FAILED: patch "[PATCH] mm/hugetlb: do not dissolve gigantic pages without runtime" failed to apply to 6.6-stable tree

PATCH New [email protected] 2 participants 5 messages Sep 29 – Sep 30

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Stable branch Memory management HugeTLB

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[email protected]

author maintainer

2026-09-29 08:27 UTC #0 lore raw

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x a363c62a653cc8b3e21da9545fa4e028ef50f9c3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026092904-singer-headphone-fefa@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a363c62a653cc8b3e21da9545fa4e028ef50f9c3 Mon Sep 17 00:00:00 2001
From: Longlong Xia <[email protected]>
Date: Sun, 23 Aug 2026 12:40:51 +0800
Subject: [PATCH] mm/hugetlb: do not dissolve gigantic pages without runtime
support

dissolve_free_hugetlb_folio() doesn't check hstate_is_gigantic_no_runtime(h) though remove_hugetlb_folio()/ update_and_free_hugetlb_folio() silently bail for such folios, so it frees a still-listed folio and, on vmemmap restore failure, the add_hugetlb_folio() rollback corrupts the free list.

Link https://lore.kernel.org/[email protected] open here

Fixes 6eb4e88a6d27 ("hugetlb: create remove_hugetlb_page() to separate functionality")

Signed-off-by Longlong Xia <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Assisted-by Codex:gpt-5.6-sol

Acked-by Muchun Song <[email protected]>

Cc David Hildenbrand <[email protected]>

Cc Miaohe Lin <[email protected]>

Cc Michal Hocko <[email protected]>

Cc Oscar Salvador <[email protected]>

Cc <[email protected]>

mm/hugetlb.c +9 -0

index 4f6f58bf3db6..d28972cd33f5 100644
@@ -1967,6 +1967,15 @@ int dissolve_free_hugetlb_folio(struct folio *folio)
 		struct hstate *h = folio_hstate(folio);
 		bool adjust_surplus = false;
 
+		/*
+		 * remove_hugetlb_folio()/update_and_free_hugetlb_folio() bail
+		 * for gigantic hstates without runtime support, so dissolving one
+		 * here would leave it on the free list and, on vmemmap restore
+		 * failure, the add_hugetlb_folio() rollback corrupts that list.
+		 */
+		if (hstate_is_gigantic_no_runtime(h))
+			goto out;
+
 		if (!available_huge_pages(h))
 			goto out;

Sasha Levin

maintainer

2026-09-29 19:47 UTC #1 lore raw

PATCH 1/1 mm/hugetlb: do not dissolve gigantic pages without runtime support

From: Longlong Xia <[email protected]>

[ Upstream commit a363c62a653cc8b3e21da9545fa4e028ef50f9c3 ]

Link https://lore.kernel.org/[email protected] open here

Fixes 6eb4e88a6d27 ("hugetlb: create remove_hugetlb_page() to separate functionality")

Signed-off-by Longlong Xia <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Assisted-by Codex:gpt-5.6-sol

Acked-by Muchun Song <[email protected]>

Cc David Hildenbrand <[email protected]>

Cc Miaohe Lin <[email protected]>

Cc Michal Hocko <[email protected]>

Cc Oscar Salvador <[email protected]>

Cc <[email protected]>

[ replaced unavailable hstate_is_gigantic_no_runtime() with hstate_is_gigantic(h) && !gigantic_page_runtime_supported(). ]

Signed-off-by Sasha Levin <[email protected]>

---
 mm/hugetlb.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

mm/hugetlb.c +10 -0

index bd8752a5356b7..6004261af2e80 100644
@@ -2303,6 +2303,16 @@ int dissolve_free_huge_page(struct page *page)
 
 	if (!folio_ref_count(folio)) {
 		struct hstate *h = folio_hstate(folio);
+
+		/*
+		 * remove_hugetlb_folio()/update_and_free_hugetlb_folio() bail
+		 * for gigantic hstates without runtime support, so dissolving one
+		 * here would leave it on the free list and, on vmemmap restore
+		 * failure, the add_hugetlb_folio() rollback corrupts that list.
+		 */
+		if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+			goto out;
+
 		if (!available_huge_pages(h))
 			goto out;

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-30 00:04 UTC #2 lore raw

PATCH 1/3 mm/hugetlb: fix surplus pages in dissolve_free_huge_page()

In reply to [email protected]

From: Jinjiang Tu <[email protected]>

[ Upstream commit cb402bbdabcaa5a765068c5b8673bbfc1c264242 ]

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 with：
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/[email protected] open here

Fixes c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage")

Signed-off-by Jinjiang Tu <[email protected]>

Acked-by David Hildenbrand <[email protected]>

Acked-by Oscar Salvador <[email protected]>

Cc Jinjiang Tu <[email protected]>

Cc Kefeng Wang <[email protected]>

Cc Muchun Song <[email protected]>

Cc Nanyong Sun <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Stable-dep-of: a363c62a653c ("mm/hugetlb: do not dissolve gigantic pages without runtime support")

Signed-off-by Sasha Levin <[email protected]>

---
 mm/hugetlb.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

mm/hugetlb.c +6 -2

index bd8752a5356b7..2b12644e47848 100644
@@ -2303,6 +2303,8 @@ int dissolve_free_huge_page(struct page *page)
 
 	if (!folio_ref_count(folio)) {
 		struct hstate *h = folio_hstate(folio);
+		bool adjust_surplus = false;
+
 		if (!available_huge_pages(h))
 			goto out;

@@ -2325,7 +2327,9 @@ int dissolve_free_huge_page(struct page *page)
 			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);

@@ -2342,7 +2346,7 @@ int dissolve_free_huge_page(struct page *page)
 			update_and_free_hugetlb_folio(h, folio, false);
 		} else {
 			spin_lock_irq(&hugetlb_lock);
-			add_hugetlb_folio(h, folio, false);
+			add_hugetlb_folio(h, folio, adjust_surplus);
 			h->max_huge_pages++;
 			spin_unlock_irq(&hugetlb_lock);
 		}

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-30 00:04 UTC #3 lore raw

PATCH 2/3 mm/hugetlb: create hstate_is_gigantic_no_runtime helper

From: Usama Arif <[email protected]>

[ Upstream commit a743e0af503a633e4ca68a100d9b2a1a071fe8ae ]

This is a common condition used to skip operations that cannot be performed on gigantic pages when runtime support is disabled. This helper is introduced as the condition will exist even more when allowing "overcommit" of gigantic hugepages. No functional change intended with this patch.

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by Usama Arif <[email protected]>

Reviewed-by Shakeel Butt <[email protected]>

Reviewed-by Kefeng Wang <[email protected]>

Acked-by David Hildenbrand <[email protected]>

Acked-by Oscar Salvador <[email protected]>

Cc Johannes Weiner <[email protected]>

Cc Muchun Song <[email protected]>

Cc Rik van Riel <[email protected]>

Cc SeongJae Park <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

For the 6.6 dependency backport, implement the shared predicate as a macro so no new functions are introduced. Its argument is evaluated once and the original short-circuit condition is preserved at all five existing call sites. Keep the 6.6 freeing and CMA paths: the upstream hugetlb_free_folio() context and clear_flag local belong to later changes and are not needed here.

This supplies hstate_is_gigantic_no_runtime() for a363c62a653c without changing the existing hugepage behavior or importing unrelated refactors.

Stable-dep-of: a363c62a653c ("mm/hugetlb: do not dissolve gigantic pages without runtime support")

Signed-off-by Sasha Levin <[email protected]>

---
 mm/hugetlb.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

mm/hugetlb.c +14 -5

index 2b12644e47848..f5b434f2ac474 100644
@@ -102,6 +102,15 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
 		unsigned long start, unsigned long end, bool take_locks);
 static struct resv_map *vma_resv_map(struct vm_area_struct *vma);
 
+/*
+ * Check if the hstate represents gigantic pages but gigantic page
+ * runtime support is not available. This is a common condition used to
+ * skip operations that cannot be performed on gigantic pages when runtime
+ * support is disabled.
+ */
+#define hstate_is_gigantic_no_runtime(h) \
+	(hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+
 static inline bool subpool_is_free(struct hugepage_subpool *spool)
 {
 	if (spool->count)

@@ -1656,7 +1665,7 @@ static void __remove_hugetlb_folio(struct hstate *h, struct folio *folio,
 	VM_BUG_ON_FOLIO(hugetlb_cgroup_from_folio_rsvd(folio), folio);
 
 	lockdep_assert_held(&hugetlb_lock);
-	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+	if (hstate_is_gigantic_no_runtime(h))
 		return;
 
 	list_del(&folio->lru);

@@ -1750,7 +1759,7 @@ static void add_hugetlb_folio(struct hstate *h, struct folio *folio,
 static void __update_and_free_hugetlb_folio(struct hstate *h,
 						struct folio *folio)
 {
-	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+	if (hstate_is_gigantic_no_runtime(h))
 		return;
 
 	/*

@@ -2659,7 +2668,7 @@ static void return_unused_surplus_pages(struct hstate *h,
 	/* Uncommit the reservation */
 	h->resv_huge_pages -= unused_resv_pages;
 
-	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+	if (hstate_is_gigantic_no_runtime(h))
 		goto out;
 
 	/*

@@ -3376,7 +3385,7 @@ static void __init hugetlb_init_hstates(void)
 		 * - If CMA allocation is possible, we can not demote
 		 *   HUGETLB_PAGE_ORDER or smaller size pages.
 		 */
-		if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+		if (hstate_is_gigantic_no_runtime(h))
 			continue;
 		if (hugetlb_cma_size && h->order <= HUGETLB_PAGE_ORDER)
 			continue;

@@ -3773,7 +3782,7 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
 	int err;
 	nodemask_t nodes_allowed, *n_mask;
 
-	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
+	if (hstate_is_gigantic_no_runtime(h))
 		return -EINVAL;
 
 	if (nid == NUMA_NO_NODE) {

Signature · 1 line

2.53.0

Sasha Levin

maintainer

2026-09-30 00:04 UTC #4 lore raw

PATCH 3/3 mm/hugetlb: do not dissolve gigantic pages without runtime support

In reply to Sasha Levin

From: Longlong Xia <[email protected]>

[ Upstream commit a363c62a653cc8b3e21da9545fa4e028ef50f9c3 ]

Link https://lore.kernel.org/[email protected] open here

Fixes 6eb4e88a6d27 ("hugetlb: create remove_hugetlb_page() to separate functionality")

Signed-off-by Longlong Xia <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Assisted-by Codex:gpt-5.6-sol

Acked-by Muchun Song <[email protected]>

Cc David Hildenbrand <[email protected]>

Cc Miaohe Lin <[email protected]>

Cc Michal Hocko <[email protected]>

Cc Oscar Salvador <[email protected]>

Cc <[email protected]>

Signed-off-by Sasha Levin <[email protected]>

---
 mm/hugetlb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

mm/hugetlb.c +9 -0

index f5b434f2ac474..02bc36d52e2e5 100644
@@ -2314,6 +2314,15 @@ int dissolve_free_huge_page(struct page *page)
 		struct hstate *h = folio_hstate(folio);
 		bool adjust_surplus = false;
 
+		/*
+		 * remove_hugetlb_folio()/update_and_free_hugetlb_folio() bail
+		 * for gigantic hstates without runtime support, so dissolving one
+		 * here would leave it on the free list and, on vmemmap restore
+		 * failure, the add_hugetlb_folio() rollback corrupts that list.
+		 */
+		if (hstate_is_gigantic_no_runtime(h))
+			goto out;
+
 		if (!available_huge_pages(h))
 			goto out;

Signature · 1 line

2.53.0