[PATCH v2 2/2] sr: fix automatic tray loading for data reading

[Thomas Schmitt]

If
  open("/dev/sr0", O_RDONLY);
pulls in the tray of an optical drive, it immediately returns -1 with
errno ENOMEDIUM or the first read(2) fails with EIO. Later, when the drive
has stopped blinking, another open() yields success and read() works.
This affects not only userland reading of the device file but also
mounting the device.
The reason is that medium assessment happens before automatic tray
loading.

Use the new function cdrom_handle_open_tray() for deciding and performing
tray loading before doing medium assessment.

Signed-off-by: Thomas Schmitt <scdbackup@xxxxxxx>
---
 drivers/scsi/sr.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index 2b43c0f97442..1c3806f59865 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -540,12 +540,18 @@ static int sr_block_open(struct block_device *bdev, fmode_t mode)

 	sdev = cd->device;
 	scsi_autopm_get_device(sdev);
-	if (bdev_check_media_change(bdev))
-		sr_revalidate_disk(cd);

 	mutex_lock(&cd->lock);
-	ret = cdrom_open(&cd->cdi, bdev, mode);
+	ret = cdrom_handle_open_tray(&cd->cdi, mode, 0);
 	mutex_unlock(&cd->lock);
+	if (!ret) {
+		if (bdev_check_media_change(bdev))
+			sr_revalidate_disk(cd);
+
+		mutex_lock(&cd->lock);
+		ret = cdrom_open(&cd->cdi, bdev, mode);
+		mutex_unlock(&cd->lock);
+	}

 	scsi_autopm_put_device(sdev);
 	if (ret)
--
2.20.1