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-rw-r--r--net/core/skbuff.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 10bde7c6db44..30b523fa4ad2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5276,11 +5276,18 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
if (skb_cloned(to))
return false;
- /* The page pool signature of struct page will eventually figure out
- * which pages can be recycled or not but for now let's prohibit slab
- * allocated and page_pool allocated SKBs from being coalesced.
+ /* In general, avoid mixing slab allocated and page_pool allocated
+ * pages within the same SKB. However when @to is not pp_recycle and
+ * @from is cloned, we can transition frag pages from page_pool to
+ * reference counted.
+ *
+ * On the other hand, don't allow coalescing two pp_recycle SKBs if
+ * @from is cloned, in case the SKB is using page_pool fragment
+ * references (PP_FLAG_PAGE_FRAG). Since we only take full page
+ * references for cloned SKBs at the moment that would result in
+ * inconsistent reference counts.
*/
- if (to->pp_recycle != from->pp_recycle)
+ if (to->pp_recycle != (from->pp_recycle && !skb_cloned(from)))
return false;
if (len <= skb_tailroom(to)) {