Re: [PATCH v2] splice: sendfile() at once fails for big files

[Jens Axboe]

On 05/06/2015 08:38 AM, leroy christophe wrote:
> Le 06/05/2015 16:23, Jens Axboe a Ãcrit :
> > On 05/05/2015 09:41 PM, Linus Torvalds wrote:
> > > Jens, ping?
> > >
> > > The test results should make this a no-brainer, but I hate how random
> > > these flag ops.
> >
> > Missed the original, apparently. I too am confused how this is a
> > correctness fix and not just an optimization.
> >
> > +               if (read_len < len)
> > +                       sd->flags |= SPLICE_F_MORE;
> > +               else if (!more)
> > +                       sd->flags &= ~SPLICE_F_MORE;
> >
> > Should that check be for 'more', not '!more'?
> @@ -1204,6 +1204,7 @@ ssize_t splice_direct_to_actor(struct file *in,
> struct splice_desc *sd,
>        * Don't block on output, we have to drain the direct pipe.
>        */
>       sd->flags &= ~SPLICE_F_NONBLOCK;
> +    more = sd->flags & SPLICE_F_MORE;
>
>       while (len) {
>           size_t read_len;
> @@ -1216,6 +1217,10 @@ ssize_t splice_direct_to_actor(struct file *in,
> struct splice_desc *sd,
>           read_len = ret;
>           sd->total_len = read_len;
>
> +        if (read_len < len)
> +            sd->flags |= SPLICE_F_MORE;
> +        else if (!more)
> +            sd->flags &= ~SPLICE_F_MORE;
>
>
>
> 'more' contains whether sendfile() has been called with SPLICE_F_MORE or
> not.
> Until all bytes are processed, we have to force SPLICE_F_MORE regardless
> of how sendfile() was called.
> Once all bytes have been read, we have to reset the flags according to
> how sendfile() was called, so if 'more' is NOT set, we have to clear
> SPLICE_F_MORE from sd->flags (which was unconditionaly set for
> processing the first bytes)

Ah gotcha, that looks correct. Patch is fine with me then.

--
Jens Axboe

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