719d34027e
The logic in cfq_allow_merge() wasn't clear enough - basically allow merging for the same queues only. Do a fast check for 'rq and bio both sync/async' before doing the cfqq hash lookup. This is verified to work with the fixed elv_try_merge() from commit bb4067e34159648d394943d5e2a011f838bff22f. Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>