ISCSI: Add support for thin-provisioning via discard/UNMAP and bigger LUNs

Update the configure test for libiscsi support to detect version 1.3
or later.  Version 1.3 of libiscsi provides both READCAPACITY16 as well
as UNMAP commands.

Update the iscsi block layer to use READCAPACITY16 to detect the size of
the LUN instead of READCAPACITY10. This allows support for LUNs larger
than 2TB.

Update to implement bdrv_aio_discard() using the UNMAP command.
This allows us to use thin-provisioned LUNs from TGTD and other iSCSI
targets that support thin-provisioning.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
[squashed in subsequent patch from Ronnie to fix off-by-one in LBA count]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/configure b/configure
index 0111774cb0..0e3615be07 100755
--- a/configure
+++ b/configure
@@ -2546,10 +2546,13 @@ fi
 
 ##########################################
 # Do we have libiscsi
+# We check for iscsi_unmap_sync() to make sure we have a
+# recent enough version of libiscsi.
 if test "$libiscsi" != "no" ; then
   cat > $TMPC << EOF
+#include <stdio.h>
 #include <iscsi/iscsi.h>
-int main(void) { iscsi_create_context(""); return 0; }
+int main(void) { iscsi_unmap_sync(NULL,0,0,0,NULL,0); return 0; }
 EOF
   if compile_prog "-Werror" "-liscsi" ; then
     libiscsi="yes"