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dataplane: replace iothread object_add() with embedded instance 

Before IOThread was its own object, each virtio-blk device would create
its own internal thread.  We need to preserve this behavior for
backwards compatibility when users do not specify -device
virtio-blk-pci,iothread=<id>.

This patch changes how the internal IOThread object is created.
Previously we used the monitor object_add() function, which is really a
layering violation.  The problem is that this needs to assign a name but
we don't have a name for this internal object.

Generating names for internal objects is a pain but even worse is that
they may collide with user-defined names.

Paolo Bonzini <pbonzini@redhat.com> suggested that the internal IOThread
object should not be named.  This way the conflict cannot happen and we
no longer need object_add().

One gotcha is that internal IOThread objects will not be listed by the
query-iothreads command since they are not named.  This is okay though
because query-iothreads is new and the internal IOThread is just for
backwards compatibility.  New users should explicitly define IOThread
objects.

Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-03-20 15:06:32 +01:00 committed by Kevin Wolf
parent 8c2664d869
commit 54bee5c2b4
1 changed files with 12 additions and 19 deletions
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31
hw/block/dataplane/virtio-blk.c
View File

@ -23,7 +23,7 @@
#include "virtio-blk.h"
#include "block/aio.h"
#include "hw/virtio/virtio-bus.h"
#include "monitor/monitor.h" /* for object_add() */
#include "qom/object_interfaces.h"
enum {
SEG_MAX = 126, /* maximum number of I/O segments */
@ -59,7 +59,7 @@ struct VirtIOBlockDataPlane {
* use it).
*/
IOThread *iothread;
bool internal_iothread;
IOThread internal_iothread_obj;
AioContext *ctx;
EventNotifier io_notifier; /* Linux AIO completion */
EventNotifier host_notifier; /* doorbell */
@ -391,23 +391,19 @@ void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
s->blk = blk;
if (blk->iothread) {
s->internal_iothread = false;
s->iothread = blk->iothread;
object_ref(OBJECT(s->iothread));
} else {
/* Create per-device IOThread if none specified */
Error *local_err = NULL;
s->internal_iothread = true;
object_add(TYPE_IOTHREAD, vdev->name, NULL, NULL, &local_err);
if (error_is_set(&local_err)) {
error_propagate(errp, local_err);
g_free(s);
return;
}
s->iothread = iothread_find(vdev->name);
assert(s->iothread);
/* Create per-device IOThread if none specified. This is for
* x-data-plane option compatibility. If x-data-plane is removed we
* can drop this.
*/
object_initialize(&s->internal_iothread_obj,
sizeof(s->internal_iothread_obj),
TYPE_IOTHREAD);
user_creatable_complete(OBJECT(&s->internal_iothread_obj), &error_abort);
s->iothread = &s->internal_iothread_obj;
}
object_ref(OBJECT(s->iothread));
s->ctx = iothread_get_aio_context(s->iothread);
/* Prevent block operations that conflict with data plane thread */
@ -426,9 +422,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
virtio_blk_data_plane_stop(s);
bdrv_set_in_use(s->blk->conf.bs, 0);
object_unref(OBJECT(s->iothread));
if (s->internal_iothread) {
object_unparent(OBJECT(s->iothread));
}
g_free(s);
}