On Thu, Jul 14, 2016 at 12:26:43PM +1000, NeilBrown wrote:
> I now think this was a mistaken idea.
>
> If a filesystem is exported with the "mountpoint" or "mp" option, it
> should only be exported if the directory is a mount point. The
> intention is that if there is a problem with one filesystem on a
> server, the others can still be exported, but clients won't
> incorrectly see the empty directory on the parent when accessing the
> missing filesystem, they will see clearly that the filesystem is
> missing.
>
> It is easy to handle this correctly for NFSv3 MOUNT requests, but what
> is the correct behavior if a client already has the filesystem mounted
> and so has a filehandle? Maybe the server rebooted and came back with
> one device missing. What should the client see?
>
> The "dev_missing" code tries to detect this case and causes the server
> to respond with silence rather than ESTALE. The idea was that the
> client would retry and when (or if) the filesystem came back, service
> would be transparently restored.
>
> The problem with this is that arbitrarily long delays are not what
> people would expect, and can be quite annoying. ESTALE, while
> unpleasant, it at least easily understood. A device disappearing is a
> fairly significant event and hiding it doesn't really serve anyone.
It could also be a filesystem disappearing because it failed to mount in
time on a reboot.
> So: remove the code and allow ESTALE.
I'm not completely sure I understand the justification.
I don't like the current behavior either--I'd be happy if we could
deprecate "mountpoint" entirely--but changing it now would seem to risk
regressions if anyone depends on it.
--b.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
> utils/mountd/cache.c | 12 ------------
> 1 file changed, 12 deletions(-)
>
> diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
> index ec86a22613cf..346a8b3af8b5 100644
> --- a/utils/mountd/cache.c
> +++ b/utils/mountd/cache.c
> @@ -687,7 +687,6 @@ static void nfsd_fh(int f)
> char *found_path = NULL;
> nfs_export *exp;
> int i;
> - int dev_missing = 0;
> char buf[RPC_CHAN_BUF_SIZE], *bp;
> int blen;
>
> @@ -754,11 +753,6 @@ static void nfsd_fh(int f)
> if (!is_ipaddr_client(dom)
> && !namelist_client_matches(exp, dom))
> continue;
> - if (exp->m_export.e_mountpoint &&
> - !is_mountpoint(exp->m_export.e_mountpoint[0]?
> - exp->m_export.e_mountpoint:
> - exp->m_export.e_path))
> - dev_missing ++;
>
> if (!match_fsid(&parsed, exp, path))
> continue;
> @@ -801,12 +795,6 @@ static void nfsd_fh(int f)
> /* FIXME we need to make sure we re-visit this later */
> goto out;
> }
> - if (!found && dev_missing) {
> - /* The missing dev could be what we want, so just be
> - * quite rather than returning stale yet
> - */
> - goto out;
> - }
>
> if (found)
> if (cache_export_ent(buf, sizeof(buf), dom, found, found_path) < 0)
>
>
> --
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