From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id A60946B04AF for ; Fri, 18 Aug 2017 17:34:54 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id z195so5720565wmz.8 for ; Fri, 18 Aug 2017 14:34:54 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id w67si1758920wme.175.2017.08.18.14.34.53 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 18 Aug 2017 14:34:53 -0700 (PDT) Date: Fri, 18 Aug 2017 14:34:50 -0700 From: Andrew Morton Subject: Re: [RFC PATCH] mm: fadvise: avoid fadvise for fs without backing device Message-Id: <20170818143450.7584a3f86abf96f4c43fccd0@linux-foundation.org> In-Reply-To: References: <20170818011023.181465-1-shakeelb@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Shakeel Butt Cc: Mel Gorman , Johannes Weiner , Hillf Danton , Vlastimil Babka , Hugh Dickins , Greg Thelen , Linux MM , LKML On Thu, 17 Aug 2017 18:20:17 -0700 Shakeel Butt wrote: > +linux-mm, linux-kernel > > On Thu, Aug 17, 2017 at 6:10 PM, Shakeel Butt wrote: > > The fadvise() manpage is silent on fadvise()'s effect on > > memory-based filesystems (shmem, hugetlbfs & ramfs) and pseudo > > file systems (procfs, sysfs, kernfs). The current implementaion > > of fadvise is mostly a noop for such filesystems except for > > FADV_DONTNEED which will trigger expensive remote LRU cache > > draining. This patch makes the noop of fadvise() on such file > > systems very explicit. > > > > However this change has two side effects for ramfs and one for > > tmpfs. First fadvise(FADV_DONTNEED) can remove the unmapped clean > > zero'ed pages of ramfs (allocated through read, readahead & read > > fault) and tmpfs (allocated through read fault). Also > > fadvise(FADV_WILLNEED) on create such clean zero'ed pages for > > ramfs. This change removes these two interfaces. > > It doesn't sound like a risky change to me, although perhaps someone is depending on the current behaviour for obscure reasons, who knows. What are the reasons for this change? Is the current behaviour causing some sort of problem for someone? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org