Existing users access free_req_queue under q->lock. Document this.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200617132201.1832152-6-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/nvme.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/nvme.c b/block/nvme.c
index 8e60882af3..426c77e5ab 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -57,7 +57,6 @@ typedef struct {
 } NVMeRequest;
 
 typedef struct {
-    CoQueue     free_req_queue;
     QemuMutex   lock;
 
     /* Fields protected by BQL */
@@ -65,6 +64,7 @@ typedef struct {
     uint8_t     *prp_list_pages;
 
     /* Fields protected by @lock */
+    CoQueue     free_req_queue;
     NVMeQueue   sq, cq;
     int         cq_phase;
     int         free_req_head;
-- 
2.26.2