[PATCH v8 3/7] 9pfs: split out fs driver core of v9fs_co_readdir()

[Christian Schoenebeck <qemu_oss@crudebyte.com>]

The implementation of v9fs_co_readdir() has two parts: the outer
part is executed by main I/O thread, whereas the inner part is
executed by fs driver on a background I/O thread.

Move the inner part to its own new, private function do_readdir(),
so it can be shared by another upcoming new function.

This is just a preparatory patch for the subsequent patch, with the
purpose to avoid the next patch to clutter the overall diff.

Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
---
 hw/9pfs/codir.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
index 73f9a751e1..ff57fb8619 100644
--- a/hw/9pfs/codir.c
+++ b/hw/9pfs/codir.c
@@ -18,28 +18,37 @@
 #include "qemu/main-loop.h"
 #include "coth.h"
 
+/*
+ * This must solely be executed on a background IO thread.
+ */
+static int do_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
+{
+    int err = 0;
+    V9fsState *s = pdu->s;
+    struct dirent *entry;
+
+    errno = 0;
+    entry = s->ops->readdir(&s->ctx, &fidp->fs);
+    if (!entry && errno) {
+        *dent = NULL;
+        err = -errno;
+    } else {
+        *dent = entry;
+    }
+    return err;
+}
+
 int coroutine_fn v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp,
                                  struct dirent **dent)
 {
     int err;
-    V9fsState *s = pdu->s;
 
     if (v9fs_request_cancelled(pdu)) {
         return -EINTR;
     }
-    v9fs_co_run_in_worker(
-        {
-            struct dirent *entry;
-
-            errno = 0;
-            entry = s->ops->readdir(&s->ctx, &fidp->fs);
-            if (!entry && errno) {
-                err = -errno;
-            } else {
-                *dent = entry;
-                err = 0;
-            }
-        });
+    v9fs_co_run_in_worker({
+        err = do_readdir(pdu, fidp, dent);
+    });
     return err;
 }
 
-- 
2.20.1