[Drbd-dev] [Bug 41602] DRBD: possible deadlock in Ahead mode

[Lars Ellenberg]

On Wed, Aug 24, 2011 at 03:14:47PM +0000, bugzilla-daemon at bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=41602

> --- Comment #2 from Cyril B. <cbay at excellency.fr>  2011-08-24 15:14:47 ---
> I can't rule out a misconfiguration, but I've been using DRBD since 8.0 on many
> servers and I've never seen such a thing happen. It's only happened very
> recently since I began using Linux 3.0 on a few servers, a few days ago.
> 
> Even if it's a temporary network failure that I've never had before:
> 
>  - how comes even a drbdadm disconnect doesn't work (i.e. hangs), and I have to
> reboot the primary server to be able to write on my filesystem again?

Arguably a design bug, the default disconnect waits for all current
requests to be handled.

You can try to --force disconnect, though.

>  - isn't the Ahead mode supposed to not block IO if the buffer is full and/or
> the secondary server is not accessible?

Well, yes, but it still needs to send some bytes (as oposed to the full
data block) to the peer. And if sendmsg blocks/times out/makes no
progress for whatever reason, we cannot do anything about that.

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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