From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:46527 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750849AbaDJHgI (ORCPT ); Thu, 10 Apr 2014 03:36:08 -0400 Message-ID: <53464A29.7090607@oracle.com> Date: Thu, 10 Apr 2014 15:37:13 +0800 From: Anand Jain MIME-Version: 1.0 To: Qu Wenruo CC: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs-progs: Force 'btrfs dev scan' not using old libblkid cache References: <1397115021-30426-1-git-send-email-quwenruo@cn.fujitsu.com> In-Reply-To: <1397115021-30426-1-git-send-email-quwenruo@cn.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 04/10/2014 03:30 PM, Qu Wenruo wrote: > 'btrfs scan' uses libblkid to scan devices by default, and libblkid uses > cache to reduce the probe. > > But if operations below is done in less than 2 seconds(BLKID_PROBE_MIN), > 'btrfs scan' will still use the uncorrect cache and scan on the deleted device. Great thanks for looking into this. Anand > 0. /dev/sda[1-4] mounted on /mnt using single data/metadata > 1. btrfs dev scan > 2. btrfs dev del /dev/sda3 /mnt > 3. btrfs dev scan > Since the cache made by step 1 is still validated, step 3 will use the > cache and consider /dev/sda3 as a btrfs filesystem and try to scan it. > But the superblock(at least the first one) is wiped and failed to scan, > a error message, which can be avoided and is unneeded, is output. > > This patch will force scan_for_btrfs() not to use cache to avoid the > problem. > > Reported-by: Tsutomu Itoh > Singed-off-by: Qu Wenruo > --- > utils.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/utils.c b/utils.c > index 0bfb9d9..1cd1d28 100644 > --- a/utils.c > +++ b/utils.c > @@ -2057,7 +2057,8 @@ int btrfs_scan_lblkid(int update_kernel) > blkid_cache cache = NULL; > char path[PATH_MAX]; > > - if (blkid_get_cache(&cache, 0) < 0) { > + /* No to use libblkid cache to avoid old data */ > + if (blkid_get_cache(&cache, "/dev/null") < 0) { > printf("ERROR: lblkid cache get failed\n"); > return 1; > } >