On 7/1/22 8:30 AM, Jens Axboe wrote: > On 7/1/22 8:19 AM, Jens Axboe wrote: >> On 6/30/22 10:39 PM, Al Viro wrote: >>> On Wed, Jun 01, 2022 at 02:01:41PM -0700, Stefan Roesch wrote: >>>> This adds the async buffered write support to XFS. For async buffered >>>> write requests, the request will return -EAGAIN if the ilock cannot be >>>> obtained immediately. >>> >>> breaks generic/471... >> >> That test case is odd, because it makes some weird assumptions about >> what RWF_NOWAIT means. Most notably that it makes it mean if we should >> instantiate blocks or not. Where did those assumed semantics come from? >> On the read side, we have clearly documented that it should "not wait >> for data which is not immediately available". >> >> Now it is possible that we're returning a spurious -EAGAIN here when we >> should not be. And that would be a bug imho. I'll dig in and see what's >> going on. > > This is the timestamp update that needs doing which will now return > -EAGAIN if IOCB_NOWAIT is set as it may block. > > I do wonder if we should just allow inode time updates with IOCB_NOWAIT, > even on the io_uring side. Either that, or passed in RWF_NOWAIT > semantics don't map completely to internal IOCB_NOWAIT semantics. At > least in terms of what generic/471 is doing, but I'm not sure who came > up with that and if it's established semantics or just some made up ones > from whomever wrote that test. I don't think they make any sense, to be > honest. Further support that generic/471 is just randomly made up semantics, it needs to special case btrfs with nocow or you'd get -EAGAIN anyway for that test. And it's relying on some random timing to see if this works. I really think that test case is just hot garbage, and doesn't test anything meaningful. -- Jens Axboe
