= q
->max_hw_sectors
>> 1;
3528 return queue_var_show(max_hw_sectors_kb
, (page
));
3532 static struct queue_sysfs_entry queue_requests_entry
= {
3533 .attr
= {.name
= "nr_requests", .mode
= S_IRUGO
| S_IWUSR
},
3534 .show
= queue_requests_show
,
3535 .store
= queue_requests_store
,
3538 static struct queue_sysfs_entry queue_ra_entry
= {
3539 .attr
= {.name
= "read_ahead_kb", .mode
= S_IRUGO
| S_IWUSR
},
3540 .show
= queue_ra_show
,
3541 .store
= queue_ra_store
,
3544 static struct queue_sysfs_entry queue_max_sectors_entry
= {
3545 .attr
= {.name
= "max_sectors_kb", .mode
= S_IRUGO
| S_IWUSR
},
3546 .show
= queue_max_sectors_show
,
3547 .store
= queue_max_sectors_store
,
3550 static struct queue_sysfs_entry queue_max_hw_sectors_entry
= {
3551 .attr
= {.name
= "max_hw_sectors_kb", .mode
= S_IRUGO
},
3552 .show
= queue_max_hw_sectors_show
,
3555 static struct queue_sysfs_entry queue_iosched_entry
= {
3556 .attr
= {.name
= "scheduler", .mode
= S_IRUGO
| S_IWUSR
},
3557 .show
= elv_iosched_show
,
3558 .store
= elv_iosched_store
,
3561 static struct attribute
*default_attrs
[] = {
3562 &queue_requests_entry
.attr
,
3563 &queue_ra_entry
.attr
,
3564 &queue_max_hw_sectors_entry
.attr
,
3565 &queue_max_sectors_entry
.attr
,
3566 &queue_iosched_entry
.attr
,
3570 #define to_queue(atr) container_of((atr), struct queue_sysfs_entry, attr)
3573 queue_attr_show(struct kobject
*kobj
, struct attribute
*attr
, char *page
)
3575 struct queue_sysfs_entry
*entry
= to_queue(attr
);
3576 struct request_queue
*q
;
3578 q
= container_of(kobj
, struct request_queue
, kobj
);
3582 return entry
->show(q
, page
);
3586 queue_attr_store(struct kobject
*kobj
, struct attribute
*attr
,
3587 const char *page
, size_t length
)
3589 struct queue_sysfs_entry
*entry
= to_queue(attr
);
3590 struct request_queue
*q
;
3592 q
= container_of(kobj
, struct request_queue
, kobj
);
3596 return entry
->store(q
, page
, length
);
3599 static struct sysfs_ops queue_sysfs_ops
= {
3600 .show
= queue_attr_show
,
3601 .store
= queue_attr_store
,
3604 struct kobj_type queue_ktype
= {
3605 .sysfs_ops
= &queue_sysfs_ops
,
3606 .default_attrs
= default_attrs
,
3609 int blk_register_queue(struct gendisk
*disk
)
3613 request_queue_t
*q
= disk
->queue
;
3615 if (!q
|| !q
->request_fn
)
3618 q
->kobj
.parent
= kobject_get(&disk
->kobj
);
3619 if (!q
->kobj
.parent
)
3622 snprintf(q
->kobj
.name
, KOBJ_NAME_LEN
, "%s", "queue");
3623 q
->kobj
.ktype
= &queue_ktype
;
3625 ret
= kobject_register(&q
->kobj
);
3629 ret
= elv_register_queue(q
);
3631 kobject_unregister(&q
->kobj
);
3638 void blk_unregister_queue(struct gendisk
*disk
)
3640 request_queue_t
*q
= disk
->queue
;
3642 if (q
&& q
->request_fn
) {
3643 elv_unregister_queue(q
);
3645 kobject_unregister(&q
->kobj
);
3646 kobject_put(&disk
->kobj
);