block: deal with stale req count of plug list
authorMing Lei <ming.lei@canonical.com>
Wed, 16 Nov 2016 10:07:05 +0000 (18:07 +0800)
committerJens Axboe <axboe@fb.com>
Wed, 16 Nov 2016 15:09:51 +0000 (08:09 -0700)
commit0a6219a95f0b0690fb7094acb26002e7a4791197
treef965302c4a95854447b360d0d6c41dabfc28171e
parent2868f13c303e1472bfd3941c62916c1f4128a713
block: deal with stale req count of plug list

In both legacy and mq path, req count of plug list is computed
before allocating request, so the number can be stale when falling
back to slept allocation, also the new introduced wbt can sleep
too.

This patch deals with the case by checking if plug list becomes
empty, and fixes the KASAN report of 'BUG: KASAN: stack-out-of-bounds'
which is introduced by Shaohua's patches of dispatching big request.

Fixes: 600271d900002(blk-mq: immediately dispatch big size request)
Fixes: 50d24c34403c6(block: immediately dispatch big size request)
Cc: Shaohua Li <shli@fb.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
block/blk-core.c
block/blk-mq.c