[PULL,02/33] QIOChannelSocket: Introduce assert and reduce ifdefs to improve readability

Commit Message

Dr. David Alan Gilbert June 22, 2022, 6:38 p.m. UTC

From: Leonardo Bras <[e-mail]>

During implementation of MSG_ZEROCOPY feature, a lot of #ifdefs were
introduced, particularly at qio_channel_socket_writev().

Rewrite some of those changes so it's easier to read.

Also, introduce an assert to help detect incorrect zero-copy usage is when
it's disabled on build.

Signed-off-by: Leonardo Bras <[e-mail]>
Reviewed-by: Daniel P. Berrangé <[e-mail]>
Reviewed-by: Juan Quintela <[e-mail]>
Reviewed-by: Peter Xu <[e-mail]>
Signed-off-by: Juan Quintela <[e-mail]>
Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
  dgilbert: Fixed up thinko'd g_assert_unreachable->g_assert_not_reached
---
 io/channel-socket.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Patch

diff --git a/io/channel-socket.c b/io/channel-socket.c
index dc9c165de1..b8c13dba7c 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -578,11 +578,17 @@  static ssize_t qio_channel_socket_writev(QIOChannel *ioc,
         memcpy(CMSG_DATA(cmsg), fds, fdsize);
     }
 
-#ifdef QEMU_MSG_ZEROCOPY
     if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
+#ifdef QEMU_MSG_ZEROCOPY
         sflags = MSG_ZEROCOPY;
-    }
+#else
+        /*
+         * We expect QIOChannel class entry point to have
+         * blocked this code path already
+         */
+        g_assert_not_reached();
 #endif
+    }
 
  retry:
     ret = sendmsg(sioc->fd, &msg, sflags);
@@ -592,15 +598,13 @@  static ssize_t qio_channel_socket_writev(QIOChannel *ioc,
             return QIO_CHANNEL_ERR_BLOCK;
         case EINTR:
             goto retry;
-#ifdef QEMU_MSG_ZEROCOPY
         case ENOBUFS:
-            if (sflags & MSG_ZEROCOPY) {
+            if (flags & QIO_CHANNEL_WRITE_FLAG_ZERO_COPY) {
                 error_setg_errno(errp, errno,
                                  "Process can't lock enough memory for using MSG_ZEROCOPY");
                 return -1;
             }
             break;
-#endif
         }
 
         error_setg_errno(errp, errno,