[RFC v11 08/14] mm: page_frag: some minor refactoring before adding new API

[Yunsheng Lin <linyunsheng@xxxxxxxxxx>]

Refactor common codes from __page_frag_alloc_va_align()
to __page_frag_cache_refill(), so that the new API can
make use of them.

CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Signed-off-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
---
 include/linux/page_frag_cache.h |  2 +-
 mm/page_frag_cache.c            | 93 +++++++++++++++++----------------
 2 files changed, 49 insertions(+), 46 deletions(-)

diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cache.h
index 12a16f8e8ad0..5aa45de7a9a5 100644
--- a/include/linux/page_frag_cache.h
+++ b/include/linux/page_frag_cache.h
@@ -50,7 +50,7 @@ static inline void *encoded_page_address(unsigned long encoded_va)
 
 static inline void page_frag_cache_init(struct page_frag_cache *nc)
 {
-	nc->encoded_va = 0;
+	memset(nc, 0, sizeof(*nc));
 }
 
 static inline bool page_frag_cache_is_pfmemalloc(struct page_frag_cache *nc)
diff --git a/mm/page_frag_cache.c b/mm/page_frag_cache.c
index 7928e5d50711..d9c9cad17af7 100644
--- a/mm/page_frag_cache.c
+++ b/mm/page_frag_cache.c
@@ -19,6 +19,28 @@
 #include <linux/page_frag_cache.h>
 #include "internal.h"
 
+static struct page *__page_frag_cache_recharge(struct page_frag_cache *nc)
+{
+	unsigned long encoded_va = nc->encoded_va;
+	struct page *page;
+
+	page = virt_to_page((void *)encoded_va);
+	if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
+		return NULL;
+
+	if (unlikely(encoded_page_pfmemalloc(encoded_va))) {
+		VM_BUG_ON(compound_order(page) !=
+			  encoded_page_order(encoded_va));
+		free_unref_page(page, encoded_page_order(encoded_va));
+		return NULL;
+	}
+
+	/* OK, page count is 0, we can safely set it */
+	set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
+
+	return page;
+}
+
 static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 					     gfp_t gfp_mask)
 {
@@ -26,6 +48,14 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	struct page *page = NULL;
 	gfp_t gfp = gfp_mask;
 
+	if (likely(nc->encoded_va)) {
+		page = __page_frag_cache_recharge(nc);
+		if (page) {
+			order = encoded_page_order(nc->encoded_va);
+			goto out;
+		}
+	}
+
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 	gfp_mask = (gfp_mask & ~__GFP_DIRECT_RECLAIM) |  __GFP_COMP |
 		   __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
@@ -35,7 +65,7 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	if (unlikely(!page)) {
 		page = alloc_pages_node(NUMA_NO_NODE, gfp, 0);
 		if (unlikely(!page)) {
-			nc->encoded_va = 0;
+			memset(nc, 0, sizeof(*nc));
 			return NULL;
 		}
 
@@ -45,6 +75,16 @@ static struct page *__page_frag_cache_refill(struct page_frag_cache *nc,
 	nc->encoded_va = encode_aligned_va(page_address(page), order,
 					   page_is_pfmemalloc(page));
 
+	/* Even if we own the page, we do not use atomic_set().
+	 * This would break get_page_unless_zero() users.
+	 */
+	page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
+
+out:
+	/* reset page count bias and remaining to start of new frag */
+	nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
+	nc->remaining = PAGE_SIZE << order;
+
 	return page;
 }
 
@@ -55,7 +95,7 @@ void page_frag_cache_drain(struct page_frag_cache *nc)
 
 	__page_frag_cache_drain(virt_to_head_page((void *)nc->encoded_va),
 				nc->pagecnt_bias);
-	nc->encoded_va = 0;
+	memset(nc, 0, sizeof(*nc));
 }
 EXPORT_SYMBOL(page_frag_cache_drain);
 
@@ -72,31 +112,9 @@ void *__page_frag_alloc_va_align(struct page_frag_cache *nc,
 				 unsigned int fragsz, gfp_t gfp_mask,
 				 unsigned int align_mask)
 {
-	unsigned long encoded_va = nc->encoded_va;
-	unsigned int size, remaining;
-	struct page *page;
-
-	if (unlikely(!encoded_va)) {
-refill:
-		page = __page_frag_cache_refill(nc, gfp_mask);
-		if (!page)
-			return NULL;
-
-		encoded_va = nc->encoded_va;
-		size = page_frag_cache_page_size(encoded_va);
+	unsigned int size = page_frag_cache_page_size(nc->encoded_va);
+	unsigned int remaining = nc->remaining & align_mask;
 
-		/* Even if we own the page, we do not use atomic_set().
-		 * This would break get_page_unless_zero() users.
-		 */
-		page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE);
-
-		/* reset page count bias and remaining to start of new frag */
-		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
-		nc->remaining = size;
-	}
-
-	size = page_frag_cache_page_size(encoded_va);
-	remaining = nc->remaining & align_mask;
 	if (unlikely(remaining < fragsz)) {
 		if (unlikely(fragsz > PAGE_SIZE)) {
 			/*
@@ -111,32 +129,17 @@ void *__page_frag_alloc_va_align(struct page_frag_cache *nc,
 			return NULL;
 		}
 
-		page = virt_to_page((void *)encoded_va);
-
-		if (!page_ref_sub_and_test(page, nc->pagecnt_bias))
-			goto refill;
-
-		if (unlikely(encoded_page_pfmemalloc(encoded_va))) {
-			VM_BUG_ON(compound_order(page) !=
-				  encoded_page_order(encoded_va));
-			free_unref_page(page, encoded_page_order(encoded_va));
-			goto refill;
-		}
-
-		/* OK, page count is 0, we can safely set it */
-		set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1);
-
-		/* reset page count bias and remaining to start of new frag */
-		nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1;
-		nc->remaining = size;
+		if (unlikely(!__page_frag_cache_refill(nc, gfp_mask)))
+			return NULL;
 
+		size = page_frag_cache_page_size(nc->encoded_va);
 		remaining = size;
 	}
 
 	nc->pagecnt_bias--;
 	nc->remaining = remaining - fragsz;
 
-	return encoded_page_address(encoded_va) + (size - remaining);
+	return encoded_page_address(nc->encoded_va) + (size - remaining);
 }
 EXPORT_SYMBOL(__page_frag_alloc_va_align);
 
-- 
2.33.0