linux-kernel - Re: [PATCH v2] ext4: fix fast commit inode enqueueing during a full journal commit

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Message-ID: <20240528105203.2q4gxqz6amgvud4l@quack3>
Date: Tue, 28 May 2024 12:52:03 +0200
From: Jan Kara <jack@...e.cz>
To: Luis Henriques <luis.henriques@...ux.dev>
Cc: Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger@...ger.ca>,
	Harshad Shirwadkar <harshadshirwadkar@...il.com>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ext4: fix fast commit inode enqueueing during a full
 journal commit

On Tue 28-05-24 12:36:02, Jan Kara wrote:
> On Mon 27-05-24 16:48:24, Luis Henriques wrote:
> > On Mon 27 May 2024 09:29:40 AM +01, Luis Henriques wrote;
> > >>> +	/*
> > >>> +	 * Used to flag an inode as part of the next fast commit; will be
> > >>> +	 * reset during fast commit clean-up
> > >>> +	 */
> > >>> +	tid_t i_fc_next;
> > >>> +
> > >>
> > >> Do we really need new tid in the inode? I'd be kind of hoping we could use
> > >> EXT4_I(inode)->i_sync_tid for this - I can see we even already set it in
> > >> ext4_fc_track_template() and used for similar comparisons in fast commit
> > >> code.
> > >
> > > Ah, true.  It looks like it could be used indeed.  We'll still need a flag
> > > here, but a simple bool should be enough for that.
> > 
> > After looking again at the code, I'm not 100% sure that this is actually
> > doable.  For example, if I replace the above by
> > 
> > 	bool i_fc_next;
> > 
> > and set to to 'true' below:

Forgot to comment on this one: I don't think you even need 'bool i_fc_next'
- simply whenever i_sync_tid is greater than committing transaction's tid,
you move the inode to FC_Q_STAGING list in ext4_fc_cleanup().

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR