tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/folio_split_race_test.c | 292 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 2 + 3 files changed, 295 insertions(+) create mode 100644 tools/testing/selftests/mm/folio_split_race_test.c
The added folio_split_race_test is a modified C port of the race condition
test from [1]. The test creates shmem huge pages, where the main thread
punches holes in the shmem to cause folio_split() in the kernel and
a set of 16 threads reads the shmem to cause filemap_get_entry() in the
kernel. filemap_get_entry() reads the folio and xarray split by
folio_split() locklessly. The original test[2] is written in rust and uses
memfd (shmem backed). This C port uses shmem directly and use a single
process.
Note: the initial rust to C conversion is done by Cursor.
Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1]
Link: https://github.com/dfinity/thp-madv-remove-test [2]
Signed-off-by: Bas van Dijk <bas@dfinity.org>
Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@dfinity.org>
Signed-off-by: Zi Yan <ziy@nvidia.com>
---
From V2:
1. simplied the program by removing fork.
From V1:
1. added prctl(PR_SET_PDEATHSIG, SIGTERM) to avoid child looping
forever.
2. removed page_idx % PUNCH_INTERVAL >= 0, since it is a nop. Added a
comment.
3. added a child process status check to prevent parent looping forever
and record that as a failure.
4. used ksft_exit_skip() instead of ksft_finished() when the program is
not running as root.
5. restored THP settings properly when the program exits abnormally.
tools/testing/selftests/mm/Makefile | 1 +
.../selftests/mm/folio_split_race_test.c | 292 ++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 2 +
3 files changed, 295 insertions(+)
create mode 100644 tools/testing/selftests/mm/folio_split_race_test.c
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index 7a5de4e9bf520..cd24596cdd27e 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -105,6 +105,7 @@ TEST_GEN_FILES += droppable
TEST_GEN_FILES += guard-regions
TEST_GEN_FILES += merge
TEST_GEN_FILES += rmap
+TEST_GEN_FILES += folio_split_race_test
ifneq ($(ARCH),arm64)
TEST_GEN_FILES += soft-dirty
diff --git a/tools/testing/selftests/mm/folio_split_race_test.c b/tools/testing/selftests/mm/folio_split_race_test.c
new file mode 100644
index 0000000000000..efe4b631edfc4
--- /dev/null
+++ b/tools/testing/selftests/mm/folio_split_race_test.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * The test creates shmem PMD huge pages, fills all pages with known patterns,
+ * then continuously verifies non-punched pages with 16 threads. Meanwhile, the
+ * main thread punches holes via MADV_REMOVE on the shmem.
+ *
+ * It tests the race condition between folio_split() and filemap_get_entry(),
+ * where the hole punches on shmem lead to folio_split() and reading the shmem
+ * lead to filemap_get_entry().
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/mman.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <signal.h>
+#include <unistd.h>
+#include "vm_util.h"
+#include "kselftest.h"
+#include "thp_settings.h"
+
+uint64_t page_size;
+uint64_t pmd_pagesize;
+#define NR_PMD_PAGE 5
+#define FILE_SIZE (pmd_pagesize * NR_PMD_PAGE)
+#define TOTAL_PAGES (FILE_SIZE / page_size)
+
+/* Every N-th to N+M-th pages are punched; not aligned with huge page boundaries. */
+#define PUNCH_INTERVAL 50 /* N */
+#define PUNCH_SIZE_FACTOR 3 /* M */
+
+#define NUM_READER_THREADS 16
+#define FILL_BYTE 0xAF
+#define NUM_ITERATIONS 100
+
+/* Shared control block: control reading threads and record stats */
+struct shared_ctl {
+ atomic_uint_fast32_t stop;
+ atomic_size_t reader_failures;
+ atomic_size_t reader_verified;
+};
+
+static void fill_page(unsigned char *base, size_t page_idx)
+{
+ unsigned char *page_ptr = base + page_idx * page_size;
+ uint64_t idx = (uint64_t)page_idx;
+
+ memset(page_ptr, FILL_BYTE, page_size);
+ memcpy(page_ptr, &idx, sizeof(idx));
+}
+
+/* Returns true if valid, false if corrupted. */
+static bool check_page(unsigned char *base, size_t page_idx)
+{
+ unsigned char *page_ptr = base + page_idx * page_size;
+ uint64_t expected_idx = (uint64_t)page_idx;
+ uint64_t got_idx;
+
+ memcpy(&got_idx, page_ptr, 8);
+
+ if (got_idx != expected_idx) {
+ size_t off;
+ int all_zero = 1;
+
+ for (off = 0; off < page_size; off++) {
+ if (page_ptr[off] != 0) {
+ all_zero = 0;
+ break;
+ }
+ }
+ if (all_zero) {
+ ksft_print_msg(
+ "CORRUPTED: page %zu (huge page %zu) is ALL ZEROS\n",
+ page_idx,
+ (page_idx * page_size) / pmd_pagesize);
+ } else {
+ ksft_print_msg(
+ "CORRUPTED: page %zu (huge page %zu): expected idx %zu, got %lu\n",
+ page_idx, (page_idx * page_size) / pmd_pagesize,
+ page_idx, (unsigned long)got_idx);
+ }
+ return false;
+ }
+ return true;
+}
+
+struct reader_arg {
+ unsigned char *base;
+ struct shared_ctl *ctl;
+ int tid;
+ atomic_size_t *failures;
+ atomic_size_t *verified;
+};
+
+static void *reader_thread(void *arg)
+{
+ struct reader_arg *ra = (struct reader_arg *)arg;
+ unsigned char *base = ra->base;
+ struct shared_ctl *ctl = ra->ctl;
+ int tid = ra->tid;
+ atomic_size_t *failures = ra->failures;
+ atomic_size_t *verified = ra->verified;
+ size_t page_idx;
+
+ while (atomic_load_explicit(&ctl->stop, memory_order_acquire) == 0) {
+ for (page_idx = (size_t)tid; page_idx < TOTAL_PAGES;
+ page_idx += NUM_READER_THREADS) {
+ /*
+ * page_idx % PUNCH_INTERVAL is in [0, PUNCH_INTERVAL),
+ * skip [0, PUNCH_SIZE_FACTOR)
+ */
+ if (page_idx % PUNCH_INTERVAL < PUNCH_SIZE_FACTOR)
+ continue;
+ if (check_page(base, page_idx))
+ atomic_fetch_add_explicit(verified, 1,
+ memory_order_relaxed);
+ else
+ atomic_fetch_add_explicit(failures, 1,
+ memory_order_relaxed);
+ }
+ if (atomic_load_explicit(failures, memory_order_relaxed) > 0)
+ break;
+ }
+
+ return NULL;
+}
+
+static void create_readers(pthread_t *threads, struct reader_arg *args,
+ unsigned char *base, struct shared_ctl *ctl)
+{
+ int i;
+
+ for (i = 0; i < NUM_READER_THREADS; i++) {
+ args[i].base = base;
+ args[i].ctl = ctl;
+ args[i].tid = i;
+ args[i].failures = &ctl->reader_failures;
+ args[i].verified = &ctl->reader_verified;
+ if (pthread_create(&threads[i], NULL, reader_thread,
+ &args[i]) != 0)
+ ksft_exit_fail_msg("pthread_create failed\n");
+ }
+}
+
+/* Run a single iteration. Returns total number of corrupted pages. */
+static size_t run_iteration(void)
+{
+ size_t reader_failures, reader_verified;
+ struct reader_arg args[NUM_READER_THREADS];
+ pthread_t threads[NUM_READER_THREADS];
+ unsigned char *mmap_base;
+ struct shared_ctl ctl;
+ size_t i;
+
+ memset(&ctl, 0, sizeof(struct shared_ctl));
+
+ mmap_base = mmap(NULL, FILE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+
+ if (mmap_base == MAP_FAILED)
+ ksft_exit_fail_msg("mmap failed: %d\n", errno);
+
+ if (madvise(mmap_base, FILE_SIZE, MADV_HUGEPAGE) != 0)
+ ksft_exit_fail_msg("madvise(MADV_HUGEPAGE) failed: %d\n",
+ errno);
+
+ for (i = 0; i < TOTAL_PAGES; i++)
+ fill_page(mmap_base, i);
+
+ if (!check_huge_shmem(mmap_base, NR_PMD_PAGE, pmd_pagesize))
+ ksft_exit_fail_msg("No shmem THP is allocated\n");
+
+ create_readers(threads, args, mmap_base, &ctl);
+
+ for (i = 0; i < TOTAL_PAGES; i++) {
+ if (i % PUNCH_INTERVAL != 0)
+ continue;
+ if (madvise(mmap_base + i * page_size,
+ PUNCH_SIZE_FACTOR * page_size, MADV_REMOVE) != 0) {
+ ksft_exit_fail_msg(
+ "madvise(MADV_REMOVE) failed on page %zu: %d\n",
+ i, errno);
+ }
+
+ i += PUNCH_SIZE_FACTOR;
+ }
+
+ atomic_store_explicit(&ctl.stop, 1, memory_order_release);
+
+ for (i = 0; i < NUM_READER_THREADS; i++)
+ pthread_join(threads[i], NULL);
+
+ reader_failures = atomic_load_explicit(&ctl.reader_failures,
+ memory_order_acquire);
+ reader_verified = atomic_load_explicit(&ctl.reader_verified,
+ memory_order_acquire);
+ if (reader_failures)
+ ksft_print_msg("Child: %zu pages verified, %zu failures\n",
+ reader_verified, reader_failures);
+
+ munmap(mmap_base, FILE_SIZE);
+
+ return reader_failures;
+}
+
+static void thp_cleanup_handler(int signum)
+{
+ thp_restore_settings();
+ /*
+ * Restore default handler and re-raise the signal to exit.
+ * This is to ensure the test process exits with the correct
+ * status code corresponding to the signal.
+ */
+ signal(signum, SIG_DFL);
+ raise(signum);
+}
+
+static void thp_settings_cleanup(void)
+{
+ thp_restore_settings();
+}
+
+int main(void)
+{
+ struct thp_settings current_settings;
+ bool failed = false;
+ size_t failures;
+ size_t iter;
+
+ ksft_print_header();
+
+ if (!thp_is_enabled())
+ ksft_exit_skip("Transparent Hugepages not available\n");
+
+ if (geteuid() != 0)
+ ksft_exit_skip("Please run the test as root\n");
+
+ thp_save_settings();
+ /* make sure thp settings are restored */
+ if (atexit(thp_settings_cleanup) != 0)
+ ksft_exit_fail_msg("atexit failed\n");
+
+ signal(SIGINT, thp_cleanup_handler);
+ signal(SIGTERM, thp_cleanup_handler);
+
+ thp_read_settings(¤t_settings);
+ current_settings.shmem_enabled = SHMEM_ADVISE;
+ thp_write_settings(¤t_settings);
+
+ ksft_set_plan(1);
+
+ page_size = getpagesize();
+ pmd_pagesize = read_pmd_pagesize();
+
+ ksft_print_msg("folio split race test\n");
+ ksft_print_msg("===================================================\n");
+ ksft_print_msg("Shmem size: %zu MiB\n", FILE_SIZE / 1024 / 1024);
+ ksft_print_msg("Total pages: %zu\n", TOTAL_PAGES);
+ ksft_print_msg("Child readers: %d\n", NUM_READER_THREADS);
+ ksft_print_msg("Punching every %dth to %dth page\n", PUNCH_INTERVAL,
+ PUNCH_INTERVAL + PUNCH_SIZE_FACTOR);
+ ksft_print_msg("Iterations: %d\n", NUM_ITERATIONS);
+
+ for (iter = 1; iter <= NUM_ITERATIONS; iter++) {
+ failures = run_iteration();
+ if (failures > 0) {
+ failed = true;
+ ksft_print_msg(
+ "FAILED on iteration %zu: %zu pages corrupted by MADV_REMOVE!\n",
+ iter, failures);
+ break;
+ }
+ }
+
+ if (failed) {
+ ksft_test_result_fail("Test failed\n");
+ ksft_exit_fail();
+ } else {
+ ksft_test_result_pass("All %d iterations passed\n",
+ NUM_ITERATIONS);
+ ksft_exit_pass();
+ }
+
+ return 0;
+}
diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 606558cc3b098..530980fdf3227 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -553,6 +553,8 @@ if [ -n "${MOUNTED_XFS}" ]; then
rm -f ${XFS_IMG}
fi
+CATEGORY="thp" run_test ./folio_split_race_test
+
CATEGORY="migration" run_test ./migration
CATEGORY="mkdirty" run_test ./mkdirty
--
2.51.0(-cc old email) On Thu, Mar 19, 2026 at 03:04:08PM -0400, Zi Yan wrote: > The added folio_split_race_test is a modified C port of the race condition > test from [1]. The test creates shmem huge pages, where the main thread > punches holes in the shmem to cause folio_split() in the kernel and > a set of 16 threads reads the shmem to cause filemap_get_entry() in the > kernel. filemap_get_entry() reads the folio and xarray split by > folio_split() locklessly. The original test[2] is written in rust and uses > memfd (shmem backed). This C port uses shmem directly and use a single > process. > > Note: the initial rust to C conversion is done by Cursor. > > Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1] > Link: https://github.com/dfinity/thp-madv-remove-test [2] > Signed-off-by: Bas van Dijk <bas@dfinity.org> > Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@dfinity.org> > Signed-off-by: Zi Yan <ziy@nvidia.com> No .gitignore entry? :) (Just saw it flag up locally in git status) Linus says don't remove, but he doesn't say don't add :P Cheers, Lorenzo
On 20 Mar 2026, at 13:53, Lorenzo Stoakes (Oracle) wrote: > (-cc old email) > > On Thu, Mar 19, 2026 at 03:04:08PM -0400, Zi Yan wrote: >> The added folio_split_race_test is a modified C port of the race condition >> test from [1]. The test creates shmem huge pages, where the main thread >> punches holes in the shmem to cause folio_split() in the kernel and >> a set of 16 threads reads the shmem to cause filemap_get_entry() in the >> kernel. filemap_get_entry() reads the folio and xarray split by >> folio_split() locklessly. The original test[2] is written in rust and uses >> memfd (shmem backed). This C port uses shmem directly and use a single >> process. >> >> Note: the initial rust to C conversion is done by Cursor. >> >> Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1] >> Link: https://github.com/dfinity/thp-madv-remove-test [2] >> Signed-off-by: Bas van Dijk <bas@dfinity.org> >> Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@dfinity.org> >> Signed-off-by: Zi Yan <ziy@nvidia.com> > > No .gitignore entry? :) > > (Just saw it flag up locally in git status) > > Linus says don't remove, but he doesn't say don't add :P I did not know about that. The fixup is below. Thank you for pointing it out. From bd164a7090c0e8b6e3013502c64c161214e38714 Mon Sep 17 00:00:00 2001 From: Zi Yan <ziy@nvidia.com> Date: Fri, 20 Mar 2026 13:56:04 -0400 Subject: [PATCH] git: add generated binary into gitignore Signed-off-by: Zi Yan <ziy@nvidia.com> --- tools/testing/selftests/mm/.gitignore | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index 83ad9454dd9d1..b0c30c5ee9e30 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -61,3 +61,4 @@ guard-regions merge prctl_thp_disable rmap +folio_split_race_test -- 2.51.0 Best Regards, Yan, Zi
On Fri, Mar 20, 2026 at 01:58:18PM -0400, Zi Yan wrote: > On 20 Mar 2026, at 13:53, Lorenzo Stoakes (Oracle) wrote: > > > (-cc old email) > > > > On Thu, Mar 19, 2026 at 03:04:08PM -0400, Zi Yan wrote: > >> The added folio_split_race_test is a modified C port of the race condition > >> test from [1]. The test creates shmem huge pages, where the main thread > >> punches holes in the shmem to cause folio_split() in the kernel and > >> a set of 16 threads reads the shmem to cause filemap_get_entry() in the > >> kernel. filemap_get_entry() reads the folio and xarray split by > >> folio_split() locklessly. The original test[2] is written in rust and uses > >> memfd (shmem backed). This C port uses shmem directly and use a single > >> process. > >> > >> Note: the initial rust to C conversion is done by Cursor. > >> > >> Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1] > >> Link: https://github.com/dfinity/thp-madv-remove-test [2] > >> Signed-off-by: Bas van Dijk <bas@dfinity.org> > >> Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@dfinity.org> > >> Signed-off-by: Zi Yan <ziy@nvidia.com> > > > > No .gitignore entry? :) > > > > (Just saw it flag up locally in git status) > > > > Linus says don't remove, but he doesn't say don't add :P > > I did not know about that. The fixup is below. Thank you for pointing it out. To be clear I'm referencing this re: the .gitignore _removals_ ;) https://lore.kernel.org/linux-mm/CAHk-=wiHK5_oBUdUiNAaevmN9f-ORe+QBqbRefAZaw-RbgEn3w@mail.gmail.com/ Thanks! :) > > From bd164a7090c0e8b6e3013502c64c161214e38714 Mon Sep 17 00:00:00 2001 > From: Zi Yan <ziy@nvidia.com> > Date: Fri, 20 Mar 2026 13:56:04 -0400 > Subject: [PATCH] git: add generated binary into gitignore > > Signed-off-by: Zi Yan <ziy@nvidia.com> > --- > tools/testing/selftests/mm/.gitignore | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore > index 83ad9454dd9d1..b0c30c5ee9e30 100644 > --- a/tools/testing/selftests/mm/.gitignore > +++ b/tools/testing/selftests/mm/.gitignore > @@ -61,3 +61,4 @@ guard-regions > merge > prctl_thp_disable > rmap > +folio_split_race_test > -- > 2.51.0 > > > > Best Regards, > Yan, Zi Cheers, Lorenzo
On 20 Mar 2026, at 14:04, Lorenzo Stoakes (Oracle) wrote: > On Fri, Mar 20, 2026 at 01:58:18PM -0400, Zi Yan wrote: >> On 20 Mar 2026, at 13:53, Lorenzo Stoakes (Oracle) wrote: >> >>> (-cc old email) >>> >>> On Thu, Mar 19, 2026 at 03:04:08PM -0400, Zi Yan wrote: >>>> The added folio_split_race_test is a modified C port of the race condition >>>> test from [1]. The test creates shmem huge pages, where the main thread >>>> punches holes in the shmem to cause folio_split() in the kernel and >>>> a set of 16 threads reads the shmem to cause filemap_get_entry() in the >>>> kernel. filemap_get_entry() reads the folio and xarray split by >>>> folio_split() locklessly. The original test[2] is written in rust and uses >>>> memfd (shmem backed). This C port uses shmem directly and use a single >>>> process. >>>> >>>> Note: the initial rust to C conversion is done by Cursor. >>>> >>>> Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@mail.gmail.com/ [1] >>>> Link: https://github.com/dfinity/thp-madv-remove-test [2] >>>> Signed-off-by: Bas van Dijk <bas@dfinity.org> >>>> Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@dfinity.org> >>>> Signed-off-by: Zi Yan <ziy@nvidia.com> >>> >>> No .gitignore entry? :) >>> >>> (Just saw it flag up locally in git status) >>> >>> Linus says don't remove, but he doesn't say don't add :P >> >> I did not know about that. The fixup is below. Thank you for pointing it out. > > To be clear I'm referencing this re: the .gitignore _removals_ ;) > > https://lore.kernel.org/linux-mm/CAHk-=wiHK5_oBUdUiNAaevmN9f-ORe+QBqbRefAZaw-RbgEn3w@mail.gmail.com/ > > Thanks! :) I did not know .gitignore file exists in that directory. Also good to know about the do-not-remove rule. > >> >> From bd164a7090c0e8b6e3013502c64c161214e38714 Mon Sep 17 00:00:00 2001 >> From: Zi Yan <ziy@nvidia.com> >> Date: Fri, 20 Mar 2026 13:56:04 -0400 >> Subject: [PATCH] git: add generated binary into gitignore >> >> Signed-off-by: Zi Yan <ziy@nvidia.com> >> --- >> tools/testing/selftests/mm/.gitignore | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore >> index 83ad9454dd9d1..b0c30c5ee9e30 100644 >> --- a/tools/testing/selftests/mm/.gitignore >> +++ b/tools/testing/selftests/mm/.gitignore >> @@ -61,3 +61,4 @@ guard-regions >> merge >> prctl_thp_disable >> rmap >> +folio_split_race_test >> -- >> 2.51.0 >> >> >> >> Best Regards, >> Yan, Zi > > Cheers, Lorenzo Best Regards, Yan, Zi
On Thu, 19 Mar 2026 15:04:08 -0400 Zi Yan <ziy@nvidia.com> wrote: > The added folio_split_race_test is a modified C port of the race condition > test from [1]. The test creates shmem huge pages, where the main thread > punches holes in the shmem to cause folio_split() in the kernel and > a set of 16 threads reads the shmem to cause filemap_get_entry() in the > kernel. filemap_get_entry() reads the folio and xarray split by > folio_split() locklessly. The original test[2] is written in rust and uses > memfd (shmem backed). This C port uses shmem directly and use a single > process. > > Note: the initial rust to C conversion is done by Cursor. Sashiko has questions: https://sashiko.dev/#/patchset/20260319190409.294523-1-ziy%40nvidia.com (this is getting painful :(. I hope they're worthwhile)
On 19 Mar 2026, at 22:41, Andrew Morton wrote: > On Thu, 19 Mar 2026 15:04:08 -0400 Zi Yan <ziy@nvidia.com> wrote: > >> The added folio_split_race_test is a modified C port of the race condition >> test from [1]. The test creates shmem huge pages, where the main thread >> punches holes in the shmem to cause folio_split() in the kernel and >> a set of 16 threads reads the shmem to cause filemap_get_entry() in the >> kernel. filemap_get_entry() reads the folio and xarray split by >> folio_split() locklessly. The original test[2] is written in rust and uses >> memfd (shmem backed). This C port uses shmem directly and use a single >> process. >> >> Note: the initial rust to C conversion is done by Cursor. > > Sashiko has questions: > https://sashiko.dev/#/patchset/20260319190409.294523-1-ziy%40nvidia.com > > (this is getting painful :(. I hope they're worthwhile) Q1: Does this test actually trigger filemap_get_entry() in the kernel? Yes, when MADV_REMOVE triggers folio_split(), in remap_page(), after-split folios are not mapped. So subsequent accesses to these folios will trigger page fault and filemap_get_entry(). Q2: Does this loop advance the index further than intended? Will fix it. Q3: Is it safe to call thp_restore_settings() from a signal handler? There is a theoretical hazard but it is unlikely to happen in practice, since it would only occur when thp_restore_settings() errors out to use printf(). Q4: Use %zu for uint64_t. Will use %" PRIu64 " instead. Best Regards, Yan, Zi
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