From: Xiao Ni xni@redhat.com
One customer reports a crash problem which causes by flush request. It triggers a warning before crash.
/* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; }
The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work.
We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way.
Reviewed-by: David Jeffery djeffery@redhat.com Signed-off-by: Xiao Ni xni@redhat.com Signed-off-by: Song Liu songliubraving@fb.com [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com --- drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c index ea139d0c0bc3..2bd60bd9e2ca 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) * could wait for this and below md_handle_request could wait for those * bios because of suspend check */ + spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL; + spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait);
if (bio->bi_iter.bi_size == 0) {
On Fri, Feb 05, 2021 at 03:13:01PM +0100, Jack Wang wrote:
From: Xiao Ni xni@redhat.com
One customer reports a crash problem which causes by flush request. It triggers a warning before crash.
/* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; }The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work.
We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way.
Reviewed-by: David Jeffery djeffery@redhat.com Signed-off-by: Xiao Ni xni@redhat.com Signed-off-by: Song Liu songliubraving@fb.com [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com
drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c index ea139d0c0bc3..2bd60bd9e2ca 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) * could wait for this and below md_handle_request could wait for those * bios because of suspend check */
- spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL;
- spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait);
if (bio->bi_iter.bi_size == 0) { -- 2.25.1
Now queued up, thanks.
greg k-h
On Mon, Feb 8, 2021 at 1:45 PM Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Feb 05, 2021 at 03:13:01PM +0100, Jack Wang wrote:
From: Xiao Ni xni@redhat.com
One customer reports a crash problem which causes by flush request. It triggers a warning before crash.
/* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; }The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work.
We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way.
Reviewed-by: David Jeffery djeffery@redhat.com Signed-off-by: Xiao Ni xni@redhat.com Signed-off-by: Song Liu songliubraving@fb.com [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com
drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c index ea139d0c0bc3..2bd60bd9e2ca 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) * could wait for this and below md_handle_request could wait for those * bios because of suspend check */
spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL;spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait); if (bio->bi_iter.bi_size == 0) {-- 2.25.1
Now queued up, thanks.
greg k-h
Thanks, I see only this patch got applied. Do you have concern regarding first 7 patches?
Regards!
On Mon, Feb 08, 2021 at 03:38:48PM +0100, Jinpu Wang wrote:
On Mon, Feb 8, 2021 at 1:45 PM Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Feb 05, 2021 at 03:13:01PM +0100, Jack Wang wrote:
From: Xiao Ni xni@redhat.com
One customer reports a crash problem which causes by flush request. It triggers a warning before crash.
/* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; }The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work.
We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way.
Reviewed-by: David Jeffery djeffery@redhat.com Signed-off-by: Xiao Ni xni@redhat.com Signed-off-by: Song Liu songliubraving@fb.com [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com
drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c index ea139d0c0bc3..2bd60bd9e2ca 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) * could wait for this and below md_handle_request could wait for those * bios because of suspend check */
spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL;spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait); if (bio->bi_iter.bi_size == 0) {-- 2.25.1
Now queued up, thanks.
greg k-h
Thanks, I see only this patch got applied. Do you have concern regarding first 7 patches?
I only see this one patch. Please resend anything else you wish to have applied as I think I said that I dropped everything you submitted before, right?
thanks,
greg k-h
On Mon, Feb 8, 2021 at 3:49 PM Greg KH gregkh@linuxfoundation.org wrote:
On Mon, Feb 08, 2021 at 03:38:48PM +0100, Jinpu Wang wrote:
On Mon, Feb 8, 2021 at 1:45 PM Greg KH gregkh@linuxfoundation.org wrote:
On Fri, Feb 05, 2021 at 03:13:01PM +0100, Jack Wang wrote:
From: Xiao Ni xni@redhat.com
One customer reports a crash problem which causes by flush request. It triggers a warning before crash.
/* new request after previous flush is completed */ if (ktime_after(req_start, mddev->prev_flush_start)) { WARN_ON(mddev->flush_bio); mddev->flush_bio = bio; bio = NULL; }The WARN_ON is triggered. We use spin lock to protect prev_flush_start and flush_bio in md_flush_request. But there is no lock protection in md_submit_flush_data. It can set flush_bio to NULL first because of compiler reordering write instructions.
For example, flush bio1 sets flush bio to NULL first in md_submit_flush_data. An interrupt or vmware causing an extended stall happen between updating flush_bio and prev_flush_start. Because flush_bio is NULL, flush bio2 can get the lock and submit to underlayer disks. Then flush bio1 updates prev_flush_start after the interrupt or extended stall.
Then flush bio3 enters in md_flush_request. The start time req_start is behind prev_flush_start. The flush_bio is not NULL(flush bio2 hasn't finished). So it can trigger the WARN_ON now. Then it calls INIT_WORK again. INIT_WORK() will re-initialize the list pointers in the work_struct, which then can result in a corrupted work list and the work_struct queued a second time. With the work list corrupted, it can lead in invalid work items being used and cause a crash in process_one_work.
We need to make sure only one flush bio can be handled at one same time. So add spin lock in md_submit_flush_data to protect prev_flush_start and flush_bio in an atomic way.
Reviewed-by: David Jeffery djeffery@redhat.com Signed-off-by: Xiao Ni xni@redhat.com Signed-off-by: Song Liu songliubraving@fb.com [jwang: backport dc5d17a3c39b06aef866afca19245a9cfb533a79 to 4.19] Signed-off-by: Jack Wang jinpu.wang@cloud.ionos.com
drivers/md/md.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/md/md.c b/drivers/md/md.c index ea139d0c0bc3..2bd60bd9e2ca 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -639,8 +639,10 @@ static void md_submit_flush_data(struct work_struct *ws) * could wait for this and below md_handle_request could wait for those * bios because of suspend check */
spin_lock_irq(&mddev->lock); mddev->last_flush = mddev->start_flush; mddev->flush_bio = NULL;spin_unlock_irq(&mddev->lock); wake_up(&mddev->sb_wait); if (bio->bi_iter.bi_size == 0) {-- 2.25.1
Now queued up, thanks.
greg k-h
Thanks, I see only this patch got applied. Do you have concern regarding first 7 patches?
I only see this one patch. Please resend anything else you wish to have applied as I think I said that I dropped everything you submitted before, right?
Ah, ok, I misunderstood your comments, I will resend them.
thanks,
greg k-h
Thanks.
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Jack Wang -
Jinpu Wang