On Fri, Jul 01, 2022 at 08:38:07AM -0600, Jens Axboe wrote: > 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. <shrug> I had thought that NOWAIT means "don't wait for *any*thing", which would include timestamp updates... but then I've never been all that clear on what specifically NOWAIT will and won't wait for. :/ --D > -- > Jens Axboe >
