From c55f13964008bfea7c5bee268f28b699cbad7f00 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 19 Jun 2014 10:42:54 +0800 Subject: Btrfs: fix deadlock when mounting a degraded fs The deadlock happened when we mount degraded filesystem, the reproduced steps are following: # mkfs.btrfs -f -m raid1 -d raid1 # echo 1 > /sys/block/`basename `/device/delete # mount -o degraded The reason was that the counter -- bi_remaining was wrong. If the missing or unwriteable device was the last device in the mapping array, we would not submit the original bio, so we shouldn't increase bi_remaining of it in btrfs_end_bio(), or we would skip the final endio handle. Fix this problem by adding a flag into btrfs bio structure. If we submit the original bio, we will set the flag, and we increase bi_remaining counter, or we don't. Though there is another way to fix it -- decrease bi_remaining counter of the original bio when we make sure the original bio is not submitted, this method need add more check and is easy to make mistake. Signed-off-by: Miao Xie Reviewed-by: Liu Bo Signed-off-by: Chris Mason --- fs/btrfs/volumes.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs/btrfs/volumes.c') diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 31f9036f3171..4ca3c92a54b3 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5415,8 +5415,12 @@ static void btrfs_end_bio(struct bio *bio, int err) set_bit(BIO_UPTODATE, &bio->bi_flags); err = 0; } + + if (likely(bbio->flags & BTRFS_BIO_ORIG_BIO_SUBMITTED)) + bio_endio_nodec(bio, err); + else + bio_endio(bio, err); kfree(bbio); - bio_endio_nodec(bio, err); } else if (!is_orig_bio) { bio_put(bio); } @@ -5671,6 +5675,7 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio, BUG_ON(!bio); /* -ENOMEM */ } else { bio = first_bio; + bbio->flags |= BTRFS_BIO_ORIG_BIO_SUBMITTED; } submit_stripe_bio(root, bbio, bio, -- cgit v1.2.3