[PATCH 3/5] vduse-blk: Don't delete the export until all inflight I/Os completed

[Xie Yongji]

Don't delete the export until all inflight I/Os completed.
Otherwise, it might lead to a use-after-free.

Fixes: cc241b5505b2 ("vduse-blk: Implement vduse-blk export")
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
---
 block/export/vduse-blk.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/block/export/vduse-blk.c b/block/export/vduse-blk.c
index c3a89894ae..251d73c841 100644
--- a/block/export/vduse-blk.c
+++ b/block/export/vduse-blk.c
@@ -31,6 +31,7 @@ typedef struct VduseBlkExport {
     VduseDev *dev;
     uint16_t num_queues;
     char *recon_file;
+    unsigned int inflight;
 } VduseBlkExport;
 
 typedef struct VduseBlkReq {
@@ -38,6 +39,18 @@ typedef struct VduseBlkReq {
     VduseVirtq *vq;
 } VduseBlkReq;
 
+static void vduse_blk_inflight_inc(VduseBlkExport *vblk_exp)
+{
+    vblk_exp->inflight++;
+}
+
+static void vduse_blk_inflight_dec(VduseBlkExport *vblk_exp)
+{
+    if (--vblk_exp->inflight == 0) {
+        aio_wait_kick();
+    }
+}
+
 static void vduse_blk_req_complete(VduseBlkReq *req, size_t in_len)
 {
     vduse_queue_push(req->vq, &req->elem, in_len);
@@ -68,10 +81,13 @@ static void coroutine_fn vduse_blk_virtio_process_req(void 
*opaque)
     }
 
     vduse_blk_req_complete(req, in_len);
+    vduse_blk_inflight_dec(vblk_exp);
 }
 
 static void vduse_blk_vq_handler(VduseDev *dev, VduseVirtq *vq)
 {
+    VduseBlkExport *vblk_exp = vduse_dev_get_priv(dev);
+
     while (1) {
         VduseBlkReq *req;
 
@@ -83,6 +99,8 @@ static void vduse_blk_vq_handler(VduseDev *dev, VduseVirtq 
*vq)
 
         Coroutine *co =
             qemu_coroutine_create(vduse_blk_virtio_process_req, req);
+
+        vduse_blk_inflight_inc(vblk_exp);
         qemu_coroutine_enter(co);
     }
 }
@@ -168,6 +186,8 @@ static void vduse_blk_detach_ctx(VduseBlkExport *vblk_exp)
     }
     aio_set_fd_handler(vblk_exp->export.ctx, vduse_dev_get_fd(vblk_exp->dev),
                        true, NULL, NULL, NULL, NULL, NULL);
+
+    AIO_WAIT_WHILE(vblk_exp->export.ctx, vblk_exp->inflight > 0);
 }
 
 
@@ -332,7 +352,9 @@ static void vduse_blk_exp_request_shutdown(BlockExport *exp)
 {
     VduseBlkExport *vblk_exp = container_of(exp, VduseBlkExport, export);
 
+    aio_context_acquire(vblk_exp->export.ctx);
     vduse_blk_detach_ctx(vblk_exp);
+    aio_context_acquire(vblk_exp->export.ctx);
 }
 
 const BlockExportDriver blk_exp_vduse_blk = {
-- 
2.20.1