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Message-ID: <Z5QfFLaywTAdmHoh@slm.duckdns.org>
Date: Fri, 24 Jan 2025 13:15:32 -1000
From: Tejun Heo <tj@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michal Koutný <mkoutny@...e.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Hillf Danton <hdanton@...a.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Marco Elver <elver@...gle.com>, Zefan Li <lizefan.x@...edance.com>,
	tglx@...utronix.de
Subject: Re: [PATCH v4 4/6] kernfs: Don't re-lock kernfs_root::kernfs_rwsem
 in kernfs_fop_readdir().

Hello,

On Fri, Jan 24, 2025 at 06:46:12PM +0100, Sebastian Andrzej Siewior wrote:
...
> to avoid holding a global lock during a page fault. The lock drop is
> wrong since the support of renames and not a big burden since the lock
> is no longer global.

It's still a pretty big lock. Hopefully, at least name accesses can be
converted to rcu protected ones later?

> Don't re-acquire kernfs_root::kernfs_rwsem while copying the name to the
> userpace buffer.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun

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