1 files changed, 48 insertions, 25 deletions

diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
index fc049612d6dc..62934cf4b10d 100644
--- a/drivers/cdrom/cdrom.c
+++ b/drivers/cdrom/cdrom.c
@@ -631,6 +631,16 @@ int register_cdrom(struct gendisk *disk, struct cdrom_device_info *cdi)
 
 	WARN_ON(!cdo->generic_packet);
 
+	/*
+	 * Propagate the drive's write support to the block layer so BLKROGET
+	 * reflects actual write capability. Drivers that use GET CONFIGURATION
+	 * features (CDC_MRW_W, CDC_RAM) must have called
+	 * cdrom_probe_write_features() before register_cdrom() so the mask is
+	 * complete here.
+	 */
+	set_disk_ro(disk, !CDROM_CAN(CDC_DVD_RAM | CDC_MRW_W | CDC_RAM |
+				     CDC_CD_RW));
+
 	cd_dbg(CD_REG_UNREG, "drive \"/dev/%s\" registered\n", cdi->name);
 	mutex_lock(&cdrom_mutex);
 	list_add(&cdi->list, &cdrom_list);
@@ -742,6 +752,44 @@ static int cdrom_is_random_writable(struct cdrom_device_info *cdi, int *write)
 	return 0;
 }
 
+/*
+ * Probe write-related MMC features via GET CONFIGURATION and update
+ * cdi->mask accordingly. Drivers that populate cdi->mask from the MODE SENSE
+ * capabilities page (e.g. sr) should call this after those MODE SENSE bits
+ * have been set but before register_cdrom(), so that the full set of
+ * write-capability bits is known by the time register_cdrom() decides on the
+ * initial read-only state of the disk.
+ */
+void cdrom_probe_write_features(struct cdrom_device_info *cdi)
+{
+	int mrw, mrw_write, ram_write;
+
+	mrw = 0;
+	if (!cdrom_is_mrw(cdi, &mrw_write))
+		mrw = 1;
+
+	if (CDROM_CAN(CDC_MO_DRIVE))
+		ram_write = 1;
+	else
+		(void) cdrom_is_random_writable(cdi, &ram_write);
+
+	if (mrw)
+		cdi->mask &= ~CDC_MRW;
+	else
+		cdi->mask |= CDC_MRW;
+
+	if (mrw_write)
+		cdi->mask &= ~CDC_MRW_W;
+	else
+		cdi->mask |= CDC_MRW_W;
+
+	if (ram_write)
+		cdi->mask &= ~CDC_RAM;
+	else
+		cdi->mask |= CDC_RAM;
+}
+EXPORT_SYMBOL(cdrom_probe_write_features);
+
 static int cdrom_media_erasable(struct cdrom_device_info *cdi)
 {
 	disc_information di;
@@ -894,33 +942,8 @@ static int cdrom_is_dvd_rw(struct cdrom_device_info *cdi)
  */
 static int cdrom_open_write(struct cdrom_device_info *cdi)
 {
-	int mrw, mrw_write, ram_write;
 	int ret = 1;
 
-	mrw = 0;
-	if (!cdrom_is_mrw(cdi, &mrw_write))
-		mrw = 1;
-
-	if (CDROM_CAN(CDC_MO_DRIVE))
-		ram_write = 1;
-	else
-		(void) cdrom_is_random_writable(cdi, &ram_write);
-	
-	if (mrw)
-		cdi->mask &= ~CDC_MRW;
-	else
-		cdi->mask |= CDC_MRW;
-
-	if (mrw_write)
-		cdi->mask &= ~CDC_MRW_W;
-	else
-		cdi->mask |= CDC_MRW_W;
-
-	if (ram_write)
-		cdi->mask &= ~CDC_RAM;
-	else
-		cdi->mask |= CDC_RAM;
-
 	if (CDROM_CAN(CDC_MRW_W))
 		ret = cdrom_mrw_open_write(cdi);
 	else if (CDROM_CAN(CDC_DVD_RAM))