WARNING: CPU: 0 PID: 10242 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Call Trace:
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 io_put_req fs/io_uring.c:2140 [inline]
 io_queue_linked_timeout fs/io_uring.c:6300 [inline]
 __io_queue_sqe+0xbef/0xec0 fs/io_uring.c:6354
 io_submit_sqe fs/io_uring.c:6534 [inline]
 io_submit_sqes+0x2bbd/0x7c50 fs/io_uring.c:6660
 __do_sys_io_uring_enter fs/io_uring.c:9240 [inline]
 __se_sys_io_uring_enter+0x256/0x1d60 fs/io_uring.c:9182

io_link_timeout_fn() should put only one reference of the linked timeout
request, however in case of racing with the master request's completion
first io_req_complete() puts one and then io_put_req_deferred() is
called.

Cc: stable@vger.kernel.org # 5.12+
Fixes: 9ae1f8dd ("io_uring: fix inconsistent lock state")
Reported-by: syzbot+a2910119328ce8e7996f@syzkaller.appspotmail.com
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ff51018ff29de5ffa76f09273ef48cb24c720368.1620417627.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Read and write operations are capped to MAX_RW_COUNT. Some read ops rely on
that limit, and that is not guaranteed by the IORING_OP_PROVIDE_BUFFERS.

Truncate those lengths when doing io_add_buffers, so buffer addresses still
use the uncapped length.

Also, take the chance and change struct io_buffer len member to __u32, so
it matches struct io_provide_buffer len member.

This fixes CVE-2021-3491, also reported as ZDI-CAN-13546.

Fixes: ddf0322d ("io_uring: add IORING_OP_PROVIDE_BUFFERS")
Reported-by: Billy Jheng Bing-Jhong (@st424204)
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

unreferenced object 0xffff8881123bf0a0 (size 32):
comm "syz-executor557", pid 8384, jiffies 4294946143 (age 12.360s)
backtrace:
[<ffffffff81469b71>] kmalloc_node include/linux/slab.h:579 [inline]
[<ffffffff81469b71>] kvmalloc_node+0x61/0xf0 mm/util.c:587
[<ffffffff815f0b3f>] kvmalloc include/linux/mm.h:795 [inline]
[<ffffffff815f0b3f>] kvmalloc_array include/linux/mm.h:813 [inline]
[<ffffffff815f0b3f>] kvcalloc include/linux/mm.h:818 [inline]
[<ffffffff815f0b3f>] io_rsrc_data_alloc+0x4f/0xc0 fs/io_uring.c:7164
[<ffffffff815f26d8>] io_sqe_buffers_register+0x98/0x3d0 fs/io_uring.c:8383
[<ffffffff815f84a7>] __io_uring_register+0xf67/0x18c0 fs/io_uring.c:9986
[<ffffffff81609222>] __do_sys_io_uring_register fs/io_uring.c:10091 [inline]
[<ffffffff81609222>] __se_sys_io_uring_register fs/io_uring.c:10071 [inline]
[<ffffffff81609222>] __x64_sys_io_uring_register+0x112/0x230 fs/io_uring.c:10071
[<ffffffff842f616a>] do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
[<ffffffff84400068>] entry_SYSCALL_64_after_hwframe+0x44/0xae

Fix data->tags memory leak, through io_rsrc_data_free() to release
data memory space.

Reported-by: syzbot+0f32d05d8b6cd8d7ea3e@syzkaller.appspotmail.com
Signed-off-by: NZqiang <qiang.zhang@windriver.com>
Link: https://lore.kernel.org/r/20210430082515.13886-1-qiang.zhang@windriver.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Currently the -EINVAL error return path is leaking memory allocated
to data. Fix this by not returning immediately but instead setting
the error return variable to -EINVAL and breaking out of the loop.

Kudos to Pavel Begunkov for suggesting a correct fix.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Reviewed-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/20210429104602.62676-1-colin.king@canonical.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

io_rsrc_node_switch_start() can fail, don't forget to check returned
error code.

Reported-by: syzbot+a4715dd4b7c866136f79@syzkaller.appspotmail.com
Fixes: eae071c9 ("io_uring: prepare fixed rw for dynanic buffers")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c4c06e2f3f0c8e43bd8d0a266c79055bcc6b6e60.1619693112.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Allow empty reg buffer slots any request using which should fail. This
allows users to not register all buffers in advance, but do it lazily
and/or on demand via updates. That is achieved by setting iov_base and
iov_len to zero for registration and/or buffer updates. Empty buffer
can't have a non-zero tag.

Implementation details: to not add extra overhead to io_import_fixed(),
create a dummy buffer crafted to fail any request using it, and set it
to all empty buffer slots.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7e95e4d700082baaf010c648c72ac764c9cc8826.1619611868.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add a couple of BUILD_BUG_ON() checking some rsrc uapi structs and SQE
flags.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ff960df4d5026b9fb5bfd80994b9d3667d3926da.1619536280.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

CQE flags take one byte that we store in req->flags together with other
REQ_F_* internal flags. CQE flags are copied directly into req and then
verified that requires some handling on failures, e.g. to make sure that
that copy doesn't set some of the internal flags.

Move all internal flags to take bits after the first byte, so we don't
need extra handling and make it safer overall.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b8b5b02d1ab9d786fcc7db4a3fe86db6b70b8987.1619536280.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Resource emitted CQEs are not bound to requests, so fix up counters used
for DRAIN/defer logic.

Fixes: b60c8dce ("io_uring: preparation for rsrc tagging")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2b32f5f0a40d5928c3466d028f936e167f0654be.1619536280.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Now that we have multishot poll requests, one SQE can emit multiple
CQEs. given below example:
    sqe0(multishot poll)-->sqe1-->sqe2(drain req)
sqe2 is designed to issue after sqe0 and sqe1 completed, but since sqe0
is a multishot poll request, sqe2 may be issued after sqe0's event
triggered twice before sqe1 completed. This isn't what users leverage
drain requests for.
Here the solution is to wait for multishot poll requests fully
completed.
To achieve this, we should reconsider the req_need_defer equation, the
original one is:

    all_sqes(excluding dropped ones) == all_cqes(including dropped ones)

This means we issue a drain request when all the previous submitted
SQEs have generated their CQEs.
Now we should consider multishot requests, we deduct all the multishot
CQEs except the cancellation one, In this way a multishot poll request
behave like a normal request, so:
    all_sqes == all_cqes - multishot_cqes(except cancellations)

Here we introduce cq_extra for it.
Signed-off-by: NHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1618298439-136286-1-git-send-email-haoxu@linux.alibaba.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

syzkaller identified KASAN: null-ptr-deref Write in
io_uring_cancel_sqpoll.

io_uring_cancel_sqpoll is called by io_sq_thread before calling
io_uring_alloc_task_context. This leads to current->io_uring being NULL.
io_uring_cancel_sqpoll should not have to deal with threads where
current->io_uring is NULL.

In order to cast a wider safety net, perform input sanitisation directly
in io_uring_cancel_sqpoll and return for NULL value of current->io_uring.
This is safe since if current->io_uring isn't set, then there's no way
for the task to have submitted any requests.

Reported-by: syzbot+be51ca5a4d97f017cd50@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: NPalash Oswal <hello@oswalpalash.com>
Link: https://lore.kernel.org/r/20210427125148.21816-1-hello@oswalpalash.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

io_import_fixed() doesn't expect a registered buffer slot to be NULL and
would fail stumbling on it. We don't allow it, but if during
__io_sqe_buffers_update() rsrc removal succeeds but following register
fails, we'll get such a situation.

Do it atomically and don't remove buffers until we sure that a new one
can be set.

Fixes: 634d00df ("io_uring: add full-fledged dynamic buffers support")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/830020f9c387acddd51962a3123b5566571b8c6d.1619446608.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

All sqpoll rings (even sharing sqpoll task) are currently dead bound
to the task that created them, iow when owner task dies it kills all
its SQPOLL rings and their inflight requests via task_work infra. It's
neither the nicist way nor the most convenient as adds extra
locking/waiting and dependencies.

Leave it alone and rely on SIGKILL being delivered on its thread group
exit, so there are only two cases left:

1) thread group is dying, so sqpoll task gets a signal and exit itself
   cancelling all requests.

2) an sqpoll ring is dying. Because refs_kill() is called the sqpoll not
   going to submit any new request, and that's what we need. And
   io_ring_exit_work() will do all the cancellation itself before
   actually killing ctx, so sqpoll doesn't need to worry about it.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3cd7f166b9c326a2c932b70e71a655b03257b366.1619389911.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

After closing an SQPOLL ring, io_ring_exit_work() kicks in and starts
doing cancellations via io_uring_try_cancel_requests(). It will go
through io_uring_try_cancel_iowq(), which uses ctx->tctx_list, but as
SQPOLL task don't have a ctx note, its io-wq won't be reachable and so
is left not cancelled.

It will eventually cancelled when one of the tasks dies, but if a thread
group survives for long and changes rings, it will spawn lots of
unreclaimed resources and live locked works.

Cancel SQPOLL task's io-wq separately in io_ring_exit_work().

Cc: stable@vger.kernel.org
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/a71a7fe345135d684025bb529d5cb1d8d6b46e10.1619389911.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

The variable up.resv is not initialized and is being checking for a
non-zero value in the call to _io_register_rsrc_update. Fix this by
explicitly setting the variable to 0.

Addresses-Coverity: ("Uninitialized scalar variable)"
Fixes: c3bdad02 ("io_uring: add generic rsrc update with tags")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210426094735.8320-1-colin.king@canonical.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Now we allocate io_mapped_ubuf instead of bvec, so we clearly have to
check its address after allocation.

Fixes: 41edf1a5 ("io_uring: keep table of pointers to ubufs")
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d28eb1bc4384284f69dbce35b9f70c115ff6176f.1619392565.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

This is done by create_io_thread() now.
Signed-off-by: NStefan Metzmacher <metze@samba.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

we shall update sq_thread_idle anytime we do ctx deletion from ctx_list

Fixes:734551df ("io_uring: fix shared sqpoll cancellation hangs")
Signed-off-by: NHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619256380-236460-1-git-send-email-haoxu@linux.alibaba.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Hook buffers into all rsrc infrastructure, including tagging and
updates.
Suggested-by: NBijan Mottahedeh <bijan.mottahedeh@oracle.com>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/119ed51d68a491dae87eb55fb467a47870c86aad.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Apply fixed_rsrc functionality for fixed buffers support.
Signed-off-by: NBijan Mottahedeh <bijan.mottahedeh@oracle.com>
[rebase, remove multi-level tables, fix unregister on exit]
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/17035f4f75319dc92962fce4fc04bc0afb5a68dc.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

With dynamic buffer updates, registered buffers in the table may change
at any moment. First of all we want to prevent future races between
updating and importing (i.e. io_import_fixed()), where the latter one
may happen without uring_lock held, e.g. from io-wq.

Save the first loaded io_mapped_ubuf buffer and reuse.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/21a2302d07766ae956640b6f753292c45200fe8f.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Instead of keeping a table of ubufs convert them into pointers to ubuf,
so we can atomically read one pointer and be sure that the content of
ubuf won't change.

Because it was already dynamically allocating imu->bvec, throw both
imu and bvec into a single structure so they can be allocated together.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b96efa4c5febadeccf41d0e849ac099f4c83b0d3.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add IORING_REGISTER_RSRC_UPDATE, which also supports passing in rsrc
tags. Implement it for registered files.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d4dc66df204212f64835ffca2c4eb5e8363f2f05.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add a new io_uring_register() opcode for rsrc registeration. Instead of
accepting a pointer to resources, fds or iovecs, it @arg is now pointing
to a struct io_uring_rsrc_register, and the second argument tells how
large that struct is to make it easily extendible by adding new fields.

All that is done mainly to be able to pass in a pointer with tags. Pass
it in and enable CQE posting for file resources. Doesn't support setting
tags on update yet.

A design choice made here is to not post CQEs on rsrc de-registration,
but only when we updated-removed it by rsrc dynamic update.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c498aaec32a4bb277b2406b9069662c02cdda98c.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

As resources are getting more support and common parts, it'll be more
convenient to index resources and use it for indexing.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f0be63e9310212d5601d36277c2946ff7a040485.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Extract some common parts for rsrc update, will be used reg buffers
support dynamic (i.e. quiesce-lee) managing.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b49c3ff6b9ff0e530295767604fe4de64d349e04.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

We need a way to notify userspace when a lazily removed resource
actually died out. This will be done by associating a tag, which is u64
exactly like req->user_data, with each rsrc (e.g. buffer of file). A CQE
will be posted once a resource is actually put down.

Tag 0 is a special value set by default, for whcih it don't generate an
CQE, so providing the old behaviour.

Don't expose it to the userspace yet, but prepare internally, allocate
buffers, add all posting hooks, etc.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2e6beec5eabe7216bb61fb93cdf5aaf65812a9b0.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Make __io_cqring_fill_event() agnostic of struct io_kiocb, pass all the
data needed directly into it. Will be used to post rsrc removal
completions, which don't have an associated request.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c9b8da9e42772db2033547dfebe479dc972a0f2c.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Add io_rsrc_data_free() helper for destroying rsrc_data, easier for
search and the function will get more stuff to destroy shortly.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/562d1d53b5ff184f15b8949a63d76ef19c4ba9ec.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

A preparation patch moving __io_sqe_files_unregister() definition closer
to other "files" functions without any modification.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/95caf17fe837e67bd1f878395f07049062a010d4.1619356238.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

do this to avoid race below:

         userspace                         kernel

                               |  check sqring and iopoll_list
submit sqe                     |
check IORING_SQ_NEED_WAKEUP    |
(which is not set)    |        |
                               |  set IORING_SQ_NEED_WAKEUP
wait cqe                       |  schedule(never wakeup again)
Signed-off-by: NHao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/1619018351-75883-1-git-send-email-haoxu@linux.alibaba.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Just a bit of code tossing in io_sq_offload_create(), so it looks a bit
better. No functional changes.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/939776f90de8d2cdd0414e1baa29c8ec0926b561.1618916549.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Put sq_creds as a part of io_ring_ctx_free(), it's easy to miss doing it
in io_sq_thread_finish(), especially considering past mistakes related
to ring creation failures.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3becb1866467a1de82a97345a0a90d7fb8ff875e.1618916549.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

REQ_F_INFLIGHT deaccounting doesn't do any spinlocking or resource
freeing anymore, so it's safe to move it into the normal cleanup flow,
i.e. into io_clean_op(), so making it cleaner.

Also move io_req_needs_clean() to be first in io_dismantle_req() so it
doesn't reload req->flags.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/90653a3a5de4107e3a00536fa4c2ea5f2c38a4ac.1618916549.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

[  736.982891] INFO: task iou-sqp-4294:4295 blocked for more than 122 seconds.
[  736.982897] Call Trace:
[  736.982901]  schedule+0x68/0xe0
[  736.982903]  io_uring_cancel_sqpoll+0xdb/0x110
[  736.982908]  io_sqpoll_cancel_cb+0x24/0x30
[  736.982911]  io_run_task_work_head+0x28/0x50
[  736.982913]  io_sq_thread+0x4e3/0x720

We call io_uring_cancel_sqpoll() one by one for each ctx either in
sq_thread() itself or via task works, and it's intended to cancel all
requests of a specified context. However the function uses per-task
counters to track the number of inflight requests, so it counts more
requests than available via currect io_uring ctx and goes to sleep for
them to appear (e.g. from IRQ), that will never happen.

Cancel a bit more than before, i.e. all ctxs that share sqpoll
and continue to use shared counters. Don't forget that we should not
remove ctx from the list before running that task_work sqpoll-cancel,
otherwise the function wouldn't be able to find the context and will
hang.
Reported-by: NJoakim Hassila <joj@mac.com>
Reported-by: NJens Axboe <axboe@kernel.dk>
Fixes: 37d1e2e3 ("io_uring: move SQPOLL thread io-wq forked worker")
Cc: stable@vger.kernel.org
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1bded7e6c6b32e0bae25fce36be2868e46b116a0.1618752958.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

SQPOLL task won't submit requests for a context that is currently dying,
so no need to remove ctx from sqd_list prior the main loop of
io_ring_exit_work(). Kill it, will be removed by io_sq_thread_finish()
and only brings confusion and lockups.

Cc: stable@vger.kernel.org
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f220c2b786ba0f9499bebc9f3cd9714d29efb6a5.1618752958.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Move restriction checks of __io_uring_register() before quiesce, saves
from waiting for requests in fail case and simplifies the code a bit.
Also add array_index_nospec() for safety
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/88d7913c9280ee848fdb7b584eea37a465391cee.1618488258.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Colin reported before possible overflow and sign extension problems in
io_provide_buffers_prep(). As Linus pointed out previous attempt did nothing
useful, see d81269fe ("io_uring: fix provide_buffers sign extension").

Do that with help of check_<op>_overflow helpers. And fix struct
io_provide_buf::len type, as it doesn't make much sense to keep it
signed.
Reported-by: NColin Ian King <colin.king@canonical.com>
Fixes: efe68c1c ("io_uring: validate the full range of provided buffers for access")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/46538827e70fce5f6cdb50897cff4cacc490f380.1618488258.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Don't fail submission attempts if there are CQEs in the overflow
backlog, but give away the decision making to the userspace. It
might be very inconvenient to the userspace, especially if
submission and completion are done by different threads.

We can remove it because of recent changes, where requests
are now not locked by the backlog, backlog entries are allocated
separately, so they take less space and cgroup accounted.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

A hand-edit while applying this patch on top of a new base resulted in
a reverted check for re-issue, resulting in spurious -EAGAIN errors.

Fixes: 8c130827 ("io_uring: don't alter iopoll reissue fail ret code")
Signed-off-by: NJens Axboe <axboe@kernel.dk>