hw/9pfs: Reset server state during TVERSION

As per the 9p rfc, during TVERSION its necessary to clean all the active
fids, so that we start the session from a clean state. Its also needed in
scenarios where the guest is booting off 9p, and boot fails, and client
restarts, without any knowledge of the past, it will issue a TVERSION again
so this ensures that we always start from a clean state.

Signed-off-by: Deepak C Shetty <deepakcs@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

hw/9pfs/virtio-9p.c

@@ -523,6 +523,30 @@ static int v9fs_mark_fids_unreclaim(V9fsPDU *pdu, V9fsPath *path)
     return 0;
 }
 
+static void virtfs_reset(V9fsPDU *pdu)
+{
+    V9fsState *s = pdu->s;
+    V9fsFidState *fidp = NULL;
+
+    /* Free all fids */
+    while (s->fid_list) {
+        fidp = s->fid_list;
+        s->fid_list = fidp->next;
+
+        if (fidp->ref) {
+            fidp->clunked = 1;
+        } else {
+            free_fid(pdu, fidp);
+        }
+    }
+    if (fidp) {
+        /* One or more unclunked fids found... */
+        error_report("9pfs:%s: One or more uncluncked fids "
+                     "found during reset", __func__);
+    }
+    return;
+}
+
 #define P9_QID_TYPE_DIR         0x80
 #define P9_QID_TYPE_SYMLINK     0x02
 
@@ -1196,6 +1220,8 @@ static void v9fs_version(void *opaque)
     pdu_unmarshal(pdu, offset, "ds", &s->msize, &version);
     trace_v9fs_version(pdu->tag, pdu->id, s->msize, version.data);
 
+    virtfs_reset(pdu);
+
     if (!strcmp(version.data, "9P2000.u")) {
         s->proto_version = V9FS_PROTO_2000U;
     } else if (!strcmp(version.data, "9P2000.L")) {