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Date:   Fri, 16 Nov 2018 14:38:45 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
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        "Darrick J . Wong" <darrick.wong@oracle.com>,
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        Bob Peterson <rpeterso@redhat.com>, cluster-devel@redhat.com
Subject: Re: [PATCH V10 08/19] btrfs: move bio_pages_all() to btrfs
Message-ID: <20181116133845.GG3165@lst.de>
References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-9-ming.lei@redhat.com>
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On Thu, Nov 15, 2018 at 04:52:55PM +0800, Ming Lei wrote:
> BTRFS is the only user of this helper, so move this helper into
> BTRFS, and implement it via bio_for_each_segment_all(), since
> bio->bi_vcnt may not equal to number of pages after multipage bvec
> is enabled.

btrfs only uses the value to check if it is larger than 1.  No amount
of multipage bio merging should ever make bi_vcnt go from 0 to 1 or
vice versa.