[SCSI] sd: retry read_capacity on UNIT_ATTENTION

Hazard testing uncovered yet another bug in sd. Under heavy reset
activity the retry counter might be exhausted and the command will be
returned with sense UNIT_ATTENTION/0x29/00 (POWER ON, RESET, OR BUS
DEVICE RESET OCCURRED). In those cases we should just increase the
retry counter again, retrying one more to clear up this Unit Attention
state.

[jejb: update to work with RC16 devices and not to loop endlessly]
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 20 insertions, 3 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 7955bc226125..015a597a852e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -1433,6 +1433,8 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
 #error RC16_LEN must not be more than SD_BUF_SIZE
 #endif
 
+#define READ_CAPACITY_RETRIES_ON_RESET  10
+
 static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
                                                 unsigned char *buffer)
 {
@@ -1440,7 +1442,7 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
         struct scsi_sense_hdr sshdr;
         int sense_valid = 0;
         int the_result;
-        int retries = 3;
+        int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
         unsigned int alignment;
         unsigned long long lba;
         unsigned sector_size;
@@ -1469,6 +1471,13 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
                                  * Invalid Field in CDB, just retry
                                  * silently with RC10 */
                                 return -EINVAL;
+                        if (sense_valid &&
+                            sshdr.sense_key == UNIT_ATTENTION &&
+                            sshdr.asc == 0x29 && sshdr.ascq == 0x00)
+                                /* Device reset might occur several times,
+                                 * give it one more chance */
+                                if (--reset_retries > 0)
+                                        continue;
                 }
                 retries--;
 
@@ -1527,7 +1536,7 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
         struct scsi_sense_hdr sshdr;
         int sense_valid = 0;
         int the_result;
-        int retries = 3;
+        int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
         sector_t lba;
         unsigned sector_size;
 
@@ -1543,8 +1552,16 @@ static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
                 if (media_not_present(sdkp, &sshdr))
                         return -ENODEV;
 
-                if (the_result)
+                if (the_result) {
                         sense_valid = scsi_sense_valid(&sshdr);
+                        if (sense_valid &&
+                            sshdr.sense_key == UNIT_ATTENTION &&
+                            sshdr.asc == 0x29 && sshdr.ascq == 0x00)
+                                /* Device reset might occur several times,
+                                 * give it one more chance */
+                                if (--reset_retries > 0)
+                                        continue;
+                }
                 retries--;
 
         } while (the_result && retries);