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SubjectRe: [PATCH 3/3] tracing: clean up splice code

On Mon, 9 Feb 2009, Eduard - Gabriel Munteanu wrote:

> On Mon, Feb 09, 2009 at 08:26:20PM +0200, Pekka Enberg wrote:
> > Eduard - Gabriel Munteanu wrote:
> >>> @@ -2573,45 +2607,25 @@ static ssize_t tracing_splice_read_pipe(struct
> >>> file *filp,
> >>> ret = iter->trace->splice_read(iter, filp,
> >>> ppos, pipe, len, flags);
> >>> if (ret)
> >>> - goto out;
> >>> + goto out_err;
> >>> }
> >>> ret = tracing_wait_pipe(filp);
> >>> if (ret <= 0)
> >>> - goto out;
> >>> + goto out_err;
> >>> if (!iter->ent && !find_next_entry_inc(iter)) {
> >>> ret = -EFAULT;
> >>> - goto out;
> >>> + goto out_err;
> >>> }
> >>> /* Fill as many pages as possible. */
> >>> for (i = 0, rem = len; i < PIPE_BUFFERS && rem; i++) {
> >>> pages[i] = alloc_page(GFP_KERNEL);
> >>> + if (!pages[i])
> >>> + break;
> >> I believe you should decrement 'i' before breaking, since we fill
> >> spd.nr_pages just after the loop. In case the current page couldn't be
> >> allocated, spd.nr_pages will be one too many (that is, 'i').
> >
> > But, but, if we fail for i == 1, for example, we want ->nr_pages == 1, no?
> >
> > Pekka
>
> Sure, my bad. I even made the same assumption myself about the outer
> 'for' loop when I wrote it ('i' would end up last page + 1). The patch is
> okay. :-)

Heh, I was just about to say, if this is wrong then so is the if below it
;-)


pages[i] = alloc_page(GFP_KERNEL);
if (!pages[i])
break;

rem = tracing_fill_pipe_page(pages[i], rem, iter);

/* Copy the data into the page, so we can start over. */
ret = trace_seq_to_buffer(&iter->seq,
page_address(pages[i]),
iter->seq.len);
if (ret < 0) {
__free_page(pages[i]);

Same 'i'.
break;
}


Thanks Eduard!

-- Steve



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