Btrfs: fix extent buffer reference for tree mod log roots

In get_old_root we grab a lock on the extent buffer before we obtain a
reference on that buffer. That order is changed now.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index ef68c33..f673990 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1279,6 +1279,7 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
 
        if (!eb)
                return NULL;
+       extent_buffer_get(eb);
        btrfs_tree_read_lock(eb);
        if (old_root) {
                btrfs_set_header_bytenr(eb, eb->start);
@@ -1291,7 +1292,6 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
                __tree_mod_log_rewind(eb, time_seq, tm);
        else
                WARN_ON(btrfs_header_level(eb) != 0);
-       extent_buffer_get(eb);
        WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(root));
 
        return eb;