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authorJan Kara <jack@suse.cz>2021-06-23 12:36:34 +0300
committerJens Axboe <axboe@kernel.dk>2021-06-25 03:43:55 +0300
commitfd2ef39cc9a6b9c4c41864ac506906c52f94b06a (patch)
tree0d9ad0660f5947bccc862825bcdaf9f3bfd20789 /block/blk-merge.c
parenta921c655f2033dd1ce1379128efe881dda23ea37 (diff)
downloadlinux-fd2ef39cc9a6b9c4c41864ac506906c52f94b06a.tar.xz
blk: Fix lock inversion between ioc lock and bfqd lock
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>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c19
1 files changed, 8 insertions, 11 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 4d97fb6dd226..1398b52a24b4 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -846,18 +846,15 @@ static struct request *attempt_front_merge(struct request_queue *q,
return NULL;
}
-int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
- struct request *next)
+/*
+ * Try to merge 'next' into 'rq'. Return true if the merge happened, false
+ * otherwise. The caller is responsible for freeing 'next' if the merge
+ * happened.
+ */
+bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
+ struct request *next)
{
- struct request *free;
-
- free = attempt_merge(q, rq, next);
- if (free) {
- blk_put_request(free);
- return 1;
- }
-
- return 0;
+ return attempt_merge(q, rq, next);
}
bool blk_rq_merge_ok(struct request *rq, struct bio *bio)