On Thu, Sep 03, 2015 at 01:36:25PM -0400, Jeff Layton wrote:
> This is the userland companion patch for the patch to add a "nowcc"
> option to knfsd. This just adds the necessary code to allow userspace
> to set that option.
>
> Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
> ---
> support/include/nfs/export.h | 3 ++-
> support/nfs/exports.c | 5 +++++
> utils/exportfs/exportfs.c | 2 ++
> utils/exportfs/exports.man | 14 ++++++++++++++
> 4 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/support/include/nfs/export.h b/support/include/nfs/export.h
> index 1194255899bd..68bee5c2f305 100644
> --- a/support/include/nfs/export.h
> +++ b/support/include/nfs/export.h
> @@ -26,7 +26,8 @@
> #define NFSEXP_CROSSMOUNT 0x4000
> #define NFSEXP_NOACL 0x8000 /* reserved for possible ACL related use */
> #define NFSEXP_V4ROOT 0x10000
> -#define NFSEXP_PNFS 0x20000
> +#define NFSEXP_PNFS 0x20000
> +#define NFSEXP_NOWCC 0x40000
> /*
> * All flags supported by the kernel before addition of the
> * export_features interface:
> diff --git a/support/nfs/exports.c b/support/nfs/exports.c
> index 0aea6f154f09..791b5f756c9c 100644
> --- a/support/nfs/exports.c
> +++ b/support/nfs/exports.c
> @@ -276,6 +276,7 @@ putexportent(struct exportent *ep)
> if (ep->e_flags & NFSEXP_NOREADDIRPLUS)
> fprintf(fp, "nordirplus,");
> fprintf(fp, "%spnfs,", (ep->e_flags & NFSEXP_PNFS)? "" : "no_");
> + fprintf(fp, "%swcc,", (ep->e_flags & NFSEXP_NOWCC) ? "no" : "");
> if (ep->e_flags & NFSEXP_FSID) {
> fprintf(fp, "fsid=%d,", ep->e_fsid);
> }
> @@ -586,6 +587,10 @@ parseopts(char *cp, struct exportent *ep, int warn, int *had_subtree_opt_ptr)
> setflags(NFSEXP_PNFS, active, ep);
> else if (!strcmp(opt, "no_pnfs"))
> clearflags(NFSEXP_PNFS, active, ep);
> + else if (!strcmp(opt, "wcc"))
> + clearflags(NFSEXP_NOWCC, active, ep);
> + else if (!strcmp(opt, "nowcc"))
> + setflags(NFSEXP_NOWCC, active, ep);
> else if (strncmp(opt, "anonuid=", 8) == 0) {
> char *oe;
> ep->e_anonuid = strtol(opt+8, &oe, 10);
> diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c
> index 87582316b086..a2afc80ee6ea 100644
> --- a/utils/exportfs/exportfs.c
> +++ b/utils/exportfs/exportfs.c
> @@ -823,6 +823,8 @@ dump(int verbose, int export_format)
> c = dumpopt(c, "no_acl");
> if (ep->e_flags & NFSEXP_PNFS)
> c = dumpopt(c, "pnfs");
> + if (ep->e_flags & NFSEXP_NOWCC)
> + c = dumpopt(c, "nowcc");
> if (ep->e_flags & NFSEXP_FSID)
> c = dumpopt(c, "fsid=%d", ep->e_fsid);
> if (ep->e_uuid)
> diff --git a/utils/exportfs/exports.man b/utils/exportfs/exports.man
> index 93092463153b..9213a228bb04 100644
> --- a/utils/exportfs/exports.man
> +++ b/utils/exportfs/exports.man
> @@ -417,6 +417,20 @@ devices. The default can be explicitly requested with the
> .I no_pnfs
> option.
>
> +.TP
> +.IR nowcc
> +This option disables the collection and reporting of WCC (weak cache
> +consistency) data in NFSv3 requests. RFC 1813 recommends that all
> +servers report this information to the clients as it allows the client
> +to avoid some extra round trips to the server. In some underlying
> +filesystems however, collecting this data can be cost prohibitive and
> +atomicity is difficult to guarantee.
Which filesystems?
> Also, in some client use-cases WCC
> +data is ignored or not terribly useful. The default is to always report
> +weak cache consistency data to the client in NFSv3 requests, and can be
> +explicitly requested with the
> +.I wcc
> +option.
> +
This is a little vague. Can we give users any better guidelines?
--b.
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