Hi! I would like to remind this my older email about race free unlinking. Is there any plan to provide such support? On Wednesday 20 December 2017 20:18:44 Pali Rohár wrote: > 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
