On Fri, Mar 16, 2012 at 03:32:15PM +0800, Shaohua Li wrote: > Didn't allow discard request merge temporarily, as SCSI layer isn't ready > for discard merge as Martin Petersen pointed out. This isn't fair for > non-scsi device, but looks this is the only way I can do currently. > > We should have the same issue before, but maybe because discard merge is > very rare case. But now raid0/10 makes the merge quite possible, so we need > disable it explicitly. > > Signed-off-by: Shaohua Li <shli@xxxxxxxxxxxx> > --- > include/linux/blkdev.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: linux/include/linux/blkdev.h > =================================================================== > --- linux.orig/include/linux/blkdev.h 2012-03-14 09:20:06.787261188 +0800 > +++ linux/include/linux/blkdev.h 2012-03-14 09:20:47.797261248 +0800 > @@ -575,7 +575,7 @@ static inline void blk_clear_queue_full( > * it already be started by driver. > */ > #define RQ_NOMERGE_FLAGS \ > - (REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA) > + (REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA | REQ_DISCARD) > #define rq_mergeable(rq) \ > (!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \ > (((rq)->cmd_flags & REQ_DISCARD) || \ I think you will need to do little more cleanup to make discard unmergeable. - Change rq_mergeable(rq) - Change attempt_merge() and get rid of special conditions of allowing discard merge. Martin had a bigger patch where he wanted to cleanup many discard specific condition checks. As you are just focusing on disabling merging for discard requests, you might as well just pick the relevant pieces from the patch. http://www.spinics.net/lists/linux-scsi/msg57779.html Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
