On Thu, 2008-02-07 at 18:48 -0800, Andrew Morton wrote:
> On Thu, 07 Feb 2008 20:07:21 -0500 Trond Myklebust <[EMAIL PROTECTED]> wrote:
>
> > commit 5d47a35600270e7115061cb1320ee60ae9bcb6b8
> > Author: Trond Myklebust <[EMAIL PROTECTED]>
> > 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"?)
Definitely, and probably back into 2.6.23.x, 2.6.22.x,... too.
Cheers
Trond
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