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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, Liu Bo <bo.li.liu@oracle.com>,
        Josef Bacik <jbacik@fb.com>, David Sterba <dsterba@suse.com>
Subject: [PATCH 4.9 18/77] Btrfs: fix deadlock in run_delalloc_nocow
Date:   Wed, 21 Feb 2018 13:48:27 +0100
Message-Id: <20180221124432.950380626@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Liu Bo <bo.li.liu@oracle.com>

commit e89166990f11c3f21e1649d760dd35f9e410321c upstream.

@cur_offset is not set back to what it should be (@cow_start) if
btrfs_next_leaf() returns something wrong, and the range [cow_start,
cur_offset) remains locked forever.

cc: <stable@vger.kernel.org>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/inode.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1320,8 +1320,11 @@ next_slot:
 		leaf = path->nodes[0];
 		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
+			if (ret < 0) {
+				if (cow_start != (u64)-1)
+					cur_offset = cow_start;
 				goto error;
+			}
 			if (ret > 0)
 				break;
 			leaf = path->nodes[0];