From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:34638 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751935AbaCGPs7 (ORCPT ); Fri, 7 Mar 2014 10:48:59 -0500 Received: from acsinet22.oracle.com (acsinet22.oracle.com [141.146.126.238]) by userp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id s27Fmvwk016020 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 7 Mar 2014 15:48:58 GMT Received: from aserz7021.oracle.com (aserz7021.oracle.com [141.146.126.230]) by acsinet22.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s27FmvaI010338 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 7 Mar 2014 15:48:57 GMT Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by aserz7021.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s27FmvXY005865 for ; Fri, 7 Mar 2014 15:48:57 GMT From: Anand Jain To: linux-btrfs@vger.kernel.org Subject: [PATCH 1/3 v2 RFC] btrfs: total_devices vs num_devices Date: Fri, 7 Mar 2014 23:48:37 +0800 Message-Id: <1394207319-13252-1-git-send-email-Anand.Jain@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: The intended usage of total_devices and num_devices should be recorded in the comments so that these two counters can be used correctly as originally intended. As of now there appears to be slight deviations/bugs from the original intention, the bugs are apparent that num_devices does not count seed devices where as total_devices does, but total_devices does not count the replacing devices where as num_devices does. So in this situation the ioctl(BTRFS_IOC_DEVICES_READY) will fails when there is seed FS. Next, applications using ioctl(BTRFS_IOC_FS_INFO) and ioctl(BTRFS_IOC_DEV_INFO) in conjunction to allocate the slots will also fail as former depend on the num_devices where as latter would match total_devices (except when replace is running). This patch will help have the clarity on usage of these two counter so that bugs related to this can be fixed. Signed-off-by: Anand Jain --- v2: edit commit fs/btrfs/volumes.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 91b7596..99c71aa 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -121,12 +121,18 @@ struct btrfs_fs_devices { /* the device with this id has the most recent copy of the super */ u64 latest_devid; u64 latest_trans; + /* num_devices contains run time count of devices which are part + * of this FSID. (the FS devices + replacing devices + ? + */ u64 num_devices; u64 open_devices; u64 rw_devices; u64 missing_devices; u64 total_rw_bytes; u64 num_can_discard; + /* total_devices contains static recorded count of device which + * are part of this FSID. (the FS devices + seed devices + ? + */ u64 total_devices; struct block_device *latest_bdev; -- 1.8.5.3