Date: Sat, 10 Oct 2009 14:06:14 +0200
From: Pavel Machek <pavel@ucw.cz>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Hellwig <hch@infradead.org>,
       Suresh Jayaraman <sjayaraman@suse.de>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, netdev@vger.kernel.org, Neil Brown <neilb@suse.de>,
       Miklos Szeredi <mszeredi@suse.cz>, Wouter Verhelst <w@uter.be>,
       trond.myklebust@fys.uio.no
Subject: Re: [PATCH 00/31] Swap over NFS -v20
Message-ID: <20091010120614.GC1811@ucw.cz>
References: <1254405858-15651-1-git-send-email-sjayaraman@suse.de> <20091001174201.GA30068@infradead.org> <1254692482.21044.15.camel@laptop>
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Hi!

> > One of them
> > would be the whole VM/net work to just make swap over nbd/iscsi safe.
> 
> Getting those two 'fixed' is going to be tons of interesting work
> because they involve interaction with userspace daemons.
> 
> NBD has fairly simple userspace, but iSCSI has a rather large userspace
> footprint and a rather complicated user/kernel interaction which will be
> mighty interesting to get allocation safe.
> 
> Ideally the swap-over-$foo bits have no userspace component.
> 
> That said, Wouter is the NBD userspace maintainer and has expressed
> interest into looking at making that work, but its sure going to be
> non-trivial, esp. since exposing PF_MEMALLOC to userspace is a, not over
> my dead-bodym like thing.

Well, as long as nbd-server is on separate machine (with real swap),
safe swapping over network should be ok, without PF_MEMALLOC for
userspace or similar nightmares, right?
								Pavel  

-- 
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