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"?)
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