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

[Daniel Kiper <dkiper@xxxxxxxxxxxx>]

On Tue, Feb 08, 2011 at 06:25:38PM -0500, Konrad Rzeszutek Wilk wrote:
> 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.

No. Calls to lock_memory_hotplug()/unlock_memory_hotplug() were
moved from original add_memory() to add_registered_memory()
and new add_memory().

Daniel

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