io_ring_exit_work() have to cancel all requests, including those staying
in io-wq, however it tries only cancellation of current tctx, which is
NULL. If we've got task==NULL, use the ctx-to-tctx map to go over all
tctx/io-wq and try cancellations on them.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We use system_unbound_wq to run io_ring_exit_work(), so it's hard to
monitor whether removal hang or not. Add WARN_ONCE to catch hangs.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We don't use task file notes anymore, and no need left in indexing
task->io_uring->xa by file, and replace it with ctx. It's better
design-wise, especially since we keep a dangling file, and so have to
keep an eye on not dereferencing it.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

With ->flush() gone we're now leaving all uring file notes until the
task dies/execs, so the ctx will not be freed until all tasks that have
ever submit a request die. It was nicer with flush but not much, we
could have locked as described ctx in many cases.

Now we guarantee that ctx outlives all tctx in a sense that
io_ring_exit_work() waits for all tctxs to drop their corresponding
enties in ->xa, and ctx won't go away until then. Hence, additional
io_uring file reference (a.k.a. task file notes) are not needed anymore.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Another preparation patch. When full quiesce is done on ctx exit, use
task_work infra to remove corresponding to the ctx io_uring->xa entries.
For that we use the back tctx map. Also use ->in_idle to prevent
removing it while we traversing ->xa on cancellation, just ignore it.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

For each pair tcxt-ctx create an object and chain it into ctx, so we
have a way to traverse all tctx that are using current ctx. Preparation
patch, will be used later.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Rework io_uring_del_task_file(), so it accepts an index to delete, and
it's not necessarily have to be in the ->xa. Infer file from xa_erase()
to maintain a single origin of truth.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we go async with a request, grab the creds that the task currently has
assigned and make sure that the async side switches to them. This is
handled in the same way that we do for registered personalities.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Ran into a use-after-free on the main io-wq struct, wq. It has a worker
ref and completion event, but the manager itself isn't holding a
reference. This can lead to a race where the manager thinks there are
no workers and exits, but a worker is being added. That leads to the
following trace:

BUG: KASAN: use-after-free in io_wqe_worker+0x4c0/0x5e0
Read of size 8 at addr ffff888108baa8a0 by task iou-wrk-3080422/3080425

CPU: 5 PID: 3080425 Comm: iou-wrk-3080422 Not tainted 5.12.0-rc1+ #110
Hardware name: Micro-Star International Co., Ltd. MS-7C60/TRX40 PRO 10G (MS-7C60), BIOS 1.60 05/13/2020
Call Trace:
 dump_stack+0x90/0xbe
 print_address_description.constprop.0+0x67/0x28d
 ? io_wqe_worker+0x4c0/0x5e0
 kasan_report.cold+0x7b/0xd4
 ? io_wqe_worker+0x4c0/0x5e0
 __asan_load8+0x6d/0xa0
 io_wqe_worker+0x4c0/0x5e0
 ? io_worker_handle_work+0xc00/0xc00
 ? recalc_sigpending+0xe5/0x120
 ? io_worker_handle_work+0xc00/0xc00
 ? io_worker_handle_work+0xc00/0xc00
 ret_from_fork+0x1f/0x30

Allocated by task 3080422:
 kasan_save_stack+0x23/0x60
 __kasan_kmalloc+0x80/0xa0
 kmem_cache_alloc_node_trace+0xa0/0x480
 io_wq_create+0x3b5/0x600
 io_uring_alloc_task_context+0x13c/0x380
 io_uring_add_task_file+0x109/0x140
 __x64_sys_io_uring_enter+0x45f/0x660
 do_syscall_64+0x32/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 3080422:
 kasan_save_stack+0x23/0x60
 kasan_set_track+0x20/0x40
 kasan_set_free_info+0x24/0x40
 __kasan_slab_free+0xe8/0x120
 kfree+0xa8/0x400
 io_wq_put+0x14a/0x220
 io_wq_put_and_exit+0x9a/0xc0
 io_uring_clean_tctx+0x101/0x140
 __io_uring_files_cancel+0x36e/0x3c0
 do_exit+0x169/0x1340
 __x64_sys_exit+0x34/0x40
 do_syscall_64+0x32/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Have the manager itself hold a reference, and now both drop points drop
and complete if we hit zero, and the manager can unconditionally do a
wait_for_completion() instead of having a race between reading the ref
count and waiting if it was non-zero.

Fixes: fb3a1f6c ("io-wq: have manager wait for all workers to exit")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

45d189c6 ("io_uring: replace force_nonblock with flags") did
something strange for io_openat() slicing all issue_flags but
IO_URING_F_NONBLOCK. Not a bug for now, but better to just forward the
flags.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We have this weird true/false return from parking, and then some of the
callers decide to look at that. It can lead to unbalanced parks and
sqd locking. Have the callers check the thread status once it's parked.
We know we have the lock at that point, so it's either valid or it's NULL.

Fix race with parking on thread exit. We need to be careful here with
ordering of the sdq->lock and the IO_SQ_THREAD_SHOULD_PARK bit.

Rename sqd->completion to sqd->parked to reflect that this is the only
thing this completion event doesn.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we race with shutting down the io-wq context and someone queueing
a hashed entry, then we can exit the manager with it armed. If it then
triggers after the manager has exited, we can have a use-after-free where
io_wqe_hash_wake() attempts to wake a now gone manager process.

Move the killing of the hashed write queue into the manager itself, so
that we know we've killed it before the task exits.

Fixes: e941894e ("io-wq: make buffered file write hashed work map per-ctx")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The callback can only be armed, if we get -EIOCBQUEUED returned. It's
important that we clear the WAITQ bit for other cases, otherwise we can
queue for async retry and filemap will assume that we're armed and
return -EAGAIN instead of just blocking for the IO.

Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: NJens Axboe <axboe@kernel.dk>

It doesn't make sense to wait for more events to come in, if we can't
even flush the overflow we already have to the ring. Return -EBUSY for
that condition, just like we do for attempts to submit with overflow
pending.

Cc: stable@vger.kernel.org # 5.11
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This allows us to do task creation and setup without needing to use
completions to try and synchronize with the starting thread. Get rid of
the old io_wq_fork_thread() wrapper, and the 'wq' and 'worker' startup
completion events - we can now do setup before the task is running.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Linked timeouts are fired asynchronously (i.e. soft-irq), and use
generic cancellation paths to do its stuff, including poking into io-wq.
The problem is that it's racy to access tctx->io_wq, as
io_uring_task_cancel() and others may be happening at this exact moment.
Mark linked timeouts with REQ_F_INLIFGHT for now, making sure there are
no timeouts before io-wq destraction.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Instead of going into request internals, like checking req->file->f_op,
do match them based on REQ_F_INFLIGHT, it's set only when we want it to
be reliably cancelled.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We migrate zone unusable bytes to read-only bytes when a block group is
set to read-only, and account all the free region as bytes_readonly.
Thus, we should not increase block_group->zone_unusable when the block
group is read-only.

Fixes: 169e0da9 ("btrfs: zoned: track unusable bytes for zones")
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

We need to use sector_t for zone_sectors, or it would set the zone size
to zero when the size >= 4GB (= 2^24 sectors) by shifting the
zone_sectors value by SECTOR_SHIFT. We're assuming zones sizes up to
8GiB.

Fixes: 5b316468 ("btrfs: get zone information of zoned block devices")
Reviewed-by: NJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: NNaohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

If we race on shutting down the io-wq, then we should ensure that any
work that was queued after workers shutdown is canceled. Harden the
add work check a bit too, checking for IO_WQ_BIT_EXIT and cancel if
it's set.

Add a WARN_ON() for having any work before we kill the io-wq context.

Reported-by: syzbot+91b4b56ead187d35c9d3@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Alex reports that his system fails to suspend using 5.12-rc1, with the
following dump:

[  240.650300] PM: suspend entry (deep)
[  240.650748] Filesystems sync: 0.000 seconds
[  240.725605] Freezing user space processes ...
[  260.739483] Freezing of tasks failed after 20.013 seconds (3 tasks refusing to freeze, wq_busy=0):
[  260.739497] task:iou-mgr-446     state:S stack:    0 pid:  516 ppid:   439 flags:0x00004224
[  260.739504] Call Trace:
[  260.739507]  ? sysvec_apic_timer_interrupt+0xb/0x81
[  260.739515]  ? pick_next_task_fair+0x197/0x1cde
[  260.739519]  ? sysvec_reschedule_ipi+0x2f/0x6a
[  260.739522]  ? asm_sysvec_reschedule_ipi+0x12/0x20
[  260.739525]  ? __schedule+0x57/0x6d6
[  260.739529]  ? del_timer_sync+0xb9/0x115
[  260.739533]  ? schedule+0x63/0xd5
[  260.739536]  ? schedule_timeout+0x219/0x356
[  260.739540]  ? __next_timer_interrupt+0xf1/0xf1
[  260.739544]  ? io_wq_manager+0x73/0xb1
[  260.739549]  ? io_wq_create+0x262/0x262
[  260.739553]  ? ret_from_fork+0x22/0x30
[  260.739557] task:iou-mgr-517     state:S stack:    0 pid:  522 ppid:   439 flags:0x00004224
[  260.739561] Call Trace:
[  260.739563]  ? sysvec_apic_timer_interrupt+0xb/0x81
[  260.739566]  ? pick_next_task_fair+0x16f/0x1cde
[  260.739569]  ? sysvec_apic_timer_interrupt+0xb/0x81
[  260.739571]  ? asm_sysvec_apic_timer_interrupt+0x12/0x20
[  260.739574]  ? __schedule+0x5b7/0x6d6
[  260.739578]  ? del_timer_sync+0x70/0x115
[  260.739581]  ? schedule_timeout+0x211/0x356
[  260.739585]  ? __next_timer_interrupt+0xf1/0xf1
[  260.739588]  ? io_wq_check_workers+0x15/0x11f
[  260.739592]  ? io_wq_manager+0x69/0xb1
[  260.739596]  ? io_wq_create+0x262/0x262
[  260.739600]  ? ret_from_fork+0x22/0x30
[  260.739603] task:iou-wrk-517     state:S stack:    0 pid:  523 ppid:   439 flags:0x00004224
[  260.739607] Call Trace:
[  260.739609]  ? __schedule+0x5b7/0x6d6
[  260.739614]  ? schedule+0x63/0xd5
[  260.739617]  ? schedule_timeout+0x219/0x356
[  260.739621]  ? __next_timer_interrupt+0xf1/0xf1
[  260.739624]  ? task_thread.isra.0+0x148/0x3af
[  260.739628]  ? task_thread_unbound+0xa/0xa
[  260.739632]  ? task_thread_bound+0x7/0x7
[  260.739636]  ? ret_from_fork+0x22/0x30
[  260.739647] OOM killer enabled.
[  260.739648] Restarting tasks ... done.
[  260.740077] PM: suspend exit

Play nice and ensure that any thread we create will call try_to_freeze()
at an opportune time so that memory suspend can proceed. For the io-wq
worker threads, mark them as PF_NOFREEZE. They could potentially be
blocked for a long time.
Reported-by: NAlex Xu (Hello71) <alex_y_xu@yahoo.ca>
Tested-by: NAlex Xu (Hello71) <alex_y_xu@yahoo.ca>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

io_dismantle_req() is always followed by io_put_task(), which already do
proper in_idle wake ups, so we can skip waking the owner task in
io_dismantle_req(). The rules are simpler now, do io_put_task() shortly
after ending a request, and it will be fine.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

__io_queue_async_work() is only called from io_queue_async_work(),
inline it.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Inline io_req_clean_work(), less code and easier to analyse
tctx dependencies and refs usage.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When we cancel SQPOLL, @task in io_uring_try_cancel_requests() will
differ from current. Use the right tctx from passed in @task, and don't
forget that it can be NULL when the io_uring ctx exits.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We no longer revert the iovec on -EIOCBQUEUED, see commit ab2125df,
and this started causing issues for IOPOLL on devies that run out of
request slots. Turns out what outside of needing a revert for those, we
also had a bug where we didn't properly setup retry inside the submission
path. That could cause re-import of the iovec, if any, and that could lead
to spurious results if the application had those allocated on the stack.

Catch -EAGAIN retry and make the iovec stable for IOPOLL, just like we do
for !IOPOLL retries.

Cc: <stable@vger.kernel.org> # 5.9+
Reported-by: NAbaci Robot <abaci@linux.alibaba.com>
Reported-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The 'err' path should include the hash put, we already grabbed a reference
once we get that far.

Fixes: e941894e ("io-wq: make buffered file write hashed work map per-ctx")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Now, sqo_task is used only for a warning that is not interesting anymore
since sqo_dead is gone, remove all of that including ctx->sqo_task.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

As SQPOLL task doesn't poke into ->sqo_task anymore, there is no need to
kill the sqo when the master task exits. Before it was necessary to
avoid races accessing sqo_task->files with removing them.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
[axboe: don't forget to enable SQPOLL before exit, if started disabled]
Signed-off-by: NJens Axboe <axboe@kernel.dk>

syzbot reports a deadlock, attempting to lock the same spinlock twice:

============================================
WARNING: possible recursive locking detected
5.11.0-syzkaller #0 Not tainted
--------------------------------------------
swapper/1/0 is trying to acquire lock:
ffff88801b2b1130 (&runtime->sleep){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
ffff88801b2b1130 (&runtime->sleep){..-.}-{2:2}, at: io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4960

but task is already holding lock:
ffff88801b2b3130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&runtime->sleep);
  lock(&runtime->sleep);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by swapper/1/0:
 #0: ffff888147474908 (&group->lock){..-.}-{2:2}, at: _snd_pcm_stream_lock_irqsave+0x9f/0xd0 sound/core/pcm_native.c:170
 #1: ffff88801b2b3130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137

stack backtrace:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0xfa/0x151 lib/dump_stack.c:120
 print_deadlock_bug kernel/locking/lockdep.c:2829 [inline]
 check_deadlock kernel/locking/lockdep.c:2872 [inline]
 validate_chain kernel/locking/lockdep.c:3661 [inline]
 __lock_acquire.cold+0x14c/0x3b4 kernel/locking/lockdep.c:4900
 lock_acquire kernel/locking/lockdep.c:5510 [inline]
 lock_acquire+0x1ab/0x730 kernel/locking/lockdep.c:5475
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:354 [inline]
 io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4960
 __wake_up_common+0x147/0x650 kernel/sched/wait.c:108
 __wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:138
 snd_pcm_update_state+0x46a/0x540 sound/core/pcm_lib.c:203
 snd_pcm_update_hw_ptr0+0xa75/0x1a50 sound/core/pcm_lib.c:464
 snd_pcm_period_elapsed+0x160/0x250 sound/core/pcm_lib.c:1805
 dummy_hrtimer_callback+0x94/0x1b0 sound/drivers/dummy.c:378
 __run_hrtimer kernel/time/hrtimer.c:1519 [inline]
 __hrtimer_run_queues+0x609/0xe40 kernel/time/hrtimer.c:1583
 hrtimer_run_softirq+0x17b/0x360 kernel/time/hrtimer.c:1600
 __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
 invoke_softirq kernel/softirq.c:221 [inline]
 __irq_exit_rcu kernel/softirq.c:422 [inline]
 irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:29 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline]
RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:137 [inline]
RIP: 0010:acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
RIP: 0010:acpi_idle_do_entry+0x1c9/0x250 drivers/acpi/processor_idle.c:516
Code: dd 38 6e f8 84 db 75 ac e8 54 32 6e f8 e8 0f 1c 74 f8 e9 0c 00 00 00 e8 45 32 6e f8 0f 00 2d 4e 4a c5 00 e8 39 32 6e f8 fb f4 <9c> 5b 81 e3 00 02 00 00 fa 31 ff 48 89 de e8 14 3a 6e f8 48 85 db
RSP: 0018:ffffc90000d47d18 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff8880115c3780 RSI: ffffffff89052537 RDI: 0000000000000000
RBP: ffff888141127064 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff81794168 R11: 0000000000000000 R12: 0000000000000001
R13: ffff888141127000 R14: ffff888141127064 R15: ffff888143331804
 acpi_idle_enter+0x361/0x500 drivers/acpi/processor_idle.c:647
 cpuidle_enter_state+0x1b1/0xc80 drivers/cpuidle/cpuidle.c:237
 cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:351
 call_cpuidle kernel/sched/idle.c:158 [inline]
 cpuidle_idle_call kernel/sched/idle.c:239 [inline]
 do_idle+0x3e1/0x590 kernel/sched/idle.c:300
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:397
 start_secondary+0x274/0x350 arch/x86/kernel/smpboot.c:272
 secondary_startup_64_no_verify+0xb0/0xbb

which is due to the driver doing poll_wait() twice on the same
wait_queue_head. That is perfectly valid, but from checking the rest
of the kernel tree, it's the only driver that does this.

We can handle this just fine, we just need to ignore the second addition
as we'll get woken just fine on the first one.

Cc: stable@vger.kernel.org # 5.8+
Fixes: 18bceab1 ("io_uring: allow POLL_ADD with double poll_wait() users")
Reported-by: syzbot+28abd693db9e92c160d8@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we create it in a disabled state because IORING_SETUP_R_DISABLED is
set on ring creation, we need to ensure that we've kicked the thread if
we're exiting before it's been explicitly disabled. Otherwise we can run
into a deadlock where exit is waiting go park the SQPOLL thread, but the
SQPOLL thread itself is waiting to get a signal to start.

That results in the below trace of both tasks hung, waiting on each other:

INFO: task syz-executor458:8401 blocked for more than 143 seconds.
      Not tainted 5.11.0-next-20210226-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor458 state:D stack:27536 pid: 8401 ppid:  8400 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:4324 [inline]
 __schedule+0x90c/0x21a0 kernel/sched/core.c:5075
 schedule+0xcf/0x270 kernel/sched/core.c:5154
 schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x168/0x270 kernel/sched/completion.c:138
 io_sq_thread_park fs/io_uring.c:7115 [inline]
 io_sq_thread_park+0xd5/0x130 fs/io_uring.c:7103
 io_uring_cancel_task_requests+0x24c/0xd90 fs/io_uring.c:8745
 __io_uring_files_cancel+0x110/0x230 fs/io_uring.c:8840
 io_uring_files_cancel include/linux/io_uring.h:47 [inline]
 do_exit+0x299/0x2a60 kernel/exit.c:780
 do_group_exit+0x125/0x310 kernel/exit.c:922
 __do_sys_exit_group kernel/exit.c:933 [inline]
 __se_sys_exit_group kernel/exit.c:931 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:931
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43e899
RSP: 002b:00007ffe89376d48 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004af2f0 RCX: 000000000043e899
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000010000000
R10: 0000000000008011 R11: 0000000000000246 R12: 00000000004af2f0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
INFO: task iou-sqp-8401:8402 can't die for more than 143 seconds.
task:iou-sqp-8401    state:D stack:30272 pid: 8402 ppid:  8400 flags:0x00004004
Call Trace:
 context_switch kernel/sched/core.c:4324 [inline]
 __schedule+0x90c/0x21a0 kernel/sched/core.c:5075
 schedule+0xcf/0x270 kernel/sched/core.c:5154
 schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x168/0x270 kernel/sched/completion.c:138
 io_sq_thread+0x27d/0x1ae0 fs/io_uring.c:6717
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task iou-sqp-8401:8402 blocked for more than 143 seconds.

Reported-by: syzbot+fb5458330b4442f2090d@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>

io_run_ctx_fallback() can use xchg() instead of cmpxchg(). It's simpler
and faster.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

There is an unlikely but possible race using a freed context. That's
because req->task_work.func() can free a request, but we won't
necessarily find a completion in submit_state.comp and so all ctx refs
may be put by the time we do mutex_lock(&ctx->uring_ctx);

There are several reasons why it can miss going through
submit_state.comp: 1) req->task_work.func() didn't complete it itself,
but punted to iowq (e.g. reissue) and it got freed later, or a similar
situation with it overflowing and getting flushed by someone else, or
being submitted to IRQ completion, 2) As we don't hold the uring_lock,
someone else can do io_submit_flush_completions() and put our ref.
3) Bugs and code obscurities, e.g. failing to propagate issue_flags
properly.

One example is as follows

  CPU1                                  |  CPU2
=======================================================================
@req->task_work.func()                  |
  -> @req overflwed,                    |
     so submit_state.comp,nr==0         |
                                        | flush overflows, and free @req
                                        | ctx refs == 0, free it
ctx is dead, but we do                  |
	lock + flush + unlock           |

So take a ctx reference for each new ctx we see in __tctx_task_work(),
and do release it until we do all our flushing.

Fixes: 65453d1e ("io_uring: enable req cache for task_work items")
Reported-by: syzbot+a157ac7c03a56397f553@syzkaller.appspotmail.com
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
[axboe: fold in my one-liner and fix ref mismatch]
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This was always a weird work-around or file referencing, and we don't
need it anymore. Get rid of it.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We already run the fallback task_work in io_uring_try_cancel_requests(),
no need to duplicate at ring exit explicitly.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we move it in there, then we no longer have to care about it in io-wq.
This means we can drop the cred handling in io-wq, and we can drop the
REQ_F_WORK_INITIALIZED flag and async init functions as that was the last
user of it since we moved to the new workers. Then we can also drop
io_wq_work->creds, and just hold the personality u16 in there instead.
Suggested-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We're no longer checking anything that requires the work item to be
initialized, as we're not carrying any file related state there.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We prune the full cache regardless, get rid of the dead argument.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Destroy current's io-wq backend and tctx on __io_uring_task_cancel(),
aka exec(). Looks it's not strictly necessary, because it will be done
at some point when the task dies and changes of creds/files/etc. are
handled, but better to do that earlier to free io-wq and not potentially
lock previous mm and other resources for the time being.

It's safe to do because we wait for all requests of the current task to
complete, so no request will use tctx afterwards. Note, that
io_uring_files_cancel() may leave some requests for later reaping, so it
leaves tctx intact, that's ok as the task is dying anyway.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Make sure that we killed an io-wq by the time a task is dead.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>