Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > 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 I would call these MOUNT_SETATTR_* rather than AT_*. > 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) So, I like this generally, some notes though: I wonder if this should be two separate parameters, a mask and the settings? I'm not sure that's worth it since some of the mask bits would cover multiple settings. Also, should NODIRATIME be separate from the other *ATIME flags? I do also like treating some of these settings as enumerations rather than a set of bits. I would make the prototype: int mount_setattr(int dirfd, const char *path, unsigned int flags, unsigned int attr, void *reserved5); Further, do we want to say you can either change the propagation type *or* reconfigure the mountpoint restrictions, but not both at the same time? > With either openat() used as in this series, or explicit > int open_tree(int dirfd, const char *path, int flags) Maybe open_mount(), grab_mount() or pick_mount()? I wonder if fsopen()/fspick() should be create_fs()/open_fs()... > 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. You also need an O_CLOEXEC equivalent. I would make it: OPEN_TREE_CLOEXEC 0x00000001 OPEN_TREE_EMPTY_PATH 0x00000002 OPEN_TREE_FOLLOW_SYMLINK 0x00000004 OPEN_TREE_NO_AUTOMOUNT 0x00000008 OPEN_TREE_CLONE 0x00000010 OPEN_TREE_RECURSIVE 0x00000020 adding the follow-symlinks so that you don't grab a symlink target by accident. (Can you actually mount on top of a symlink?) > Hell, might even add AT_UMOUNT for "open root and detach, to be dissolved on > close", incompatible with AT_CLONE. Cute. Guess you could do: fd = open_mount(..., OPEN_TREE_DETACH); mount_setattr(fd, "", MOUNT_SETATTR_EMPTY_PATH, MOUNT_SETATTR_NOSUID, NULL); move_mount(fd, "", ...); David
