446 lines
11 KiB
C
446 lines
11 KiB
C
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/*
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* Functions related to barrier IO handling
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include "blk.h"
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/**
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* blk_queue_ordered - does this queue support ordered writes
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* @q: the request queue
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* @ordered: one of QUEUE_ORDERED_*
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* @prepare_flush_fn: rq setup helper for cache flush ordered writes
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*
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* Description:
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* For journalled file systems, doing ordered writes on a commit
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* block instead of explicitly doing wait_on_buffer (which is bad
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* for performance) can be a big win. Block drivers supporting this
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* feature should call this function and indicate so.
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*
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**/
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int blk_queue_ordered(struct request_queue *q, unsigned ordered,
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prepare_flush_fn *prepare_flush_fn)
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{
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if (!prepare_flush_fn && (ordered & (QUEUE_ORDERED_DO_PREFLUSH |
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QUEUE_ORDERED_DO_POSTFLUSH))) {
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printk(KERN_ERR "%s: prepare_flush_fn required\n", __func__);
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return -EINVAL;
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}
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if (ordered != QUEUE_ORDERED_NONE &&
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ordered != QUEUE_ORDERED_DRAIN &&
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ordered != QUEUE_ORDERED_DRAIN_FLUSH &&
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ordered != QUEUE_ORDERED_DRAIN_FUA &&
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ordered != QUEUE_ORDERED_TAG &&
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ordered != QUEUE_ORDERED_TAG_FLUSH &&
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ordered != QUEUE_ORDERED_TAG_FUA) {
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printk(KERN_ERR "blk_queue_ordered: bad value %d\n", ordered);
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return -EINVAL;
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}
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q->ordered = ordered;
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q->next_ordered = ordered;
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q->prepare_flush_fn = prepare_flush_fn;
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return 0;
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}
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EXPORT_SYMBOL(blk_queue_ordered);
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/*
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* Cache flushing for ordered writes handling
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*/
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unsigned blk_ordered_cur_seq(struct request_queue *q)
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{
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if (!q->ordseq)
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return 0;
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return 1 << ffz(q->ordseq);
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}
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unsigned blk_ordered_req_seq(struct request *rq)
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{
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struct request_queue *q = rq->q;
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BUG_ON(q->ordseq == 0);
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if (rq == &q->pre_flush_rq)
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return QUEUE_ORDSEQ_PREFLUSH;
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if (rq == &q->bar_rq)
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return QUEUE_ORDSEQ_BAR;
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if (rq == &q->post_flush_rq)
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return QUEUE_ORDSEQ_POSTFLUSH;
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/*
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* !fs requests don't need to follow barrier ordering. Always
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* put them at the front. This fixes the following deadlock.
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*
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* http://thread.gmane.org/gmane.linux.kernel/537473
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*/
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if (!blk_fs_request(rq))
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return QUEUE_ORDSEQ_DRAIN;
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if ((rq->cmd_flags & REQ_ORDERED_COLOR) ==
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(q->orig_bar_rq->cmd_flags & REQ_ORDERED_COLOR))
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return QUEUE_ORDSEQ_DRAIN;
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else
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return QUEUE_ORDSEQ_DONE;
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}
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bool blk_ordered_complete_seq(struct request_queue *q, unsigned seq, int error)
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{
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struct request *rq;
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if (error && !q->orderr)
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q->orderr = error;
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BUG_ON(q->ordseq & seq);
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q->ordseq |= seq;
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if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE)
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return false;
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/*
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* Okay, sequence complete.
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*/
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q->ordseq = 0;
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rq = q->orig_bar_rq;
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__blk_end_request_all(rq, q->orderr);
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return true;
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}
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static void pre_flush_end_io(struct request *rq, int error)
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{
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elv_completed_request(rq->q, rq);
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blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
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}
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static void bar_end_io(struct request *rq, int error)
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{
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elv_completed_request(rq->q, rq);
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blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
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}
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static void post_flush_end_io(struct request *rq, int error)
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{
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elv_completed_request(rq->q, rq);
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blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
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}
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static void queue_flush(struct request_queue *q, unsigned which)
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{
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struct request *rq;
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rq_end_io_fn *end_io;
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if (which == QUEUE_ORDERED_DO_PREFLUSH) {
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rq = &q->pre_flush_rq;
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end_io = pre_flush_end_io;
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} else {
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rq = &q->post_flush_rq;
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end_io = post_flush_end_io;
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}
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blk_rq_init(q, rq);
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rq->cmd_flags = REQ_HARDBARRIER;
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rq->rq_disk = q->bar_rq.rq_disk;
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rq->end_io = end_io;
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q->prepare_flush_fn(q, rq);
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elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
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}
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static inline bool start_ordered(struct request_queue *q, struct request **rqp)
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{
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struct request *rq = *rqp;
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unsigned skip = 0;
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q->orderr = 0;
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q->ordered = q->next_ordered;
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q->ordseq |= QUEUE_ORDSEQ_STARTED;
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/*
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* For an empty barrier, there's no actual BAR request, which
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* in turn makes POSTFLUSH unnecessary. Mask them off.
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*/
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if (!blk_rq_sectors(rq)) {
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q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
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QUEUE_ORDERED_DO_POSTFLUSH);
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/*
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* Empty barrier on a write-through device w/ ordered
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* tag has no command to issue and without any command
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* to issue, ordering by tag can't be used. Drain
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* instead.
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*/
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if ((q->ordered & QUEUE_ORDERED_BY_TAG) &&
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!(q->ordered & QUEUE_ORDERED_DO_PREFLUSH)) {
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q->ordered &= ~QUEUE_ORDERED_BY_TAG;
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q->ordered |= QUEUE_ORDERED_BY_DRAIN;
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}
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}
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/* stash away the original request */
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blk_dequeue_request(rq);
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q->orig_bar_rq = rq;
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rq = NULL;
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/*
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* Queue ordered sequence. As we stack them at the head, we
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* need to queue in reverse order. Note that we rely on that
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* no fs request uses ELEVATOR_INSERT_FRONT and thus no fs
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* request gets inbetween ordered sequence.
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*/
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if (q->ordered & QUEUE_ORDERED_DO_POSTFLUSH) {
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queue_flush(q, QUEUE_ORDERED_DO_POSTFLUSH);
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rq = &q->post_flush_rq;
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} else
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skip |= QUEUE_ORDSEQ_POSTFLUSH;
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if (q->ordered & QUEUE_ORDERED_DO_BAR) {
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rq = &q->bar_rq;
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/* initialize proxy request and queue it */
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blk_rq_init(q, rq);
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if (bio_data_dir(q->orig_bar_rq->bio) == WRITE)
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rq->cmd_flags |= REQ_RW;
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if (q->ordered & QUEUE_ORDERED_DO_FUA)
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rq->cmd_flags |= REQ_FUA;
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init_request_from_bio(rq, q->orig_bar_rq->bio);
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rq->end_io = bar_end_io;
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elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
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} else
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skip |= QUEUE_ORDSEQ_BAR;
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if (q->ordered & QUEUE_ORDERED_DO_PREFLUSH) {
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queue_flush(q, QUEUE_ORDERED_DO_PREFLUSH);
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rq = &q->pre_flush_rq;
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} else
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skip |= QUEUE_ORDSEQ_PREFLUSH;
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if ((q->ordered & QUEUE_ORDERED_BY_DRAIN) && queue_in_flight(q))
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rq = NULL;
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else
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skip |= QUEUE_ORDSEQ_DRAIN;
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*rqp = rq;
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/*
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* Complete skipped sequences. If whole sequence is complete,
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* return false to tell elevator that this request is gone.
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*/
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return !blk_ordered_complete_seq(q, skip, 0);
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}
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bool blk_do_ordered(struct request_queue *q, struct request **rqp)
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{
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struct request *rq = *rqp;
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const int is_barrier = blk_fs_request(rq) && blk_barrier_rq(rq);
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if (!q->ordseq) {
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if (!is_barrier)
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return true;
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if (q->next_ordered != QUEUE_ORDERED_NONE)
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return start_ordered(q, rqp);
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else {
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/*
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* Queue ordering not supported. Terminate
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* with prejudice.
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*/
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blk_dequeue_request(rq);
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__blk_end_request_all(rq, -EOPNOTSUPP);
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*rqp = NULL;
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return false;
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}
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}
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/*
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* Ordered sequence in progress
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*/
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/* Special requests are not subject to ordering rules. */
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if (!blk_fs_request(rq) &&
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rq != &q->pre_flush_rq && rq != &q->post_flush_rq)
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return true;
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if (q->ordered & QUEUE_ORDERED_BY_TAG) {
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/* Ordered by tag. Blocking the next barrier is enough. */
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if (is_barrier && rq != &q->bar_rq)
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*rqp = NULL;
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} else {
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/* Ordered by draining. Wait for turn. */
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WARN_ON(blk_ordered_req_seq(rq) < blk_ordered_cur_seq(q));
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if (blk_ordered_req_seq(rq) > blk_ordered_cur_seq(q))
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*rqp = NULL;
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}
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return true;
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}
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static void bio_end_empty_barrier(struct bio *bio, int err)
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{
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if (err) {
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if (err == -EOPNOTSUPP)
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set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
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clear_bit(BIO_UPTODATE, &bio->bi_flags);
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}
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complete(bio->bi_private);
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}
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/**
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* blkdev_issue_flush - queue a flush
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* @bdev: blockdev to issue flush for
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* @error_sector: error sector
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*
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* Description:
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* Issue a flush for the block device in question. Caller can supply
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* room for storing the error offset in case of a flush error, if they
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* wish to.
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*/
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int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector)
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{
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DECLARE_COMPLETION_ONSTACK(wait);
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struct request_queue *q;
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struct bio *bio;
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int ret;
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if (bdev->bd_disk == NULL)
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return -ENXIO;
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q = bdev_get_queue(bdev);
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if (!q)
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return -ENXIO;
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bio = bio_alloc(GFP_KERNEL, 0);
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bio->bi_end_io = bio_end_empty_barrier;
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bio->bi_private = &wait;
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bio->bi_bdev = bdev;
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submit_bio(WRITE_BARRIER, bio);
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wait_for_completion(&wait);
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/*
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* The driver must store the error location in ->bi_sector, if
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* it supports it. For non-stacked drivers, this should be copied
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* from blk_rq_pos(rq).
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*/
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if (error_sector)
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*error_sector = bio->bi_sector;
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ret = 0;
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if (bio_flagged(bio, BIO_EOPNOTSUPP))
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ret = -EOPNOTSUPP;
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else if (!bio_flagged(bio, BIO_UPTODATE))
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ret = -EIO;
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bio_put(bio);
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return ret;
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}
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EXPORT_SYMBOL(blkdev_issue_flush);
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static void blkdev_discard_end_io(struct bio *bio, int err)
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{
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if (err) {
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if (err == -EOPNOTSUPP)
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set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
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clear_bit(BIO_UPTODATE, &bio->bi_flags);
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}
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if (bio->bi_private)
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complete(bio->bi_private);
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__free_page(bio_page(bio));
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bio_put(bio);
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}
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/**
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* blkdev_issue_discard - queue a discard
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* @bdev: blockdev to issue discard for
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* @sector: start sector
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* @nr_sects: number of sectors to discard
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* @gfp_mask: memory allocation flags (for bio_alloc)
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* @flags: DISCARD_FL_* flags to control behaviour
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*
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* Description:
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* Issue a discard request for the sectors in question.
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*/
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int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
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sector_t nr_sects, gfp_t gfp_mask, int flags)
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{
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DECLARE_COMPLETION_ONSTACK(wait);
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struct request_queue *q = bdev_get_queue(bdev);
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int type = flags & DISCARD_FL_BARRIER ?
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DISCARD_BARRIER : DISCARD_NOBARRIER;
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struct bio *bio;
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||
|
|
struct page *page;
|
||
|
|
int ret = 0;
|
||
|
|
|
||
|
|
if (!q)
|
||
|
|
return -ENXIO;
|
||
|
|
|
||
|
|
if (!blk_queue_discard(q))
|
||
|
|
return -EOPNOTSUPP;
|
||
|
|
|
||
|
|
while (nr_sects && !ret) {
|
||
|
|
unsigned int sector_size = q->limits.logical_block_size;
|
||
|
|
unsigned int max_discard_sectors =
|
||
|
|
min(q->limits.max_discard_sectors, UINT_MAX >> 9);
|
||
|
|
|
||
|
|
bio = bio_alloc(gfp_mask, 1);
|
||
|
|
if (!bio)
|
||
|
|
goto out;
|
||
|
|
bio->bi_sector = sector;
|
||
|
|
bio->bi_end_io = blkdev_discard_end_io;
|
||
|
|
bio->bi_bdev = bdev;
|
||
|
|
if (flags & DISCARD_FL_WAIT)
|
||
|
|
bio->bi_private = &wait;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* Add a zeroed one-sector payload as that's what
|
||
|
|
* our current implementations need. If we'll ever need
|
||
|
|
* more the interface will need revisiting.
|
||
|
|
*/
|
||
|
|
page = alloc_page(GFP_KERNEL | __GFP_ZERO);
|
||
|
|
if (!page)
|
||
|
|
goto out_free_bio;
|
||
|
|
if (bio_add_pc_page(q, bio, page, sector_size, 0) < sector_size)
|
||
|
|
goto out_free_page;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* And override the bio size - the way discard works we
|
||
|
|
* touch many more blocks on disk than the actual payload
|
||
|
|
* length.
|
||
|
|
*/
|
||
|
|
if (nr_sects > max_discard_sectors) {
|
||
|
|
bio->bi_size = max_discard_sectors << 9;
|
||
|
|
nr_sects -= max_discard_sectors;
|
||
|
|
sector += max_discard_sectors;
|
||
|
|
} else {
|
||
|
|
bio->bi_size = nr_sects << 9;
|
||
|
|
nr_sects = 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
bio_get(bio);
|
||
|
|
submit_bio(type, bio);
|
||
|
|
|
||
|
|
if (flags & DISCARD_FL_WAIT)
|
||
|
|
wait_for_completion(&wait);
|
||
|
|
|
||
|
|
if (bio_flagged(bio, BIO_EOPNOTSUPP))
|
||
|
|
ret = -EOPNOTSUPP;
|
||
|
|
else if (!bio_flagged(bio, BIO_UPTODATE))
|
||
|
|
ret = -EIO;
|
||
|
|
bio_put(bio);
|
||
|
|
}
|
||
|
|
return ret;
|
||
|
|
out_free_page:
|
||
|
|
__free_page(page);
|
||
|
|
out_free_bio:
|
||
|
|
bio_put(bio);
|
||
|
|
out:
|
||
|
|
return -ENOMEM;
|
||
|
|
}
|
||
|
|
EXPORT_SYMBOL(blkdev_issue_discard);
|