From f7959239dcc411b050db4b5560d7349df7f8f848 Mon Sep 17 00:00:00 2001
Message-Id: <f7959239dcc411b050db4b5560d7349df7f8f848@dist-git>
From: Eric Blake <eblake@redhat.com>
Date: Fri, 3 Oct 2014 08:46:25 -0600
Subject: [PATCH] qemu: support nospace reason in io error event

Aeons ago (commit 34dcbbb4, v0.8.2), we added a new libvirt event
(VIR_DOMAIN_EVENT_ID_IO_ERROR_REASON) in order to tell the user WHY
the guest halted.  This is because at least VDSM wants to react
differently to ENOSPC events (resize the lvm partition to be larger,
and resume the guest as if nothing had happened) from all other events
(I/O is hosed, throw up our hands and flag things as broken).  At the
time this was done, downstream RHEL qemu added a vendor extension
'__com.redhat_reason', which would be exactly one of these strings:
"enospc", "eperm", "eio", and "eother".  In our stupidity, we exposed
those exact strings to clients, rather than an enum, and we also
return "" if we did not have access to a reason (which was the case
for upstream qemu).

Fast forward to now: upstream qemu commit c7c2ff0c (will be qemu 2.2)
FINALLY adds a 'nospace' boolean, after discussion with multiple
projects determined that VDSM really doesn't care about distinction
between any other error types.  So this patch converts 'nospace' into
the string "enospc" for compatibility with RHEL clients that were
already used to the downstream extension, while leaving the reason
blank for all other cases (no change from the status quo).

See also https://bugzilla.redhat.com/show_bug.cgi?id=1119784

* src/qemu/qemu_monitor_json.c (qewmuMonitorJSONHandleIOError):
Parse reason field from modern qemu.
* include/libvirt/libvirt.h.in
(virConnectDomainEventIOErrorReasonCallback): Document it.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit e9392e48d4e3b29809da7883b697d5caf3a09680)
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>

Conflicts:
	src/qemu/qemu_monitor_json.c -- RHEL-only addition of
        __com.redhat_reason

This backport removes the RHEL-only __com.redhat_reason to make the code
match upstream. The next patch will add the RHEL-only reason back. This
is to make future rebases easier. We won't have to rework this once
again, we can just drop the old RHEL-only patch and this backport and
only keep the new RHEL-only patch.
---
 include/libvirt/libvirt.h.in |  6 ++++++
 src/qemu/qemu_monitor_json.c | 12 ++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 60b3e0b..3ca935e 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -4853,6 +4853,12 @@ typedef void (*virConnectDomainEventIOErrorCallback)(virConnectPtr conn,
  * The callback signature to use when registering for an event of type
  * VIR_DOMAIN_EVENT_ID_IO_ERROR_REASON with virConnectDomainEventRegisterAny()
  *
+ * If the I/O error is known to be caused by an ENOSPC condition in
+ * the host (where resizing the disk to be larger will allow the guest
+ * to be resumed as if nothing happened), @reason will be "enospc".
+ * Otherwise, @reason will be "", although future strings may be added
+ * if determination of other error types becomes possible.
+ *
  */
 typedef void (*virConnectDomainEventIOErrorReasonCallback)(virConnectPtr conn,
                                                            virDomainPtr dom,
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index adf560a..7dcea2e 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -717,11 +717,13 @@ VIR_ENUM_IMPL(qemuMonitorIOErrorAction, VIR_DOMAIN_EVENT_IO_ERROR_LAST,
               "ignore", "stop", "report");
 
 
-static void qemuMonitorJSONHandleIOError(qemuMonitorPtr mon, virJSONValuePtr data)
+static void
+qemuMonitorJSONHandleIOError(qemuMonitorPtr mon, virJSONValuePtr data)
 {
     const char *device;
     const char *action;
-    const char *reason;
+    const char *reason = "";
+    bool nospc = false;
     int actionID;
 
     /* Throughout here we try our best to carry on upon errors,
@@ -737,10 +739,8 @@ static void qemuMonitorJSONHandleIOError(qemuMonitorPtr mon, virJSONValuePtr dat
         VIR_WARN("missing device in disk io error event");
     }
 
-    if ((reason = virJSONValueObjectGetString(data, "__com.redhat_reason")) == NULL) {
-        VIR_WARN("missing __com.redhat_reason in disk io error event");
-        reason = "";
-    }
+    if (virJSONValueObjectGetBoolean(data, "nospace", &nospc) == 0 && nospc)
+        reason = "enospc";
 
     if ((actionID = qemuMonitorIOErrorActionTypeFromString(action)) < 0) {
         VIR_WARN("unknown disk io error action '%s'", action);
-- 
2.1.3