[PATCH rfc -next 07/10] ARM: 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/arm/Kconfig    |  1 +
 arch/arm/mm/fault.c | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 1a6a6eb48a15..8b6d4507ccee 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -34,6 +34,7 @@ config ARM
 	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_HUGETLBFS if ARM_LPAE
+	select ARCH_SUPPORTS_PER_VMA_LOCK
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_USE_MEMTEST
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index fef62e4a9edd..c44b83841e36 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -244,6 +244,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	vm_fault_t fault;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
 	unsigned long vm_flags = VM_ACCESS_FLAGS;
+	struct vm_locked_fault vmlf;
 
 	if (kprobe_page_fault(regs, fsr))
 		return 0;
@@ -278,6 +279,18 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 
+	VM_LOCKED_FAULT_INIT(vmlf, mm, addr, flags, vm_flags, regs, fsr);
+	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))
+			goto no_context;
+		return 0;
+	}
+
 retry:
 	vma = lock_mm_and_find_vma(mm, addr, regs);
 	if (unlikely(!vma)) {
@@ -316,7 +329,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	}
 
 	mmap_read_unlock(mm);
-
+done:
 	/*
 	 * Handle the "normal" case first - VM_FAULT_MAJOR
 	 */
-- 
2.27.0