[PATCH v7 18/22] scsi: sd: Have scsi-ml retry read_capacity_10 errors

[Mike Christie <michael.christie@oracle.com>]

This has read_capacity_10 have scsi-ml retry errors instead of driving
them itself.

There are two behavior changes:
1. We no longer retry when scsi_execute_cmd returns < 0, but we should be
ok. We don't need to retry for failures like the queue being removed, and
for the case where there are no tags/reqs the block layer waits/retries
for us. For possible memory allocation failures from blk_rq_map_kern we
use GFP_NOIO, so retrying will probably not help.
2. For device reset UAs, we would retry READ_CAPACITY_RETRIES_ON_RESET
times, then once those are used up we would hit the main do loops retry
counter and get 3 more retries. We now only get
READ_CAPACITY_RETRIES_ON_RESET retries.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 drivers/scsi/sd.c | 64 +++++++++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 25 deletions(-)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index ba1970283966..8fe97a9f8a4f 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2447,42 +2447,56 @@ static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
 static int read_capacity_10(struct scsi_disk *sdkp, struct scsi_device *sdp,
 						unsigned char *buffer)
 {
-	unsigned char cmd[16];
+	static const u8 cmd[10] = { READ_CAPACITY };
 	struct scsi_sense_hdr sshdr;
+	struct scsi_failure failures[] = {
+		/* Fail immediately for Medium Not Present */
+		{
+			.sense = UNIT_ATTENTION,
+			.asc = 0x3A,
+			.ascq = 0x0,
+			.allowed = 0,
+			.result = SAM_STAT_CHECK_CONDITION,
+		},
+		{
+			.sense = NOT_READY,
+			.asc = 0x3A,
+			.ascq = 0x0,
+			.allowed = 0,
+			.result = SAM_STAT_CHECK_CONDITION,
+		},
+		{
+			.sense = UNIT_ATTENTION,
+			.asc = 0x29,
+			.ascq = 0,
+			/* Device reset might occur several times */
+			.allowed = READ_CAPACITY_RETRIES_ON_RESET,
+			.result = SAM_STAT_CHECK_CONDITION,
+		},
+		/* Any other error not listed above retry */
+		{
+			.result = SCMD_FAILURE_RESULT_ANY,
+			.allowed = 3,
+		},
+		{},
+	};
 	const struct scsi_exec_args exec_args = {
 		.sshdr = &sshdr,
+		.failures = failures,
 	};
 	int sense_valid = 0;
 	int the_result;
-	int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
 	sector_t lba;
 	unsigned sector_size;
 
-	do {
-		cmd[0] = READ_CAPACITY;
-		memset(&cmd[1], 0, 9);
-		memset(buffer, 0, 8);
-
-		the_result = scsi_execute_cmd(sdp, cmd, REQ_OP_DRV_IN, buffer,
-					      8, SD_TIMEOUT, sdkp->max_retries,
-					      &exec_args);
+	memset(buffer, 0, 8);
 
-		if (media_not_present(sdkp, &sshdr))
-			return -ENODEV;
-
-		if (the_result > 0) {
-			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--;
+	the_result = scsi_execute_cmd(sdp, cmd, REQ_OP_DRV_IN, buffer,
+				      8, SD_TIMEOUT, sdkp->max_retries,
+				      &exec_args);
 
-	} while (the_result && retries);
+	if (media_not_present(sdkp, &sshdr))
+		return -ENODEV;
 
 	if (the_result) {
 		sd_print_result(sdkp, "Read Capacity(10) failed", the_result);
-- 
2.25.1