On 09/02/15 07:31, Brian King wrote:
This patch fixes an issue seen with an IBM 2145 (SVC) where, following an error injection test which results in paths going offline, when they came back online, the path would timeout the REPORT_LUNS issued during the scan. This timeout situation continued until retries were expired, resulting in falling back to a sequential LUN scan. Then, since the target responds with PQ=1, PDT=0 for all possible LUNs, due to the way the sequential LUN scan code works, we end up adding 512 LUNs for each target, when there is really only a small handful of LUNs that are actually present. This patch doubles the timeout used on the REPORT_LUNS for each retry after a timeout is seen on a REPORT_LUNS. This patch solves the issue of 512 non existent LUNs showing up after this event. Running the test with this patch still showed that we were regularly hitting two timeouts, but the third, and final, REPORT_LUNS was always successful. Signed-off-by: Brian King <[email protected]> --- drivers/scsi/scsi_scan.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff -puN drivers/scsi/scsi_scan.c~scsi_report_luns_timeout_escalate drivers/scsi/scsi_scan.c --- linux/drivers/scsi/scsi_scan.c~scsi_report_luns_timeout_escalate 2015-09-02 08:49:07.268243497 -0500 +++ linux-bjking1/drivers/scsi/scsi_scan.c 2015-09-02 08:49:07.272243461 -0500 @@ -1304,6 +1304,7 @@ static int scsi_report_lun_scan(struct s struct scsi_device *sdev; struct Scsi_Host *shost = dev_to_shost(&starget->dev); int ret = 0; + int timeout = SCSI_TIMEOUT + 4 * HZ; /* * Only support SCSI-3 and up devices if BLIST_NOREPORTLUN is not set. @@ -1383,7 +1384,7 @@ retry: result = scsi_execute_req(sdev, scsi_cmd, DMA_FROM_DEVICE, lun_data, length, &sshdr, - SCSI_TIMEOUT + 4 * HZ, 3, NULL); + timeout, 3, NULL); SCSI_LOG_SCAN_BUS(3, sdev_printk (KERN_INFO, sdev, "scsi scan: REPORT LUNS" @@ -1392,6 +1393,8 @@ retry: retries, result)); if (result == 0) break; + else if (host_byte(result) == DID_TIME_OUT) + timeout = timeout * 2; else if (scsi_sense_valid(&sshdr)) { if (sshdr.sense_key != UNIT_ATTENTION) break;
This is somewhat of a hack, but anyway: Reviewed-by: Bart Van Assche <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
