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Date:   Mon, 4 Jan 2021 09:44:15 +0100
From:   Christoph Hellwig <>
To:     Ming Lei <>
        Alexander Viro <>,,,
        Christoph Hellwig <>, Jens Axboe <>
Subject: Re: [PATCH] fs/buffer: try to submit writeback bio in unit of page

On Wed, Dec 30, 2020 at 08:08:15AM +0800, Ming Lei wrote:
> It is observed that __block_write_full_page() always submit bio with size of block size,
> which is often 512 bytes.
> In case of sequential IO, or >=4k BS random/seq writeback IO, most of times IO
> represented by all buffer_head in each page can be done in single bio. It is actually
> done in single request IO by block layer's plug merge too.
> So check if IO represented by buffer_head can be merged to single page
> IO, if yes, just submit single bio instead of submitting one bio for each buffer_head.

There is some very weird formatting in here.  From a very quick look
the changes look sensible, but I wonder if we should spend so much
time optimizing the legacy buffer_head I/O path, rather than switching
callers to saner helpers.

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