From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-f198.google.com (mail-lb0-f198.google.com [209.85.217.198]) by kanga.kvack.org (Postfix) with ESMTP id E2AF56B0005 for ; Fri, 17 Jun 2016 12:55:55 -0400 (EDT) Received: by mail-lb0-f198.google.com with SMTP id nq2so2216977lbc.3 for ; Fri, 17 Jun 2016 09:55:55 -0700 (PDT) Received: from radon.swed.at (b.ns.miles-group.at. [95.130.255.144]) by mx.google.com with ESMTPS id m192si400397wma.13.2016.06.17.09.55.54 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 17 Jun 2016 09:55:54 -0700 (PDT) Subject: Re: [PATCH 1/3] mm: Don't blindly assign fallback_migrate_page() References: <1466112375-1717-1-git-send-email-richard@nod.at> <1466112375-1717-2-git-send-email-richard@nod.at> <20160616161121.35ee5183b9ef9f7b7dcbc815@linux-foundation.org> <5763A9B2.8060303@nod.at> <20160617162803.GK21670@dhcp22.suse.cz> From: Richard Weinberger Message-ID: <57642B91.4020206@nod.at> Date: Fri, 17 Jun 2016 18:55:45 +0200 MIME-Version: 1.0 In-Reply-To: <20160617162803.GK21670@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , 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, 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 Am 17.06.2016 um 18:28 schrieb Michal Hocko: > But doesn't this disable the page migration and so potentially reduce > the compaction success rate for the large pile of filesystems? Without > any hint about that? The WARN_ON_ONCE() is the hint. ;) But I can understand your point we'd have to communicate that change better. > $ git grep "\.migratepage[[:space:]]*=" -- fs | wc -l > 16 > out of > $ git grep "struct address_space_operations[[:space:]]*[a-zA-Z0-9_]*[[:space:]]*=" -- fs | wc -l > 87 > > That just seems to be too conservative for something that even not might > be a problem, especially when considering the fallback migration code is > there for many years with only UBIFS seeing a problem. UBIFS is also there for many years. It just shows that the issue is hard to hit but at least for UBIFS it is real. > Wouldn't it be safer to contact FS developers who might have have > similar issue and work with them to use a proper migration code? That was the goal of this patch. Forcing the filesystem developers to look as the WARN_ON_ONCE() triggered. I fear just sending a mail to linux-fsdevel@vger is not enough. Thanks, //richard -- 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