[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>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e5a9526..f35a095 100644 (file)
--- 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);