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=-2.5 required=3.0 tests=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 1181EC4151A for ; Thu, 31 Jan 2019 09:51:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E251F218DA for ; Thu, 31 Jan 2019 09:51:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731784AbfAaJvj (ORCPT ); Thu, 31 Jan 2019 04:51:39 -0500 Received: from nautica.notk.org ([91.121.71.147]:52183 "EHLO nautica.notk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726316AbfAaJvj (ORCPT ); Thu, 31 Jan 2019 04:51:39 -0500 Received: by nautica.notk.org (Postfix, from userid 1001) id DAA5DC009; Thu, 31 Jan 2019 10:51:36 +0100 (CET) Date: Thu, 31 Jan 2019 10:51:21 +0100 From: Dominique Martinet To: Michal Hocko , Josh Snyder Cc: Vlastimil Babka , Andrew Morton , Linus Torvalds , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Peter Zijlstra , Greg KH , Jann Horn , Jiri Kosina , Andy Lutomirski , Dave Chinner , Kevin Easton , Matthew Wilcox , Cyril Hrubis , Tejun Heo , "Kirill A . Shutemov" , Daniel Gruss , Jiri Kosina Subject: Re: [PATCH 1/3] mm/mincore: make mincore() more conservative Message-ID: <20190131095121.GA26131@nautica> References: <20190130124420.1834-1-vbabka@suse.cz> <20190130124420.1834-2-vbabka@suse.cz> <20190131094357.GQ18811@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190131094357.GQ18811@dhcp22.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michal Hocko wrote on Thu, Jan 31, 2019: > > Change the semantics of mincore() so that it only reveals pagecache information > > for non-anonymous mappings that belog to files that the calling process could > > (if it tried to) successfully open for writing. > > I agree that this is a better way than the original 574823bfab82 > ("Change mincore() to count "mapped" pages rather than "cached" pages"). > One thing is still not clear to me though. Is the new owner/writeable > check OK for the Netflix-like usecases? I mean does happycache have > appropriate access to the cache data? I have tried to re-read the > original thread but couldn't find any confirmation. It's enough for my use cases and Josh didn't seem to oppose, but since he's not in Cc I don't think he would answer -- added him now :) FWIW happycache writes in the current directory by default so I assume in the way they use it it would usually have access one way or another. > If this still doesn't help happycache kind of workloads then we should > add a capability check IMO but this looks like a decent foundation to > me. the inode_owner_or_capable/inode_permission helpers already do allow quite a few capabilities there -- Dominique