Smatch complains that:

smatch warnings:
io_uring/rsrc.c:1262 io_sqe_buffer_register() error: uninitialized symbol 'folio'.

'folio' may be used uninitialized, which can happen if we end up with a
single page mapped. Ensure that we clear folio to NULL at the top so
it's always set.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/202302241432.YML1CD5C-lkp@intel.com/


Signed-off-by: Jens Axboe <axboe@kernel.dk>

When registering huge pages, internally io_uring will split them into
many PAGE_SIZE bvec entries. That's bad for performance as drivers need
to eventually dma-map the data and will do it individually for each bvec
entry. Coalesce huge pages into one large bvec.

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

Iterating within the first bvec entry should be essentially free, but we
use iov_iter_advance() for that, which shows up in benchmark profiles
taking up to 0.5% of CPU. Replace it with a hand coded version.

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

If two or more mappings go back to back to each other they can be passed
into io_uring to be registered as a single registered buffer. That would
even work if mappings came from different sources, e.g. it's possible to
mix in this way anon pages and pages from shmem or hugetlb. That is not
a problem but it'd rather be less prone if we forbid such mixing.

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

io_import_fixed() supports offsets, but "may not" means the opposite.
Replace it with "might not" so the comments rather speaks about
possible cases.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Link: https://lore.kernel.org/r/5b5f79958456caa6dc532f6205f75f224b232c81.1676902343.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use the bvec_set_page helper to initialize a bvec.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20230203150634.3199647-19-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use task_work for completing rsrc removals, it'll be needed later for
spinlock optimisations.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cbba5d53a11ee6fc2194dacea262c1d733c8b529.1670384893.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

There is no need to reinit data and install a new rsrc node every time
we get a task_work, it's detrimental, just execute it and conitnue
waiting.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/3895d3344164cd9b3a0bbb24a6e357e20a13434b.1669821213.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Do a little bit of refactoring of io_rsrc_ref_quiesce(), flatten the
data refs checks and so get rid of a conditional weird unlock-else-break
construct.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/d21283e9f88a77612c746ed526d86fe3bfb58a70.1669821213.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

The only call sites which would not allow overflow are also call sites
which would use the io_aux_cqe as they care about ordering.

So remove this parameter from io_post_aux_cqe.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221124093559.3780686-9-dylany@meta.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Running task work when not needed can unnecessarily delay
operations. Specifically IORING_SETUP_DEFER_TASKRUN tries to avoid running
task work until the user requests it. Therefore do not run it in
io_uring_register any more.

The one catch is that io_rsrc_ref_quiesce expects it to have run in order
to process all outstanding references, and so reorder it's loop to do this.

Signed-off-by: Dylan Yudaken <dylany@meta.com>
Link: https://lore.kernel.org/r/20221107123349.4106213-1-dylany@meta.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

THe lifetime of SCM'ed files is bound to ring_sock, which is destroyed
strictly after we're done with registered file tables. This means there
is no need for the FFS_SCM hack, which was not available on 32-bit builds
anyway.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/984226a1045adf42dc35d8bd7fb5a8bbfa472ce1.1665891182.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Instead of putting io_uring's registered files in unix_gc() we want it
to be done by io_uring itself. The trick here is to consider io_uring
registered files for cycle detection but not actually putting them down.
Because io_uring can't register other ring instances, this will remove
all refs to the ring file triggering the ->release path and clean up
with io_ring_ctx_free().

Cc: stable@vger.kernel.org
Fixes: 6b06314c ("io_uring: add file set registration")
Reported-and-tested-by: David Bouman <dbouman03@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[axboe: add kerneldoc comment to skb, fold in skb leak fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Allow deferring async tasks until the user calls io_uring_enter(2) with
the IORING_ENTER_GETEVENTS flag. Enable this mode with a flag at
io_uring_setup time. This functionality requires that the later
io_uring_enter will be called from the same submission task, and therefore
restrict this flag to work only when IORING_SETUP_SINGLE_ISSUER is also
set.

Being able to hand pick when tasks are run prevents the problem where
there is current work to be done, however task work runs anyway.

For example, a common workload would obtain a batch of CQEs, and process
each one. Interrupting this to additional taskwork would add latency but
not gain anything. If instead task work is deferred to just before more
CQEs are obtained then no additional latency is added.

The way this is implemented is by trying to keep task work local to a
io_ring_ctx, rather than to the submission task. This is required, as the
application will want to wake up only a single io_ring_ctx at a time to
process work, and so the lists of work have to be kept separate.

This has some other benefits like not having to check the task continually
in handle_tw_list (and potentially unlocking/locking those), and reducing
locks in the submit & process completions path.

There are networking cases where using this option can reduce request
latency by 50%. For example a contrived example using [1] where the client
sends 2k data and receives the same data back while doing some system
calls (to trigger task work) shows this reduction. The reason ends up
being that if sending responses is delayed by processing task work, then
the client side sits idle. Whereas reordering the sends first means that
the client runs it's workload in parallel with the local task work.

[1]:
Using https://github.com/DylanZA/netbench/tree/defer_run


Client:
./netbench  --client_only 1 --control_port 10000 --host <host> --tx "epoll --threads 16 --per_thread 1 --size 2048 --resp 2048 --workload 1000"
Server:
./netbench  --server_only 1 --control_port 10000  --rx "io_uring --defer_taskrun 0 --workload 100"   --rx "io_uring  --defer_taskrun 1 --workload 100"

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220830125013.570060-5-dylany@fb.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

This reverts commit 4379d5f1.

We removed notification flushing, also cleanup uapi preparation changes
to not pollute it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/89edc3905350f91e1b6e26d9dbf42ee44fd451a2.1662027856.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

This reverts commit 492dddb4.

Soon we won't have the very notion of notification flushing, so remove
notification flushing requests.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8850334ca56e65b413cb34fd158db81d7b2865a3.1662027856.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

We need to make sure (at build time) that struct io_cmd_data is not
casted to a structure that's larger.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Link: https://lore.kernel.org/r/c024cdf25ae19fc0319d4180e2298bade8ed17b8.1660201408.git.metze@samba.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Make network page accounting more consistent with how buffer
registration is working, i.e. account all memory to ctx->user.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4aacfe64bbb81b27f9ecf5d5c219c69a07e5aa56.1658742118.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Overlay notification control onto IORING_OP_RSRC_UPDATE (former
IORING_OP_FILES_UPDATE). It allows to flush a range of zc notifications
from slots with indexes [sqe->off, sqe->off+sqe->len). If sqe->arg is
not zero, it also copies sqe->arg as a new tag for all flushed
notifications.

Note, it doesn't flush a notification of a slot if there was no requests
attached to it (since last flush or registration).

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/df13e2363400682a73dd9e71c3b990b8d1ff0333.1657643355.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

IORING_OP_FILES_UPDATE will be a more generic opcode serving different
resource types, rename it into IORING_OP_RSRC_UPDATE and add subtype
handling.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/0a907133907d9af3415a8a7aa1802c6aa97c03c6.1657643355.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use atomic_long_try_cmpxchg instead of
atomic_long_cmpxchg (*ptr, old, new) == old in __io_account_mem.
x86 CMPXCHG instruction returns success in ZF flag, so this
change saves a compare after cmpxchg (and related move
instruction in front of cmpxchg).

Also, atomic_long_try_cmpxchg implicitly assigns old *ptr value
to "old" when cmpxchg fails, enabling further code simplifications.

No functional change intended.

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

Some use cases of io_post_aux_cqe would not want to overflow as is, but
might want to change the flags/result. For example multishot receive
requires in order CQE, and so if there is an overflow it would need to
stop receiving until the overflow is taken care of.

Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220630091231.1456789-8-dylany@fb.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

From recently io_uring provides an option to allocate a file index for
operation registering fixed files. However, it's utterly unusable with
mixed approaches when for a part of files the userspace knows better
where to place it, as it may race and users don't have any sane way to
pick a slot and hoping it will not be taken.

Let the userspace to register a range of fixed file slots in which the
auto-allocation happens. The use case is splittting the fixed table in
two parts, where on of them is used for auto-allocation and another for
slot-specified operations.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/66ab0394e436f38437cf7c44676e1920d09687ad.1656154403.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Put it with the filetable code, which is where it belongs. While doing
so, have the helpers take a ctx rather than an io_kiocb. It doesn't make
sense to use a request, as it's not an operation on the request itself.
It applies to the ring itself.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Move io_import_fixed() into rsrc.c where it belongs.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/4d5becb21f332b4fef6a7cedd6a50e65e2371630.1655684496.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io_uring.h already includes io_uring_types.h, no need to
include it every time. Kill it in a bunch of places, it prepares us for
following patches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/94d8c943fbe0ef949981c508ddcee7fc1c18850f.1655384063.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Deduplicate some code and add a helper for filling an aux CQE, locking
and notification.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/b7c6557c8f9dc5c4cfb01292116c682a0ff61081.1655455613.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

The default (i.e. empty) state of register buffer is dummy_ubuf, so set
it to dummy on init instead of NULL.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c5456aecf03d9627fbd6e65e100e2b5293a6151e.1655310733.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Jens Axboe <axboe@kernel.dk>