Re: [PATCH v3] md: clear MD_CLOSING when array_state_store() bails on interrupted lock

[yu kuai]

Hi,

在 2026/11/2 15:35, Jack Wang 写道:
> From: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxx>
>
> Writing "clear", "readonly", "inactive" or "read_auto" to array_state
> calls mddev_set_closing_and_sync_blockdev(), which sets MD_CLOSING to
> keep the array from being reopened while it is torn down. The flag is
> only cleared again at the tail of array_state_store() (for readonly /
> read_auto / inactive, or the failed-clear case).
>
> Between setting the flag and reaching that tail there is an early return:
>
> 	err = mddev_lock(mddev);
> 	if (err)
> 		return err;
>
> mddev_lock() is mutex_lock_interruptible() on reconfig_mutex. If the
> writing task catches a signal while blocked there, it returns -EINTR and
> MD_CLOSING is left set on a still-running array. do_md_stop() /
> md_set_readonly() never ran, so the array keeps working internally, but
> every subsequent md_open() now returns -ENODEV for all callers - the
> device shows up in /proc/mdstat and sysfs is fully populated, yet cannot
> be opened, and cannot be recovered without a reboot (all clear paths
> either need the device open or re-enter test_and_set_bit(MD_CLOSING) and
> bail with -EBUSY before the clear).
>
> The window is easy to hit on a busy host: reconfig_mutex is held for long
> stretches by a running resync/recovery, widening the interruptible wait,
> and a userspace helper writing to array_state and then being killed or
> timed out is enough to leak the flag.
>
> Clear the flag directly in the interrupted-lock exit. Guard the clear
> with a set_closing flag that records whether this write actually set
> MD_CLOSING: the set call is skipped when the array is not running
> read-write (or mddev->pers is NULL), and in that case this write must
> not clear a MD_CLOSING it never set. This also tightens the pre-existing
> tail clear, which had the same unconditional behaviour.
>
> Fixes: 99b902ac1725 ("md: sync blockdev before stopping raid or setting readonly")
> Assisted-by: Claude:claude-opus-4-8 [Claude Code]

checkpatch reprot error with this tag.

> Signed-off-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxx>
> ---
> v3: (Kuai) clear MD_CLOSING directly at the mddev_lock() failure and
>      return, drop the out_clear_closing label; reword the commit message.
>      Keep the set_closing guard: the set call is skipped when the array
>      is not rdwr or mddev->pers is NULL, so this write may not own the
>      flag. Rebased on v7.4-rc1.
> v2: guard the clear with set_closing.
>
>   drivers/md/md.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 03e35386a802..f14a31387990 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4671,6 +4671,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
>   {
>   	int err = 0;
>   	enum array_state st = match_word(buf, array_states);
> +	bool set_closing = false;
>   
>   	/* No lock dependent actions */
>   	switch (st) {
> @@ -4691,6 +4692,7 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
>   		err = mddev_set_closing_and_sync_blockdev(mddev, 0);
>   		if (err)
>   			return err;
> +		set_closing = true;
>   		break;
>   	default:
>   		break;
> @@ -4718,8 +4720,12 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
>   		return err ?: len;
>   	}
>   	err = mddev_lock(mddev);
> -	if (err)
> +	if (err) {
> +		/* Interrupted before any teardown ran, don't leak MD_CLOSING */
> +		if (set_closing)
> +			clear_bit(MD_CLOSING, &mddev->flags);
>   		return err;
> +	}
>   
>   	switch (st) {
>   	case inactive:
> @@ -4792,8 +4798,9 @@ array_state_store(struct mddev *mddev, const char *buf, size_t len)
>   	}
>   	mddev_unlock(mddev);
>   
> -	if (st == readonly || st == read_auto || st == inactive ||
> -	    (err && st == clear))
> +	if (set_closing &&
> +	    (st == readonly || st == read_auto || st == inactive ||
> +	     (err && st == clear)))

Just keep the checking of set_closing should be enough.

>   		clear_bit(MD_CLOSING, &mddev->flags);
>   
>   	return err ?: len;

-- 
Thanks,
Kuai