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Date:   Thu, 11 Mar 2021 13:30:02 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc:     linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
        linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org,
        darrick.wong@oracle.com, dan.j.williams@intel.com,
        willy@infradead.org, jack@suse.cz, viro@zeniv.linux.org.uk,
        linux-btrfs@vger.kernel.org, ocfs2-devel@oss.oracle.com,
        david@fromorbit.com, hch@lst.de, rgoldwyn@suse.de
Subject: Re: [RESEND PATCH v2.1 07/10] iomap: Introduce iomap_apply2() for
 operations on two files
Message-ID: <20210311123002.GA18838@lst.de>
References: <20210226002030.653855-8-ruansy.fnst@fujitsu.com> <20210304054142.1147895-1-ruansy.fnst@fujitsu.com>
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On Thu, Mar 04, 2021 at 01:41:42PM +0800, Shiyang Ruan wrote:
> Some operations, such as comparing a range of data in two files under
> fsdax mode, requires nested iomap_open()/iomap_end() on two file.  Thus,
> we introduce iomap_apply2() to accept arguments from two files and
> iomap_actor2_t for actions on two files.

I still wonder if adding the iter based iomap API that willy proposed
would be a better fit here.  In that case we might not even need
a special API for the double iteration.