On Mon, 2022-12-12 at 05:34 -0800, dai.ngo@xxxxxxxxxx wrote:
> On 12/12/22 4:22 AM, Jeff Layton wrote:
> > On Sun, 2022-12-11 at 11:22 -0800, Dai Ngo wrote:
> > > Problem caused by source's vfsmount being unmounted but remains
> > > on the delayed unmount list. This happens when nfs42_ssc_open()
> > > return errors.
> > > Fixed by removing nfsd4_interssc_connect(), leave the vfsmount
> > > for the laundromat to unmount when idle time expires.
> > >
> > > Reported-by: Xingyuan Mo <hdthky0@xxxxxxxxx>
> > > Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
> > > ---
> > > fs/nfsd/nfs4proc.c | 23 +++++++----------------
> > > 1 file changed, 7 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > > index 8beb2bc4c328..756e42cf0d01 100644
> > > --- a/fs/nfsd/nfs4proc.c
> > > +++ b/fs/nfsd/nfs4proc.c
> > > @@ -1463,13 +1463,6 @@ nfsd4_interssc_connect(struct nl4_server *nss, struct svc_rqst *rqstp,
> > > return status;
> > > }
> > >
> > > -static void
> > > -nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
> > > -{
> > > - nfs_do_sb_deactive(ss_mnt->mnt_sb);
> > > - mntput(ss_mnt);
> > > -}
> > > -
> > > /*
> > > * Verify COPY destination stateid.
> > > *
> > > @@ -1572,11 +1565,6 @@ nfsd4_cleanup_inter_ssc(struct vfsmount *ss_mnt, struct file *filp,
> > > {
> > > }
> > >
> > > -static void
> > > -nfsd4_interssc_disconnect(struct vfsmount *ss_mnt)
> > > -{
> > > -}
> > > -
> > > static struct file *nfs42_ssc_open(struct vfsmount *ss_mnt,
> > > struct nfs_fh *src_fh,
> > > nfs4_stateid *stateid)
> > > @@ -1762,7 +1750,8 @@ static int nfsd4_do_async_copy(void *data)
> > > struct file *filp;
> > >
> > > filp = nfs42_ssc_open(copy->ss_mnt, ©->c_fh,
> > > - ©->stateid);
> > > + ©->stateid);
> > > +
> > > if (IS_ERR(filp)) {
> > > switch (PTR_ERR(filp)) {
> > > case -EBADF:
> > > @@ -1771,7 +1760,7 @@ static int nfsd4_do_async_copy(void *data)
> > > default:
> > > nfserr = nfserr_offload_denied;
> > > }
> > > - nfsd4_interssc_disconnect(copy->ss_mnt);
> > > + /* ss_mnt will be unmounted by the laundromat */
> > > goto do_callback;
> > > }
> > > nfserr = nfsd4_do_copy(copy, filp, copy->nf_dst->nf_file,
> > > @@ -1852,8 +1841,10 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > > if (async_copy)
> > > cleanup_async_copy(async_copy);
> > > status = nfserrno(-ENOMEM);
> > > - if (nfsd4_ssc_is_inter(copy))
> > > - nfsd4_interssc_disconnect(copy->ss_mnt);
> > > + /*
> > > + * source's vfsmount of inter-copy will be unmounted
> > > + * by the laundromat
> > > + */
> > > goto out;
> > > }
> > >
> > This looks reasonable at first glance, but I have some concerns with the
> > refcounting around ss_mnt elsewhere in this code. nfsd4_ssc_setup_dul
> > looks for an existing connection and bumps the ni->nsui_refcnt if it
> > finds one.
> >
> > But then later, nfsd4_cleanup_inter_ssc has a couple of cases where it
> > just does a bare mntput:
> >
> > if (!nn) {
> > mntput(ss_mnt);
> > return;
> > }
> > ...
> > if (!found) {
> > mntput(ss_mnt);
> > return;
> > }
> >
> > The first one looks bogus. Can net_generic return NULL? If so how, and
> > why is it not a problem elsewhere in the kernel?
>
> it looks like net_generic can not fail, no where else check for NULL
> so I will remove this check.
>
> >
> > For the second case, if the ni is no longer on the list, where did the
> > extra ss_mnt reference come from? Maybe that should be a WARN_ON or
> > BUG_ON?
>
> if ni is not found on the list then it's a bug somewhere so I will add
> a BUG_ON on this.
>
Probably better to just WARN_ON and let any references leak in that
case. A BUG_ON implies a panic in some environments, and it's best to
avoid that unless there really is no choice.
--
Jeff Layton <jlayton@xxxxxxxxxx>
