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Date: Mon, 16 Feb 2015 12:56:04 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] sheepdog: fix confused return values
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To: Liu Yuan <namei.unix@gmail.com>
Cc: sheepdog@lists.wpkg.org, qemu-devel@nongnu.org, armbru@redhat.com

Am 13.02.2015 um 04:45 hat Liu Yuan geschrieben:
> From: Liu Yuan <liuyuan@cmss.chinamobile.com>
> 
> These functions mix up -1 and -errno in return values and would might cause
> trouble error handling in the call chain.
> 
> This patch let them return -errno and add some comments.
> 
> Reported-by: Markus Armbruster <armbru@redhat.com>
> Signed-off-by: Liu Yuan <liuyuan@cmss.chinamobile.com>
> ---
>  block/sheepdog.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/block/sheepdog.c b/block/sheepdog.c
> index be3176f..c28658c 100644
> --- a/block/sheepdog.c
> +++ b/block/sheepdog.c
> @@ -527,6 +527,7 @@ static SheepdogAIOCB *sd_aio_setup(BlockDriverState *bs, QEMUIOVector *qiov,
>      return acb;
>  }
>  
> +/* Return -EIO in case of error, file descriptor on success */
>  static int connect_to_sdog(BDRVSheepdogState *s, Error **errp)
>  {
>      int fd;
> @@ -546,11 +547,14 @@ static int connect_to_sdog(BDRVSheepdogState *s, Error **errp)
>  
>      if (fd >= 0) {
>          qemu_set_nonblock(fd);
> +    } else {
> +        fd = -EIO;
>      }
>  
>      return fd;
>  }
>  
> +/* Return 0 on success and -errno in case of error */
>  static coroutine_fn int send_co_req(int sockfd, SheepdogReq *hdr, void *data,
>                                      unsigned int *wlen)
>  {
> @@ -559,11 +563,13 @@ static coroutine_fn int send_co_req(int sockfd, SheepdogReq *hdr, void *data,
>      ret = qemu_co_send(sockfd, hdr, sizeof(*hdr));
>      if (ret != sizeof(*hdr)) {
>          error_report("failed to send a req, %s", strerror(errno));
> +        ret = -errno;

qemu_co_sendv_recvv() uses socket_error() internally to access the
return code. This is defined as errno on POSIX, but as WSAGetLastError()
on Windows.

You should probably either use socket_error() here, or change
qemu_co_sendv_recvv() to return a negative error code instead of -1.

>          return ret;
>      }
>  
>      ret = qemu_co_send(sockfd, data, *wlen);
>      if (ret != *wlen) {
> +        ret = -errno;
>          error_report("failed to send a req, %s", strerror(errno));
>      }

The same here.

Kevin