Add a new vma flag to allow an architecture to disable the backing of non-present, anonymous pages with the read-only empty zero page. Signed-off-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx> Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> --- include/linux/mm.h | 13 +++++++++++-- mm/huge_memory.c | 2 +- mm/memory.c | 2 +- 3 files changed, 13 insertions(+), 4 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index cd33ae2..8f09c91 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -113,7 +113,7 @@ extern unsigned int kobjsize(const void *objp); #define VM_GROWSDOWN 0x00000100 /* general info on the segment */ #define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */ #define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */ - +#define VM_NOZEROPAGE 0x00001000 /* forbid new zero page mappings */ #define VM_LOCKED 0x00002000 #define VM_IO 0x00004000 /* Memory mapped I/O or similar */ @@ -179,7 +179,7 @@ extern unsigned int kobjsize(const void *objp); #define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP) /* This mask defines which mm->def_flags a process can inherit its parent */ -#define VM_INIT_DEF_MASK VM_NOHUGEPAGE +#define VM_INIT_DEF_MASK (VM_NOHUGEPAGE | VM_NOZEROPAGE) /* * mapping from the currently active vm_flags protection bits (the @@ -1293,6 +1293,15 @@ static inline int stack_guard_page_end(struct vm_area_struct *vma, !vma_growsup(vma->vm_next, addr); } +static inline int vma_forbids_zeropage(struct vm_area_struct *vma) +{ +#ifdef CONFIG_NOZEROPAGE + return vma->vm_flags & VM_NOZEROPAGE; +#else + return 0; +#endif +} + extern struct task_struct *task_of_stack(struct task_struct *task, struct vm_area_struct *vma, bool in_group); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index de98415..c271265 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -805,7 +805,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; if (unlikely(khugepaged_enter(vma, vma->vm_flags))) return VM_FAULT_OOM; - if (!(flags & FAULT_FLAG_WRITE) && + if (!(flags & FAULT_FLAG_WRITE) && !vma_forbids_zeropage(vma) && transparent_hugepage_use_zero_page()) { spinlock_t *ptl; pgtable_t pgtable; diff --git a/mm/memory.c b/mm/memory.c index 64f82aa..1859b2b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2640,7 +2640,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_SIGBUS; /* Use the zero-page for reads */ - if (!(flags & FAULT_FLAG_WRITE)) { + if (!(flags & FAULT_FLAG_WRITE) && !vma_forbids_zeropage(vma)) { entry = pte_mkspecial(pfn_pte(my_zero_pfn(address), vma->vm_page_prot)); page_table = pte_offset_map_lock(mm, pmd, address, &ptl); -- 1.8.5.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>