Hi! Linux kernel currently does not provide any race-free way for calling unlink() syscall on file entry which points to opened file descriptor. On the other hand Linux kernel already provides race-free way for creating file entry by linkat() syscall with AT_EMPTY_PATH or AT_SYMLINK_FOLLOW flags. unlinkat() does not. There was already discussion about unlink issue in bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=93441 Because file descriptor describes inode number which can be stored in more directories as hard links, there is a proposed funlinkat() syscall with following API: int funlinkat(int fd, int dirfd, const char *pathname, int flags); It should atomically check if file descriptor fd and pathname (according to dirfd) are same, and if then just unlinkat(dirfd, pathname, flags). If are not same, throw error. What userspace application basically needs: Open file, test it stat (or probably content) and based on test result decide if file needs to be removed or not. Or delete a file behind a file descriptor opened with O_PATH. Both cases are currently not possible without introducing race condition between open/stat and unlink. Between those two calls, some other process can exchange files. -- Pali Rohár pali.rohar@xxxxxxxxx
