On Sat, Jun 02, 2018 at 04:42:56AM +0100, Al Viro wrote: > _If_ I'm interpreting that correctly, that should be something like a bitmap > of attributes to modify + values to set for each. Let's see - > propagation 1 + 2 bits > nodev 1 + 1 > noexec 1 + 1 > nosuid 1 + 1 > ro 1 + 1 > atime 1 + 3 > That's 15 bits. On top of that, we have 1 bit for "clone or original" > and 1 bit for "recursive or single-mount". As well as AT_EMPTY_PATH, > and AT_NO_AUTOMOUNT (inconvenient, since these are fixed bits). In > principle, that does fit into int, with some space to spare... > > Is that what you have in mind? TBH, I would probably prefer separate mount_setattr(2) for that kind of work, with something like int mount_setattr(int dirfd, const char *path, int flags, int attr) *not* opening any files. flags: AT_EMPTY_PATH, AT_NO_AUTOMOUNT, AT_RECURSIVE attr: MOUNT_SETATTR_DEV (1<<0) MOUNT_SETATTR_NODEV (1<<0)|(1<<1) MOUNT_SETATTR_EXEC (1<<2) MOUNT_SETATTR_NOEXEC (1<<2)|(1<<3) MOUNT_SETATTR_SUID (1<<4) MOUNT_SETATTR_NOSUID (1<<4)|(1<<5) MOUNT_SETATTR_RW (1<<6) MOUNT_SETATTR_RO (1<<6)|(1<<7) MOUNT_SETATTR_RELATIME (1<<8) MOUNT_SETATTR_NOATIME (1<<8)|(1<<9) MOUNT_SETATTR_NODIRATIME (1<<8)|(2<<9) MOUNT_SETATTR_STRICTATIME (1<<8)|(3<<9) MOUNT_SETATTR_PRIVATE (1<<11) MOUNT_SETATTR_SHARED (1<<11)|(1<<12) MOUNT_SETATTR_SLAVE (1<<11)|(2<<12) MOUNT_SETATTR_UNBINDABLE (1<<11)|(3<<12) With either openat() used as in this series, or explicit int open_tree(int dirfd, const char *path, int flags) returning a descriptor, with flags being AT_EMPTY_PATH, AT_NO_AUTOMOUNT, AT_RECURSIVE, AT_CLONE with AT_RECURSIVE without AT_CLONE being an error. Hell, might even add AT_UMOUNT for "open root and detach, to be dissolved on close", incompatible with AT_CLONE. Comments?
