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| author | Adrian Hunter <adrian.hunter@nokia.com> | 2010-09-25 12:42:55 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2010-09-25 12:42:55 +0200 |
| commit | f281fb5fe54e15a7ab802945e42f8e24fceb56b2 (patch) | |
| tree | 51a7dd2e900b8ce4118d1357ab6e187edfc12e25 /block | |
| parent | a850ea30374ebed32a0724742601861853fde869 (diff) | |
| download | linux-f281fb5fe54e15a7ab802945e42f8e24fceb56b2.tar.gz linux-f281fb5fe54e15a7ab802945e42f8e24fceb56b2.tar.bz2 linux-f281fb5fe54e15a7ab802945e42f8e24fceb56b2.zip | |
block: prevent merges of discard and write requests
Add logic to prevent two I/O requests being merged if
only one of them is a discard. Ditto secure discard.
Without this fix, it is possible for write requests
to transform into discard requests. For example:
Submit bio 1 to discard 8 sectors from sector n
Submit bio 2 to write 8 sectors from sector n + 16
Submit bio 3 to write 8 sectors from sector n + 8
Bio 1 becomes request 1. Bio 2 becomes request 2.
Bio 3 is merged with request 2, and then subsequently
request 2 is merged with request 1 resulting in just
one I/O request which discards all 24 sectors.
Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
(Moved the checks above the position checks /Jens)
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-merge.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c index 3b0cd4249671..eafc94f68d79 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -362,6 +362,18 @@ static int attempt_merge(struct request_queue *q, struct request *req, return 0; /* + * Don't merge file system requests and discard requests + */ + if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD)) + return 0; + + /* + * Don't merge discard requests and secure discard requests + */ + if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE)) + return 0; + + /* * not contiguous */ if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) |