linux-kernel - Re: [PATCH v3 03/25] dcache: Enable lockless update of d

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Message-ID: <CA+55aFzRbOgBhmL3y=bgR=OakOH6RizVYD5XBc8aP9LzfMn8cA@mail.gmail.com>
Date:	Wed, 3 Jul 2013 13:37:25 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Waiman Long <Waiman.Long@...com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...hat.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	"Norton, Scott J" <scott.norton@...com>
Subject: Re: [PATCH v3 03/25] dcache: Enable lockless update of d_count in
 dentry structure

This patch grew a lot, and that seems to be mainly because of bad reasons.

I'd suggest dropping the whole
"lockref_ret_count()"/"lockref_ret_lock()" helpers, which cause all
the annoyance, and just make people use the members directly.

Then, just do

   #define d_lock d_lockref.lockref_lock

or similar, so that all the existing code just continues to work,
without the need for the syntactic changes:

-       spin_lock(&dentry->d_lock);
+       d_lock(dentry);

For d_count, we probably do need to have the wrapper macro:

  #define dentry_count(dentry)  ((dentry)->d_lockref.lockref_count)

and change the existing users of "dentry->d_count" to use that, but
there are fewer of those than there are of people taking the dentry
lock. And most of them are in fs/dcache.c and would be affected by
this set of patches anyway.

                  Linus
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