From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Ni Subject: Re: After reshaping raid1 to raid0 with bitmap, then stop md panic Date: Fri, 8 Aug 2014 03:34:06 -0400 (EDT) Message-ID: <1873811381.19925148.1407483246395.JavaMail.zimbra@redhat.com> References: <324320204.17911195.1407221719669.JavaMail.zimbra@redhat.com> <11051344.17913061.1407222186494.JavaMail.zimbra@redhat.com> <20140806163702.15592dc6@notabene.brown> <1783178354.19231525.1407405817606.JavaMail.zimbra@redhat.com> <20140807202913.570be307@notabene.brown> <20140808154506.544472c2@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140808154506.544472c2@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid@vger.kernel.org, Jes Sorensen List-Id: linux-raid.ids ----- Original Message ----- > From: "NeilBrown" > To: "Xiao Ni" > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" > Sent: Friday, August 8, 2014 1:45:06 PM > Subject: Re: After reshaping raid1 to raid0 with bitmap, then stop md panic > > On Thu, 7 Aug 2014 20:29:13 +1000 NeilBrown wrote: > > > On Thu, 7 Aug 2014 06:03:37 -0400 (EDT) Xiao Ni wrote: > > > > > > > > > > > ----- Original Message ----- > > > > From: "NeilBrown" > > > > To: "Xiao Ni" > > > > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" > > > > > > > > Sent: Wednesday, August 6, 2014 2:37:02 PM > > > > Subject: Re: After reshaping raid1 to raid0 with bitmap, then stop md > > > > panic > > > > > > > > On Tue, 5 Aug 2014 03:03:06 -0400 (EDT) Xiao Ni wrote: > > > > > > > > > Dear all > > > > > > > > > > > > > > > I faced one problem that the system panic after reshaping raid1 to > > > > > raid0 > > > > > with bitmap. > > > > > The dmesg and calltrace information is like this: > > > > > > > > > > You can easily reproduce this by those steps: > > > > > 1. mdadm -CR /dev/md0 -l1 -n2 /dev/loop[0-1] --bitmap=internal > > > > > 2. mdadm --wait /dev/md0 > > > > > 3. mdadm --grow -l0 /dev/md0 > > > > > 4. mdadm -S /dev/md0 > > > > ... > > > > > > > > > > [ 1485.646746] BUG: unable to handle kernel NULL pointer dereference > > > > > at > > > > > 0000000000000038 > > > > > [ 1485.654724] IP: [] > > > > > bitmap_daemon_work+0x24e/0x450 > > > > > > > > Yes, RAID0 doesn't support bitmaps, so this cannot possibly work. > > > > > > > > Following patch should turn the crash into a clean failure. > > > > > > > > Thanks for the report, > > > > NeilBrown > > > > > > > > > > > > From 1bdb20e16166240a4ca3b861c48defefaf218874 Mon Sep 17 00:00:00 2001 > > > > From: NeilBrown > > > > Date: Wed, 6 Aug 2014 16:34:27 +1000 > > > > Subject: [PATCH] md: check for bitmap compatability when changing raid > > > > levels. > > > > > > > > If an array has a bitmap, then it cannot be converted to > > > > a level which does not support bitmaps. > > > > > > > > Reported-by: Xiao Ni > > > > Signed-off-by: NeilBrown > > > > > > > > diff --git a/drivers/md/md.c b/drivers/md/md.c > > > > index 1379b1a3b9ff..3bd13b276e45 100644 > > > > --- a/drivers/md/md.c > > > > +++ b/drivers/md/md.c > > > > @@ -3500,6 +3500,12 @@ level_store(struct mddev *mddev, const char > > > > *buf, > > > > size_t len) > > > > mdname(mddev), clevel); > > > > return -EINVAL; > > > > } > > > > + if (mddev->bitmap && !pers->quiesce) { > > > > + module_put(pers->owner); > > > > + printk(KERN_WARNING "md: %s: %s does not support a bitmap\n", > > > > + mdname(mddev), clevel); > > > > + return -EINVAL; > > > > + } > > > > > > > > rdev_for_each(rdev, mddev) > > > > rdev->new_raid_disk = rdev->raid_disk; > > > > > > > > > > Hi Neil > > > > > > I have tried the patch, but it can reshape to raid0 still, then stop > > > the raid0, the system > > > panics. > > > > > > What does pers->quiesce mean? I'm not familiar with md code. > > > > > > Best Regards > > > Xiao > > > > > > "quiesce" is a function that makes the array "quiescent" - it stops all IO > > from happening. > > The set_bitmap_file() function has: > > > > if (mddev->pers) { > > if (!mddev->pers->quiesce) > > return -EBUSY; > > > > > > So I thought it was safe to assume that if there was a quiesce function > > then > > the personality handled bitmaps. Obviously not. > > I'll have to fix that up... > > Can you confirm that this works please? > Thanks. > > NeilBrown > > From a8461a61c241a25afedbe493c13d98a6e0cf4246 Mon Sep 17 00:00:00 2001 > From: NeilBrown > Date: Wed, 6 Aug 2014 16:34:27 +1000 > Subject: [PATCH] md/raid0: check for bitmap compatability when changing raid > levels. > > If an array has a bitmap, then it cannot be converted to raid0. > > Reported-by: Xiao Ni > Signed-off-by: NeilBrown > > diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c > index 407a99e46f69..cf91f5910c7c 100644 > --- a/drivers/md/raid0.c > +++ b/drivers/md/raid0.c > @@ -685,6 +685,12 @@ static void *raid0_takeover(struct mddev *mddev) > * raid10 - assuming we have all necessary active disks > * raid1 - with (N -1) mirror drives faulty > */ > + > + if (mddev->bitmap) { > + printk(KERN_ERR "md/raid0: %s: cannot takeover array with bitmap\n", > + mdname(mddev)); > + return ERR_PTR(-EBUSY); > + } > if (mddev->level == 4) > return raid0_takeover_raid45(mddev); > > > > Hi Neil The problem can be fixed by this patch. Best Regards Xiao