From: blaisorblade_spam@yahoo.it Avoid using, in the UBD driver, the elv_queue_empty function. It's for the block layer only; in fact, the Anticipatory Scheduler can return NULL with elv_next_request() even if the queue is not empty, because it waits for the process to send another request before seeking on the disk. In fact, if (with uml-ubd-any-elevator) we let UBD use any scheduler, elevator=as will make the UBD driver Oops, if we don't have this patch. Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton --- 25-akpm/arch/um/drivers/ubd_kern.c | 6 ++---- 1 files changed, 2 insertions(+), 4 deletions(-) diff -puN arch/um/drivers/ubd_kern.c~uml-avoid-using-elv_queue_empty arch/um/drivers/ubd_kern.c --- 25/arch/um/drivers/ubd_kern.c~uml-avoid-using-elv_queue_empty 2004-09-06 14:20:37.400490736 -0700 +++ 25-akpm/arch/um/drivers/ubd_kern.c 2004-09-06 14:20:37.404490128 -0700 @@ -1038,8 +1038,7 @@ static void do_ubd_request(request_queue int err, n; if(thread_fd == -1){ - while(!elv_queue_empty(q)){ - req = elv_next_request(q); + while((req = elv_next_request(q)) != NULL){ err = prepare_request(req, &io_req); if(!err){ do_io(&io_req); @@ -1048,9 +1047,8 @@ static void do_ubd_request(request_queue } } else { - if(do_ubd || elv_queue_empty(q)) + if(do_ubd || (req = elv_next_request(q)) == NULL) return; - req = elv_next_request(q); err = prepare_request(req, &io_req); if(!err){ do_ubd = ubd_handler; _