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@nvidia.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: wang lian <lianux.mm@gmail.com>
---
.../selftests/mm/split_huge_page_test.c | 88 ++++++++++++++-----
tools/testing/selftests/mm/vm_util.c | 13 +++
tools/testing/selftests/mm/vm_util.h | 4 +
3 files changed, 81 insertions(+), 24 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 089e146efeab..56d1eaf9a860 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"
@@ -34,26 +35,66 @@ 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)
-
-static int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
+static bool 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));
+ pfn = pagemap_get_pfn(pagemap_fd, vaddr);
- if (kpageflags_file) {
- pread(kpageflags_file, &page_flags, sizeof(page_flags),
- (paddr & PFN_MASK) * sizeof(page_flags));
+ /* non present page */
+ if (pfn == -1UL)
+ return false;
- return !!(page_flags & KPF_THP);
- }
+ if (pageflags_get(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 false;
+ return true;
}
- return 0;
+
+ /* non THP folio */
+ if (!(pfn_flags & KPF_THP))
+ return false;
+
+ pfn_head = pfn & ~((1 << order) - 1);
+
+ if (pageflags_get(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 false;
+
+ /* check all tail PFN flags */
+ for (i = 1; i < 1UL << order; i++) {
+ if (pageflags_get(pfn_head + i, kpageflags_fd, &pfn_flags))
+ goto fail;
+ if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL)))
+ return false;
+ }
+
+ /*
+ * check the PFN after this folio, but if its flags cannot be obtained,
+ * assume this folio has the expected order
+ */
+ if (pageflags_get(pfn_head + (1UL << order), kpageflags_fd, &pfn_flags))
+ return true;
+
+ /* this folio is bigger than the given order */
+ if (pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL))
+ return false;
+
+ return true;
+fail:
+ ksft_exit_fail_msg("Failed to get folio info\n");
+ return false;
}
static void write_file(const char *path, const char *buf, size_t buflen)
@@ -234,7 +275,7 @@ 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))
thp_size++;
if (thp_size != 4)
@@ -251,7 +292,7 @@ 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))
thp_size++;
}
@@ -523,7 +564,6 @@ 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;
@@ -544,28 +584,28 @@ int main(int argc, char **argv)
ksft_exit_fail_msg("Reading PMD pagesize failed\n");
nr_pages = pmd_pagesize / pagesize;
- max_order = sz2ord(pmd_pagesize, pagesize);
- tests = 2 + (max_order - 1) + (2 * max_order) + (max_order - 1) * 4 + 2;
+ pmd_order = sz2ord(pmd_pagesize, pagesize);
+ 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..741fc129313d 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 pageflags_get(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 3da56feeb944..ab8722f482ae 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 pageflags_get(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);
--
2.50.1On 18.08.25 20:46, Zi Yan wrote:
> 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@nvidia.com>
> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
> Reviewed-by: wang lian <lianux.mm@gmail.com>
> ---
> .../selftests/mm/split_huge_page_test.c | 88 ++++++++++++++-----
> tools/testing/selftests/mm/vm_util.c | 13 +++
> tools/testing/selftests/mm/vm_util.h | 4 +
> 3 files changed, 81 insertions(+), 24 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index 089e146efeab..56d1eaf9a860 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"
> @@ -34,26 +35,66 @@ 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)
> -
> -static int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
> +static bool 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;
Final nit (sorry!) :)
const unsigned long nr_pages = 1ul << order;
so you can make some of the code below easier to read.
Acked-by: David Hildenbrand <david@redhat.com>
--
Cheers
David / dhildenb
On 19 Aug 2025, at 4:54, David Hildenbrand wrote:
> On 18.08.25 20:46, Zi Yan wrote:
>> 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@nvidia.com>
>> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
>> Reviewed-by: wang lian <lianux.mm@gmail.com>
>> ---
>> .../selftests/mm/split_huge_page_test.c | 88 ++++++++++++++-----
>> tools/testing/selftests/mm/vm_util.c | 13 +++
>> tools/testing/selftests/mm/vm_util.h | 4 +
>> 3 files changed, 81 insertions(+), 24 deletions(-)
>>
>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
>> index 089e146efeab..56d1eaf9a860 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"
>> @@ -34,26 +35,66 @@ 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)
>> -
>> -static int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
>> +static bool 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;
>
> Final nit (sorry!) :)
>
> const unsigned long nr_pages = 1ul << order;
>
> so you can make some of the code below easier to read.
Sure. Will send a fixup.
>
> Acked-by: David Hildenbrand <david@redhat.com>
>
Thanks.
--
Best Regards,
Yan, Zi
On 19 Aug 2025, at 12:50, Zi Yan wrote:
> On 19 Aug 2025, at 4:54, David Hildenbrand wrote:
>
>> On 18.08.25 20:46, Zi Yan wrote:
>>> 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@nvidia.com>
>>> Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
>>> Reviewed-by: wang lian <lianux.mm@gmail.com>
>>> ---
>>> .../selftests/mm/split_huge_page_test.c | 88 ++++++++++++++-----
>>> tools/testing/selftests/mm/vm_util.c | 13 +++
>>> tools/testing/selftests/mm/vm_util.h | 4 +
>>> 3 files changed, 81 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
>>> index 089e146efeab..56d1eaf9a860 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"
>>> @@ -34,26 +35,66 @@ 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)
>>> -
>>> -static int is_backed_by_thp(char *vaddr, int pagemap_file, int kpageflags_file)
>>> +static bool 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;
>>
>> Final nit (sorry!) :)
>>
>> const unsigned long nr_pages = 1ul << order;
>>
>> so you can make some of the code below easier to read.
>
> Sure. Will send a fixup.
>
>>
>> Acked-by: David Hildenbrand <david@redhat.com>
>>
> Thanks.
Hi Andrew,
The fixup below replaced 1 << order with nr_pages based on David's
suggestion. Do you mind folding it in?
Thanks.
From c07eb882465b938a70acb84e4cdc5b6598536322 Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@nvidia.com>
Date: Tue, 19 Aug 2025 12:52:13 -0400
Subject: [PATCH] fixup: selftests/mm: use nr_pages instead of 1UL << order.
Signed-off-by: Zi Yan <ziy@nvidia.com>
---
tools/testing/selftests/mm/split_huge_page_test.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 56d1eaf9a860..f2882cfab568 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -38,6 +38,7 @@ unsigned int pmd_order;
static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
int kpageflags_fd)
{
+ const unsigned long nr_pages = 1UL << order;
unsigned long pfn_head;
uint64_t pfn_flags;
unsigned long pfn;
@@ -63,7 +64,7 @@ static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
if (!(pfn_flags & KPF_THP))
return false;
- pfn_head = pfn & ~((1 << order) - 1);
+ pfn_head = pfn & ~(nr_pages - 1);
if (pageflags_get(pfn_head, kpageflags_fd, &pfn_flags))
goto fail;
@@ -73,7 +74,7 @@ static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
return false;
/* check all tail PFN flags */
- for (i = 1; i < 1UL << order; i++) {
+ for (i = 1; i < nr_pages; i++) {
if (pageflags_get(pfn_head + i, kpageflags_fd, &pfn_flags))
goto fail;
if (!(pfn_flags & (KPF_THP | KPF_COMPOUND_TAIL)))
@@ -84,7 +85,7 @@ static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
* check the PFN after this folio, but if its flags cannot be obtained,
* assume this folio has the expected order
*/
- if (pageflags_get(pfn_head + (1UL << order), kpageflags_fd, &pfn_flags))
+ if (pageflags_get(pfn_head + nr_pages, kpageflags_fd, &pfn_flags))
return true;
/* this folio is bigger than the given order */
--
2.50.1
--
Best Regards,
Yan, Zi
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