aio: fix io_destroy() regression by using call_rcu()
There was a regression introduced by
36f5588 ("aio: refcounting cleanup"),
reported by Jens Axboe - the refcounting cleanup switched to using RCU in
the shutdown path, but the synchronize_rcu() was done in the context of
the io_destroy() syscall greatly increasing the time it could block.
This patch switches it to call_rcu() and makes shutdown asynchronous (more
asynchronous than it was originally; before the refcount changes
io_destroy() would still wait on pending kiocbs).
Note that there's a global quota on the max outstanding kiocbs, and that
quota must be manipulated synchronously; otherwise io_setup() could return
-EAGAIN when there isn't quota available, and userspace won't have any way
of waiting until shutdown of the old kioctxs has finished (besides busy
looping).
So we release our quota before kioctx shutdown has finished, which should
be fine since the quota never corresponded to anything real anyways.
Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reported-by: Jens Axboe <axboe@kernel.dk>
Tested-by: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Tested-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>