[PATCH 3/4] virtio-blk: don't lock AioContext in the completion code path

[Stefan Hajnoczi <stefanha@redhat.com>]

Nothing in the completion code path relies on the AioContext lock
anymore. Virtqueues are only accessed from one thread at any moment and
the s->rq global state is protected by its own lock now.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/virtio-blk.c | 34 ++++------------------------------
 1 file changed, 4 insertions(+), 30 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index ee38e089bc..f5315df042 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -105,7 +105,6 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
     VirtIOBlock *s = next->dev;
     VirtIODevice *vdev = VIRTIO_DEVICE(s);
 
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     while (next) {
         VirtIOBlockReq *req = next;
         next = req->mr_next;
@@ -138,7 +137,6 @@ static void virtio_blk_rw_complete(void *opaque, int ret)
         block_acct_done(blk_get_stats(s->blk), &req->acct);
         virtio_blk_free_request(req);
     }
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
 }
 
 static void virtio_blk_flush_complete(void *opaque, int ret)
@@ -146,19 +144,13 @@ static void virtio_blk_flush_complete(void *opaque, int ret)
     VirtIOBlockReq *req = opaque;
     VirtIOBlock *s = req->dev;
 
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
-    if (ret) {
-        if (virtio_blk_handle_rw_error(req, -ret, 0, true)) {
-            goto out;
-        }
+    if (ret && virtio_blk_handle_rw_error(req, -ret, 0, true)) {
+        return;
     }
 
     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
     block_acct_done(blk_get_stats(s->blk), &req->acct);
     virtio_blk_free_request(req);
-
-out:
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
 }
 
 static void virtio_blk_discard_write_zeroes_complete(void *opaque, int ret)
@@ -168,11 +160,8 @@ static void virtio_blk_discard_write_zeroes_complete(void *opaque, int ret)
     bool is_write_zeroes = (virtio_ldl_p(VIRTIO_DEVICE(s), &req->out.type) &
                             ~VIRTIO_BLK_T_BARRIER) == VIRTIO_BLK_T_WRITE_ZEROES;
 
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
-    if (ret) {
-        if (virtio_blk_handle_rw_error(req, -ret, false, is_write_zeroes)) {
-            goto out;
-        }
+    if (ret && virtio_blk_handle_rw_error(req, -ret, false, is_write_zeroes)) {
+        return;
     }
 
     virtio_blk_req_complete(req, VIRTIO_BLK_S_OK);
@@ -180,9 +169,6 @@ static void virtio_blk_discard_write_zeroes_complete(void *opaque, int ret)
         block_acct_done(blk_get_stats(s->blk), &req->acct);
     }
     virtio_blk_free_request(req);
-
-out:
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
 }
 
 #ifdef __linux__
@@ -229,10 +215,8 @@ static void virtio_blk_ioctl_complete(void *opaque, int status)
     virtio_stl_p(vdev, &scsi->data_len, hdr->dxfer_len);
 
 out:
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     virtio_blk_req_complete(req, status);
     virtio_blk_free_request(req);
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
     g_free(ioctl_req);
 }
 
@@ -672,7 +656,6 @@ static void virtio_blk_zone_report_complete(void *opaque, int ret)
 {
     ZoneCmdData *data = opaque;
     VirtIOBlockReq *req = data->req;
-    VirtIOBlock *s = req->dev;
     VirtIODevice *vdev = VIRTIO_DEVICE(req->dev);
     struct iovec *in_iov = data->in_iov;
     unsigned in_num = data->in_num;
@@ -763,10 +746,8 @@ static void virtio_blk_zone_report_complete(void *opaque, int ret)
     }
 
 out:
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     virtio_blk_req_complete(req, err_status);
     virtio_blk_free_request(req);
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
     g_free(data->zone_report_data.zones);
     g_free(data);
 }
@@ -829,10 +810,8 @@ static void virtio_blk_zone_mgmt_complete(void *opaque, int ret)
         err_status = VIRTIO_BLK_S_ZONE_INVALID_CMD;
     }
 
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     virtio_blk_req_complete(req, err_status);
     virtio_blk_free_request(req);
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
 }
 
 static int virtio_blk_handle_zone_mgmt(VirtIOBlockReq *req, BlockZoneOp op)
@@ -882,7 +861,6 @@ static void virtio_blk_zone_append_complete(void *opaque, int ret)
 {
     ZoneCmdData *data = opaque;
     VirtIOBlockReq *req = data->req;
-    VirtIOBlock *s = req->dev;
     VirtIODevice *vdev = VIRTIO_DEVICE(req->dev);
     int64_t append_sector, n;
     uint8_t err_status = VIRTIO_BLK_S_OK;
@@ -905,10 +883,8 @@ static void virtio_blk_zone_append_complete(void *opaque, int ret)
     trace_virtio_blk_zone_append_complete(vdev, req, append_sector, ret);
 
 out:
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     virtio_blk_req_complete(req, err_status);
     virtio_blk_free_request(req);
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
     g_free(data);
 }
 
@@ -944,10 +920,8 @@ static int virtio_blk_handle_zone_append(VirtIOBlockReq *req,
     return 0;
 
 out:
-    aio_context_acquire(blk_get_aio_context(s->conf.conf.blk));
     virtio_blk_req_complete(req, err_status);
     virtio_blk_free_request(req);
-    aio_context_release(blk_get_aio_context(s->conf.conf.blk));
     return err_status;
 }
 
-- 
2.41.0