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authorJens Axboe <axboe@fb.com>2017-01-26 22:50:36 +0300
committerJens Axboe <axboe@fb.com>2017-01-27 18:20:31 +0300
commit3c782d67c16889d753a79a8da5422c583d7cfd51 (patch)
treea34fce71ed855738dd53b3e66594446a23df7319
parent0abad774124351ba211b9053786ebd5a5a722d53 (diff)
downloadlinux-3c782d67c16889d753a79a8da5422c583d7cfd51.tar.xz
blk-mq: fix potential race in queue restart and driver tag allocation
Once we mark the queue as needing a restart, re-check if we can get a driver tag. This fixes a theoretical issue where the needed IO completes _after_ blk_mq_get_driver_tag() fails, but before we manage to set the restart bit. Signed-off-by: Jens Axboe <axboe@fb.com> Reviewed-by: Omar Sandoval <osandov@fb.com> Tested-by: Hannes Reinecke <hare@suse.com>
-rw-r--r--block/blk-mq.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1f948d5c2715..fd80101c7591 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -928,8 +928,16 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list)
if (!blk_mq_get_driver_tag(rq, &hctx, false)) {
if (!queued && reorder_tags_to_front(list))
continue;
+
+ /*
+ * We failed getting a driver tag. Mark the queue(s)
+ * as needing a restart. Retry getting a tag again,
+ * in case the needed IO completed right before we
+ * marked the queue as needing a restart.
+ */
blk_mq_sched_mark_restart(hctx);
- break;
+ if (!blk_mq_get_driver_tag(rq, &hctx, false))
+ break;
}
list_del_init(&rq->queuelist);