linux.git/io_uring/eventfd.c, branch v6.13

io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period

2025-01-09T14:16:45+00:00

io_eventfd_do_signal() is invoked from an RCU callback, but when
dropping the reference to the io_ev_fd, it calls io_eventfd_free()
directly if the refcount drops to zero. This isn't correct, as any
potential freeing of the io_ev_fd should be deferred another RCU grace
period.

Just call io_eventfd_put() rather than open-code the dec-and-test and
free, which will correctly defer it another RCU grace period.

Fixes: 21a091b970cd ("io_uring: signal registered eventfd to process deferred task work")
Reported-by: Jann Horn 
Cc: stable@vger.kernel.org
Tested-by: Li Zetao 
Reviewed-by: Li Zetao
Reviewed-by: Prasanna Kumar T S M 
Signed-off-by: Jens Axboe

io_uring/eventfd: move ctx->evfd_last_cq_tail into io_ev_fd

2024-10-29T19:43:26+00:00

Everything else about the io_uring eventfd support is nicely kept
private to that code, except the cached_cq_tail tracking. With
everything else in place, move io_eventfd_flush_signal() to using
the ev_fd grab+release helpers, which then enables the direct use of
io_ev_fd for this tracking too.

Link: https://lore.kernel.org/r/20240921080307.185186-7-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: abstract out ev_fd grab + release helpers

2024-10-29T19:43:26+00:00

In preparation for needing the ev_fd grabbing (and releasing) from
another path, abstract out two helpers for that.

Link: https://lore.kernel.org/r/20240921080307.185186-6-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: move trigger check into a helper

2024-10-29T19:43:26+00:00

It's a bit hard to read what guards the triggering, move it into a
helper and add a comment explaining it too. This additionally moves
the ev_fd == NULL check in there as well.

Link: https://lore.kernel.org/r/20240921080307.185186-5-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: move actual signaling part into separate helper

2024-10-29T19:43:26+00:00

In preparation for using this from multiple spots, move the signaling
into a helper.

Link: https://lore.kernel.org/r/20240921080307.185186-4-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: check for the need to async notifier earlier

2024-10-29T19:43:26+00:00

It's not necessary to do this post grabbing a reference. With that, we
can drop the out goto path as well.

Link: https://lore.kernel.org/r/20240921080307.185186-3-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: abstract out ev_fd put helper

2024-10-29T19:43:26+00:00

We call this in two spot, have a helper for it. In preparation for
extending this part.

Link: https://lore.kernel.org/r/20240921080307.185186-2-axboe@kernel.dk
Signed-off-by: Jens Axboe

io_uring/eventfd: move refs to refcount_t

2024-09-08T22:43:57+00:00

atomic_t for the struct io_ev_fd references and there are no issues with
it. While the ref getting and putting for the eventfd code is somewhat
performance critical for cases where eventfd signaling is used (news
flash, you should not...), it probably doesn't warrant using an atomic_t
for this. Let's just move to it to refcount_t to get the added
protection of over/underflows.

Link: https://lore.kernel.org/lkml/202409082039.hnsaIJ3X-lkp@intel.com/
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202409082039.hnsaIJ3X-lkp@intel.com/
Signed-off-by: Jens Axboe

io_uring: add new line after variable declaration

2024-09-02T15:39:57+00:00

Fixes checkpatch warning

Signed-off-by: Anuj Gupta 
Link: https://lore.kernel.org/r/20240902062134.136387-2-anuj20.g@samsung.com
Signed-off-by: Jens Axboe

io_uring/eventfd: move eventfd handling to separate file

2024-06-16T20:54:55+00:00

This is pretty nicely abstracted already, but let's move it to a separate
file rather than have it in the main io_uring file. With that, we can
also move the io_ev_fd struct and enum out of global scope.

Signed-off-by: Jens Axboe