net: factorize code in kmalloc_reserve()

All kmalloc_reserve() callers have to make the same computation,
we can factorize them, to prepare following patch in the series.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/skbuff.c

@@ -478,25 +478,28 @@ EXPORT_SYMBOL(napi_build_skb);
  * may be used. Otherwise, the packet data may be discarded until enough
  * memory is free
  */
-static void *kmalloc_reserve(size_t size, gfp_t flags, int node,
+static void *kmalloc_reserve(unsigned int *size, gfp_t flags, int node,
 			     bool *pfmemalloc)
 {
-	void *obj;
 	bool ret_pfmemalloc = false;
+	unsigned int obj_size;
+	void *obj;
 
+	obj_size = SKB_HEAD_ALIGN(*size);
+	*size = obj_size = kmalloc_size_roundup(obj_size);
 	/*
 	 * Try a regular allocation, when that fails and we're not entitled
 	 * to the reserves, fail.
 	 */
-	obj = kmalloc_node_track_caller(size,
+	obj = kmalloc_node_track_caller(obj_size,
 					flags | __GFP_NOMEMALLOC | __GFP_NOWARN,
 					node);
 	if (obj || !(gfp_pfmemalloc_allowed(flags)))
 		goto out;
 
 	/* Try again but now we are using pfmemalloc reserves */
 	ret_pfmemalloc = true;
-	obj = kmalloc_node_track_caller(size, flags, node);
+	obj = kmalloc_node_track_caller(obj_size, flags, node);
 
 out:
 	if (pfmemalloc)
@@ -557,9 +560,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	 * aligned memory blocks, unless SLUB/SLAB debug is enabled.
 	 * Both skb->head and skb_shared_info are cache line aligned.
 	 */
-	size = SKB_HEAD_ALIGN(size);
-	size = kmalloc_size_roundup(size);
-	data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc);
+	data = kmalloc_reserve(&size, gfp_mask, node, &pfmemalloc);
 	if (unlikely(!data))
 		goto nodata;
 	/* kmalloc_size_roundup() might give us more room than requested.
@@ -1933,9 +1934,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_HEAD_ALIGN(size);
-	size = kmalloc_size_roundup(size);
-	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+	data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)
 		goto nodata;
 	size = SKB_WITH_OVERHEAD(size);
@@ -6283,9 +6282,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_HEAD_ALIGN(size);
-	size = kmalloc_size_roundup(size);
-	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+	data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)
 		return -ENOMEM;
 	size = SKB_WITH_OVERHEAD(size);
@@ -6401,9 +6398,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
 	if (skb_pfmemalloc(skb))
 		gfp_mask |= __GFP_MEMALLOC;
 
-	size = SKB_HEAD_ALIGN(size);
-	size = kmalloc_size_roundup(size);
-	data = kmalloc_reserve(size, gfp_mask, NUMA_NO_NODE, NULL);
+	data = kmalloc_reserve(&size, gfp_mask, NUMA_NO_NODE, NULL);
 	if (!data)
 		return -ENOMEM;
 	size = SKB_WITH_OVERHEAD(size);