+ mm-hugetlb-use-kvmalloc_objs-for-hugetlb_fault_mutex_table.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/hugetlb: use kvmalloc_objs for hugetlb_fault_mutex_table
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hugetlb-use-kvmalloc_objs-for-hugetlb_fault_mutex_table.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb-use-kvmalloc_objs-for-hugetlb_fault_mutex_table.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Subject: mm/hugetlb: use kvmalloc_objs for hugetlb_fault_mutex_table
Date: Tue, 6 Oct 2026 21:31:28 +0530

On systems/VMs with a large number of CPUs (e.g.  4096), hugetlb_init()
computes num_fault_mutexes = roundup_pow_of_two(8 * num_possible_cpus()) =
32768.  The subsequent kmalloc for the mutex table can exceed
MAX_PAGE_ORDER when struct mutex is enlarged by debug options like
CONFIG_DEBUG_MUTEXES and CONFIG_DEBUG_LOCK_ALLOC, resulting in:

  WARNING: at __alloc_frozen_pages_noprof (order > MAX_PAGE_ORDER)
  kernel BUG at mm/hugetlb.c (BUG_ON(!hugetlb_fault_mutex_table))
  Kernel panic - not syncing: Fatal exception

Switch to kvmalloc_objs() so the allocation falls back to vmalloc when the
contiguous physical allocation is too large.  The table is only accessed
by index, so virtual contiguity is sufficient.

Link: https://lore.kernel.org/20261006160128.31447-1-dheerajkumar.srivastava@amd.com
Fixes: 8382d914ebf7 ("mm, hugetlb: improve page-fault scalability")
Signed-off-by: Dheeraj Kumar Srivastava <dheerajkumar.srivastava@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Vasant Hegde <vasant.hegde@amd.com>
Cc: Bharata B Rao <bharata@amd.com>
---

 mm/hugetlb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/hugetlb.c~mm-hugetlb-use-kvmalloc_objs-for-hugetlb_fault_mutex_table
+++ a/mm/hugetlb.c
@@ -4242,7 +4242,7 @@ static int __init hugetlb_init(void)
 	num_fault_mutexes = 1;
 #endif
 	hugetlb_fault_mutex_table =
-		kmalloc_objs(struct mutex, num_fault_mutexes);
+		kvmalloc_objs(struct mutex, num_fault_mutexes);
 	BUG_ON(!hugetlb_fault_mutex_table);
 
 	for (i = 0; i < num_fault_mutexes; i++)
_

Patches currently in -mm which might be from dheerajkumar.srivastava@amd.com are

mm-hugetlb-use-kvmalloc_objs-for-hugetlb_fault_mutex_table.patch