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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 042/100] btrfs: fix deadlock when writing out
 space cache
Thread-Topic: [PATCH AUTOSEL for 4.14 042/100] btrfs: fix deadlock when
 writing out space cache
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Date:   Wed, 24 Jan 2018 04:14:45 +0000
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From: Josef Bacik <jbacik@fb.com>

[ Upstream commit b77000ed558daa3bef0899d29bf171b8c9b5e6a8 ]

If we fail to prepare our pages for whatever reason (out of memory in
our case) we need to make sure to drop the block_group->data_rwsem,
otherwise hilarity ensues.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add label and use existing unlocking code ]
Signed-off-by: David Sterba <dsterba@suse.com>

Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 fs/btrfs/free-space-cache.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index cdc9f4015ec3..4426d1c73e50 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1264,7 +1264,7 @@ static int __btrfs_write_out_cache(struct btrfs_root =
*root, struct inode *inode,
 	/* Lock all pages first so we can lock the extent safely. */
 	ret =3D io_ctl_prepare_pages(io_ctl, inode, 0);
 	if (ret)
-		goto out;
+		goto out_unlock;
=20
 	lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
 			 &cached_state);
@@ -1358,6 +1358,7 @@ out_nospc_locked:
 out_nospc:
 	cleanup_write_cache_enospc(inode, io_ctl, &cached_state);
=20
+out_unlock:
 	if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
 		up_write(&block_group->data_rwsem);
=20
--=20
2.11.0