| Message ID | 20210205141301.71682-1-jinpu.wang@cloud.ionos.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [stable-5.10] md: Set prev_flush_start and flush_bio in an atomic way | expand |
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.
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) {