linux-kernel - Re: [PATCH 3/5] smb3: fix temporary data corruption in collapse range

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Date:   Tue, 23 Aug 2022 15:07:57 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     sfrench@...ba.org, linux-cifs@...r.kernel.org, lsahlber@...hat.com,
        jlayton@...nel.org, dchinner@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        samba-technical@...ts.samba.org
Subject: Re: [PATCH 3/5] smb3: fix temporary data corruption in collapse range

On Tue, Aug 23, 2022 at 02:07:41PM +0100, David Howells wrote:
>  
> +	filemap_invalidate_lock(inode->i_mapping);
>  	filemap_write_and_wait(inode->i_mapping);
> +	truncate_pagecache_range(inode, off, old_eof);

It's a bit odd to writeback the entire file but then truncate only part
of it.  XFS does the same part:

        error = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (error)
                return error;
        truncate_pagecache_range(inode, start, end);

... and presumably, you'd also want the error check?

>  	rc = smb2_copychunk_range(xid, cfile, cfile, off + len,
> -				  i_size_read(inode) - off - len, off);
> +				  old_eof - off - len, off);