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Date:   Mon, 23 Aug 2021 14:58:24 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc:     djwong@kernel.org, hch@lst.de, linux-xfs@vger.kernel.org,
        dan.j.williams@intel.com, david@fromorbit.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        nvdimm@lists.linux.dev, rgoldwyn@suse.de, viro@zeniv.linux.org.uk,
        willy@infradead.org
Subject: Re: [PATCH v7 5/8] iomap: Introduce iomap_iter2 for two files
Message-ID: <20210823125824.GB15536@lst.de>
References: <20210816060359.1442450-1-ruansy.fnst@fujitsu.com> <20210816060359.1442450-6-ruansy.fnst@fujitsu.com>
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On Mon, Aug 16, 2021 at 02:03:56PM +0800, Shiyang Ruan wrote:
> Some operations, such as comparing a range of data in two files under
> fsdax mode, requires nested iomap_begin()/iomap_end() on two files.
> Thus, we introduce iomap_iter2() to accept two iteraters to operate
> action on two files.

We really should not need both.  We should be able to be in two
nested loops, just operating on the part that both cover (for which
a helper might be useful).