Hi: Bruce:
> On 5/31/18, 10:34 AM, "bfields@xxxxxxxxxxxx" <bfields@xxxxxxxxxxxx> wrote:
> On Thu, May 31, 2018 at 04:51:49PM +0000, Shawn Lu (shawlu) wrote:
> > >On 5/31/18, 8:18 AM, "bfields@xxxxxxxxxxxx" <bfields@xxxxxxxxxxxx> wrote:
> > > > One case is involved with cross mounted nfs from different host.
> >
> > > Note: in theory I think there are some deadlocks possible if client and
> > > server mount each other. (Each host could be waiting on the other one
> > > to process writes before it can free memory that it needs to make
> > > progress.)
> >
> > Yes. I hope aggressive umount will help by setting a very short grace period and timeout before umount.
> No, the deadlock isn't an unmounting problem, it's a problem that could
> happen during normal operation. I don't know if it's easy to reproduce.
> You'd probably need one or both hosts to be writing to NFS very quickly.
Yes, This will a big issue for cross mount. Luckily, we have not experience it yet due to low traffic.
By the way, what is your suggestion on the road to enhance “umount –f” ? Will add kernel config option to support guaranteed force unmount helps?
> --b.
Thanks,
Shawn
On 5/31/18, 10:34 AM, "bfields@xxxxxxxxxxxx" <bfields@xxxxxxxxxxxx> wrote:
On Thu, May 31, 2018 at 04:51:49PM +0000, Shawn Lu (shawlu) wrote:
> >On 5/31/18, 8:18 AM, "bfields@xxxxxxxxxxxx" <bfields@xxxxxxxxxxxx> wrote:
> > > One case is involved with cross mounted nfs from different host.
>
> > Note: in theory I think there are some deadlocks possible if client and
> > server mount each other. (Each host could be waiting on the other one
> > to process writes before it can free memory that it needs to make
> > progress.)
>
> Yes. I hope aggressive umount will help by setting a very short grace period and timeout before umount.
No, the deadlock isn't an unmounting problem, it's a problem that could
happen during normal operation. I don't know if it's easy to reproduce.
You'd probably need one or both hosts to be writing to NFS very quickly.
--b.
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