From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id EB76F7D00B for ; Tue, 28 Aug 2018 23:10:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727216AbeH2DE3 (ORCPT ); Tue, 28 Aug 2018 23:04:29 -0400 Received: from mail-it0-f65.google.com ([209.85.214.65]:51015 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727072AbeH2DE3 (ORCPT ); Tue, 28 Aug 2018 23:04:29 -0400 Received: by mail-it0-f65.google.com with SMTP id j81-v6so5115735ite.0; Tue, 28 Aug 2018 16:10:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5Gsh7+eKDb8jbcSjKNujBLc/+vJzu9XwrX6LuNtlNAQ=; b=E2pM7z1EhhMcRYKUNbVq3O94ZW6koRlaLZOSo5wCw983nV80RoAx39FwNtWWJH552Q dfcA8m8rZq6s3pGwHzr7M2dgN1fGmJcLdoeHRe2rteydjIaeda4klGJg2A04xaYcAvVG CeiebKFmliBZjE3PKj6RISdMxqfiepXLd0UgU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5Gsh7+eKDb8jbcSjKNujBLc/+vJzu9XwrX6LuNtlNAQ=; b=nvfpIrEHkXiJJb21sqM8TpLq5lkWU9Wrx1qzejYa7XriqPOzFhO8Pry2uKXXf1ne27 TiPaGIRsJXytEZbmTkNMgw944v6N17dWmIJGaY+pKnZB1zcJE20U1qxkWtTxOkZE9goi 9CxUDLK0mC9ewKhkd24q9+E7SXKxstdA/TiSOyDd3X+3G//BBq8mL5ZlVbYdUXOF+8Z8 agoo9pHeKuKSmfdVt0s40qic2UPTdJMnp+psdhiCb36yocUsodmnK+VfIWvkz9Vc0HQS cYQs2QSIrJbEhB9STyBHuJrFh4UI2uv+rPz9iPG3/HvlY1EejNDRFqJCJj99WVRZ7cX5 gp4Q== X-Gm-Message-State: APzg51CDqphK7Z3ZZwLj7Xl/5F4xsfbF+e6qTqzqUysiVfaf7B34Kn6L 6nM623GbPrz5qtaAWXeq7IpwPj/VzIuTBPpgXoQ= X-Google-Smtp-Source: ANB0VdYWqV0gGpaCuAZmXMTHIUX7a+qgmGQwviq8erYBjSjR34b16AWt17CaPcs07IDiaNqHakZNLN3ObprkMYYYgdA= X-Received: by 2002:a02:702:: with SMTP id f2-v6mr3430146jaf.70.1535497835163; Tue, 28 Aug 2018 16:10:35 -0700 (PDT) MIME-Version: 1.0 References: <1535476780-5773-1-git-send-email-longman@redhat.com> <1535476780-5773-3-git-send-email-longman@redhat.com> <20180828221352.GC11400@bombadil.infradead.org> <6873378b-3202-e738-2366-5fb818b4a013@redhat.com> In-Reply-To: <6873378b-3202-e738-2366-5fb818b4a013@redhat.com> From: Linus Torvalds Date: Tue, 28 Aug 2018 16:10:24 -0700 Message-ID: Subject: Re: [PATCH 2/2] fs/dcache: Make negative dentries easier to be reclaimed To: Waiman Long Cc: Matthew Wilcox , Al Viro , Jonathan Corbet , Linux Kernel Mailing List , linux-fsdevel , linux-mm , "open list:DOCUMENTATION" , "Luis R. Rodriguez" , Kees Cook , Jan Kara , Paul McKenney , Andrew Morton , Ingo Molnar , Miklos Szeredi , Larry Woodman , James Bottomley , "Wangkai (Kevin,C)" , Michal Hocko Content-Type: text/plain; charset="UTF-8" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tue, Aug 28, 2018 at 3:29 PM Waiman Long wrote: > > Yes, I can rewrite it. What is the problem with the abbreviated form? Either gcc rewrites it for you, or you end up _actually_ using a function pointer and calling through it. The latter would be absolutely horribly bad for something like "list_add()", which should expand to just a couple of instructions. And the former would be ok, except for the "you wrote code the garbage way, and then depended on the compiler fixing it up". Which we generally try to avoid in the kernel. (Don't get me wrong - we definitely depend on the compiler doing a good job at CSE and dead code elimination etc, but generally we try to avoid the whole "compiler has to rewrite code to be good" model). Linus