From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754901Ab0JOKER (ORCPT ); Fri, 15 Oct 2010 06:04:17 -0400 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:42540 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754421Ab0JOKEP (ORCPT ); Fri, 15 Oct 2010 06:04:15 -0400 Message-ID: <4CB82720.8040708@kernel.dk> Date: Fri, 15 Oct 2010 12:04:16 +0200 From: Jens Axboe MIME-Version: 1.0 To: Yasuaki Ishimatsu CC: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] blk: fix a wrong accounting of hd_struct->in_flight References: <4CB40281.1020403@jp.fujitsu.com> <4CB41A27.5080001@kernel.dk> <4CB6FC1C.3050801@jp.fujitsu.com> <4CB6FDB7.5010501@kernel.dk> <4CB8135E.1030100@jp.fujitsu.com> In-Reply-To: <4CB8135E.1030100@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2010-10-15 10:39, Yasuaki Ishimatsu wrote: > Hi Jens, > > Jens Axboe wrote: >> On 2010-10-14 14:48, Yasuaki Ishimatsu wrote: >>> Index: linux-2.6.36-rc7/block/blk-core.c >>> =================================================================== >>> --- linux-2.6.36-rc7.orig/block/blk-core.c 2010-10-07 05:39:52.000000000 +0900 >>> +++ linux-2.6.36-rc7/block/blk-core.c 2010-10-14 17:25:43.000000000 +0900 >>> @@ -66,9 +66,15 @@ static void drive_stat_acct(struct reque >>> cpu = part_stat_lock(); >>> part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq)); >>> >>> - if (!new_io) >>> + if (!new_io) { >>> + if (unlikely(rq->part != part)) { >>> + part_dec_in_flight(rq->part, rw); >>> + part_inc_in_flight(part, rw); >>> + rq->part = part; >>> + } >>> part_stat_inc(cpu, part, merges[rw]); >>> - else { >>> + } else { >>> + rq->part = part; >>> part_round_stats(cpu, part); >>> part_inc_in_flight(part, rw); >>> } >> >> I was thinking that we'd do away with the lookup always if ->part was >> already set. It will probably require a quiscing of IO on partition >> table reload, though. > > O.K. > I removed extra part lookups. Following patch also fixed a wrong accounting of > hd_struct->in_flight. But I could not invent how to stop IOs when > reloading partition table. Do you have some idea? This looks good! To quiesce the queue, something like the below. Completely untested. diff --git a/block/blk-core.c b/block/blk-core.c index 32a1c12..dce2f68 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -796,11 +796,16 @@ static struct request *get_request(struct request_queue *q, int rw_flags, rl->starved[is_sync] = 0; priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); - if (priv) + if (priv) { rl->elvpriv++; - if (blk_queue_io_stat(q)) - rw_flags |= REQ_IO_STAT; + /* + * Don't do stats for non-priv requests + */ + if (blk_queue_io_stat(q)) + rw_flags |= REQ_IO_STAT; + } + spin_unlock_irq(q->queue_lock); rq = blk_alloc_request(q, rw_flags, priv, gfp_mask); diff --git a/block/genhd.c b/block/genhd.c index 59a2db6..2ecbe7d 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -925,8 +925,10 @@ static void disk_free_ptbl_rcu_cb(struct rcu_head *head) { struct disk_part_tbl *ptbl = container_of(head, struct disk_part_tbl, rcu_head); + struct gendisk *disk = ptbl->disk; kfree(ptbl); + elv_quiesce_end(disk->queue); } /** @@ -949,6 +951,7 @@ static void disk_replace_part_tbl(struct gendisk *disk, if (old_ptbl) { rcu_assign_pointer(old_ptbl->last_lookup, NULL); + elv_quiesce_start(disk->queue); call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb); } } diff --git a/include/linux/genhd.h b/include/linux/genhd.h index 5f2f4c4..69b21bb 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -130,6 +130,7 @@ struct disk_part_tbl { struct rcu_head rcu_head; int len; struct hd_struct *last_lookup; + struct gendisk *disk; struct hd_struct *part[]; }; -- Jens Axboe