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* [glibc] io: Check at runtime if timestamp supports nanoseconds
@ 2021-03-31 20:47 Adhemerval Zanella
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From: Adhemerval Zanella @ 2021-03-31 20:47 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=bfddda2570331da2ae4387b530456e6c4e230257
commit bfddda2570331da2ae4387b530456e6c4e230257
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon Mar 29 14:40:30 2021 -0300
io: Check at runtime if timestamp supports nanoseconds
Now that non-LFS stat function is implemented on to on LFS, it will
use statx when available. It allows to check for nanosecond timestamp
if the kernel supports __NR_statx.
Checked on s390-linux-gnu with 4.12.14 kernel.
Diff:
---
io/tst-stat.c | 7 ++++++-
support/support.h | 2 +-
support/support_stat_nanoseconds.c | 40 +++++++++++++++++++++++++++++++-------
3 files changed, 40 insertions(+), 9 deletions(-)
diff --git a/io/tst-stat.c b/io/tst-stat.c
index 397d480ecc..22b89bb3e7 100644
--- a/io/tst-stat.c
+++ b/io/tst-stat.c
@@ -25,6 +25,7 @@
#include <support/xunistd.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
+#include <stdio.h>
#include <unistd.h>
static void
@@ -73,6 +74,10 @@ do_test (void)
test_t tests[] = { stat_check, lstat_check, fstat_check, fstatat_check };
+ bool check_ns = support_stat_nanoseconds (path);
+ if (!check_ns)
+ printf ("warning: timestamp with nanoseconds not supportted\n");
+
for (int i = 0; i < array_length (tests); i++)
{
struct stat st;
@@ -92,7 +97,7 @@ do_test (void)
TEST_COMPARE (stx.stx_ctime.tv_sec, st.st_ctim.tv_sec);
TEST_COMPARE (stx.stx_mtime.tv_sec, st.st_mtim.tv_sec);
- if (support_stat_nanoseconds ())
+ if (check_ns)
{
TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
diff --git a/support/support.h b/support/support.h
index b0352726bf..e023d00857 100644
--- a/support/support.h
+++ b/support/support.h
@@ -142,7 +142,7 @@ static __inline bool support_path_support_time64 (const char *path)
}
/* Return true if stat supports nanoseconds resolution. */
-extern bool support_stat_nanoseconds (void);
+extern bool support_stat_nanoseconds (const char *path);
__END_DECLS
diff --git a/support/support_stat_nanoseconds.c b/support/support_stat_nanoseconds.c
index c0d5b2c3a9..6a9e49cc88 100644
--- a/support/support_stat_nanoseconds.c
+++ b/support/support_stat_nanoseconds.c
@@ -16,16 +16,42 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
+#include <errno.h>
+#include <fcntl.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/timespec.h>
#include <stdbool.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
bool
-support_stat_nanoseconds (void)
+support_stat_nanoseconds (const char *path)
{
- /* s390 stat64 compat symbol does not support nanoseconds resolution
- and it used on non-LFS [f,l]stat[at] implementations. */
-#if defined __linux__ && !defined __s390x__ && defined __s390__
- return false;
-#else
- return true;
+ bool support;
+#ifdef __linux__
+ /* Obtain the original timestamp to restore at the end. */
+ struct stat ost;
+ TEST_VERIFY_EXIT (stat (path, &ost) == 0);
+
+ const struct timespec tsp[] = { { 0, TIMESPEC_HZ - 1 },
+ { 0, TIMESPEC_HZ / 2 } };
+ TEST_VERIFY_EXIT (utimensat (AT_FDCWD, path, tsp, 0) == 0);
+
+ struct stat st;
+ TEST_VERIFY_EXIT (stat (path, &st) == 0);
+
+ support = st.st_atim.tv_nsec == tsp[0].tv_nsec
+ && st.st_mtim.tv_nsec == tsp[1].tv_nsec;
+
+ /* Reset to original timestamps. */
+ const struct timespec otsp[] =
+ {
+ { ost.st_atim.tv_sec, ost.st_atim.tv_nsec },
+ { ost.st_mtim.tv_sec, ost.st_mtim.tv_nsec },
+ };
+ TEST_VERIFY_EXIT (utimensat (AT_FDCWD, path, otsp, 0) == 0);
#endif
+ return support;
}
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