2015-03-28 0:42 GMT+03:00 Richard Weinberger <richard.weinberger@xxxxxxxxx>: > On Fri, Mar 27, 2015 at 9:39 PM, Andrey Vagin <avagin@xxxxxxxxxx> wrote: >> I don't see any reasons to hide them. This information can help to >> understand errors. > > Because these flags are set/read only internally by the VFS. In contrast > to the other flags shown by mountinfo MNT_LOCKED is not a mount option. But this flag is set as a result of the specified user action, when he unshares userns and mntns. This flag affects visiable behaviour. > > Why does it help to debug errors? > How would a user know that mount() with MS_BIND returns EINVAL because > the mount source is MNT_LOCKED? This information is useless for her. If I see lock_ro, I can be sure that mount -o remount,bind,rw /XXX will fail. If I see locked, I know that this mount can't be umounted or moved and can be bind-mounted only recursively. If a user see these flags, he can check that a mount namespace is configured correctly without security issues. Sorry but I don't understand why you think that this information is useless for users. > If you argue like that you'd have to expose the whole VFS state to userland. I have not noticed other MNT_LOCK_* flags. I should think more about what information are a really required for dumping mount namespaces. > >> And this information is required for correct checkpoint/restore of mount >> namespaces. > > Why especially MNT_LOCKED and not all the other flags used by VFS? My goal is to dump enough information about a mount namespace to be able to restore it back later. I don't know how to do this without knowledge about locked mounts. I will think. > Say MNT_DOOMED? Mounts with MNT_DOOMED are never shown in mountinfo, are they? Thank you for looking at this patch. > > -- > Thanks, > //richard -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
