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Message-ID: <2024102201-pummel-mournful-d349@gregkh>
Date: Tue, 22 Oct 2024 15:55:29 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Johannes Berg <johannes@...solutions.net>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH 1/2] debugfs: add small file operations for most files
On Tue, Oct 22, 2024 at 03:18:34PM +0200, Johannes Berg wrote:
> From: Johannes Berg <johannes.berg@...el.com>
>
> As struct file_operations is really big, but (most) debugfs
> files only use simple_open, read, write and perhaps seek, and
> don't need anything else, this wastes a lot of space for NULL
> pointers.
>
> Add a struct debugfs_short_fops and some bookkeeping code in
> debugfs so that users can use that with debugfs_create_file()
> using _Generic to figure out which function to use.
>
> Converting mac80211 to use it where possible saves quite a
> bit of space:
>
> 1010127 205064 1220 1216411 128f9b net/mac80211/mac80211.ko (before)
> 981199 205064 1220 1187483 121e9b net/mac80211/mac80211.ko (after)
> -------
> -28928 = ~28KiB
>
> With a marginal space cost in debugfs:
>
> 8701 550 16 9267 2433 fs/debugfs/inode.o (before)
> 25233 325 32 25590 63f6 fs/debugfs/file.o (before)
> 8914 558 16 9488 2510 fs/debugfs/inode.o (after)
> 25380 325 32 25737 6489 fs/debugfs/file.o (after)
> ---------------
> +360 +8
>
> (All on x86-64)
>
> A simple spatch suggests there are more than 300 instances,
> not even counting the ones hidden in macros like in mac80211,
> that could be trivially converted, for additional savings of
> about 240 bytes for each.
>
> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
I imagine you want to take this through the wireless tree for the second
patch, so feel free to do that and add:
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
thanks!
greg k-h
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