This little tweak restores the behaviour that was before the recent
io_worker_handle_work() optimisation patches. It makes the function do
cond_resched() and flush_signals() only if there is an actual work to
execute.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Deduplicate cancellation parts, as many of them looks the same, as do
e.g.
- io_wqe_cancel_cb_work() and io_wqe_cancel_work()
- io_wq_worker_cancel() and io_work_cancel()
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

First it changes io-wq interfaces. It replaces {get,put}_work() with
free_work(), which guaranteed to be called exactly once. It also enforces
free_work() callback to be non-NULL.

io_uring follows the changes and instead of putting a submission reference
in io_put_req_async_completion(), it will be done in io_free_work(). As
removes io_get_work() with corresponding refcount_inc(), the ref balance
is maintained.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When executing non-linked hashed work, io_worker_handle_work()
will lock-unlock wqe->lock to update hash, and then immediately
lock-unlock to get next work. Optimise this case and do
lock/unlock only once.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

There are 2 optimisations:
- Now, io_worker_handler_work() do io_assign_current_work() twice per
request, and each one adds lock/unlock(worker->lock) pair. The first is
to reset worker->cur_work to NULL, and the second to set a real work
shortly after. If there is a dependant work, set it immediately, that
effectively removes the extra NULL'ing.

- And there is no use in taking wqe->lock for linked works, as they are
not hashed now. Optimise it out.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This is a preparation patch, it adds some helpers and makes
the next patches cleaner.

- extract io_impersonate_work() and io_assign_current_work()
- replace @next label with nested do-while
- move put_work() right after NULL'ing cur_work.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

@hash_map is unsigned long, but BIT_ULL() is used for manipulations.
BIT() is a better match as it returns exactly unsigned long value.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

IO_WQ_WORK_CB is used only for linked timeouts, which will be armed
before the work setup (i.e. mm, override creds, etc). The setup
shouldn't take long, so it's ok to arm it a bit later and get rid
of IO_WQ_WORK_CB.

Make io-wq call work->func() only once, callbacks will handle the rest.
i.e. the linked timeout handler will do the actual issue. And as a
bonus, it removes an extra indirect call.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

IO_WQ_WORK_HAS_MM is set but never used, remove it.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

io_wq_flush() is buggy, during cancelation of a flush, the associated
work may be passed to the caller's (i.e. io_uring) @match callback. That
callback is expecting it to be embedded in struct io_kiocb. Cancelation
of internal work probably doesn't make a lot of sense to begin with.

As the flush helper is no longer used, just delete it and the associated
work flag.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

To cancel a work, io-wq sets IO_WQ_WORK_CANCEL and executes the
callback. However, IO_WQ_WORK_NO_CANCEL works will just execute and may
return next work, which will be ignored and lost.

Cancel the whole link.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Andres reports that buffered IO seems to suck up more cycles than we
would like, and he narrowed it down to the fact that the io-wq workers
will briefly spin for more work on completion of a work item. This was
a win on the networking side, but apparently some other cases take a
hit because of it. Remove the optimization to avoid burning more CPU
than we have to for disk IO.
Reported-by: NAndres Freund <andres@anarazel.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Glauber reports a crash on init on a box he has:

 RIP: 0010:__alloc_pages_nodemask+0x132/0x340
 Code: 18 01 75 04 41 80 ce 80 89 e8 48 8b 54 24 08 8b 74 24 1c c1 e8 0c 48 8b 3c 24 83 e0 01 88 44 24 20 48 85 d2 0f 85 74 01 00 00 <3b> 77 08 0f 82 6b 01 00 00 48 89 7c 24 10 89 ea 48 8b 07 b9 00 02
 RSP: 0018:ffffb8be4d0b7c28 EFLAGS: 00010246
 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000e8e8
 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000002080
 RBP: 0000000000012cc0 R08: 0000000000000000 R09: 0000000000000002
 R10: 0000000000000dc0 R11: ffff995c60400100 R12: 0000000000000000
 R13: 0000000000012cc0 R14: 0000000000000001 R15: ffff995c60db00f0
 FS:  00007f4d115ca900(0000) GS:ffff995c60d80000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000002088 CR3: 00000017cca66002 CR4: 00000000007606e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 PKRU: 55555554
 Call Trace:
  alloc_slab_page+0x46/0x320
  new_slab+0x9d/0x4e0
  ___slab_alloc+0x507/0x6a0
  ? io_wq_create+0xb4/0x2a0
  __slab_alloc+0x1c/0x30
  kmem_cache_alloc_node_trace+0xa6/0x260
  io_wq_create+0xb4/0x2a0
  io_uring_setup+0x97f/0xaa0
  ? io_remove_personalities+0x30/0x30
  ? io_poll_trigger_evfd+0x30/0x30
  do_syscall_64+0x5b/0x1c0
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
 RIP: 0033:0x7f4d116cb1ed

which is due to the 'wqe' and 'worker' allocation being node affine.
But it isn't valid to call the node affine allocation if the node isn't
online.

Setup structures for even offline nodes, as usual, but skip them in
terms of thread setup to not waste resources. If the node isn't online,
just alloc memory with NUMA_NO_NODE.
Reported-by: NGlauber Costa <glauber@scylladb.com>
Tested-by: NGlauber Costa <glauber@scylladb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Add a helper that allows the caller to cancel work based on what mm
it belongs to. This allows io_uring to cancel work from a given
task or thread when it exits.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We want to use the cancel functionality for canceling based on not
just the work itself. Instead of matching on the work address
manually, allow a match handler to tell us if we found the right work
item or not.

No functional changes in this patch.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Some work items need this for relative path lookup, make it available
like the other inherited credentials/mm/etc.

Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We're not consistent in how the file table is grabbed and assigned if we
have a command linked that requires the use of it.

Add ->file_table to the io_op_defs[] array, and use that to determine
when to grab the table instead of having the handlers set it if they
need to defer. This also means we can kill the IO_WQ_WORK_NEEDS_FILES
flag. We always initialize work->files, so io-wq can just check for
that.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Export a helper to attach to an existing io-wq, rather than setting up
a new one. This is doable now that we have reference counted io_wq's.
Reported-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We currently setup the io_wq with a static set of mm and creds. Even for
a single-use io-wq per io_uring, this is suboptimal as we have may have
multiple enters of the ring. For sharing the io-wq backend, it doesn't
work at all.

Switch to passing in the creds and mm when the work item is setup. This
means that async work is no longer deferred to the io_uring mm and creds,
it is done with the current mm and creds.

Flag this behavior with IORING_FEAT_CUR_PERSONALITY, so applications know
they can rely on the current personality (mm and creds) being the same
for direct issue and async issue.
Reviewed-by: NStefan Metzmacher <metze@samba.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

In preparation for sharing an io-wq across different users, add a
reference count that manages destruction of it.
Reviewed-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

io-wq assumes that work will complete fast (and not block), so it
doesn't create a new worker when work is enqueued, if we already have
at least one worker running. This is done on the assumption that if work
is running, then it will complete fast.

Add an option to force io-wq to fork a new worker for work queued. This
is signaled by setting IO_WQ_WORK_CONCURRENT on the work item. For that
case, io-wq will create a new worker, even though workers are already
running.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Not all work can be cancelled, some of it we may need to guarantee
that it runs to completion. Allow the caller to set IO_WQ_WORK_NO_CANCEL
on work that must not be cancelled. Note that the caller work function
must also check for IO_WQ_WORK_NO_CANCEL on work that is marked
IO_WQ_WORK_CANCEL.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we require mm and user context, mark the request for cancellation
if we fail to acquire the desired mm.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Reschedule the current IO worker to cut the risk that it is becoming
a cpu hog.
Signed-off-by: NHillf Danton <hdanton@sina.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Commit e61df66c ("io-wq: ensure free/busy list browsing see all
items") added a list for io workers in addition to the free and busy
lists, not only making worker walk cleaner, but leaving the busy list
unused. Let's remove it.
Signed-off-by: NHillf Danton <hdanton@sina.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

- Fix a few typos found while reading the code.

- Fix stale io_get_sqring comment referencing s->sqe, the 's' parameter
  was renamed to 'req', but the comment still holds.
Signed-off-by: NBrian Gianforcaro <b.gianfo@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

To avoid going to sleep only to get woken shortly thereafter, spin
briefly for new work upon completion of work.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We only have one cases of using the waitqueue to wake the worker, the
rest are using wake_up_process(). Since we can save some cycles not
fiddling with the waitqueue io_wqe_worker(), switch the work activation
to task wakeup and get rid of the now unused wait_queue_head_t in
struct io_worker.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

syzbot reports:

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9217 Comm: io_uring-sq Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:creds_are_invalid kernel/cred.c:792 [inline]
RIP: 0010:__validate_creds include/linux/cred.h:187 [inline]
RIP: 0010:override_creds+0x9f/0x170 kernel/cred.c:550
Code: ac 25 00 81 fb 64 65 73 43 0f 85 a3 37 00 00 e8 17 ab 25 00 49 8d 7c
24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84
c0 74 08 3c 03 0f 8e 96 00 00 00 41 8b 5c 24 10 bf
RSP: 0018:ffff88809c45fda0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000043736564 RCX: ffffffff814f3318
RDX: 0000000000000002 RSI: ffffffff814f3329 RDI: 0000000000000010
RBP: ffff88809c45fdb8 R08: ffff8880a3aac240 R09: ffffed1014755849
R10: ffffed1014755848 R11: ffff8880a3aac247 R12: 0000000000000000
R13: ffff888098ab1600 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd51c40664 CR3: 0000000092641000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  io_sq_thread+0x1c7/0xa20 fs/io_uring.c:3274
  kthread+0x361/0x430 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Modules linked in:
---[ end trace f2e1a4307fbe2245 ]---
RIP: 0010:creds_are_invalid kernel/cred.c:792 [inline]
RIP: 0010:__validate_creds include/linux/cred.h:187 [inline]
RIP: 0010:override_creds+0x9f/0x170 kernel/cred.c:550
Code: ac 25 00 81 fb 64 65 73 43 0f 85 a3 37 00 00 e8 17 ab 25 00 49 8d 7c
24 10 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84
c0 74 08 3c 03 0f 8e 96 00 00 00 41 8b 5c 24 10 bf
RSP: 0018:ffff88809c45fda0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000043736564 RCX: ffffffff814f3318
RDX: 0000000000000002 RSI: ffffffff814f3329 RDI: 0000000000000010
RBP: ffff88809c45fdb8 R08: ffff8880a3aac240 R09: ffffed1014755849
R10: ffffed1014755848 R11: ffff8880a3aac247 R12: 0000000000000000
R13: ffff888098ab1600 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd51c40664 CR3: 0000000092641000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

which is caused by slab fault injection triggering a failure in
prepare_creds(). We don't actually need to create a copy of the creds
as we're not modifying it, we just need a reference on the current task
creds. This avoids the failure case as well, and propagates the const
throughout the stack.

Fixes: 181e448d ("io_uring: async workers should inherit the user creds")
Reported-by: syzbot+5320383e16029ba057ff@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Currently we're using 40 bytes for the io_wq_work structure, and 16 of
those is the doubly link list node. We don't need doubly linked lists,
we always add to tail to keep things ordered, and any other use case
is list traversal with deletion. For the deletion case, we can easily
support any node deletion by keeping track of the previous entry.

This shrinks io_wq_work to 32 bytes, and subsequently io_kiock from
io_uring to 216 to 208 bytes.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

There are several things that can go wrong in the current code on NUMA
systems, especially if not all nodes are online all the time:

 - If the identifiers of the online nodes do not form a single contiguous
   block starting at zero, wq->wqes will be too small, and OOB memory
   accesses will occur e.g. in the loop in io_wq_create().
 - If a node comes online between the call to num_online_nodes() and the
   for_each_node() loop in io_wq_create(), an OOB write will occur.
 - If a node comes online between io_wq_create() and io_wq_enqueue(), a
   lookup is performed for an element that doesn't exist, and an OOB read
   will probably occur.

Fix it by:

 - using nr_node_ids instead of num_online_nodes() for the allocation size;
   nr_node_ids is calculated by setup_nr_node_ids() to be bigger than the
   highest node ID that could possibly come online at some point, even if
   those nodes' identifiers are not a contiguous block
 - creating workers for all possible CPUs, not just all online ones

This is basically what the normal workqueue code also does, as far as I can
tell.
Signed-off-by: NJann Horn <jannh@google.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

These allocations are single-element allocations, so don't use the array
allocation wrapper for them.
Signed-off-by: NJann Horn <jannh@google.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we don't inherit the original task creds, then we can confuse users
like fuse that pass creds in the request header. See link below on
identical aio issue.

Link: https://lore.kernel.org/linux-fsdevel/26f0d78e-99ca-2f1b-78b9-433088053a61@scylladb.com/T/#uSigned-off-by: NJens Axboe <axboe@kernel.dk>

We currently pass in 4 arguments outside of the bounded size. In
preparation for adding one more argument, let's bundle them up in
a struct to make it more readable.

No functional changes in this patch.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When we find new work to process within the work handler, we queue the
linked timeout before we have issued the new work. This can be
problematic for very short timeouts, as we have a window where the new
work isn't visible.

Allow the work handler to store a callback function for this in the work
item, and flag it with IO_WQ_WORK_CB if the caller has done so. If that
is set, then io-wq will call the callback when it has setup the new work
item.
Reported-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

These lines are indented an extra space character.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We currently have a race where if setup is really slow, we can be
calling io_wq_destroy() before we're done setting up. This will cause
the caller to get stuck waiting for the manager to set things up, but
the manager already exited.

Fix this by doing a sync setup of the manager. This also fixes the case
where if we failed creating workers, we'd also get stuck.

In practice this race window was really small, as we already wait for
the manager to start. Hence someone would have to call io_wq_destroy()
after the task has started, but before it started the first loop. The
reported test case forked tons of these, which is why it became an
issue.

Reported-by: syzbot+0f1cc17f85154f400465@syzkaller.appspotmail.com
Fixes: 771b53d0 ("io-wq: small threadpool implementation for io_uring")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Since we don't iterate these lists anymore after commit:

e61df66c ("io-wq: ensure free/busy list browsing see all items")

we don't need to retain the nulls value we use for them. That means it's
pretty pointless to wrap the hlist_nulls_head in a structure, so get rid
of it.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We have two lists for workers in io-wq, a busy and a free list. For
certain operations we want to browse all workers, and we currently do
that by browsing the two separate lists. But since these lists are RCU
protected, we can potentially miss workers if they move between the two
lists while we're browsing them.

Add a third list, all_list, that simply holds all workers. A worker is
added to that list when it starts, and removed when it exits. This makes
the worker iteration cleaner, too.
Reported-by: NPaul E. McKenney <paulmck@kernel.org>
Reviewed-by: NPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

worker->cur_work is currently protected by the lock of the wqe that the
worker belongs to. When we send a signal to a worker, we need a stable
view of ->cur_work, so we need to hold that lock. But this doesn't work
so well, since we have the opposite order potentially on queueing work.
If POLL_ADD is used with a signalfd, then io_poll_wake() is called with
the signal lock, and that sometimes needs to insert work items.

Add a specific worker lock that protects the current work item. Then we
can guarantee that the task we're sending a signal is currently
processing the exact work we think it is.
Reported-by: NPaul E. McKenney <paulmck@kernel.org>
Reviewed-by: NPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>