linux-kernel - Re: [PATCH v2 00/13] btrfs: clean up RAID I/O geometry calculation

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Message-ID: <20231213185204.GE3001@twin.jikos.cz>
Date:   Wed, 13 Dec 2023 19:52:04 +0100
From:   David Sterba <dsterba@...e.cz>
To:     Johannes Thumshirn <johannes.thumshirn@....com>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 00/13] btrfs: clean up RAID I/O geometry calculation

On Wed, Dec 13, 2023 at 06:42:55AM -0800, Johannes Thumshirn wrote:
> The calculation of the RAID I/O geometry in btrfs_map_block has been a maze of
> if-else statements for a very long time and the advent of the
> raid-stripe-tree made the situation even worse.
> 
> This patchset refactors btrfs_map_block() to untagle the maze and make I/O
> geometry setting easier to follow, but does not introduce any functional
> changes.
> 
> I've also run it through Josef's CI and there have been test failures, but
> none of them introduced by these patches.
> 
> ---
> Changes in v2:
> - add btrfs_map_op into struct btrfs_io_geometry
> - split RAID56 read and write into two different helpers
> - drop redundand 'for' in helper function names
> - kept dev_replace_is_ongoing variable name
> - Link to v1: https://lore.kernel.org/r/20231212-btrfs_map_block-cleanup-v1-0-b2d954d9a55b@wdc.com
> 
> ---
> Johannes Thumshirn (13):
>       btrfs: factor out helper for single device IO check
>       btrfs: re-introduce struct btrfs_io_geometry
>       btrfs: factor out block-mapping for RAID0
>       btrfs: factor out RAID1 block mapping
>       btrfs: factor out block mapping for DUP profiles
>       btrfs: factor out block mapping for RAID10
>       btrfs: reduce scope of data_stripes in btrfs_map_block
>       btrfs: factor out block mapping for RAID5/6
>       btrfs: factor out block mapping for single profiles
>       btrfs: btrfs: untagle if else maze in btrfs_map_block
>       btrfs: open code set_io_stripe for RAID56
>       btrfs: pass struct btrfs_io_geometry to set_io_stripe
>       btrfs: pass btrfs_io_geometry into btrfs_max_io_len

Added to misc-next with some adjustments, thanks. I've noticed some of
the helpers can take const parameters, some lines that can be joined so
the expression is one one line, but there are calculations like in
"btrfs: open code set_io_stripe for RAID56" where it's up to your
creativity.