linux-kernel - Re: [PATCH] fs: unconditionally use atime_needs_update() in pick

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Message-ID: <ygscd5g4qhpkekidplxvwprtxf34gc3aylohxsk5qr2meehk33@n54hljzo53y7>
Date: Tue, 8 Apr 2025 14:07:48 +0200
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: unconditionally use atime_needs_update() in
 pick_link()

On Tue 08-04-25 09:36:41, Mateusz Guzik wrote:
> Vast majority of the time the func returns false.
> 
> This avoids a branch to determine whether we are in RCU mode.
> 
> Signed-off-by: Mateusz Guzik <mjguzik@...il.com>

Looks good! Feel free to add:

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

								Honza

> ---
>  fs/namei.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 360a86ca1f02..ae2643ff14dc 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1905,13 +1905,13 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
>  			unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
>  		return ERR_PTR(-ELOOP);
>  
> -	if (!(nd->flags & LOOKUP_RCU)) {
> +	if (unlikely(atime_needs_update(&last->link, inode))) {
> +		if (nd->flags & LOOKUP_RCU) {
> +			if (!try_to_unlazy(nd))
> +				return ERR_PTR(-ECHILD);
> +		}
>  		touch_atime(&last->link);
>  		cond_resched();
> -	} else if (atime_needs_update(&last->link, inode)) {
> -		if (!try_to_unlazy(nd))
> -			return ERR_PTR(-ECHILD);
> -		touch_atime(&last->link);
>  	}
>  
>  	error = security_inode_follow_link(link->dentry, inode,
> -- 
> 2.43.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR