Fixes to resolve the read cache status as reported by tap-ctl stats

drivers/block-vhd.c

@@ -832,6 +832,21 @@ _vhd_close(td_driver_t *driver)
 	return 0;
 }
 
+static int
+vhd_get_oflags(td_driver_t *driver, int *flags)
+{
+	struct vhd_state *s = driver->data;
+
+	*flags = fcntl(s->vhd.fd, F_GETFL, 0);
+	if (*flags == -1){
+		*flags = 0;
+		ERR(s, -errno, "fcntl failed\n");
+		return -errno;
+	}
+
+	return 0;
+}
+
 int
 vhd_validate_parent(td_driver_t *child_driver,
 		    td_driver_t *parent_driver, td_flag_t flags)
@@ -2479,6 +2494,7 @@ struct tap_disk tapdisk_vhd = {
 	.private_data_size  = sizeof(struct vhd_state),
 	.td_open            = _vhd_open,
 	.td_close           = _vhd_close,
+	.td_get_oflags      = vhd_get_oflags,
 	.td_queue_read      = vhd_queue_read,
 	.td_queue_write     = vhd_queue_write,
 	.td_get_parent_id   = vhd_get_parent_id,

drivers/tapdisk-interface.c

@@ -120,6 +120,24 @@ td_close(td_image_t *image)
 	return 0;
 }
 
+int
+td_get_oflags(td_image_t *image, int *flags)
+{
+	td_driver_t *driver;
+
+	driver = image->driver;
+	if (!driver)
+		return -ENODEV;
+
+	if (!td_flag_test(driver->state, TD_DRIVER_OPEN))
+		return -EBADF;
+
+	if (!driver->ops->td_get_oflags)
+		return -ENOTSUP;
+
+	return driver->ops->td_get_oflags(driver, flags);
+}
+
 int
 td_get_parent_id(td_image_t *image, td_disk_id_t *id)
 {

drivers/tapdisk-interface.h

@@ -27,6 +27,7 @@ int td_open(td_image_t *);
 int __td_open(td_image_t *, td_disk_info_t *);
 int td_load(td_image_t *);
 int td_close(td_image_t *);
+int td_get_oflags(td_image_t *, int *);
 int td_get_parent_id(td_image_t *, td_disk_id_t *);
 int td_validate_parent(td_image_t *, td_image_t *);
 

drivers/tapdisk-vbd.c

@@ -538,6 +538,31 @@ tapdisk_vbd_add_dirty_log(td_vbd_t *vbd)
 	return err;
 }
 
+int
+tapdisk_vbd_update_o_direct(td_vbd_t *vbd)
+{
+	td_image_t *image, *next;
+	int no_o_direct = 0, oflags, err;
+
+	tapdisk_vbd_for_each_image(vbd, image, next){
+		err = td_get_oflags(image, &oflags);
+		if (err == -ENOTSUP)
+			continue;
+		if (err < 0)
+			return err;
+		if (!(oflags & O_DIRECT)){
+			no_o_direct = 1;
+			break;
+		}
+	}
+
+	td_flag_clear(vbd->flags, TD_OPEN_NO_O_DIRECT);
+	if (no_o_direct)
+		td_flag_set(vbd->flags, TD_OPEN_NO_O_DIRECT);
+
+	return 0;
+}
+
 int
 tapdisk_vbd_open_vdi(td_vbd_t *vbd, const char *name, td_flag_t flags, int prt_devnum)
 {
@@ -601,6 +626,10 @@ tapdisk_vbd_open_vdi(td_vbd_t *vbd, const char *name, td_flag_t flags, int prt_d
 		}
 	}
 
+    err = tapdisk_vbd_update_o_direct(vbd);
+    if (err)
+        goto fail;
+
     err = vbd_stats_create(vbd);
     if (err)
         goto fail;

drivers/tapdisk.h

@@ -182,6 +182,7 @@ struct tap_disk {
 	int                          private_data_size;
 	int (*td_open)               (td_driver_t *, const char *, td_flag_t);
 	int (*td_close)              (td_driver_t *);
+	int (*td_get_oflags)         (td_driver_t *, int *);
 	int (*td_get_parent_id)      (td_driver_t *, td_disk_id_t *);
 	int (*td_validate_parent)    (td_driver_t *, td_driver_t *, td_flag_t);
 	void (*td_queue_read)        (td_driver_t *, td_request_t);