On Mon, Oct 5, 2020 at 5:14 AM Tetsuo Handa
<penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
>
> splice() from pipe should return 0 when there is no pipe writer. However,
> since commit a194dfe6e6f6f720 ("pipe: Rearrange sequence in pipe_write()
> to preallocate slot") started inserting empty pages, splice() from pipe
> also returns 0 when all ready buffers are empty pages.
Well... Only if you had writers that intentionally did that whole "no
valid data write" thing.
Which could be seen as a feature.
That said, if this actually broke some code, then we need to fix it -
but I really hate how you have that whole !pipe_empty() loop around
the empty buffers.
That case is very unlikely, and you have a loop with !pipe_empty()
*anyway* with the whole "goto refill". So the loop is completely
pointless.
Also, what if we have a packet pipe? Do we perhaps want to return at
packet boundaries? I don't think splice() has cared, so probably not,
but it's worth perhaps thinking about.
Anyway, I'd be a lot happier with the patch being structured something
like this instead.. UNTESTED
Linus
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