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/volumes.c b/fs/btrfs/volumes.c
index a79b3cc09e94..825364fae690 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2594,12 +2594,15 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
                         stripe_nr = stripe_nr * map->num_stripes + i;
                 }
                 bytenr = chunk_start + stripe_nr * map->stripe_len;
+                WARN_ON(nr >= map->num_stripes);
                 for (j = 0; j < nr; j++) {
                         if (buf[j] == bytenr)
                                 break;
                 }
-                if (j == nr)
+                if (j == nr) {
+                        WARN_ON(nr >= map->num_stripes);
                         buf[nr++] = bytenr;
+                }
         }
 
         for (i = 0; i > nr; i++) {