x86: Move do_page_fault()'s error path under unlikely()
KOSAKI Motohiro [Thu, 26 May 2011 08:12:12 +0000 (17:12 +0900)]
Ingo suggested SIGKILL check should be moved into slowpath
function. This will reduce the page fault fastpath impact
of this recent commit:

  37b23e0525d3: x86,mm: make pagefault killable

Suggested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: kamezawa.hiroyu@jp.fujitsu.com
Cc: minchan.kim@gmail.com
Cc: willy@linux.intel.com
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/4DDE0B5C.9050907@jp.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/fault.c

index f7a2a05..2dbf6bf 100644 (file)
@@ -823,16 +823,30 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
        force_sig_info_fault(SIGBUS, code, address, tsk, fault);
 }
 
-static noinline void
+static noinline int
 mm_fault_error(struct pt_regs *regs, unsigned long error_code,
               unsigned long address, unsigned int fault)
 {
+       /*
+        * Pagefault was interrupted by SIGKILL. We have no reason to
+        * continue pagefault.
+        */
+       if (fatal_signal_pending(current)) {
+               if (!(fault & VM_FAULT_RETRY))
+                       up_read(&current->mm->mmap_sem);
+               if (!(error_code & PF_USER))
+                       no_context(regs, error_code, address);
+               return 1;
+       }
+       if (!(fault & VM_FAULT_ERROR))
+               return 0;
+
        if (fault & VM_FAULT_OOM) {
                /* Kernel mode? Handle exceptions or die: */
                if (!(error_code & PF_USER)) {
                        up_read(&current->mm->mmap_sem);
                        no_context(regs, error_code, address);
-                       return;
+                       return 1;
                }
 
                out_of_memory(regs, error_code, address);
@@ -843,6 +857,7 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
                else
                        BUG();
        }
+       return 1;
 }
 
 static int spurious_fault_check(unsigned long error_code, pte_t *pte)
@@ -1133,19 +1148,9 @@ good_area:
         */
        fault = handle_mm_fault(mm, vma, address, flags);
 
-       if (unlikely(fault & VM_FAULT_ERROR)) {
-               mm_fault_error(regs, error_code, address, fault);
-               return;
-       }
-
-       /*
-        * Pagefault was interrupted by SIGKILL. We have no reason to
-        * continue pagefault.
-        */
-       if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
-               if (!(error_code & PF_USER))
-                       no_context(regs, error_code, address);
-               return;
+       if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+               if (mm_fault_error(regs, error_code, address, fault))
+                       return;
        }
 
        /*