[Xen-devel] Re: [PATCH R3 1/7] mm: Add add_registered_memory() to memory hotplug API

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Feb 03, 2011 at 05:25:14PM +0100, Daniel Kiper wrote:
> add_registered_memory() adds memory ealier registered
> as memory resource. It is required by memory hotplug
> for Xen guests, however it could be used also by other
> modules.
> 
> Signed-off-by: Daniel Kiper <dkiper@xxxxxxxxxxxx>
> ---
>  include/linux/memory_hotplug.h |    1 +
>  mm/memory_hotplug.c            |   50 ++++++++++++++++++++++++++++++---------
>  2 files changed, 39 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 8122018..fe63912 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -223,6 +223,7 @@ static inline int is_mem_section_removable(unsigned long 
> pfn,
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>  
>  extern int mem_online_node(int nid);
> +extern int add_registered_memory(int nid, u64 start, u64 size);
>  extern int add_memory(int nid, u64 start, u64 size);
>  extern int arch_add_memory(int nid, u64 start, u64 size);
>  extern int remove_memory(u64 start, u64 size);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 321fc74..7947bdf 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -532,20 +532,12 @@ out:
>  }
>  
>  /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> -int __ref add_memory(int nid, u64 start, u64 size)
> +static int __ref __add_memory(int nid, u64 start, u64 size)
>  {
>       pg_data_t *pgdat = NULL;
>       int new_pgdat = 0;
> -     struct resource *res;
>       int ret;
>  
> -     lock_memory_hotplug();
> -
> -     res = register_memory_resource(start, size);
> -     ret = -EEXIST;
> -     if (!res)
> -             goto out;
> -
>       if (!node_online(nid)) {
>               pgdat = hotadd_new_pgdat(nid, start);
>               ret = -ENOMEM;
> @@ -579,14 +571,48 @@ int __ref add_memory(int nid, u64 start, u64 size)
>       goto out;
>  
>  error:
> -     /* rollback pgdat allocation and others */
> +     /* rollback pgdat allocation */
>       if (new_pgdat)
>               rollback_node_hotadd(nid, pgdat);
> -     if (res)
> -             release_memory_resource(res);
> +
> +out:
> +     return ret;
> +}
> +
> +int add_registered_memory(int nid, u64 start, u64 size)
> +{
> +     int ret;
> +
> +     lock_memory_hotplug();
> +     ret = __add_memory(nid, start, size);
> +     unlock_memory_hotplug();

Isn't this a duplicate call to the mutex?
The __add_memory does an unlock_memory_hotplug when it finishes
and then you do another unlock_memory_hotplug here too.


> +
> +     return ret;
> +}
> +EXPORT_SYMBOL_GPL(add_registered_memory);
> +
> +int add_memory(int nid, u64 start, u64 size)
> +{
> +     int ret = -EEXIST;
> +     struct resource *res;
> +
> +     lock_memory_hotplug();
> +
> +     res = register_memory_resource(start, size);
> +
> +     if (!res)
> +             goto out;
> +
> +     ret = __add_memory(nid, start, size);

Ditto here. When __add_memory finishes the unlock_memory_hotplug
has been called, but you end up doing it in the out: label
too?

> +
> +     if (!ret)
> +             goto out;
> +
> +     release_memory_resource(res);
>  
>  out:
>       unlock_memory_hotplug();
> +
>       return ret;
>  }
>  EXPORT_SYMBOL_GPL(add_memory);
> -- 
> 1.5.6.5

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