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authorAdrian Hunter <adrian.hunter@nokia.com>2010-09-25 12:42:55 +0200
committerJens Axboe <jaxboe@fusionio.com>2010-09-25 12:42:55 +0200
commitf281fb5fe54e15a7ab802945e42f8e24fceb56b2 (patch)
tree51a7dd2e900b8ce4118d1357ab6e187edfc12e25 /block/blk-merge.c
parenta850ea30374ebed32a0724742601861853fde869 (diff)
downloadlinux-linaro-stable-f281fb5fe54e15a7ab802945e42f8e24fceb56b2.tar.gz
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/blk-merge.c')
-rw-r--r--block/blk-merge.c12
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))