Messages in this thread | | | Subject | Re: [PATCH v2 4/7] mm,memory_hotplug: Enforce struct page size to be multiple of PMD | From | David Hildenbrand <> | Date | Mon, 1 Mar 2021 11:24:57 +0100 |
| |
On 01.03.21 11:06, Oscar Salvador wrote: > On Thu, Feb 25, 2021 at 07:26:50PM +0100, David Hildenbrand wrote: >> On 09.02.21 14:38, Oscar Salvador wrote: >>> When struct page's size is not multiple of PMD, these do not get >>> fully populated when adding sections, hence two sections will >>> intersect the same the PMD. This goes against the vmemmap-per-device >>> premise, so reject it if that is the case. >>> >>> Signed-off-by: Oscar Salvador <osalvador@suse.de> >>> --- >>> mm/memory_hotplug.c | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 95695483a622..d3fb036d33fd 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -57,10 +57,11 @@ static __meminit int memmap_on_memory_store(const char *val, >>> const struct kernel_param *kp) >>> { >>> /* >>> - * Fail silently in case we cannot enable it due to platform constraints. >>> + * Fail silently in case we cannot enable it due to system constraints. >>> * User can always check whether it is enabled or not via /sys/module. >>> */ >>> - if (!IS_ENABLED(CONFIG_ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE)) >>> + if (!IS_ENABLED(CONFIG_ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE) || >>> + (PMD_SIZE % sizeof(struct page))) >>> return 0; >>> return param_set_bool(val, kp); >>> >> >> Squash that into #1 - it's part of basic operation. > > Just to be sure we are on the same page. > You mean to move this patch and patch#5 into the runtime check in > mhp_supports_memmap_on_memory(), right?
Yes, then the compiler might even be able to figure out that what follows the check is dead code.
-- Thanks,
David / dhildenb
| |