From: Ming Lei
mainline inclusion
from mainline-5.11-rc1
commit 88c9979334aa5ff8c814ddf578f3113ed6c5ce8e
category: bugfix
issue: #I3ZXZF
CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
---------------------------
Set nvme-loop's lock class via blk_mq_hctx_set_fq_lock_class for avoiding
lockdep possible recursive locking, then we can remove the dynamically
allocated lock class for each flush queue, finally we can avoid horrible
SCSI probe delay.
This way may not address situation in which one nvme-loop is backed on
another nvme-loop. However, in reality, people seldom uses this way
for test. Even though someone played in this way, it is just one
recursive locking false positive, no real deadlock issue.
Tested-by: Kashyap Desai
Reported-by: Qian Cai
Reviewed-by: Christoph Hellwig
Cc: Sumit Saxena
Cc: John Garry
Cc: Kashyap Desai
Cc: Bart Van Assche
Cc: Hannes Reinecke
Signed-off-by: Ming Lei
Reviewed-by: Hannes Reinecke
Signed-off-by: Jens Axboe
Signed-off-by: yangerkun
Reviewed-by: Jason Yan
Signed-off-by: Chen Jun
Signed-off-by: Yu Changchun
---
drivers/nvme/target/loop.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/nvme/target/loop.c b/drivers/nvme/target/loop.c
index 16d71cc5a50e..06b940d71dc6 100644
--- a/drivers/nvme/target/loop.c
+++ b/drivers/nvme/target/loop.c
@@ -211,6 +211,8 @@ static int nvme_loop_init_request(struct blk_mq_tag_set *set,
(set == &ctrl->tag_set) ? hctx_idx + 1 : 0);
}
+static struct lock_class_key loop_hctx_fq_lock_key;
+
static int nvme_loop_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
unsigned int hctx_idx)
{
@@ -219,6 +221,14 @@ static int nvme_loop_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
BUG_ON(hctx_idx >= ctrl->ctrl.queue_count);
+ /*
+ * flush_end_io() can be called recursively for us, so use our own
+ * lock class key for avoiding lockdep possible recursive locking,
+ * then we can remove the dynamically allocated lock class for each
+ * flush queue, that way may cause horrible boot delay.
+ */
+ blk_mq_hctx_set_fq_lock_class(hctx, &loop_hctx_fq_lock_key);
+
hctx->driver_data = queue;
return 0;
}
--
2.22.0
