* FAILED: patch "[PATCH] mm/hugetlb_cma: round up per_node before logging it" failed to apply to 6.12-stable tree
@ 2026-05-12 13:17 gregkh
2026-05-14 12:41 ` [PATCH 6.12.y] mm/hugetlb_cma: round up per_node before logging it Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: gregkh @ 2026-05-12 13:17 UTC (permalink / raw)
To: ekffu200098, akpm, david, muchun.song, osalvador, stable; +Cc: stable
The patch below does not apply to the 6.12-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 <stable@vger.kernel.org>.
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-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 8f5ce56b76303c55b78a87af996e2e0f8535f979
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026051241-magnifier-bunkmate-b408@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 8f5ce56b76303c55b78a87af996e2e0f8535f979 Mon Sep 17 00:00:00 2001
From: Sang-Heon Jeon <ekffu200098@gmail.com>
Date: Wed, 22 Apr 2026 23:33:53 +0900
Subject: [PATCH] mm/hugetlb_cma: round up per_node before logging it
When the user requests a total hugetlb CMA size without per-node
specification, hugetlb_cma_reserve() computes per_node from
hugetlb_cma_size and the number of nodes that have memory
per_node = DIV_ROUND_UP(hugetlb_cma_size,
nodes_weight(hugetlb_bootmem_nodes));
The reservation loop later computes
size = round_up(min(per_node, hugetlb_cma_size - reserved),
PAGE_SIZE << order);
So the actually reserved per_node size is multiple of (PAGE_SIZE <<
order), but the logged per_node is not rounded up, so it may be smaller
than the actual reserved size.
For example, as the existing comment describes, if a 3 GB area is
requested on a machine with 4 NUMA nodes that have memory, 1 GB is
allocated on the first three nodes, but the printed log is
hugetlb_cma: reserve 3072 MiB, up to 768 MiB per node
Round per_node up to (PAGE_SIZE << order) before logging so that the
printed log always matches the actual reserved size. No functional change
to the actual reservation size, as the following case analysis shows
1. remaining (hugetlb_cma_size - reserved) >= rounded per_node
- AS-IS: min() picks unrounded per_node;
round_up() returns rounded per_node
- TO-BE: min() picks rounded per_node;
round_up() returns rounded per_node (no-op)
2. remaining < unrounded per_node
- AS-IS: min() picks remaining;
round_up() returns round_up(remaining)
- TO-BE: min() picks remaining;
round_up() returns round_up(remaining)
3. unrounded per_node <= remaining < rounded per_node
- AS-IS: min() picks unrounded per_node;
round_up() returns rounded per_node
- TO-BE: min() picks remaining;
round_up() returns round_up(remaining) equals rounded per_node
Link: https://lore.kernel.org/20260422143353.852257-1-ekffu200098@gmail.com
Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma") # 5.7
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/mm/hugetlb_cma.c b/mm/hugetlb_cma.c
index f83ae4998990..7693ccefd0c6 100644
--- a/mm/hugetlb_cma.c
+++ b/mm/hugetlb_cma.c
@@ -204,6 +204,7 @@ void __init hugetlb_cma_reserve(void)
*/
per_node = DIV_ROUND_UP(hugetlb_cma_size,
nodes_weight(hugetlb_bootmem_nodes));
+ per_node = round_up(per_node, PAGE_SIZE << order);
pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n",
hugetlb_cma_size / SZ_1M, per_node / SZ_1M);
}
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH 6.12.y] mm/hugetlb_cma: round up per_node before logging it
2026-05-12 13:17 FAILED: patch "[PATCH] mm/hugetlb_cma: round up per_node before logging it" failed to apply to 6.12-stable tree gregkh
@ 2026-05-14 12:41 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-05-14 12:41 UTC (permalink / raw)
To: stable
Cc: Sang-Heon Jeon, Muchun Song, David Hildenbrand, Oscar Salvador,
Andrew Morton, Sasha Levin
From: Sang-Heon Jeon <ekffu200098@gmail.com>
[ Upstream commit 8f5ce56b76303c55b78a87af996e2e0f8535f979 ]
When the user requests a total hugetlb CMA size without per-node
specification, hugetlb_cma_reserve() computes per_node from
hugetlb_cma_size and the number of nodes that have memory
per_node = DIV_ROUND_UP(hugetlb_cma_size,
nodes_weight(hugetlb_bootmem_nodes));
The reservation loop later computes
size = round_up(min(per_node, hugetlb_cma_size - reserved),
PAGE_SIZE << order);
So the actually reserved per_node size is multiple of (PAGE_SIZE <<
order), but the logged per_node is not rounded up, so it may be smaller
than the actual reserved size.
For example, as the existing comment describes, if a 3 GB area is
requested on a machine with 4 NUMA nodes that have memory, 1 GB is
allocated on the first three nodes, but the printed log is
hugetlb_cma: reserve 3072 MiB, up to 768 MiB per node
Round per_node up to (PAGE_SIZE << order) before logging so that the
printed log always matches the actual reserved size. No functional change
to the actual reservation size, as the following case analysis shows
1. remaining (hugetlb_cma_size - reserved) >= rounded per_node
- AS-IS: min() picks unrounded per_node;
round_up() returns rounded per_node
- TO-BE: min() picks rounded per_node;
round_up() returns rounded per_node (no-op)
2. remaining < unrounded per_node
- AS-IS: min() picks remaining;
round_up() returns round_up(remaining)
- TO-BE: min() picks remaining;
round_up() returns round_up(remaining)
3. unrounded per_node <= remaining < rounded per_node
- AS-IS: min() picks unrounded per_node;
round_up() returns rounded per_node
- TO-BE: min() picks remaining;
round_up() returns round_up(remaining) equals rounded per_node
Link: https://lore.kernel.org/20260422143353.852257-1-ekffu200098@gmail.com
Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma") # 5.7
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ applied the single-line addition to mm/hugetlb.c since mm/hugetlb_cma.c didn't exist yet in 6.12 ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
mm/hugetlb.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 9577922c976cd..c5975b411afbb 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7689,6 +7689,7 @@ void __init hugetlb_cma_reserve(int order)
* let's allocate 1 GB on first three nodes and ignore the last one.
*/
per_node = DIV_ROUND_UP(hugetlb_cma_size, nr_online_nodes);
+ per_node = round_up(per_node, PAGE_SIZE << order);
pr_info("hugetlb_cma: reserve %lu MiB, up to %lu MiB per node\n",
hugetlb_cma_size / SZ_1M, per_node / SZ_1M);
}
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-05-14 12:41 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-05-12 13:17 FAILED: patch "[PATCH] mm/hugetlb_cma: round up per_node before logging it" failed to apply to 6.12-stable tree gregkh
2026-05-14 12:41 ` [PATCH 6.12.y] mm/hugetlb_cma: round up per_node before logging it Sasha Levin
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.