Subject: Re: mmap over nfs leads to excessive system load
From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Andrew Morton <akpm@osdl.org>
Cc: theonetruekenny@yahoo.com, linux-kernel@vger.kernel.org
In-Reply-To: <20051116162516.61cb1e6b.akpm@osdl.org>
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Date: Wed, 16 Nov 2005 19:28:00 -0500
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On Wed, 2005-11-16 at 16:25 -0800, Andrew Morton wrote:
> Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> >
> > The accompanying NFS patch makes use of this in order to figure out when
> >  to flush the data correctly.
> 
> OK.  So with that patch, nfs_writepages() may still leave I/O pending,
> uninitiated, yes?
> 
> I don't understand why NFS hasn't been BUGging as it stands at present.  It
> has several end_page_writeback() calls but no set_page_writeback()s. 
> end_page_writeback() or rotate_reclaimable_page() will go BUG if the page
> wasn't PageWriteback().

It does have SetPageWriteback() calls in the asynchronous writeback
path. As you can see from the patch I just sent, I only needed to
replace them with set_page_writebacks().

Cheers,
 Trond

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