On Fri, 2017-11-10 at 10:31 +0800, Yan, Zheng wrote:
> On Fri, Nov 10, 2017 at 12:03 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote:
> > From: Jeff Layton <jlayton@xxxxxxxxxx>
> >
> > FSAL_CEPH just does a ceph_ll_get_inode when asked to create a
> > filehandle today, which only does a query of the local Ceph client
> > cache. This means, it can only find Inodes that were previously found
> > via name lookup.
> >
> > When ganesha is restarted, we have a blank-slate Client, and the Inode
> > will not be in cache. That ends up with the NFS client getting back an
> > ESTALE.
> >
> > We must be able to find Inodes that may not be in the cache. When
> > ceph_ll_get_inode can't find an Inode, try a lookup vs. the MDS for it.
> >
> > The only problem is that we currently have no way to look up a snapped
> > inode from scratch. I think we'll probably need to add that ability to
> > libcephfs, but for now the best we can do is just bail out with an
> > ESTALE in that case.
> >
> > While we're in there, remove the comment about ceph_ll_connectable_m.
> > There is no such function in libcephfs and never has been. The ds
> > code does seem to refer to such a call, but it's not clear to me
> > what it's supposed to do.
> >
> > Change-Id: I2d0e362ef8f28ba78575b60f3fb2890096d98fc6
> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> >
> > I sent this up through git-review to ganesha's gerrit, but I'd
> > like some cephfs folks to have a look too. This patch is basically
> > a workaround for the FSAL_CEPH code for now.
> >
> > Do we need to worry about inodes that are not CEPH_NOSNAP? It
> > seems like we might need for libcephfs to grow an interface that
> > can look up snapped inodes as well?
> >
> > Either that, or teach ceph_ll_get_inode how to look up inodes
> > that are not in its cache. Would that be a better fix here?
> >
> > src/FSAL/FSAL_CEPH/export.c | 19 +++++++++++++++----
> > 1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/src/FSAL/FSAL_CEPH/export.c b/src/FSAL/FSAL_CEPH/export.c
> > index 3de25fdfaf41..a31e3bb3ebef 100644
> > --- a/src/FSAL/FSAL_CEPH/export.c
> > +++ b/src/FSAL/FSAL_CEPH/export.c
> > @@ -234,12 +234,23 @@ static fsal_status_t create_handle(struct fsal_export *export_pub,
> > return status;
> > }
> >
> > + /* Check our local cache first */
> > i = ceph_ll_get_inode(export->cmount, *vi);
> > - if (!i)
> > - return ceph2fsal_error(-ESTALE);
> > + if (!i) {
> > + /*
> > + * Try the slow way, may not be in cache now.
> > + *
> > + * Currently, there is no interface for looking up a snapped
> > + * inode, so we just bail here in that case.
> > + */
> > + if (vi->snapid.val != CEPH_NOSNAP)
> > + return ceph2fsal_error(-ESTALE);
> > +
> > + rc = ceph_ll_lookup_inode(export->cmount, vi->ino, &i);
> > + if (rc)
> > + return ceph2fsal_error(rc);
> > + }
> >
> > - /* The ceph_ll_connectable_m should have populated libceph's
> > - cache with all this anyway */
> > rc = fsal_ceph_ll_getattr(export->cmount, i, &stx,
> > attrs_out ? CEPH_STATX_ATTR_MASK : CEPH_STATX_HANDLE_MASK,
> > op_ctx->creds);
> > --
> > 2.13.6
> >
>
> Looks good to me,
>
> Tested-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
>
Thanks. I still wonder whether this is a sufficient fix.
ceph_ll_lookup_inode does not take the snapid into account. Do we need a
version of ceph_ll_lookup_inode that can find snapshotted inodes after
ganesha has restarted?
It does seem like we could allow a nfs client do work in a snapshotted
directory, and then have ganesha restart. That client may be very
confused when the server comes back and all of the existing filehandles
go stale.
--
Jeff Layton <jlayton@xxxxxxxxxx>
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