On Thu, Apr 16, 2020 at 12:47:07PM +0200, David Hildenbrand wrote: > The comment in add_memory_resource() is stale: hotadd_new_pgdat() will > no longer call get_pfn_range_for_nid(), as a hotadded pgdat will simply > span no pages at all, until memory is moved to the zone/node via > move_pfn_range_to_zone() - e.g., when onlining memory blocks. > > The only archs that care about memblocks for hotplugged memory (either > for iterating over all system RAM or testing for memory validity) are > arm64, s390x, and powerpc - due to CONFIG_ARCH_KEEP_MEMBLOCK. Without > CONFIG_ARCH_KEEP_MEMBLOCK, we can simply stop messing with memblocks. > > For s390x, it seems to be fairly easy to avoid CONFIG_ARCH_KEEP_MEMBLOCK. > arm64 could rework most code (esp., pfn_valid(), valid_phys_addr_range() > and kexec_file_load()) to not require memblocks for hotplugged > memory. E.g., as hotplugged memory has no holes and can be identified > using !early_section(), arm64's variant of pfn_valid() could be reworked > fairly easily to not require memblocks for hotadded memory. powerpc might > be more involed. > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Baoquan He <bhe@xxxxxxxxxx> > Cc: Oscar Salvador <osalvador@xxxxxxx> > Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> > Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx> > Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > --- > mm/Kconfig | 3 +++ > mm/memory_hotplug.c | 13 +++++++------ > 2 files changed, 10 insertions(+), 6 deletions(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index c1acc34c1c35..a063fd9cdff4 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -136,6 +136,9 @@ config HAVE_FAST_GUP > depends on MMU > bool > > +# Don't discard allocated memory used to track "memory" and "reserved" memblocks > +# after early boot, so it can still be used to test for validity of memory. > +# Also, memblocks are updated with memory hot(un)plug. > config ARCH_KEEP_MEMBLOCK > bool > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 9b15ce465be2..104285ee9ae8 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1020,13 +1020,9 @@ int __ref add_memory_resource(int nid, struct resource *res) > > mem_hotplug_begin(); > > - /* > - * Add new range to memblock so that when hotadd_new_pgdat() is called > - * to allocate new pgdat, get_pfn_range_for_nid() will be able to find > - * this new range and calculate total pages correctly. The range will > - * be removed at hot-remove time. > - */ > +#ifdef CONFIG_ARCH_KEEP_MEMBLOCK > memblock_add_node(start, size, nid); > +#endif > > ret = __try_online_node(nid, false); > if (ret < 0) > @@ -1075,7 +1071,9 @@ int __ref add_memory_resource(int nid, struct resource *res) > /* rollback pgdat allocation and others */ > if (new_node) > rollback_node_hotadd(nid); > +#ifdef CONFIG_ARCH_KEEP_MEMBLOCK > memblock_remove(start, size); > +#endif > mem_hotplug_done(); > return ret; > } > @@ -1751,8 +1749,11 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) > mem_hotplug_begin(); > > arch_remove_memory(nid, start, size, NULL); > + > +#ifdef CONFIG_ARCH_KEEP_MEMBLOCK > memblock_free(start, size); > memblock_remove(start, size); > +#endif > __release_memory_resource(start, size); > > try_offline_node(nid); > -- > 2.25.1 > -- Sincerely yours, Mike.
