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Date: Mon, 9 Jan 2017 01:31:48 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>, linux-btrfs@vger.kernel.org,
        Jeff Mahoney <jeffm@suse.com>, David Sterba <dsterba@suse.com>
Subject: Re: [RFC] Converging userspace and kernel code
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On Mon, Jan 09, 2017 at 10:11:29AM +0800, Qu Wenruo wrote:
> (I'm already trying to re-implement btrfs_map_block() in btrfs-progs with a
> better interface in out-of-tree offline scrub patchset)

How about doing the right thing in the kernel as well?  While looking
at the btrfs abuse of the block REQ_* flag I had to read and understand
__btrfs_map_block and agree it's ripe for refactoring.