From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8EC91C433E0 for ; Mon, 25 May 2020 11:31:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AA0220787 for ; Mon, 25 May 2020 11:31:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ZUcgqvbe" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390379AbgEYLbG (ORCPT ); Mon, 25 May 2020 07:31:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390364AbgEYLbD (ORCPT ); Mon, 25 May 2020 07:31:03 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E0C29C061A0E; Mon, 25 May 2020 04:31:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=9XennrgwipSgDkcsh71JEE0YegAAd1Z7p+AJvSBp+LI=; b=ZUcgqvbe9pjXSixowq68xyD1+A jECWDJzEqXYVz4Tzq7adXDx4JV7G6zoRYEnkWuFdwWISGC6S79gzajY4IV0Cw9RPRF0ju56IXV7+j 88UNEit+PABKAihCehQT1F4/c26kP9Beb+a6kzS2EpKuZgO7dukDWVNp9gsDkW+xNa9sHwaIwFtgo 6c8d3/qF65NmYakyzeUO1P7HDhY4nDa+ee1+72qzGoXz0BWgsa1Rg+cFNYcTUkKEdM1hryKab0feC cPnX1kKw20Lq3g4Ar2809ZQSHVQjqhPtM45DIt4SWlwdrTU/PImnX6+oMwT5PIviCnQGmQdnQGaUd YQQO9bVQ==; Received: from [2001:4bb8:18c:5da7:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jdBJq-0002Y8-LA; Mon, 25 May 2020 11:30:59 +0000 From: Christoph Hellwig To: Jens Axboe Cc: Konstantin Khlebnikov , Minchan Kim , Nitin Gupta , dm-devel@redhat.com, linux-block@vger.kernel.org, drbd-dev@lists.linbit.com, linux-bcache@vger.kernel.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org Subject: [PATCH 14/16] block: remove rcu_read_lock() from part_stat_lock() Date: Mon, 25 May 2020 13:30:12 +0200 Message-Id: <20200525113014.345997-15-hch@lst.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200525113014.345997-1-hch@lst.de> References: <20200525113014.345997-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Konstantin Khlebnikov The RCU lock is required only in disk_map_sector_rcu() to lookup the partition. After that request holds reference to related hd_struct. Replace get_cpu() with preempt_disable() - returned cpu index is unused. Signed-off-by: Konstantin Khlebnikov [hch: rebased] Signed-off-by: Christoph Hellwig --- block/genhd.c | 11 ++++++++--- include/linux/part_stat.h | 4 ++-- 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/block/genhd.c b/block/genhd.c index 3e7df0a3e6bb0..1a76593276644 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -321,11 +321,12 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector) struct hd_struct *part; int i; + rcu_read_lock(); ptbl = rcu_dereference(disk->part_tbl); part = rcu_dereference(ptbl->last_lookup); if (part && sector_in_part(part, sector) && hd_struct_try_get(part)) - return part; + goto out_unlock; for (i = 1; i < ptbl->len; i++) { part = rcu_dereference(ptbl->part[i]); @@ -339,10 +340,14 @@ struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector) if (!hd_struct_try_get(part)) break; rcu_assign_pointer(ptbl->last_lookup, part); - return part; + goto out_unlock; } } - return &disk->part0; + + part = &disk->part0; +out_unlock: + rcu_read_unlock(); + return part; } /** diff --git a/include/linux/part_stat.h b/include/linux/part_stat.h index 6644197980b92..a6b0938ce82e9 100644 --- a/include/linux/part_stat.h +++ b/include/linux/part_stat.h @@ -21,8 +21,8 @@ struct disk_stats { * * part_stat_read() can be called at any time. */ -#define part_stat_lock() ({ rcu_read_lock(); get_cpu(); }) -#define part_stat_unlock() do { put_cpu(); rcu_read_unlock(); } while (0) +#define part_stat_lock() preempt_disable() +#define part_stat_unlock() preempt_enable() #define part_stat_get_cpu(part, field, cpu) \ (per_cpu_ptr((part)->dkstats, (cpu))->field) -- 2.26.2