ufs: do not treat unreadable directory blocks as empty

ufs_empty_dir() scans every directory block to decide whether a
directory is empty before rmdir() removes it. When ufs_get_folio()
cannot read or validate a block it returns an error pointer, and the
loop currently skips that block with continue and keeps scanning the
remaining blocks.

If none of the readable blocks hold an entry, the function returns 1
and the caller unlinks the directory. A directory whose contents live
in a block that cannot be read, for example because of an I/O error or
corrupted directory metadata, is therefore seen as empty and removed,
losing the entries it still holds.

Follow the ext2 behaviour and treat an unreadable block as a reason to
consider the directory not empty, so rmdir() fails instead of
discarding data that could not be verified.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Link: https://patch.msgid.link/20260801013942.279992-1-ali@iusegentoo.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

fs/ufs/dir.c

@@ -590,7 +590,7 @@ int ufs_empty_dir(struct inode * inode)
 
 		kaddr = ufs_get_folio(inode, i, &folio);
 		if (IS_ERR(kaddr))
-			continue;
+			return 0;
 
 		de = (struct ufs_dir_entry *)kaddr;
 		kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);