[PATCH] virtio-9p: fix build on !CONFIG_UTIMENSAT v2

[Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>]

This patch introduce a fallback mechanism for old systems that do not
support utimensat.  This will fix build failure with following warnings:

hw/virtio-9p-local.c: In function 'local_utimensat':
hw/virtio-9p-local.c:479: warning: implicit declaration of function 'utimensat'
hw/virtio-9p-local.c:479: warning: nested extern declaration of 'utimensat'

and

hw/virtio-9p.c: In function 'v9fs_setattr_post_chmod':
hw/virtio-9p.c:1410: error: 'UTIME_NOW' undeclared (first use in this function)
hw/virtio-9p.c:1410: error: (Each undeclared identifier is reported only once
hw/virtio-9p.c:1410: error: for each function it appears in.)
hw/virtio-9p.c:1413: error: 'UTIME_OMIT' undeclared (first use in this function)
hw/virtio-9p.c: In function 'v9fs_wstat_post_chmod':
hw/virtio-9p.c:2905: error: 'UTIME_OMIT' undeclared (first use in this function)

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
---
 hw/virtio-9p-local.c |   32 ++++++++++++++++++++++++++++++--
 hw/virtio-9p.h       |   10 ++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/hw/virtio-9p-local.c b/hw/virtio-9p-local.c
index 0d52020..7811d2c 100644
--- a/hw/virtio-9p-local.c
+++ b/hw/virtio-9p-local.c
@@ -479,10 +479,38 @@ static int local_chown(FsContext *fs_ctx, const char *path, FsCred *credp)
     return -1;
 }
 
+/* TODO: relocate this to proper file, and make it more generic */
+static int qemu_utimensat(int dirfd, const char *path,
+                          const struct timespec *times, int flags)
+{
+#ifdef CONFIG_UTIMENSAT
+    return utimensat(dirfd, path, times, flags);
+#else
+    /*
+     * Fallback: use utimes() instead of utimensat().
+     * See commit 74bc02b2d2272dc88fb98d43e631eb154717f517 for known problem.
+     */
+    struct timeval tv[2];
+    int i;
+
+    for (i = 0; i < 2; i++) {
+        if (times[i].tv_nsec == UTIME_OMIT || times[i].tv_nsec == UTIME_NOW) {
+            tv[i].tv_sec = 0;
+            tv[i].tv_usec = 0;
+        } else {
+            tv[i].tv_sec = times[i].tv_sec;
+            tv[i].tv_usec = times[i].tv_nsec / 1000;
+        }
+    }
+
+    return utimes(path, &tv[0]);
+#endif
+}
+
 static int local_utimensat(FsContext *s, const char *path,
-		       const struct timespec *buf)
+                           const struct timespec *buf)
 {
-    return utimensat(AT_FDCWD, rpath(s, path), buf, AT_SYMLINK_NOFOLLOW);
+    return qemu_utimensat(AT_FDCWD, rpath(s, path), buf, AT_SYMLINK_NOFOLLOW);
 }
 
 static int local_remove(FsContext *ctx, const char *path)
diff --git a/hw/virtio-9p.h b/hw/virtio-9p.h
index 6c23319..d448d8a 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -8,6 +8,16 @@
 
 #include "file-op-9p.h"
 
+/* TODO: relocate this to proper file */
+#ifndef CONFIG_UTIMENSAT
+#ifndef UTIME_NOW
+# define UTIME_NOW     ((1l << 30) - 1l)
+#endif
+#ifndef UTIME_OMIT
+# define UTIME_OMIT    ((1l << 30) - 2l)
+#endif
+#endif
+
 /* The feature bitmap for virtio 9P */
 /* The mount point is specified in a config variable */
 #define VIRTIO_9P_MOUNT_TAG 0
-- 
1.7.3.1