posix: use nanosecond accuracy when available

Programs that set mtime, such as `rsync -a`, don't work correctly on
GlusterFS, because it sets the nanoseconds to 000. This creates
problems for incremental backups, where files get accidentally copied
again and again.

For example, consider `myfile` on an ext4 system, being copied to a
GlusterFS volume, with `rsync -a` and then `cp -u` in turn. You'd
expect that after the first `rsync -a`, `cp -u` agrees that the file
need not be copied.

BUG: 1422074
Change-Id: I89c7b6a73e2e06c02851ff76b7e5cdfaa271e985
Signed-off-by: Niklas Hambüchen <mail@nh2.me>
Reviewed-on: https://review.gluster.org/16667
Smoke: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Tested-by: Jeff Darcy <jdarcy@redhat.com>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
Reviewed-by: jiffin tony Thottan <jthottan@redhat.com>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>

4 files changed, 49 insertions, 6 deletions

diff --git a/libglusterfs/src/common-utils.c b/libglusterfs/src/common-utils.c
index 51f97442fec..e18c97f5aa1 100644
--- a/libglusterfs/src/common-utils.c
+++ b/libglusterfs/src/common-utils.c
@@ -3806,7 +3806,11 @@ int
 gf_set_timestamp  (const char *src, const char* dest)
 {
         struct stat    sb             = {0, };
-        struct timeval new_time[2]    = {{0, },{0,}};
+#if defined(HAVE_UTIMENSAT)
+        struct timespec new_time[2]   = { {0, }, {0, } };
+#else
+        struct timeval new_time[2]    = { {0, }, {0, } };
+#endif
         int            ret            = 0;
         xlator_t       *this          = NULL;
 
@@ -3821,21 +3825,35 @@ gf_set_timestamp  (const char *src, const char* dest)
                         LG_MSG_FILE_STAT_FAILED, "stat on %s", src);
                 goto out;
         }
+        /* The granularity is nano seconds if `utimensat()` is available,
+         * and micro seconds otherwise.
+         */
+#if defined(HAVE_UTIMENSAT)
+        new_time[0].tv_sec = sb.st_atime;
+        new_time[0].tv_nsec = ST_ATIM_NSEC (&sb);
+
+        new_time[1].tv_sec = sb.st_mtime;
+        new_time[1].tv_nsec = ST_MTIM_NSEC (&sb);
+
+        /* dirfd = 0 is ignored because `dest` is an absolute path. */
+        ret = sys_utimensat (AT_FDCWD, dest, new_time, AT_SYMLINK_NOFOLLOW);
+        if (ret) {
+                gf_msg (this->name, GF_LOG_ERROR, errno,
+                        LG_MSG_UTIMENSAT_FAILED, "utimensat on %s", dest);
+        }
+#else
         new_time[0].tv_sec = sb.st_atime;
         new_time[0].tv_usec = ST_ATIM_NSEC (&sb)/1000;
 
         new_time[1].tv_sec = sb.st_mtime;
         new_time[1].tv_usec = ST_MTIM_NSEC (&sb)/1000;
 
-        /* The granularity is micro seconds as per the current
-         * requiremnt. Hence using 'utimes'. This can be updated
-         * to 'utimensat' if we need timestamp in nanoseconds.
-         */
         ret = sys_utimes (dest, new_time);
         if (ret) {
                 gf_msg (this->name, GF_LOG_ERROR, errno, LG_MSG_UTIMES_FAILED,
                         "utimes on %s", dest);
         }
+#endif
 out:
         return ret;
 }
diff --git a/libglusterfs/src/libglusterfs-messages.h b/libglusterfs/src/libglusterfs-messages.h
index 29196929eb3..23ed7b727d3 100644
--- a/libglusterfs/src/libglusterfs-messages.h
+++ b/libglusterfs/src/libglusterfs-messages.h
@@ -37,7 +37,7 @@
 
 #define GLFS_LG_BASE            GLFS_MSGID_COMP_LIBGLUSTERFS
 
-#define GLFS_LG_NUM_MESSAGES    209
+#define GLFS_LG_NUM_MESSAGES    210
 
 #define GLFS_LG_MSGID_END       (GLFS_LG_BASE + GLFS_LG_NUM_MESSAGES + 1)
 /* Messaged with message IDs */
@@ -1791,6 +1791,15 @@
  * @recommendedaction
  *
  */
+
+#define LG_MSG_UTIMENSAT_FAILED                          (GLFS_LG_BASE + 210)
+
+/*!
+ * @messageid
+ * @diagnosis
+ * @recommendedaction
+ *
+ */
 /*------------*/
 
 #define glfs_msg_end_lg GLFS_LG_MSGID_END, "Invalid: End of messages"
diff --git a/libglusterfs/src/syscall.c b/libglusterfs/src/syscall.c
index 4e4c6a728da..a7d4402808d 100644
--- a/libglusterfs/src/syscall.c
+++ b/libglusterfs/src/syscall.c
@@ -272,6 +272,16 @@ sys_utimes (const char *filename, const struct timeval times[2])
 }
 
 
+#if defined(HAVE_UTIMENSAT)
+int
+sys_utimensat (int dirfd, const char *filename, const struct timespec times[2],
+               int flags)
+{
+        return utimensat (dirfd, filename, times, flags);
+}
+#endif
+
+
 int
 sys_creat (const char *pathname, mode_t mode)
 {
diff --git a/libglusterfs/src/syscall.h b/libglusterfs/src/syscall.h
index b1bcad138c5..6bb374822ee 100644
--- a/libglusterfs/src/syscall.h
+++ b/libglusterfs/src/syscall.h
@@ -129,6 +129,12 @@ sys_ftruncate (int fd, off_t length);
 int
 sys_utimes (const char *filename, const struct timeval times[2]);
 
+#if defined(HAVE_UTIMENSAT)
+int
+sys_utimensat (int dirfd, const char *filename, const struct timespec times[2],
+               int flags);
+#endif
+
 int
 sys_creat (const char *pathname, mode_t mode);