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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Josef Bacik <jbacik@fb.com>,
        Omar Sandoval <osandov@fb.com>, Liu Bo <bo.li.liu@oracle.com>,
        David Sterba <dsterba@suse.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 34/86] btrfs: fix deadlock when writing out space cache
Date:   Fri,  2 Feb 2018 17:57:54 +0100
Message-Id: <20180202140825.686102707@linuxfoundation.org>
In-Reply-To: <20180202140822.679101338@linuxfoundation.org>
References: <20180202140822.679101338@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/btrfs/free-space-cache.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1253,7 +1253,7 @@ static int __btrfs_write_out_cache(struc
 	/* Lock all pages first so we can lock the extent safely. */
 	ret = io_ctl_prepare_pages(io_ctl, inode, 0);
 	if (ret)
-		goto out;
+		goto out_unlock;
 
 	lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
 			 &cached_state);
@@ -1346,6 +1346,7 @@ out_nospc_locked:
 out_nospc:
 	cleanup_write_cache_enospc(inode, io_ctl, &cached_state, &bitmap_list);
 
+out_unlock:
 	if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
 		up_write(&block_group->data_rwsem);