linux-kernel - Re: [PATCH v2 10/13] xfs: Unmap blocks according to forcealign

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Message-ID: <Zo0JghFEaqxBs41l@dread.disaster.area>
Date: Tue, 9 Jul 2024 19:57:22 +1000
From: Dave Chinner <david@...morbit.com>
To: Christoph Hellwig <hch@....de>
Cc: John Garry <john.g.garry@...cle.com>, chandan.babu@...cle.com,
	djwong@...nel.org, dchinner@...hat.com, viro@...iv.linux.org.uk,
	brauner@...nel.org, jack@...e.cz, linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	catherine.hoang@...cle.com, martin.petersen@...cle.com
Subject: Re: [PATCH v2 10/13] xfs: Unmap blocks according to forcealign

On Sat, Jul 06, 2024 at 09:58:58AM +0200, Christoph Hellwig wrote:
> 
> > +			if (isforcealign) {
> > +				off = ip->i_extsize - mod;
> > +			} else {
> > +				ASSERT(isrt);
> > +				off = mp->m_sb.sb_rextsize - mod;
> > +			}
> 
> And we'll really need proper helpers so that we don't have to
> open code the i_extsize vs sb_rextsize logic all over.

We already have that: xfs_inode_alloc_unitsize().

Have the code get that value, then do all the alignment based on
whether it is allocation unit size > mp->m_sb.sb_blocksize. Then all
the calculations are generic and not dependent on forcealign or rt,
but on whether the inode requires multi-block contiguous extent
alignment....

i.e.
	alloc_size = xfs_inode_alloc_unitsize(ip);
	if (alloc_size > mp->m_sb.sb_blocksize) {
		/* do aligned allocation setup stuff */
		.....
	}
	....

No code should be doing "if (forcealign) ... else if (realtime) ..."
branching for alignment purposes. All the code should all be
generic based on the value xfs_inode_alloc_unitsize() returns.

-Dave.
-- 
Dave Chinner
david@...morbit.com