[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>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 7955bc2261256c27cda37bb4074880bd11893987..015a597a852ec5700edf1720cce349d5aeda40fb 100644 (file)
--- 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);