linux-ext4 - Re: [PATCH v2 7/7] f2fs: Enable negative dentries on case-insensitive lookup

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Date:   Thu, 13 Jul 2023 22:49:24 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Gabriel Krisman Bertazi <krisman@...e.de>
Cc:     viro@...iv.linux.org.uk, brauner@...nel.org, tytso@....edu,
        jaegeuk@...nel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v2 7/7] f2fs: Enable negative dentries on
 case-insensitive lookup

On Fri, Apr 21, 2023 at 08:03:10PM -0400, Gabriel Krisman Bertazi wrote:
> From: Gabriel Krisman Bertazi <krisman@...labora.com>
> 
> Instead of invalidating negative dentries during case-insensitive
> lookups, mark them as such and let them be added to the dcache.
> d_ci_revalidate is able to properly filter them out if necessary based
> on the dentry casefold flag.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  fs/f2fs/namei.c | 23 ++---------------------
>  1 file changed, 2 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index 11fc4c8036a9..57ca7ea86509 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -564,17 +564,8 @@ static struct dentry *f2fs_lookup(struct inode *dir, struct dentry *dentry,
>  		goto out_iput;
>  	}
>  out_splice:
> -#if IS_ENABLED(CONFIG_UNICODE)
> -	if (!inode && IS_CASEFOLDED(dir)) {
> -		/* Eventually we want to call d_add_ci(dentry, NULL)
> -		 * for negative dentries in the encoding case as
> -		 * well.  For now, prevent the negative dentry
> -		 * from being cached.
> -		 */
> -		trace_f2fs_lookup_end(dir, dentry, ino, err);
> -		return NULL;
> -	}
> -#endif
> +	if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
> +		d_set_casefold_lookup(dentry);

I wonder if a more consistent place for the above code would be earlier in
f2fs_lookup(), next to the call to generic_set_encrypted_ci_d_ops()?  That's
where the dentry_operations are set.  It's also next to f2fs_prepare_lookup()
which is where DCACHE_NOKEY_NAME gets set if needed.

- Eric