linux-kernel - Re: [PATCH v2] docs: ext4: modify the group desc size to 64

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Message-ID: <Y/WXkhxhJ742G4xB@magnolia>
Date:   Tue, 21 Feb 2023 20:18:26 -0800
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Wu Bo <bo.wu@...o.com>
Cc:     Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jonathan Corbet <corbet@....net>, linux-ext4@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] docs: ext4: modify the group desc size to 64

On Wed, Feb 22, 2023 at 09:35:24AM +0800, Wu Bo wrote:
> Since the default ext4 group desc size is 64 now (assuming that the
> 64-bit feature is enbled). And the size mentioned in this doc is 64 too.
> Change it to 64.
> 
> Signed-off-by: Wu Bo <bo.wu@...o.com>

32-bit blockgroup descriptors aren't that ancient of a disk format, it's
probably helpful to mention that one should double the ratios for ^64bit
filesystems.

Also: Not sure what went wrong with your emptyish To: line?

If Ted's ok with this, then:
Acked-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  Documentation/filesystems/ext4/blockgroup.rst | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/filesystems/ext4/blockgroup.rst b/Documentation/filesystems/ext4/blockgroup.rst
> index 46d78f860623..ed5a5cac6d40 100644
> --- a/Documentation/filesystems/ext4/blockgroup.rst
> +++ b/Documentation/filesystems/ext4/blockgroup.rst
> @@ -105,9 +105,9 @@ descriptors. Instead, the superblock and a single block group descriptor
>  block is placed at the beginning of the first, second, and last block
>  groups in a meta-block group. A meta-block group is a collection of
>  block groups which can be described by a single block group descriptor
> -block. Since the size of the block group descriptor structure is 32
> -bytes, a meta-block group contains 32 block groups for filesystems with
> -a 1KB block size, and 128 block groups for filesystems with a 4KB
> +block. Since the size of the block group descriptor structure is 64
> +bytes, a meta-block group contains 16 block groups for filesystems with
> +a 1KB block size, and 64 block groups for filesystems with a 4KB
>  blocksize. Filesystems can either be created using this new block group
>  descriptor layout, or existing filesystems can be resized on-line, and
>  the field s_first_meta_bg in the superblock will indicate the first
> -- 
> 2.35.3
>