Hello, this patch set fixes a problem with cross directory renames originally reported in [1]. To quickly sum it up some filesystems (so far we know at least about ext4, udf, f2fs, ocfs2, likely also reiserfs, gfs2 and others) need to lock the directory when it is being renamed into another directory. This is because we need to update the parent pointer in the directory in that case and if that races with other operation on the directory (in particular a conversion from one directory format into another), bad things can happen. So far we've done the locking in the filesystem code but recently Darrick pointed out [2] that we've missed the RENAME_EXCHANGE case in our ext4 fix. That one is particularly nasty because RENAME_EXCHANGE can arbitrarily mix regular files and directories and proper lock ordering is not achievable in the filesystems alone. This patch set adds locking into vfs_rename() so that not only parent directories but also moved inodes (regardless whether they are directories or not) are locked when calling into the filesystem. Honza [1] https://lore.kernel.org/all/20230117123735.un7wbamlbdihninm@quack3 [2] https://lore.kernel.org/all/20230517045836.GA11594@frogsfrogsfrogs
