linux-kernel - Re: [PATCH] tracefs: Add d_delete to remove negative dentries

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Message-ID: <20250611173702.GL299672@ZenIV>
Date: Wed, 11 Jun 2025 18:37:02 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] tracefs: Add d_delete to remove negative dentries

On Wed, Jun 11, 2025 at 12:18:15PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.org>
> 
> If a lookup in tracefs is done on a file that does not exist, it leaves a
> dentry hanging around until memory pressure removes it. But eventfs
> dentries should hang around as when their ref count goes to zero, it
> requires more work to recreate it. For the rest of the tracefs dentries,
> they hang around as their dentry is used as a descriptor for the tracing
> system. But if a file lookup happens for a file in tracefs that does not
> exist, it should be deleted.
> 
> Add a .d_delete callback that checks if dentry->fsdata is set or not. Only
> eventfs dentries set fsdata so if it has content it should not be deleted
> and should hang around in the cache.
> 
> Reported-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Applied to #work.dcache