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Message-id: <1413287968-13940-8-git-send-email-heesub.shin@samsung.com>
Date: Tue, 14 Oct 2014 20:59:26 +0900
From: Heesub Shin <heesub.shin@...sung.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Seth Jennings <sjennings@...iantweb.net>
Cc: Nitin Gupta <ngupta@...are.org>, Dan Streetman <ddstreet@...e.org>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Sunae Seo <sunae.seo@...sung.com>,
Heesub Shin <heesub.shin@...sung.com>
Subject: [RFC PATCH 7/9] mm/zbud: drop zbud_header
Now that the only field in zbud_header is .under_reclaim, get it out of
the struct and let PG_reclaim bit in page->flags take over. As a result
of this change, we can finally eliminate the struct zbud_header, and
hence all the internal data structures of zbud live in struct page.
Signed-off-by: Heesub Shin <heesub.shin@...sung.com>
---
mm/zbud.c | 66 +++++++++++++++++----------------------------------------------
1 file changed, 18 insertions(+), 48 deletions(-)
diff --git a/mm/zbud.c b/mm/zbud.c
index 8a6dd6b..5a392f3 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -60,17 +60,15 @@
* NCHUNKS_ORDER determines the internal allocation granularity, effectively
* adjusting internal fragmentation. It also determines the number of
* freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
- * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk
- * in allocated page is occupied by zbud header, NCHUNKS will be calculated to
- * 63 which shows the max number of free chunks in zbud page, also there will be
- * 63 freelists per pool.
+ * allocation granularity will be in chunks of size PAGE_SIZE/64.
+ * NCHUNKS will be calculated to 64 which shows the max number of free
+ * chunks in zbud page, also there will be 64 freelists per pool.
*/
#define NCHUNKS_ORDER 6
#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
#define CHUNK_SIZE (1 << CHUNK_SHIFT)
-#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
-#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
+#define NCHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
/**
* struct zbud_pool - stores metadata for each zbud pool
@@ -96,14 +94,6 @@ struct zbud_pool {
struct zbud_ops *ops;
};
-/*
- * struct zbud_header - zbud page metadata occupying the first chunk of each
- * zbud page.
- */
-struct zbud_header {
- bool under_reclaim;
-};
-
/*****************
* zpool
****************/
@@ -220,22 +210,19 @@ static size_t get_num_chunks(struct page *page, enum buddy bud)
#define for_each_unbuddied_list(_iter, _begin) \
for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
-/* Initializes the zbud header of a newly allocated zbud page */
+/* Initializes a newly allocated zbud page */
static void init_zbud_page(struct page *page)
{
- struct zbud_header *zhdr = page_address(page);
set_num_chunks(page, FIRST, 0);
set_num_chunks(page, LAST, 0);
INIT_LIST_HEAD((struct list_head *) &page->index);
INIT_LIST_HEAD(&page->lru);
- zhdr->under_reclaim = 0;
+ ClearPageReclaim(page);
}
/* Resets the struct page fields and frees the page */
-static void free_zbud_page(struct zbud_header *zhdr)
+static void free_zbud_page(struct page *page)
{
- struct page *page = virt_to_page(zhdr);
-
init_page_count(page);
page_mapcount_reset(page);
__free_page(page);
@@ -261,14 +248,6 @@ static struct page *handle_to_zbud_page(unsigned long handle)
return (struct page *) (handle & ~LAST);
}
-/* Returns the zbud page where a given handle is stored */
-static struct zbud_header *handle_to_zbud_header(unsigned long handle)
-{
- struct page *page = handle_to_zbud_page(handle);
-
- return page_address(page);
-}
-
/* Returns the number of free chunks in a zbud page */
static int num_free_chunks(struct page *page)
{
@@ -347,7 +326,7 @@ int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp,
if (!size || (gfp & __GFP_HIGHMEM))
return -EINVAL;
- if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
+ if (size > PAGE_SIZE - CHUNK_SIZE)
return -ENOSPC;
chunks = size_to_chunks(size);
spin_lock(&pool->lock);
@@ -410,21 +389,18 @@ found:
*/
void zbud_free(struct zbud_pool *pool, unsigned long handle)
{
- struct zbud_header *zhdr;
struct page *page;
int freechunks;
spin_lock(&pool->lock);
- zhdr = handle_to_zbud_header(handle);
- page = virt_to_page(zhdr);
+ page = handle_to_zbud_page(handle);
- /* If first buddy, handle will be page aligned */
- if ((handle - ZHDR_SIZE_ALIGNED) & ~PAGE_MASK)
- set_num_chunks(page, LAST, 0);
- else
+ if (!is_last_chunk(handle))
set_num_chunks(page, FIRST, 0);
+ else
+ set_num_chunks(page, LAST, 0);
- if (zhdr->under_reclaim) {
+ if (PageReclaim(page)) {
/* zbud page is under reclaim, reclaim will free */
spin_unlock(&pool->lock);
return;
@@ -436,7 +412,7 @@ void zbud_free(struct zbud_pool *pool, unsigned long handle)
list_del((struct list_head *) &page->index);
/* zbud page is empty, free */
list_del(&page->lru);
- free_zbud_page(zhdr);
+ free_zbud_page(page);
pool->pages_nr--;
} else {
/* Add to unbuddied list */
@@ -489,7 +465,6 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
{
int i, ret, freechunks;
struct page *page;
- struct zbud_header *zhdr;
unsigned long first_handle, last_handle;
spin_lock(&pool->lock);
@@ -500,11 +475,10 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
}
for (i = 0; i < retries; i++) {
page = list_tail_entry(&pool->lru, struct page, lru);
- zhdr = page_address(page);
list_del(&page->lru);
list_del((struct list_head *) &page->index);
/* Protect zbud page against free */
- zhdr->under_reclaim = true;
+ SetPageReclaim(page);
/*
* We need encode the handles before unlocking, since we can
* race with free that will set (first|last)_chunks to 0
@@ -530,14 +504,14 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries)
}
next:
spin_lock(&pool->lock);
- zhdr->under_reclaim = false;
+ ClearPageReclaim(page);
freechunks = num_free_chunks(page);
if (freechunks == NCHUNKS) {
/*
* Both buddies are now free, free the zbud page and
* return success.
*/
- free_zbud_page(zhdr);
+ free_zbud_page(page);
pool->pages_nr--;
spin_unlock(&pool->lock);
return 0;
@@ -569,14 +543,12 @@ next:
*/
void *zbud_map(struct zbud_pool *pool, unsigned long handle)
{
- size_t offset;
+ size_t offset = 0;
struct page *page = handle_to_zbud_page(handle);
if (is_last_chunk(handle))
offset = PAGE_SIZE -
(get_num_chunks(page, LAST) << CHUNK_SHIFT);
- else
- offset = ZHDR_SIZE_ALIGNED;
return (unsigned char *) page_address(page) + offset;
}
@@ -604,8 +576,6 @@ u64 zbud_get_pool_size(struct zbud_pool *pool)
static int __init init_zbud(void)
{
- /* Make sure the zbud header will fit in one chunk */
- BUILD_BUG_ON(sizeof(struct zbud_header) > ZHDR_SIZE_ALIGNED);
pr_info("loaded\n");
#ifdef CONFIG_ZPOOL
--
1.9.1
--
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