[SCSI] sd,sr: add early detection of medium not present

The current scsi_test_unit_ready() is updated to return sense code
information (in struct scsi_sense_hdr).  The sd and sr drivers are
changed to interpret the sense code return asc 0x3a as no media and
adjust the device status accordingly.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 38 insertions, 8 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index aa17e718666e..db52222885b7 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1973,27 +1973,57 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 }
 EXPORT_SYMBOL(scsi_mode_sense);
 
+/**
+ *      scsi_test_unit_ready - test if unit is ready
+ *      @sdev:  scsi device to change the state of.
+ *      @timeout: command timeout
+ *      @retries: number of retries before failing
+ *      @sshdr_external: Optional pointer to struct scsi_sense_hdr for
+ *              returning sense. Make sure that this is cleared before passing
+ *              in.
+ *
+ *      Returns zero if unsuccessful or an error if TUR failed.  For
+ *      removable media, a return of NOT_READY or UNIT_ATTENTION is
+ *      translated to success, with the ->changed flag updated.
+ **/
 int
-scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries)
+scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int retries,
+                     struct scsi_sense_hdr *sshdr_external)
 {
         char cmd[] = {
                 TEST_UNIT_READY, 0, 0, 0, 0, 0,
         };
-        struct scsi_sense_hdr sshdr;
+        struct scsi_sense_hdr *sshdr;
         int result;
-        
-        result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, &sshdr,
-                                  timeout, retries);
+
+        if (!sshdr_external)
+                sshdr = kzalloc(sizeof(*sshdr), GFP_KERNEL);
+        else
+                sshdr = sshdr_external;
+
+        /* try to eat the UNIT_ATTENTION if there are enough retries */
+        do {
+                result = scsi_execute_req(sdev, cmd, DMA_NONE, NULL, 0, sshdr,
+                                          timeout, retries);
+        } while ((driver_byte(result) & DRIVER_SENSE) &&
+                 sshdr && sshdr->sense_key == UNIT_ATTENTION &&
+                 --retries);
+
+        if (!sshdr)
+                /* could not allocate sense buffer, so can't process it */
+                return result;
 
         if ((driver_byte(result) & DRIVER_SENSE) && sdev->removable) {
 
-                if ((scsi_sense_valid(&sshdr)) &&
-                    ((sshdr.sense_key == UNIT_ATTENTION) ||
-                     (sshdr.sense_key == NOT_READY))) {
+                if ((scsi_sense_valid(sshdr)) &&
+                    ((sshdr->sense_key == UNIT_ATTENTION) ||
+                     (sshdr->sense_key == NOT_READY))) {
                         sdev->changed = 1;
                         result = 0;
                 }
         }
+        if (!sshdr_external)
+                kfree(sshdr);
         return result;
 }
 EXPORT_SYMBOL(scsi_test_unit_ready);