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authorMatthew R. Ochs <mrochs@linux.vnet.ibm.com>2015-12-14 14:55:44 -0600
committerMartin K. Petersen <martin.petersen@oracle.com>2016-01-06 20:50:08 -0500
commitd5e26bb1d812ba74f29b6bcbc88c3dbfb3eed824 (patch)
treed70e61530110d432830ce17d4a055327cc757b03 /include/uapi/scsi
parenta9be294ecb3b9dc82b15625631b153f871181d16 (diff)
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 <mrochs@linux.vnet.ibm.com> Acked-by: Manoj Kumar <manoj@linux.vnet.ibm.com> Reviewed-by: Uma Krishnan <ukrishn@linux.vnet.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'include/uapi/scsi')
-rw-r--r--include/uapi/scsi/cxlflash_ioctl.h10
1 files changed, 10 insertions, 0 deletions
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
@@ -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

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