On Thu, 2018-07-19 at 17:15 +0200, Jan Kara wrote: > On Thu 19-07-18 14:23:53, Martin Wilck wrote: > > On Thu, 2018-07-19 at 12:45 +0200, Jan Kara wrote: > > > Secondly, I don't think it is good to discard error from > > > bio_iov_iter_get_pages() here and just submit partial IO. It will > > > again > > > lead to part of IO being done as direct and part attempted to be > > > done > > > as > > > buffered. Also the "slow" direct IO path in __blkdev_direct_IO() > > > behaves > > > differently - it aborts and returns error if > > > bio_iov_iter_get_pages() > > > ever > > > returned error. IMO we should do the same here. > > > > Well, it aborts the loop, but then (in the sync case) it still > > waits > > for the already submitted IOs to finish. Here, too, I'd find it > > more > > logical to return the number of successfully transmitted bytes > > rather > > than an error code. In the async case, the submitted bios are left > > in > > place, and will probably sooner or later finish, changing iocb- > > >ki_pos. > > Well, both these behaviors make sense, just traditionally (defined by > our > implementation) DIO returns error even if part of IO has actually > been > successfully submitted. Making a userspace visible change like you > suggest > thus has to be very carefully analyzed and frankly I don't think it's > worth > the bother. OK, maybe not. I'll rework the treatment of the error case. Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg)
