[dm-devel] [PATCH 2/3] libmultipath: alua: retry RTPG for NOT_READY and UNIT_ATTENTION

[Martin Wilck]

Use similar logic as the kernel for retrying ALUA commands to
avoid misinterpreting temporary failures as fatal errors.

Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 libmultipath/prioritizers/alua_rtpg.c | 59 +++++++++++++++++++++++----
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/libmultipath/prioritizers/alua_rtpg.c b/libmultipath/prioritizers/alua_rtpg.c
index ce405b55..34b5f3ce 100644
--- a/libmultipath/prioritizers/alua_rtpg.c
+++ b/libmultipath/prioritizers/alua_rtpg.c
@@ -69,10 +69,20 @@ print_hex(unsigned char *p, unsigned long len)
 #define SCSI_COMMAND_TERMINATED 0x22
 #define SG_ERR_DRIVER_SENSE     0x08
 #define RECOVERED_ERROR 0x01
+#define NOT_READY 0x2
+#define UNIT_ATTENTION 0x6
+
+enum scsi_disposition {
+	SCSI_GOOD = 0,
+	SCSI_ERROR,
+	SCSI_RETRY,
+};
 
 static int
-scsi_error(struct sg_io_hdr *hdr)
+scsi_error(struct sg_io_hdr *hdr, int opcode)
 {
+	int sense_key, asc, ascq;
+
 	/* Treat SG_ERR here to get rid of sg_err.[ch] */
 	hdr->status &= 0x7e;
 
@@ -81,29 +91,44 @@ scsi_error(struct sg_io_hdr *hdr)
 		(hdr->host_status == 0)   &&
 		(hdr->driver_status == 0)
 	) {
-		return 0;
+		return SCSI_GOOD;
 	}
 
+	sense_key = asc = ascq = -1;
 	if (
 		(hdr->status == SCSI_CHECK_CONDITION)    ||
 		(hdr->status == SCSI_COMMAND_TERMINATED) ||
 		((hdr->driver_status & 0xf) == SG_ERR_DRIVER_SENSE)
 	) {
 		if (hdr->sbp && (hdr->sb_len_wr > 2)) {
-			int		sense_key;
 			unsigned char *	sense_buffer = hdr->sbp;
 
-			if (sense_buffer[0] & 0x2)
+			if (sense_buffer[0] & 0x2) {
 				sense_key = sense_buffer[1] & 0xf;
-			else
+				if (hdr->sb_len_wr > 3)
+					asc = sense_buffer[2];
+				if (hdr->sb_len_wr > 4)
+					ascq = sense_buffer[3];
+			} else {
 				sense_key = sense_buffer[2] & 0xf;
+				if (hdr->sb_len_wr > 13)
+					asc = sense_buffer[12];
+				if (hdr->sb_len_wr > 14)
+					ascq = sense_buffer[13];
+			}
 
 			if (sense_key == RECOVERED_ERROR)
-				return 0;
+				return SCSI_GOOD;
 		}
 	}
 
-	return 1;
+	PRINT_DEBUG("alua: SCSI error for command %02x: status %02x, sense %02x/%02x/%02x",
+		    opcode, hdr->status, sense_key, asc, ascq);
+
+	if (sense_key == UNIT_ATTENTION || sense_key == NOT_READY)
+		return SCSI_RETRY;
+	else
+		return SCSI_ERROR;
 }
 
 /*
@@ -116,7 +141,9 @@ do_inquiry(int fd, int evpd, unsigned int codepage,
 	struct inquiry_command	cmd;
 	struct sg_io_hdr	hdr;
 	unsigned char		sense[SENSE_BUFF_LEN];
+	int rc, retry_count = 3;
 
+retry:
 	memset(&cmd, 0, sizeof(cmd));
 	cmd.op = OPERATION_CODE_INQUIRY;
 	if (evpd) {
@@ -142,9 +169,15 @@ do_inquiry(int fd, int evpd, unsigned int codepage,
 		return -RTPG_INQUIRY_FAILED;
 	}
 
-	if (scsi_error(&hdr)) {
+	rc = scsi_error(&hdr, OPERATION_CODE_INQUIRY);
+	if (rc == SCSI_ERROR) {
 		PRINT_DEBUG("do_inquiry: SCSI error!");
 		return -RTPG_INQUIRY_FAILED;
+	} else if (rc == SCSI_RETRY) {
+		if (--retry_count >= 0)
+			goto retry;
+		PRINT_DEBUG("do_inquiry: retries exhausted!");
+		return -RTPG_INQUIRY_FAILED;
 	}
 	PRINT_HEX((unsigned char *) resp, resplen);
 
@@ -265,7 +298,9 @@ do_rtpg(int fd, void* resp, long resplen, unsigned int timeout)
 	struct rtpg_command	cmd;
 	struct sg_io_hdr	hdr;
 	unsigned char		sense[SENSE_BUFF_LEN];
+	int retry_count = 3, rc;
 
+retry:
 	memset(&cmd, 0, sizeof(cmd));
 	cmd.op			= OPERATION_CODE_RTPG;
 	rtpg_command_set_service_action(&cmd);
@@ -286,9 +321,15 @@ do_rtpg(int fd, void* resp, long resplen, unsigned int timeout)
 	if (ioctl(fd, SG_IO, &hdr) < 0)
 		return -RTPG_RTPG_FAILED;
 
-	if (scsi_error(&hdr)) {
+	rc = scsi_error(&hdr, OPERATION_CODE_RTPG);
+	if (rc == SCSI_ERROR) {
 		PRINT_DEBUG("do_rtpg: SCSI error!");
 		return -RTPG_RTPG_FAILED;
+	} else if (rc == SCSI_RETRY) {
+		if (--retry_count >= 0)
+			goto retry;
+		PRINT_DEBUG("do_rtpg: retries exhausted!");
+		return -RTPG_RTPG_FAILED;
 	}
 	PRINT_HEX(resp, resplen);
 
-- 
2.17.1