[PATCH rfc -next 10/10] loongarch: mm: try VMA lock-based page fault handling first

[Kefeng Wang]

Attempt VMA lock-based page fault handling first, and fall back
to the existing mmap_lock-based handling if that fails.

Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
---
 arch/loongarch/Kconfig    |  1 +
 arch/loongarch/mm/fault.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 397203e18800..afb0ccabab97 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -53,6 +53,7 @@ config LOONGARCH
 	select ARCH_SUPPORTS_LTO_CLANG
 	select ARCH_SUPPORTS_LTO_CLANG_THIN
 	select ARCH_SUPPORTS_NUMA_BALANCING
+	select ARCH_SUPPORTS_PER_VMA_LOCK
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_USE_QUEUED_RWLOCKS
diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index cde2ea0119fa..7e54bc48813e 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -136,6 +136,17 @@ static inline bool access_error(unsigned int flags, struct pt_regs *regs,
 	return false;
 }
 
+#ifdef CONFIG_PER_VMA_LOCK
+int arch_vma_check_access(struct vm_area_struct *vma,
+			  struct vm_locked_fault *vmlf)
+{
+	if (unlikely(access_error(vmlf->fault_flags, vmlf->regs, vmlf->address,
+		     vma)))
+		return -EINVAL;
+	return 0;
+}
+#endif
+
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
@@ -149,6 +160,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
 	struct vm_area_struct *vma = NULL;
+	struct vm_locked_fault vmlf;
 	vm_fault_t fault;
 
 	if (kprobe_page_fault(regs, current->thread.trap_nr))
@@ -183,6 +195,19 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 		flags |= FAULT_FLAG_WRITE;
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
+	VM_LOCKED_FAULT_INIT(vmlf, mm, address, flags, 0, regs, 0);
+	if (try_vma_locked_page_fault(&vmlf, &fault))
+		goto retry;
+	else if (!(fault | VM_FAULT_RETRY))
+		goto done;
+
+	if (fault_signal_pending(fault, regs)) {
+		if (!user_mode(regs))
+			no_context(regs, address);
+		return;
+	}
+
 retry:
 	vma = lock_mm_and_find_vma(mm, address, regs);
 	if (unlikely(!vma))
@@ -223,6 +248,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 
 	mmap_read_unlock(mm);
 
+done:
 	if (unlikely(fault & VM_FAULT_ERROR)) {
 		if (fault & VM_FAULT_OOM) {
 			do_out_of_memory(regs, address);
-- 
2.27.0