Subject: Re: [Ksummit-2005-discuss] Summary of 2005 Kernel Summit Proposed Topics

From: Mike Christie <[email-masked]>
Date: Wed, 30 Mar 2005 12:10:58 -0800

Dmitry Yusupov wrote:
> On Wed, 2005-03-30 at 09:24 -0800, Matt Mackall wrote: 
> 
>>I seem to recall this being fairly easy to trigger by simply pulling
>>the network cable while there's heavy mmap + write load. The system
>>will quickly spiral down into OOM and will remain wedged when you plug
>>the network back in. With iSCSI, after some extended period all the
>>I/Os will have SCSI timeouts and lose everything.
> 
> 
> We've discussed that already. SCSI timeout logic just doesn't fit. (see
> rfc3720). For iSCSI, SCSI timeout logic *must* be disabled until iSCSI
> recovery is complete.

This has actually been brought up when the scsi_times_out thread was going
on. It kinda was at least. Some driver writers inluding sfnet used to play
a lot of tricks with the timers to accomplish this (this was the goal
for sfnet at least) and I do not think linux-scsi will allow it. Maybe that
will change.

  host block/unblock logic in recent iSCSI transport
> patch will help to implement that.
> 

No it won't :( block/unblock does not disable timeouts it just makes it
so new commands are not queued and they timeout when the driver knows
that the transport is hosed.