net: skb: remove old comments about frag_size for build_skb()

Since commit ce098da1 ("skbuff: Introduce slab_build_skb()")
drivers trying to build skb around slab-backed buffers should
go via slab_build_skb() rather than passing frag_size = 0 to
the main build_skb().

Remove the copy'n'pasted comments about 0 meaning slab.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -386,8 +386,6 @@ struct sk_buff *__build_skb(void *data, unsigned int frag_size)
 
 /* build_skb() is wrapper over __build_skb(), that specifically
  * takes care of skb->head and skb->pfmemalloc
- * This means that if @frag_size is not zero, then @data must be backed
- * by a page fragment, not kmalloc() or vmalloc()
  */
 struct sk_buff *build_skb(void *data, unsigned int frag_size)
 {
@@ -406,7 +404,7 @@ EXPORT_SYMBOL(build_skb);
  * build_skb_around - build a network buffer around provided skb
  * @skb: sk_buff provide by caller, must be memset cleared
  * @data: data buffer provided by caller
- * @frag_size: size of data, or 0 if head was kmalloced
+ * @frag_size: size of data
  */
 struct sk_buff *build_skb_around(struct sk_buff *skb,
 				 void *data, unsigned int frag_size)
@@ -428,7 +426,7 @@ EXPORT_SYMBOL(build_skb_around);
 /**
  * __napi_build_skb - build a network buffer
  * @data: data buffer provided by caller
- * @frag_size: size of data, or 0 if head was kmalloced
+ * @frag_size: size of data
  *
  * Version of __build_skb() that uses NAPI percpu caches to obtain
  * skbuff_head instead of inplace allocation.
@@ -452,7 +450,7 @@ static struct sk_buff *__napi_build_skb(void *data, unsigned int frag_size)
 /**
  * napi_build_skb - build a network buffer
  * @data: data buffer provided by caller
- * @frag_size: size of data, or 0 if head was kmalloced
+ * @frag_size: size of data
  *
  * Version of __napi_build_skb() that takes care of skb->head_frag
  * and skb->pfmemalloc when the data is a page or page fragment.