From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:23136 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757902AbaFSJPp (ORCPT ); Thu, 19 Jun 2014 05:15:45 -0400 Date: Thu, 19 Jun 2014 17:15:34 +0800 From: Liu Bo To: Miao Xie Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 6/7] Btrfs: fix deadlock when mounting a degraded fs Message-ID: <20140619091533.GB16468@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <1403145775-22641-1-git-send-email-miaox@cn.fujitsu.com> <1403145775-22641-7-git-send-email-miaox@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1403145775-22641-7-git-send-email-miaox@cn.fujitsu.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Thu, Jun 19, 2014 at 10:42:54AM +0800, Miao Xie wrote: > 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. Happen to look at this problem, looks good to me. Reviewed-by: Liu Bo -liubo > > 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html