v4, 4 partstransport-helper: use xread instead of read

> From: "Randall S. Becker" <rsbecker@nexbridge.com>
>
> This fix was needed on HPE NonStop NSE and NSX where SSIZE_MAX is less than
> BUFFERSIZE resulting in EINVAL. The call to read in transport-helper.c
> was the only place outside of wrapper.c where it is used instead of xread.

> Signed-off-by: Randall S. Becker <rsbecker@nexbridge.com>
> ---
>  transport-helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/transport-helper.c b/transport-helper.c
> index bf225c698f..a290695a12 100644
> --- a/transport-helper.c
> +++ b/transport-helper.c
> @@ -1225,7 +1225,7 @@ static int udt_do_read(struct unidirectional_transfer *t)
>  		return 0;	/* No space for more. */
>  
>  	transfer_debug("%s is readable", t->src_name);
> -	bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
> +	bytes = xread(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
> - 	if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
> - 		errno != EINTR) {
> + 	if (bytes < 0 && errno != EINTR) {
>  		error_errno(_("read(%s) failed"), t->src_name);

> > Signed-off-by: Randall S. Becker <rsbecker@nexbridge.com>
> > ---
> >  transport-helper.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/transport-helper.c b/transport-helper.c
> > index bf225c698f..a290695a12 100644
> > --- a/transport-helper.c
> > +++ b/transport-helper.c
> > @@ -1225,7 +1225,7 @@ static int udt_do_read(struct unidirectional_transfer *t)
> >  		return 0;	/* No space for more. */
> >  
> >  	transfer_debug("%s is readable", t->src_name);
> > -	bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
> > +	bytes = xread(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
> > - 	if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
> > - 		errno != EINTR) {
> > + 	if (bytes < 0 && errno != EINTR) {
> >  		error_errno(_("read(%s) failed"), t->src_name);
> 
> Can't we also lose EINTR check, though?  When read() returns
> negative, we check errno and if it is EINTR, continue the loop.

> On Wed, Jan 02, 2019 at 12:55:51PM -0800, Junio C Hamano wrote:
>
>> > Signed-off-by: Randall S. Becker <rsbecker@nexbridge.com>
>> > ---
>> >  transport-helper.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/transport-helper.c b/transport-helper.c
>> > index bf225c698f..a290695a12 100644
>> > --- a/transport-helper.c
>> > +++ b/transport-helper.c
>> > @@ -1225,7 +1225,7 @@ static int udt_do_read(struct unidirectional_transfer *t)
>> >  		return 0;	/* No space for more. */
>> >  
>> >  	transfer_debug("%s is readable", t->src_name);
>> > -	bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
>> > +	bytes = xread(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
>> > - 	if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
>> > - 		errno != EINTR) {
>> > + 	if (bytes < 0 && errno != EINTR) {
>> >  		error_errno(_("read(%s) failed"), t->src_name);
>> 
>> Can't we also lose EINTR check, though?  When read() returns
>> negative, we check errno and if it is EINTR, continue the loop.
>
> Yes.
>
> I also wondered if this caller might actually be relying on the current
> non-looping behavior, but it looks like I already traced through and
> determined this was OK:
>
>   https://public-inbox.org/git/20180111063110.GB31213@sigill.intra.peff.net/
>
> (the cleanup is correct either way, but that is what makes the
> conversion to xread() OK).
>
> We may want to just take the xread() conversion and then do the patch
> that I linked above on top, since it also cleans up the xwrite() spot,
> too.