task_work is a LIFO list, due to how it's implemented as a lockless
list. For long chains of task_work, this can be problematic as the
first entry added is the last one processed. Similarly, we'd waste
a lot of CPU cycles reversing this list.

Wrap the task_work so we have a single task_work entry per task per
ctx, and use that to run it in the right order.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that we have the submit_state in the ring itself, we can have io_kiocb
allocations that are persistent across invocations. This reduces the time
spent doing slab allocations and frees.

[sil: rebased]
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Make io_req_free_batch(), which is used for inline executed requests and
IOPOLL, to return requests back into the allocation cache, so avoid
most of kmalloc()/kfree() for those cases.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Don't free batch-allocated requests across syscalls.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Currently batch free handles request memory freeing and ctx ref putting
together. Separate them and use different counters, that will be needed
for reusing reqs memory.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Remove fallback_req for now, it gets in the way of other changes.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_submit_flush_completions() does completion batching, but may also use
free batching as iopoll does. The main beneficiaries should be buffered
reads/writes and send/recv.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Reincarnation of an old patch that replaces a list in struct
io_compl_batch with an array. It's needed to avoid hooking requests via
their compl.list, because it won't be always available in the future.

It's also nice to split io_submit_flush_completions() to avoid free
under locks and remove unlock/lock with a long comment describing when
it can be done.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

As now submit_state is retained across syscalls, we can save ourself
from initialising it from ground up for each io_submit_sqes(). Set some
fields during ctx allocation, and just keep them always consistent.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: remove unnecessary zeroing of ctx members]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

completion state is closely bound to ctx, we don't need to store ctx
inside as we always have it around to pass to flush.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

struct io_submit_state is quite big (168 bytes) and going to grow. It's
better to not keep it on stack as it is now. Move it to context, it's
always protected by uring_lock, so it's fine to have only one instance
of it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

There is no reason to drag io_comp_state into opcode handlers, we just
need a flag and the actual work will be done in __io_queue_sqe().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Make opcode handler interfaces a bit more consistent by always passing
in issue flags. Bulky but pretty easy and mechanical change.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Replace bool force_nonblock with flags. It has a long standing goal of
differentiating context from which we execute. Currently we have some
subtle places where some invariants, like holding of uring_lock, are
subtly inferred.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

For SQPOLL rings tctx_inflight() always returns zero, so it might skip
doing full cancelation. It's fine because we jam all sqpoll submissions
in any case and do go through files cancel for them, but not nice.

Do the intended full cancellation, by mimicking __io_uring_task_cancel()
waiting but impersonating SQPOLL task.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Current iov handling with recvmsg/sendmsg may be confusing. First make a
rule for msg->iov: either it points to an allocated iov that have to be
kfree()'d later, or it's NULL and we use fast_iov. That's much better
than current 3-state (also can point to fast_iov). And rename it into
free_iov for uniformity with read/write.

Also, instead of after struct io_async_msghdr copy fixing up of
msg.msg_iter.iov has been happening in io_recvmsg()/io_sendmsg(). Move
it into io_setup_async_msg(), that's the right place.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: add comment on NULL check before kfree()]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Don't pretend we don't know that REQ_F_BUFFER_SELECT for recvmsg always
uses fast_iov -- clean up confusing intermixing kmsg->iov and
kmsg->fast_iov for buffer select.

Also don't init iter with garbage in __io_recvmsg_copy_hdr() only for it
to be set shortly after in io_recvmsg().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_setup_async_msg() should fully prepare io_async_msghdr, let it also
handle assigning msg_name and don't hand code it in [send,recv]msg().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Saving one lock/unlock for io-wq is not super important, but adds some
ugliness in the code. More important, atomic decs not turning it to zero
for some archs won't give the right ordering/barriers so the
io_steal_work() may pretty easily get subtly and completely broken.

Return back 2-step io-wq work exchange and clean it up.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Extract a helper io_fixed_file_slot() returning a place in our fixed
files table, so we don't hand-code it three times in the code.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_import_iovec() doesn't return IO size anymore, only error code. Make
it more apparent by returning int instead of ssize and clean up
leftovers.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Make decision making of whether we need to retry read/write similar for
O_NONBLOCK and RWF_NOWAIT. Set REQ_F_NOWAIT when either is specified and
use it for all relevant checks. Also fix resubmitting NOWAIT requests
via io_rw_reissue().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We already have implicit do-while for read-retries but with goto in the
end. Convert it to an actual do-while, it highlights it so making a
bit more understandable and is cleaner in general.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_read() has not the simpliest control flow with a lot of jumps and
it's hard to read. One of those is a out_free: label, which frees iovec.
However, from the middle of io_read() iovec is NULL'ed and so
kfree(iovec) is no-op, it leaves us with two place where we can inline
it and further clean up the code.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We have invariant in io_read() of how much we're trying to read spilled
into an iter and io_size variable. The last one controls decision making
about whether to do read-retries. However, io_size is modified only
after the first read attempt, so if we happen to go for a third retry in
a single call to io_read(), we will get io_size greater than in the
iterator, so may lead to various side effects up to live-locking.

Modify io_size each time.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now we give out ownership of iovec into io_setup_async_rw(), so it
either sets request's context right or frees the iovec on error itself.
Makes our life a bit easier at call sites.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

First, instead of checking iov_iter_count(iter) for 0 to find out that
all needed bytes were read, just compare returned code against io_size.
It's more reliable and arguably cleaner.

Also, place the half-read case into an else branch and delete an extra
label.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

!io_file_supports_async() case of io_read() is hard to read, it jumps
somewhere in the middle of the function just to do async setup and fail
on a similar check. Call io_setup_async_rw() directly for this case,
it's much easier to follow.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

It's easy to make a mistake in io_cqring_wait() because for all
break/continue clauses we need to watch for prepare/finish_wait to be
used correctly. Extract all those into a new helper
io_cqring_wait_schedule(), and transforming the loop into simple series
of func calls: prepare(); check_and_schedule(); finish();

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

schedule_timeout() with timeout=MAX_SCHEDULE_TIMEOUT is guaranteed to
work just as schedule(), so instead of hand-coding it based on arguments
always use the timeout version and simplify code.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Files and task cancellations go over same steps trying to cancel
requests in io-wq, poll, etc. Deduplicate it with a helper.

note: new io_uring_try_cancel_requests() is former
__io_uring_cancel_task_requests() with files passed as an agrument and
flushing overflowed requests.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

do_read() returning 0 bytes read (not -EAGAIN/etc.) is not an important
enough of a case to prioritise it. Fold it into ret < 0 check, so we get
rid of an extra if and make it a bit more readable.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We don't know for how long REQ_F_INFLIGHT is going to stay, cleaner to
extract a helper for marking requests as so.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Shouldn't be a problem now, but it's better to clean
REQ_F_WORK_INITIALIZED and work->flags only after relevant resources are
killed, so cancellation see them.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

req->files now have same lifetime as all other iowq-work resources,
inline io_req_drop_files() for consistency. Moreover, since
REQ_F_INFLIGHT is no more files specific, the function name became
very confusing.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We have no request types left using needs_file_no_error, remove it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

WARNING: inconsistent lock state

inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
syz-executor217/8450 [HC1[1]:SC0[0]:HE0:SE1] takes:
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: io_req_clean_work fs/io_uring.c:1398 [inline]
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: io_dismantle_req+0x66f/0xf60 fs/io_uring.c:2029

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

       CPU0
       ----
  lock(&fs->lock);
  <Interrupt>
    lock(&fs->lock);

 *** DEADLOCK ***

1 lock held by syz-executor217/8450:
 #0: ffff88802417c3e8 (&ctx->uring_lock){+.+.}-{3:3}, at: __do_sys_io_uring_enter+0x1071/0x1f30 fs/io_uring.c:9442

stack backtrace:
CPU: 1 PID: 8450 Comm: syz-executor217 Not tainted 5.11.0-rc5-next-20210129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
[...]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:354 [inline]
 io_req_clean_work fs/io_uring.c:1398 [inline]
 io_dismantle_req+0x66f/0xf60 fs/io_uring.c:2029
 __io_free_req+0x3d/0x2e0 fs/io_uring.c:2046
 io_free_req fs/io_uring.c:2269 [inline]
 io_double_put_req fs/io_uring.c:2392 [inline]
 io_put_req+0xf9/0x570 fs/io_uring.c:2388
 io_link_timeout_fn+0x30c/0x480 fs/io_uring.c:6497
 __run_hrtimer kernel/time/hrtimer.c:1519 [inline]
 __hrtimer_run_queues+0x609/0xe40 kernel/time/hrtimer.c:1583
 hrtimer_interrupt+0x334/0x940 kernel/time/hrtimer.c:1645
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline]
 __sysvec_apic_timer_interrupt+0x146/0x540 arch/x86/kernel/apic/apic.c:1102
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0xbd/0x100 arch/x86/kernel/apic/apic.c:1096
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:629
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:199
 spin_unlock_irq include/linux/spinlock.h:404 [inline]
 io_queue_linked_timeout+0x194/0x1f0 fs/io_uring.c:6525
 __io_queue_sqe+0x328/0x1290 fs/io_uring.c:6594
 io_queue_sqe+0x631/0x10d0 fs/io_uring.c:6639
 io_queue_link_head fs/io_uring.c:6650 [inline]
 io_submit_sqe fs/io_uring.c:6697 [inline]
 io_submit_sqes+0x19b5/0x2720 fs/io_uring.c:6960
 __do_sys_io_uring_enter+0x107d/0x1f30 fs/io_uring.c:9443
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Don't free requests from under hrtimer context (softirq) as it may sleep
or take spinlocks improperly (e.g. non-irq versions).

Cc: stable@vger.kernel.org # 5.6+
Reported-by:  <syzbot+81d17233a2b02eafba33@syzkaller.appspotmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If we hit a "goto out_free;" before the "ctx->file_data" pointer has
been assigned then it leads to a NULL derefence when we call:

	free_fixed_rsrc_data(ctx->file_data);

We can fix this by moving the assignment earlier.

Fixes: 1ad555c6

 ("io_uring: create common fixed_rsrc_data allocation routines")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Abaci reported this issue:

#[  605.170872] INFO: task kworker/u4:1:53 blocked for more than 143 seconds.
[  605.172123]       Not tainted 5.10.0+ #1
[  605.172811] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  605.173915] task:kworker/u4:1    state:D stack:    0 pid:   53 ppid:     2 flags:0x00004000
[  605.175130] Workqueue: events_unbound io_ring_exit_work
[  605.175931] Call Trace:
[  605.176334]  __schedule+0xe0e/0x25a0
[  605.176971]  ? firmware_map_remove+0x1a1/0x1a1
[  605.177631]  ? write_comp_data+0x2a/0x80
[  605.178272]  schedule+0xd0/0x270
[  605.178811]  schedule_timeout+0x6b6/0x940
[  605.179415]  ? mark_lock.part.0+0xca/0x1420
[  605.180062]  ? usleep_range+0x170/0x170
[  605.180684]  ? wait_for_completion+0x16d/0x280
[  605.181392]  ? mark_held_locks+0x9e/0xe0
[  605.182079]  ? rwlock_bug.part.0+0x90/0x90
[  605.182853]  ? lockdep_hardirqs_on_prepare+0x286/0x400
[  605.183817]  wait_for_completion+0x175/0x280
[  605.184713]  ? wait_for_completion_interruptible+0x340/0x340
[  605.185611]  ? _raw_spin_unlock_irq+0x24/0x30
[  605.186307]  ? migrate_swap_stop+0x9c0/0x9c0
[  605.187046]  kthread_park+0x127/0x1c0
[  605.187738]  io_sq_thread_stop+0xd5/0x530
[  605.188459]  io_ring_exit_work+0xb1/0x970
[  605.189207]  process_one_work+0x92c/0x1510
[  605.189947]  ? pwq_dec_nr_in_flight+0x360/0x360
[  605.190682]  ? rwlock_bug.part.0+0x90/0x90
[  605.191430]  ? write_comp_data+0x2a/0x80
[  605.192207]  worker_thread+0x9b/0xe20
[  605.192900]  ? process_one_work+0x1510/0x1510
[  605.193599]  kthread+0x353/0x460
[  605.194154]  ? _raw_spin_unlock_irq+0x24/0x30
[  605.194910]  ? kthread_create_on_node+0x100/0x100
[  605.195821]  ret_from_fork+0x1f/0x30
[  605.196605]
[  605.196605] Showing all locks held in the system:
[  605.197598] 1 lock held by khungtaskd/25:
[  605.198301]  #0: ffffffff8b5f76a0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire.constprop.0+0x0/0x30
[  605.199914] 3 locks held by kworker/u4:1/53:
[  605.200609]  #0: ffff888100109938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x82a/0x1510
[  605.202108]  #1: ffff888100e47dc0 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x85e/0x1510
[  605.203681]  #2: ffff888116931870 (&sqd->lock){+.+.}-{3:3}, at: io_sq_thread_park.part.0+0x19/0x50
[  605.205183] 3 locks held by systemd-journal/161:
[  605.206037] 1 lock held by syslog-ng/254:
[  605.206674] 2 locks held by agetty/311:
[  605.207292]  #0: ffff888101097098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x27/0x80
[  605.208715]  #1: ffffc900000332e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x222/0x1bb0
[  605.210131] 2 locks held by bash/677:
[  605.210723]  #0: ffff88810419a098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x27/0x80
[  605.212105]  #1: ffffc900000512e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x222/0x1bb0
[  605.213777]
[  605.214151] =============================================

I believe this is caused by the follow race:

(ctx_list is empty now)
=> io_put_sq_data               |
==> kthread_park(sqd->thread);  |
====> set KTHREAD_SHOULD_PARK	|
====> wake_up_process(k)        | sq thread is running
				|
				|
				| needs_sched is true since no ctx,
				| so TASK_INTERRUPTIBLE set and schedule
				| out then never wake up again
				|
====> wait_for_completion	|
	(stuck here)

So check if sqthread gets park flag right before schedule().
since ctx_list is always empty when this problem happens, here I put
kthread_should_park() before setting the wakeup flag(ctx_list is empty
so this for loop is fast), where is close enough to schedule(). The
problem doesn't show again in my repro testing after this fix.

Reported-by: Abaci <abaci@linux.alibaba.com>
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Add the missing kernel io_uring header, add Pavel as a reviewer, and
exclude io_uring from the FILESYSTEMS section to avoid keep spamming Al
(mainly) with bug reports, patches, etc.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>