linux-kernel - Re: [PATCH] fs: touch up predicts in putname()

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tn2kke5jquwjydr4hmi5h2adm4iio53yvsylmohxtebaazwcqy@i74mtkxq233x>
Date: Thu, 30 Oct 2025 14:59:25 +0100
From: Jan Kara <jack@...e.cz>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] fs: touch up predicts in putname()

On Wed 29-10-25 14:49:52, Mateusz Guzik wrote:
> 1. we already expect the refcount is 1.
> 2. path creation predicts name == iname
> 
> I verified this straightens out the asm, no functional changes.
> 
> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>

Looks sensible. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
> 
> random annoyance i noticed while profiling
> 
>  fs/namei.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index ba29ec7b67c5..4692f25e7cd9 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -282,7 +282,7 @@ void putname(struct filename *name)
>  		return;
>  
>  	refcnt = atomic_read(&name->refcnt);
> -	if (refcnt != 1) {
> +	if (unlikely(refcnt != 1)) {
>  		if (WARN_ON_ONCE(!refcnt))
>  			return;
>  
> @@ -290,7 +290,7 @@ void putname(struct filename *name)
>  			return;
>  	}
>  
> -	if (name->name != name->iname) {
> +	if (unlikely(name->name != name->iname)) {
>  		__putname(name->name);
>  		kfree(name);
>  	} else
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR