linux-kernel - Re: [GIT] Please pull 2 NFS client fixes

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Message-Id: <20080207184818.e40d5277.akpm@linux-foundation.org>
Date:	Thu, 7 Feb 2008 18:48:18 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	nfsv4@...ux-nfs.org
Subject: Re: [GIT] Please pull 2 NFS client fixes

On Thu, 07 Feb 2008 20:07:21 -0500 Trond Myklebust <Trond.Myklebust@...app.com> wrote:

> commit 5d47a35600270e7115061cb1320ee60ae9bcb6b8
> Author: Trond Myklebust <Trond.Myklebust@...app.com>
> Date:   Thu Feb 7 17:24:07 2008 -0500
> 
>     NFS: Fix a potential file corruption issue when writing
>     
>     If the inode is flagged as having an invalid mapping, then we can't rely on
>     the PageUptodate() flag. Ensure that we don't use the "anti-fragmentation"
>     write optimisation in nfs_updatepage(), since that will cause NFS to write
>     out areas of the page that are no longer guaranteed to be up to date.
>     
>     A potential corruption could occur in the following scenario:
>     
>     client 1			client 2
>     ===============			===============
>     				fd=open("f",O_CREAT|O_WRONLY,0644);
>     				write(fd,"fubar\n",6);	// cache last page
>     				close(fd);
>     fd=open("f",O_WRONLY|O_APPEND);
>     write(fd,"foo\n",4);
>     close(fd);
>     
>     				fd=open("f",O_WRONLY|O_APPEND);
>     				write(fd,"bar\n",4);
>     				close(fd);
>     -----
>     The bug may lead to the file "f" reading 'fubar\n\0\0\0\nbar\n' because
>     client 2 does not update the cached page after re-opening the file for
>     write. Instead it keeps it marked as PageUptodate() until someone calls
>     invaldate_inode_pages2() (typically by calling read()).

Is this one worth feeding back into 2.6.24.x?  (for various values of "4"?)
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