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Date: Thu, 7 Nov 2024 08:33:18 +0100
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org, hch@lst.de
Subject: Re: [PATCH 2/4] design: document realtime groups
Message-ID: <20241107073318.GF4408@lst.de>
References: <173092059696.2883258.7093773656482973762.stgit@frogsfrogsfrogs> <173092059729.2883258.3327326591290447581.stgit@frogsfrogsfrogs>
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User-Agent: Mutt/1.5.17 (2007-11-01)

> --- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> +++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> @@ -106,6 +106,10 @@ struct xfs_sb
>  	xfs_lsn_t		sb_lsn;
>  	uuid_t			sb_meta_uuid;
>  	xfs_ino_t		sb_metadirino;
> +	xfs_rgnumber_t		sb_rgcount;
> +	xfs_rgblock_t		sb_rgextents;
> +	uint8_t			sb_rgblklog;
> +	uint8_t			sb_pad[7];

And following on with my ranting about existing bits theme from the
previous review:  why are we documenting the in-memory xfs_sb here
and not the on-disk xfs_dsb?

> +| +XFS_SB_FEAT_RO_COMPAT_RTSB+ |
> +Realtime superblock.  The first rt extent in rt group zero contains a superblock
> +header that can be used to identify the realtime device.  See the section about
> +the xref:Realtime_Group_Superblocks[realtime group superblocks] for more
> +information.

This is actually gone now.

> +*sb_rgcount*::
> +Count of realtime groups in the filesystem, if the
> ++XFS_SB_FEAT_INCOMPAT_RTGROUPS+ feature is enabled.

... will be zero if XFS_SB_FEAT_INCOMPAT_RTGROUPS is set, but no
realtime subvolume exists

?