What I really wanted in the end was a highmem-capable alloc_pages_exact(),
so here it is.
It's a bit unfortunate that we have __free_pages_exact() and
free_pages_exact(), but that mess already exists with __free_pages()
vs. free_pages_exact(). So, at worst, this mirrors the mess that we
already have.
I'm also a bit worried that I've not put in something named
alloc_pages_exact(), but that behaves differently. I got all of the
in-tree cases, but I'm a bit worried about stragglers elsewheree
Note that the __get_free_pages() has a !GFP_HIGHMEM check. Now that
we're not using it, we had to add a new check to get_free_pages_exact().
Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
---
linux-2.6.git-dave/include/linux/gfp.h | 4 +
linux-2.6.git-dave/mm/page_alloc.c | 81 ++++++++++++++++++++++++---------
2 files changed, 65 insertions(+), 20 deletions(-)
diff -puN include/linux/gfp.h~make_new_alloc_pages_exact include/linux/gfp.h
--- linux-2.6.git/include/linux/gfp.h~make_new_alloc_pages_exact 2011-03-22 12:11:57.557452739 -0700
+++ linux-2.6.git-dave/include/linux/gfp.h 2011-03-22 12:11:57.573452738 -0700
@@ -346,6 +346,10 @@ extern struct page *alloc_pages_vma(gfp_
extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
extern unsigned long get_zeroed_page(gfp_t gfp_mask);
+/* 'struct page' version */
+struct page *alloc_pages_exact(gfp_t gfp_mask, size_t);
+void __free_pages_exact(struct page *page, size_t size);
+/* virtual address version */
void *get_free_pages_exact(size_t size, gfp_t gfp_mask);
void free_pages_exact(void *virt, size_t size);
diff -puN mm/page_alloc.c~make_new_alloc_pages_exact mm/page_alloc.c
--- linux-2.6.git/mm/page_alloc.c~make_new_alloc_pages_exact 2011-03-22 12:11:57.561452738 -0700
+++ linux-2.6.git-dave/mm/page_alloc.c 2011-03-22 12:11:57.573452738 -0700
@@ -2284,36 +2284,83 @@ void free_pages(unsigned long addr, unsi
EXPORT_SYMBOL(free_pages);
/**
- * get_free_pages_exact - allocate an exact number physically-contiguous pages.
+ * alloc_pages_exact - allocate an exact number physically-contiguous pages.
* @size: the number of bytes to allocate
* @gfp_mask: GFP flags for the allocation
+ * returns: struct page for allocated memory
*
- * This function is similar to __get_free_pages(), except that it allocates the
- * minimum number of pages to satisfy the request. get_free_pages() can only
+ * This function is similar to alloc_pages(), except that it allocates the
+ * minimum number of pages to satisfy the request. alloc_pages() can only
* allocate memory in power-of-two pages.
*
* This function is also limited by MAX_ORDER.
*
* Memory allocated by this function must be released by free_pages_exact().
*/
-void *get_free_pages_exact(size_t size, gfp_t gfp_mask)
+struct page *alloc_pages_exact(gfp_t gfp_mask, size_t size)
{
unsigned int order = get_order(size);
- unsigned long addr;
+ struct page *page;
- addr = __get_free_pages(gfp_mask, order);
- if (addr) {
- unsigned long alloc_end = addr + (PAGE_SIZE << order);
- unsigned long used = addr + PAGE_ALIGN(size);
+ page = alloc_pages(gfp_mask, order);
+ if (page) {
+ struct page *alloc_end = page + (1 << order);
+ struct page *used = page + PAGE_ALIGN(size)/PAGE_SIZE;
- split_page(virt_to_page((void *)addr), order);
+ split_page(page, order);
while (used < alloc_end) {
- free_page(used);
- used += PAGE_SIZE;
+ __free_page(page);
+ used++;
}
}
- return (void *)addr;
+ return page;
+}
+EXPORT_SYMBOL(alloc_pages_exact);
+
+/**
+ * __free_pages_exact - release memory allocated via alloc_pages_exact()
+ * @virt: the value returned by alloc_pages_exact().
+ * @size: size of allocation, same value as passed to alloc_pages_exact().
+ *
+ * Release the memory allocated by a previous call to alloc_pages_exact().
+ */
+void __free_pages_exact(struct page *page, size_t size)
+{
+ struct page *end = page + PAGE_ALIGN(size)/PAGE_SIZE;
+
+ while (page < end) {
+ __free_page(page);
+ page++;
+ }
+}
+EXPORT_SYMBOL(__free_pages_exact);
+
+/**
+ * get_free_pages_exact - allocate an exact number physically-contiguous pages.
+ * @size: the number of bytes to allocate
+ * @gfp_mask: GFP flags for the allocation
+ * returns: virtual address of allocated memory
+ *
+ * This function is similar to __get_free_pages(), except that it allocates the
+ * minimum number of pages to satisfy the request. get_free_pages() can only
+ * allocate memory in power-of-two pages.
+ *
+ * This function is also limited by MAX_ORDER.
+ *
+ * Memory allocated by this function must be released by free_pages_exact().
+ */
+void *get_free_pages_exact(size_t size, gfp_t gfp_mask)
+{
+ struct page *page;
+
+ /* If we are using page_address(), we can not allow highmem */
+ VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
+
+ page = alloc_pages_exact(gfp_mask, size);
+ if (page)
+ return (void *) page_address(page);
+ return NULL;
}
EXPORT_SYMBOL(get_free_pages_exact);
@@ -2326,13 +2373,7 @@ EXPORT_SYMBOL(get_free_pages_exact);
*/
void free_pages_exact(void *virt, size_t size)
{
- unsigned long addr = (unsigned long)virt;
- unsigned long end = addr + PAGE_ALIGN(size);
-
- while (addr < end) {
- free_page(addr);
- addr += PAGE_SIZE;
- }
+ __free_pages_exact(virt_to_page(virt), size);
}
EXPORT_SYMBOL(free_pages_exact);
_
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