On 1/28/20 5:10 PM, Pavel Begunkov wrote: > On 29/01/2020 02:51, Jens Axboe wrote: >> On 1/28/20 4:40 PM, Jens Axboe wrote: >>> On 1/28/20 4:36 PM, Pavel Begunkov wrote: >>>> On 28/01/2020 22:42, Jens Axboe wrote: >>>>> I didn't like it becoming a bit too complicated, both in terms of >>>>> implementation and use. And the fact that we'd have to jump through >>>>> hoops to make this work for a full chain. >>>>> >>>>> So I punted and just added sqe->personality and IOSQE_PERSONALITY. >>>>> This makes it way easier to use. Same branch: >>>>> >>>>> https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds >>>>> >>>>> I'd feel much better with this variant for 5.6. >>>>> >>>> >>>> Checked out ("don't use static creds/mm assignments") >>>> >>>> 1. do we miscount cred refs? We grab one in get_current_cred() for each async >>>> request, but if (worker->creds != work->creds) it will never be put. >>> >>> Yeah I think you're right, that needs a bit of fixing up. >> > > Hmm, it seems it leaks it unconditionally, as it grabs in a ref in > override_creds(). > >> I think this may have gotten fixed with the later addition posted today? >> I'll double check. But for the newer stuff, we put it for both cases >> when the request is freed. > > Yeah, maybe. I got tangled trying to verify both at once and decided to start > with the old one. > > >>>> 2. shouldn't worker->creds be named {old,saved,etc}_creds? It's set as >>>> >>>> worker->creds = override_creds(work->creds); >>>> >>>> Where override_creds() returns previous creds. And if so, then the following >>>> fast check looks strange: >>>> >>>> worker->creds != work->creds >>> >>> Don't care too much about the naming, but the logic does appear off. >>> I'll take a look at both of these tonight, unless you beat me to it. > > Apparently, you're faster :) > >> >> Testing this now, what a braino. >> >> diff --git a/fs/io-wq.c b/fs/io-wq.c >> index ee49e8852d39..8fbbadf04cc3 100644 >> --- a/fs/io-wq.c >> +++ b/fs/io-wq.c >> @@ -56,7 +56,8 @@ struct io_worker { >> >> struct rcu_head rcu; >> struct mm_struct *mm; >> - const struct cred *creds; >> + const struct cred *cur_creds; >> + const struct cred *saved_creds; >> struct files_struct *restore_files; >> }; >> >> @@ -135,9 +136,9 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker) >> { >> bool dropped_lock = false; >> >> - if (worker->creds) { >> - revert_creds(worker->creds); >> - worker->creds = NULL; >> + if (worker->saved_creds) { >> + revert_creds(worker->saved_creds); >> + worker->cur_creds = worker->saved_creds = NULL; >> } >> >> if (current->files != worker->restore_files) { >> @@ -424,10 +425,11 @@ static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work) >> static void io_wq_switch_creds(struct io_worker *worker, >> struct io_wq_work *work) >> { >> - if (worker->creds) >> - revert_creds(worker->creds); >> + if (worker->saved_creds) >> + revert_creds(worker->saved_creds); >> >> - worker->creds = override_creds(work->creds); >> + worker->saved_creds = override_creds(work->creds); >> + worker->cur_creds = work->creds; >> } > > How about as follows? rever_creds() is a bit heavier than put_creds(). > > static void io_wq_switch_creds(struct io_worker *worker, > struct io_wq_work *work) > { > const struct cred *old_creds = override_creds(work->creds); > > if (worker->saved_creds) > put_cred(old_creds); > else > worker->saved_creds = old; > worker->cur_creds = work->creds; > } Looks good to me, I'll fold. -- Jens Axboe
