linux-kernel - Re: [PATCH] btrfs: remove EXTENT_BUFFER_IN

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Message-ID: <20250318171605.GJ32661@suse.cz>
Date: Tue, 18 Mar 2025 18:16:05 +0100
From: David Sterba <dsterba@...e.cz>
To: Daniel Vacek <neelx@...e.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
Subject: Re: [PATCH] btrfs: remove EXTENT_BUFFER_IN_TREE flag

On Tue, Mar 18, 2025 at 06:07:20PM +0100, Daniel Vacek wrote:
> On Tue, 18 Mar 2025 at 16:45, David Sterba <dsterba@...e.cz> wrote:
> >
> > On Tue, Mar 18, 2025 at 10:54:38AM +0100, Daniel Vacek wrote:
> > > This flag is set after inserting the eb to the buffer tree and cleared on
> > > it's removal. But it does not bring any added value. Just kill it for good.
> >
> > Would be good to add the reference to commit that added the bit,
> > 34b41acec1ccc0 ("Btrfs: use a bit to track if we're in the radix tree")
> > and wanted to make use of it, faa2dbf004e89e ("Btrfs: add sanity tests
> > for new qgroup accounting code"). And both are 10+ years old.
> 
> Right, I could have checked the history.
> 
> Though honestly from the diff of these two commits I don't see any
> valid usage of this flag either. Must have been somewhere in the
> context or I'm missing something.

Yeah, from the diff it can be seen if the code has any effects. It's
recommended to analyze the code also from the historical context because
it can be a leftover from a cleanup (and most of the time it is), but
there's still a chance the initial intentions of the code are still
valid and it was the cleanup that broke it.