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[PATCH] mm: split highorder pages

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Have an explicit mm call to split higher order pages into individual pages.
 Should help to avoid bugs and be more explicit about the code's intention.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Yoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2006-03-22 00:08:05 -08:00 committed by Linus Torvalds
parent 8e7a9aae91
commit 8dfcc9ba27
9 changed files with 41 additions and 21 deletions
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4
arch/arm/mm/consistent.c
View File

@ -223,6 +223,8 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
pte = consistent_pte[idx] + off;
c->vm_pages = page;
split_page(page, order);
/*
* Set the "dma handle"
*/
@ -231,7 +233,6 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
do {
BUG_ON(!pte_none(*pte));
set_page_count(page, 1);
/*
* x86 does not mark the pages reserved...
*/
@ -250,7 +251,6 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
* Free the otherwise unused pages.
*/
while (page < end) {
set_page_count(page, 1);
__free_page(page);
page++;
}

4
arch/frv/mm/dma-alloc.c
View File

@ -115,9 +115,7 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *dma_handle)
*/
if (order > 0) {
struct page *rpage = virt_to_page(page);
for (i = 1; i < (1 << order); i++)
set_page_count(rpage + i, 1);
split_page(rpage, order);
}
err = 0;

5
arch/mips/mm/init.c
View File

@ -54,7 +54,8 @@ unsigned long empty_zero_page, zero_page_mask;
*/
unsigned long setup_zero_pages(void)
{
unsigned long order, size;
unsigned int order;
unsigned long size;
struct page *page;
if (cpu_has_vce)
@ -67,9 +68,9 @@ unsigned long setup_zero_pages(void)
panic("Oh boy, that early out of memory?");
page = virt_to_page(empty_zero_page);
split_page(page, order);
while (page < virt_to_page(empty_zero_page + (PAGE_SIZE << order))) {
SetPageReserved(page);
set_page_count(page, 1);
page++;
}

4
arch/ppc/kernel/dma-mapping.c
View File

@ -223,6 +223,8 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
pte_t *pte = consistent_pte + CONSISTENT_OFFSET(vaddr);
struct page *end = page + (1 << order);
split_page(page, order);
/*
* Set the "dma handle"
*/
@ -231,7 +233,6 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
do {
BUG_ON(!pte_none(*pte));
set_page_count(page, 1);
SetPageReserved(page);
set_pte_at(&init_mm, vaddr,
pte, mk_pte(page, pgprot_noncached(PAGE_KERNEL)));
@ -244,7 +245,6 @@ __dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
* Free the otherwise unused pages.
*/
while (page < end) {
set_page_count(page, 1);
__free_page(page);
page++;
}

3
arch/sh/mm/consistent.c
View File

@ -23,6 +23,7 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *handle)
page = alloc_pages(gfp, order);
if (!page)
return NULL;
split_page(page, order);
ret = page_address(page);
*handle = virt_to_phys(ret);
@ -37,8 +38,6 @@ void *consistent_alloc(gfp_t gfp, size_t size, dma_addr_t *handle)
end = page + (1 << order);
while (++page < end) {
set_page_count(page, 1);
/* Free any unused pages */
if (page >= free) {
__free_page(page);

10
arch/xtensa/mm/pgtable.c
View File

@ -21,13 +21,9 @@ pte_t* pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
p = (pte_t*) __get_free_pages(GFP_KERNEL|__GFP_REPEAT, COLOR_ORDER);
if (likely(p)) {
struct page *page;
split_page(virt_to_page(p), COLOR_ORDER);
for (i = 0; i < COLOR_SIZE; i++) {
page = virt_to_page(p);
set_page_count(page, 1);
if (ADDR_COLOR(p) == color)
pte = p;
else
@ -55,9 +51,9 @@ struct page* pte_alloc_one(struct mm_struct *mm, unsigned long address)
p = alloc_pages(GFP_KERNEL | __GFP_REPEAT, PTE_ORDER);
if (likely(p)) {
for (i = 0; i < PAGE_ORDER; i++) {
set_page_count(p, 1);
split_page(p, COLOR_ORDER);
for (i = 0; i < PAGE_ORDER; i++) {
if (PADDR_COLOR(page_address(p)) == color)
page = p;
else

6
include/linux/mm.h
View File

@ -328,6 +328,12 @@ static inline void get_page(struct page *page)
void put_page(struct page *page);
#ifdef CONFIG_MMU
void split_page(struct page *page, unsigned int order);
#else
static inline void split_page(struct page *page, unsigned int order) {}
#endif
/*
* Multiple processes may "see" the same page. E.g. for untouched
* mappings of /dev/null, all processes see the same page full of

4
mm/memory.c
View File

@ -1221,9 +1221,7 @@ out:
* The page has to be a nice clean _individual_ kernel allocation.
* If you allocate a compound page, you need to have marked it as
* such (__GFP_COMP), or manually just split the page up yourself
* (which is mainly an issue of doing "set_page_count(page, 1)" for
* each sub-page, and then freeing them one by one when you free
* them rather than freeing it as a compound page).
* (see split_page()).
*
* NOTE! Traditionally this was done with "remap_pfn_range()" which
* took an arbitrary page protection parameter. This doesn't allow

22
mm/page_alloc.c
View File

@ -752,6 +752,28 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
clear_highpage(page + i);
}
#ifdef CONFIG_MMU
/*
* split_page takes a non-compound higher-order page, and splits it into
* n (1<<order) sub-pages: page[0..n]
* Each sub-page must be freed individually.
*
* Note: this is probably too low level an operation for use in drivers.
* Please consult with lkml before using this in your driver.
*/
void split_page(struct page *page, unsigned int order)
{
int i;
BUG_ON(PageCompound(page));
BUG_ON(!page_count(page));
for (i = 1; i < (1 << order); i++) {
BUG_ON(page_count(page + i));
set_page_count(page + i, 1);
}
}
#endif
/*
* Really, prep_compound_page() should be called from __rmqueue_bulk(). But
* we cheat by calling it from here, in the order > 0 path. Saves a branch