Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.

Zi Yan
2024-03-01T20:02:48Z

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On 1 Mar 2024, at 14:37, Zi Yan wrote:

> On 1 Mar 2024, at 4:51, Aishwarya TCV wrote:
>
>> On 26/02/2024 20:55, Zi Yan wrote:
>>> From: Zi Yan <ziy@nvidia.com>
>>>
>>> It is used to test split_huge_page_to_list_to_order for pagecache THPs.
>>> Also add test cases for split_huge_page_to_list_to_order via both
>>> debugfs.
>>>
>>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>>> ---
>>> mm/huge_memory.c | 34 ++++--
>>> .../selftests/mm/split_huge_page_test.c | 115 +++++++++++++++++-
>>> 2 files changed, 131 insertions(+), 18 deletions(-)
>>>
>>
>> Hi Zi,
>>
>> When booting the kernel against next-master(20240228)with Arm64 on
>> Marvell Thunder X2 (TX2), the kselftest-mm test 'split_huge_page_test'
>> is failing in our CI (with rootfs over NFS). I can send the full logs if
>> required.
>>
>> A bisect (full log below) identified this patch as introducing the
>> failure. Bisected it on the tag "next-20240228" at repo
>> "https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git".
>>
>> This works fine on Linux version 6.8.0-rc6
>
> Hi Aishwarya,
>
> Can you try the attached patch and see if it fixes the failure? I changed
> the test to accept XFS dev as input, mount XFS on a temp folder under /tmp,
> and skip if no XFS is mounted.

Please try this updated one. It allows you to specify a XFS device path
in SPLIT_HUGE_PAGE_TEST_XFS_PATH env variable, which is passed to
split_huge_page_test in run_vmtests.sh. It at least allow CI/CD to run
the test without too much change.

--
Best Regards,
Yan, Zi

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diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index fe140a9f4f9d..22e45207cf6b 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -412,7 +412,7 @@ CATEGORY="thp" run_test ./khugepaged -s 2

CATEGORY="thp" run_test ./transhuge-stress -d 20

-CATEGORY="thp" run_test ./split_huge_page_test
+CATEGORY="thp" run_test ./split_huge_page_test ${SPLIT_HUGE_PAGE_TEST_XFS_PATH}

CATEGORY="migration" run_test ./migration

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index cf09fdc9ef22..047883473b84 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -26,7 +26,6 @@ uint64_t pmd_pagesize;

#define SPLIT_DEBUGFS "/sys/kernel/debug/split_huge_pages"
#define SMAP_PATH "/proc/self/smaps"
-#define THP_FS_PATH "/mnt/thp_fs"
#define INPUT_MAX 80

#define PID_FMT "%d,0x%lx,0x%lx,%d"
@@ -268,7 +267,45 @@ void split_file_backed_thp(void)
ksft_exit_fail_msg("Error occurred\n");
}

-void create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd, char **addr)
+bool prepare_thp_fs(const char *xfs_dev_loc, char *thp_fs_template,
+ const char **thp_fs_loc)
+{
+ bool mounted = false;
+
+ *thp_fs_loc = mkdtemp(thp_fs_template);
+
+ if (!*thp_fs_loc)
+ ksft_exit_fail_msg("cannot create temp folder\n");
+
+ if (xfs_dev_loc) {
+ int status = mount(xfs_dev_loc, *thp_fs_loc, "xfs", 0, NULL);
+
+ if (status)
+ ksft_exit_fail_msg("Unable to mount xfs for testing\n");
+ mounted = true;
+ }
+ return mounted;
+}
+
+void cleanup_thp_fs(const char *thp_fs_loc, bool mounted)
+{
+ int status;
+
+ if (mounted) {
+ status = umount(thp_fs_loc);
+ if (status)
+ ksft_exit_fail_msg("Unable to umount %s\n",
+ thp_fs_loc);
+ }
+
+ status = rmdir(thp_fs_loc);
+ if (status)
+ ksft_exit_fail_msg("cannot remove tmp dir: %s\n",
+ strerror(errno));
+}
+
+int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,
+ char **addr)
{
size_t i;
int dummy;
@@ -277,7 +314,7 @@ void create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,

*fd = open(testfile, O_CREAT | O_RDWR, 0664);
if (*fd == -1)
- ksft_exit_fail_msg("Failed to create a file at "THP_FS_PATH);
+ ksft_exit_fail_msg("Failed to create a file at %s\n", testfile);

for (i = 0; i < fd_size; i++) {
unsigned char byte = (unsigned char)i;
@@ -299,7 +336,7 @@ void create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,

*fd = open(testfile, O_RDWR);
if (*fd == -1) {
- ksft_perror("Failed to open a file at "THP_FS_PATH);
+ ksft_perror("Failed to open testfile\n");
goto err_out_unlink;
}

@@ -314,26 +351,37 @@ void create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,
dummy += *(*addr + i);

if (!check_huge_file(*addr, fd_size / pmd_pagesize, pmd_pagesize)) {
- ksft_print_msg("No large pagecache folio generated, please mount a filesystem supporting large folio at "THP_FS_PATH"\n");
- goto err_out_close;
+ ksft_print_msg("No large pagecache folio generated, please provide a filesystem supporting large folio\n");
+ unlink(testfile);
+ ksft_test_result_skip("Pagecache folio split skipped\n");
+ return -2;
}
- return;
+ return 0;
err_out_close:
close(*fd);
err_out_unlink:
unlink(testfile);
ksft_exit_fail_msg("Failed to create large pagecache folios\n");
+ return -1;
}

-void split_thp_in_pagecache_to_order(size_t fd_size, int order)
+void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_loc)
{
int fd;
char *addr;
size_t i;
- const char testfile[] = THP_FS_PATH "/test";
+ char testfile[INPUT_MAX];
int err = 0;

- create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
+ err = snprintf(testfile, INPUT_MAX, "%s/test", fs_loc);
+
+ if (err < 0)
+ ksft_exit_fail_msg("cannot generate right test file name\n");
+
+ err = create_pagecache_thp_and_fd(testfile, fd_size, &fd, &addr);
+ if (err)
+ return;
+ err = 0;

write_debugfs(PID_FMT, getpid(), (uint64_t)addr, (uint64_t)addr + fd_size, order);

@@ -351,6 +399,7 @@ void split_thp_in_pagecache_to_order(size_t fd_size, int order)
}

out:
+ munmap(addr, fd_size);
close(fd);
unlink(testfile);
if (err)
@@ -360,8 +409,11 @@ void split_thp_in_pagecache_to_order(size_t fd_size, int order)

int main(int argc, char **argv)
{
- int i;
+ int i, mounted;
size_t fd_size;
+ char *optional_xfs_dev_loc = NULL;
+ char fs_loc_template[] = "/tmp/thp_fs_XXXXXX";
+ const char *fs_loc;

ksft_print_header();

@@ -370,6 +422,9 @@ int main(int argc, char **argv)
ksft_finished();
}

+ if (argc > 1)
+ optional_xfs_dev_loc = argv[1];
+
ksft_set_plan(3+9);

pagesize = getpagesize();
@@ -384,8 +439,11 @@ int main(int argc, char **argv)
split_pte_mapped_thp();
split_file_backed_thp();

+ mounted = prepare_thp_fs(optional_xfs_dev_loc, fs_loc_template,
+ &fs_loc);
for (i = 8; i >= 0; i--)
- split_thp_in_pagecache_to_order(fd_size, i);
+ split_thp_in_pagecache_to_order(fd_size, i, fs_loc);
+ cleanup_thp_fs(fs_loc, mounted);

ksft_finished();

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