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Date: Wed, 05 May 2010 08:15:19 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH v7 3/6] char: Let writers know how much
 data was written in case of errors
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To: Amit Shah <amit.shah@redhat.com>
Cc: Paul Brook <paul@codesourcery.com>, Juan Quintela <quintela@redhat.com>, qemu list <qemu-devel@nongnu.org>, Gerd Hoffmann <kraxel@redhat.com>

On 05/04/2010 04:39 PM, Amit Shah wrote:
> On writing errors, we just returned -1 even if some bytes were already
> written out. Ensure we return the number of bytes written before we
> return the error (on a subsequent call to qemu_chr_write()).
>
> Signed-off-by: Amit Shah<amit.shah@redhat.com>
> ---
>   qemu-char.c |   12 +++++++++++-
>   1 files changed, 11 insertions(+), 1 deletions(-)
>
> diff --git a/qemu-char.c b/qemu-char.c
> index 76ad12c..decf687 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -507,6 +507,9 @@ int send_all(int fd, const void *buf, int len1)
>       while (len>  0) {
>           ret = send(fd, buf, len, 0);
>           if (ret<  0) {
> +            if (len1 - len) {
> +                return len1 - len;
> +            }
>               errno = WSAGetLastError();
>               if (errno != WSAEWOULDBLOCK) {
>                   return -1;
> @@ -531,8 +534,15 @@ static int unix_write(int fd, const uint8_t *buf, int len1)
>       while (len>  0) {
>           ret = write(fd, buf, len);
>           if (ret<  0) {
> -            if (errno != EINTR&&  errno != EAGAIN)
> +            if (errno == EINTR) {
> +                continue;
> +            }
> +            if (len1 - len) {
> +                return len1 - len;
> +            }
> +            if (errno != EAGAIN) {
>                   return -1;
> +            }
>           } else if (ret == 0) {
>               break;
>           } else {
>    

This will break lots of things.  The contract for send_all and 
unix_write is that the transmit all data.

Regards,

Anthony Liguori