block/iscsi: add support for request timeouts

libiscsi starting with 1.15 will properly support timeout of iscsi
commands. The default will remain no timeout, but this can
be changed via cmdline parameters, e.g.:

qemu -iscsi timeout=30 -drive file=iscsi://...

If a timeout occurs a reconnect is scheduled and the timed out command
will be requeued for processing after a successful reconnect.

The required API call iscsi_set_timeout is present since libiscsi
1.10 which was released in October 2013. However, due to some bugs
in the libiscsi code the use is not recommended before version 1.15.

Please note that this patch bumps the libiscsi requirement to 1.10
to have all function and macros defined. The patch fixes also a
off-by-one error in the NOP timeout calculation which was fixed
while touching these code parts.

Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1434455107-19328-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/qemu-options.hx b/qemu-options.hx
index e6e3895..0bdd59f 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2294,6 +2294,9 @@ By default qemu will use the iSCSI initiator-name
 'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from the command
 line or a configuration file.
 
+Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to detect
+stalled requests and force a reestablishment of the session. The timeout
+is specified in seconds. The default is 0 which means no timeout.
 
 Example (without authentication):
 @example
@@ -2321,6 +2324,7 @@ DEF("iscsi", HAS_ARG, QEMU_OPTION_iscsi,
     "-iscsi [user=user][,password=password]\n"
     "       [,header-digest=CRC32C|CR32C-NONE|NONE-CRC32C|NONE\n"
     "       [,initiator-name=initiator-iqn][,id=target-iqn]\n"
+    "       [,timeout=timeout]\n"
     "                iSCSI session parameters\n", QEMU_ARCH_ALL)
 STEXI