inet: frags: reorganize struct netns_frags

BugLink: https://bugs.launchpad.net/bugs/1818806

commit c2615cf5 upstream.

Put the read-mostly fields in a separate cache line
at the beginning of struct netns_frags, to reduce
false sharing noticed in inet_frag_kill()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

include/net/inet_frag.h

@@ -4,15 +4,16 @@
 #include <linux/rhashtable.h>
 
 struct netns_frags {
-	struct rhashtable       rhashtable ____cacheline_aligned_in_smp;
-
-	/* Keep atomic mem on separate cachelines in structs that include it */
-	atomic_long_t		mem ____cacheline_aligned_in_smp;
 	/* sysctls */
 	long			high_thresh;
 	long			low_thresh;
 	int			timeout;
 	struct inet_frags	*f;
+
+	struct rhashtable       rhashtable ____cacheline_aligned_in_smp;
+
+	/* Keep atomic mem on separate cachelines in structs that include it */
+	atomic_long_t		mem ____cacheline_aligned_in_smp;
 };
 
 /**