[rfc,v2,03/10] x86: mm: use try_vma_locked_page_fault()

Commit Message

Kefeng Wang Aug. 21, 2023, 12:30 p.m. UTC

Use new try_vma_locked_page_fault() helper to simplify code.
No functional change intended.

Signed-off-by: Kefeng Wang <[e-mail]>
---
 arch/x86/mm/fault.c | 55 +++++++++++++++++++--------------------------
 1 file changed, 23 insertions(+), 32 deletions(-)

Patch

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ab778eac1952..3edc9edc0b28 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1227,6 +1227,13 @@  do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
 }
 NOKPROBE_SYMBOL(do_kern_addr_fault);
 
+#ifdef CONFIG_PER_VMA_LOCK
+bool arch_vma_access_error(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	return access_error(vmf->fault_code, vma);
+}
+#endif
+
 /*
  * Handle faults in the user portion of the address space.  Nothing in here
  * should check X86_PF_USER without a specific justification: for almost
@@ -1241,13 +1248,13 @@  void do_user_addr_fault(struct pt_regs *regs,
 			unsigned long address)
 {
 	struct vm_area_struct *vma;
-	struct task_struct *tsk;
-	struct mm_struct *mm;
+	struct mm_struct *mm = current->mm;
 	vm_fault_t fault;
-	unsigned int flags = FAULT_FLAG_DEFAULT;
-
-	tsk = current;
-	mm = tsk->mm;
+	struct vm_fault vmf = {
+		.real_address = address,
+		.fault_code = error_code,
+		.flags = FAULT_FLAG_DEFAULT
+	};
 
 	if (unlikely((error_code & (X86_PF_USER | X86_PF_INSTR)) == X86_PF_INSTR)) {
 		/*
@@ -1311,7 +1318,7 @@  void do_user_addr_fault(struct pt_regs *regs,
 	 */
 	if (user_mode(regs)) {
 		local_irq_enable();
-		flags |= FAULT_FLAG_USER;
+		vmf.flags |= FAULT_FLAG_USER;
 	} else {
 		if (regs->flags & X86_EFLAGS_IF)
 			local_irq_enable();
@@ -1326,11 +1333,11 @@  void do_user_addr_fault(struct pt_regs *regs,
 	 * maybe_mkwrite() can create a proper shadow stack PTE.
 	 */
 	if (error_code & X86_PF_SHSTK)
-		flags |= FAULT_FLAG_WRITE;
+		vmf.flags |= FAULT_FLAG_WRITE;
 	if (error_code & X86_PF_WRITE)
-		flags |= FAULT_FLAG_WRITE;
+		vmf.flags |= FAULT_FLAG_WRITE;
 	if (error_code & X86_PF_INSTR)
-		flags |= FAULT_FLAG_INSTRUCTION;
+		vmf.flags |= FAULT_FLAG_INSTRUCTION;
 
 #ifdef CONFIG_X86_64
 	/*
@@ -1350,26 +1357,11 @@  void do_user_addr_fault(struct pt_regs *regs,
 	}
 #endif
 
-	if (!(flags & FAULT_FLAG_USER))
-		goto lock_mmap;
-
-	vma = lock_vma_under_rcu(mm, address);
-	if (!vma)
-		goto lock_mmap;
-
-	if (unlikely(access_error(error_code, vma))) {
-		vma_end_read(vma);
-		goto lock_mmap;
-	}
-	fault = handle_mm_fault(vma, address, 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)) {
@@ -1379,7 +1371,6 @@  void do_user_addr_fault(struct pt_regs *regs,
 						 ARCH_DEFAULT_PKEY);
 		return;
 	}
-lock_mmap:
 
 retry:
 	vma = lock_mm_and_find_vma(mm, address, regs);
@@ -1410,7 +1401,7 @@  void do_user_addr_fault(struct pt_regs *regs,
 	 * userland). The return to userland is identified whenever
 	 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
 	 */
-	fault = handle_mm_fault(vma, address, flags, regs);
+	fault = handle_mm_fault(vma, address, vmf.flags, regs);
 
 	if (fault_signal_pending(fault, regs)) {
 		/*
@@ -1434,7 +1425,7 @@  void do_user_addr_fault(struct pt_regs *regs,
 	 * that we made any progress. Handle this case first.
 	 */
 	if (unlikely(fault & VM_FAULT_RETRY)) {
-		flags |= FAULT_FLAG_TRIED;
+		vmf.flags |= FAULT_FLAG_TRIED;
 		goto retry;
 	}