From mboxrd@z Thu Jan 1 00:00:00 1970 From: Davide Libenzi Subject: Re: [PATCH 18/23] vfs: Teach epoll to use file_hotplug_lock Date: Wed, 3 Jun 2009 17:50:01 -0700 (PDT) Message-ID: References: <1243893048-17031-18-git-send-email-ebiederm@xmission.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Al Viro , Linux Kernel Mailing List , linux-pci@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins , Tejun Heo , Alexey Dobriyan , Linus Torvalds , Alan Cox , Greg Kroah-Hartman , Nick Piggin , Andrew Morton , Christoph Hellwig , "Eric W. Biederman" To: "Eric W. Biederman" Return-path: In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 3 Jun 2009, Eric W. Biederman wrote: > What code are you talking about? > > To the open path a few memory writes and a smp_wmb. No atomics and no > spin lock/unlocks. > > Are you complaining because I retain the file_list? Sorry, did I overlook the patch? Weren't a couple of atomic ops and a spin lock/unlock couple present in __dentry_open() (same sort of the release path)? And that's only like 5% of the code touched by the new special handling of the file operations structure (basically, every f_op access ends up being wrapped by two atomic ops and other extra code). The question, that I'd like to reiterate is, is this stuff really needed? Anyway, my complaint ends here and I'll let others evaluate if merging this patchset is worth the cost. - Davide