drivers/md/md.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
When using device-mapper's dm-raid target, stopping a RAID array can cause the
system to hang under specific conditions.
This occurs when:
- A dm-raid managed device tree is suspended from top to bottom
(the top-level RAID device is suspended first, followed by its
underlying metadata and data devices)
- The top-level RAID device is then removed
The hang happens because removing the top-level device triggers md_stop() from the
dm-raid destructor. This function attempts to flush the write-intent bitmap, which
requires writing bitmap superblocks to the metadata sub-devices. However, since
these metadata devices are already suspended, the write operations cannot complete,
causing the system to hang.
Fix:
- Prevent bitmap flushing when md_stop() is called from dm-raid contexts
and avoid a quiescing/unquescing cycle which could also cause I/O
- Avoid any I/O operations that might occur during the quiesce/unquiesce process in md_stop()
This ensures that RAID array teardown can complete successfully even when the
underlying devices are in a suspended state.
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
---
drivers/md/md.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4e033c26fdd4..53e15bdd9ab2 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6541,12 +6541,14 @@ static void __md_stop_writes(struct mddev *mddev)
{
timer_delete_sync(&mddev->safemode_timer);
- if (mddev->pers && mddev->pers->quiesce) {
- mddev->pers->quiesce(mddev, 1);
- mddev->pers->quiesce(mddev, 0);
- }
+ if (!mddev_is_dm(mddev)) {
+ if (mddev->pers && mddev->pers->quiesce) {
+ mddev->pers->quiesce(mddev, 1);
+ mddev->pers->quiesce(mddev, 0);
+ }
- mddev->bitmap_ops->flush(mddev);
+ mddev->bitmap_ops->flush(mddev);
+ }
if (md_is_rdwr(mddev) &&
((!mddev->in_sync && !mddev_is_clustered(mddev)) ||
--
2.51.0
Hi, 在 2025/09/18 21:42, Heinz Mauelshagen 写道: > When using device-mapper's dm-raid target, stopping a RAID array can cause the > system to hang under specific conditions. > > This occurs when: > > - A dm-raid managed device tree is suspended from top to bottom > (the top-level RAID device is suspended first, followed by its > underlying metadata and data devices) > > - The top-level RAID device is then removed > > The hang happens because removing the top-level device triggers md_stop() from the > dm-raid destructor. This function attempts to flush the write-intent bitmap, which > requires writing bitmap superblocks to the metadata sub-devices. However, since > these metadata devices are already suspended, the write operations cannot complete, > causing the system to hang. > > Fix: > > - Prevent bitmap flushing when md_stop() is called from dm-raid contexts > and avoid a quiescing/unquescing cycle which could also cause I/O If bitmap flush is skipped, then bitmap can still be dirty after dm-raid is stopped, and the next time when dm-raid is reloaded, looks like there will be unnecessary data resync because there are dirty bits? Thanks, Kuai > > - Avoid any I/O operations that might occur during the quiesce/unquiesce process in md_stop() > > This ensures that RAID array teardown can complete successfully even when the > underlying devices are in a suspended state. > > Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com> > --- > drivers/md/md.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 4e033c26fdd4..53e15bdd9ab2 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -6541,12 +6541,14 @@ static void __md_stop_writes(struct mddev *mddev) > { > timer_delete_sync(&mddev->safemode_timer); > > - if (mddev->pers && mddev->pers->quiesce) { > - mddev->pers->quiesce(mddev, 1); > - mddev->pers->quiesce(mddev, 0); > - } > + if (!mddev_is_dm(mddev)) { > + if (mddev->pers && mddev->pers->quiesce) { > + mddev->pers->quiesce(mddev, 1); > + mddev->pers->quiesce(mddev, 0); > + } > > - mddev->bitmap_ops->flush(mddev); > + mddev->bitmap_ops->flush(mddev); > + } > > if (md_is_rdwr(mddev) && > ((!mddev->in_sync && !mddev_is_clustered(mddev)) || >
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