From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian King Subject: [PATCH] SCSI: Scale up REPORT_LUNS timeout on failure Date: Wed, 02 Sep 2015 09:31:46 -0500 Message-ID: <55E70852.9050506@linux.vnet.ibm.com> References: <55D65082.6020504@linux.vnet.ibm.com> <55DDB8F3.3020308@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from e19.ny.us.ibm.com ([129.33.205.209]:34415 "EHLO e19.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754071AbbIBOb6 (ORCPT ); Wed, 2 Sep 2015 10:31:58 -0400 Received: from /spool/local by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 2 Sep 2015 10:31:58 -0400 Received: from b01cxnp23032.gho.pok.ibm.com (b01cxnp23032.gho.pok.ibm.com [9.57.198.27]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 2ABF738C8046 for ; Wed, 2 Sep 2015 10:31:56 -0400 (EDT) Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t82EVuhR49610764 for ; Wed, 2 Sep 2015 14:31:56 GMT Received: from d01av03.pok.ibm.com (localhost [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t82EVs3r018959 for ; Wed, 2 Sep 2015 10:31:55 -0400 In-Reply-To: <55DDB8F3.3020308@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi , James Bottomley Cc: Hannes Reinecke , Bart Van Assche 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 --- 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; _