On 1/29/20 1:09 PM, Stefan Metzmacher wrote: > Am 29.01.20 um 18:42 schrieb Jens Axboe: >> On 1/29/20 10:34 AM, Jens Axboe wrote: >>> On 1/29/20 7:23 AM, Pavel Begunkov wrote: >>>>>>> The override_creds(personality_creds) has changed current->cred >>>>>>> and get_current_cred() will just pick it up as in the default case. >>>>>>> >>>>>>> This would make the patch much simpler and allows put_cred() to be >>>>>>> in io_put_work() instead of __io_req_aux_free() as explained above. >>>>>>> >>>>>> >>>>>> It's one extra get_current_cred(). I'd prefer to find another way to >>>>>> clean this up. >>>>> >>>>> As far as I can see it avoids a get_cred() in the IOSQE_PERSONALITY case >>>>> and the if (!req->work.creds) for both cases. >>>> >>>> Great, that you turned attention to that! override_creds() is already >>>> grabbing a ref, so it shouldn't call get_cred() there. >>>> So, that's a bug. >>> >>> It's not though - one is dropped in that function, the other when the >>> request is freed. So we do need two references to it. With the proposed >>> change to keep the override_creds() variable local for that spot we >>> don't, and the get_cred() can then go. >>> >>>> It could be I'm wrong with the statement above, need to recheck all this >>>> code to be sure. >>> >>> I think you are :-) >>> >>>> BTW, io_req_defer_prep() may be called twice for a req, so you will >>>> reassign it without putting a ref. It's safer to leave NULL checks. At >>>> least, until I've done reworking and fixing preparation paths. >>> >>> Agree, the NULL checks are safer and we should keep them. >>> >>> Going through the rest of this thread, I'm making the following changes: >>> >>> - ID must be > 0. I like that change, as we don't need an sqe flag to >>> select personality then, and it also makes it obvious that id == 0 is >>> just using current creds. >>> >>> - Fixed the missing put_cred() in the teardown >>> >>> - Use a local variable in io_submit_sqe() instead of assigning the >>> creds to req->work.creds there >>> >>> - Use cyclic idr allocation >>> >>> I'm going to fold in as appropriate. If there are fixes needed on top of >>> that, let's do them separately. >> >> In particular, would love a patch that only assigns req->work.creds if >> we do go async, so we can leave the put_cred() in io_put_work() >> instead of needing it in __io_req_aux_free(). > > I made some improvements here: > > https://git.samba.org/?p=metze/linux/wip.git;a=shortlog;h=refs/heads/for-5.6/io_uring-vfs > > Feel free to squash > https://git.samba.org/?p=metze/linux/wip.git;a=commitdiff;h=ce8812c9b935467bb08ed4d528dd92b9f67e221c > into > https://git.samba.org/?p=metze/linux/wip.git;a=commitdiff;h=22021e95e73d4658a6c834a3276886e127ab8425 > and add my review to it. Looks good to me, folded. Thanks! > If you're confident that it's safe you can > call io_req_work_drop_env() also in io_put_work(), Let's look into that later, want to flush this out sooner rather than later... -- Jens Axboe
