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From: Amir Goldstein <amir73il@gmail.com>
Date: Thu, 10 May 2018 07:47:42 +0300
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Subject: Re: [PATCH v2 0/4] Enable holes in copy_file_range()
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        Dave Chinner <david@fromorbit.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Anna Schumaker <Anna.Schumaker@netapp.com>
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On Thu, May 10, 2018 at 4:58 AM, Goldwyn Rodrigues <rgoldwyn@suse.de> wrote:
> If copy_file_range performs a copy using splice, it converts holes
> to zeros. This effort primarily changes this behavior to create
> holes when it is possible.
>
> Even if copy_file_range() or clone_file_range() does not work for different
> mounted filesystems, We should be able to splice files if they do not
> belong the same super_block.
>
> Changes since v1:
> - Fixed bug when hole/data offset is farther than len

Please specify how you tested this work.
Did you run the xfstests generic/copy tests that Anna wrote?
If the tests caught your bugs - good, if they didn't, please
write more tests to cover the issues you found.
One thing I do not see in the existing tests is coverage for the
trivial case of "only holes" (i.e. touch x; truncate -s 10 x).

Thanks,
Amir.