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> --- 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
