scsi: fix TUR error handling in sr_media_change()

sr_test_unit_ready() returns 0 iff TUR succeeded - IOW, when media is
present and the device is actually ready, so the return value wouldn't
be zero when TUR ends with sense data. sr_media_change() incorrectly
tests (retval || (scsi_sense_valid(sshdr)...)) when it tries to test
whether TUR failed without sense data or with sense data indicating
media-not-present.

Fix the test using scsi_status_is_good() and update comments.

- Fixed a comment typo spotted by Eike.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rolf Eike Beer <eike-kernel@sf-tec.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/scsi/sr.c b/drivers/scsi/sr.c
index d7b383c96d5d..c7e29bdec2cd 100644
--- a/drivers/scsi/sr.c
+++ b/drivers/scsi/sr.c
@@ -214,13 +214,17 @@ static int sr_media_change(struct cdrom_device_info *cdi, int slot)
 
         sshdr =  kzalloc(sizeof(*sshdr), GFP_KERNEL);
         retval = sr_test_unit_ready(cd->device, sshdr);
-        if (retval || (scsi_sense_valid(sshdr) &&
-                       /* 0x3a is medium not present */
-                       sshdr->asc == 0x3a)) {
-                /* Media not present or unable to test, unit probably not
-                 * ready. This usually means there is no disc in the drive.
-                 * Mark as changed, and we will figure it out later once
-                 * the drive is available again.
+        /*
+         * Media is considered to be present if TUR succeeds or fails with
+         * sense data indicating something other than media-not-present
+         * (ASC 0x3a).
+         */
+        if (!scsi_status_is_good(retval) &&
+            (!scsi_sense_valid(sshdr) || sshdr->asc == 0x3a)) {
+                /*
+                 * Probably no media in the device.  Mark as changed, and
+                 * we will figure it out later once the drive is available
+                 * again.
                  */
                 cd->device->changed = 1;
                 /* This will force a flush, if called from check_disk_change */