Re: [PATCH/RFC v2 nfs-utils] Fix NFSv4 export of tmpfs filesystems.

[Petr Vorel <pvorel@suse.cz>]

Hi Neil,

> Some filesystems cannot be exported without an fsid or uuid.
> tmpfs is the main example.

> When mountd (or exportd) creates nfsv4 pseudo-root exports for the path
> leading down to an export point it exports each directory without any
> fsid or uuid.  If one of these directories is on tmp, that will fail.
                                                   ^ nit: you probably 
												   mean tmpfs

> The net result is that exporting a subdirectory of a tmpfs filesystem
> will not work over NFSv4 as the parents within the filesystem cannot be
> exported.  It will either fail, or fall-back to NFSv3 (depending on the
> version of the mount.nfs program).

> To fix this we need to provide an fsid or uuid for these pseudo-root
> exports.  This patch does that by creating an RFC-4122 V5 compatible
> UUID based on an arbitrary seed and the path to the export.

> To check if an export needs a uuid, text_export() is moved from exportfs
> to libexport.a, modified slightly and renamed to export_test().

> Signed-off-by: NeilBrown <neilb@suse.de>

Reported-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Tested-by: Petr Vorel <pvorel@suse.cz>

LGTM, thanks for fixing it.

...
> --- a/support/include/exportfs.h
> +++ b/support/include/exportfs.h
> @@ -173,5 +173,6 @@ struct export_features {
>  struct export_features *get_export_features(void);
>  void fix_pseudoflavor_flags(struct exportent *ep);
>  char *exportent_realpath(struct exportent *eep);
> +int export_test(struct exportent *eep, int with_fsid);

>  #endif /* EXPORTFS_H */
> diff --git a/utils/exportd/Makefile.am b/utils/exportd/Makefile.am
> index eb521f15032d..c95bdee76d3f 100644
> --- a/utils/exportd/Makefile.am
> +++ b/utils/exportd/Makefile.am
> @@ -16,7 +16,7 @@ exportd_SOURCES = exportd.c
>  exportd_LDADD = ../../support/export/libexport.a \
>  			../../support/nfs/libnfs.la \
>  			../../support/misc/libmisc.a \
> -			$(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD) 
> +			$(OPTLIBS) $(LIBBLKID) $(LIBPTHREAD) -luuid
I wonder if configure.ac should have libuuid check as it's now mandatory, e.g.:

AC_CHECK_LIB[uuid], uuid_parse, [LIBUUID="-luuid"], AC_MSG_ERROR([libuuid needed]))

Kind regards,
Petr