Commit add688fb authored by malc's avatar malc Committed by Linus Torvalds
Browse files

Revert "mm/vmalloc: interchage the implementation of vmalloc_to_{pfn,page}"

Revert commit ece86e22

, which was intended as a small performance

Despite the claim that the patch doesn't introduce any functional
changes in fact it does.

The "no page" path behaves different now.  Originally, vmalloc_to_page
might return NULL under some conditions, with new implementation it
returns pfn_to_page(0) which is not the same as NULL.

Simple test shows the difference.


#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>

int __init myi(void)
	struct page *p;
	void *v;

	v = vmalloc(PAGE_SIZE);
	/* trigger the "no page" path in vmalloc_to_page*/

	p = vmalloc_to_page(v);

	pr_err("expected val = NULL, returned val = %p", p);

	return -EBUSY;

void __exit mye(void)


Before interchange:
expected val = NULL, returned val =   (null)

After interchange:
expected val = NULL, returned val = c7ebe000
Signed-off-by: default avatarVladimir Murzin <>
Cc: Jianyu Zhan <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent fb5bb60c
......@@ -220,12 +220,12 @@ int is_vmalloc_or_module_addr(const void *x)
* Walk a vmap address to the physical pfn it maps to.
* Walk a vmap address to the struct page it maps.
unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
struct page *vmalloc_to_page(const void *vmalloc_addr)
unsigned long addr = (unsigned long) vmalloc_addr;
unsigned long pfn = 0;
struct page *page = NULL;
pgd_t *pgd = pgd_offset_k(addr);
......@@ -244,23 +244,23 @@ unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
ptep = pte_offset_map(pmd, addr);
pte = *ptep;
if (pte_present(pte))
pfn = pte_pfn(pte);
page = pte_page(pte);
return pfn;
return page;
* Map a vmalloc()-space virtual address to the struct page.
* Map a vmalloc()-space virtual address to the physical page frame number.
struct page *vmalloc_to_page(const void *vmalloc_addr)
unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
return pfn_to_page(vmalloc_to_pfn(vmalloc_addr));
return page_to_pfn(vmalloc_to_page(vmalloc_addr));
/*** Global kva allocator ***/
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