[PATCH rfc v2 02/10] arm64: mm: use try_vma_locked_page_fault()

[Kefeng Wang]

Use new try_vma_locked_page_fault() helper to simplify code, also
pass struct vmf to __do_page_fault() directly instead of each
independent variable. No functional change intended.

Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
---
 arch/arm64/mm/fault.c | 60 ++++++++++++++++---------------------------
 1 file changed, 22 insertions(+), 38 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 2e5d1e238af9..2b7a1e610b3e 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -498,9 +498,8 @@ static void do_bad_area(unsigned long far, unsigned long esr,
 #define VM_FAULT_BADACCESS	((__force vm_fault_t)0x020000)
 
 static vm_fault_t __do_page_fault(struct mm_struct *mm,
-				  struct vm_area_struct *vma, unsigned long addr,
-				  unsigned int mm_flags, unsigned long vm_flags,
-				  struct pt_regs *regs)
+				  struct vm_area_struct *vma,
+				  struct vm_fault *vmf)
 {
 	/*
 	 * Ok, we have a good vm_area for this memory access, so we can handle
@@ -508,9 +507,9 @@ static vm_fault_t __do_page_fault(struct mm_struct *mm,
 	 * Check that the permissions on the VMA allow for the fault which
 	 * occurred.
 	 */
-	if (!(vma->vm_flags & vm_flags))
+	if (!(vma->vm_flags & vmf->vm_flags))
 		return VM_FAULT_BADACCESS;
-	return handle_mm_fault(vma, addr, mm_flags, regs);
+	return handle_mm_fault(vma, vmf->real_address, vmf->flags, vmf->regs);
 }
 
 static bool is_el0_instruction_abort(unsigned long esr)
@@ -533,10 +532,12 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 	const struct fault_info *inf;
 	struct mm_struct *mm = current->mm;
 	vm_fault_t fault;
-	unsigned long vm_flags;
-	unsigned int mm_flags = FAULT_FLAG_DEFAULT;
 	unsigned long addr = untagged_addr(far);
 	struct vm_area_struct *vma;
+	struct vm_fault vmf = {
+		.real_address = addr,
+		.flags = FAULT_FLAG_DEFAULT,
+	};
 
 	if (kprobe_page_fault(regs, esr))
 		return 0;
@@ -549,7 +550,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 		goto no_context;
 
 	if (user_mode(regs))
-		mm_flags |= FAULT_FLAG_USER;
+		vmf.flags |= FAULT_FLAG_USER;
 
 	/*
 	 * vm_flags tells us what bits we must have in vma->vm_flags
@@ -559,20 +560,20 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 	 */
 	if (is_el0_instruction_abort(esr)) {
 		/* It was exec fault */
-		vm_flags = VM_EXEC;
-		mm_flags |= FAULT_FLAG_INSTRUCTION;
+		vmf.vm_flags = VM_EXEC;
+		vmf.flags |= FAULT_FLAG_INSTRUCTION;
 	} else if (is_write_abort(esr)) {
 		/* It was write fault */
-		vm_flags = VM_WRITE;
-		mm_flags |= FAULT_FLAG_WRITE;
+		vmf.vm_flags = VM_WRITE;
+		vmf.flags |= FAULT_FLAG_WRITE;
 	} else {
 		/* It was read fault */
-		vm_flags = VM_READ;
+		vmf.vm_flags = VM_READ;
 		/* Write implies read */
-		vm_flags |= VM_WRITE;
+		vmf.vm_flags |= VM_WRITE;
 		/* If EPAN is absent then exec implies read */
 		if (!cpus_have_const_cap(ARM64_HAS_EPAN))
-			vm_flags |= VM_EXEC;
+			vmf.vm_flags |= VM_EXEC;
 	}
 
 	if (is_ttbr0_addr(addr) && is_el1_permission_fault(addr, esr, regs)) {
@@ -587,26 +588,11 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
-	if (!(mm_flags & FAULT_FLAG_USER))
-		goto lock_mmap;
-
-	vma = lock_vma_under_rcu(mm, addr);
-	if (!vma)
-		goto lock_mmap;
-
-	if (!(vma->vm_flags & vm_flags)) {
-		vma_end_read(vma);
-		goto lock_mmap;
-	}
-	fault = handle_mm_fault(vma, addr, mm_flags | FAULT_FLAG_VMA_LOCK, regs);
-	if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
-		vma_end_read(vma);
-
-	if (!(fault & VM_FAULT_RETRY)) {
-		count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+	fault = try_vma_locked_page_fault(&vmf);
+	if (fault == VM_FAULT_NONE)
+		goto retry;
+	if (!(fault & VM_FAULT_RETRY))
 		goto done;
-	}
-	count_vm_vma_lock_event(VMA_LOCK_RETRY);
 
 	/* Quick path to respond to signals */
 	if (fault_signal_pending(fault, regs)) {
@@ -614,8 +600,6 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 			goto no_context;
 		return 0;
 	}
-lock_mmap:
-
 retry:
 	vma = lock_mm_and_find_vma(mm, addr, regs);
 	if (unlikely(!vma)) {
@@ -623,7 +607,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 		goto done;
 	}
 
-	fault = __do_page_fault(mm, vma, addr, mm_flags, vm_flags, regs);
+	fault = __do_page_fault(mm, vma, &vmf);
 
 	/* Quick path to respond to signals */
 	if (fault_signal_pending(fault, regs)) {
@@ -637,7 +621,7 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
 		return 0;
 
 	if (fault & VM_FAULT_RETRY) {
-		mm_flags |= FAULT_FLAG_TRIED;
+		vmf.flags |= FAULT_FLAG_TRIED;
 		goto retry;
 	}
 	mmap_read_unlock(mm);
-- 
2.27.0