md: get rdev->mddev with READ_ONCE()

[PATCH] md: get rdev->mddev with READ_ONCE()

Posted by Li Lingfeng 1 year, 12 months ago

From: Li Lingfeng <lilingfeng3@huawei.com>

Users may get rdev->mddev by sysfs while rdev is releasing.
So use both READ_ONCE() and WRITE_ONCE() to prevent load/store tearing
and to read/write mddev atomically.

Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
---
 drivers/md/md.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9bdd57324c37..3b38a565bffa 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2562,7 +2562,7 @@ static void md_kick_rdev_from_array(struct md_rdev *rdev)
 	list_del_rcu(&rdev->same_set);
 	pr_debug("md: unbind<%pg>\n", rdev->bdev);
 	mddev_destroy_serial_pool(rdev->mddev, rdev);
-	rdev->mddev = NULL;
+	WRITE_ONCE(rdev->mddev, NULL);
 	sysfs_remove_link(&rdev->kobj, "block");
 	sysfs_put(rdev->sysfs_state);
 	sysfs_put(rdev->sysfs_unack_badblocks);
@@ -3646,7 +3646,7 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
 	struct kernfs_node *kn = NULL;
 	bool suspend = false;
 	ssize_t rv;
-	struct mddev *mddev = rdev->mddev;
+	struct mddev *mddev = READ_ONCE(rdev->mddev);
 
 	if (!entry->store)
 		return -EIO;
-- 
2.39.2

Re: [PATCH] md: get rdev->mddev with READ_ONCE()

Posted by Li Lingfeng 1 year, 11 months ago

Friendly ping ...

Thanks

在 2023/12/29 15:05, Li Lingfeng 写道:
> From: Li Lingfeng <lilingfeng3@huawei.com>
>
> Users may get rdev->mddev by sysfs while rdev is releasing.
> So use both READ_ONCE() and WRITE_ONCE() to prevent load/store tearing
> and to read/write mddev atomically.
>
> Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
> ---
>   drivers/md/md.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9bdd57324c37..3b38a565bffa 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2562,7 +2562,7 @@ static void md_kick_rdev_from_array(struct md_rdev *rdev)
>   	list_del_rcu(&rdev->same_set);
>   	pr_debug("md: unbind<%pg>\n", rdev->bdev);
>   	mddev_destroy_serial_pool(rdev->mddev, rdev);
> -	rdev->mddev = NULL;
> +	WRITE_ONCE(rdev->mddev, NULL);
>   	sysfs_remove_link(&rdev->kobj, "block");
>   	sysfs_put(rdev->sysfs_state);
>   	sysfs_put(rdev->sysfs_unack_badblocks);
> @@ -3646,7 +3646,7 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
>   	struct kernfs_node *kn = NULL;
>   	bool suspend = false;
>   	ssize_t rv;
> -	struct mddev *mddev = rdev->mddev;
> +	struct mddev *mddev = READ_ONCE(rdev->mddev);
>   
>   	if (!entry->store)
>   		return -EIO;

Re: [PATCH] md: get rdev->mddev with READ_ONCE()

Posted by Song Liu 1 year, 11 months ago

On Mon, Jan 29, 2024 at 5:55 AM Li Lingfeng <lilingfeng@huaweicloud.com> wrote:
>
> Friendly ping ...
>
> Thanks
>
> 在 2023/12/29 15:05, Li Lingfeng 写道:
> > From: Li Lingfeng <lilingfeng3@huawei.com>
> >
> > Users may get rdev->mddev by sysfs while rdev is releasing.
> > So use both READ_ONCE() and WRITE_ONCE() to prevent load/store tearing
> > and to read/write mddev atomically.
> >
> > Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>

Sorry for the delay. Applied to md-tmp-6.9 branch.

Thanks,
Song

Re: [PATCH] md: get rdev->mddev with READ_ONCE()

Posted by Yu Kuai 1 year, 11 months ago

在 2023/12/29 15:05, Li Lingfeng 写道:
> From: Li Lingfeng <lilingfeng3@huawei.com>
> 
> Users may get rdev->mddev by sysfs while rdev is releasing.
> So use both READ_ONCE() and WRITE_ONCE() to prevent load/store tearing
> and to read/write mddev atomically.

LGTM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
> 
> Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com>
> ---
>   drivers/md/md.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9bdd57324c37..3b38a565bffa 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -2562,7 +2562,7 @@ static void md_kick_rdev_from_array(struct md_rdev *rdev)
>   	list_del_rcu(&rdev->same_set);
>   	pr_debug("md: unbind<%pg>\n", rdev->bdev);
>   	mddev_destroy_serial_pool(rdev->mddev, rdev);
> -	rdev->mddev = NULL;
> +	WRITE_ONCE(rdev->mddev, NULL);
>   	sysfs_remove_link(&rdev->kobj, "block");
>   	sysfs_put(rdev->sysfs_state);
>   	sysfs_put(rdev->sysfs_unack_badblocks);
> @@ -3646,7 +3646,7 @@ rdev_attr_store(struct kobject *kobj, struct attribute *attr,
>   	struct kernfs_node *kn = NULL;
>   	bool suspend = false;
>   	ssize_t rv;
> -	struct mddev *mddev = rdev->mddev;
> +	struct mddev *mddev = READ_ONCE(rdev->mddev);
>   
>   	if (!entry->store)
>   		return -EIO;
>