net/smc: pay attention to MAX_ORDER for CQ entries

smc allocates a certain number of CQ entries for used RoCE devices. For
mlx5 devices the chosen constant number results in a large allocation
causing this warning:

[13355.124656] WARNING: CPU: 3 PID: 16535 at mm/page_alloc.c:3883 __alloc_pages_nodemask+0x2be/0x10c0
[13355.124657] Modules linked in: smc_diag(O) smc(O) xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ip6table_filter ip6_tables iptable_filter mlx5_ib ib_core sunrpc mlx5_core s390_trng rng_core ghash_s390 prng aes_s390 des_s390 des_generic sha512_s390 sha256_s390 sha1_s390 sha_common ptp pps_core eadm_sch dm_multipath dm_mod vhost_net tun vhost tap sch_fq_codel kvm ip_tables x_tables autofs4 [last unloaded: smc]
[13355.124672] CPU: 3 PID: 16535 Comm: kworker/3:0 Tainted: G           O    4.14.0uschi #1
[13355.124673] Hardware name: IBM 3906 M04 704 (LPAR)
[13355.124675] Workqueue: events smc_listen_work [smc]
[13355.124677] task: 00000000e2f22100 task.stack: 0000000084720000
[13355.124678] Krnl PSW : 0704c00180000000 000000000029da76 (__alloc_pages_nodemask+0x2be/0x10c0)
[13355.124681]            R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3
[13355.124682] Krnl GPRS: 0000000000000000 00550e00014080c0 0000000000000000 0000000000000001
[13355.124684]            000000000029d8b6 00000000f3bfd710 0000000000000000 00000000014080c0
[13355.124685]            0000000000000009 00000000ec277a00 0000000000200000 0000000000000000
[13355.124686]            0000000000000000 00000000000001ff 000000000029d8b6 0000000084723720
[13355.124708] Krnl Code: 000000000029da6a: a7110200		tmll	%r1,512
                          000000000029da6e: a774ff29		brc	7,29d8c0
                         #000000000029da72: a7f40001		brc	15,29da74
                         >000000000029da76: a7f4ff25		brc	15,29d8c0
                          000000000029da7a: a7380000		lhi	%r3,0
                          000000000029da7e: a7f4fef1		brc	15,29d860
                          000000000029da82: 5820f0c4		l	%r2,196(%r15)
                          000000000029da86: a53e0048		llilh	%r3,72
[13355.124720] Call Trace:
[13355.124722] ([<000000000029d8b6>] __alloc_pages_nodemask+0xfe/0x10c0)
[13355.124724]  [<000000000013bd1e>] s390_dma_alloc+0x6e/0x148
[13355.124733]  [<000003ff802eeba6>] mlx5_dma_zalloc_coherent_node+0x8e/0xe0 [mlx5_core]
[13355.124740]  [<000003ff802eee18>] mlx5_buf_alloc_node+0x70/0x108 [mlx5_core]
[13355.124744]  [<000003ff804eb410>] mlx5_ib_create_cq+0x558/0x898 [mlx5_ib]
[13355.124749]  [<000003ff80407d40>] ib_create_cq+0x48/0x88 [ib_core]
[13355.124751]  [<000003ff80109fba>] smc_ib_setup_per_ibdev+0x52/0x118 [smc]
[13355.124753]  [<000003ff8010bcb6>] smc_conn_create+0x65e/0x728 [smc]
[13355.124755]  [<000003ff801081a2>] smc_listen_work+0x2d2/0x540 [smc]
[13355.124756]  [<0000000000162c66>] process_one_work+0x1be/0x440
[13355.124758]  [<0000000000162f40>] worker_thread+0x58/0x458
[13355.124759]  [<0000000000169e7e>] kthread+0x14e/0x168
[13355.124760]  [<00000000009ce8be>] kernel_thread_starter+0x6/0xc
[13355.124762]  [<00000000009ce8b8>] kernel_thread_starter+0x0/0xc
[13355.124762] Last Breaking-Event-Address:
[13355.124764]  [<000000000029da72>] __alloc_pages_nodemask+0x2ba/0x10c0
[13355.124764] ---[ end trace 34be38b581c0b585 ]---

This patch reduces the smc constant for the maximum number of allocated
completion queue entries SMC_MAX_CQE by 2 to avoid high round up values
in the mlx5 code, and reduces the number of allocated completion queue
entries even more, if the final allocation for an mlx5 device hits the
MAX_ORDER limit.

Reported-by: Ihnken Menssen <menssen@de.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_ib.c

@@ -23,6 +23,8 @@
 #include "smc_wr.h"
 #include "smc.h"
 
+#define SMC_MAX_CQE 32766	/* max. # of completion queue elements */
+
 #define SMC_QP_MIN_RNR_TIMER		5
 #define SMC_QP_TIMEOUT			15 /* 4096 * 2 ** timeout usec */
 #define SMC_QP_RETRY_CNT			7 /* 7: infinite */
@@ -438,9 +440,15 @@ out:
 long smc_ib_setup_per_ibdev(struct smc_ib_device *smcibdev)
 {
 	struct ib_cq_init_attr cqattr =	{
-		.cqe = SMC_WR_MAX_CQE, .comp_vector = 0 };
+		.cqe = SMC_MAX_CQE, .comp_vector = 0 };
+	int cqe_size_order, smc_order;
 	long rc;
 
+	/* the calculated number of cq entries fits to mlx5 cq allocation */
+	cqe_size_order = cache_line_size() == 128 ? 7 : 6;
+	smc_order = MAX_ORDER - cqe_size_order - 1;
+	if (SMC_MAX_CQE + 2 > (0x00000001 << smc_order) * PAGE_SIZE)
+		cqattr.cqe = (0x00000001 << smc_order) * PAGE_SIZE - 2;
 	smcibdev->roce_cq_send = ib_create_cq(smcibdev->ibdev,
 					      smc_wr_tx_cq_handler, NULL,
 					      smcibdev, &cqattr);

net/smc/smc_wr.h

@@ -19,7 +19,6 @@
 #include "smc.h"
 #include "smc_core.h"
 
-#define SMC_WR_MAX_CQE 32768	/* max. # of completion queue elements */
 #define SMC_WR_BUF_CNT 16	/* # of ctrl buffers per link */
 
 #define SMC_WR_TX_WAIT_FREE_SLOT_TIME	(10 * HZ)