On 2023/8/24 15:12, Alexander Gordeev wrote:
On Mon, Aug 21, 2023 at 08:30:47PM +0800, Kefeng Wang wrote:
Hi Kefeng,
The ARCH_SUPPORTS_PER_VMA_LOCK are enabled by more and more architectures,
eg, x86, arm64, powerpc and s390, and riscv, those implementation are very
similar which results in some duplicated codes, let's add a generic VMA
lock-based page fault handler try_to_vma_locked_page_fault() to eliminate
them, and which also make us easy to support this on new architectures.
Since different architectures use different way to check vma whether is
accessable or not, the struct pt_regs, page fault error code and vma flags
are added into struct vm_fault, then, the architecture's page fault code
could re-use struct vm_fault to record and check vma accessable by each
own implementation.
Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
...
+
+vm_fault_t try_vma_locked_page_fault(struct vm_fault *vmf)
+{
+ vm_fault_t fault = VM_FAULT_NONE;
+ struct vm_area_struct *vma;
+
+ if (!(vmf->flags & FAULT_FLAG_USER))
+ return fault;
+
+ vma = lock_vma_under_rcu(current->mm, vmf->real_address);
+ if (!vma)
+ return fault;
+
+ if (arch_vma_access_error(vma, vmf)) {
+ vma_end_read(vma);
+ return fault;
+ }
+
+ fault = handle_mm_fault(vma, vmf->real_address,
+ vmf->flags | FAULT_FLAG_VMA_LOCK, vmf->regs);
+
+ if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
+ vma_end_read(vma);
Could you please explain how vma_end_read() call could be conditional?
The check is added for swap and userfault, see
https://lkml.kernel.org/r/20230630211957.1341547-4-surenb@xxxxxxxxxx
+
+ if (fault & VM_FAULT_RETRY)
+ count_vm_vma_lock_event(VMA_LOCK_RETRY);
+ else
+ count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+
+ return fault;
+}
+
#endif /* CONFIG_PER_VMA_LOCK */
#ifndef __PAGETABLE_P4D_FOLDED
