On Feb 10, 2014, at 21:30, NeilBrown <neilb@xxxxxxx> wrote: > > (I seem to have quite a pile of NFS issues lately.... some if it is tidying up > issues from before Christmas, some of it just keeps on coming :-) > > If you run "mount -a" it will attempt to mount all filesystems listed > in /etc/fstab, but filesystems that are already mounted will not be mounted > again. So it is normally safe to run "mount -a" multiple times. > > However if an NFS mount in /etc/fstab has the "nosharecache" option set, > mount doesn't notice that it is already mounted as so mounts it again. So > repeated "mount -a" is no longer safe. > > This happens because the prevention of multiple mounts happens in do_add_mount > in fs/namespace.c: > > err = -EBUSY; > if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && > path->mnt->mnt_root == path->dentry) > goto unlock; > > > i.e. if the exact same superblock is being mounted in the exact same place, > return EBUSY. > With nosharecache, every mount attempt produces a new superblock so this test > never fires. > > One way to address this would be to have a different option, e.g. > sharecache=27 > > where the '27' is an arbitrary number meaning that if two mount attempts have > different sharecache numbers they will have different superblocks. If they > have the same sharecache number they can have the same superblock. > This is not the most elegant interface ever and I would be very happy for > suggestions to improve it. Maybe a string rather than a number ??? > > This probably isn't a very serious issue, but is a regression in terms of the > usability of "mount -a" and I think it would be best to fix it if the cost is > not too high. > > Below is my patch to implement the "sharecache=%u" syntax. > > Any ideas? What are people using nosharecache for these days, and why is this not another argument for just getting rid of it? _________________________________ Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
