From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:43617 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751789AbaEPOlx (ORCPT ); Fri, 16 May 2014 10:41:53 -0400 Message-ID: <53762456.3050005@oracle.com> Date: Fri, 16 May 2014 22:44:38 +0800 From: Anand Jain MIME-Version: 1.0 To: Wang Shilong , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: set right total device count for seeding support References: <1399971906-1237-1-git-send-email-wangsl.fnst@cn.fujitsu.com> <1399971906-1237-2-git-send-email-wangsl.fnst@cn.fujitsu.com> <53761D30.6080207@oracle.com> In-Reply-To: <53761D30.6080207@oracle.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Wang, when we unmount && mount (instead of remount) and followed with device del it ends up with null pointer deref at btrfs_shrink_dev. Thats because the btrfs_root is not set for seed disk as we mounted the writable sprout disk. I am writing a separate fix for that as its a new bug. Thanks, Anand On 16/05/14 22:14, Anand Jain wrote: > > Wang, > > There seems to be a problem - after we delete the seed > disk, the total_devices didn't decrement back to 1. > reproducer as in the below test case. (I used btrfs-devlist > (posted) to check fs_devices). > > > # mkfs.btrfs -f /dev/sdb > > # btrfstune -S 1 /dev/sdb > > # mount /dev/sdb /mnt > > # btrfs device add -f /dev/sdc /mnt --->fs_devices->total_devices = 1 > mount -o rw,remount /mnt > btrfs dev del /dev/sdb /mnt --> fs_devices->total_devices is still 2 > > Thanks, Anand > > > On 13/05/14 17:05, Wang Shilong wrote: >> Seeding device support allows us to create a new filesystem >> based on existed filesystem. >> >> However newly created filesystem's @total_devices should include seed >> devices. This patch fix the following problem: >> >> # mkfs.btrfs -f /dev/sdb >> # btrfstune -S 1 /dev/sdb >> # mount /dev/sdb /mnt >> # btrfs device add -f /dev/sdc /mnt --->fs_devices->total_devices = 1 >> # umount /mnt >> # mount /dev/sdc /mnt --->fs_devices->total_devices = 2 >> >> This is because we record right @total_devices in superblock, but >> @fs_devices->total_devices is reset to be 0 in btrfs_prepare_sprout(). >> >> Fix this problem by not resetting @fs_devices->total_devices. >> >> Signed-off-by: Wang Shilong >> --- >> fs/btrfs/volumes.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c >> index 6fd7fe6..19b2d32 100644 >> --- a/fs/btrfs/volumes.c >> +++ b/fs/btrfs/volumes.c >> @@ -1883,7 +1883,6 @@ static int btrfs_prepare_sprout(struct >> btrfs_root *root) >> fs_devices->seeding = 0; >> fs_devices->num_devices = 0; >> fs_devices->open_devices = 0; >> - fs_devices->total_devices = 0; >> fs_devices->seed = seed_devices; >> >> generate_random_uuid(fs_devices->fsid); >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html