Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760157Ab0HLNnw (ORCPT ); Thu, 12 Aug 2010 09:43:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12492 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753579Ab0HLNnv (ORCPT ); Thu, 12 Aug 2010 09:43:51 -0400 From: Jeff Moyer To: Naoya Horiguchi Cc: Christoph Lameter , Andi Kleen , Andrew Morton , Mel Gorman , Wu Fengguang , "Jun'ichi Nomura" , linux-mm , LKML , Andrea Arcangeli Subject: Re: [RFC] [PATCH 2/4] dio: add page locking for direct I/O References: <1281432464-14833-1-git-send-email-n-horiguchi@ah.jp.nec.com> <20100812075323.GA6112@spritzera.linux.bs1.fc.nec.co.jp> <20100812075941.GD6112@spritzera.linux.bs1.fc.nec.co.jp> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Thu, 12 Aug 2010 09:42:21 -0400 In-Reply-To: <20100812075941.GD6112@spritzera.linux.bs1.fc.nec.co.jp> (Naoya Horiguchi's message of "Thu, 12 Aug 2010 16:59:41 +0900") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1728 Lines: 55 Naoya Horiguchi writes: > Basically it is user's responsibility to take care of race condition > related to direct I/O, but some events which are out of user's control > (such as memory failure) can happen at any time. So we need to lock and > set/clear PG_writeback flags in dierct I/O code to protect from data loss. Did you do any performance testing of this? If not, please do and report back. I'm betting users won't be pleased with the results. Cheers, Jeff > > Signed-off-by: Naoya Horiguchi > --- > fs/direct-io.c | 8 +++++++- > 1 files changed, 7 insertions(+), 1 deletions(-) > > diff --git a/fs/direct-io.c b/fs/direct-io.c > index 7600aac..0d0810d 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -439,7 +439,10 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio) > struct page *page = bvec[page_no].bv_page; > > if (dio->rw == READ && !PageCompound(page)) > - set_page_dirty_lock(page); > + set_page_dirty(page); > + if (dio->rw & WRITE) > + end_page_writeback(page); > + unlock_page(page); > page_cache_release(page); > } > bio_put(bio); > @@ -702,11 +705,14 @@ submit_page_section(struct dio *dio, struct page *page, > { > int ret = 0; > > + lock_page(page); > + > if (dio->rw & WRITE) { > /* > * Read accounting is performed in submit_bio() > */ > task_io_account_write(len); > + set_page_writeback(page); > } > > /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/