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Commit 0531b2aa authored by Linus Torvalds's avatar Linus Torvalds
Browse files

mm: add new 'read_cache_page_gfp()' helper function 



It's a simplified 'read_cache_page()' which takes a page allocation
flag, so that different paths can control how aggressive the memory
allocations are that populate a address space.

In particular, the intel GPU object mapping code wants to be able to do
a certain amount of own internal memory management by automatically
shrinking the address space when memory starts getting tight.  This
allows it to dynamically use different memory allocation policies on a
per-allocation basis, rather than depend on the (static) address space
gfp policy.

The actual new function is a one-liner, but re-organizing the helper
functions to the point where you can do this with a single line of code
is what most of the patch is all about.

Tested-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent caf0801e

include/linux/pagemap.h

+2 −0
Original line number Diff line number Diff line
@@ -253,6 +253,8 @@ extern struct page * read_cache_page_async(struct address_space *mapping, 
extern struct page * read_cache_page(struct address_space *mapping,

				pgoff_t index, filler_t *filler,

				void *data);

extern struct page * read_cache_page_gfp(struct address_space *mapping,

				pgoff_t index, gfp_t gfp_mask);

extern int read_cache_pages(struct address_space *mapping,

		struct list_head *pages, filler_t *filler, void *data);

mm/filemap.c

+68 −32
Original line number Diff line number Diff line
@@ -1634,14 +1634,15 @@ EXPORT_SYMBOL(generic_file_readonly_mmap); 
static struct page *__read_cache_page(struct address_space *mapping,

				pgoff_t index,

				int (*filler)(void *,struct page*),

				void *data)

				void *data,

				gfp_t gfp)

{

	struct page *page;

	int err;

repeat:

	page = find_get_page(mapping, index);

	if (!page) {

		page = page_cache_alloc_cold(mapping);

		page = __page_cache_alloc(gfp | __GFP_COLD);

		if (!page)

			return ERR_PTR(-ENOMEM);

		err = add_to_page_cache_lru(page, mapping, index, GFP_KERNEL);
@@ -1661,31 +1662,18 @@ static struct page *__read_cache_page(struct address_space *mapping, 
	return page;

}



/**

 * read_cache_page_async - read into page cache, fill it if needed

 * @mapping:	the page's address_space

 * @index:	the page index

 * @filler:	function to perform the read

 * @data:	destination for read data

 *

 * Same as read_cache_page, but don't wait for page to become unlocked

 * after submitting it to the filler.

 *

 * Read into the page cache. If a page already exists, and PageUptodate() is

 * not set, try to fill the page but don't wait for it to become unlocked.

 *

 * If the page does not get brought uptodate, return -EIO.

 */

struct page *read_cache_page_async(struct address_space *mapping,

static struct page *do_read_cache_page(struct address_space *mapping,

				pgoff_t index,

				int (*filler)(void *,struct page*),

				void *data)

				void *data,

				gfp_t gfp)



{

	struct page *page;

	int err;



retry:

	page = __read_cache_page(mapping, index, filler, data);

	page = __read_cache_page(mapping, index, filler, data, gfp);

	if (IS_ERR(page))

		return page;

	if (PageUptodate(page))
@@ -1710,38 +1698,86 @@ struct page *read_cache_page_async(struct address_space *mapping, 
	mark_page_accessed(page);

	return page;

}

EXPORT_SYMBOL(read_cache_page_async);



/**

 * read_cache_page - read into page cache, fill it if needed

 * read_cache_page_async - read into page cache, fill it if needed

 * @mapping:	the page's address_space

 * @index:	the page index

 * @filler:	function to perform the read

 * @data:	destination for read data

 *

 * Same as read_cache_page, but don't wait for page to become unlocked

 * after submitting it to the filler.

 *

 * Read into the page cache. If a page already exists, and PageUptodate() is

 * not set, try to fill the page then wait for it to become unlocked.

 * not set, try to fill the page but don't wait for it to become unlocked.

 *

 * If the page does not get brought uptodate, return -EIO.

 */

struct page *read_cache_page(struct address_space *mapping,

struct page *read_cache_page_async(struct address_space *mapping,

				pgoff_t index,

				int (*filler)(void *,struct page*),

				void *data)

{

	struct page *page;

	return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));

}

EXPORT_SYMBOL(read_cache_page_async);



	page = read_cache_page_async(mapping, index, filler, data);

	if (IS_ERR(page))

		goto out;

static struct page *wait_on_page_read(struct page *page)

{

	if (!IS_ERR(page)) {

		wait_on_page_locked(page);

		if (!PageUptodate(page)) {

			page_cache_release(page);

			page = ERR_PTR(-EIO);

		}

 out:

	}

	return page;

}



/**

 * read_cache_page_gfp - read into page cache, using specified page allocation flags.

 * @mapping:	the page's address_space

 * @index:	the page index

 * @gfp:	the page allocator flags to use if allocating

 *

 * This is the same as "read_mapping_page(mapping, index, NULL)", but with

 * any new page allocations done using the specified allocation flags. Note

 * that the Radix tree operations will still use GFP_KERNEL, so you can't

 * expect to do this atomically or anything like that - but you can pass in

 * other page requirements.

 *

 * If the page does not get brought uptodate, return -EIO.

 */

struct page *read_cache_page_gfp(struct address_space *mapping,

				pgoff_t index,

				gfp_t gfp)

{

	filler_t *filler = (filler_t *)mapping->a_ops->readpage;



	return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));

}

EXPORT_SYMBOL(read_cache_page_gfp);



/**

 * read_cache_page - read into page cache, fill it if needed

 * @mapping:	the page's address_space

 * @index:	the page index

 * @filler:	function to perform the read

 * @data:	destination for read data

 *

 * Read into the page cache. If a page already exists, and PageUptodate() is

 * not set, try to fill the page then wait for it to become unlocked.

 *

 * If the page does not get brought uptodate, return -EIO.

 */

struct page *read_cache_page(struct address_space *mapping,

				pgoff_t index,

				int (*filler)(void *,struct page*),

				void *data)

{

	return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));

}

EXPORT_SYMBOL(read_cache_page);



/*