+ mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages.patch added to mm-new branch

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

The patch titled
     Subject: mm/memory-failure: support disabling soft offline for HugeTLB pages
has been added to the -mm mm-new branch.  Its filename is
     mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
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fixup patches in mm-new.

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------------------------------------------------------
From: Kyle Meyer <kyle.meyer@hpe.com>
Subject: mm/memory-failure: support disabling soft offline for HugeTLB pages
Date: Mon, 15 Sep 2025 19:27:41 -0500

Soft offlining a HugeTLB page reduces the HugeTLB page pool.

Commit 56374430c5dfc ("mm/memory-failure: userspace controls
soft-offlining pages") introduced the following sysctl interface to
control soft offline:

/proc/sys/vm/enable_soft_offline

The interface does not distinguish between page types:

    0 - Soft offline is disabled
    1 - Soft offline is enabled

Convert enable_soft_offline to a bitmask and support disabling soft
offline for HugeTLB pages:

Bits:

    0 - Enable soft offline
    1 - Disable soft offline for HugeTLB pages

Supported values:

    0 - Soft offline is disabled
    1 - Soft offline is enabled
    3 - Soft offline is enabled (disabled for HugeTLB pages)

Existing behavior is preserved.

Update documentation and HugeTLB soft offline self tests.

Link: https://lkml.kernel.org/r/aMiu_Uku6Y5ZbuhM@hpe.com
Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
Reported-by: Shawn Fan <shawn.fan@intel.com>
Suggested-by: Tony Luck <tony.luck@intel.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Clapinski <mclapinski@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Russ Anderson <russ.anderson@hpe.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yafang <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/ABI/testing/sysfs-memory-page-offline |    3 +
 Documentation/admin-guide/sysctl/vm.rst             |   28 ++++++++--
 mm/memory-failure.c                                 |   17 +++++-
 tools/testing/selftests/mm/hugetlb-soft-offline.c   |   19 +++++-
 4 files changed, 56 insertions(+), 11 deletions(-)

--- a/Documentation/ABI/testing/sysfs-memory-page-offline~mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages
+++ a/Documentation/ABI/testing/sysfs-memory-page-offline
@@ -20,6 +20,9 @@ Description:
 		number, or a error when the offlining failed.  Reading
 		the file is not allowed.
 
+		Soft-offline can be controlled via sysctl, see:
+		Documentation/admin-guide/sysctl/vm.rst
+
 What:		/sys/devices/system/memory/hard_offline_page
 Date:		Sep 2009
 KernelVersion:	2.6.33
--- a/Documentation/admin-guide/sysctl/vm.rst~mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages
+++ a/Documentation/admin-guide/sysctl/vm.rst
@@ -309,19 +309,39 @@ physical memory) vs performance / capaci
 HugeTLB cases.
 
 For all architectures, enable_soft_offline controls whether to soft offline
-memory pages.  When set to 1, kernel attempts to soft offline the pages
-whenever it thinks needed.  When set to 0, kernel returns EOPNOTSUPP to
-the request to soft offline the pages.  Its default value is 1.
+memory pages.
+
+enable_soft_offline is a bitmask:
+
+Bits::
+
+	0 - Enable soft offline
+	1 - Disable soft offline for HugeTLB pages
+
+Supported values::
+
+	0 - Soft offline is disabled
+	1 - Soft offline is enabled
+	3 - Soft offline is enabled (disabled for HugeTLB pages)
+
+The default value is 1.
+
+If soft offline is disabled for the requested page type, EOPNOTSUPP is returned.
 
 It is worth mentioning that after setting enable_soft_offline to 0, the
 following requests to soft offline pages will not be performed:
 
+- Request to soft offline from sysfs (soft_offline_page).
+
 - Request to soft offline pages from RAS Correctable Errors Collector.
 
-- On ARM, the request to soft offline pages from GHES driver.
+- On ARM and X86, the request to soft offline pages from GHES driver.
 
 - On PARISC, the request to soft offline pages from Page Deallocation Table.
 
+Note:
+	Soft offlining a HugeTLB page reduces the HugeTLB page pool.
+
 extfrag_threshold
 =================
 
--- a/mm/memory-failure.c~mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages
+++ a/mm/memory-failure.c
@@ -64,11 +64,14 @@
 #include "internal.h"
 #include "ras/ras_event.h"
 
+#define SOFT_OFFLINE_ENABLED		BIT(0)
+#define SOFT_OFFLINE_SKIP_HUGETLB	BIT(1)
+
 static int sysctl_memory_failure_early_kill __read_mostly;
 
 static int sysctl_memory_failure_recovery __read_mostly = 1;
 
-static int sysctl_enable_soft_offline __read_mostly = 1;
+static int sysctl_enable_soft_offline __read_mostly = SOFT_OFFLINE_ENABLED;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
@@ -150,7 +153,7 @@ static const struct ctl_table memory_fai
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
+		.extra2		= SYSCTL_THREE,
 	}
 };
 
@@ -2725,12 +2728,20 @@ int soft_offline_page(unsigned long pfn,
 		return -EIO;
 	}
 
-	if (!sysctl_enable_soft_offline) {
+	if (!(sysctl_enable_soft_offline & SOFT_OFFLINE_ENABLED)) {
 		pr_info_once("disabled by /proc/sys/vm/enable_soft_offline\n");
 		put_ref_page(pfn, flags);
 		return -EOPNOTSUPP;
 	}
 
+	if (sysctl_enable_soft_offline & SOFT_OFFLINE_SKIP_HUGETLB) {
+		if (folio_test_hugetlb(pfn_folio(pfn))) {
+			pr_info_once("disabled for HugeTLB pages by /proc/sys/vm/enable_soft_offline\n");
+			put_ref_page(pfn, flags);
+			return -EOPNOTSUPP;
+		}
+	}
+
 	mutex_lock(&mf_mutex);
 
 	if (PageHWPoison(page)) {
--- a/tools/testing/selftests/mm/hugetlb-soft-offline.c~mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages
+++ a/tools/testing/selftests/mm/hugetlb-soft-offline.c
@@ -5,6 +5,8 @@
  *   offlining failed with EOPNOTSUPP.
  * - if enable_soft_offline = 1, a hugepage should be dissolved and
  *   nr_hugepages/free_hugepages should be reduced by 1.
+ * - if enable_soft_offline = 3, hugepages should stay intact and soft
+ *   offlining failed with EOPNOTSUPP.
  *
  * Before running, make sure more than 2 hugepages of default_hugepagesz
  * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB:
@@ -32,6 +34,9 @@
 
 #define EPREFIX " !!! "
 
+#define SOFT_OFFLINE_ENABLED		(1 << 0)
+#define SOFT_OFFLINE_SKIP_HUGETLB	(1 << 1)
+
 static int do_soft_offline(int fd, size_t len, int expect_errno)
 {
 	char *filemap = NULL;
@@ -56,6 +61,7 @@ static int do_soft_offline(int fd, size_
 	ksft_print_msg("Allocated %#lx bytes of hugetlb pages\n", len);
 
 	hwp_addr = filemap + len / 2;
+	errno = 0;
 	ret = madvise(hwp_addr, pagesize, MADV_SOFT_OFFLINE);
 	ksft_print_msg("MADV_SOFT_OFFLINE %p ret=%d, errno=%d\n",
 		       hwp_addr, ret, errno);
@@ -83,7 +89,7 @@ static int set_enable_soft_offline(int v
 	char cmd[256] = {0};
 	FILE *cmdfile = NULL;
 
-	if (value != 0 && value != 1)
+	if (value < 0 || value > 3)
 		return -EINVAL;
 
 	sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);
@@ -155,13 +161,17 @@ close:
 static void test_soft_offline_common(int enable_soft_offline)
 {
 	int fd;
-	int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP;
+	int expect_errno = 0;
 	struct statfs file_stat;
 	unsigned long hugepagesize_kb = 0;
 	unsigned long nr_hugepages_before = 0;
 	unsigned long nr_hugepages_after = 0;
 	int ret;
 
+	if (!(enable_soft_offline & SOFT_OFFLINE_ENABLED) ||
+	     (enable_soft_offline & SOFT_OFFLINE_SKIP_HUGETLB))
+		expect_errno = EOPNOTSUPP;
+
 	ksft_print_msg("Test soft-offline when enabled_soft_offline=%d\n",
 		       enable_soft_offline);
 
@@ -198,7 +208,7 @@ static void test_soft_offline_common(int
 	// No need for the hugetlbfs file from now on.
 	close(fd);
 
-	if (enable_soft_offline) {
+	if (expect_errno == 0) {
 		if (nr_hugepages_before != nr_hugepages_after + 1) {
 			ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n");
 			return;
@@ -219,8 +229,9 @@ static void test_soft_offline_common(int
 int main(int argc, char **argv)
 {
 	ksft_print_header();
-	ksft_set_plan(2);
+	ksft_set_plan(3);
 
+	test_soft_offline_common(3);
 	test_soft_offline_common(1);
 	test_soft_offline_common(0);
 
_

Patches currently in -mm which might be from kyle.meyer@hpe.com are

mm-memory-failure-support-disabling-soft-offline-for-hugetlb-pages.patch