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authorMing Lei <ming.lei@redhat.com>2018-11-14 11:25:51 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-11-21 11:19:18 +0300
commit410306a0f2baa5d68970cdcf6763d79c16df5f23 (patch)
tree5d527688a386d671d7ffb6ad0e31ead1fb0b8c24 /block
parentdd2fb8c67d81af9e27210e3196e8f24b3e016637 (diff)
downloadlinux-410306a0f2baa5d68970cdcf6763d79c16df5f23.tar.xz
SCSI: fix queue cleanup race before queue initialization is done
commit 8dc765d438f1e42b3e8227b3b09fad7d73f4ec9a upstream. c2856ae2f315d ("blk-mq: quiesce queue before freeing queue") has already fixed this race, however the implied synchronize_rcu() in blk_mq_quiesce_queue() can slow down LUN probe a lot, so caused performance regression. Then 1311326cf4755c7 ("blk-mq: avoid to synchronize rcu inside blk_cleanup_queue()") tried to quiesce queue for avoiding unnecessary synchronize_rcu() only when queue initialization is done, because it is usual to see lots of inexistent LUNs which need to be probed. However, turns out it isn't safe to quiesce queue only when queue initialization is done. Because when one SCSI command is completed, the user of sending command can be waken up immediately, then the scsi device may be removed, meantime the run queue in scsi_end_request() is still in-progress, so kernel panic can be caused. In Red Hat QE lab, there are several reports about this kind of kernel panic triggered during kernel booting. This patch tries to address the issue by grabing one queue usage counter during freeing one request and the following run queue. Fixes: 1311326cf4755c7 ("blk-mq: avoid to synchronize rcu inside blk_cleanup_queue()") Cc: Andrew Jones <drjones@redhat.com> Cc: Bart Van Assche <bart.vanassche@wdc.com> Cc: linux-scsi@vger.kernel.org Cc: Martin K. Petersen <martin.petersen@oracle.com> Cc: Christoph Hellwig <hch@lst.de> Cc: James E.J. Bottomley <jejb@linux.vnet.ibm.com> Cc: stable <stable@vger.kernel.org> Cc: jianchao.wang <jianchao.w.wang@oracle.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block')
-rw-r--r--block/blk-core.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index cff0a60ee200..eb8b52241453 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -793,9 +793,8 @@ void blk_cleanup_queue(struct request_queue *q)
* dispatch may still be in-progress since we dispatch requests
* from more than one contexts.
*
- * No need to quiesce queue if it isn't initialized yet since
- * blk_freeze_queue() should be enough for cases of passthrough
- * request.
+ * We rely on driver to deal with the race in case that queue
+ * initialization isn't done.
*/
if (q->mq_ops && blk_queue_init_done(q))
blk_mq_quiesce_queue(q);