blob: e8b2e5c091b1f7c5112667e239dd6f919b458cf1 [file] [log] [blame]
/*
* Functions related to barrier IO handling
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/gfp.h>
#include "blk.h"
static struct request *queue_next_ordseq(struct request_queue *q);
/*
* Cache flushing for ordered writes handling
*/
unsigned blk_ordered_cur_seq(struct request_queue *q)
{
if (!q->ordseq)
return 0;
return 1 << ffz(q->ordseq);
}
static struct request *blk_ordered_complete_seq(struct request_queue *q,
unsigned seq, int error)
{
struct request *next_rq = NULL;
if (error && !q->orderr)
q->orderr = error;
BUG_ON(q->ordseq & seq);
q->ordseq |= seq;
if (blk_ordered_cur_seq(q) != QUEUE_ORDSEQ_DONE) {
/* not complete yet, queue the next ordered sequence */
next_rq = queue_next_ordseq(q);
} else {
/* complete this barrier request */
__blk_end_request_all(q->orig_bar_rq, q->orderr);
q->orig_bar_rq = NULL;
q->ordseq = 0;
/* dispatch the next barrier if there's one */
if (!list_empty(&q->pending_barriers)) {
next_rq = list_entry_rq(q->pending_barriers.next);
list_move(&next_rq->queuelist, &q->queue_head);
}
}
return next_rq;
}
static void pre_flush_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_PREFLUSH, error);
}
static void bar_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_BAR, error);
}
static void post_flush_end_io(struct request *rq, int error)
{
elv_completed_request(rq->q, rq);
blk_ordered_complete_seq(rq->q, QUEUE_ORDSEQ_POSTFLUSH, error);
}
static void queue_flush(struct request_queue *q, struct request *rq,
rq_end_io_fn *end_io)
{
blk_rq_init(q, rq);
rq->cmd_type = REQ_TYPE_FS;
rq->cmd_flags = REQ_FLUSH;
rq->rq_disk = q->orig_bar_rq->rq_disk;
rq->end_io = end_io;
elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
}
static struct request *queue_next_ordseq(struct request_queue *q)
{
struct request *rq = &q->bar_rq;
switch (blk_ordered_cur_seq(q)) {
case QUEUE_ORDSEQ_PREFLUSH:
queue_flush(q, rq, pre_flush_end_io);
break;
case QUEUE_ORDSEQ_BAR:
/* initialize proxy request and queue it */
blk_rq_init(q, rq);
init_request_from_bio(rq, q->orig_bar_rq->bio);
rq->cmd_flags &= ~REQ_HARDBARRIER;
if (q->ordered & QUEUE_ORDERED_DO_FUA)
rq->cmd_flags |= REQ_FUA;
rq->end_io = bar_end_io;
elv_insert(q, rq, ELEVATOR_INSERT_FRONT);
break;
case QUEUE_ORDSEQ_POSTFLUSH:
queue_flush(q, rq, post_flush_end_io);
break;
default:
BUG();
}
return rq;
}
struct request *blk_do_ordered(struct request_queue *q, struct request *rq)
{
unsigned skip = 0;
if (!(rq->cmd_flags & REQ_HARDBARRIER))
return rq;
if (q->ordseq) {
/*
* Barrier is already in progress and they can't be
* processed in parallel. Queue for later processing.
*/
list_move_tail(&rq->queuelist, &q->pending_barriers);
return NULL;
}
if (unlikely(q->next_ordered == QUEUE_ORDERED_NONE)) {
/*
* Queue ordering not supported. Terminate
* with prejudice.
*/
blk_dequeue_request(rq);
__blk_end_request_all(rq, -EOPNOTSUPP);
return NULL;
}
/*
* Start a new ordered sequence
*/
q->orderr = 0;
q->ordered = q->next_ordered;
q->ordseq |= QUEUE_ORDSEQ_STARTED;
/*
* For an empty barrier, there's no actual BAR request, which
* in turn makes POSTFLUSH unnecessary. Mask them off.
*/
if (!blk_rq_sectors(rq))
q->ordered &= ~(QUEUE_ORDERED_DO_BAR |
QUEUE_ORDERED_DO_POSTFLUSH);
/* stash away the original request */
blk_dequeue_request(rq);
q->orig_bar_rq = rq;
if (!(q->ordered & QUEUE_ORDERED_DO_PREFLUSH))
skip |= QUEUE_ORDSEQ_PREFLUSH;
if (!(q->ordered & QUEUE_ORDERED_DO_BAR))
skip |= QUEUE_ORDSEQ_BAR;
if (!(q->ordered & QUEUE_ORDERED_DO_POSTFLUSH))
skip |= QUEUE_ORDSEQ_POSTFLUSH;
/* complete skipped sequences and return the first sequence */
return blk_ordered_complete_seq(q, skip, 0);
}
static void bio_end_empty_barrier(struct bio *bio, int err)
{
if (err) {
if (err == -EOPNOTSUPP)
set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
clear_bit(BIO_UPTODATE, &bio->bi_flags);
}
if (bio->bi_private)
complete(bio->bi_private);
bio_put(bio);
}
/**
* blkdev_issue_flush - queue a flush
* @bdev: blockdev to issue flush for
* @gfp_mask: memory allocation flags (for bio_alloc)
* @error_sector: error sector
* @flags: BLKDEV_IFL_* flags to control behaviour
*
* Description:
* Issue a flush for the block device in question. Caller can supply
* room for storing the error offset in case of a flush error, if they
* wish to. If WAIT flag is not passed then caller may check only what
* request was pushed in some internal queue for later handling.
*/
int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
sector_t *error_sector, unsigned long flags)
{
DECLARE_COMPLETION_ONSTACK(wait);
struct request_queue *q;
struct bio *bio;
int ret = 0;
if (bdev->bd_disk == NULL)
return -ENXIO;
q = bdev_get_queue(bdev);
if (!q)
return -ENXIO;
/*
* some block devices may not have their queue correctly set up here
* (e.g. loop device without a backing file) and so issuing a flush
* here will panic. Ensure there is a request function before issuing
* the barrier.
*/
if (!q->make_request_fn)
return -ENXIO;
bio = bio_alloc(gfp_mask, 0);
bio->bi_end_io = bio_end_empty_barrier;
bio->bi_bdev = bdev;
if (test_bit(BLKDEV_WAIT, &flags))
bio->bi_private = &wait;
bio_get(bio);
submit_bio(WRITE_BARRIER, bio);
if (test_bit(BLKDEV_WAIT, &flags)) {
wait_for_completion(&wait);
/*
* The driver must store the error location in ->bi_sector, if
* it supports it. For non-stacked drivers, this should be
* copied from blk_rq_pos(rq).
*/
if (error_sector)
*error_sector = bio->bi_sector;
}
if (bio_flagged(bio, BIO_EOPNOTSUPP))
ret = -EOPNOTSUPP;
else if (!bio_flagged(bio, BIO_UPTODATE))
ret = -EIO;
bio_put(bio);
return ret;
}
EXPORT_SYMBOL(blkdev_issue_flush);