Re: [PATCH 0/2] Introduce dns_interval procfs setting

[Enzo Matsumiya <ematsumiya@suse.de>]

On 06/09, Tom Talpey wrote:
>On 6/8/2022 5:54 PM, Enzo Matsumiya wrote:
>>Hi,
>>
>>These 2 patches are a simple way to fix the DNS issue that
>>currently exists in cifs, where the upcall to key.dns_resolver will
>>always return 0 for the record TTL, hence, making the resolve worker
>>always use the default value SMB_DNS_RESOLVE_INTERVAL_DEFAULT
>>(currently 600 seconds).
>>
>>This also makes the new setting `dns_interval' user-configurable via
>>procfs (/proc/fs/cifs/dns_interval).
>>
>>One disadvantage here is that the interval is applied to all hosts
>>resolution. This is still how it works today, because we're always using
>>the default value anyway, but should someday this be fixed, then we can
>>go back to rely on the keys infrastructure to cache each hostname with
>>its own separate TTL.
>
>Curious, why did you choose a procfs global approach? Wouldn't it be
>more appropriate to make this a mount option, so it would be applied
>selectively per-server?

I tried to stick to the current behaviour, while also fixing the issue
of getting a TTL=0 from key.dns_resolver upcall.

A mount option looks indeed better initially, and that was also my
initial approach to this. But in a, e.g. multi-domain forest, with
multiple DFS targets, the per-mount setting starts to look irrelevant
again as well. So I took the "per-client" approach instead.


Cheers,

Enzo