block: remove AioContext locking

This is the big patch that removes
aio_context_acquire()/aio_context_release() from the block layer and
affected block layer users.

There isn't a clean way to split this patch and the reviewers are likely
the same group of people, so I decided to do it in one patch.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Message-ID: <20231205182011.1976568-7-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

3 files changed, 2 insertions, 38 deletions

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index f83bb0f116..7bbbd981ad 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -124,7 +124,6 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
     VirtIOBlockDataPlane *s = vblk->dataplane;
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
-    AioContext *old_context;
     unsigned i;
     unsigned nvqs = s->conf->num_queues;
     Error *local_err = NULL;
@@ -178,10 +177,7 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
 
     trace_virtio_blk_data_plane_start(s);
 
-    old_context = blk_get_aio_context(s->conf->conf.blk);
-    aio_context_acquire(old_context);
     r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
-    aio_context_release(old_context);
     if (r < 0) {
         error_report_err(local_err);
         goto fail_aio_context;
@@ -208,13 +204,11 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
 
     /* Get this show started by hooking up our callbacks */
     if (!blk_in_drain(s->conf->conf.blk)) {
-        aio_context_acquire(s->ctx);
         for (i = 0; i < nvqs; i++) {
             VirtQueue *vq = virtio_get_queue(s->vdev, i);
 
             virtio_queue_aio_attach_host_notifier(vq, s->ctx);
         }
-        aio_context_release(s->ctx);
     }
     return 0;
 
@@ -314,8 +308,6 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev)
      */
     vblk->dataplane_started = false;
 
-    aio_context_acquire(s->ctx);
-
     /* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
     blk_drain(s->conf->conf.blk);
 
@@ -325,8 +317,6 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev)
      */
     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context(), NULL);
 
-    aio_context_release(s->ctx);
-
     /* Clean up guest notifier (irq) */
     k->set_guest_notifiers(qbus->parent, nvqs, false);
 
diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c
index c4bb28c66f..98501e6885 100644
--- a/hw/block/dataplane/xen-block.c
+++ b/hw/block/dataplane/xen-block.c
@@ -260,8 +260,6 @@ static void xen_block_complete_aio(void *opaque, int ret)
     XenBlockRequest *request = opaque;
     XenBlockDataPlane *dataplane = request->dataplane;
 
-    aio_context_acquire(dataplane->ctx);
-
     if (ret != 0) {
         error_report("%s I/O error",
                      request->req.operation == BLKIF_OP_READ ?
@@ -273,10 +271,10 @@ static void xen_block_complete_aio(void *opaque, int ret)
     if (request->presync) {
         request->presync = 0;
         xen_block_do_aio(request);
-        goto done;
+        return;
     }
     if (request->aio_inflight > 0) {
-        goto done;
+        return;
     }
 
     switch (request->req.operation) {
@@ -318,9 +316,6 @@ static void xen_block_complete_aio(void *opaque, int ret)
     if (dataplane->more_work) {
         qemu_bh_schedule(dataplane->bh);
     }
-
-done:
-    aio_context_release(dataplane->ctx);
 }
 
 static bool xen_block_split_discard(XenBlockRequest *request,
@@ -601,9 +596,7 @@ static void xen_block_dataplane_bh(void *opaque)
 {
     XenBlockDataPlane *dataplane = opaque;
 
-    aio_context_acquire(dataplane->ctx);
     xen_block_handle_requests(dataplane);
-    aio_context_release(dataplane->ctx);
 }
 
 static bool xen_block_dataplane_event(void *opaque)
@@ -703,10 +696,8 @@ void xen_block_dataplane_stop(XenBlockDataPlane *dataplane)
         xen_block_dataplane_detach(dataplane);
     }
 
-    aio_context_acquire(dataplane->ctx);
     /* Xen doesn't have multiple users for nodes, so this can't fail */
     blk_set_aio_context(dataplane->blk, qemu_get_aio_context(), &error_abort);
-    aio_context_release(dataplane->ctx);
 
     /*
      * Now that the context has been moved onto the main thread, cancel
@@ -752,7 +743,6 @@ void xen_block_dataplane_start(XenBlockDataPlane *dataplane,
 {
     ERRP_GUARD();
     XenDevice *xendev = dataplane->xendev;
-    AioContext *old_context;
     unsigned int ring_size;
     unsigned int i;
 
@@ -836,11 +826,8 @@ void xen_block_dataplane_start(XenBlockDataPlane *dataplane,
         goto stop;
     }
 
-    old_context = blk_get_aio_context(dataplane->blk);
-    aio_context_acquire(old_context);
     /* If other users keep the BlockBackend in the iothread, that's ok */
     blk_set_aio_context(dataplane->blk, dataplane->ctx, NULL);
-    aio_context_release(old_context);
 
     if (!blk_in_drain(dataplane->blk)) {
         xen_block_dataplane_attach(dataplane);
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index e110f9718b..ec9ed09a6a 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -1210,17 +1210,13 @@ static void virtio_blk_dma_restart_cb(void *opaque, bool running,
 static void virtio_blk_reset(VirtIODevice *vdev)
 {
     VirtIOBlock *s = VIRTIO_BLK(vdev);
-    AioContext *ctx;
     VirtIOBlockReq *req;
 
     /* Dataplane has stopped... */
     assert(!s->dataplane_started);
 
     /* ...but requests may still be in flight. */
-    ctx = blk_get_aio_context(s->blk);
-    aio_context_acquire(ctx);
     blk_drain(s->blk);
-    aio_context_release(ctx);
 
     /* We drop queued requests after blk_drain() because blk_drain() itself can
      * produce them. */
@@ -1250,10 +1246,6 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     uint64_t capacity;
     int64_t length;
     int blk_size = conf->logical_block_size;
-    AioContext *ctx;
-
-    ctx = blk_get_aio_context(s->blk);
-    aio_context_acquire(ctx);
 
     blk_get_geometry(s->blk, &capacity);
     memset(&blkcfg, 0, sizeof(blkcfg));
@@ -1277,7 +1269,6 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
      * per track (cylinder).
      */
     length = blk_getlength(s->blk);
-    aio_context_release(ctx);
     if (length > 0 && length / conf->heads / conf->secs % blk_size) {
         blkcfg.geometry.sectors = conf->secs & ~s->sector_mask;
     } else {
@@ -1344,9 +1335,7 @@ static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
 
     memcpy(&blkcfg, config, s->config_size);
 
-    aio_context_acquire(blk_get_aio_context(s->blk));
     blk_set_enable_write_cache(s->blk, blkcfg.wce != 0);
-    aio_context_release(blk_get_aio_context(s->blk));
 }
 
 static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features,
@@ -1414,11 +1403,9 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
      * s->blk would erroneously be placed in writethrough mode.
      */
     if (!virtio_vdev_has_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE)) {
-        aio_context_acquire(blk_get_aio_context(s->blk));
         blk_set_enable_write_cache(s->blk,
                                    virtio_vdev_has_feature(vdev,
                                                            VIRTIO_BLK_F_WCE));
-        aio_context_release(blk_get_aio_context(s->blk));
     }
 }