linux-kernel - Re: Odd NFS related SIGBUS (& possible fix)

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Message-ID: <1285966407.2463.145.camel@pasglop>
Date:	Sat, 02 Oct 2010 06:53:27 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Nick Piggin <npiggin@...nel.dk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-fsdevel@...r.kernel.org
Subject: Re: Odd NFS related SIGBUS (& possible fix)

On Fri, 2010-10-01 at 14:12 -0400, Trond Myklebust wrote:
> 
> However, it looks to me as if the right thing to do when the
> page->mapping has changed would be to do the same thing as
> block_page_mkwrite(), and just return VM_FAULT_NOPAGE so that the VM
> can
> retry the fault.
> IMO: We should only SIGBUS if the calls to nfs_flush_incompatible()
> and/or nfs_updatepage() fail.

Well, other filesystems seem to think that if the mapping -changed-,
SIGBUS is a good idea... But they don't have to deal with invalidations
wiping mappings in the background.

So that's why I was thinking about singling out the "mapping became
NULL" case and keep the SIGBUS for when the mapping became something
else... but that's your call really :-)

Cheers,
Ben.

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