On 11/29/2016 07:53 PM, NeilBrown wrote:
> When attempting an NFSv3 mount request, it is possible to catch the
> server at an "awkward" moment while it is still starting up.
> In these cases it is possible to get an error that would otherwise
> indiciate a permanent error, but which should be considered temporary during
> the start-up window.
>
> In particular:
> ECONNREFUSED will be returned between the time the network interface
> is configured, and the time that rpcbind starts
> EOPNOTSUPP (representing RPC_PROGNOTREGISTERED) will be returned between
> the time that rpcbind starts and the time when nfsd registers, and
> ESTALE will be returned between the time nfsd starts and when filesystems
> are exported (this windown can be removed with correct configuration).
>
> So these errors only deserve a relatively small timeout.
>
> So change nfs_is_permanent_error() to record the previous error
> and the number of times the same error has been seen.
> If ESTALE or EOPNOTSUPP is seen 3 times (over 3 seconds or more)
> or ECONNREFUSED is seen 5 times (15 seconds), report a permanent
> error, others assume it could be temporary.
>
> A result of this is that if you try a UDP mount from a server which
> doesn't support UDP, you get an error without a few seconds, rather
> than a 2-minute timeout.
>
> Signed-off-by: NeilBrown <neilb@xxxxxxxx>
> ---
> utils/mount/stropts.c | 27 ++++++++++++++++++++++-----
> 1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
> index 7b1ad93effc0..ba6593036a50 100644
> --- a/utils/mount/stropts.c
> +++ b/utils/mount/stropts.c
> @@ -935,20 +935,37 @@ static int nfs_try_mount(struct nfsmount_info *mi)
> * failed so far, but fail immediately if there is a local
> * error (like a bad mount option).
> *
> - * ESTALE is also a temporary error because some servers
> - * return ESTALE when a share is temporarily offline.
> + * If there is a remote error, like ESTALE or RPC_PROGNOTREGISTERED
> + * then it is probably permanent, but there is a small chance
> + * the it is temporary can we caught the server at an awkward
> + * time during start-up. So require that we see three of those
> + * before treating them as permanent.
> + * For ECONNREFUSED, wait a bit longer as there is often a longer
> + * gap between the network being ready and the NFS server starting.
> *
> * Returns 1 if we should fail immediately, or 0 if we
> * should retry.
> */
> static int nfs_is_permanent_error(int error)
> {
> + static int prev_error;
> + static int rpt_cnt;
> +
> + if (error == prev_error)
> + rpt_cnt += 1;
> + else
> + rpt_cnt = 1;
> + prev_error = error;
> +
> switch (error) {
> case ESTALE:
> - case ETIMEDOUT:
> + case EOPNOTSUPP: /* aka RPC_PROGNOTREGISTERED */
> + /* If two in a row, assume permanent */
> + return rpt_cnt >= 3;
This looks good... very clean... and now the time
out is control by the -o retry setting... Perfect!
> case ECONNREFUSED:
> + return rpt_cnt >= 5;
My only question is why mess with this? Over the years
we've always time out after 2 mins (the default) and now
we are bring that down to 15 secs? I'm think that might
be a bit short... I seems like we might be fixing something
that is not broken...
But again the design is very clever... nice work!
steved.
> + case ETIMEDOUT:
> case EHOSTUNREACH:
> - case EOPNOTSUPP: /* aka RPC_PROGNOTREGISTERED */
> case EAGAIN:
> return 0; /* temporary */
> default:
> @@ -1000,7 +1017,7 @@ static int nfsmount_fg(struct nfsmount_info *mi)
> if (secs > 10)
> secs = 10;
> }
> - };
> + }
>
> mount_error(mi->spec, mi->node, errno);
> return EX_FAIL;
>
>
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