[PATCH 7/7] x86: mm: accelerate pagefault when badaccess

[Kefeng Wang]

The vm_flags of vma already checked under per-VMA lock, if it is a
bad access, directly handle error and return, there is no need to
lock_mm_and_find_vma() and check vm_flags again.

Signed-off-by: Kefeng Wang <wangkefeng.w...@huawei.com>
---
 arch/x86/mm/fault.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a4cc20d0036d..67b18adc75dd 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -866,14 +866,17 @@ bad_area_nosemaphore(struct pt_regs *regs, unsigned long 
error_code,
 
 static void
 __bad_area(struct pt_regs *regs, unsigned long error_code,
-          unsigned long address, u32 pkey, int si_code)
+          unsigned long address, struct mm_struct *mm,
+          struct vm_area_struct *vma, u32 pkey, int si_code)
 {
-       struct mm_struct *mm = current->mm;
        /*
         * Something tried to access memory that isn't in our memory map..
         * Fix it, but check if it's kernel or user first..
         */
-       mmap_read_unlock(mm);
+       if (mm)
+               mmap_read_unlock(mm);
+       else
+               vma_end_read(vma);
 
        __bad_area_nosemaphore(regs, error_code, address, pkey, si_code);
 }
@@ -897,7 +900,8 @@ static inline bool bad_area_access_from_pkeys(unsigned long 
error_code,
 
 static noinline void
 bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
-                     unsigned long address, struct vm_area_struct *vma)
+                     unsigned long address, struct mm_struct *mm,
+                     struct vm_area_struct *vma)
 {
        /*
         * This OSPKE check is not strictly necessary at runtime.
@@ -927,9 +931,9 @@ bad_area_access_error(struct pt_regs *regs, unsigned long 
error_code,
                 */
                u32 pkey = vma_pkey(vma);
 
-               __bad_area(regs, error_code, address, pkey, SEGV_PKUERR);
+               __bad_area(regs, error_code, address, mm, vma, pkey, 
SEGV_PKUERR);
        } else {
-               __bad_area(regs, error_code, address, 0, SEGV_ACCERR);
+               __bad_area(regs, error_code, address, mm, vma, 0, SEGV_ACCERR);
        }
 }
 
@@ -1357,8 +1361,9 @@ void do_user_addr_fault(struct pt_regs *regs,
                goto lock_mmap;
 
        if (unlikely(access_error(error_code, vma))) {
-               vma_end_read(vma);
-               goto lock_mmap;
+               bad_area_access_error(regs, error_code, address, NULL, vma);
+               count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+               return;
        }
        fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, 
regs);
        if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
@@ -1394,7 +1399,7 @@ void do_user_addr_fault(struct pt_regs *regs,
         * we can handle it..
         */
        if (unlikely(access_error(error_code, vma))) {
-               bad_area_access_error(regs, error_code, address, vma);
+               bad_area_access_error(regs, error_code, address, mm, vma);
                return;
        }
 
-- 
2.27.0