[Libguestfs] [nbdkit PATCH v3 03/16] server: Move default_exportname from handle to connection

[Eric Blake]

struct handle represents things that can differ per export (such as
the results of .can_write), but .default_exportname is really
something that should be global to all possible exports of the
connection.  Moving it also gets rid of the leaky abstraction where
NBD_OPT_STARTTLS has to reset the cached default when changing TLS
even though there is no current handle at that time.  It also lets us
simplify reset_handle(), as it no longer tracks allocated memory, and
prepares for an upcoming patch refactoring how backend_open operates.
---
 server/internal.h                    |  6 ++----
 server/backend.c                     |  8 ++++----
 server/connections.c                 | 15 ++++++++++++---
 server/protocol-handshake-newstyle.c |  7 +++----
 4 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/server/internal.h b/server/internal.h
index 906f0690..1f37703f 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -211,8 +211,6 @@ struct handle {

   unsigned char state;  /* Bitmask of HANDLE_* values */

-  char *default_exportname;
-
   uint64_t exportsize;
   int can_write;
   int can_flush;
@@ -231,8 +229,6 @@ reset_handle (struct handle *h)
 {
   h->handle = NULL;
   h->state = 0;
-  free (h->default_exportname);
-  h->default_exportname = NULL;
   h->exportsize = -1;
   h->can_write = -1;
   h->can_flush = -1;
@@ -261,6 +257,8 @@ struct connection {
   struct handle *handles;       /* One per plugin and filter. */
   size_t nr_handles;

+  char **default_exportname;    /* One per plugin and filter. */
+
   uint32_t cflags;
   uint16_t eflags;
   bool handshake_complete;
diff --git a/server/backend.c b/server/backend.c
index e9fcd696..d08a2b6b 100644
--- a/server/backend.c
+++ b/server/backend.c
@@ -193,7 +193,7 @@ backend_default_export (struct backend *b, int readonly)
   controlpath_debug ("%s: default_export readonly=%d tls=%d",
                      b->name, readonly, conn->using_tls);

-  if (h->default_exportname == NULL) {
+  if (conn->default_exportname[b->i] == NULL) {
     assert (h->handle == NULL);
     assert ((h->state & HANDLE_OPEN) == 0);
     s = b->default_export (b, readonly, conn->using_tls);
@@ -205,12 +205,12 @@ backend_default_export (struct backend *b, int readonly)
     }
     if (s) {
       /* Best effort caching */
-      h->default_exportname = strdup (s);
-      if (h->default_exportname == NULL)
+      conn->default_exportname[b->i] = strdup (s);
+      if (conn->default_exportname[b->i] == NULL)
         return s;
     }
   }
-  return h->default_exportname;
+  return conn->default_exportname[b->i];
 }

 int
diff --git a/server/connections.c b/server/connections.c
index 38b32742..b56f89f8 100644
--- a/server/connections.c
+++ b/server/connections.c
@@ -1,5 +1,5 @@
 /* nbdkit
- * Copyright (C) 2013-2020 Red Hat Inc.
+ * Copyright (C) 2013-2021 Red Hat Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -263,6 +263,14 @@ new_connection (int sockin, int sockout, int nworkers)
   for_each_backend (b)
     reset_handle (get_handle (conn, b->i));

+  conn->default_exportname = calloc (top->i + 1,
+                                     sizeof *conn->default_exportname);
+  if (conn->default_exportname == NULL) {
+    perror ("malloc");
+    free (conn->handles);
+    goto error1;
+  }
+
   conn->status = 1;
   conn->nworkers = nworkers;
   if (nworkers) {
@@ -330,6 +338,7 @@ new_connection (int sockin, int sockout, int nworkers)
   if (conn->status_pipe[1] >= 0)
     close (conn->status_pipe[1]);
   free (conn->handles);
+  free (conn->default_exportname);

  error1:
   pthread_mutex_destroy (&conn->request_lock);
@@ -373,9 +382,9 @@ free_connection (struct connection *conn)
   free (conn->exportname_from_set_meta_context);
   free_interns ();

-  /* This is needed in order to free a field in struct handle. */
   for_each_backend (b)
-    reset_handle (get_handle (conn, b->i));
+    free (conn->default_exportname[b->i]);
+  free (conn->default_exportname);
   free (conn->handles);

   free (conn);
diff --git a/server/protocol-handshake-newstyle.c b/server/protocol-handshake-newstyle.c
index 0a76a814..fb4a93bc 100644
--- a/server/protocol-handshake-newstyle.c
+++ b/server/protocol-handshake-newstyle.c
@@ -1,5 +1,5 @@
 /* nbdkit
- * Copyright (C) 2013-2020 Red Hat Inc.
+ * Copyright (C) 2013-2021 Red Hat Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ -497,9 +497,8 @@ negotiate_handshake_newstyle_options (void)
         debug ("using TLS on this connection");
         /* Wipe out any cached default export name. */
         for_each_backend (b) {
-          struct handle *h = get_handle (conn, b->i);
-          free (h->default_exportname);
-          h->default_exportname = NULL;
+          free (conn->default_exportname[b->i]);
+          conn->default_exportname[b->i] = NULL;
         }
       }
       break;
-- 
2.30.1