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-rw-r--r--include/linux/gfp.h23
-rw-r--r--include/net/sock.h11
2 files changed, 31 insertions, 3 deletions
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index fb07b503dc45..61f2f6ff9467 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -325,6 +325,29 @@ static inline bool gfpflags_allow_blocking(const gfp_t gfp_flags)
return !!(gfp_flags & __GFP_DIRECT_RECLAIM);
}
+/**
+ * gfpflags_normal_context - is gfp_flags a normal sleepable context?
+ * @gfp_flags: gfp_flags to test
+ *
+ * Test whether @gfp_flags indicates that the allocation is from the
+ * %current context and allowed to sleep.
+ *
+ * An allocation being allowed to block doesn't mean it owns the %current
+ * context. When direct reclaim path tries to allocate memory, the
+ * allocation context is nested inside whatever %current was doing at the
+ * time of the original allocation. The nested allocation may be allowed
+ * to block but modifying anything %current owns can corrupt the outer
+ * context's expectations.
+ *
+ * %true result from this function indicates that the allocation context
+ * can sleep and use anything that's associated with %current.
+ */
+static inline bool gfpflags_normal_context(const gfp_t gfp_flags)
+{
+ return (gfp_flags & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC)) ==
+ __GFP_DIRECT_RECLAIM;
+}
+
#ifdef CONFIG_HIGHMEM
#define OPT_ZONE_HIGHMEM ZONE_HIGHMEM
#else
diff --git a/include/net/sock.h b/include/net/sock.h
index f69b58bff7e5..c31a9ed86d5a 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2242,12 +2242,17 @@ struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
* sk_page_frag - return an appropriate page_frag
* @sk: socket
*
- * If socket allocation mode allows current thread to sleep, it means its
- * safe to use the per task page_frag instead of the per socket one.
+ * Use the per task page_frag instead of the per socket one for
+ * optimization when we know that we're in the normal context and owns
+ * everything that's associated with %current.
+ *
+ * gfpflags_allow_blocking() isn't enough here as direct reclaim may nest
+ * inside other socket operations and end up recursing into sk_page_frag()
+ * while it's already in use.
*/
static inline struct page_frag *sk_page_frag(struct sock *sk)
{
- if (gfpflags_allow_blocking(sk->sk_allocation))
+ if (gfpflags_normal_context(sk->sk_allocation))
return &current->task_frag;
return &sk->sk_frag;