On Sun, Jan 15, 2017 at 03:43:21PM +0800, Kinglong Mee wrote: > On 1/11/2017 22:16, J. Bruce Fields wrote: > > On Sat, Jan 07, 2017 at 07:57:28PM +0800, Kinglong Mee wrote: > >> On 1/7/2017 05:05, J. Bruce Fields wrote: > >>> On Sat, Dec 31, 2016 at 09:05:11PM +0800, Kinglong Mee wrote: > >>>> test_export pass a export flags only marks NFSEXP_FSID, > >>>> nfsd may want other flags for export checking. > >>> > >>> Why? What problem does this fix? > >> > >> When testing the patch "NFSD: Only support readonly export for > >> !fsync and readonly filesystem", I found exportfs don't pass > >> all valid export flags to nfsd. So, make this patch. > > > > This function is meant to test whether a filesystem supports nfs export > > or not. It doesn't need the full set of export flags. Off the top of > > my head I can't see reason this would cause problems, but I'm not > > convinced it's safe, either. (New nfs-utils against old kernels might > > be a case to check, e.g. to see how unsupported flags are handled.) > > There are two cases that passing the flags to nfsd, > 1, exportfs checks the export entry, only NFSEXP_FSID without this patch, > 2, mountd pass the validate export entry, all validate export flags. > > When the new nfs-utils against old kernels, > user specifies an unsupported flags(Not NFSEXP_FSID), > exportfs doesn't warning that unsupported flags (without test), > mountd doesn't get the export entry for the flags. > > If exportfs warning the unsupported flags, user can modify it and > do the right export. > Do I have an exact understanding? OK, so when somebody specifies unsupported flags, the failures is silent and client mounts just fail. It would be better to warn when exportfs runs. I agree that that would be helpful. Have you tested those cases? (new nfs-utils, old kernel). It would be worth looking at validate_export() to see how it could improve error messages in this case. Currently it will say only: /example/export does not support NFS export or /example/export requires fsid= for export With your patch (forgive me if I misremember), I believe those are still the only error messages, so it will be confusing if, for example, you get /example/export does not support NFS export when the real problem is that an export flag is unsupported. (But maybe you had kernel messages to help there, I don't remember.) --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
