linux-ext4 - Re: [PATCH v6 02/10] ext4: for committing inode, make ext4_fc_track

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Message-ID: <20240628144555.6a2jdc4d2lmbfiy7@quack3>
Date: Fri, 28 Jun 2024 16:45:55 +0200
From: Jan Kara <jack@...e.cz>
To: Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, saukad@...gle.com,
	harshads@...gle.com
Subject: Re: [PATCH v6 02/10] ext4: for committing inode, make
 ext4_fc_track_inode wait

On Wed 29-05-24 01:19:55, Harshad Shirwadkar wrote:
> If the inode that's being requested to track using ext4_fc_track_inode
> is being committed, then wait until the inode finishes the
> commit. Also, add calls to ext4_fc_track_inode at the right places.
> 
> With this patch, now calling ext4_reserve_inode_write() results in
> inode being tracked for next fast commit. A subtle lock ordering
> requirement with i_data_sem (which is documented in the code) requires
> that ext4_fc_track_inode() be called before grabbing i_data_sem. So,
> this patch also adds explicit ext4_fc_track_inode() calls in places
> where i_data_sem grabbed.
> 
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@...il.com>

One more thing I've noticed:

> @@ -5727,6 +5730,7 @@ ext4_reserve_inode_write(handle_t *handle, struct inode *inode,
>  			brelse(iloc->bh);
>  			iloc->bh = NULL;
>  		}
> +		ext4_fc_track_inode(handle, inode);
>  	}
>  	ext4_std_error(inode->i_sb, err);
>  	return err;

Calling ext4_fc_track_inode() when ext4_get_write_access() failed is
pointless (inode isn't going to be written) and confusing. We should do
that only in the success case.

								Honza

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