[PATCH v3 1/3] selftests/mm: handle EINVAL when configuring gigantic hugepages

[Sayali Patil <sayalip@linux.ibm.com>]

Some MM selftests attempt to configure the amount of
HugeTLB pages of different sizes by writing to nr_hugepages.

PowerPC hash MMU pSeries systems advertise gigantic hugepage sizes
but do not support runtime allocation of such pages, writes
to the corresponding nr_hugepages file fail with -EINVAL.
This causes the test to bail out even though the failure is due
to a platform limitation rather than the
functionality being tested.

Ignore -EINVAL when configuring nr_hugepages so that tests continue to
run on systems where gigantic hugepage allocation is unsupported.

Before patch:
   -------------------------
   running ./hugetlb-madvise
   -------------------------
   TAP version 13
   1..1
     [INFO] detected hugetlb page size: 16777216 KiB
     [INFO] detected hugetlb page size: 16384 KiB
    ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
    Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
    Bail out! /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages
    write(0) failed: Invalid argument
    Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
    [FAIL]

After patch:
   -------------------------
   running ./hugetlb-madvise
   -------------------------
   TAP version 13
   1..1
    [INFO] detected hugetlb page size: 16777216 KiB
    [INFO] detected hugetlb page size: 16384 KiB
   ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
   Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
   [PASS]

Fixes: 27477b28b74f ("selftests/mm: hugepage_settings: add APIs to get and set nr_hugepages")
Co-developed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
 .../testing/selftests/mm/hugepage_settings.c  |  2 +-
 tools/testing/selftests/mm/vm_util.c          | 26 ++++++++++++++++---
 tools/testing/selftests/mm/vm_util.h          |  1 +
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/mm/hugepage_settings.c b/tools/testing/selftests/mm/hugepage_settings.c
index 2eab2110ac6a..d7917dce3aba 100644
--- a/tools/testing/selftests/mm/hugepage_settings.c
+++ b/tools/testing/selftests/mm/hugepage_settings.c
@@ -437,7 +437,7 @@ void hugetlb_set_nr_pages(unsigned long size, unsigned long nr)
 
 	hugetlb_sysfs_path(path, sizeof(path), size, "nr_hugepages");
 
-	write_num(path, nr);
+	write_num_ignore_einval(path, nr);
 }
 
 unsigned long hugetlb_free_pages(unsigned long size)
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 311fc5b4513e..ef1ea11981a7 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -719,7 +719,7 @@ int read_file(const char *path, char *buf, size_t buflen)
 	return (unsigned int) numread;
 }
 
-void write_file(const char *path, const char *buf, size_t buflen)
+static void __write_file(const char *path, const char *buf, size_t buflen, bool ignore_einval)
 {
 	int fd, saved_errno;
 	ssize_t numwritten;
@@ -735,14 +735,22 @@ void write_file(const char *path, const char *buf, size_t buflen)
 	saved_errno = errno;
 	close(fd);
 	errno = saved_errno;
-	if (numwritten < 0)
+	if (numwritten < 0) {
+		if (ignore_einval && errno == EINVAL)
+			return;
 		ksft_exit_fail_msg("%s write(%.*s) failed: %s\n", path, (int)(buflen - 1),
 				buf, strerror(errno));
+	}
 	if (numwritten != buflen - 1)
 		ksft_exit_fail_msg("%s write(%.*s) is truncated, expected %zu bytes, got %zd bytes\n",
 				path, (int)(buflen - 1), buf, buflen - 1, numwritten);
 }
 
+void write_file(const char *path, const char *buf, size_t buflen)
+{
+	__write_file(path, buf, buflen, /* ignore_einval = */ false);
+}
+
 unsigned long read_num(const char *path)
 {
 	char buf[21];
@@ -753,12 +761,22 @@ unsigned long read_num(const char *path)
 	return strtoul(buf, NULL, 10);
 }
 
-void write_num(const char *path, unsigned long num)
+static void __write_num(const char *path, unsigned long num, bool ignore_einval)
 {
 	char buf[21];
 
 	sprintf(buf, "%lu", num);
-	write_file(path, buf, strlen(buf) + 1);
+	__write_file(path, buf, strlen(buf) + 1, ignore_einval);
+}
+
+void write_num(const char *path, unsigned long num)
+{
+	return __write_num(path, num, /* ignore_einval = */ false);
+}
+
+void write_num_ignore_einval(const char *path, unsigned long num)
+{
+	return __write_num(path, num, /* ignore_einval = */ true);
 }
 
 static unsigned long shmall, shmmax;
diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
index ea8fc8fdf0eb..7799154b67ee 100644
--- a/tools/testing/selftests/mm/vm_util.h
+++ b/tools/testing/selftests/mm/vm_util.h
@@ -168,6 +168,7 @@ void write_file(const char *path, const char *buf, size_t buflen);
 int read_file(const char *path, char *buf, size_t buflen);
 unsigned long read_num(const char *path);
 void write_num(const char *path, unsigned long num);
+void write_num_ignore_einval(const char *path, unsigned long num);
 
 void shm_limits_prepare(unsigned long length);
 void __shm_limits_restore(void);
-- 
2.52.0