* [PATCH] Need update superblock on time when deciding to do reshape
@ 2016-05-17 8:54 Xiao Ni
2016-05-20 17:59 ` Shaohua Li
0 siblings, 1 reply; 6+ messages in thread
From: Xiao Ni @ 2016-05-17 8:54 UTC (permalink / raw)
To: shli; +Cc: linux-raid, Jes.Sorensen
Hi all
If the disks are not enough to have spaces for relocating the data_offset,
it needs to run start_reshape and then run mdadm --grow --continue by
systemd. But mdadm --grow --continue fails because it checkes that
info->reshape_active is 0.
The info->reshape_active is set to 1 when the superblock feature_map
have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
Function start_reshape calls raid5_start_reshape which changes
mddev->reshape_position to 0. Then in md_check_recovery it updates the
superblock to underlying devices. But there is a chance that the superblock
haven't written to underlying devices, the mdadm reads the superblock data.
So mdadm --grow --continue fails.
The steps to reproduce this:
mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
mdadm --wait /dev/md0
mdadm /dev/md0 -a /dev/loop3
mdadm --grow --raid-devices 4 /dev/md0
The loop device size is 500MB
[root@storageqe-09 ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
[>....................] reshape = 0.0% (1/510976) finish=0.0min speed=255488K/sec
bitmap: 1/1 pages [4KB], 65536KB chunk
unused devices: <none>
So if we update the superblock on time, mdadm can read the right superblock data.
Signed-off-by <xni@redhat.com>
---
drivers/md/md.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 14d3b37..7919606 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char *page, size_t len)
else {
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
err = mddev->pers->start_reshape(mddev);
+ md_update_sb(mddev, 1);
}
mddev_unlock(mddev);
}
--
2.4.3
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] Need update superblock on time when deciding to do reshape
2016-05-17 8:54 [PATCH] Need update superblock on time when deciding to do reshape Xiao Ni
@ 2016-05-20 17:59 ` Shaohua Li
2016-05-22 2:14 ` Xiao Ni
0 siblings, 1 reply; 6+ messages in thread
From: Shaohua Li @ 2016-05-20 17:59 UTC (permalink / raw)
To: Xiao Ni; +Cc: linux-raid, Jes.Sorensen
On Tue, May 17, 2016 at 04:54:09PM +0800, Xiao Ni wrote:
> Hi all
>
> If the disks are not enough to have spaces for relocating the data_offset,
> it needs to run start_reshape and then run mdadm --grow --continue by
> systemd. But mdadm --grow --continue fails because it checkes that
> info->reshape_active is 0.
>
> The info->reshape_active is set to 1 when the superblock feature_map
> have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
> MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
>
> Function start_reshape calls raid5_start_reshape which changes
> mddev->reshape_position to 0. Then in md_check_recovery it updates the
> superblock to underlying devices. But there is a chance that the superblock
> haven't written to underlying devices, the mdadm reads the superblock data.
> So mdadm --grow --continue fails.
>
> The steps to reproduce this:
> mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
> mdadm --wait /dev/md0
> mdadm /dev/md0 -a /dev/loop3
> mdadm --grow --raid-devices 4 /dev/md0
> The loop device size is 500MB
>
> [root@storageqe-09 ~]# cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
> 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]
> [>....................] reshape = 0.0% (1/510976) finish=0.0min speed=255488K/sec
> bitmap: 1/1 pages [4KB], 65536KB chunk
what's the bad effect of the --continue failure? I think reshape will still
continue. Doing a update super there is ok, but I'm wondering if it's the good
way. Could mdadm wait for MD_FEATURE_RESHAPE_ACTIVE then let systemd run?
Because sounds like we are working around systemd bug, kernel itself will write
superblock anyway soon, so we probably working around in userspace.
> unused devices: <none>
>
> So if we update the superblock on time, mdadm can read the right superblock data.
>
> Signed-off-by <xni@redhat.com>
>
> ---
> drivers/md/md.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 14d3b37..7919606 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char *page, size_t len)
> else {
> clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> err = mddev->pers->start_reshape(mddev);
> + md_update_sb(mddev, 1);
write super even err != 0?
Thanks,
Shaohua
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Need update superblock on time when deciding to do reshape
2016-05-20 17:59 ` Shaohua Li
@ 2016-05-22 2:14 ` Xiao Ni
2016-05-23 19:02 ` Shaohua Li
0 siblings, 1 reply; 6+ messages in thread
From: Xiao Ni @ 2016-05-22 2:14 UTC (permalink / raw)
To: Shaohua Li; +Cc: linux-raid, Jes Sorensen
----- Original Message -----
> From: "Shaohua Li" <shli@kernel.org>
> To: "Xiao Ni" <xni@redhat.com>
> Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> Sent: Saturday, May 21, 2016 1:59:46 AM
> Subject: Re: [PATCH] Need update superblock on time when deciding to do reshape
>
> On Tue, May 17, 2016 at 04:54:09PM +0800, Xiao Ni wrote:
> > Hi all
> >
> > If the disks are not enough to have spaces for relocating the data_offset,
> > it needs to run start_reshape and then run mdadm --grow --continue by
> > systemd. But mdadm --grow --continue fails because it checkes that
> > info->reshape_active is 0.
> >
> > The info->reshape_active is set to 1 when the superblock feature_map
> > have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
> > MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
> >
> > Function start_reshape calls raid5_start_reshape which changes
> > mddev->reshape_position to 0. Then in md_check_recovery it updates the
> > superblock to underlying devices. But there is a chance that the superblock
> > haven't written to underlying devices, the mdadm reads the superblock data.
> > So mdadm --grow --continue fails.
> >
> > The steps to reproduce this:
> > mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
> > mdadm --wait /dev/md0
> > mdadm /dev/md0 -a /dev/loop3
> > mdadm --grow --raid-devices 4 /dev/md0
> > The loop device size is 500MB
> >
> > [root@storageqe-09 ~]# cat /proc/mdstat
> > Personalities : [raid6] [raid5] [raid4]
> > md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
> > 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
> > [UUUU]
> > [>....................] reshape = 0.0% (1/510976) finish=0.0min
> > speed=255488K/sec
> > bitmap: 1/1 pages [4KB], 65536KB chunk
>
> what's the bad effect of the --continue failure? I think reshape will still
> continue. Doing a update super there is ok, but I'm wondering if it's the
> good
> way. Could mdadm wait for MD_FEATURE_RESHAPE_ACTIVE then let systemd run?
> Because sounds like we are working around systemd bug, kernel itself will
> write
> superblock anyway soon, so we probably working around in userspace.
There is no bad effect if --continue failure. It just miss one chance to
go on reshaping. Yes, as you said we can fix this in userspace. I tried
to start mdadm-grow-continue@.service 30 seconds later as mdadm-last-resort@.service
does. It can fix this too.
Sure it should be fixed this if mdadm try more times to check MD_FEATURE_RESHAPE_ACTIVE.
>
> > unused devices: <none>
> >
> > So if we update the superblock on time, mdadm can read the right superblock
> > data.
> >
> > Signed-off-by <xni@redhat.com>
> >
> > ---
> > drivers/md/md.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 14d3b37..7919606 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char *page,
> > size_t len)
> > else {
> > clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > err = mddev->pers->start_reshape(mddev);
> > + md_update_sb(mddev, 1);
>
> write super even err != 0?
Ah, sorry for this. It should update superblock only err is 0.
At first I want to fix this in userspace, but I ask myself why shouldn't update
the superblock once start_reshape returns. There are some guys waiting for the
update. The function action_store should update the superblock in time to tell
the colleagues what happens now. Then I checked the places where md_update_sb
is called. I found it is indeed called in some places where the md device
changes. So I sent the patch here.
By the way, in size_store it update the superblock when err != 0. Is it right
to check err there?
Best Regards
Xiao
>
> Thanks,
> Shaohua
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Need update superblock on time when deciding to do reshape
2016-05-22 2:14 ` Xiao Ni
@ 2016-05-23 19:02 ` Shaohua Li
2016-05-23 21:19 ` Xiao Ni
0 siblings, 1 reply; 6+ messages in thread
From: Shaohua Li @ 2016-05-23 19:02 UTC (permalink / raw)
To: Xiao Ni; +Cc: linux-raid, Jes Sorensen
On Sat, May 21, 2016 at 10:14:07PM -0400, Xiao Ni wrote:
>
>
> ----- Original Message -----
> > From: "Shaohua Li" <shli@kernel.org>
> > To: "Xiao Ni" <xni@redhat.com>
> > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> > Sent: Saturday, May 21, 2016 1:59:46 AM
> > Subject: Re: [PATCH] Need update superblock on time when deciding to do reshape
> >
> > On Tue, May 17, 2016 at 04:54:09PM +0800, Xiao Ni wrote:
> > > Hi all
> > >
> > > If the disks are not enough to have spaces for relocating the data_offset,
> > > it needs to run start_reshape and then run mdadm --grow --continue by
> > > systemd. But mdadm --grow --continue fails because it checkes that
> > > info->reshape_active is 0.
> > >
> > > The info->reshape_active is set to 1 when the superblock feature_map
> > > have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
> > > MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
> > >
> > > Function start_reshape calls raid5_start_reshape which changes
> > > mddev->reshape_position to 0. Then in md_check_recovery it updates the
> > > superblock to underlying devices. But there is a chance that the superblock
> > > haven't written to underlying devices, the mdadm reads the superblock data.
> > > So mdadm --grow --continue fails.
> > >
> > > The steps to reproduce this:
> > > mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
> > > mdadm --wait /dev/md0
> > > mdadm /dev/md0 -a /dev/loop3
> > > mdadm --grow --raid-devices 4 /dev/md0
> > > The loop device size is 500MB
> > >
> > > [root@storageqe-09 ~]# cat /proc/mdstat
> > > Personalities : [raid6] [raid5] [raid4]
> > > md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
> > > 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
> > > [UUUU]
> > > [>....................] reshape = 0.0% (1/510976) finish=0.0min
> > > speed=255488K/sec
> > > bitmap: 1/1 pages [4KB], 65536KB chunk
> >
> > what's the bad effect of the --continue failure? I think reshape will still
> > continue. Doing a update super there is ok, but I'm wondering if it's the
> > good
> > way. Could mdadm wait for MD_FEATURE_RESHAPE_ACTIVE then let systemd run?
> > Because sounds like we are working around systemd bug, kernel itself will
> > write
> > superblock anyway soon, so we probably working around in userspace.
>
> There is no bad effect if --continue failure. It just miss one chance to
> go on reshaping. Yes, as you said we can fix this in userspace. I tried
> to start mdadm-grow-continue@.service 30 seconds later as mdadm-last-resort@.service
> does. It can fix this too.
>
> Sure it should be fixed this if mdadm try more times to check MD_FEATURE_RESHAPE_ACTIVE.
>
> >
> > > unused devices: <none>
> > >
> > > So if we update the superblock on time, mdadm can read the right superblock
> > > data.
> > >
> > > Signed-off-by <xni@redhat.com>
> > >
> > > ---
> > > drivers/md/md.c | 1 +
> > > 1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > > index 14d3b37..7919606 100644
> > > --- a/drivers/md/md.c
> > > +++ b/drivers/md/md.c
> > > @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char *page,
> > > size_t len)
> > > else {
> > > clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > err = mddev->pers->start_reshape(mddev);
> > > + md_update_sb(mddev, 1);
> >
> > write super even err != 0?
>
> Ah, sorry for this. It should update superblock only err is 0.
>
> At first I want to fix this in userspace, but I ask myself why shouldn't update
> the superblock once start_reshape returns. There are some guys waiting for the
> update. The function action_store should update the superblock in time to tell
> the colleagues what happens now. Then I checked the places where md_update_sb
> is called. I found it is indeed called in some places where the md device
> changes. So I sent the patch here.
>
> By the way, in size_store it update the superblock when err != 0. Is it right
> to check err there?
I think we should. probably nobody noticed it before.
Thanks,
Shaohua
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Need update superblock on time when deciding to do reshape
2016-05-23 19:02 ` Shaohua Li
@ 2016-05-23 21:19 ` Xiao Ni
2016-05-23 23:02 ` Shaohua Li
0 siblings, 1 reply; 6+ messages in thread
From: Xiao Ni @ 2016-05-23 21:19 UTC (permalink / raw)
To: Shaohua Li; +Cc: linux-raid, Jes Sorensen
----- Original Message -----
> From: "Shaohua Li" <shli@kernel.org>
> To: "Xiao Ni" <xni@redhat.com>
> Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> Sent: Tuesday, May 24, 2016 3:02:04 AM
> Subject: Re: [PATCH] Need update superblock on time when deciding to do reshape
>
> On Sat, May 21, 2016 at 10:14:07PM -0400, Xiao Ni wrote:
> >
> >
> > ----- Original Message -----
> > > From: "Shaohua Li" <shli@kernel.org>
> > > To: "Xiao Ni" <xni@redhat.com>
> > > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> > > Sent: Saturday, May 21, 2016 1:59:46 AM
> > > Subject: Re: [PATCH] Need update superblock on time when deciding to do
> > > reshape
> > >
> > > On Tue, May 17, 2016 at 04:54:09PM +0800, Xiao Ni wrote:
> > > > Hi all
> > > >
> > > > If the disks are not enough to have spaces for relocating the
> > > > data_offset,
> > > > it needs to run start_reshape and then run mdadm --grow --continue by
> > > > systemd. But mdadm --grow --continue fails because it checkes that
> > > > info->reshape_active is 0.
> > > >
> > > > The info->reshape_active is set to 1 when the superblock feature_map
> > > > have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
> > > > MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
> > > >
> > > > Function start_reshape calls raid5_start_reshape which changes
> > > > mddev->reshape_position to 0. Then in md_check_recovery it updates the
> > > > superblock to underlying devices. But there is a chance that the
> > > > superblock
> > > > haven't written to underlying devices, the mdadm reads the superblock
> > > > data.
> > > > So mdadm --grow --continue fails.
> > > >
> > > > The steps to reproduce this:
> > > > mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
> > > > mdadm --wait /dev/md0
> > > > mdadm /dev/md0 -a /dev/loop3
> > > > mdadm --grow --raid-devices 4 /dev/md0
> > > > The loop device size is 500MB
> > > >
> > > > [root@storageqe-09 ~]# cat /proc/mdstat
> > > > Personalities : [raid6] [raid5] [raid4]
> > > > md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
> > > > 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
> > > > [UUUU]
> > > > [>....................] reshape = 0.0% (1/510976) finish=0.0min
> > > > speed=255488K/sec
> > > > bitmap: 1/1 pages [4KB], 65536KB chunk
> > >
> > > what's the bad effect of the --continue failure? I think reshape will
> > > still
> > > continue. Doing a update super there is ok, but I'm wondering if it's the
> > > good
> > > way. Could mdadm wait for MD_FEATURE_RESHAPE_ACTIVE then let systemd run?
> > > Because sounds like we are working around systemd bug, kernel itself will
> > > write
> > > superblock anyway soon, so we probably working around in userspace.
> >
> > There is no bad effect if --continue failure. It just miss one chance to
> > go on reshaping. Yes, as you said we can fix this in userspace. I tried
> > to start mdadm-grow-continue@.service 30 seconds later as
> > mdadm-last-resort@.service
> > does. It can fix this too.
> >
> > Sure it should be fixed this if mdadm try more times to check
> > MD_FEATURE_RESHAPE_ACTIVE.
> >
> > >
> > > > unused devices: <none>
> > > >
> > > > So if we update the superblock on time, mdadm can read the right
> > > > superblock
> > > > data.
> > > >
> > > > Signed-off-by <xni@redhat.com>
> > > >
> > > > ---
> > > > drivers/md/md.c | 1 +
> > > > 1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > > > index 14d3b37..7919606 100644
> > > > --- a/drivers/md/md.c
> > > > +++ b/drivers/md/md.c
> > > > @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char
> > > > *page,
> > > > size_t len)
> > > > else {
> > > > clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > > err = mddev->pers->start_reshape(mddev);
> > > > + md_update_sb(mddev, 1);
> > >
> > > write super even err != 0?
> >
> > Ah, sorry for this. It should update superblock only err is 0.
> >
> > At first I want to fix this in userspace, but I ask myself why shouldn't
> > update
> > the superblock once start_reshape returns. There are some guys waiting for
> > the
> > update. The function action_store should update the superblock in time to
> > tell
> > the colleagues what happens now. Then I checked the places where
> > md_update_sb
> > is called. I found it is indeed called in some places where the md device
> > changes. So I sent the patch here.
> >
> > By the way, in size_store it update the superblock when err != 0. Is it
> > right
> > to check err there?
>
> I think we should. probably nobody noticed it before.
>
So does it mean you applied the way fixing the problem in kernel space? If
you apply the method I'll re-send the patch.
Best Regards
Xiao
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Need update superblock on time when deciding to do reshape
2016-05-23 21:19 ` Xiao Ni
@ 2016-05-23 23:02 ` Shaohua Li
0 siblings, 0 replies; 6+ messages in thread
From: Shaohua Li @ 2016-05-23 23:02 UTC (permalink / raw)
To: Xiao Ni; +Cc: linux-raid, Jes Sorensen
On Mon, May 23, 2016 at 05:19:41PM -0400, Xiao Ni wrote:
>
>
> ----- Original Message -----
> > From: "Shaohua Li" <shli@kernel.org>
> > To: "Xiao Ni" <xni@redhat.com>
> > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> > Sent: Tuesday, May 24, 2016 3:02:04 AM
> > Subject: Re: [PATCH] Need update superblock on time when deciding to do reshape
> >
> > On Sat, May 21, 2016 at 10:14:07PM -0400, Xiao Ni wrote:
> > >
> > >
> > > ----- Original Message -----
> > > > From: "Shaohua Li" <shli@kernel.org>
> > > > To: "Xiao Ni" <xni@redhat.com>
> > > > Cc: linux-raid@vger.kernel.org, "Jes Sorensen" <Jes.Sorensen@redhat.com>
> > > > Sent: Saturday, May 21, 2016 1:59:46 AM
> > > > Subject: Re: [PATCH] Need update superblock on time when deciding to do
> > > > reshape
> > > >
> > > > On Tue, May 17, 2016 at 04:54:09PM +0800, Xiao Ni wrote:
> > > > > Hi all
> > > > >
> > > > > If the disks are not enough to have spaces for relocating the
> > > > > data_offset,
> > > > > it needs to run start_reshape and then run mdadm --grow --continue by
> > > > > systemd. But mdadm --grow --continue fails because it checkes that
> > > > > info->reshape_active is 0.
> > > > >
> > > > > The info->reshape_active is set to 1 when the superblock feature_map
> > > > > have the flag MD_FEATURE_RESHAPE_ACTIVE. Superblock feature_map is set
> > > > > MD_FEATURE_RESHAPE_ACTIVE as mddev->reshape_position != MaxSector.
> > > > >
> > > > > Function start_reshape calls raid5_start_reshape which changes
> > > > > mddev->reshape_position to 0. Then in md_check_recovery it updates the
> > > > > superblock to underlying devices. But there is a chance that the
> > > > > superblock
> > > > > haven't written to underlying devices, the mdadm reads the superblock
> > > > > data.
> > > > > So mdadm --grow --continue fails.
> > > > >
> > > > > The steps to reproduce this:
> > > > > mdadm -CR /dev/md0 -l5 -n3 /dev/loop[0-2] --bitmap=internal
> > > > > mdadm --wait /dev/md0
> > > > > mdadm /dev/md0 -a /dev/loop3
> > > > > mdadm --grow --raid-devices 4 /dev/md0
> > > > > The loop device size is 500MB
> > > > >
> > > > > [root@storageqe-09 ~]# cat /proc/mdstat
> > > > > Personalities : [raid6] [raid5] [raid4]
> > > > > md0 : active raid5 loop3[4] loop2[3] loop1[1] loop0[0]
> > > > > 1021952 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4]
> > > > > [UUUU]
> > > > > [>....................] reshape = 0.0% (1/510976) finish=0.0min
> > > > > speed=255488K/sec
> > > > > bitmap: 1/1 pages [4KB], 65536KB chunk
> > > >
> > > > what's the bad effect of the --continue failure? I think reshape will
> > > > still
> > > > continue. Doing a update super there is ok, but I'm wondering if it's the
> > > > good
> > > > way. Could mdadm wait for MD_FEATURE_RESHAPE_ACTIVE then let systemd run?
> > > > Because sounds like we are working around systemd bug, kernel itself will
> > > > write
> > > > superblock anyway soon, so we probably working around in userspace.
> > >
> > > There is no bad effect if --continue failure. It just miss one chance to
> > > go on reshaping. Yes, as you said we can fix this in userspace. I tried
> > > to start mdadm-grow-continue@.service 30 seconds later as
> > > mdadm-last-resort@.service
> > > does. It can fix this too.
> > >
> > > Sure it should be fixed this if mdadm try more times to check
> > > MD_FEATURE_RESHAPE_ACTIVE.
> > >
> > > >
> > > > > unused devices: <none>
> > > > >
> > > > > So if we update the superblock on time, mdadm can read the right
> > > > > superblock
> > > > > data.
> > > > >
> > > > > Signed-off-by <xni@redhat.com>
> > > > >
> > > > > ---
> > > > > drivers/md/md.c | 1 +
> > > > > 1 file changed, 1 insertion(+)
> > > > >
> > > > > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > > > > index 14d3b37..7919606 100644
> > > > > --- a/drivers/md/md.c
> > > > > +++ b/drivers/md/md.c
> > > > > @@ -4350,6 +4350,7 @@ action_store(struct mddev *mddev, const char
> > > > > *page,
> > > > > size_t len)
> > > > > else {
> > > > > clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > > > err = mddev->pers->start_reshape(mddev);
> > > > > + md_update_sb(mddev, 1);
> > > >
> > > > write super even err != 0?
> > >
> > > Ah, sorry for this. It should update superblock only err is 0.
> > >
> > > At first I want to fix this in userspace, but I ask myself why shouldn't
> > > update
> > > the superblock once start_reshape returns. There are some guys waiting for
> > > the
> > > update. The function action_store should update the superblock in time to
> > > tell
> > > the colleagues what happens now. Then I checked the places where
> > > md_update_sb
> > > is called. I found it is indeed called in some places where the md device
> > > changes. So I sent the patch here.
> > >
> > > By the way, in size_store it update the superblock when err != 0. Is it
> > > right
> > > to check err there?
> >
> > I think we should. probably nobody noticed it before.
> >
>
> So does it mean you applied the way fixing the problem in kernel space? If
> you apply the method I'll re-send the patch.
No, I didn't. I thought you agree with fixing it in userspace. For the err != 0
checking, I mean we probably should do it for size_store if somebody wants to
fix it.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-05-23 23:02 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-05-17 8:54 [PATCH] Need update superblock on time when deciding to do reshape Xiao Ni
2016-05-20 17:59 ` Shaohua Li
2016-05-22 2:14 ` Xiao Ni
2016-05-23 19:02 ` Shaohua Li
2016-05-23 21:19 ` Xiao Ni
2016-05-23 23:02 ` Shaohua Li
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