riscv: mm: accelerate pagefault when badaccess

The access_error() of vma already checked under per-VMA lock, if it
is a bad access, directly handle error, no need to retry with mmap_lock
again. Since the page faut is handled under per-VMA lock, count it as
a vma lock event with VMA_LOCK_SUCCESS.

Reviewed-by: Suren Baghdasaryan <[email protected]>
Signed-off-by: Kefeng Wang <[email protected]>
Reviewed-by: Alexandre Ghiti <[email protected]>
Tested-by: Alexandre Ghiti <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: Kefeng Wang

arch/riscv/mm/fault.c

@@ -293,8 +293,8 @@ void handle_page_fault(struct pt_regs *regs)
 	if (unlikely(access_error(cause, vma))) {
 		vma_end_read(vma);
 		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
-		tsk->thread.bad_cause = cause;
-		bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
+		tsk->thread.bad_cause = SEGV_ACCERR;
+		bad_area_nosemaphore(regs, code, addr);
 		return;
 	}