Hi,
On Sat, Dec 05, 2020 at 04:54:01PM -0800, akpm@linux-foundation.org wrote:
The patch titled Subject: mm: initialize struct pages in reserved regions outside of the zone ranges has been added to the -mm tree. Its filename is mm-initialize-struct-pages-in-reserved-regions-outside-of-the-zone-ranges.patch
This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-initialize-struct-pages-in-rese... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-initialize-struct-pages-in-rese...
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From: Andrea Arcangeli aarcange@redhat.com Subject: mm: initialize struct pages in reserved regions outside of the zone ranges
Without this change, the pfn 0 isn't in any zone spanned range, and it's also not in any memory.memblock range, so the struct page of pfn 0 wasn't initialized and the PagePoison remained set when reserve_bootmem_region called __SetPageReserved, inducing a silent boot failure with DEBUG_VM (and correctly so, because the crash signaled the nodeid/nid of pfn 0 would be again wrong).
There's no enforcement that all memblock.reserved ranges must overlap memblock.memory ranges, so the memblock.reserved ranges also require an explicit initialization and the zones ranges need to be extended to include all memblock.reserved ranges with struct pages too or they'll be left uninitialized with PagePoison as it happened to pfn 0.
Link: https://lkml.kernel.org/r/20201205013238.21663-2-aarcange@redhat.com Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather that check each PFN") Signed-off-by: Andrea Arcangeli aarcange@redhat.com Cc: Mike Rapoport rppt@linux.ibm.com Cc: Baoquan He bhe@redhat.com Cc: David Hildenbrand david@redhat.com Cc: Mel Gorman mgorman@suse.de Cc: Michal Hocko mhocko@kernel.org Cc: Qian Cai cai@lca.pw Cc: Vlastimil Babka vbabka@suse.cz Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
include/linux/memblock.h | 17 ++++++++--- mm/debug.c | 3 + mm/memblock.c | 4 +- mm/page_alloc.c | 57 +++++++++++++++++++++++++++++-------- 4 files changed, 63 insertions(+), 18 deletions(-)
I don't see why we need all this complexity when a simple fixup was enough.
--- a/include/linux/memblock.h~mm-initialize-struct-pages-in-reserved-regions-outside-of-the-zone-ranges +++ a/include/linux/memblock.h
...
--- a/mm/page_alloc.c~mm-initialize-struct-pages-in-reserved-regions-outside-of-the-zone-ranges +++ a/mm/page_alloc.c
...
@@ -6227,7 +6233,7 @@ void __init __weak memmap_init(unsigned unsigned long zone, unsigned long range_start_pfn) {
- unsigned long start_pfn, end_pfn, next_pfn = 0;
- unsigned long start_pfn, end_pfn, prev_pfn = 0; unsigned long range_end_pfn = range_start_pfn + size; u64 pgcnt = 0; int i;
@@ -6235,7 +6241,7 @@ void __init __weak memmap_init(unsigned for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) { start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn); end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
next_pfn = clamp(next_pfn, range_start_pfn, range_end_pfn);
prev_pfn = clamp(prev_pfn, range_start_pfn, range_end_pfn);
if (end_pfn > start_pfn) { size = end_pfn - start_pfn; @@ -6243,10 +6249,10 @@ void __init __weak memmap_init(unsigned MEMINIT_EARLY, NULL, MIGRATE_MOVABLE); }
if (next_pfn < start_pfn)
pgcnt += init_unavailable_range(next_pfn, start_pfn,
if (prev_pfn < start_pfn)
pgcnt += init_unavailable_range(prev_pfn, start_pfn, zone, nid);
next_pfn = end_pfn;
}prev_pfn = end_pfn;
/* @@ -6256,12 +6262,31 @@ void __init __weak memmap_init(unsigned * considered initialized. Make sure that memmap has a well defined * state. */
- if (next_pfn < range_end_pfn)
pgcnt += init_unavailable_range(next_pfn, range_end_pfn,
- if (prev_pfn < range_end_pfn)
pgcnt += init_unavailable_range(prev_pfn, range_end_pfn, zone, nid);
- /*
* memblock.reserved isn't enforced to overlap with
* memblock.memory so initialize the struct pages for
* memblock.reserved too in case it wasn't overlapping.
*
* If any struct page associated with a memblock.reserved
* range isn't overlapping with a zone range, it'll be left
* uninitialized, ideally with PagePoison, and it'll be a more
* easily detectable error.
*/
- for_each_res_pfn_range(i, nid, &start_pfn, &end_pfn, NULL) {
start_pfn = clamp(start_pfn, range_start_pfn, range_end_pfn);
end_pfn = clamp(end_pfn, range_start_pfn, range_end_pfn);
if (end_pfn > start_pfn)
pgcnt += init_unavailable_range(start_pfn, end_pfn,
zone, nid);
- }
This means we are going iterate over all memory allocated before free_area_ini() from memblock extra time. One time here and another time in reserve_bootmem_region(). And this can be substantial for CMA and alloc_large_system_hash().
- if (pgcnt)
pr_info("%s: Zeroed struct page in unavailable ranges: %lld\n",
pr_info("%s: pages in unavailable ranges: %lld\n", zone_names[zone], pgcnt);
} @@ -6499,6 +6524,10 @@ void __init get_pfn_range_for_nid(unsign *start_pfn = min(*start_pfn, this_start_pfn); *end_pfn = max(*end_pfn, this_end_pfn); }
- for_each_res_pfn_range(i, nid, &this_start_pfn, &this_end_pfn, NULL) {
*start_pfn = min(*start_pfn, this_start_pfn);
*end_pfn = max(*end_pfn, this_end_pfn);
- }
if (*start_pfn == -1UL) *start_pfn = 0; @@ -7126,7 +7155,13 @@ unsigned long __init node_map_pfn_alignm */ unsigned long __init find_min_pfn_with_active_regions(void) {
- return PHYS_PFN(memblock_start_of_DRAM());
- /*
* reserved regions must be included so that their page
* structure can be part of a zone and obtain a valid zoneid
* before __SetPageReserved().
*/
- return min(PHYS_PFN(memblock_start_of_DRAM()),
PHYS_PFN(memblock.reserved.regions[0].base));
So this implies that reserved memory starts before memory. Don't you find this weird?
} /* _
Patches currently in -mm which might be from aarcange@redhat.com are
mm-initialize-struct-pages-in-reserved-regions-outside-of-the-zone-ranges.patch