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Message-ID: <20250815023915.1394655-4-ziy@nvidia.com>
Date: Thu, 14 Aug 2025 22:39:12 -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 3/5] selftests/mm: reimplement is_backed_by_thp() with more precise check
and rename it to is_backed_by_folio().
is_backed_by_folio() checks if the given vaddr is backed a folio with
a given order. It does so by:
1. getting the pfn of the vaddr;
2. checking kpageflags of the pfn;
if order is greater than 0:
3. checking kpageflags of the head pfn;
4. checking kpageflags of all tail pfns.
pmd_order is added to split_huge_page_test.c and replaces max_order.
Signed-off-by: Zi Yan <ziy@...dia.com>
---
.../selftests/mm/split_huge_page_test.c | 90 ++++++++++++++-----
tools/testing/selftests/mm/vm_util.c | 13 +++
tools/testing/selftests/mm/vm_util.h | 4 +
3 files changed, 84 insertions(+), 23 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 89d3dc08fe4c..80f718ca21c7 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -25,6 +25,7 @@
uint64_t pagesize;
unsigned int pageshift;
uint64_t pmd_pagesize;
+unsigned int pmd_order;
#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
#define SMAP_PATH "/proc/self/smaps"
@@ -34,27 +35,71 @@ uint64_t pmd_pagesize;
#define PID_FMT_OFFSET "%d,0x%lx,0x%lx,%d,%d"
#define PATH_FMT "%s,0x%lx,0x%lx,%d"
-#define PFN_MASK ((1UL<<55)-1)
-#define KPF_THP (1UL<<22)
#define GET_ORDER(nr_pages) (31 - __builtin_clz(nr_pages))
-static int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
+static int is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
+ int kpageflags_fd)
{
- uint64_t paddr;
- uint64_t page_flags;
+ unsigned long pfn_head;
+ uint64_t pfn_flags;
+ unsigned long pfn;
+ unsigned long i;
- if (pagemap_file) {
- pread(pagemap_file, &paddr, sizeof(paddr),
- ((long)vaddr >> pageshift) * sizeof(paddr));
+ if (pagemap_fd == -1 || kpageflags_fd == -1)
+ goto fail;
- if (kpageflags_file) {
- pread(kpageflags_file, &page_flags, sizeof(page_flags),
- (paddr & PFN_MASK) * sizeof(page_flags));
+ pfn = pagemap_get_pfn(pagemap_fd, vaddr);
- return !!(page_flags & KPF_THP);
- }
+ /* non present page */
+ if (pfn == -1UL)
+ return 0;
+
+ if (get_pfn_flags(pfn, kpageflags_fd, &pfn_flags))
+ goto fail;
+
+ /* check for order-0 pages */
+ if (!order) {
+ if (pfn_flags & (KPF_THP | KPF_COMPOUND_HEAD | KPF_COMPOUND_TAIL))
+ return 0;
+ return 1;
}
- return 0;
+
+ /* non THP folio */
+ if (!(pfn_flags & KPF_THP))
+ return 0;
+
+ pfn_head = pfn & ~((1 << order) - 1);
+
+ if (get_pfn_flags(pfn_head, kpageflags_fd, &pfn_flags))
+ goto fail;
+
+ /* head PFN has no compound_head flag set */
+ if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_HEAD)))
+ return 0;
+
+ /* check all tail PFN flags */
+ for (i = 1; i < 1UL << order; i++) {
+ if (get_pfn_flags(pfn_head + i, kpageflags_fd, &pfn_flags))
+ goto fail;
+ if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL)))
+ return 0;
+ }
+
+ /*
+ * check the PFN after this folio, but if its flags cannot be obtained,
+ * assume this folio has the expected order
+ */
+ if (get_pfn_flags(pfn_head + (1UL << order), kpageflags_fd, &pfn_flags))
+ return 1;
+
+ /* this folio is bigger than the given order */
+ if (pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL))
+ return 0;
+
+ return 1;
+fail:
+ ksft_exit_fail_msg("Failed to get folio info\n");
+ return -1;
}
static void write_file(const char *path, const char *buf, size_t buflen)
@@ -235,7 +280,7 @@ static void split_pte_mapped_thp(void)
thp_size = 0;
for (i = 0; i < pagesize * 4; i++)
if (i % pagesize == 0 &&
- is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
+ is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd) == 1)
thp_size++;
if (thp_size != 4)
@@ -252,7 +297,7 @@ static void split_pte_mapped_thp(void)
ksft_exit_fail_msg("%ld byte corrupted\n", i);
if (i % pagesize == 0 &&
- is_backed_by_thp(&pte_mapped[i], pagemap_fd, kpageflags_fd))
+ is_backed_by_folio(&pte_mapped[i], 0, pagemap_fd, kpageflags_fd) == 0)
thp_size++;
}
@@ -524,7 +569,6 @@ int main(int argc, char **argv)
const char *fs_loc;
bool created_tmp;
int offset;
- unsigned int max_order;
unsigned int nr_pages;
unsigned int tests;
@@ -545,28 +589,28 @@ int main(int argc, char **argv)
ksft_exit_fail_msg("Reading PMD pagesize failed\n");
nr_pages = pmd_pagesize / pagesize;
- max_order = GET_ORDER(nr_pages);
- tests = 2 + (max_order - 1) + (2 * max_order) + (max_order - 1) * 4 + 2;
+ pmd_order = GET_ORDER(nr_pages);
+ tests = 2 + (pmd_order - 1) + (2 * pmd_order) + (pmd_order - 1) * 4 + 2;
ksft_set_plan(tests);
fd_size = 2 * pmd_pagesize;
split_pmd_zero_pages();
- for (i = 0; i < max_order; i++)
+ for (i = 0; i < pmd_order; i++)
if (i != 1)
split_pmd_thp_to_order(i);
split_pte_mapped_thp();
- for (i = 0; i < max_order; i++)
+ for (i = 0; i < pmd_order; i++)
split_file_backed_thp(i);
created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
&fs_loc);
- for (i = max_order - 1; i >= 0; i--)
+ for (i = pmd_order - 1; i >= 0; i--)
split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1);
- for (i = 0; i < max_order; i++)
+ for (i = 0; i < pmd_order; i++)
for (offset = 0;
offset < nr_pages;
offset += MAX(nr_pages / 4, 1 << i))
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 6a239aa413e2..18b7cb51fc56 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -338,6 +338,19 @@ int detect_hugetlb_page_sizes(size_t sizes[], int max)
return count;
}
+int get_pfn_flags(unsigned long pfn, int kpageflags_fd, uint64_t *flags)
+{
+ size_t count;
+
+ count = pread(kpageflags_fd, flags, sizeof(*flags),
+ pfn * sizeof(*flags));
+
+ if (count != sizeof(*flags))
+ return -1;
+
+ return 0;
+}
+
/* If `ioctls' non-NULL, the allowed ioctls will be returned into the var */
int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
bool miss, bool wp, bool minor, uint64_t *ioctls)
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index 1843ad48d32b..03481ca0a1b4 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -18,6 +18,9 @@
#define PM_SWAP BIT_ULL(62)
#define PM_PRESENT BIT_ULL(63)
+#define KPF_COMPOUND_HEAD BIT_ULL(15)
+#define KPF_COMPOUND_TAIL BIT_ULL(16)
+#define KPF_THP BIT_ULL(22)
/*
* Ignore the checkpatch warning, we must read from x but don't want to do
* anything with it in order to trigger a read page fault. We therefore must use
@@ -85,6 +88,7 @@ bool check_huge_shmem(void *addr, int nr_hpages, uint64_t hpage_size);
int64_t allocate_transhuge(void *ptr, int pagemap_fd);
unsigned long default_huge_page_size(void);
int detect_hugetlb_page_sizes(size_t sizes[], int max);
+int get_pfn_flags(unsigned long pfn, int kpageflags_fd, uint64_t *flags);
int uffd_register(int uffd, void *addr, uint64_t len,
bool miss, bool wp, bool minor);
--
2.50.1
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