The quilt patch titled
Subject: mm/hugetlb: fix surplus pages in dissolve_free_huge_page()
has been removed from the -mm tree. Its filename was
mm-hugetlb-fix-surplus-pages-in-dissolve_free_huge_page.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
Subject: mm/hugetlb: fix surplus pages in dissolve_free_huge_page()
Date: Tue, 4 Mar 2025 21:21:06 +0800
In dissolve_free_huge_page(), free huge pages are dissolved without
adjusting surplus count. However, free huge pages may be accounted as
surplus pages, and will lead to wrong surplus count.
I reproduce this issue on qemu. The steps are:
1) Node1 is memory-less at first. Hot-add memory to node1 by executing
the two commands in qemu monitor:
object_add memory-backend-ram,id=mem1,size=1G
device_add pc-dimm,id=dimm1,memdev=mem1,node=1
2) online one memory block of Node1 withï¼?
echo online_movable > /sys/devices/system/node/node1/memoryX/state
3) create 64 huge pages for node1
4) run a program to reserve (don't consume) all the huge pages
5) echo 0 > nr_huge_pages for node1. After this step, free huge pages in
Node1 are surplus.
6) create 80 huge pages for node0
7) offline memory of node1, The memory range to offline contains the free
surplus huge pages created in step3) ~ step5)
echo offline > /sys/devices/system/node/node1/memoryX/state
8) kill the program in step 4)
The result:
Node0 Node1
total 80 0
free 80 0
surplus 0 61
To fix it, adjust surplus when destroying huge pages if the node has
surplus pages in dissolve_free_hugetlb_folio().
The result with this patch:
Node0 Node1
total 80 0
free 80 0
surplus 0 0
Link: https://lkml.kernel.org/r/20250304132106.2872754-1-tujinjiang@xxxxxxxxxx
Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Oscar Salvador <osalvador@xxxxxxx>
Cc: Jinjiang Tu <tujinjiang@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Nanyong Sun <sunnanyong@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/mm/hugetlb.c~mm-hugetlb-fix-surplus-pages-in-dissolve_free_huge_page
+++ a/mm/hugetlb.c
@@ -2135,6 +2135,8 @@ retry:
if (!folio_ref_count(folio)) {
struct hstate *h = folio_hstate(folio);
+ bool adjust_surplus = false;
+
if (!available_huge_pages(h))
goto out;
@@ -2157,7 +2159,9 @@ retry:
goto retry;
}
- remove_hugetlb_folio(h, folio, false);
+ if (h->surplus_huge_pages_node[folio_nid(folio)])
+ adjust_surplus = true;
+ remove_hugetlb_folio(h, folio, adjust_surplus);
h->max_huge_pages--;
spin_unlock_irq(&hugetlb_lock);
@@ -2177,7 +2181,7 @@ retry:
rc = hugetlb_vmemmap_restore_folio(h, folio);
if (rc) {
spin_lock_irq(&hugetlb_lock);
- add_hugetlb_folio(h, folio, false);
+ add_hugetlb_folio(h, folio, adjust_surplus);
h->max_huge_pages++;
goto out;
}
_
Patches currently in -mm which might be from tujinjiang@xxxxxxxxxx are
mm-contig_alloc-fix-alloc_contig_range-when-__gfp_comp-and-order-max_order.patch
mm-hugetlb-fix-set_max_huge_pages-when-there-are-surplus-pages.patch
