Re: [PATCH v3 07/26] mm: drop CONFIG_HAVE_ARCH_NODEDATA_EXTENSION

Mike Rapoport
2024-08-05T14:42:01Z

On Sun, Aug 04, 2024 at 04:11:19PM +0100, Jonathan Cameron wrote:
> On Sun, 4 Aug 2024 10:24:15 +0300
> Mike Rapoport <rppt@kernel.org> wrote:
>
> > On Sat, Aug 03, 2024 at 11:58:13AM -0700, Andrew Morton wrote:
> > > On Fri, 2 Aug 2024 10:49:22 +0100 Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:
> > >
> > > > > --- a/mm/mm_init.c
> > > > > +++ b/mm/mm_init.c
> > > > > @@ -1838,11 +1838,10 @@ void __init free_area_init(unsigned long *max_zone_pfn)
> > > > >
> > > > > if (!node_online(nid)) {
> > > > > /* Allocator not initialized yet */
> > > > > - pgdat = arch_alloc_nodedata(nid);
> > > > > + pgdat = memblock_alloc(sizeof(*pgdat), SMP_CACHE_BYTES);
> > > > > if (!pgdat)
> > > > > panic("Cannot allocate %zuB for node %d.\n",
> > > > > sizeof(*pgdat), nid);
> > > > > - arch_refresh_nodedata(nid, pgdat);
> > > >
> > > > This allocates pgdat but never sets node_data[nid] to it
> > > > and promptly leaks it on the line below.
> > > >
> > > > Just to sanity check this I spun up a qemu machine with no memory
> > > > initially present on some nodes and it went boom as you'd expect.
> > > >
> > > > I tested with addition of
> > > > NODE_DATA(nid) = pgdat;
> > > > and it all seems to work as expected.
> > >
> > > Thanks, I added that. It blew up on x86_64 allnoconfig because
> > > node_data[] (and hence NODE_DATA()) isn't an lvalue when CONFIG_NUMA=n.
> > >
> > > I'll put some #ifdef CONFIG_NUMAs in there for now but
> > >
> > > a) NODE_DATA() is upper-case. Implies "constant". Shouldn't be assigned to.
> > >
> > > b) NODE_DATA() should be non-lvalue when CONFIG_NUMA=y also. But no,
> > > we insist on implementing things in cpp instead of in C.
> >
> > This looks like a candidate for a separate tree-wide cleanup.
> >
> > > c) In fact assigning to anything which ends in "()" is nuts. Please
> > > clean up my tempfix.
> > >
> > > c) Mike, generally I'm wondering if there's a bunch of code here
> > > which isn't needed on CONFIG_NUMA=n. Please check all of this for
> > > unneeded bloatiness.
> >
> > I believe the patch addresses your concerns, just with this the commit log
> > needs update. Instead of
> >
> > Replace the call to arch_alloc_nodedata() in free_area_init() with
> > memblock_alloc(), remove arch_refresh_nodedata() and cleanup
> > include/linux/memory_hotplug.h from the associated ifdefery.
> >
> > it should be
> >
> > Replace the call to arch_alloc_nodedata() in free_area_init() with a
> > new helper alloc_offline_node_data(), remove arch_refresh_nodedata()
> > and cleanup include/linux/memory_hotplug.h from the associated
> > ifdefery.
> >
> > I can send an updated patch if you prefer.
> This solution looks good to me - except for a Freudian typo that means it won't
> compile :)

Right :)

I'll post v4 after kbuild confirms it compiles :)

> Jonathan
>
> >
> > diff --git a/include/linux/numa.h b/include/linux/numa.h
> > index 3b12d8ca0afd..5a749fd67f39 100644
> > --- a/include/linux/numa.h
> > +++ b/include/linux/numa.h
> > @@ -34,6 +34,7 @@ extern struct pglist_data *node_data[];
> > #define NODE_DATA(nid) (node_data[nid])
> >
> > void __init alloc_node_data(int nid);
> > +void __init alloc_offline_node_data(int nit);
> >
> > /* Generic implementation available */
> > int numa_nearest_node(int node, unsigned int state);
> > @@ -62,6 +63,8 @@ static inline int phys_to_target_node(u64 start)
> > {
> > return 0;
> > }
> > +
> > +static inline void alloc_offline_node_data(int nit) {}
> nid
> > #endif
> >
> > #define numa_map_to_online_node(node) numa_nearest_node(node, N_ONLINE)
> > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > index bcc2f2dd8021..2785be04e7bb 100644
> > --- a/mm/mm_init.c
> > +++ b/mm/mm_init.c
> > @@ -1836,13 +1836,8 @@ void __init free_area_init(unsigned long *max_zone_pfn)
> > for_each_node(nid) {
> > pg_data_t *pgdat;
> >
> > - if (!node_online(nid)) {
> > - /* Allocator not initialized yet */
> > - pgdat = memblock_alloc(sizeof(*pgdat), SMP_CACHE_BYTES);
> > - if (!pgdat)
> > - panic("Cannot allocate %zuB for node %d.\n",
> > - sizeof(*pgdat), nid);
> > - }
> > + if (!node_online(nid))
> > + alloc_offline_node_data(nid);
> >
> > pgdat = NODE_DATA(nid);
> > free_area_init_node(nid);
> > diff --git a/mm/numa.c b/mm/numa.c
> > index da27eb151dc5..07e486a977c7 100644
> > --- a/mm/numa.c
> > +++ b/mm/numa.c
> > @@ -34,6 +34,18 @@ void __init alloc_node_data(int nid)
> > memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
> > }
> >
> > +void __init alloc_offline_node_data(int nit)
>
> nid
>
> > +{
> > + pg_data_t *pgdat;
> > +
> > + pgdat = memblock_alloc(sizeof(*pgdat), SMP_CACHE_BYTES);
> > + if (!pgdat)
> > + panic("Cannot allocate %zuB for node %d.\n",
> > + sizeof(*pgdat), nid);
> > +
> > + node_data[nid] = pgdat;
> > +}
> > +
> > /* Stub functions: */
> >
> > #ifndef memory_add_physaddr_to_nid
> >
> >
> >
>
>

--
Sincerely yours,
Mike.