From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754555Ab0C1M2b (ORCPT ); Sun, 28 Mar 2010 08:28:31 -0400 Received: from einhorn.in-berlin.de ([192.109.42.8]:48718 "EHLO einhorn.in-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754434Ab0C1M2a (ORCPT ); Sun, 28 Mar 2010 08:28:30 -0400 X-Envelope-From: stefanr@s5r6.in-berlin.de Message-ID: <4BAF4B49.9070308@s5r6.in-berlin.de> Date: Sun, 28 Mar 2010 14:27:53 +0200 From: Stefan Richter User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.8.1.23) Gecko/20100102 SeaMonkey/1.1.18 MIME-Version: 1.0 To: Arnd Bergmann CC: Jiri Kosina , Frederic Weisbecker , linux-kernel@vger.kernel.org, Matthew Wilcox , Thomas Gleixner , jblunck@suse.de, Alan Cox , Ingo Molnar , John Kacur Subject: Re: [GIT, RFC] Killing the Big Kernel Lock References: <201003242240.54907.arnd@arndb.de> <201003251438.59062.arnd@arndb.de> <4BAD4795.2040700@s5r6.in-berlin.de> <201003271537.40488.arnd@arndb.de> In-Reply-To: <201003271537.40488.arnd@arndb.de> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Arnd Bergmann wrote: > Your patches look good, but it would be helpful to also set .llseek = no_llseek > in the file operations, because that is much easier to grep for than > only the nonseekable_open. While it's technically a NOP on the presence of > nonseekable_open, it will help that I don't accidentally apply my patch on > top of yours. Sounds like a plan, but (a) if my .llseek = no_llseek and your .llseek = default_llseek are not within diff context range, you (or whoever else merges mine and yours) only get a compiler warning (Initializer entry defined twice) rather than a merge conflict which couldn't be missed, (b) there won't be a merge conflict in "BKL removal: mark remaining users as 'depends on BKL'". (c) While I don't mind adding more visual clutter to ieee1394/*, I prefer terse coding in firewire/*. How about I put my nonseekable_open additions into a release branch and send you a pull request after a few days exposure in linux-next? If you do not plan to respin your patch queue soon or at all, I could even let you pull a for-arnd branch with a semantically correct merge of yours and mine. General thoughts: ".llseek = NULL," so far meant "do the Right Thing on lseek() and friends, as far as the fs core can tell". Shouldn't we keep it that way? It's as close to other ".method = NULL," as it can get, which either mean "silently skip this method if it doesn't matter" (e.g. .flush) or "fail attempts to use this method with a fitting errno" (e.g. .write). Of course, as we have already seen with infiniband, firewire, ieee1394, .llseek = NULL is ambiguous in practice. Does the driver really want to use default_llseek, or should it rather use no_llseek and/or nonseekable_open, or should it even implement a dummy_llseek() { return 0; } which avoids the BKL but preserves ABI behaviour? This needs to be resolved for each and every case eventually, regardless of whether or when your addition of .llseek = default_llseek enters mainline. -- Stefan Richter -=====-==-=- --== ===-- http://arcgraph.de/sr/