From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:39842 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756081AbaFSCl0 (ORCPT ); Wed, 18 Jun 2014 22:41:26 -0400 Received: from G08CNEXCHPEKD01.g08.fujitsu.local (localhost.localdomain [127.0.0.1]) by edo.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id s5J2fOaT024076 for ; Thu, 19 Jun 2014 10:41:24 +0800 From: Miao Xie To: Subject: [PATCH 6/7] Btrfs: fix deadlock when mounting a degraded fs Date: Thu, 19 Jun 2014 10:42:54 +0800 Message-ID: <1403145775-22641-7-git-send-email-miaox@cn.fujitsu.com> In-Reply-To: <1403145775-22641-1-git-send-email-miaox@cn.fujitsu.com> References: <1403145775-22641-1-git-send-email-miaox@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-btrfs-owner@vger.kernel.org List-ID: 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 --- fs/btrfs/volumes.c | 7 ++++++- fs/btrfs/volumes.h | 3 +++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 31f9036..4ca3c92 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, diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 1a15bbe..2aaa00c 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -190,11 +190,14 @@ struct btrfs_bio_stripe { struct btrfs_bio; typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err); +#define BTRFS_BIO_ORIG_BIO_SUBMITTED 0x1 + struct btrfs_bio { atomic_t stripes_pending; struct btrfs_fs_info *fs_info; bio_end_io_t *end_io; struct bio *orig_bio; + unsigned long flags; void *private; atomic_t error; int max_errors; -- 1.9.3