tcp: align tcp_sock_write_rx group

Stephen Rothwell and kernel test robot reported that some arches
(parisc, hexagon) and/or compilers would not like blamed commit.

Lets make sure tcp_sock_write_rx group does not start with a hole.

While we are at it, correct tcp_sock_write_tx CACHELINE_ASSERT_GROUP_SIZE()
since after the blamed commit, we went to 105 bytes.

Fixes: 99123622 ("tcp: remove some holes in struct tcp_sock")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/netdev/20240301121108.5d39e4f9@canb.auug.org.au/
Closes: https://lore.kernel.org/oe-kbuild-all/202403011451.csPYOS3C-lkp@intel.com/Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Tested-by: Simon Horman <horms@kernel.org> # build-tested
Link: https://lore.kernel.org/r/20240301171945.2958176-1-edumazet@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/tcp.h

@@ -304,7 +304,7 @@ struct tcp_sock {
 	__cacheline_group_end(tcp_sock_write_txrx);
 
 	/* RX read-write hotpath cache lines */
-	__cacheline_group_begin(tcp_sock_write_rx);
+	__cacheline_group_begin(tcp_sock_write_rx) __aligned(8);
 	u64	bytes_received;
 				/* RFC4898 tcpEStatsAppHCThruOctetsReceived
 				 * sum(delta(rcv_nxt)), or how many bytes

net/ipv4/tcp.c

@@ -4651,7 +4651,7 @@ static void __init tcp_struct_check(void)
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_tx, tsorted_sent_queue);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_tx, highest_sack);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_tx, ecn_flags);
-	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_tx, 113);
+	CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_tx, 105);
 
 	/* TXRX read-write hotpath cache lines */
 	CACHELINE_ASSERT_GROUP_MEMBER(struct tcp_sock, tcp_sock_write_txrx, pred_flags);