Re: [PATCH 08/10] oslib-posix: add qemu_fds_set_blocking() helper

[Vladimir Sementsov-Ogievskiy]

On 10.09.25 12:52, Daniel P. Berrangé wrote:

On Wed, Sep 03, 2025 at 12:44:08PM +0300, Vladimir Sementsov-Ogievskiy wrote:

And use it in io/channel-socket.c. This simplifies the following
commit, which will move this functionality from io/channel-socket.c
to the callers.

Looking at how many callers will still want the current
functionality, I'm inclined to add a flag for QIOChannel

   QIO_CHANNEL_READ_FLAG_PRESERVE_BLOCKING

which migration can pass to qio_channel_readv_full and
thus avoid adding this method and duplicated calls to
it in (almost) every caller.

Yes, I thought about this too, when preparing the series.

I'll make a patch, and make the fds-set-blocking refactoring series to be the 
separate one.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
---
  include/qemu/osdep.h |  7 +++++++
  io/channel-socket.c  | 24 +++++++++++++-----------
  util/oslib-posix.c   | 12 ++++++++++++
  3 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index 1b38cb7e45..dde98d588c 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -689,6 +689,13 @@ ssize_t qemu_write_full(int fd, const void *buf, size_t 
count)
  void qemu_set_cloexec(int fd);
  bool qemu_set_blocking(int fd, bool block, Error **errp);

+/*

+ * qemu_fds_set_blockinging:
+ * Call qemu_socket_set_block() on several fds.
+ * When @nfds = 0, does nothing, @fds is not touched.
+ */
+bool qemu_fds_set_blockinging(int *fds, int nfds, bool block, Error **errp);
+
  /* Return a dynamically allocated directory path that is appropriate for 
storing
   * local state.
   *
diff --git a/io/channel-socket.c b/io/channel-socket.c
index 4f7e86f72f..96098b5bcc 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -472,8 +472,11 @@ static void qio_channel_socket_copy_fds(struct msghdr *msg,
      *fds = NULL;

for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {

-        int fd_size, i;
+        int fd_size;
          int gotfds;
+#ifndef MSG_CMSG_CLOEXEC
+        int i;
+#endif

if (cmsg->cmsg_len < CMSG_LEN(sizeof(int)) ||

              cmsg->cmsg_level != SOL_SOCKET ||
@@ -491,20 +494,19 @@ static void qio_channel_socket_copy_fds(struct msghdr 
*msg,
          *fds = g_renew(int, *fds, *nfds + gotfds);
          memcpy(*fds + *nfds, CMSG_DATA(cmsg), fd_size);

+ /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */

+        /* TODO: don't crash on error, just handle it! */
+        qemu_fds_set_blockinging(*fds + *nfds, gotfds, true, &error_abort);
+
+#ifndef MSG_CMSG_CLOEXEC
          for (i = 0; i < gotfds; i++) {
              int fd = (*fds)[*nfds + i];
-            if (fd < 0) {
-                continue;
+            if (fd >= 0) {
+                qemu_set_cloexec(fd);
              }
-
-            /* O_NONBLOCK is preserved across SCM_RIGHTS so reset it */
-            /* TODO: don't crash on error, just handle it! */
-            qemu_set_blocking(fd, true, &error_abort);
-
-#ifndef MSG_CMSG_CLOEXEC
-            qemu_set_cloexec(fd);
-#endif
          }
+#endif
+
          *nfds += gotfds;
      }
  }
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index 8891d82db0..8589ff21ec 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -262,6 +262,18 @@ bool qemu_set_blocking(int fd, bool block, Error **errp)
      return true;
  }

+bool qemu_fds_set_blockinging(int *fds, int nfds, bool block, Error **errp)

+{
+    int i;
+    for (i = 0; i < nfds; i++) {
+        if (fds[i] >= 0 && !qemu_set_blocking(fds[i], block, errp)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
  int socket_set_fast_reuse(int fd)
  {
      int val = 1, ret;
--
2.48.1

With regards,
Daniel

--
Best regards,
Vladimir