Messages in this thread | | | Date | Tue, 5 Nov 2013 13:39:59 +1100 | From | NeilBrown <> | Subject | Re: [PATCH] [RFC] vfs: don't revalidate dentries that serve as mountpoints |
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On Mon, 4 Nov 2013 20:16:26 -0500 Jeff Layton <jlayton@redhat.com> wrote:
> We had a couple of reports of people that are mounting NFS filesystems, > and then bind mounting certain local files onto dentries in that nfs > mount (sort of like a poor-man's unionmount). > > This all works well until the dentry serving as the mountpoint fails > d_revalidate. The dentry will end up being invalidated which makes the > bind mount unreachable via pathwalk. > > It doesn't make much sense to me to allow dentries to serve as > mountpoints to end up invalidated, so there's no real point in > attempting to d_revalidate them at all. > > Reported-by: Patrick McLean <chutzpah@gentoo.org> > Reported-by: Guang Cheng Li <liguangc@cn.ibm.com> > Signed-off-by: Jeff Layton <jlayton@redhat.com> > --- > fs/namei.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/namei.c b/fs/namei.c > index caa2805..5b10ad0 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -585,6 +585,9 @@ drop_root_mnt: > > static inline int d_revalidate(struct dentry *dentry, unsigned int flags) > { > + /* dentries that serve as mountpoints are always considered valid */ > + if (d_mountpoint(dentry)) > + return 1; > return dentry->d_op->d_revalidate(dentry, flags); > } >
Makes sense to me. But what about the parent or grandparent of the mountpoint?
Presumably we don't want to invalidate them either, and I don't think d_mountpoint() returns true for those, does it?
NeilBrown [unhandled content-type:application/pgp-signature] | |