linux-kernel - Re: [PATCH 3/6] tracefs: dentry lookup crapectomy

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Message-ID: <20240131002346.GN2087318@ZenIV>
Date: Wed, 31 Jan 2024 00:23:46 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] tracefs: dentry lookup crapectomy

On Tue, Jan 30, 2024 at 11:03:52AM -0800, Linus Torvalds wrote:
>  {
>  	struct eventfs_inode *ei;
>  
> -	mutex_lock(&eventfs_mutex);
>  	do {
>  		// The parent is stable because we do not do renames
>  		dentry = dentry->d_parent;
> @@ -247,7 +246,6 @@ static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
>  		}
>  		// Walk upwards until you find the events inode
>  	} while (!ei->is_events);
> -	mutex_unlock(&eventfs_mutex);

Unless I'm missing something, you've just lost exclusion with
removals (not that the original hadn't been suspicious in that
respect - what's to protect ei past that mutex_unlock?