Btrfs: Use map_private_extent_buffer during generic_bin_search

It is possible that generic_bin_search will be called on a tree block
that has not been locked.  This happens because cache_block_block skips
locking on the tree blocks.

Since the tree block isn't locked, we aren't allowed to change
the extent_buffer->map_token field.  Using map_private_extent_buffer
avoids any changes to the internal extent buffer fields.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a83cbdf1d8c4..19c0dd33b1e8 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -813,7 +813,8 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
                                 unmap_extent_buffer(eb, map_token, KM_USER0);
                                 map_token = NULL;
                         }
-                        err = map_extent_buffer(eb, offset,
+
+                        err = map_private_extent_buffer(eb, offset,
                                                 sizeof(struct btrfs_disk_key),
                                                 &map_token, &kaddr,
                                                 &map_start, &map_len, KM_USER0);
@@ -3585,6 +3586,7 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
         int level;
         int ret = 1;
 
+        WARN_ON(!path->keep_locks);
 again:
         cur = btrfs_lock_root_node(root);
         level = btrfs_header_level(cur);
@@ -3708,6 +3710,7 @@ int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
         int slot;
         struct extent_buffer *c;
 
+        WARN_ON(!path->keep_locks);
         while(level < BTRFS_MAX_LEVEL) {
                 if (!path->nodes[level])
                         return 1;