There is an old problem with io-wq cancellation where requests should be
killed and are in io-wq but are not discoverable, e.g. in @next_hashed
or @linked vars of io_worker_handle_work(). It adds some unreliability
to individual request canellation, but also may potentially get
__io_uring_cancel() stuck. For instance:
1) An __io_uring_cancel()'s cancellation round have not found any
request but there are some as desribed.
2) __io_uring_cancel() goes to sleep
3) Then workers wake up and try to execute those hidden requests
that happen to be unbound.
As we already cancel all requests of io-wq there, set IO_WQ_BIT_EXIT
in advance, so preventing 3) from executing unbound requests. The
workers will initially break looping because of getting a signal as they
are threads of the dying/exec()'ing user task.
Cc: stable@vger.kernel.org
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/abfcf8c54cb9e8f7bfbad7e9a0cc5433cc70bdc2.1621781238.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
A previous commit removed the need for this, but overlooked that we no
longer use it at all. Get rid of it.
Fixes: 685fe7feed ("io-wq: eliminate the need for a manager thread")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Do not include private headers and do not frob in internals.
On top of that, while the previous code restores the affinity, it
doesn't ensure the task actually moves there if it was running,
leading to the fun situation that it can be observed running outside
of its allowed mask for potentially significant time.
Use the proper API instead.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/YG7QkiUzlEbW85TU@hirez.programming.kicks-ass.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With using task_work_cancel(), we're potentially canceling task_work
that isn't related to this specific io_wq. Use the newly added
task_work_cancel_match() to ensure that we only remove and cancel work
items that are specific to this io_wq.
Fixes: 685fe7feed ("io-wq: eliminate the need for a manager thread")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
io-wq relies on a manager thread to create/fork new workers, as needed.
But there's really no strong need for it anymore. We have the following
cases that fork a new worker:
1) Work queue. This is done from the task itself always, and it's trivial
to create a worker off that path, if needed.
2) All workers have gone to sleep, and we have more work. This is called
off the sched out path. For this case, use a task_work items to queue
a fork-worker operation.
3) Hashed work completion. Don't think we need to do anything off this
case. If need be, it could just use approach 2 as well.
Part of this change is incrementing the running worker count before the
fork, to avoid cases where we observe we need a worker and then queue
creation of one. Then new work comes in, we fork a new one. That last
queue operation should have waited for the previous worker to come up,
it's quite possible we don't even need it. Hence move the worker running
from before we fork it off to more efficiently handle that case.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Extract a helper for io_work_get_acct() and io_wqe_get_acct() to avoid
duplication.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
WARNING: CPU: 5 PID: 227 at fs/io_uring.c:8578 io_ring_exit_work+0xe6/0x470
RIP: 0010:io_ring_exit_work+0xe6/0x470
Call Trace:
process_one_work+0x206/0x400
worker_thread+0x4a/0x3d0
kthread+0x129/0x170
ret_from_fork+0x22/0x30
INFO: task lfs-openat:2359 blocked for more than 245 seconds.
task:lfs-openat state:D stack: 0 pid: 2359 ppid: 1 flags:0x00000004
Call Trace:
...
wait_for_completion+0x8b/0xf0
io_wq_destroy_manager+0x24/0x60
io_wq_put_and_exit+0x18/0x30
io_uring_clean_tctx+0x76/0xa0
__io_uring_files_cancel+0x1b9/0x2e0
do_exit+0xc0/0xb40
...
Even after io-wq destroy has been issued io-wq worker threads will
continue executing all left work items as usual, and may hang waiting
for I/O that won't ever complete (aka unbounded).
[<0>] pipe_read+0x306/0x450
[<0>] io_iter_do_read+0x1e/0x40
[<0>] io_read+0xd5/0x330
[<0>] io_issue_sqe+0xd21/0x18a0
[<0>] io_wq_submit_work+0x6c/0x140
[<0>] io_worker_handle_work+0x17d/0x400
[<0>] io_wqe_worker+0x2c0/0x330
[<0>] ret_from_fork+0x22/0x30
Cancel all unbounded I/O instead of executing them. This changes the
user visible behaviour, but that's inevitable as io-wq is not per task.
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cd4b543154154cba055cf86f351441c2174d7f71.1617842918.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
task_pid may be large enough to not fit into the left space of
TASK_COMM_LEN-sized buffers and overflow in sprintf. We not so care
about uniqueness, so replace it with safer snprintf().
Reported-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1702c6145d7e1c46fbc382f28334c02e1a3d3994.1617267273.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We go through various hoops to disallow signals for the IO threads, but
there's really no reason why we cannot just allow them. The IO threads
never return to userspace like a normal thread, and hence don't go through
normal signal processing. Instead, just check for a pending signal as part
of the work loop, and call get_signal() to handle it for us if anything
is pending.
With that, we can support receiving signals, including special ones like
SIGSTOP.
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linus correctly points out that this is both unnecessary and generates
much worse code on some archs as going from current to thread_info is
actually backwards - and obviously just wasteful, since the thread_info
is what we care about.
Since io_uring only operates on current for these operations, just use
test_thread_flag() instead. For io-wq, we can further simplify and use
tracehook_notify_signal() to handle the TIF_NOTIFY_SIGNAL work and clear
the flag. The latter isn't an actual bug right now, but it may very well
be in the future if we place other work items under TIF_NOTIFY_SIGNAL.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/io-uring/CAHk-=wgYhNck33YHKZ14mFB5MzTTk8gqXHcfj=RWTAXKwgQJgg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Mark the current task as running if we need to run task_work from the
io-wq threads as part of work handling. If that is the case, then return
as such so that the caller can appropriately loop back and reset if it
was part of a going-to-sleep flush.
Fixes: 3bfe610669 ("io-wq: fork worker threads from original task")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With the freezer using the proper signaling to notify us of when it's
time to freeze a thread, we can re-enable normal freezer usage for the
IO threads. Ensure that SQPOLL, io-wq, and the io-wq manager call
try_to_freeze() appropriately, and remove the default setting of
PF_NOFREEZE from create_io_thread().
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The io-wq threads were already marked as no-freeze, but the manager was
not. On resume, we perpetually have signal_pending() being true, and
hence the manager will loop and spin 100% of the time.
Just mark the tasks created by create_io_thread() as PF_NOFREEZE by
default, and remove any knowledge of it in io-wq and io_uring.
Reported-by: Kevin Locke <kevin@kevinlocke.name>
Tested-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
do_work such as io_wq_submit_work that cancel the work may leave a ref of
req as 1 if we have links. Fix it by call io_run_cancel.
Fixes: 4fb6ac3262 ("io-wq: improve manager/worker handling over exec")
Signed-off-by: yangerkun <yangerkun@huawei.com>
Link: https://lore.kernel.org/r/20210309030410.3294078-1-yangerkun@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Add a simple warning making sure that nobody tries to create a new
manager while we're under IO_WQ_BIT_EXIT. That can potentially happen
due to racy work submission after final put.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: fb3a1f6c74 ("io-wq: have manager wait for all workers to exit")
Signed-off-by: Jens 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: e941894eae ("io-wq: make buffered file write hashed work map per-ctx")
Signed-off-by: Jens 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: Jens Axboe <axboe@kernel.dk>
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: Jens Axboe <axboe@kernel.dk>
The 'err' path should include the hash put, we already grabbed a reference
once we get that far.
Fixes: e941894eae ("io-wq: make buffered file write hashed work map per-ctx")
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we put the io-wq from io_uring, we really want it to exit. Provide
a helper that does that for us. Couple that with not having the manager
hold a reference to the 'wq' and the normal SQPOLL exit will tear down
the io-wq context appropriate.
On the io-wq side, our wq context is per task, so only the task itself
is manipulating ->manager and hence it's safe to check and clear without
any extra locking. We just need to ensure that the manager task stays
around, in case it exits.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We are already freeing the wq struct in both spots, so don't put it and
get it freed twice.
Reported-by: syzbot+7bf785eedca35ca05501@syzkaller.appspotmail.com
Fixes: 4fb6ac3262 ("io-wq: improve manager/worker handling over exec")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The manager waits for the workers, hence the manager is always valid if
workers are running. Now also have wq destroy wait for the manager on
exit, so we now everything is gone.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This is a leftover from a different use cases, it's used to wait for
the manager to startup. Rename it as such.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we're in the process of shutting down the async context, then don't
create new workers if we already have at least the fixed one.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of having to wait separately on workers and manager, just have
the manager wait on the workers. We use an atomic_t for the reference
here, as we need to start at 0 and allow increment from that. Since the
number of workers is naturally capped by the allowed nr of processes,
and that uses an int, there is no risk of overflow.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We need to have our worker count updated before continuing, to avoid
cases where we repeatedly think we need a new worker, but a fork is
already in progress.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
exec will cancel any threads, including the ones that io-wq is using. This
isn't a problem, in fact we'd prefer it to be that way since it means we
know that any async work cancels naturally without having to handle it
proactively.
But it does mean that we need to setup a new manager, as the manager and
workers are gone. Handle this at queue time, and cancel work if we fail.
Since the manager can go away without us noticing, ensure that the manager
itself holds a reference to the 'wq' as well. Rename io_wq_destroy() to
io_wq_put() to reflect that.
In the future we can now simplify exec cancelation handling, for now just
leave it the same.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Before the io-wq thread change, we maintained a hash work map and lock
per-node per-ring. That wasn't ideal, as we really wanted it to be per
ring. But now that we have per-task workers, the hash map ends up being
just per-task. That'll work just fine for the normal case of having
one task use a ring, but if you share the ring between tasks, then it's
considerably worse than it was before.
Make the hash map per ctx instead, which provides full per-ctx buffered
write serialization on hashed writes.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There's a small window between lookup dropping the reference to the
worker and calling wake_up_process() on the worker task, where the worker
itself could have exited. We ensure that the worker struct itself is
valid, but worker->task may very well be gone by the time we issue the
wakeup.
Fix the race by using a completion triggered by the reference going to
zero, and having exit wait for that completion before proceeding.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These races have always been there, they are just more apparent now that
we do early cancel of io-wq when the task exits.
Ensure that the io-wq manager sets task state correctly to not miss
wakeups for task creation. This is important if we get a wakeup after
having marked ourselves as TASK_INTERRUPTIBLE. If we do end up creating
workers, then we flip the state back to running, making the subsequent
schedule() a no-op. Also increment the wq ref count before forking the
thread, to avoid a use-after-free.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We're now just using fork like we would from userspace, so there's no
need to try and impose extra restrictions or accounting on the user
side of things. That's already being done for us. That also means we
don't have to pass in the user_struct anymore, that's correctly inherited
through ->creds on fork.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We want to use this in io_uring proper as well, for the SQPOLL thread.
Rename it from fork_thread() to io_wq_fork_thread(), and make it
available through the io-wq.h header.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of using regular kthread kernel threads, create kernel threads
that are like a real thread that the task would create. This ensures that
we get all the context that we need, without having to carry that state
around. This greatly reduces the code complexity, and the risk of missing
state for a given request type.
With the move away from kthread, we can also dump everything related to
assigned state to the new threads.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We don't support attach anymore, so doesn't make sense to carry the
use_refs reference count. Get rid of it.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When the manager thread starts up, it creates a worker per node for
the given context. Just let these get created dynamically, like we do
for adding further workers.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We hit this case when the task is exiting, and we need somewhere to
do background cleanup of requests. Instead of relying on the io-wq
task manager to do this work for us, just stuff it somewhere where
we can safely run it ourselves directly.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
By default, kernel threads have init_fs and init_files assigned. In the
past, this has triggered security problems, as commands that don't ask
for (and hence don't get assigned) fs/files from the originating task
can then attempt path resolution etc with access to parts of the system
they should not be able to.
Rather than add checks in the fs code for misuse, just set these to
NULL. If we do attempt to use them, then the resulting code will oops
rather than provide access to something that it should not permit.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
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>
io_uring no longer issues full cancelations on the io-wq, so remove any
remnants of this code and the IO_WQ_BIT_CANCEL flag.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Instead of iterating over each request and cancelling it individually in
io_uring_cancel_files(), try to cancel all matching requests and use
->inflight_list only to check if there anything left.
In many cases it should be faster, and we can reuse a lot of code from
task cancellation.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This can't currently happen, but will be possible shortly. Handle missing
files just like we do not being able to grab a needed mm, and mark the
request as needing cancelation.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We correctly set io-wq NUMA node affinities when the io-wq context is
setup, but if an entire node CPU set is offlined and then brought back
online, the per node affinities are broken. Ensure that we set them
again whenever a CPU comes online. This ensures that we always track
the right node affinity. The usual cpuhp notifiers are used to drive it.
Reported-by: Zhang Qiang <qiang.zhang@windriver.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This one was missed in the earlier conversion, should be included like
any of the other IO identity flags. Make sure we restore to RLIM_INIFITY
when dropping the personality again.
Fixes: 98447d65b4 ("io_uring: move io identity items into separate struct")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Make sure the async io-wq workers inherit the loginuid and sessionid from
the original task, and restore them to unset once we're done with the
async work item.
While at it, disable the ability for kernel threads to write to their own
loginuid.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
io-wq contains a pointer to the identity, which we just hold in io_kiocb
for now. This is in preparation for putting this outside io_kiocb. The
only exception is struct files_struct, which we'll need different rules
for to avoid a circular dependency.
No functional changes in this patch.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We solely rely on work->work_flags now, so use that for proper checking
and clearing/dropping of various identity items.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We have a number of bits that decide what context to inherit. Set up
io-wq flags for these instead. This is in preparation for always having
the various members set, but not always needing them for all requests.
No intended functional changes in this patch.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There was an assumption that kthread_create_on_node() would properly set
NUMA affinities in terms of CPUs allowed, but it doesn't. Make sure we
do this when creating an io-wq context on NUMA.
Cc: stable@vger.kernel.org
Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The smart syzbot has found a reproducer for the following issue:
==================================================================
BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline]
BUG: KASAN: use-after-free in io_wqe_inc_running fs/io-wq.c:301 [inline]
BUG: KASAN: use-after-free in io_wq_worker_running+0xde/0x110 fs/io-wq.c:613
Write of size 4 at addr ffff8882183db08c by task io_wqe_worker-0/7771
CPU: 0 PID: 7771 Comm: io_wqe_worker-0 Not tainted 5.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x198/0x1fd lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
check_memory_region_inline mm/kasan/generic.c:186 [inline]
check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
instrument_atomic_write include/linux/instrumented.h:71 [inline]
atomic_inc include/asm-generic/atomic-instrumented.h:240 [inline]
io_wqe_inc_running fs/io-wq.c:301 [inline]
io_wq_worker_running+0xde/0x110 fs/io-wq.c:613
schedule_timeout+0x148/0x250 kernel/time/timer.c:1879
io_wqe_worker+0x517/0x10e0 fs/io-wq.c:580
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Allocated by task 7768:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
kmem_cache_alloc_node_trace+0x17b/0x3f0 mm/slab.c:3594
kmalloc_node include/linux/slab.h:572 [inline]
kzalloc_node include/linux/slab.h:677 [inline]
io_wq_create+0x57b/0xa10 fs/io-wq.c:1064
io_init_wq_offload fs/io_uring.c:7432 [inline]
io_sq_offload_start fs/io_uring.c:7504 [inline]
io_uring_create fs/io_uring.c:8625 [inline]
io_uring_setup+0x1836/0x28e0 fs/io_uring.c:8694
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Freed by task 21:
kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
__kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
__cache_free mm/slab.c:3418 [inline]
kfree+0x10e/0x2b0 mm/slab.c:3756
__io_wq_destroy fs/io-wq.c:1138 [inline]
io_wq_destroy+0x2af/0x460 fs/io-wq.c:1146
io_finish_async fs/io_uring.c:6836 [inline]
io_ring_ctx_free fs/io_uring.c:7870 [inline]
io_ring_exit_work+0x1e4/0x6d0 fs/io_uring.c:7954
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
The buggy address belongs to the object at ffff8882183db000
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 140 bytes inside of
1024-byte region [ffff8882183db000, ffff8882183db400)
The buggy address belongs to the page:
page:000000009bada22b refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2183db
flags: 0x57ffe0000000200(slab)
raw: 057ffe0000000200 ffffea0008604c48 ffffea00086a8648 ffff8880aa040700
raw: 0000000000000000 ffff8882183db000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8882183daf80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8882183db000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8882183db080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8882183db100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8882183db180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
which is down to the comment below,
/* all workers gone, wq exit can proceed */
if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs))
complete(&wqe->wq->done);
because there might be multiple cases of wqe in a wq and we would wait
for every worker in every wqe to go home before releasing wq's resources
on destroying.
To that end, rework wq's refcount by making it independent of the tracking
of workers because after all they are two different things, and keeping
it balanced when workers come and go. Note the manager kthread, like
other workers, now holds a grab to wq during its lifetime.
Finally to help destroy wq, check IO_WQ_BIT_EXIT upon creating worker
and do nothing for exiting wq.
Cc: stable@vger.kernel.org # v5.5+
Reported-by: syzbot+45fa0a195b941764e0f0@syzkaller.appspotmail.com
Reported-by: syzbot+9af99580130003da82b1@syzkaller.appspotmail.com
Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
There are a few operations that are offloaded to the worker threads. In
this case, we lose process context and end up in kthread context. This
results in ios to be not accounted to the issuing cgroup and
consequently end up as issued by root. Just like others, adopt the
personality of the blkcg too when issuing via the workqueues.
For the SQPOLL thread, it will live and attach in the inited cgroup's
context.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
During a context switch the scheduler invokes wq_worker_sleeping() with
disabled preemption. Disabling preemption is needed because it protects
access to `worker->sleeping'. As an optimisation it avoids invoking
schedule() within the schedule path as part of possible wake up (thus
preempt_enable_no_resched() afterwards).
The io-wq has been added to the mix in the same section with disabled
preemption. This breaks on PREEMPT_RT because io_wq_worker_sleeping()
acquires a spinlock_t. Also within the schedule() the spinlock_t must be
acquired after tsk_is_pi_blocked() otherwise it will block on the
sleeping lock again while scheduling out.
While playing with `io_uring-bench' I didn't notice a significant
latency spike after converting io_wqe::lock to a raw_spinlock_t. The
latency was more or less the same.
In order to keep the spinlock_t it would have to be moved after the
tsk_is_pi_blocked() check which would introduce a branch instruction
into the hot path.
The lock is used to maintain the `work_list' and wakes one task up at
most.
Should io_wqe_cancel_pending_work() cause latency spikes, while
searching for a specific item, then it would need to drop the lock
during iterations.
revert_creds() is also invoked under the lock. According to debug
cred::non_rcu is 0. Otherwise it should be moved outside of the locked
section because put_cred_rcu()->free_uid() acquires a sleeping lock.
Convert io_wqe::lock to a raw_spinlock_t.c
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If we don't get and assign the namespace for the async work, then certain
paths just don't work properly (like /dev/stdin, /proc/mounts, etc).
Anything that references the current namespace of the given task should
be assigned for async work on behalf of that task.
Cc: stable@vger.kernel.org # v5.5+
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Don't forget to update wqe->hash_tail after cancelling a pending work
item, if it was hashed.
Cc: stable@vger.kernel.org # 5.7+
Reported-by: Dmitry Shulyak <yashulyak@gmail.com>
Fixes: 86f3cd1b58 ("io-wq: handle hashed writes in chains")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linked requests are hashed, remove a comment stating otherwise. Also
move hash bits to emphasise that we don't carry it through loop
iteration and set it every time.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
RLIMIT_SIZE in needed only for execution from an io-wq context, hence
move all preparations from hot path to io-wq work setup.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's easier to return next work from ->do_work() than
having an in-out argument. Looks nicer and easier to compile.
Also, merge io_wq_assign_next() into its only user.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If a process is going away, io_uring_flush() will cancel only 1
request with a matching pid. Cancel all of them
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This adds support for cancelling all io-wq works matching a predicate.
It isn't used yet, so no change in observable behaviour.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Go all over all pending lists and cancel works there, and only then
try to match running requests. No functional changes here, just a
preparation for bulk cancellation.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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Merge tag 'io_uring-5.8-2020-06-11' of git://git.kernel.dk/linux-block
Pull io_uring fixes from Jens Axboe:
"A few late stragglers in here. In particular:
- Validate full range for provided buffers (Bijan)
- Fix bad use of kfree() in buffer registration failure (Denis)
- Don't allow close of ring itself, it's not fully safe. Making it
fully safe would require making the system call more expensive,
which isn't worth it.
- Buffer selection fix
- Regression fix for O_NONBLOCK retry
- Make IORING_OP_ACCEPT honor O_NONBLOCK (Jiufei)
- Restrict opcode handling for SQ/IOPOLL (Pavel)
- io-wq work handling cleanups and improvements (Pavel, Xiaoguang)
- IOPOLL race fix (Xiaoguang)"
* tag 'io_uring-5.8-2020-06-11' of git://git.kernel.dk/linux-block:
io_uring: fix io_kiocb.flags modification race in IOPOLL mode
io_uring: check file O_NONBLOCK state for accept
io_uring: avoid unnecessary io_wq_work copy for fast poll feature
io_uring: avoid whole io_wq_work copy for requests completed inline
io_uring: allow O_NONBLOCK async retry
io_wq: add per-wq work handler instead of per work
io_uring: don't arm a timeout through work.func
io_uring: remove custom ->func handlers
io_uring: don't derive close state from ->func
io_uring: use kvfree() in io_sqe_buffer_register()
io_uring: validate the full range of provided buffers for access
io_uring: re-set iov base/len for buffer select retry
io_uring: move send/recv IOPOLL check into prep
io_uring: deduplicate io_openat{,2}_prep()
io_uring: do build_open_how() only once
io_uring: fix {SQ,IO}POLL with unsupported opcodes
io_uring: disallow close of ring itself
Some architectures like arm64 and s390 require USER_DS to be set for
kernel threads to access user address space, which is the whole purpose of
kthread_use_mm, but other like x86 don't. That has lead to a huge mess
where some callers are fixed up once they are tested on said
architectures, while others linger around and yet other like io_uring try
to do "clever" optimizations for what usually is just a trivial asignment
to a member in the thread_struct for most architectures.
Make kthread_use_mm set USER_DS, and kthread_unuse_mm restore to the
previous value instead.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: http://lkml.kernel.org/r/20200404094101.672954-7-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Switch the function documentation to kerneldoc comments, and add
WARN_ON_ONCE asserts that the calling thread is a kernel thread and does
not have ->mm set (or has ->mm set in the case of unuse_mm).
Also give the functions a kthread_ prefix to better document the use case.
[hch@lst.de: fix a comment typo, cover the newly merged use_mm/unuse_mm caller in vfio]
Link: http://lkml.kernel.org/r/20200416053158.586887-3-hch@lst.de
[sfr@canb.auug.org.au: powerpc/vas: fix up for {un}use_mm() rename]
Link: http://lkml.kernel.org/r/20200422163935.5aa93ba5@canb.auug.org.au
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [usb]
Acked-by: Haren Myneni <haren@linux.ibm.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Link: http://lkml.kernel.org/r/20200404094101.672954-6-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "improve use_mm / unuse_mm", v2.
This series improves the use_mm / unuse_mm interface by better documenting
the assumptions, and my taking the set_fs manipulations spread over the
callers into the core API.
This patch (of 3):
Use the proper API instead.
Link: http://lkml.kernel.org/r/20200404094101.672954-1-hch@lst.de
These helpers are only for use with kernel threads, and I will tie them
more into the kthread infrastructure going forward. Also move the
prototypes to kthread.h - mmu_context.h was a little weird to start with
as it otherwise contains very low-level MM bits.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: http://lkml.kernel.org/r/20200404094101.672954-1-hch@lst.de
Link: http://lkml.kernel.org/r/20200416053158.586887-1-hch@lst.de
Link: http://lkml.kernel.org/r/20200404094101.672954-5-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
io_uring is the only user of io-wq, and now it uses only io-wq callback
for all its requests, namely io_wq_submit_work(). Instead of storing
work->runner callback in each instance of io_wq_work, keep it in io-wq
itself.
pros:
- reduces io_wq_work size
- more robust -- ->func won't be invalidated with mem{cpy,set}(req)
- helps other work
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If the original task is (or has) exited, then the task work will not get
queued properly. Allow for using the io-wq manager task to queue this
work for execution, and ensure that the io-wq manager notices and runs
this work if woken up (or exiting).
Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We always punt async buffered writes to an io-wq helper, as the core
kernel does not have IOCB_NOWAIT support for that. Most buffered async
writes complete very quickly, as it's just a copy operation. This means
that doing multiple locking roundtrips on the shared wqe lock for each
buffered write is wasteful. Additionally, buffered writes are hashed
work items, which means that any buffered write to a given file is
serialized.
Keep identicaly hashed work items contiguously in @wqe->work_list, and
track a tail for each hash bucket. On dequeue of a hashed item, splice
all of the same hash in one go using the tracked tail. Until the batch
is done, the caller doesn't have to synchronize with the wqe or worker
locks again.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
After io_assign_current_work() of a linked work, it can be decided to
offloaded to another thread so doing io_wqe_enqueue(). However, until
next io_assign_current_work() it can be cancelled, that isn't handled.
Don't assign it, if it's not going to be executed.
Fixes: 60cf46ae60 ("io-wq: hash dependent work")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Enable io-wq hashing stuff for dependent works simply by re-enqueueing
such requests.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
It's a preparation patch removing io_wq_enqueue_hashed(), which
now should be done by io_wq_hash_work() + io_wq_enqueue().
Also, set hash value for dependant works, and do it as late as possible,
because req->file can be unavailable before. This hash will be ignored
by io-wq.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens 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: Andres Freund <andres@anarazel.de>
Signed-off-by: Jens 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: Jens 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: Jens 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: Jens 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: Jens 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: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
