cdrom, scsi: sr: propagate read-only status to block layer via set_disk_ro()

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))

drivers/scsi/sr.c

@@ -395,7 +395,7 @@ static blk_status_t sr_init_command(struct scsi_cmnd *SCpnt)
 
 	switch (req_op(rq)) {
 	case REQ_OP_WRITE:
-		if (!cd->writeable)
+		if (get_disk_ro(cd->disk))
 			goto out;
 		SCpnt->cmnd[0] = WRITE_10;
 		cd->cdi.media_written = 1;
@@ -681,6 +681,7 @@ static int sr_probe(struct scsi_device *sdev)
 	error = -ENOMEM;
 	if (get_capabilities(cd))
 		goto fail_minor;
+	cdrom_probe_write_features(&cd->cdi);
 	sr_vendor_init(cd);
 
 	set_capacity(disk, cd->capacity);
@@ -899,14 +900,6 @@ static int get_capabilities(struct scsi_cd *cd)
 	/*else    I don't think it can close its tray
 		cd->cdi.mask |= CDC_CLOSE_TRAY; */
 
-	/*
-	 * if DVD-RAM, MRW-W or CD-RW, we are randomly writable
-	 */
-	if ((cd->cdi.mask & (CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW)) !=
-			(CDC_DVD_RAM | CDC_MRW_W | CDC_RAM | CDC_CD_RW)) {
-		cd->writeable = 1;
-	}
-
 	kfree(buffer);
 	return 0;
 }

drivers/scsi/sr.h

@@ -35,7 +35,6 @@ typedef struct scsi_cd {
 	struct scsi_device *device;
 	unsigned int vendor;	/* vendor code, see sr_vendor.c         */
 	unsigned long ms_offset;	/* for reading multisession-CD's        */
-	unsigned writeable : 1;
 	unsigned use:1;		/* is this device still supportable     */
 	unsigned xa_flag:1;	/* CD has XA sectors ? */
 	unsigned readcd_known:1;	/* drive supports READ_CD (0xbe) */

include/linux/cdrom.h

@@ -108,6 +108,7 @@ int cdrom_ioctl(struct cdrom_device_info *cdi, struct block_device *bdev,
 extern unsigned int cdrom_check_events(struct cdrom_device_info *cdi,
 				       unsigned int clearing);
 
+extern void cdrom_probe_write_features(struct cdrom_device_info *cdi);
 extern int register_cdrom(struct gendisk *disk, struct cdrom_device_info *cdi);
 extern void unregister_cdrom(struct cdrom_device_info *cdi);