[009/166] mm/vma: append unlikely() while testing VMA access permissions

Commit Message

Andrew Morton April 7, 2020, 3:03 a.m. UTC

From: Anshuman Khandual <[e-mail]>
Subject: mm/vma: append unlikely() while testing VMA access permissions

It is unlikely that an inaccessible VMA without required permission flags
will get a page fault.  Hence lets just append unlikely() directive to
such checks in order to improve performance while also standardizing it
across various platforms.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Anshuman Khandual <[e-mail]>
Reviewed-by: Andrew Morton <[e-mail]>
Cc: Guo Ren <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 arch/csky/mm/fault.c |    2 +-
 arch/m68k/mm/fault.c |    2 +-
 arch/mips/mm/fault.c |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

Patch

--- a/arch/csky/mm/fault.c~mm-vma-append-unlikely-while-testing-vma-access-permissions
+++ a/arch/csky/mm/fault.c
@@ -141,7 +141,7 @@  good_area:
 		if (!(vma->vm_flags & VM_WRITE))
 			goto bad_area;
 	} else {
-		if (!vma_is_accessible(vma))
+		if (unlikely(!vma_is_accessible(vma)))
 			goto bad_area;
 	}
 
--- a/arch/m68k/mm/fault.c~mm-vma-append-unlikely-while-testing-vma-access-permissions
+++ a/arch/m68k/mm/fault.c
@@ -125,7 +125,7 @@  good_area:
 		case 1:		/* read, present */
 			goto acc_err;
 		case 0:		/* read, not present */
-			if (!vma_is_accessible(vma))
+			if (unlikely(!vma_is_accessible(vma)))
 				goto acc_err;
 	}
 
--- a/arch/mips/mm/fault.c~mm-vma-append-unlikely-while-testing-vma-access-permissions
+++ a/arch/mips/mm/fault.c
@@ -142,7 +142,7 @@  good_area:
 				goto bad_area;
 			}
 		} else {
-			if (!vma_is_accessible(vma))
+			if (unlikely(!vma_is_accessible(vma)))
 				goto bad_area;
 		}
 	}