On Thu, 20 Feb 2020, Patrick Steinhardt wrote:
> On Thu, Feb 20, 2020 at 08:06:20AM -0500, Scott Mayhew wrote:
> > Hard-coding the fstype causes "nfs4" mounts to appear as "nfs",
> > which breaks scripts that do "umount -at nfs4".
> >
> > Reported-by: Patrick Steinhardt <ps@xxxxxx>
> > Fixes: f2aedb713c28 ("NFS: Add fs_context support.")
> > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
> > ---
> > fs/nfs/namespace.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
> > index ad6077404947..f3ece8ed3203 100644
> > --- a/fs/nfs/namespace.c
> > +++ b/fs/nfs/namespace.c
> > @@ -153,7 +153,7 @@ struct vfsmount *nfs_d_automount(struct path *path)
> > /* Open a new filesystem context, transferring parameters from the
> > * parent superblock, including the network namespace.
> > */
> > - fc = fs_context_for_submount(&nfs_fs_type, path->dentry);
> > + fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
> > if (IS_ERR(fc))
> > return ERR_CAST(fc);
>
> Thanks for your fix! While this fixes the fstype with mount.nfs4(8),
> it still doesn't work when using mount(8):
>
> $ sudo mount server:/mnt /mnt && findmnt -n -ofstype /mnt
> nfs
> $ sudo umount /mnt
> $ sudo mount.nfs4 server:/mnt /mnt && findmnt -n -ofstype /mnt
> nfs4
>
> I guess the issue is that the kernel doesn't yet know which NFS version
> the server provides at the point where `fs_context_for_submount()` is
> called.
Thanks for testing. Actually the problem is that the super_block's
s_type is now based on the fs_context->fs_type field, which is set when
the fs_context is created (way before the mount options are parsed).
When you use mount(8) without specifying '-t nfs4', it defaults to
using the mount.nfs helper, which calls mount(2) with 'nfs' as the
fstype. I'm sending a second patch that double-checks the
fs_context->fs_type after the mount options have been parsed. We still
shouldn't be hard-coding the fstype in fs_context_for_submount() though
(i.e. both patches are needed).
-Scott
>
> Patrick
