+ selftests-hmm-tests-add-test-for-dirty-bits.patch added to mm-unstable branch

+ selftests-hmm-tests-add-test-for-dirty-bits.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: selftests/hmm-tests: add test for dirty bits
has been added to the -mm mm-unstable branch.  Its filename is
     selftests-hmm-tests-add-test-for-dirty-bits.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-hmm-tests-add-test-for-dirty-bits.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: Alistair Popple <apopple@nvidia.com>
Subject: selftests/hmm-tests: add test for dirty bits
Date: Tue, 16 Aug 2022 17:39:25 +1000

We were not correctly copying PTE dirty bits to pages during
migrate_vma_setup() calls.  This could potentially lead to data loss, so
add a test for this.

Link: https://lkml.kernel.org/r/23069a5c6e07d16d4c4f0951ff003591ffc4f656.1660635033.git-series.apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/hmm-tests.c |  124 +++++++++++++++++++++++
 1 file changed, 124 insertions(+)

--- a/tools/testing/selftests/vm/hmm-tests.c~selftests-hmm-tests-add-test-for-dirty-bits
+++ a/tools/testing/selftests/vm/hmm-tests.c
@@ -1240,6 +1240,130 @@ TEST_F(hmm, migrate_multiple)
 	}
 }
 
+static char cgroup[] = "/sys/fs/cgroup/hmm-test-XXXXXX";
+static int write_cgroup_param(char *cgroup_path, char *param, long value)
+{
+	int ret;
+	FILE *f;
+	char *filename;
+
+	if (asprintf(&filename, "%s/%s", cgroup_path, param) < 0)
+		return -1;
+
+	f = fopen(filename, "w");
+	if (!f) {
+		ret = -1;
+		goto out;
+	}
+
+	ret = fprintf(f, "%ld\n", value);
+	if (ret < 0)
+		goto out1;
+
+	ret = 0;
+
+out1:
+	fclose(f);
+out:
+	free(filename);
+
+	return ret;
+}
+
+static int setup_cgroup(void)
+{
+	pid_t pid = getpid();
+	int ret;
+
+	if (!mkdtemp(cgroup))
+		return -1;
+
+	ret = write_cgroup_param(cgroup, "cgroup.procs", pid);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int destroy_cgroup(void)
+{
+	pid_t pid = getpid();
+	int ret;
+
+	ret = write_cgroup_param("/sys/fs/cgroup/cgroup.procs",
+				"cgroup.proc", pid);
+	if (ret)
+		return ret;
+
+	if (rmdir(cgroup))
+		return -1;
+
+	return 0;
+}
+
+/*
+ * Try and migrate a dirty page that has previously been swapped to disk. This
+ * checks that we don't loose dirty bits.
+ */
+TEST_F(hmm, migrate_dirty_page)
+{
+	struct hmm_buffer *buffer;
+	unsigned long npages;
+	unsigned long size;
+	unsigned long i;
+	int *ptr;
+	int tmp = 0;
+
+	npages = ALIGN(HMM_BUFFER_SIZE, self->page_size) >> self->page_shift;
+	ASSERT_NE(npages, 0);
+	size = npages << self->page_shift;
+
+	buffer = malloc(sizeof(*buffer));
+	ASSERT_NE(buffer, NULL);
+
+	buffer->fd = -1;
+	buffer->size = size;
+	buffer->mirror = malloc(size);
+	ASSERT_NE(buffer->mirror, NULL);
+
+	ASSERT_EQ(setup_cgroup(), 0);
+
+	buffer->ptr = mmap(NULL, size,
+			   PROT_READ | PROT_WRITE,
+			   MAP_PRIVATE | MAP_ANONYMOUS,
+			   buffer->fd, 0);
+	ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+	/* Initialize buffer in system memory. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = 0;
+
+	ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30));
+
+	/* Fault pages back in from swap as clean pages */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		tmp += ptr[i];
+
+	/* Dirty the pte */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ptr[i] = i;
+
+	/*
+	 * Attempt to migrate memory to device, which should fail because
+	 * hopefully some pages are backed by swap storage.
+	 */
+	ASSERT_TRUE(hmm_migrate_sys_to_dev(self->fd, buffer, npages));
+
+	ASSERT_FALSE(write_cgroup_param(cgroup, "memory.reclaim", 1UL<<30));
+
+	/* Check we still see the updated data after restoring from swap. */
+	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+		ASSERT_EQ(ptr[i], i);
+
+	hmm_buffer_free(buffer);
+	destroy_cgroup();
+}
+
 /*
  * Read anonymous memory multiple times.
  */
_

Patches currently in -mm which might be from apopple@nvidia.com are

mm-migrate_devicec-copy-pte-dirty-bit-to-page.patch
mm-gupc-simplify-and-fix-check_and_migrate_movable_pages-return-codes.patch
selftests-hmm-tests-add-test-for-dirty-bits.patch