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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 1EBB5C43381 for ; Wed, 20 Feb 2019 03:46:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CED1C21738 for ; Wed, 20 Feb 2019 03:46:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ziepe.ca header.i=@ziepe.ca header.b="G/3NysBX" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730377AbfBTDqb (ORCPT ); Tue, 19 Feb 2019 22:46:31 -0500 Received: from mail-pl1-f178.google.com ([209.85.214.178]:33164 "EHLO mail-pl1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725916AbfBTDqb (ORCPT ); Tue, 19 Feb 2019 22:46:31 -0500 Received: by mail-pl1-f178.google.com with SMTP id y10so11503166plp.0 for ; Tue, 19 Feb 2019 19:46:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=sM/L3SAQWZpoMUv5GGkuvSzziV7oe/mKXTb644vHA/Y=; b=G/3NysBX65W59rB6IqhAWVdFozZJwOZhpqTiDRytr14Vn1fapUCyKUkB0XC6XZLEe0 xIBpcc+eh1Ny3GYetkv8livdit3eeEqmGi8zakWHgdRRUXUKCMyz30QJcTTgslWoeP2L vCRIVDCt6JIeoIRiqGTlnmyMW3uciAFj1B7PXA9zs8gqN2DgXrnImkwCmmuPwNKltr+i qAH+YpnkwiPPSrVY7kDNxfCRJYOi8M3Si0AKTfVrObi+mYlQWXJ+pWgEuTsJsnNKs4nu 3CXEmYtEx7z7PP8o1WwNmKuftmXTviuV4GUmVVkrC250GdjeH+grS2NkLu5GDLVTRYdd xA0Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=sM/L3SAQWZpoMUv5GGkuvSzziV7oe/mKXTb644vHA/Y=; b=jlT2lgx6EHfIEDjWY1Ie+2v/BLshdjnjaToXDbVBf27uGcc1gbV/wwlX8Q0XninnMF llYWcsZkBebxB0Ps5wdOLdmN+b5Bdb2gySHpHIsZ2sGsWFErbrX7NUEg4KqZWqJ4FMDr yCnB8bu8rcSWWM3bbqwbmhW0WaRQglbzE1m6x/FfqG4SN/oGQANjgOiCyxA0qNRg1EU4 reEefEOCluZ/jtOq3vN/dLpQCzNFFnNLKBQ4m1++pz/UqNp9vxUL53cY/rRbzpqSgish xgDp/Oj7JWU79QoYnLBBR1dxgeX09xbMndCDlSkYmctvgcbX1MaUieDn5GhGrg0M0XbU GeEw== X-Gm-Message-State: AHQUAub37SfB6jenJ7mKDcIZ5Wb4H6404LUw7AC9VopElOX5SVyQ7Imx FIr6av6ieclu8xgn9pgeOCY4fjjbzRtH5w== X-Google-Smtp-Source: AHgI3IZULUq2irryFoLNl35nPUygJAUThAqfYRnx+dBHWeNBkVGr8/QyxyeReUSzI7tD1CF/bkR52g== X-Received: by 2002:a17:902:298a:: with SMTP id h10mr34732953plb.312.1550634390130; Tue, 19 Feb 2019 19:46:30 -0800 (PST) Received: from ziepe.ca (S010614cc2056d97f.ed.shawcable.net. [174.3.196.123]) by smtp.gmail.com with ESMTPSA id b6sm1192124pfo.27.2019.02.19.19.46.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 Feb 2019 19:46:28 -0800 (PST) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1gwIq4-00029W-0N; Tue, 19 Feb 2019 20:46:28 -0700 Date: Tue, 19 Feb 2019 20:46:27 -0700 From: Jason Gunthorpe To: Matthew Wilcox Cc: linux-kernel@vger.kernel.org Subject: Re: xarray reserve/release? Message-ID: <20190220034627.GA564@ziepe.ca> References: <20190219235349.GA17351@ziepe.ca> <20190220012609.GC12668@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190220012609.GC12668@bombadil.infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 19, 2019 at 05:26:09PM -0800, Matthew Wilcox wrote: > On Tue, Feb 19, 2019 at 04:53:49PM -0700, Jason Gunthorpe wrote: > > Hey Matt, > > > > Did you intend that xa_release doesn't work on allocating arrays: > > That surprises me. I'll take a look in the morning. I think the issue is that this: static inline void xa_release(struct xarray *xa, unsigned long index) { xa_cmpxchg(xa, index, NULL, NULL, 0); relies on the NULL actually being xas_store(NULL), but cmpxchg transforms it into xas_store(XA_ZERO_ENTRY) when allocating.. So xa_reserve(), xa_release() and xa_cmpxchg() all do the same thing for allocating arrays. Perhaps this: void __xa_release(struct xarray *xa, unsigned long index) { XA_STATE(xas, xa, index); void *curr; curr = xas_load(&xas); if (curr == XA_ZERO_ENTRY) xas_store(&xas, NULL); } ? Also, I wonder if xa_reserve() is better written as as xa_cmpxchg(xa, index, NULL, XA_ZERO_ENTRY) Bit clearer what is going on.. Jason