Btrfs: don't treat top/root directory inode as deleted/reused

We can't do the deleted/reused logic for top/root inodes as it would
create a stream that tries to delete and recreate the root dir.

Reported-by: Alex Lyakas <alex.bolshoy.btrfs@gmail.com>
Signed-off-by: Alexander Block <ablock84@googlemail.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index a4011a9148fd..d17d75ebc482 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2627,6 +2627,12 @@ static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 send_progress)
         struct btrfs_key loc;
         struct btrfs_dir_item *di;
 
+        /*
+         * Don't try to rmdir the top/root subvolume dir.
+         */
+        if (dir == BTRFS_FIRST_FREE_OBJECTID)
+                return 0;
+
         path = alloc_path_for_send();
         if (!path)
                 return -ENOMEM;
@@ -2687,6 +2693,12 @@ static int process_recorded_refs(struct send_ctx *sctx)
 
 verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
 
+        /*
+         * This should never happen as the root dir always has the same ref
+         * which is always '..'
+         */
+        BUG_ON(sctx->cur_ino <= BTRFS_FIRST_FREE_OBJECTID);
+
         valid_path = fs_path_alloc(sctx);
         if (!valid_path) {
                 ret = -ENOMEM;
@@ -4094,7 +4106,14 @@ static int changed_inode(struct send_ctx *sctx,
 
                 right_gen = btrfs_inode_generation(sctx->right_path->nodes[0],
                                 right_ii);
-                if (left_gen != right_gen)
+
+                /*
+                 * The cur_ino = root dir case is special here. We can't treat
+                 * the inode as deleted+reused because it would generate a
+                 * stream that tries to delete/mkdir the root dir.
+                 */
+                if (left_gen != right_gen &&
+                    sctx->cur_ino != BTRFS_FIRST_FREE_OBJECTID)
                         sctx->cur_inode_new_gen = 1;
         }