From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 420F96B01F0 for ; Tue, 17 Aug 2010 05:40:12 -0400 (EDT) Date: Tue, 17 Aug 2010 11:40:08 +0200 From: Andi Kleen Subject: Re: [PATCH 0/9] Hugepage migration (v2) Message-ID: <20100817094007.GA18161@basil.fritz.box> References: <1281432464-14833-1-git-send-email-n-horiguchi@ah.jp.nec.com> <20100812075323.GA6112@spritzera.linux.bs1.fc.nec.co.jp> <20100816091935.GB3388@spritzera.linux.bs1.fc.nec.co.jp> <20100817023719.GC12736@spritzera.linux.bs1.fc.nec.co.jp> <20100817081817.GA28969@spritzera.linux.bs1.fc.nec.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100817081817.GA28969@spritzera.linux.bs1.fc.nec.co.jp> Sender: owner-linux-mm@kvack.org To: Naoya Horiguchi Cc: Christoph Lameter , Andi Kleen , Andrew Morton , Mel Gorman , Wu Fengguang , Jun'ichi Nomura , linux-mm , LKML List-ID: > When get_user_pages_fast() is called before try_to_unmap(), > direct I/O code increments refcount on the target page. > Because this refcount is not associated to the mapping, > migration code will find remaining refcounts after try_to_unmap() > unmaps all mappings. Then refcount check decides migration to fail, > so direct I/O is continued safely. This would imply that direct IO can make migration fail arbitarily. Also not good. Should we add some retries, at least for the soft offline case? -Andi -- ak@linux.intel.com -- Speaking for myself only. -- 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