On Tue, Mar 7, 2017 at 5:24 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > > On Mon, Mar 6, 2017 at 3:05 PM, Alexey Gladkov <gladkov.alexey@xxxxxxxxx> wrote: > > > > After discussion with Oleg Nesterov I reimplement my patch as an additional > > option for /proc. This option affects the mountpoint. It means that in one > > pid namespace it possible to have both the whole traditional /proc and > > /proc with only pids subset. > > > > I like this. I think you should split it into two patches, though: > one that reworks how procfs gets mounted and one that makes adds the > new functionality. > > Djajal had some concerns about the first part breaking applications > that use stat and expect certain behavior. This should be manageable, > though, but making stat work appropriately. I'm bit lost in the two discussion, however the main concern I was discussing with Andy was if you have per superblock proc mounts then each mount will end up with its own device ID st_dev, right now they share the same ID if they are in the same pid namespace, but if we change that then we may break the following: http://man7.org/linux/man-pages/man7/namespaces.7.html Both new NS_GET_PARENT and NS_GET_USERNS ioctl() that return an fd, suggests to follow up with fstat() to identify the namespaces.. "By applying fstat(2) to the returned file descriptor, one obtains a stat structure whose st_dev (resident device) and st_ino (inode number) fields together identify the owning/parent namespace." Other /proc/self/ns/* comparison and stat() logic... Andy suggested that we may have the same st_dev for mounts in the same pid namespace... I'm not sure which side effect this may bring! Thanks! -- tixxdz -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
