io: Return UNSUPPORTED if filesystem do not support 64 bit timestamps

Some Linux filesystems might not fully support 64 bit timestamps [1],
which make some Linux specific tests to fail when they check for the
functionality.

This patch adds a new libsupport function, support_path_support_time64,
that returns whether the target file supports or not 64 bit timestamps.
The support is checked by issuing a utimensat and verifying both the
last access and last modification time against a statx call.

The tests that might fail are also adjusted to check the file support
as well:

  $ dd if=/dev/zero of=loopbackfile.img bs=100M count=1
  1+0 records in
  1+0 records out
  104857600 bytes (105 MB, 100 MiB) copied, 0,0589568 s, 1,8 GB/s
  $ sudo losetup -fP loopbackfile.img
  $ mkfs.xfs loopbackfile.img
  meta-data=loopbackfile.img       isize=512    agcount=4, agsize=6400 blks
           =                       sectsz=512   attr=2, projid32bit=1
           =                       crc=1        finobt=1, sparse=1, rmapbt=0
           =                       reflink=1
  data     =                       bsize=4096   blocks=25600, imaxpct=25
           =                       sunit=0      swidth=0 blks
  naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
  log      =internal log           bsize=4096   blocks=1368, version=2
           =                       sectsz=512   sunit=0 blks, lazy-count=1
  realtime =none                   extsz=4096   blocks=0, rtextents=0
  $ mkdir loopfs
  $ sudo mount -o loop /dev/loop0 loopfs/
  $ sudo chown -R azanella:azanella loopfs
  $ TMPDIR=loopfs/ ./testrun.sh misc/tst-utimes
  error: ../sysdeps/unix/sysv/linux/tst-utimes.c:55: File loopfs//utimesfECsK1 does not support 64-bit timestamps

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1795576

1 files changed, 5 insertions, 0 deletions

diff --git a/support/support.h b/support/support.h
index 9cbc455720..2e477c9e7c 100644
--- a/support/support.h
+++ b/support/support.h
@@ -23,6 +23,7 @@
 #ifndef SUPPORT_H
 #define SUPPORT_H
 
+#include <stdbool.h>
 #include <stddef.h>
 #include <sys/cdefs.h>
 /* For mode_t.  */
@@ -129,6 +130,10 @@ extern void support_copy_file (const char *from, const char *to);
 extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
 					size_t, unsigned int);
 
+/* Return true is PATH supports 64-bit time_t interfaces for file
+   operations (such as fstatat or utimensat).  */
+extern bool support_path_support_time64 (const char *path);
+
 __END_DECLS
 
 #endif /* SUPPORT_H */