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Date:   Tue, 23 Aug 2022 15:07:57 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     David Howells <dhowells@redhat.com>
Cc:     sfrench@samba.org, linux-cifs@vger.kernel.org, lsahlber@redhat.com,
        jlayton@kernel.org, dchinner@redhat.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        samba-technical@lists.samba.org
Subject: Re: [PATCH 3/5] smb3: fix temporary data corruption in collapse range
Message-ID: <YwTfPRDq04/DGTVT@casper.infradead.org>
References: <166126004083.548536.11195647088995116235.stgit@warthog.procyon.org.uk>
 <166126006184.548536.12909933168251738646.stgit@warthog.procyon.org.uk>
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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);