Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754452AbZGAJcm (ORCPT ); Wed, 1 Jul 2009 05:32:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752868AbZGAJcd (ORCPT ); Wed, 1 Jul 2009 05:32:33 -0400 Received: from brick.kernel.dk ([93.163.65.50]:60103 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752837AbZGAJcc (ORCPT ); Wed, 1 Jul 2009 05:32:32 -0400 Date: Wed, 1 Jul 2009 11:32:35 +0200 From: Jens Axboe To: Shan Wei Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Jeff Moyer Subject: Re: [PATCH 2/2] cfq-iosched: get rid of the need for __GFP_FAIL in cfq_find_alloc_queue() Message-ID: <20090701093235.GX23611@kernel.dk> References: <1246007120-24034-1-git-send-email-jens.axboe@oracle.com> <1246007120-24034-3-git-send-email-jens.axboe@oracle.com> <4A4B2C3D.7090800@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A4B2C3D.7090800@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1840 Lines: 60 On Wed, Jul 01 2009, Shan Wei wrote: > Jens Axboe said: > > Setup an emergency fallback cfqq that we allocate at IO scheduler init > > time. If the slab allocation fails in cfq_find_alloc_queue(), we'll just > > punt IO to that cfqq instead. This ensures that cfq_find_alloc_queue() > > never fails without having to ensure free memory. > > > > Signed-off-by: Jens Axboe > > --- > > > > @@ -1740,11 +1745,8 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc, > > cfqq = *async_cfqq; > > } > > > > - if (!cfqq) { > > + if (!cfqq) > > cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask); > > - if (!cfqq) > > - return NULL; > > - } > > I jsut reviewed the code and found that the check of cfqq is also redundant > after doing cfq_get_queue() in cfq_set_request. > > The patch is based on Linus's main tree. It's not redundant in Linus' tree, cfq_get_queue() can return NULL for != __GFP_WAIT. > > Signed-off-by: Shan Wei > --- > block/cfq-iosched.c | 4 ---- > 1 files changed, 0 insertions(+), 4 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 833ec18..c373237 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -2307,10 +2307,6 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask) > cfqq = cic_to_cfqq(cic, is_sync); > if (!cfqq) { > cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask); > - > - if (!cfqq) > - goto queue_fail; > - > cic_set_cfqq(cic, cfqq, is_sync); > } > -- Jens Axboe -- 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/