Re: [PATCH v2 3/4] fsnotify: count all objects with attached connectors

From: Jan Kara <jack@suse.cz>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jan Kara <jack@suse.cz>,
	Matthew Bobrowski <mbobrowski@mbobrowski.org>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2 3/4] fsnotify: count all objects with attached connectors
Date: Wed, 11 Aug 2021 13:37:41 +0200	[thread overview]
Message-ID: <20210811113741.GD14725@quack2.suse.cz> (raw)
In-Reply-To: <20210810151220.285179-4-amir73il@gmail.com>

On Tue 10-08-21 18:12:19, Amir Goldstein wrote:
> Rename s_fsnotify_inode_refs to s_fsnotify_connectors and count all
> objects with attached connectors, not only inodes with attached
> connectors.
> 
> This will be used to optimize fsnotify() calls on sb without any
> type of marks.
> 
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>

... just a minor nit below ...

> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 640574294216..d48d2018dfa4 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1507,8 +1507,8 @@ struct super_block {
>  	/* Number of inodes with nlink == 0 but still referenced */
>  	atomic_long_t s_remove_count;
>  
> -	/* Pending fsnotify inode refs */
> -	atomic_long_t s_fsnotify_inode_refs;
> +	/* Number of inode/mount/sb objects that are being watched */
> +	atomic_long_t s_fsnotify_connectors;

I've realized inode watches will be double-accounted because we increment
s_fsnotify_connectors both when attaching a connector and when grabbing
inode reference. It doesn't really matter and avoiding this would require
special treatment of inode connectors (we need to decrement
s_fsnotify_connectors only after dropping inode reference). So I'll just
reflect this in the comment here so that we don't forget.

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