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; } > > static void io_worker_handle_work(struct io_worker *worker) > @@ -480,7 +482,7 @@ static void io_worker_handle_work(struct io_worker *worker) > } > if (work->mm != worker->mm) > io_wq_switch_mm(worker, work); > - if (worker->creds != work->creds) > + if (worker->cur_creds != work->creds) > io_wq_switch_creds(worker, work); > /* > * OK to set IO_WQ_WORK_CANCEL even for uncancellable work, > -- Pavel Begunkov
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