Re: [RESEND PATCH] drivers/md: Use rcu_dereference() for accessing rcu pointer

From: Paul E. McKenney
Date: Sun Sep 28 2014 - 17:43:37 EST


On Sun, Sep 28, 2014 at 11:05:04AM -0400, Pranith Kumar wrote:
> Got Paul's email wrong the first time.
>
> The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference()
> while accessing it.
>
> Signed-off-by: Pranith Kumar <bobby.prani@xxxxxxxxx>

OK, I now have all three queued (including the extraneous first line of
the commit log above...), will see what 0day thinks of it.

Thanx, Paul

> ---
> drivers/md/dm.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 746411b..fbdf0bb 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -2211,7 +2211,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
>
> merge_is_optional = dm_table_merge_is_optional(t);
>
> - old_map = md->map;
> + old_map = rcu_dereference(md->map);
> rcu_assign_pointer(md->map, t);
> md->immutable_target_type = dm_table_get_immutable_target_type(t);
>
> @@ -2230,7 +2230,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> */
> static struct dm_table *__unbind(struct mapped_device *md)
> {
> - struct dm_table *map = md->map;
> + struct dm_table *map = rcu_dereference(md->map);
>
> if (!map)
> return NULL;
> @@ -2624,7 +2624,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
> goto out_unlock;
> }
>
> - map = md->map;
> + map = rcu_dereference(md->map);
>
> /*
> * DMF_NOFLUSH_SUSPENDING must be set before presuspend.
> @@ -2718,7 +2718,7 @@ int dm_resume(struct mapped_device *md)
> if (!dm_suspended_md(md))
> goto out;
>
> - map = md->map;
> + map = rcu_dereference(md->map);
> if (!map || !dm_table_get_size(map))
> goto out;
>
> --
> 1.9.1
>

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