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. If you're confident that it's safe you can call io_req_work_drop_env() also in io_put_work(), metze
