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selftests/mm: reimplement is_backed_by_thp() with more precise check

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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.

[ziy@nvidia.com: reduce code duplication, per David]
  Link: https://lkml.kernel.org/r/F54782D6-65A3-4D35-AE03-8ADE636EE258@nvidia.com
Link: https://lkml.kernel.org/r/20250818184622.1521620-4-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: wang lian <lianux.mm@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zi Yan
2025-09-13 16:55:12 -07:00
committed by Andrew Morton
parent 72a07c0390
commit bd66448f2a
3 changed files with 82 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tools/testing/selftests/mm/split_huge_page_test.c
+65 -24
View File
@@ -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 +35,67 @@ 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;
const unsigned long nr_pages = 1UL << order;
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 & ~(nr_pages - 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 < nr_pages; 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 + nr_pages, 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 +276,7 @@ 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 +293,7 @@ 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++;
}
@@ -525,7 +567,6 @@ 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;
@@ -546,28 +587,28 @@ 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))
tools/testing/selftests/mm/vm_util.c
+13
View File
@@ -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)
tools/testing/selftests/mm/vm_util.h
+4
View File
@@ -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);