From f10d9f617a65905c556c3b37c9b9646ae7d04ed7 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 13 Jul 2010 17:50:50 +1000 Subject: [PATCH] blkdev: check for valid request queue before issuing flush Issuing a blkdev_issue_flush() on an unconfigured loop device causes a panic as q->make_request_fn is not configured. This can occur when trying to mount the unconfigured loop device as an XFS filesystem. There are no guards that catch the bio before the request function is called because we don't add a payload to the bio. Instead, manually check this case as soon as we have a pointer to the queue to flush. Signed-off-by: Dave Chinner Signed-off-by: Jens Axboe --- block/blk-barrier.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/block/blk-barrier.c b/block/blk-barrier.c index eefbde835308..557f69360b6a 100644 --- a/block/blk-barrier.c +++ b/block/blk-barrier.c @@ -310,6 +310,15 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, if (!q) return -ENXIO; + /* + * some block devices may not have their queue correctly set up here + * (e.g. loop device without a backing file) and so issuing a flush + * here will panic. Ensure there is a request function before issuing + * the barrier. + */ + if (!q->make_request_fn) + return -ENXIO; + bio = bio_alloc(gfp_mask, 0); bio->bi_end_io = bio_end_empty_barrier; bio->bi_bdev = bdev; -- 2.39.5