io_uring: fix incorrect unlikely() usage in io_waitid_prep()

JIRA: https://issues.redhat.com/browse/RHEL-105612

commit 4ec703e
Author: Alok Tiwari <alok.a.tiwari@oracle.com>
Date:   Sat Oct 18 12:32:54 2025 -0700

    io_uring: fix incorrect unlikely() usage in io_waitid_prep()
    
    The negation operator is incorrectly placed outside the unlikely()
    macro:
    
        if (!unlikely(iwa))
    
    This inverts the compiler branch prediction hint, marking the NULL case
    as likely instead of unlikely. The intent is to indicate that allocation
    failures are rare, consistent with common kernel patterns.
    
     Moving the negation inside unlikely():
    
        if (unlikely(!iwa))
    
    Fixes: 2b4fc4c ("io_uring/waitid: setup async data in the prep handler")
    Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
    Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
    Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

Author: JeffMoyer

io_uring/waitid.c

@@ -291,7 +291,7 @@ int io_waitid_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	iwa = io_uring_alloc_async_data(NULL, req);
-	if (!unlikely(iwa))
+	if (unlikely(!iwa))
 		return -ENOMEM;
 	iwa->req = req;