Lockdep complains about lock inversion between ioc->lock and bfqd->lock:
bfqd -> ioc:
put_io_context+0x33/0x90 -> ioc->lock grabbed
blk_mq_free_request+0x51/0x140
blk_put_request+0xe/0x10
blk_attempt_req_merge+0x1d/0x30
elv_attempt_insert_merge+0x56/0xa0
blk_mq_sched_try_insert_merge+0x4b/0x60
bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed
blk_mq_sched_insert_requests+0xd6/0x2b0
blk_mq_flush_plug_list+0x154/0x280
blk_finish_plug+0x40/0x60
ext4_writepages+0x696/0x1320
do_writepages+0x1c/0x80
__filemap_fdatawrite_range+0xd7/0x120
sync_file_range+0xac/0xf0
ioc->bfqd:
bfq_exit_icq+0xa3/0xe0 -> bfqd->lock grabbed
put_io_context_active+0x78/0xb0 -> ioc->lock grabbed
exit_io_context+0x48/0x50
do_exit+0x7e9/0xdd0
do_group_exit+0x54/0xc0
To avoid this inversion we change blk_mq_sched_try_insert_merge() to not
free the merged request but rather leave that upto the caller similarly
to blk_mq_sched_try_merge(). And in bfq_insert_requests() we make sure
to free all the merged requests after dropping bfqd->lock.
Fixes: aee69d78dec0 ("block, bfq: introduce the BFQ-v0 I/O scheduler as an extra scheduler")
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210623093634.27879-3-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(cherry picked from commit fd2ef39cc9a6b9c4c41864ac506906c52f94b06a)
(cherry picked from commit 786e392c4a7bd2559bdc1a1c6ac28d8b612a0735)
(cherry picked from commit aa8e3e1451bde73dff60f1e5110b6a3cb810e35b)
(cherry picked from commit 4deef6abb13a82b148c583d9ab37374c876fe4c2)
(cherry picked from commit 1988f864ec1c494bb54e5b9df1611195f6d923f2)
(cherry picked from commit 9dc0074b0dd8960f9e06dc1494855493ff53eb68)
(cherry picked from commit c937983724111bb4526e34da0d5c6c8aea1902af)
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
(cherry picked from commit 4d3c7baa4acb5fa3b238dde267826254788e86e5)
(cherry picked from commit 6e658026fe20dc1d651c5f4a56afd363a3195f42)
(cherry picked from commit 2ce27817f2fa8e4bbd3420b2f6c050d404703efc)
(cherry picked from commit 85c200268a4bd8b9ad639991bdaf233ba14f6ade)
(cherry picked from commit 35ab17dbef37e36630d542dce420dc3ac6467d74)
(cherry picked from commit 77662095632a51547ca5f921ec453802788d58ee)
(cherry picked from commit 46e2b47e9560de0877079c8a5db0f5ae742133c4)
(cherry picked from commit d12b3702c6e03ac84d399d41e2859b24e8630dea)
(cherry picked from commit 79be04236891dcd6e5e87a25626a64d6d0d0a42f)
(cherry picked from commit c85b5a7d9c215ca4dc35e894149523b33409fd40)
