On Mon, Mar 15, 2021 at 2:41 PM David Howells <dhowells@xxxxxxxxxx> wrote: > > Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > > > (2) We can use the file position to represent the mnt_id and can jump to > > > it directly - ie. using seek() to jump to a mount object by its ID. > > > > What happens if the mount at the current position is removed? > > umount_tree() requires the namespace_sem to be writelocked, so that should be > fine as the patches currently read-lock that whilst doing /proc/*/mount* > > I'm assuming that kern_unmount() won't be a problem as it is there to deal > with mounts made by kern_mount() which don't get added to the mount list > (mnt_ns is MNT_NS_INTERNAL). kern_unmount_array() seems to be the same > because overlayfs gives it mounts generated by clone_private_mount(). It > might be worth putting a WARN_ON() in kern_unmount() to require this. > > When reading through proc, m_start() calls xas_find() which returns the entry > at the starting index or, if not present, the next higher entry. This will break the property of new mounts always being added to the end of the list. That's likely a regression for nerural based parsers (i.e. people), probably less so for machine parsers. Thanks, Miklos > > David >
