Is this anything to worry about? It appears to have shown up after the 
Windows system that has this target mounted rebooted and went to remount 
the disk at startup.

Jul 11 22:51:06 iscsi-target: pid 
1693:/usr/src/dist/iscsi/src/util.c:736: ***ERROR*** readv() failed: rc 
-1 errno 54
Jul 11 22:51:08 iscsi-target: > Discovery login from 
iqn.1991-05.com.microsoft:xxx on 8a7b:3cfc::1000:0
Jul 11 22:51:08 iscsi-target: < Discovery logout from 
iqn.1991-05.com.microsoft:xxx on 8a7b:3cfc::1000:0
Jul 11 22:51:09 iscsi-target: > Normal login from 
iqn.1991-05.com.microsoft:xxx on 8a7b:3cfc::1000:0