block/nvme: separate nvme_get_free_req cases for coroutine/non-coroutine context

nvme_get_free_req has very difference semantics when called in
coroutine context (where it waits) and in non-coroutine context
(where it doesn't).  Split the two cases to make it clear what
is being requested.

Cc: qemu-block@nongnu.org
Reviewed-by: Alberto Faria <afaria@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220922084924.201610-2-pbonzini@redhat.com>
[kwolf: Fixed up coding style]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 28 insertions, 20 deletions

diff --git a/block/nvme.c b/block/nvme.c
index 01fb28aa63..0870f87bc6 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -293,34 +293,42 @@ static void nvme_kick(NVMeQueuePair *q)
     q->need_kick = 0;
 }
 
-/* Find a free request element if any, otherwise:
- * a) if in coroutine context, try to wait for one to become available;
- * b) if not in coroutine, return NULL;
- */
-static NVMeRequest *nvme_get_free_req(NVMeQueuePair *q)
+static NVMeRequest *nvme_get_free_req_nofail_locked(NVMeQueuePair *q)
 {
     NVMeRequest *req;
 
-    qemu_mutex_lock(&q->lock);
-
-    while (q->free_req_head == -1) {
-        if (qemu_in_coroutine()) {
-            trace_nvme_free_req_queue_wait(q->s, q->index);
-            qemu_co_queue_wait(&q->free_req_queue, &q->lock);
-        } else {
-            qemu_mutex_unlock(&q->lock);
-            return NULL;
-        }
-    }
-
     req = &q->reqs[q->free_req_head];
     q->free_req_head = req->free_req_next;
     req->free_req_next = -1;
-
-    qemu_mutex_unlock(&q->lock);
     return req;
 }
 
+/* Return a free request element if any, otherwise return NULL.  */
+static NVMeRequest *nvme_get_free_req_nowait(NVMeQueuePair *q)
+{
+    QEMU_LOCK_GUARD(&q->lock);
+    if (q->free_req_head == -1) {
+        return NULL;
+    }
+    return nvme_get_free_req_nofail_locked(q);
+}
+
+/*
+ * Wait for a free request to become available if necessary, then
+ * return it.
+ */
+static coroutine_fn NVMeRequest *nvme_get_free_req(NVMeQueuePair *q)
+{
+    QEMU_LOCK_GUARD(&q->lock);
+
+    while (q->free_req_head == -1) {
+        trace_nvme_free_req_queue_wait(q->s, q->index);
+        qemu_co_queue_wait(&q->free_req_queue, &q->lock);
+    }
+
+    return nvme_get_free_req_nofail_locked(q);
+}
+
 /* With q->lock */
 static void nvme_put_free_req_locked(NVMeQueuePair *q, NVMeRequest *req)
 {
@@ -506,7 +514,7 @@ static int nvme_admin_cmd_sync(BlockDriverState *bs, NvmeCmd *cmd)
     AioContext *aio_context = bdrv_get_aio_context(bs);
     NVMeRequest *req;
     int ret = -EINPROGRESS;
-    req = nvme_get_free_req(q);
+    req = nvme_get_free_req_nowait(q);
     if (!req) {
         return -EBUSY;
     }