2023-12-29 07:24:47

by Li Lingfeng

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

From: Li Lingfeng <[email protected]>

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 <[email protected]>
---
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

2024-01-02 06:16:59

by Yu Kuai

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

?? 2023/12/29 15:05, Li Lingfeng д??:
> From: Li Lingfeng <[email protected]>
>
> 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 <[email protected]>
>
> Signed-off-by: Li Lingfeng <[email protected]>
> ---
> 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;
>

2024-01-29 13:56:16

by Li Lingfeng

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

Friendly ping ...

Thanks

在 2023/12/29 15:05, Li Lingfeng 写道:
> From: Li Lingfeng <[email protected]>
>
> 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 <[email protected]>
> ---
> 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;

2024-01-30 06:49:15

by Song Liu

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

On Mon, Jan 29, 2024 at 5:55 AM Li Lingfeng <lilingfeng@huaweicloudcom> wrote:
>
> Friendly ping ...
>
> Thanks
>
> 在 2023/12/29 15:05, Li Lingfeng 写道:
> > From: Li Lingfeng <[email protected]>
> >
> > 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 <[email protected]>

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

Thanks,
Song