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	Sat, 05 Jul 2025 00:19:14 +0000
Date: Sat, 5 Jul 2025 01:19:13 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Tingmao Wang <m@maowtm.org>
Cc: Eric Van Hensbergen <ericvh@kernel.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Latchesar Ionkov <lucho@ionkov.net>,
	Christian Schoenebeck <linux_oss@crudebyte.com>,
	v9fs@lists.linux.dev,
	=?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>,
	=?iso-8859-1?Q?G=FCnther?= Noack <gnoack@google.com>,
	linux-security-module@vger.kernel.org, Jan Kara <jack@suse.cz>,
	Amir Goldstein <amir73il@gmail.com>,
	Matthew Bobrowski <repnop@google.com>,
	linux-fsdevel@vger.kernel.org
Subject: Re: [RFC PATCH 1/6] fs/9p: Add ability to identify inode by path for
 .L
Message-ID: <20250705001913.GV1880847@ZenIV>
References: <cover.1743971855.git.m@maowtm.org>
 <e839a49e0673b12eb5a1ed2605a0a5267ff644db.1743971855.git.m@maowtm.org>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Sun, Apr 06, 2025 at 09:43:02PM +0100, Tingmao Wang wrote:

> +struct v9fs_ino_path *make_ino_path(struct dentry *dentry)
> +{
> +	struct v9fs_ino_path *path;
> +	size_t path_components = 0;
> +	struct dentry *curr = dentry;
> +	ssize_t i;
> +
> +	lockdep_assert_held_read(&v9fs_dentry2v9ses(dentry)->rename_sem);
> +
> +	rcu_read_lock();
> +
> +    /* Don't include the root dentry */
> +	while (curr->d_parent != curr) {
> +		path_components++;
> +		curr = curr->d_parent;
> +	}
> +	if (WARN_ON(path_components > SSIZE_MAX)) {
> +		rcu_read_unlock();
> +		return NULL;
> +	}
> +
> +	path = kmalloc(struct_size(path, names, path_components),
> +		       GFP_KERNEL);

Blocking allocation under rcu_read_lock().