hw/9pfs: Add yeild support for readlink

Signed-off-by: Venkateswararao Jujjuri (JV) <jvrao@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Makefile.objs

@@ -305,7 +305,7 @@ hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
 9pfs-nested-$(CONFIG_VIRTFS) = virtio-9p.o virtio-9p-debug.o
 9pfs-nested-$(CONFIG_VIRTFS) +=  virtio-9p-local.o virtio-9p-xattr.o
 9pfs-nested-$(CONFIG_VIRTFS) +=   virtio-9p-xattr-user.o virtio-9p-posix-acl.o
-9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-coth.o
+9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-coth.o cofs.o
 
 hw-obj-$(CONFIG_REALLY_VIRTFS) += $(addprefix 9pfs/, $(9pfs-nested-y))
 $(addprefix 9pfs/, $(9pfs-nested-y)): QEMU_CFLAGS+=$(GLIB_CFLAGS)

hw/9pfs/cofs.c

@@ -0,0 +1,44 @@
+
+/*
+ * Virtio 9p backend
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ *  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "fsdev/qemu-fsdev.h"
+#include "qemu-thread.h"
+#include "qemu-coroutine.h"
+#include "virtio-9p-coth.h"
+
+int v9fs_co_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
+{
+    int err;
+    ssize_t len;
+
+    buf->data = qemu_malloc(PATH_MAX);
+    v9fs_co_run_in_worker(
+        {
+            len = s->ops->readlink(&s->ctx, path->data,
+                                   buf->data, PATH_MAX - 1);
+            if (len > -1) {
+                buf->size = len;
+                buf->data[len] = 0;
+                err = 0;
+            } else {
+                err = -errno;
+            }
+        });
+    if (err) {
+        qemu_free(buf->data);
+        buf->data = NULL;
+        buf->size = 0;
+    }
+    return err;
+}

hw/9pfs/virtio-9p-coth.h

@@ -56,4 +56,5 @@ typedef struct V9fsThPool {
 
 extern void co_run_in_worker_bh(void *);
 extern int v9fs_init_worker_threads(void);
+extern int v9fs_co_readlink(V9fsState *, V9fsString *, V9fsString *);
 #endif