From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70748C433FF for ; Sun, 11 Aug 2019 01:22:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 463FD208C4 for ; Sun, 11 Aug 2019 01:22:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="AaoGjcrC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726233AbfHKBW3 (ORCPT ); Sat, 10 Aug 2019 21:22:29 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:49272 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726084AbfHKBW3 (ORCPT ); Sat, 10 Aug 2019 21:22:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=x9UEbmW8LJ0lIKjMLHktJ3/c30NE8tEZXrlgaJFgkVE=; b=AaoGjcrC0WoqO1MfO2CSTnPGI xpj5lAq2Y9Wl0X5d3XzIXj3RgldrNnIh4XMTJiD/QAm3PVyJZ54O6o7Atg95xOKR/0I0M6yHNVKDm QPphw1ZfIX/DEd0Wua3oKgObE8pkvmnCc4JzacvdJH31NfDgA8slYqhUV+VBVweS4WwG2olbBZg/y oSgCW4Zwm5pWwrkAqnxUJ6OzyeHs1Es78Bofj4n8UOQYPGyA44gskjjjq7g5TspMpIVABjMg3gcDI 1f1enarGTp5f/nRmn8ovSkuYCzxjfQYN360kMEJ0FEJtgsk96eqIti+H2WX1IIFfVEyZO0nGsqGaf PJz9fm00g==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hwcYv-0004on-1g; Sun, 11 Aug 2019 01:22:21 +0000 Date: Sat, 10 Aug 2019 18:22:20 -0700 From: Matthew Wilcox To: Christoph Hellwig Cc: Thomas Gleixner , LKML , Peter Zijlstra , Ingo Molnar , Sebastian Siewior , Anna-Maria Gleixner , Steven Rostedt , Julia Cartwright , Jan Kara , Theodore Tso , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Jan Kara , Mark Fasheh , Joseph Qi , Joel Becker Subject: Re: [patch V2 0/7] fs: Substitute bit-spinlocks for PREEMPT_RT and debugging Message-ID: <20190811012220.GB7491@bombadil.infradead.org> References: <20190801010126.245731659@linutronix.de> <20190802075612.GA20962@infradead.org> <20190806061119.GA17492@infradead.org> <20190808072807.GA25259@infradead.org> <20190810081834.GB30426@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190810081834.GB30426@infradead.org> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Sat, Aug 10, 2019 at 01:18:34AM -0700, Christoph Hellwig wrote: > On Thu, Aug 08, 2019 at 09:54:03AM +0200, Thomas Gleixner wrote: > > > I know. But the problem here is that normally PG_locked is used together > > > with wait_on_page_bit_*, but this one instances uses the bit spinlock > > > helpers. This is the equivalent of calling spin_lock on a struct mutex > > > rather than having a mutex_lock_spin helper for this case. > > > > Yes, I know :( > > But this means we should exclude slub from the bit_spin_lock removal. > It really should use it's own version of it anyhow insted of pretending > that the page lock is a bit spinlock. But PG_locked isn't used as a mutex _when the page is allocated by slab_. Yes, every other user uses PG_locked as a mutex, but I don't see why that should constrain slub's usage of PG_locked.