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Message-ID: <20250815023915.1394655-5-ziy@nvidia.com>
Date: Thu, 14 Aug 2025 22:39:13 -0400
From: Zi Yan <ziy@...dia.com>
To: Wei Yang <richard.weiyang@...il.com>,
wang lian <lianux.mm@...il.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
David Hildenbrand <david@...hat.com>,
linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Zi Yan <ziy@...dia.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Nico Pache <npache@...hat.com>,
Ryan Roberts <ryan.roberts@....com>,
Dev Jain <dev.jain@....com>,
Barry Song <baohua@...nel.org>,
Vlastimil Babka <vbabka@...e.cz>,
Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Michal Hocko <mhocko@...e.com>,
Shuah Khan <shuah@...nel.org>,
linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: [PATCH v4 4/5] selftests/mm: add check_after_split_folio_orders() helper.
The helper gathers a folio order statistics of folios within a virtual
address range and checks it against a given order list. It aims to provide
a more precise folio order check instead of just checking the existence of
PMD folios.
The helper will be used the upcoming commit.
Signed-off-by: Zi Yan <ziy@...dia.com>
---
.../selftests/mm/split_huge_page_test.c | 150 ++++++++++++++++++
1 file changed, 150 insertions(+)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 80f718ca21c7..d2467072e752 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -102,6 +102,156 @@ static int is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
return -1;
}
+static int get_page_flags(char *vaddr, int pagemap_fd, int kpageflags_fd,
+ uint64_t *flags)
+{
+ unsigned long pfn;
+
+ pfn = pagemap_get_pfn(pagemap_fd, vaddr);
+
+ /* non-present PFN */
+ if (pfn == -1UL)
+ return 1;
+
+ if (get_pfn_flags(pfn, kpageflags_fd, flags))
+ return -1;
+
+ return 0;
+}
+
+/*
+ * gather_after_split_folio_orders - scan through [vaddr_start, len) and record
+ * folio orders
+ *
+ * @vaddr_start: start vaddr
+ * @len: range length
+ * @pagemap_fd: file descriptor to /proc/<pid>/pagemap
+ * @kpageflags_fd: file descriptor to /proc/kpageflags
+ * @orders: output folio order array
+ * @nr_orders: folio order array size
+ *
+ * gather_after_split_folio_orders() scan through [vaddr_start, len) and check
+ * all folios within the range and record their orders. All order-0 pages will
+ * be recorded. Non-present vaddr is skipped.
+ *
+ * NOTE: the function is used to check folio orders after a split is performed,
+ * so it assumes [vaddr_start, len) fully maps to folios within that range.
+ *
+ * Return: 0 - no error, -1 - unhandled cases
+ */
+static int gather_after_split_folio_orders(char *vaddr_start, size_t len,
+ int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders)
+{
+ uint64_t page_flags = 0;
+ int cur_order = -1;
+ char *vaddr;
+
+ if (pagemap_fd == -1 || kpageflags_fd == -1)
+ return -1;
+ if (!orders)
+ return -1;
+ if (nr_orders <= 0)
+ return -1;
+
+ for (vaddr = vaddr_start; vaddr < vaddr_start + len;) {
+ char *next_folio_vaddr;
+ int status;
+
+ status = get_page_flags(vaddr, pagemap_fd, kpageflags_fd,
+ &page_flags);
+ if (status < 0)
+ return -1;
+
+ /* skip non present vaddr */
+ if (status == 1) {
+ vaddr += psize();
+ continue;
+ }
+
+ /* all order-0 pages with possible false postive (non folio) */
+ if (!(page_flags & (KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))) {
+ orders[0]++;
+ vaddr += psize();
+ continue;
+ }
+
+ /* skip non thp compound pages */
+ if (!(page_flags & KPF_THP)) {
+ vaddr += psize();
+ continue;
+ }
+
+ /* vpn points to part of a THP at this point */
+ if (page_flags & KPF_COMPOUND_HEAD)
+ cur_order = 1;
+ else {
+ vaddr += psize();
+ continue;
+ }
+
+ next_folio_vaddr = vaddr + (1UL << (cur_order + pshift()));
+
+ if (next_folio_vaddr >= vaddr_start + len)
+ break;
+
+ while ((status = get_page_flags(next_folio_vaddr, pagemap_fd,
+ kpageflags_fd, &page_flags)) >= 0) {
+ /*
+ * non present vaddr, next compound head page, or
+ * order-0 page
+ */
+ if (status == 1 ||
+ (page_flags & KPF_COMPOUND_HEAD) ||
+ !(page_flags & (KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))) {
+ if (cur_order < nr_orders) {
+ orders[cur_order]++;
+ cur_order = -1;
+ vaddr = next_folio_vaddr;
+ }
+ break;
+ }
+
+ cur_order++;
+ next_folio_vaddr = vaddr + (1UL << (cur_order + pshift()));
+ }
+
+ if (status < 0)
+ return status;
+ }
+ if (cur_order > 0 && cur_order < nr_orders)
+ orders[cur_order]++;
+ return 0;
+}
+
+static int check_after_split_folio_orders(char *vaddr_start, size_t len,
+ int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders)
+{
+ int *vaddr_orders;
+ int status;
+ int i;
+
+ vaddr_orders = (int *)malloc(sizeof(int) * nr_orders);
+
+ if (!vaddr_orders)
+ ksft_exit_fail_msg("Cannot allocate memory for vaddr_orders");
+
+ memset(vaddr_orders, 0, sizeof(int) * nr_orders);
+ status = gather_after_split_folio_orders(vaddr_start, len, pagemap_fd,
+ kpageflags_fd, vaddr_orders, nr_orders);
+ if (status)
+ ksft_exit_fail_msg("gather folio info failed\n");
+
+ for (i = 0; i < nr_orders; i++)
+ if (vaddr_orders[i] != orders[i]) {
+ ksft_print_msg("order %d: expected: %d got %d\n", i,
+ orders[i], vaddr_orders[i]);
+ status = -1;
+ }
+
+ free(vaddr_orders);
+ return status;
+}
+
static void write_file(const char *path, const char *buf, size_t buflen)
{
int fd;
--
2.50.1
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