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	Tue, 05 Aug 2025 05:08:09 +0000
Date: Tue, 5 Aug 2025 06:08:09 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: =?iso-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>, Amir Goldstein <amir73il@gmail.com>,
	Theodore Tso <tytso@mit.edu>,
	Gabriel Krisman Bertazi <krisman@kernel.org>,
	linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	kernel-dev@igalia.com
Subject: Re: [PATCH RFC v2 2/8] ovl: Create ovl_strcmp() with casefold support
Message-ID: <20250805050809.GA222315@ZenIV>
References: <20250805-tonyk-overlayfs-v2-0-0e54281da318@igalia.com>
 <20250805-tonyk-overlayfs-v2-2-0e54281da318@igalia.com>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Tue, Aug 05, 2025 at 12:09:06AM -0300, André Almeida wrote:

> +static int ovl_strcmp(const char *str, struct ovl_cache_entry *p, int len)

> +	if (p->map && !is_dot_dotdot(str, len)) {
> +		dst = kmalloc(OVL_NAME_LEN, GFP_KERNEL);

...`

> +	kfree(dst);
> +
> +	return cmp;
> +}
> +

> @@ -107,7 +145,7 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
>  	while (node) {
>  		struct ovl_cache_entry *p = ovl_cache_entry_from_node(node);
>  
> -		cmp = strncmp(name, p->name, len);
> +		cmp = ovl_strcmp(name, p, len);
>  		if (cmp > 0)
>  			node = p->node.rb_right;
>  		else if (cmp < 0 || len < p->len)

Am I misreading that, or do really we get a kmalloc()/kfree() for each
sodding tree node we traverse on rbtree lookup here?