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

Jonathan Cameron
2024-08-04T15:12:06Z

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 :)

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