Jeff Moyer <jmoyer@xxxxxxxxxx> writes: > Jens Axboe <axboe@xxxxxxxxx> writes: > >> On 10/21/21 12:05 PM, Jeff Moyer wrote: >>> >>>>> I'll follow up if there are issues. >>> >>> s390 (big endian, 64 bit) is failing libaio test 21: >>> >>> # harness/cases/21.p >>> Expected -EAGAIN, got 4294967285 >>> >>> If I print out both res and res2 using %lx, you'll see what happened: >>> >>> Expected -EAGAIN, got fffffff5,ffffffff >>> >>> The sign extension is being split up. >> >> Funky, does it work if you apply this on top? >> >> diff --git a/fs/aio.c b/fs/aio.c >> index 3674abc43788..c56437908339 100644 >> --- a/fs/aio.c >> +++ b/fs/aio.c >> @@ -1442,8 +1442,8 @@ static void aio_complete_rw(struct kiocb *kiocb, u64 res) >> * 32-bits of value at most for either value, bundle these up and >> * pass them in one u64 value. >> */ >> - iocb->ki_res.res = lower_32_bits(res); >> - iocb->ki_res.res2 = upper_32_bits(res); >> + iocb->ki_res.res = (long) (res & 0xffffffff); >> + iocb->ki_res.res2 = (long) (res >> 32); >> iocb_put(iocb); >> } > > I think you'll also need to clamp any ki_complete() call sites to 32 > bits (cast to int, or what have you). Otherwise that sign extension > will spill over into res2. > > fwiw, I tested with this: > > iocb->ki_res.res = (long)(int)lower_32_bits(res); > iocb->ki_res.res2 = (long)(int)upper_32_bits(res); > > Coupled with the call site changes, that made things work for me. This is all starting to feel like a minefield. If you don't have any concrete numbers to show that there is a speedup, I think we should shelf this change. -Jeff
