fs: Fix possible use-after-free with AIO

fs: Fix possible use-after-free with AIO

Running AIO is pinning inode in memory using file reference. Once AIO
is completed using aio_complete(), file reference is put and inode can
be freed from memory. So we have to be sure that calling aio_complete()
is the last thing we do with the inode.

CC: Christoph Hellwig <[email protected]>
CC: Jens Axboe <[email protected]>
CC: Jeff Moyer <[email protected]>
CC: [email protected]
Acked-by: Jeff Moyer <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Al Viro <[email protected]>