From d5e26bb1d812ba74f29b6bcbc88c3dbfb3eed824 Mon Sep 17 00:00:00 2001 From: "Matthew R. Ochs" Date: Mon, 14 Dec 2015 14:55:44 -0600 Subject: cxlflash: Fix to avoid virtual LUN failover failure 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 Reviewed-by: Uma Krishnan Signed-off-by: Martin K. Petersen --- include/uapi/scsi/cxlflash_ioctl.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/uapi/scsi/cxlflash_ioctl.h') diff --git a/include/uapi/scsi/cxlflash_ioctl.h b/include/uapi/scsi/cxlflash_ioctl.h index 831351b2e660..2302f3ce5f86 100644 --- a/include/uapi/scsi/cxlflash_ioctl.h +++ b/include/uapi/scsi/cxlflash_ioctl.h @@ -30,6 +30,16 @@ struct dk_cxlflash_hdr { __u64 return_flags; /* Returned flags */ }; +/* + * 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: * ----- -- cgit v1.2.3