From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id A56431A029B for ; Tue, 15 Dec 2015 07:57:05 +1100 (AEDT) Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 14 Dec 2015 15:57:03 -0500 Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id B58D338C8051 for ; Mon, 14 Dec 2015 15:56:58 -0500 (EST) Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id tBEKuwlk30015730 for ; Mon, 14 Dec 2015 20:56:58 GMT Received: from d01av04.pok.ibm.com (localhost [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id tBEKuwwR024660 for ; Mon, 14 Dec 2015 15:56:58 -0500 From: Uma Krishnan To: linux-scsi@vger.kernel.org, James Bottomley , "Martin K. Petersen" , "Matthew R. Ochs" , "Manoj N. Kumar" , Brian King Cc: linuxppc-dev@lists.ozlabs.org, Ian Munsie , Andrew Donnellan , Daniel Axtens Subject: [PATCH v2 2/6] cxlflash: Fix to avoid virtual LUN failover failure Date: Mon, 14 Dec 2015 14:55:44 -0600 Message-Id: <1450126544-47592-2-git-send-email-ukrishn@linux.vnet.ibm.com> In-Reply-To: <1450126544-47592-1-git-send-email-ukrishn@linux.vnet.ibm.com> References: <1450126293-47440-1-git-send-email-ukrishn@linux.vnet.ibm.com> <1450126544-47592-1-git-send-email-ukrishn@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: "Matthew R. Ochs" Applications which use virtual LUN's that are backed by a physical LUN over both adapter ports may experience an I/O failure in the event of a link loss (e.g. cable pull). Virtual LUNs may be accessed through one or both ports of the adapter. This access is encoded in the translation entries that comprise the virtual LUN and used by the AFU for load-balancing I/O and handling failover scenarios. In a link loss scenario, even though the AFU is able to maintain connectivity to the LUN, it is up to the application to retry the failed I/O. When applications are unaware of the virtual LUN's underlying topology, they are unable to make a sound decision of when to retry an I/O and therefore are forced to make their reaction to a failed I/O absolute. The result is either a failure to retry I/O or increased latency for scenarios where a retry is pointless. To remedy this scenario, provide feedback back to the application on virtual LUN creation as to which ports the LUN may be accessed. LUN's spanning both ports are candidates for a retry in a presence of an I/O failure. Signed-off-by: Matthew R. Ochs Acked-by: Manoj Kumar --- drivers/scsi/cxlflash/vlun.c | 2 ++ include/uapi/scsi/cxlflash_ioctl.h | 10 ++++++++++ 2 files changed, 12 insertions(+) diff --git a/drivers/scsi/cxlflash/vlun.c b/drivers/scsi/cxlflash/vlun.c index a53f583..50f8e93 100644 --- a/drivers/scsi/cxlflash/vlun.c +++ b/drivers/scsi/cxlflash/vlun.c @@ -1008,6 +1008,8 @@ int cxlflash_disk_virtual_open(struct scsi_device *sdev, void *arg) virt->last_lba = last_lba; virt->rsrc_handle = rsrc_handle; + if (lli->port_sel == BOTH_PORTS) + virt->hdr.return_flags |= DK_CXLFLASH_ALL_PORTS_ACTIVE; out: if (likely(ctxi)) put_context(ctxi); diff --git a/include/uapi/scsi/cxlflash_ioctl.h b/include/uapi/scsi/cxlflash_ioctl.h index 831351b..2302f3c 100644 --- a/include/uapi/scsi/cxlflash_ioctl.h +++ b/include/uapi/scsi/cxlflash_ioctl.h @@ -31,6 +31,16 @@ struct dk_cxlflash_hdr { }; /* + * Return flag definitions available to all ioctls + * + * Similar to the input flags, these are grown from the bottom-up with the + * intention that ioctl-specific return flag definitions would grow from the + * top-down, allowing the two sets to co-exist. While not required/enforced + * at this time, this provides future flexibility. + */ +#define DK_CXLFLASH_ALL_PORTS_ACTIVE 0x0000000000000001ULL + +/* * Notes: * ----- * The 'context_id' field of all ioctl structures contains the context -- 2.1.0