Re: [PATCH 1/3] mm: add apply_to_existing_pages helper

Andrew Morton
2019-12-07T00:38:56Z

On Fri, 6 Dec 2019 01:04:05 +1100 Daniel Axtens <dja@axtens.net> wrote:

> apply_to_page_range takes an address range, and if any parts of it
> are not covered by the existing page table hierarchy, it allocates
> memory to fill them in.
>
> In some use cases, this is not what we want - we want to be able to
> operate exclusively on PTEs that are already in the tables.
>
> Add apply_to_existing_pages for this. Adjust the walker functions
> for apply_to_page_range to take 'create', which switches them between
> the old and new modes.

Wouldn't apply_to_existing_page_range() be a better name?

--- a/include/linux/mm.h~mm-add-apply_to_existing_pages-helper-fix-fix
+++ a/include/linux/mm.h
@@ -2621,9 +2621,9 @@ static inline int vm_fault_to_errno(vm_f
typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data);
extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
unsigned long size, pte_fn_t fn, void *data);
-extern int apply_to_existing_pages(struct mm_struct *mm, unsigned long address,
- unsigned long size, pte_fn_t fn,
- void *data);
+extern int apply_to_existing_page_range(struct mm_struct *mm,
+ unsigned long address, unsigned long size,
+ pte_fn_t fn, void *data);

#ifdef CONFIG_PAGE_POISONING
extern bool page_poisoning_enabled(void);
--- a/mm/memory.c~mm-add-apply_to_existing_pages-helper-fix-fix
+++ a/mm/memory.c
@@ -2184,12 +2184,12 @@ EXPORT_SYMBOL_GPL(apply_to_page_range);
* Unlike apply_to_page_range, this does _not_ fill in page tables
* where they are absent.
*/
-int apply_to_existing_pages(struct mm_struct *mm, unsigned long addr,
- unsigned long size, pte_fn_t fn, void *data)
+int apply_to_existing_page_range(struct mm_struct *mm, unsigned long addr,
+ unsigned long size, pte_fn_t fn, void *data)
{
return __apply_to_page_range(mm, addr, size, fn, data, false);
}
-EXPORT_SYMBOL_GPL(apply_to_existing_pages);
+EXPORT_SYMBOL_GPL(apply_to_existing_page_range);

/*
* handle_pte_fault chooses page fault handler according to an entry which was
_