block: Keep track of devices' I/O status

This commit adds support to the BlockDriverState type to keep track
of devices' I/O status.

There are three possible status: BDRV_IOS_OK (no error), BDRV_IOS_ENOSPC
(no space error) and BDRV_IOS_FAILED (any other error). The distinction
between no space and other errors is important because a management
application may want to watch for no space in order to extend the
space assigned to the VM and put it to run again.

Qemu devices supporting the I/O status feature have to enable it
explicitly by calling bdrv_iostatus_enable() _and_ have to be
configured to stop the VM on errors (ie. werror=stop|enospc or
rerror=stop).

In case of multiple errors being triggered in sequence only the first
one is stored. The I/O status is always reset to BDRV_IOS_OK when the
'cont' command is issued.

Next commits will add support to some devices and extend the
query-block/info block commands to return the I/O status information.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/block.h b/block.h
index 16bfa0a3d6..e77988e49c 100644
--- a/block.h
+++ b/block.h
@@ -77,6 +77,16 @@ typedef enum {
     BDRV_ACTION_REPORT, BDRV_ACTION_IGNORE, BDRV_ACTION_STOP
 } BlockMonEventAction;
 
+typedef enum {
+    BDRV_IOS_INVAL, BDRV_IOS_OK, BDRV_IOS_FAILED, BDRV_IOS_ENOSPC,
+    BDRV_IOS_MAX
+} BlockIOStatus;
+
+void bdrv_iostatus_enable(BlockDriverState *bs);
+void bdrv_iostatus_reset(BlockDriverState *bs);
+void bdrv_iostatus_disable(BlockDriverState *bs);
+bool bdrv_iostatus_is_enabled(const BlockDriverState *bs);
+void bdrv_iostatus_set_err(BlockDriverState *bs, int error);
 void bdrv_mon_event(const BlockDriverState *bdrv,
                     BlockMonEventAction action, int is_read);
 void bdrv_info_print(Monitor *mon, const QObject *data);