On 07/10/2018 07:53 PM, Matthew Wilcox wrote:
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 21e1b6a9f113..8a4698b368de 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -153,6 +153,11 @@ struct page {
> spinlock_t ptl;
> #endif
> };
> + struct { /* VMalloc pages */
> + struct vm_struct *vm_area;
> + unsigned long vm_offset;
> + unsigned long _vm_id; /* MAPPING_VMalloc */
> + };
> struct { /* ZONE_DEVICE pages */
> /** @pgmap: Points to the hosting device page map. */
> struct dev_pagemap *pgmap;
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 901943e4754b..588b8dd28a85 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -699,6 +699,32 @@ PAGE_TYPE_OPS(Kmemcg, kmemcg)
> */
> PAGE_TYPE_OPS(Table, table)
>
> +/*
> + * vmalloc pages may be mapped to userspace, so we need some other way
> + * to distinguish them from other kinds of pages. Use page->mapping for
> + * this purpose. Values below 0x1000 cannot be real pointers. Setting
> + * the bottom bit makes page_mapping() return NULL, which is what we want.
> + */
> +#define MAPPING_VMalloc (void *)0x441
So this makes the vmalloc pages look like anon pages,
while previously they were !PageAnon.
I'm pretty sure this is not going to work.
> +
> +#define PAGE_MAPPING_OPS(name) \
> +static __always_inline int Page##name(struct page *page) \
> +{ \
> + return page->mapping == MAPPING_##name; \
> +} \
> +static __always_inline void __SetPage##name(struct page *page) \
> +{ \
> + VM_BUG_ON_PAGE(page->mapping != NULL, page); \
> + page->mapping = MAPPING_##name; \
> +} \
> +static __always_inline void __ClearPage##name(struct page *page) \
> +{ \
> + VM_BUG_ON_PAGE(page->mapping != MAPPING_##name, page); \
> + page->mapping = NULL; \
> +}
> +
> +PAGE_MAPPING_OPS(VMalloc)
> +
