mm/memory-failure: Disable soft offline for HugeTLB pages by default

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Reported-by Shawn Fan <[email protected]>

Suggested-by Tony Luck <[email protected]>

Signed-off-by Kyle Meyer <[email protected]>

---

Tony's original patch disabled soft offline for HugeTLB pages when a correctable memory error reported via GHES (with "error threshold exceeded" set) happened to be on a HugeTLB page:

https://lore.kernel.org/all/[email protected]

This patch disables soft offline for HugeTLB pages by default (not just from GHES).

---
 .../ABI/testing/sysfs-memory-page-offline     |  6 ++++
 Documentation/admin-guide/sysctl/vm.rst       | 18 ++++++++---
 mm/memory-failure.c                           | 21 ++++++++++--
 .../selftests/mm/hugetlb-soft-offline.c       | 32 +++++++++++++------
 4 files changed, 60 insertions(+), 17 deletions(-)

Documentation/ABI/testing/sysfs-memory-page-offline +6 -0

index 00f4e35f916f..befb89ae39ec 100644
@@ -20,6 +20,12 @@ Description:
                number, or a error when the offlining failed.  Reading
                the file is not allowed.
 
+               Soft-offline can be disabled/enabled via sysctl:
+               /proc/sys/vm/enable_soft_offline
+
+               For details, see:
+               Documentation/admin-guide/sysctl/vm.rst
+
 What:          /sys/devices/system/memory/hard_offline_page
 Date:          Sep 2009
 KernelVersion: 2.6.33

Documentation/admin-guide/sysctl/vm.rst +0 -0

index 4d71211fdad8..ae56372bd604 100644
@@ -309,19 +309,29 @@ physical memory) vs performance / capacity implications in transparent and
 HugeTLB cases.

Documentation/admin-guide/sysctl/vm.rst +9 -1

+
+The default 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
 =================
 

mm/memory-failure.c +18 -3

index fc30ca4804bf..cb59a99b48c5 100644
@@ -64,11 +64,18 @@
 #include "internal.h"
 #include "ras/ras_event.h"
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 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_SKIP_HUGETLB;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 

@@ -150,7 +157,7 @@ static const struct ctl_table memory_failure_table[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
-               .extra2         = SYSCTL_ONE,
+               .extra2         = SYSCTL_TWO,
        }
 };
 

@@ -2799,12 +2806,20 @@ int soft_offline_page(unsigned long pfn, int flags)
                return -EIO;
        }
 
-       if (!sysctl_enable_soft_offline) {
+       if (sysctl_enable_soft_offline == SOFT_OFFLINE_DISABLED) {
                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_ENABLED_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)) {

tools/testing/selftests/mm/hugetlb-soft-offline.c +18 -7

index f086f0e04756..7e2873cd0a6d 100644
@@ -1,10 +1,15 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test soft offline behavior for HugeTLB pages:
- * - if enable_soft_offline = 0, hugepages should stay intact and soft
- *   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 = 0 (SOFT_OFFLINE_DISABLED), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 1 (SOFT_OFFLINE_ENABLED_SKIP_HUGETLB), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 2 (SOFT_OFFLINE_ENABLED), a HugeTLB page should be
+ *   dissolved and nr_hugepages/free_hugepages should be reduced by 1.
  *
  * Before running, make sure more than 2 hugepages of default_hugepagesz
  * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB:

@@ -32,6 +37,12 @@
 
 #define EPREFIX " !!! "
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 static int do_soft_offline(int fd, size_t len, int expect_errno)
 {
        char *filemap = NULL;

@@ -83,7 +94,7 @@ static int set_enable_soft_offline(int value)
        char cmd[256] = {0};
        FILE *cmdfile = NULL;
 
-       if (value != 0 && value != 1)
+       if (value < SOFT_OFFLINE_DISABLED || value > SOFT_OFFLINE_ENABLED)
                return -EINVAL;
 
        sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);

@@ -155,7 +166,7 @@ static int create_hugetlbfs_file(struct statfs *file_stat)
 static void test_soft_offline_common(int enable_soft_offline)
 {
        int fd;
-       int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP;
+       int expect_errno = (enable_soft_offline == SOFT_OFFLINE_ENABLED) ? 0 : EOPNOTSUPP;
        struct statfs file_stat;
        unsigned long hugepagesize_kb = 0;
        unsigned long nr_hugepages_before = 0;

@@ -198,7 +209,7 @@ static void test_soft_offline_common(int enable_soft_offline)
        // No need for the hugetlbfs file from now on.
        close(fd);
 
-       if (enable_soft_offline) {
+       if (enable_soft_offline == SOFT_OFFLINE_ENABLED) {
                if (nr_hugepages_before != nr_hugepages_after + 1) {
                        ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n");
                        return;

@@ -219,10 +230,11 @@ static void test_soft_offline_common(int enable_soft_offline)
 int main(int argc, char **argv)

tools/testing/selftests/mm/hugetlb-soft-offline.c +0 -1

        ksft_finished();
 }
--

2.51.0

Quoted 69 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Reported-by Shawn Fan <[email protected]>

Suggested-by Tony Luck <[email protected]>

Signed-off-by Kyle Meyer <[email protected]>

---

Tony's original patch disabled soft offline for HugeTLB pages when a correctable memory error reported via GHES (with "error threshold exceeded" set) happened to be on a HugeTLB page:

https://lore.kernel.org/all/[email protected]

This patch disables soft offline for HugeTLB pages by default (not just from GHES).

---
 .../ABI/testing/sysfs-memory-page-offline     |  6 ++++
 Documentation/admin-guide/sysctl/vm.rst       | 18 ++++++++---
 mm/memory-failure.c                           | 21 ++++++++++--
 .../selftests/mm/hugetlb-soft-offline.c       | 32 +++++++++++++------
 4 files changed, 60 insertions(+), 17 deletions(-)

Documentation/ABI/testing/sysfs-memory-page-offline +6 -0

index 00f4e35f916f..befb89ae39ec 100644
@@ -20,6 +20,12 @@ Description:
                number, or a error when the offlining failed.  Reading
                the file is not allowed.
 
+               Soft-offline can be disabled/enabled via sysctl:
+               /proc/sys/vm/enable_soft_offline
+
+               For details, see:
+               Documentation/admin-guide/sysctl/vm.rst
+
 What:          /sys/devices/system/memory/hard_offline_page
 Date:          Sep 2009
 KernelVersion: 2.6.33

Documentation/admin-guide/sysctl/vm.rst +0 -0

index 4d71211fdad8..ae56372bd604 100644
@@ -309,19 +309,29 @@ physical memory) vs performance / capacity implications in transparent and
 HugeTLB cases.

Documentation/admin-guide/sysctl/vm.rst physical memory) vs performance / capacity implications in transparent and · line 316

Quoted 10 lines

Documentation/admin-guide/sysctl/vm.rst +5 -3

 
 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:
+
+- 0: Soft offline is disabled.
+- 1: Soft offline is enabled (excluding HugeTLB pages).
+- 2: Soft offline is enabled (including HugeTLB pages).

Would it be better to keep/inherit the previous documented behavior "1
- Soft offline is enabled (no matter what type of the page is)"? Thus it will have no impact to users that are very nervous about corrected memory errors and willing to lose hugetlb page. Something like:

  enum soft_offline {
      SOFT_OFFLINE_DISABLED = 0,
      SOFT_OFFLINE_ENABLED,
      SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
      // SOFT_OFFLINE_ENABLED_SKIP_XXX...
  };

Quoted 143 lines

Documentation/admin-guide/sysctl/vm.rst +9 -1

+
+The default 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
 =================
 

mm/memory-failure.c +18 -3

index fc30ca4804bf..cb59a99b48c5 100644
@@ -64,11 +64,18 @@
 #include "internal.h"
 #include "ras/ras_event.h"
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 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_SKIP_HUGETLB;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 

@@ -150,7 +157,7 @@ static const struct ctl_table memory_failure_table[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
-               .extra2         = SYSCTL_ONE,
+               .extra2         = SYSCTL_TWO,
        }
 };
 

@@ -2799,12 +2806,20 @@ int soft_offline_page(unsigned long pfn, int flags)
                return -EIO;
        }
 
-       if (!sysctl_enable_soft_offline) {
+       if (sysctl_enable_soft_offline == SOFT_OFFLINE_DISABLED) {
                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_ENABLED_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)) {

tools/testing/selftests/mm/hugetlb-soft-offline.c +18 -7

index f086f0e04756..7e2873cd0a6d 100644
@@ -1,10 +1,15 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test soft offline behavior for HugeTLB pages:
- * - if enable_soft_offline = 0, hugepages should stay intact and soft
- *   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 = 0 (SOFT_OFFLINE_DISABLED), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 1 (SOFT_OFFLINE_ENABLED_SKIP_HUGETLB), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 2 (SOFT_OFFLINE_ENABLED), a HugeTLB page should be
+ *   dissolved and nr_hugepages/free_hugepages should be reduced by 1.
  *
  * Before running, make sure more than 2 hugepages of default_hugepagesz
  * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB:

@@ -32,6 +37,12 @@
 
 #define EPREFIX " !!! "
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 static int do_soft_offline(int fd, size_t len, int expect_errno)
 {
        char *filemap = NULL;

@@ -83,7 +94,7 @@ static int set_enable_soft_offline(int value)
        char cmd[256] = {0};
        FILE *cmdfile = NULL;
 
-       if (value != 0 && value != 1)
+       if (value < SOFT_OFFLINE_DISABLED || value > SOFT_OFFLINE_ENABLED)
                return -EINVAL;
 
        sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);

@@ -155,7 +166,7 @@ static int create_hugetlbfs_file(struct statfs *file_stat)
 static void test_soft_offline_common(int enable_soft_offline)
 {
        int fd;
-       int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP;
+       int expect_errno = (enable_soft_offline == SOFT_OFFLINE_ENABLED) ? 0 : EOPNOTSUPP;
        struct statfs file_stat;
        unsigned long hugepagesize_kb = 0;
        unsigned long nr_hugepages_before = 0;

@@ -198,7 +209,7 @@ static void test_soft_offline_common(int enable_soft_offline)
        // No need for the hugetlbfs file from now on.
        close(fd);
 
-       if (enable_soft_offline) {
+       if (enable_soft_offline == SOFT_OFFLINE_ENABLED) {
                if (nr_hugepages_before != nr_hugepages_after + 1) {
                        ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n");
                        return;

@@ -219,10 +230,11 @@ static void test_soft_offline_common(int enable_soft_offline)
 int main(int argc, char **argv)

tools/testing/selftests/mm/hugetlb-soft-offline.c static void test_soft_offline_common(int enable_soft_offline) · line 237

Quoted 10 lines

tools/testing/selftests/mm/hugetlb-soft-offline.c +4 -3

 {
        ksft_print_header();
-       ksft_set_plan(2);
+       ksft_set_plan(3);
 
-       test_soft_offline_common(1);
-       test_soft_offline_common(0);
+       test_soft_offline_common(SOFT_OFFLINE_ENABLED);
+       test_soft_offline_common(SOFT_OFFLINE_ENABLED_SKIP_HUGETLB);
+       test_soft_offline_common(SOFT_OFFLINE_DISABLED);

Thanks for updating the test code! Looks good to me.

Quoted 6 lines

tools/testing/selftests/mm/hugetlb-soft-offline.c +0 -1

        ksft_finished();
 }
--

2.51.0

Quoted 86 lines · Jiaqi Yan

Quoted 69 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Reported-by Shawn Fan <[email protected]>

Suggested-by Tony Luck <[email protected]>

Signed-off-by Kyle Meyer <[email protected]>

---

Tony's original patch disabled soft offline for HugeTLB pages when a correctable memory error reported via GHES (with "error threshold exceeded" set) happened to be on a HugeTLB page:

https://lore.kernel.org/all/[email protected]

This patch disables soft offline for HugeTLB pages by default (not just from GHES).

---
 .../ABI/testing/sysfs-memory-page-offline     |  6 ++++
 Documentation/admin-guide/sysctl/vm.rst       | 18 ++++++++---
 mm/memory-failure.c                           | 21 ++++++++++--
 .../selftests/mm/hugetlb-soft-offline.c       | 32 +++++++++++++------
 4 files changed, 60 insertions(+), 17 deletions(-)

Documentation/ABI/testing/sysfs-memory-page-offline +6 -0

index 00f4e35f916f..befb89ae39ec 100644
@@ -20,6 +20,12 @@ Description:
                number, or a error when the offlining failed.  Reading
                the file is not allowed.
 
+               Soft-offline can be disabled/enabled via sysctl:
+               /proc/sys/vm/enable_soft_offline
+
+               For details, see:
+               Documentation/admin-guide/sysctl/vm.rst
+
 What:          /sys/devices/system/memory/hard_offline_page
 Date:          Sep 2009
 KernelVersion: 2.6.33

Documentation/admin-guide/sysctl/vm.rst +0 -0

index 4d71211fdad8..ae56372bd604 100644
@@ -309,19 +309,29 @@ physical memory) vs performance / capacity implications in transparent and
 HugeTLB cases.

Documentation/admin-guide/sysctl/vm.rst physical memory) vs performance / capacity implications in transparent and · line 316

Quoted 10 lines

Documentation/admin-guide/sysctl/vm.rst +5 -3

 
 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:
+
+- 0: Soft offline is disabled.
+- 1: Soft offline is enabled (excluding HugeTLB pages).
+- 2: Soft offline is enabled (including HugeTLB pages).

Would it be better to keep/inherit the previous documented behavior "1
- Soft offline is enabled (no matter what type of the page is)"? Thus it will have no impact to users that are very nervous about corrected memory errors and willing to lose hugetlb page. Something like:

Quoted 6 lines

  enum soft_offline {
      SOFT_OFFLINE_DISABLED = 0,
      SOFT_OFFLINE_ENABLED,
      SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
      // SOFT_OFFLINE_ENABLED_SKIP_XXX...
  };

I don't have a strong opinion on the default because there's a sysctl interface, but that seems reasonable. I'll wait for more feedback before putting together a v2.

Quoted 163 lines

Quoted 144 lines

Documentation/admin-guide/sysctl/vm.rst +9 -1

+
+The default 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
 =================
 

mm/memory-failure.c +18 -3

index fc30ca4804bf..cb59a99b48c5 100644
@@ -64,11 +64,18 @@
 #include "internal.h"
 #include "ras/ras_event.h"
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 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_SKIP_HUGETLB;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 

@@ -150,7 +157,7 @@ static const struct ctl_table memory_failure_table[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec_minmax,
                .extra1         = SYSCTL_ZERO,
-               .extra2         = SYSCTL_ONE,
+               .extra2         = SYSCTL_TWO,
        }
 };
 

@@ -2799,12 +2806,20 @@ int soft_offline_page(unsigned long pfn, int flags)
                return -EIO;
        }
 
-       if (!sysctl_enable_soft_offline) {
+       if (sysctl_enable_soft_offline == SOFT_OFFLINE_DISABLED) {
                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_ENABLED_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)) {

tools/testing/selftests/mm/hugetlb-soft-offline.c +18 -7

index f086f0e04756..7e2873cd0a6d 100644
@@ -1,10 +1,15 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
  * Test soft offline behavior for HugeTLB pages:
- * - if enable_soft_offline = 0, hugepages should stay intact and soft
- *   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 = 0 (SOFT_OFFLINE_DISABLED), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 1 (SOFT_OFFLINE_ENABLED_SKIP_HUGETLB), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 2 (SOFT_OFFLINE_ENABLED), a HugeTLB page should be
+ *   dissolved and nr_hugepages/free_hugepages should be reduced by 1.
  *
  * Before running, make sure more than 2 hugepages of default_hugepagesz
  * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB:

@@ -32,6 +37,12 @@
 
 #define EPREFIX " !!! "
 
+enum soft_offline {
+       SOFT_OFFLINE_DISABLED = 0,
+       SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+       SOFT_OFFLINE_ENABLED
+};
+
 static int do_soft_offline(int fd, size_t len, int expect_errno)
 {
        char *filemap = NULL;

@@ -83,7 +94,7 @@ static int set_enable_soft_offline(int value)
        char cmd[256] = {0};
        FILE *cmdfile = NULL;
 
-       if (value != 0 && value != 1)
+       if (value < SOFT_OFFLINE_DISABLED || value > SOFT_OFFLINE_ENABLED)
                return -EINVAL;
 
        sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);

@@ -155,7 +166,7 @@ static int create_hugetlbfs_file(struct statfs *file_stat)
 static void test_soft_offline_common(int enable_soft_offline)
 {
        int fd;
-       int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP;
+       int expect_errno = (enable_soft_offline == SOFT_OFFLINE_ENABLED) ? 0 : EOPNOTSUPP;
        struct statfs file_stat;
        unsigned long hugepagesize_kb = 0;
        unsigned long nr_hugepages_before = 0;

@@ -198,7 +209,7 @@ static void test_soft_offline_common(int enable_soft_offline)
        // No need for the hugetlbfs file from now on.
        close(fd);
 
-       if (enable_soft_offline) {
+       if (enable_soft_offline == SOFT_OFFLINE_ENABLED) {
                if (nr_hugepages_before != nr_hugepages_after + 1) {
                        ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n");
                        return;

@@ -219,10 +230,11 @@ static void test_soft_offline_common(int enable_soft_offline)
 int main(int argc, char **argv)

tools/testing/selftests/mm/hugetlb-soft-offline.c static void test_soft_offline_common(int enable_soft_offline) · line 237

Quoted 10 lines

tools/testing/selftests/mm/hugetlb-soft-offline.c +4 -3

 {
        ksft_print_header();
-       ksft_set_plan(2);
+       ksft_set_plan(3);
 
-       test_soft_offline_common(1);
-       test_soft_offline_common(0);
+       test_soft_offline_common(SOFT_OFFLINE_ENABLED);
+       test_soft_offline_common(SOFT_OFFLINE_ENABLED_SKIP_HUGETLB);
+       test_soft_offline_common(SOFT_OFFLINE_DISABLED);

Thanks for updating the test code! Looks good to me.

Quoted 6 lines

tools/testing/selftests/mm/hugetlb-soft-offline.c +0 -1

        ksft_finished();
 }
--

2.51.0

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Reported-by Shawn Fan <[email protected]>

Suggested-by Tony Luck <[email protected]>

Signed-off-by Kyle Meyer <[email protected]>

---

Tony's original patch disabled soft offline for HugeTLB pages when a correctable memory error reported via GHES (with "error threshold exceeded" set) happened to be on a HugeTLB page:

https://lore.kernel.org/all/[email protected]

This patch disables soft offline for HugeTLB pages by default (not just from GHES).

---
  .../ABI/testing/sysfs-memory-page-offline     |  6 ++++
  Documentation/admin-guide/sysctl/vm.rst       | 18 ++++++++---
  mm/memory-failure.c                           | 21 ++++++++++--
  .../selftests/mm/hugetlb-soft-offline.c       | 32 +++++++++++++------
  4 files changed, 60 insertions(+), 17 deletions(-)

Documentation/ABI/testing/sysfs-memory-page-offline +6 -0

index 00f4e35f916f..befb89ae39ec 100644
@@ -20,6 +20,12 @@ Description:
  		number, or a error when the offlining failed.  Reading
  		the file is not allowed.
 
+		Soft-offline can be disabled/enabled via sysctl:
+		/proc/sys/vm/enable_soft_offline
+
+		For details, see:
+		Documentation/admin-guide/sysctl/vm.rst
+
  What:		/sys/devices/system/memory/hard_offline_page
  Date:		Sep 2009
  KernelVersion:	2.6.33

Documentation/admin-guide/sysctl/vm.rst +14 -4

index 4d71211fdad8..ae56372bd604 100644
@@ -309,19 +309,29 @@ physical memory) vs performance / capacity implications in transparent and
  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:
+
+- 0: Soft offline is disabled.
+- 1: Soft offline is enabled (excluding HugeTLB pages).
+- 2: Soft offline is enabled (including HugeTLB pages).
+
+The default 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
  =================
 

mm/memory-failure.c +18 -3

index fc30ca4804bf..cb59a99b48c5 100644
@@ -64,11 +64,18 @@
  #include "internal.h"
  #include "ras/ras_event.h"
 
+enum soft_offline {
+	SOFT_OFFLINE_DISABLED = 0,
+	SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+	SOFT_OFFLINE_ENABLED
+};
+
  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_SKIP_HUGETLB;
 
  atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 

@@ -150,7 +157,7 @@ static const struct ctl_table memory_failure_table[] = {
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= SYSCTL_ZERO,
-		.extra2		= SYSCTL_ONE,
+		.extra2		= SYSCTL_TWO,
  	}
  };
 

@@ -2799,12 +2806,20 @@ int soft_offline_page(unsigned long pfn, int flags)
  		return -EIO;
  	}
 
-	if (!sysctl_enable_soft_offline) {
+	if (sysctl_enable_soft_offline == SOFT_OFFLINE_DISABLED) {
  		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_ENABLED_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)) {

tools/testing/selftests/mm/hugetlb-soft-offline.c +18 -8

index f086f0e04756..7e2873cd0a6d 100644
@@ -1,10 +1,15 @@
  // SPDX-License-Identifier: GPL-2.0
  /*
   * Test soft offline behavior for HugeTLB pages:
- * - if enable_soft_offline = 0, hugepages should stay intact and soft
- *   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 = 0 (SOFT_OFFLINE_DISABLED), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 1 (SOFT_OFFLINE_ENABLED_SKIP_HUGETLB), HugeTLB pages
+ *   should stay intact and soft offlining failed with EOPNOTSUPP.
+ *
+ * - if enable_soft_offline = 2 (SOFT_OFFLINE_ENABLED), a HugeTLB page should be
+ *   dissolved and nr_hugepages/free_hugepages should be reduced by 1.
   *
   * Before running, make sure more than 2 hugepages of default_hugepagesz
   * are allocated. For example, if /proc/meminfo/Hugepagesize is 2048kB:

@@ -32,6 +37,12 @@
 
  #define EPREFIX " !!! "
 
+enum soft_offline {
+	SOFT_OFFLINE_DISABLED = 0,
+	SOFT_OFFLINE_ENABLED_SKIP_HUGETLB,
+	SOFT_OFFLINE_ENABLED
+};
+
  static int do_soft_offline(int fd, size_t len, int expect_errno)
  {
  	char *filemap = NULL;

@@ -83,7 +94,7 @@ static int set_enable_soft_offline(int value)
  	char cmd[256] = {0};
  	FILE *cmdfile = NULL;
 
-	if (value != 0 && value != 1)
+	if (value < SOFT_OFFLINE_DISABLED || value > SOFT_OFFLINE_ENABLED)
  		return -EINVAL;
 
  	sprintf(cmd, "echo %d > /proc/sys/vm/enable_soft_offline", value);

@@ -155,7 +166,7 @@ static int create_hugetlbfs_file(struct statfs *file_stat)
  static void test_soft_offline_common(int enable_soft_offline)
  {
  	int fd;
-	int expect_errno = enable_soft_offline ? 0 : EOPNOTSUPP;
+	int expect_errno = (enable_soft_offline == SOFT_OFFLINE_ENABLED) ? 0 : EOPNOTSUPP;
  	struct statfs file_stat;
  	unsigned long hugepagesize_kb = 0;
  	unsigned long nr_hugepages_before = 0;

@@ -198,7 +209,7 @@ static void test_soft_offline_common(int enable_soft_offline)
  	// No need for the hugetlbfs file from now on.
  	close(fd);
 
-	if (enable_soft_offline) {
+	if (enable_soft_offline == SOFT_OFFLINE_ENABLED) {
  		if (nr_hugepages_before != nr_hugepages_after + 1) {
  			ksft_test_result_fail("MADV_SOFT_OFFLINE should reduced 1 hugepage\n");
  			return;

@@ -219,10 +230,11 @@ static void test_soft_offline_common(int enable_soft_offline)
  int main(int argc, char **argv)
  {
  	ksft_print_header();
-	ksft_set_plan(2);

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Quoted 20 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Quoted 3 lines

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

I'm sure you spotted that the documentation for "/sys/devices/system/memory/soft_offline_pag" resides under "testing".

If your read about MADV_SOFT_OFFLINE in the man page it clearly says:

"This feature is intended for testing of memory error-handling code; it is available only if the kernel was configured with CONFIG_MEMORY_FAILURE."

So I'm sorry to say: I miss why we should add all this complexity to make a feature used for testing soft-offlining work differently for hugetlb folios -- with a testing interface.

Signature · 3 lines

Cheers

David / dhildenb

Quoted 21 lines · David Hildenbrand

Quoted 20 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Quoted 6 lines

Quoted 3 lines

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

I'm sure you spotted that the documentation for "/sys/devices/system/memory/soft_offline_pag" resides under "testing".

But that is only one of several places in the kernel that feed into the page offline code.

This patch was motivated by the GHES path where BIOS indicates a corrected error threshold was exceeded. There's also the drivers/ras/cec.c path where Linux does it's own threshold counting.

Quoted 1 line

Quoted 4 lines

If your read about MADV_SOFT_OFFLINE in the man page it clearly says:

"This feature is intended for testing of memory error-handling code; it is available only if the kernel was configured with CONFIG_MEMORY_FAILURE."

Agreed that this all depends on CONFIG_MEMORY_FAILURE ... so if any part of the flow is compiled in when that is "=n" then some changes are needed to fix that.

Quoted 4 lines

So I'm sorry to say: I miss why we should add all this complexity to make a feature used for testing soft-offlining work differently for hugetlb folios -- with a testing interface.

Quoted 25 lines · David Hildenbrand

Quoted 23 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Quoted 2 lines

I'm sure you spotted that the documentation for "/sys/devices/system/memory/soft_offline_pag" resides under "testing".

But that is only one of several places in the kernel that feed into the page offline code.

Quoted 26 lines · Tony

Quoted 25 lines · David Hildenbrand

Quoted 23 lines · Kyle Meyer

Soft offlining a HugeTLB page reduces the available HugeTLB page pool. Since HugeTLB pages are preallocated, reducing the available HugeTLB page pool can cause allocation failures.

/proc/sys/vm/enable_soft_offline provides a sysctl interface to disable/enable soft offline:

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

The current sysctl interface does not distinguish between HugeTLB pages and other page types.

Disable soft offline for HugeTLB pages by default (1) and extend the sysctl interface to preserve existing behavior (2):

0 - Soft offline is disabled.
1 - Soft offline is enabled (excluding HugeTLB pages). 2 - Soft offline is enabled (including HugeTLB pages).

Update documentation for the sysctl interface, reference the sysctl interface in the sysfs ABI documentation, and update HugeTLB soft offline selftests.

Quoted 5 lines

Quoted 2 lines

I'm sure you spotted that the documentation for "/sys/devices/system/memory/soft_offline_pag" resides under "testing".

But that is only one of several places in the kernel that feed into the page offline code.

Right, I can see one more call to soft_offline_page() from arch/parisc/kernel/pdt.c.

And there is memory_failure_work_func() that I missed.

So agreed that this goes beyond testing.

It caught my attention because you ended up modifying documentation residing in Documentation/ABI/testing/sysfs-memory-page-offline.

Reading 56374430c5dfc that Kyle pointed out is gets clearer.

So the patch motivation/idea makes sense to me.

I'll note two things:

(1) The interface design is not really extensible. Imagine if we want to exclude yet another page type.

Can we maybe add a second interface that defines a filter for types?

Alternatively, you could use all the remaining flags as such a filter.

0 - Soft offline is completely disabled.
1 - Soft offline is enabled except for manually disabled types.

Filter

2 - disable hugetlb.

So value 3 would give you "enable all except hugetlb" etc.

We could add in the future

4 - disable guest_memfd (just some random example)

Then you

2) Changing the semantics of the value "1"

IIUC, you are changing the semantics of value "1". It used to mean "SOFT_OFFLINE_ENABLED" now it is "SOFT_OFFLINE_ENABLED_SKIP_HUGETLB", which is a change in behavior.

If that is the case, I don't think that's okay.

2) I am not sure about changing the default. That should be an admin/ distro decision.