Re: [Qemu-devel] [PATCH 3/5] dev-mtp: retry write for incomplete transfers

[Thomas Huth <thuth@redhat.com>]

On 2018-07-20 23:40, Bandan Das wrote:
> For large buffers, write may not copy the full buffer. For example,
> on Linux, write imposes a limit of 0x7ffff000. Note that this does
> not fix >4G transfers but ~>2G files will transfer successfully.
> 
> Signed-off-by: Bandan Das <bsd@redhat.com>
> ---
>  hw/usb/dev-mtp.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/usb/dev-mtp.c b/hw/usb/dev-mtp.c
> index 1b72603dc5..c8f6eb4e9e 100644
> --- a/hw/usb/dev-mtp.c
> +++ b/hw/usb/dev-mtp.c
> @@ -1602,6 +1602,24 @@ static void utf16_to_str(uint8_t len, uint16_t *arr, char *name)
>      g_free(wstr);
>  }
>  
> +/* Wrapper around write, returns 0 on failure */
> +static uint64_t write_retry(int fd, void *buf, uint64_t size)
> +{
> +        uint64_t bytes_left = size, ret;
> +
> +        while (bytes_left > 0) {
> +                ret = write(fd, buf, bytes_left);
> +                if ((ret == -1) && (errno != EINTR || errno != EAGAIN ||
> +                                    errno != EWOULDBLOCK)) {

Someone opened a bug ticket about this here:

 https://bugs.launchpad.net/qemu/+bug/1798780

The check looks wrong, indeed - either "!=" should be "==" or "||"
should be "&&" here ?

 Thomas