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Date: Fri, 27 Feb 2026 14:52:33 +0100
From: hch <hch@lst.de>
To: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Cc: "djwong@kernel.org" <djwong@kernel.org>, hch <hch@lst.de>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"cem@kernel.org" <cem@kernel.org>
Subject: Re: [PATCH] xfs: add write pointer to xfs_rtgroup_geometry
Message-ID: <20260227135233.GA20671@lst.de>
References: <20260227030105.822728-2-wilfred.opensource@gmail.com> <20260227040619.GI13853@frogsfrogsfrogs> <dbda17987ff33a132da82b8635ac2a5c6ae01c78.camel@wdc.com>
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On Fri, Feb 27, 2026 at 05:16:39AM +0000, Wilfred Mallawa wrote:
> > > -	__u32 rg_reserved[27];	/* o: zero */
> > > +	__u32 rg_reserved0;	/* o: preserve alignment */
> > > +	__u64 rg_writepointer;  /* o: write pointer sector for
> > > zoned */
> > 
> > Hrm.  It's not possible to advance the write pointer less than a
> > single
> > xfs fsblock, right? 
> 
> I believe so, perhaps Christoph could chime in?

It's not possible.

> 
> > zoned rt requires rt groups, so that means the
> > write pointer within a rtgroup has to be a xfs_rgblock_t (32bit)
> > value,
> > so shouldn't this be a __u32 field?
> 
> I figured since this is currently returning a basic block offset
> (similar to a zone report from a zoned device), it *could* exceed a
> U32_MAX for larger zones (?). Does it seem more appropriate to return
> the xfs fsblock offset here instead?

No, the count of blocks in a zone is a xfs_rgblock_t, which is a
uint32_t.  So all group/zone relative addressing can and should use
32-bit types.