Btrfs: Fix deadlock while searching for dead roots on mount

btrfs_find_dead_roots called btrfs_read_fs_root_no_radix, which
means we end up calling btrfs_search_slot with a path already held.

The fix is to remember the key inside btrfs_find_dead_roots and drop
the path.

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

1 files changed, 9 insertions, 1 deletions

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 8bf21ba0a43b..a5c0e98b5aeb 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -154,6 +154,7 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid,
         struct btrfs_item *item;
         struct btrfs_root_item *ri;
         struct btrfs_key key;
+        struct btrfs_key found_key;
         struct btrfs_path *path;
         int ret;
         u32 nritems;
@@ -166,6 +167,8 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid,
         path = btrfs_alloc_path();
         if (!path)
                 return -ENOMEM;
+
+again:
         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
         if (ret < 0)
                 goto err;
@@ -196,7 +199,11 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid,
                 if (btrfs_disk_root_refs(leaf, ri) != 0)
                         goto next;
 
-                dead_root = btrfs_read_fs_root_no_radix(root->fs_info, &key);
+                memcpy(&found_key, &key, sizeof(key));
+                key.offset++;
+                btrfs_release_path(root, path);
+                dead_root = btrfs_read_fs_root_no_radix(root->fs_info,
+                                                        &found_key);
                 if (IS_ERR(dead_root)) {
                         ret = PTR_ERR(dead_root);
                         goto err;
@@ -206,6 +213,7 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid,
                                           &root->fs_info->dead_roots);
                 if (ret)
                         goto err;
+                goto again;
 next:
                 slot++;
                 path->slots[0]++;