9pfs: add cleanup operation in FileOperations

Currently, the backend of VirtFS doesn't have a cleanup
function. This will lead resource leak issues if the backed
driver allocates resources. This patch addresses this issue.

Signed-off-by: Li Qiang <liq3ea@gmail.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Greg Kurz <groug@kaod.org>

fsdev/file-op-9p.h

@@ -100,6 +100,7 @@ struct FileOperations
 {
     int (*parse_opts)(QemuOpts *, struct FsDriverEntry *);
     int (*init)(struct FsContext *);
+    void (*cleanup)(struct FsContext *);
     int (*lstat)(FsContext *, V9fsPath *, struct stat *);
     ssize_t (*readlink)(FsContext *, V9fsPath *, char *, size_t);
     int (*chmod)(FsContext *, V9fsPath *, FsCred *);

hw/9pfs/9p.c

@@ -3521,6 +3521,9 @@ int v9fs_device_realize_common(V9fsState *s, Error **errp)
     rc = 0;
 out:
     if (rc) {
+        if (s->ops->cleanup && s->ctx.private) {
+            s->ops->cleanup(&s->ctx);
+        }
         g_free(s->tag);
         g_free(s->ctx.fs_root);
         v9fs_path_free(&path);
@@ -3530,6 +3533,9 @@ out:
 
 void v9fs_device_unrealize_common(V9fsState *s, Error **errp)
 {
+    if (s->ops->cleanup) {
+        s->ops->cleanup(&s->ctx);
+    }
     g_free(s->tag);
     g_free(s->ctx.fs_root);
 }