vhost: stick to -errno error return convention

[PATCH 02/10] chardev/char-socket: tcp_chr_recv: don't clobber errno

Posted by Roman Kagan 4 years, 3 months ago

tcp_chr_recv communicates the specific error condition to the caller via
errno.  However, after setting it, it may call into some system calls or
library functions which can clobber the errno.

Avoid this by moving the errno assignment to the end of the function.

Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
---
 chardev/char-socket.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 836cfa0bc2..90054ce58c 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -346,13 +346,6 @@ static ssize_t tcp_chr_recv(Chardev *chr, char *buf, size_t len)
                                      NULL);
     }
 
-    if (ret == QIO_CHANNEL_ERR_BLOCK) {
-        errno = EAGAIN;
-        ret = -1;
-    } else if (ret == -1) {
-        errno = EIO;
-    }
-
     if (msgfds_num) {
         /* close and clean read_msgfds */
         for (i = 0; i < s->read_msgfds_num; i++) {
@@ -381,6 +374,13 @@ static ssize_t tcp_chr_recv(Chardev *chr, char *buf, size_t len)
 #endif
     }
 
+    if (ret == QIO_CHANNEL_ERR_BLOCK) {
+        errno = EAGAIN;
+        ret = -1;
+    } else if (ret == -1) {
+        errno = EIO;
+    }
+
     return ret;
 }
 
-- 
2.33.1

Re: [PATCH 02/10] chardev/char-socket: tcp_chr_recv: don't clobber errno

Posted by Marc-André Lureau 4 years, 3 months ago

On Thu, Nov 11, 2021 at 7:38 PM Roman Kagan <rvkagan@yandex-team.ru> wrote:

> tcp_chr_recv communicates the specific error condition to the caller via
> errno.  However, after setting it, it may call into some system calls or
> library functions which can clobber the errno.
>
> Avoid this by moving the errno assignment to the end of the function.
>
> Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

---
>  chardev/char-socket.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index 836cfa0bc2..90054ce58c 100644
> --- a/chardev/char-socket.c
> +++ b/chardev/char-socket.c
> @@ -346,13 +346,6 @@ static ssize_t tcp_chr_recv(Chardev *chr, char *buf,
> size_t len)
>                                       NULL);
>      }
>
> -    if (ret == QIO_CHANNEL_ERR_BLOCK) {
> -        errno = EAGAIN;
> -        ret = -1;
> -    } else if (ret == -1) {
> -        errno = EIO;
> -    }
> -
>      if (msgfds_num) {
>          /* close and clean read_msgfds */
>          for (i = 0; i < s->read_msgfds_num; i++) {
> @@ -381,6 +374,13 @@ static ssize_t tcp_chr_recv(Chardev *chr, char *buf,
> size_t len)
>  #endif
>      }
>
> +    if (ret == QIO_CHANNEL_ERR_BLOCK) {
> +        errno = EAGAIN;
> +        ret = -1;
> +    } else if (ret == -1) {
> +        errno = EIO;
> +    }
> +
>      return ret;
>  }
>
> --
> 2.33.1
>
>
>

-- 
Marc-André Lureau