ocfs2: fix uninitialized value in ocfs2_file_read_iter()

In the Linux kernel, the following vulnerability has been resolved: ocfs2: fix uninitialized value in ocfs2_file_read_iter() Syzbot has reported the following KMSAN splat: BUG: KMSAN: uninit-value in ocfs2_file_read_iter+0x9a4/0xf80 ocfs2_file_read_iter+0x9a4/0xf80 __io_read+0x8d4/0x20f0 io_read+0x3e/0xf0 io_issue_sqe+0x42b/0x22c0 io_wq_submit_work+0xaf9/0xdc0 io_worker_handle_work+0xd13/0x2110 io_wq_worker+0x447/0x1410 ret_from_fork+0x6f/0x90 ret_from_fork_asm+0x1a/0x30 Uninit was created at: __alloc_pages_noprof+0x9a7/0xe00 alloc_pages_mpol_noprof+0x299/0x990 alloc_pages_noprof+0x1bf/0x1e0 allocate_slab+0x33a/0x1250 ___slab_alloc+0x12ef/0x35e0 kmem_cache_alloc_bulk_noprof+0x486/0x1330 __io_alloc_req_refill+0x84/0x560 io_submit_sqes+0x172f/0x2f30 __se_sys_io_uring_enter+0x406/0x41c0 __x64_sys_io_uring_enter+0x11f/0x1a0 x64_sys_call+0x2b54/0x3ba0 do_syscall_64+0xcd/0x1e0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Since an instance of 'struct kiocb' may be passed from the block layer with 'private' field uninitialized, introduce 'ocfs2_iocb_init_rw_locked()' and use it from where 'ocfs2_dio_end_io()' might take care, i.e. in 'ocfs2_file_read_iter()' and 'ocfs2_file_write_iter()'.