[SCSI] fix removable device inability to detect disk changes

On Tue, 12 Aug 2008 15:08:14 +0200
Giuliano Pochini <pochini@shiny.it> wrote:

> Fujitsu magneto-optical drive, Adaptec 29160 and
> Linux Jay 2.6.26 #7 SMP Sun Aug 10 18:34:22 CEST 2008 ppc 7455, altivec supported PowerMac3,6 GNU/Linux
>
> When I insert a disk and I mount it, scsi_test_unit_ready() is called and
> the do-while loop gets sshdr->sense_key == UNIT_ATTENTION in the first
> cycle and 0 in the second one. So the if below misses the UNIT_ATTENTION
> and sdev->changed = 1 is not executed. At this point bad things can
> happen... I'm not sure how to fix this. Any clue ?

The problem is essentially caused by us eating UNIT_ATTENTION
conditions in scsi_test_unit_ready().  Fix by updating the ->changed
flag when this happens if the media is removable.

[pochini@shiny.it: updates to tidy up patch]
Signed-off-by: Giuliano Pochini <pochini@shiny.it>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 10 insertions, 11 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e5a9526d2037..f35a0951e469 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2105,22 +2105,21 @@ scsi_test_unit_ready(struct scsi_device *sdev, int timeout, int 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 (sdev->removable && scsi_sense_valid(sshdr) &&
+                    sshdr->sense_key == UNIT_ATTENTION)
+                        sdev->changed = 1;
+        } while (scsi_sense_valid(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))) {
-                        sdev->changed = 1;
-                        result = 0;
-                }
+        if (sdev->removable && scsi_sense_valid(sshdr) &&
+            (sshdr->sense_key == UNIT_ATTENTION ||
+             sshdr->sense_key == NOT_READY)) {
+                sdev->changed = 1;
+                result = 0;
         }
         if (!sshdr_external)
                 kfree(sshdr);