From patchwork Thu Feb 9 15:54:17 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9564989 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id A44D16020C for ; Thu, 9 Feb 2017 15:54:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 93D1A284F9 for ; Thu, 9 Feb 2017 15:54:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 887DF28541; Thu, 9 Feb 2017 15:54:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F077E284F9 for ; Thu, 9 Feb 2017 15:54:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752997AbdBIPy1 (ORCPT ); Thu, 9 Feb 2017 10:54:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:37256 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751672AbdBIPy0 (ORCPT ); Thu, 9 Feb 2017 10:54:26 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 594EEAC5B; Thu, 9 Feb 2017 15:54:19 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id DBA2B1E09E8; Thu, 9 Feb 2017 16:54:17 +0100 (CET) Date: Thu, 9 Feb 2017 16:54:17 +0100 From: Jan Kara To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Tejun Heo , Dan Williams , Thiago Jung Bauermann , NeilBrown , Jan Kara Subject: Re: [PATCH 03/10] block: Revalidate i_bdev reference in bd_aquire() Message-ID: <20170209155417.GA15818@quack2.suse.cz> References: <20170209124433.2626-1-jack@suse.cz> <20170209124433.2626-4-jack@suse.cz> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20170209124433.2626-4-jack@suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu 09-02-17 13:44:26, Jan Kara wrote: > When a device gets removed, block device inode unhashed so that it is not > used anymore (bdget() will not find it anymore). Later when a new device > gets created with the same device number, we create new block device > inode. However there may be file system device inodes whose i_bdev still > points to the original block device inode and thus we get two active > block device inodes for the same device. They will share the same > gendisk so the only visible differences will be that page caches will > not be coherent and BDIs will be different (the old block device inode > still points to unregistered BDI). > > Fix the problem by checking in bd_acquire() whether i_bdev still points > to active block device inode and re-lookup the block device if not. That > way any open of a block device happening after the old device has been > removed will get correct block device inode. Thiago spotted a stupid bug in this patch (calling bd_forget() on bdev instead of inode). Fixed version is attached. Honza > > Signed-off-by: Jan Kara > --- > fs/block_dev.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 601b71b76d7f..360439373a66 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -1043,13 +1043,22 @@ static struct block_device *bd_acquire(struct inode *inode) > > spin_lock(&bdev_lock); > bdev = inode->i_bdev; > - if (bdev) { > + if (bdev && !inode_unhashed(bdev->bd_inode)) { > bdgrab(bdev); > spin_unlock(&bdev_lock); > return bdev; > } > spin_unlock(&bdev_lock); > > + /* > + * i_bdev references block device inode that was already shut down > + * (corresponding device got removed). Remove the reference and look > + * up block device inode again just in case new device got > + * reestablished under the same device number. > + */ > + if (bdev) > + bd_forget(bdev); > + > bdev = bdget(inode->i_rdev); > if (bdev) { > spin_lock(&bdev_lock); > -- > 2.10.2 > Acked-by: Tejun Heo From aaf612333753b948a96aebe4a2f8066ed45ef164 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 9 Feb 2017 12:16:30 +0100 Subject: [PATCH 03/10] block: Revalidate i_bdev reference in bd_aquire() When a device gets removed, block device inode unhashed so that it is not used anymore (bdget() will not find it anymore). Later when a new device gets created with the same device number, we create new block device inode. However there may be file system device inodes whose i_bdev still points to the original block device inode and thus we get two active block device inodes for the same device. They will share the same gendisk so the only visible differences will be that page caches will not be coherent and BDIs will be different (the old block device inode still points to unregistered BDI). Fix the problem by checking in bd_acquire() whether i_bdev still points to active block device inode and re-lookup the block device if not. That way any open of a block device happening after the old device has been removed will get correct block device inode. Signed-off-by: Jan Kara --- fs/block_dev.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index 601b71b76d7f..68e855fdce58 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1043,13 +1043,22 @@ static struct block_device *bd_acquire(struct inode *inode) spin_lock(&bdev_lock); bdev = inode->i_bdev; - if (bdev) { + if (bdev && !inode_unhashed(bdev->bd_inode)) { bdgrab(bdev); spin_unlock(&bdev_lock); return bdev; } spin_unlock(&bdev_lock); + /* + * i_bdev references block device inode that was already shut down + * (corresponding device got removed). Remove the reference and look + * up block device inode again just in case new device got + * reestablished under the same device number. + */ + if (bdev) + bd_forget(inode); + bdev = bdget(inode->i_rdev); if (bdev) { spin_lock(&bdev_lock); -- 2.10.2