linux-ext4 - Re: [PATCH RFC 8/8] xfs: use super write guard in xfs_file

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Message-ID: <20251105174705.GB196358@frogsfrogsfrogs>
Date: Wed, 5 Nov 2025 09:47:05 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.cz>, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [PATCH RFC 8/8] xfs: use super write guard in xfs_file_ioctl()

On Tue, Nov 04, 2025 at 09:57:30PM +0100, Christian Brauner wrote:
> On Tue, Nov 04, 2025 at 09:08:45AM -0800, Darrick J. Wong wrote:
> > On Tue, Nov 04, 2025 at 01:12:37PM +0100, Christian Brauner wrote:
> > > Signed-off-by: Christian Brauner <brauner@...nel.org>
> > > ---
> > >  fs/xfs/xfs_ioctl.c | 6 ++----
> > >  1 file changed, 2 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> > > index a6bb7ee7a27a..f72e96f54cb5 100644
> > > --- a/fs/xfs/xfs_ioctl.c
> > > +++ b/fs/xfs/xfs_ioctl.c
> > > @@ -1408,10 +1408,8 @@ xfs_file_ioctl(
> > >  
> > >  		trace_xfs_ioc_free_eofblocks(mp, &icw, _RET_IP_);
> > >  
> > > -		sb_start_write(mp->m_super);
> > > -		error = xfs_blockgc_free_space(mp, &icw);
> > > -		sb_end_write(mp->m_super);
> > > -		return error;
> > > +		scoped_guard(super_write, mp->m_super)
> > > +			return xfs_blockgc_free_space(mp, &icw);
> > 
> > Can we go full on Java?
> > 
> > #define with_sb_write(sb) scoped_guard(super_write, (sb))
> > 
> > 	with_sb_write(mp->m_super)
> > 		return xfs_blockgc_free_space(mp, &icw);
> > 
> > I still keep seeing scoped_guard() as a function call, not the sort of
> > thing that starts a new block.
> > 
> > [If I missed the bikeshedding war over this, I'll let this go]
> 
> It's an option and what I did for the creds stuff. The thing is thought
> that scoped_guard() is more widespread by now and thus probably easier
> to grasp for readers that are familiar with it. I'm not married to it.

The wait_ macro would maintain sb_.*_write greppability, though I don't
know how important that might be.

--D