brain-hackers_pepepper-mirror/linux-brain
1
0
Fork 0
mirror of https://github.com/brain-hackers/linux-brain.git synced 2024-06-09 15:26:21 +09:00
Code Issues Projects Releases Wiki Activity

block: flush: fix IO hang in case of flood fua req

Browse Source 
This patch fixes one issue reported by Kent, which can
be triggered in bcachefs over sata disk. Actually it
is a generic issue in block flush vs. blk-tag.

Cc: Christoph Hellwig <hch@infradead.org>
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Ming Lei 2016-10-26 16:57:15 +08:00 committed by Jens Axboe
parent 423221d174
commit 94d7dea448
1 changed files with 28 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
block/blk-flush.c
View File

@ -342,6 +342,34 @@ static void flush_data_end_io(struct request *rq, int error)
struct request_queue *q = rq->q;
struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
/*
* Updating q->in_flight[] here for making this tag usable
* early. Because in blk_queue_start_tag(),
* q->in_flight[BLK_RW_ASYNC] is used to limit async I/O and
* reserve tags for sync I/O.
*
* More importantly this way can avoid the following I/O
* deadlock:
*
* - suppose there are 40 fua requests comming to flush queue
* and queue depth is 31
* - 30 rqs are scheduled then blk_queue_start_tag() can't alloc
* tag for async I/O any more
* - all the 30 rqs are completed before FLUSH_PENDING_TIMEOUT
* and flush_data_end_io() is called
* - the other rqs still can't go ahead if not updating
* q->in_flight[BLK_RW_ASYNC] here, meantime these rqs
* are held in flush data queue and make no progress of
* handling post flush rq
* - only after the post flush rq is handled, all these rqs
* can be completed
*/
elv_completed_request(q, rq);
/* for avoiding double accounting */
rq->cmd_flags &= ~REQ_STARTED;
/*
* After populating an empty queue, kick it to avoid stall. Read
* the comment in flush_end_io().