Btrfs: find_free_dev_extent doesn't handle holes at the start of the device

find_free_dev_extent does not properly handle the case where
the device is not complete free, and there is a free extent
at the beginning of the device.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 55c37276a29f..074c1c56d8c4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -758,9 +758,13 @@ static noinline int find_free_dev_extent(struct btrfs_trans_handle *trans,
         ret = btrfs_search_slot(trans, root, &key, path, 0, 0);
         if (ret < 0)
                 goto error;
-        ret = btrfs_previous_item(root, path, 0, key.type);
-        if (ret < 0)
-                goto error;
+        if (ret > 0) {
+                ret = btrfs_previous_item(root, path, key.objectid, key.type);
+                if (ret < 0)
+                        goto error;
+                if (ret > 0)
+                        start_found = 1;
+        }
         l = path->nodes[0];
         btrfs_item_key_to_cpu(l, &key, path->slots[0]);
         while (1) {