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

["Daniel P. Berrangé" <berrange@redhat.com>]

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.

> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@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
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