On 11/6/23 8:33 AM, Dylan Yudaken wrote: > On Mon, Nov 6, 2023 at 2:46?PM Jens Axboe <axboe@xxxxxxxxx> wrote: >> >> On 11/5/23 3:30 PM, Dylan Yudaken wrote: >>> When doing a multishot read, the code path reuses the old read >>> paths. However this breaks an assumption built into those paths, >>> namely that struct io_rw::len is available for reuse by __io_import_iovec. >>> >>> For multishot this results in len being set for the first receive >>> call, and then subsequent calls are clamped to that buffer length incorrectly. >> >> Should we just reset this to 0 always in io_read_mshot()? And preferably >> with a comment added as well as to why that is necessary to avoid >> repeated clamping. > > Unfortunately I don't think (without testing) that will work. > Sometimes the request > comes into io_read_mshot with the buffer already selected, and the > length cannot > be touched in that case. > > We could check if the buffer is set, and if not clear the length I guess. > I'm a bit unsure which is better - both seem equally ugly to be honest. I mean do it at the end when we complete it, so it's reset for the next iteration. But yeah, I'd want to have the test case verify this first :-) -- Jens Axboe
