[PATCH] ARM: mm: avoid unneeded page protection fault for memory range with (VM_PFNMAP|VM_PFNWRITE)
From: udknight@gmail.com (Wang YanQing)
Date: 2015-09-12 06:12:18
Also in:
linux-mm, lkml
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Add L_PTE_DIRTY to PTEs for memory range with (VM_PFNMAP|VM_PFNWRITE), then we could avoid unneeded page protection fault in write access first time due to L_PTE_RDONLY. There are no valid struct pages behind VM_PFNMAP range, so it make no sense to set L_PTE_DIRTY in page fault handler. Signed-off-by: Wang YanQing <udknight@gmail.com> --- arch/arm/include/asm/mman.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) create mode 100644 arch/arm/include/asm/mman.h
diff --git a/arch/arm/include/asm/mman.h b/arch/arm/include/asm/mman.h
new file mode 100644
index 0000000..f59bbf3
--- /dev/null
+++ b/arch/arm/include/asm/mman.h@@ -0,0 +1,21 @@ +/* + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ +#ifndef __ASM_ARM_MMAN_H +#define __ASM_ARM_MMAN_H + +#include <uapi/asm/mman.h> + +static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags) +{ + if ((vm_flags & (VM_PFNMAP|VM_WRITE)) == (VM_PFNMAP|VM_WRITE)) + return __pgprot(L_PTE_DIRTY); + else + return __pgprot(0); +} +#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags) + +#endif /* __ASM_ARM_MMAN_H */
--
1.8.5.6.2.g3d8a54e.dirty