From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754098AbcFPXLY (ORCPT ); Thu, 16 Jun 2016 19:11:24 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38831 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbcFPXLX (ORCPT ); Thu, 16 Jun 2016 19:11:23 -0400 Date: Thu, 16 Jun 2016 16:11:21 -0700 From: Andrew Morton To: Richard Weinberger Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, hannes@cmpxchg.org, mgorman@techsingularity.net, n-horiguchi@ah.jp.nec.com, mhocko@suse.com, kirill.shutemov@linux.intel.com, hughd@google.com, vbabka@suse.cz, adrian.hunter@intel.com, dedekind1@gmail.com, hch@infradead.org, linux-fsdevel@vger.kernel.org, boris.brezillon@free-electrons.com, maxime.ripard@free-electrons.com, david@sigma-star.at, david@fromorbit.com, alex@nextthing.co, sasha.levin@oracle.com, iamjoonsoo.kim@lge.com, rvaswani@codeaurora.org, tony.luck@intel.com, shailendra.capricorn@gmail.com Subject: Re: [PATCH 1/3] mm: Don't blindly assign fallback_migrate_page() Message-Id: <20160616161121.35ee5183b9ef9f7b7dcbc815@linux-foundation.org> In-Reply-To: <1466112375-1717-2-git-send-email-richard@nod.at> References: <1466112375-1717-1-git-send-email-richard@nod.at> <1466112375-1717-2-git-send-email-richard@nod.at> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 16 Jun 2016 23:26:13 +0200 Richard Weinberger wrote: > While block oriented filesystems use buffer_migrate_page() > as page migration function other filesystems which don't > implement ->migratepage() will automatically get fallback_migrate_page() > assigned. fallback_migrate_page() is not as generic as is should > be. Page migration is filesystem specific and a one-fits-all function > is hard to achieve. UBIFS leaned this lection the hard way. > It uses various page flags and fallback_migrate_page() does not > handle these flags as UBIFS expected. > > To make sure that no further filesystem will get confused by > fallback_migrate_page() disable the automatic assignment and > allow filesystems to use this function explicitly if it is > really suitable. hm, is there really much point in doing this? I assume it doesn't actually affect any current filesystems? [2/3] is of course OK - please add it to the UBIFS tree.