linux-kernel - Re: Fwd: [PATCH V2] md raid: fix hang when stopping arrays with metadata through dm-raid

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Message-Id: <53350e3b-aec6-47ac-bd39-9d3ec04ad51d@fnnas.com>
Date: Mon, 26 Jan 2026 13:50:37 +0800
From: "Yu Kuai" <yukuai@...as.com>
To: "Heinz Mauelshagen" <heinzm@...hat.com>, 
	"linux-raid" <linux-raid@...r.kernel.org>, 
	"Linux-Kernel" <linux-kernel@...r.kernel.org>, 
	"Song Liu" <song@...nel.org>, <yukuai@...as.com>
Subject: Re: Fwd: [PATCH V2] md raid: fix hang when stopping arrays with metadata through dm-raid

在 2026/1/15 1:52, Heinz Mauelshagen 写道:

> hen 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
>
> Removing the top-level device triggers a hang in the following
> sequence: the dm-raid
> destructor calls md_stop(), which tries to flush the write-intent
> bitmap by writing
> to the metadata sub-devices. However, these devices are already
> suspended, making
> them unable to complete the write operations and causing an indefinite block.
>
> Fix:
>
> - Prevent bitmap flushing when md_stop() is called from dm-raid
> destructor context
>    and avoid a quiescing/unquescing cycle which could also cause I/O
>
> - Still allow write-intent bitmap flushing when called from dm-raid
> suspend context
>
> This ensures that RAID array teardown can complete successfully even when the
> underlying devices are in a suspended state.
>
> This second patch uses md_is_rdwr() to distinguish between suspend and
> destructor paths as elaborated on above.
>
> Signed-off-by: Heinz Mauelshagen<heinzm@...hat.com>
> ---
>   drivers/md/md.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)

There are conflicts now, applied with some rebasing:

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 606f616190d7..59cd303548de 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6851,13 +6851,15 @@ 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 (md_is_rdwr(mddev) || !mddev_is_dm(mddev)) {
+               if (mddev->pers && mddev->pers->quiesce) {
+                       mddev->pers->quiesce(mddev, 1);
+                       mddev->pers->quiesce(mddev, 0);
+               }

-       if (md_bitmap_enabled(mddev, true))
-               mddev->bitmap_ops->flush(mddev);
+               if (md_bitmap_enabled(mddev, true))
+                       mddev->bitmap_ops->flush(mddev);
+       }

         if (md_is_rdwr(mddev) &&
             ((!mddev->in_sync && !mddev_is_clustered(mddev)) ||

-- 
Thansk,
Kuai