| Message ID | 20200908211958.38741-1-trondmy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mountd: Ignore transient and non-fatal filesystem errors in nfsd_export | expand |
On Tue, Sep 08, 2020 at 05:19:58PM -0400, trondmy@kernel.org wrote: > From: Trond Myklebust <trond.myklebust@hammerspace.com> > > If the mount point check in nfsd_export fails due to a transient error, > then ignore it to avoid spurious NFSERR_STALE errors being returned by > knfsd. What sort of transient errors? I guess this makes the upcall (and the original rpc) eventually time out? --b. > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> > --- > utils/mountd/cache.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c > index 6cba2883026f..93e868341d15 100644 > --- a/utils/mountd/cache.c > +++ b/utils/mountd/cache.c > @@ -1411,7 +1411,10 @@ static void nfsd_export(int f) > > if (mp && !*mp) > mp = found->m_export.e_path; > - if (mp && !is_mountpoint(mp)) > + errno = 0; > + if (mp && !is_mountpoint(mp)) { > + if (errno != 0 && !path_lookup_error(errno)) > + goto out; > /* Exportpoint is not mounted, so tell kernel it is > * not available. > * This will cause it not to appear in the V4 Pseudo-root > @@ -1420,9 +1423,12 @@ static void nfsd_export(int f) > * And filehandle for this mountpoint from an earlier > * mount will block in nfsd.fh lookup. > */ > + xlog(L_WARNING, > + "Cannot export path '%s': not a mountpoint", > + path); > dump_to_cache(f, buf, sizeof(buf), dom, path, > NULL, 60); > - else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > + } else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > &found->m_export, 0) < 0) { > xlog(L_WARNING, > "Cannot export %s, possibly unsupported filesystem" > -- > 2.26.2
On Thu, 2020-09-10 at 13:02 -0400, J. Bruce Fields wrote: > On Tue, Sep 08, 2020 at 05:19:58PM -0400, trondmy@kernel.org wrote: > > From: Trond Myklebust <trond.myklebust@hammerspace.com> > > > > If the mount point check in nfsd_export fails due to a transient > > error, > > then ignore it to avoid spurious NFSERR_STALE errors being returned > > by > > knfsd. > > What sort of transient errors? > > I guess this makes the upcall (and the original rpc) eventually time > out? The point here is that is_mountpoint() is making the assumption that _any_ error from stat() can be used to infer that there is nothing mounted. In reality, only a subset of errors allow it to make that assumption (specifically the errors ELOOP, ENAMETOOLONG, ENOENT, and ENOTDIR). In our case, we're seeing a problem when the underlying filesystem is a soft mounted NFSv4.2 client (i.e. we're running our Hammerspace use case of proxying NFSv4.2 to legacy NFSv3 clients) and that NFS4.2 mount times out due to a reboot of the underlying server, for instance. So, yes, in that case we want the upcall to time out instead of poking knfsd into declaring that the directory is stale. > > --b. > > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> > > --- > > utils/mountd/cache.c | 10 ++++++++-- > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c > > index 6cba2883026f..93e868341d15 100644 > > --- a/utils/mountd/cache.c > > +++ b/utils/mountd/cache.c > > @@ -1411,7 +1411,10 @@ static void nfsd_export(int f) > > > > if (mp && !*mp) > > mp = found->m_export.e_path; > > - if (mp && !is_mountpoint(mp)) > > + errno = 0; > > + if (mp && !is_mountpoint(mp)) { > > + if (errno != 0 && !path_lookup_error(errno)) > > + goto out; > > /* Exportpoint is not mounted, so tell kernel > > it is > > * not available. > > * This will cause it not to appear in the V4 > > Pseudo-root > > @@ -1420,9 +1423,12 @@ static void nfsd_export(int f) > > * And filehandle for this mountpoint from an > > earlier > > * mount will block in nfsd.fh lookup. > > */ > > + xlog(L_WARNING, > > + "Cannot export path '%s': not a > > mountpoint", > > + path); > > dump_to_cache(f, buf, sizeof(buf), dom, path, > > NULL, 60); > > - else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > > + } else if (dump_to_cache(f, buf, sizeof(buf), dom, > > path, > > &found->m_export, 0) < 0) { > > xlog(L_WARNING, > > "Cannot export %s, possibly unsupported > > filesystem" > > -- > > 2.26.2
On Thu, Sep 10, 2020 at 05:25:19PM +0000, Trond Myklebust wrote: > On Thu, 2020-09-10 at 13:02 -0400, J. Bruce Fields wrote: > > On Tue, Sep 08, 2020 at 05:19:58PM -0400, trondmy@kernel.org wrote: > > > From: Trond Myklebust <trond.myklebust@hammerspace.com> > > > > > > If the mount point check in nfsd_export fails due to a transient > > > error, > > > then ignore it to avoid spurious NFSERR_STALE errors being returned > > > by > > > knfsd. > > > > What sort of transient errors? > > > > I guess this makes the upcall (and the original rpc) eventually time > > out? > > The point here is that is_mountpoint() is making the assumption that > _any_ error from stat() can be used to infer that there is nothing > mounted. In reality, only a subset of errors allow it to make that > assumption (specifically the errors ELOOP, ENAMETOOLONG, ENOENT, and > ENOTDIR). > > In our case, we're seeing a problem when the underlying filesystem is a > soft mounted NFSv4.2 client (i.e. we're running our Hammerspace use > case of proxying NFSv4.2 to legacy NFSv3 clients) and that NFS4.2 mount > times out due to a reboot of the underlying server, for instance. > > So, yes, in that case we want the upcall to time out instead of poking > knfsd into declaring that the directory is stale. Thanks for the explanation, I guess I agree that's the best you can do in that situation. --b. > > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> > > > --- > > > utils/mountd/cache.c | 10 ++++++++-- > > > 1 file changed, 8 insertions(+), 2 deletions(-) > > > > > > diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c > > > index 6cba2883026f..93e868341d15 100644 > > > --- a/utils/mountd/cache.c > > > +++ b/utils/mountd/cache.c > > > @@ -1411,7 +1411,10 @@ static void nfsd_export(int f) > > > > > > if (mp && !*mp) > > > mp = found->m_export.e_path; > > > - if (mp && !is_mountpoint(mp)) > > > + errno = 0; > > > + if (mp && !is_mountpoint(mp)) { > > > + if (errno != 0 && !path_lookup_error(errno)) > > > + goto out; > > > /* Exportpoint is not mounted, so tell kernel > > > it is > > > * not available. > > > * This will cause it not to appear in the V4 > > > Pseudo-root > > > @@ -1420,9 +1423,12 @@ static void nfsd_export(int f) > > > * And filehandle for this mountpoint from an > > > earlier > > > * mount will block in nfsd.fh lookup. > > > */ > > > + xlog(L_WARNING, > > > + "Cannot export path '%s': not a > > > mountpoint", > > > + path); > > > dump_to_cache(f, buf, sizeof(buf), dom, path, > > > NULL, 60); > > > - else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > > > + } else if (dump_to_cache(f, buf, sizeof(buf), dom, > > > path, > > > &found->m_export, 0) < 0) { > > > xlog(L_WARNING, > > > "Cannot export %s, possibly unsupported > > > filesystem" > > > -- > > > 2.26.2 > -- > Trond Myklebust > CTO, Hammerspace Inc > 4984 El Camino Real, Suite 208 > Los Altos, CA 94022 > www.hammer.space >
On 9/8/20 5:19 PM, trondmy@kernel.org wrote: > From: Trond Myklebust <trond.myklebust@hammerspace.com> > > If the mount point check in nfsd_export fails due to a transient error, > then ignore it to avoid spurious NFSERR_STALE errors being returned by > knfsd. > > Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com> Committed... (tag: nfs-utils-2-5-2-rc5) steved. > --- > utils/mountd/cache.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c > index 6cba2883026f..93e868341d15 100644 > --- a/utils/mountd/cache.c > +++ b/utils/mountd/cache.c > @@ -1411,7 +1411,10 @@ static void nfsd_export(int f) > > if (mp && !*mp) > mp = found->m_export.e_path; > - if (mp && !is_mountpoint(mp)) > + errno = 0; > + if (mp && !is_mountpoint(mp)) { > + if (errno != 0 && !path_lookup_error(errno)) > + goto out; > /* Exportpoint is not mounted, so tell kernel it is > * not available. > * This will cause it not to appear in the V4 Pseudo-root > @@ -1420,9 +1423,12 @@ static void nfsd_export(int f) > * And filehandle for this mountpoint from an earlier > * mount will block in nfsd.fh lookup. > */ > + xlog(L_WARNING, > + "Cannot export path '%s': not a mountpoint", > + path); > dump_to_cache(f, buf, sizeof(buf), dom, path, > NULL, 60); > - else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > + } else if (dump_to_cache(f, buf, sizeof(buf), dom, path, > &found->m_export, 0) < 0) { > xlog(L_WARNING, > "Cannot export %s, possibly unsupported filesystem" >
diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c index 6cba2883026f..93e868341d15 100644 --- a/utils/mountd/cache.c +++ b/utils/mountd/cache.c @@ -1411,7 +1411,10 @@ static void nfsd_export(int f) if (mp && !*mp) mp = found->m_export.e_path; - if (mp && !is_mountpoint(mp)) + errno = 0; + if (mp && !is_mountpoint(mp)) { + if (errno != 0 && !path_lookup_error(errno)) + goto out; /* Exportpoint is not mounted, so tell kernel it is * not available. * This will cause it not to appear in the V4 Pseudo-root @@ -1420,9 +1423,12 @@ static void nfsd_export(int f) * And filehandle for this mountpoint from an earlier * mount will block in nfsd.fh lookup. */ + xlog(L_WARNING, + "Cannot export path '%s': not a mountpoint", + path); dump_to_cache(f, buf, sizeof(buf), dom, path, NULL, 60); - else if (dump_to_cache(f, buf, sizeof(buf), dom, path, + } else if (dump_to_cache(f, buf, sizeof(buf), dom, path, &found->m_export, 0) < 0) { xlog(L_WARNING, "Cannot export %s, possibly unsupported filesystem"