net/smc: Decouple sf and attached send_buf in smc_loopback

Before this patch there was the following assumption in
smc_loopback.c>smc_lo_move_data():
sf (signalling flag) == 0 : data is already in an attached target dmb
sf == 1 : data is not yet in the target dmb

This is true for the 2 callers in smc client
smcd_cdc_msg_send() : sf=1
smcd_tx_rdma_writes() : sf=0
but should not be a general assumption.

Add a bool to struct smc_buf_desc to indicate whether an SMC-D sndbuf_desc
is an attached buffer. Don't call move_data() for attached send_buffers,
because it is not necessary.

Move the data in smc_lo_move_data() if len != 0 and signal when requested.

Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Link: https://patch.msgid.link/20250918110500.1731261-3-wintera@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 48a1b1dcb576e1c24a4319d0b28a667612dc3ad7..a5a78cbff3411147b9431cd91f1315a4fd80c518 100644 (file)
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -13,6 +13,7 @@
 #define _SMC_CORE_H
 
 #include <linux/atomic.h>
+#include <linux/types.h>
 #include <linux/smc.h>
 #include <linux/pci.h>
 #include <rdma/ib_verbs.h>
@@ -221,6 +222,10 @@ struct smc_buf_desc {
                                        /* virtually contiguous */
                };
                struct { /* SMC-D */
+                       /* SMC-D tx buffer */
+                       bool            is_attached;
+                                       /* no need for explicit writes */
+                        /* SMC-D rx buffer: */
                        unsigned short  sba_idx;
                                        /* SBA index number */
                        u64             token;

diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
index fca01b95b65a375d2abc8509870e9637f351bc55..503a9f93b392d4390f63f642f45f92b882261627 100644 (file)
--- a/net/smc/smc_ism.c
+++ b/net/smc/smc_ism.c
@@ -274,6 +274,7 @@ int smc_ism_attach_dmb(struct smcd_dev *dev, u64 token,
                dmb_desc->cpu_addr = dmb.cpu_addr;
                dmb_desc->dma_addr = dmb.dma_addr;
                dmb_desc->len = dmb.dmb_len;
+               dmb_desc->is_attached = true;
        }
        return rc;
 }

diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index 0eb00bbefd174898e99e8a6a6cbe6a1a3f914331..1853c26fbbbb0a532b08306e1c0021217a519978 100644 (file)
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -224,12 +224,6 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
        struct smc_lo_dev *ldev = smcd->priv;
        struct smc_connection *conn;
 
-       if (!sf)
-               /* since sndbuf is merged with peer DMB, there is
-                * no need to copy data from sndbuf to peer DMB.
-                */
-               return 0;
-
        read_lock_bh(&ldev->dmb_ht_lock);
        hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) {
                if (tmp_node->token == dmb_tok) {
@@ -244,6 +238,9 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
        memcpy((char *)rmb_node->cpu_addr + offset, data, size);
        read_unlock_bh(&ldev->dmb_ht_lock);
 
+       if (!sf)
+               return 0;
+
        conn = smcd->conn[rmb_node->sba_idx];
        if (!conn || conn->killed)
                return -EPIPE;

diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index 214ac3cbcf9ad37cea2062a9400658e40803578c..3144b4b1fe29013cabc63d72671d256761a4c367 100644 (file)
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -426,6 +426,9 @@ static int smcd_tx_rdma_writes(struct smc_connection *conn, size_t len,
        int srcchunk, dstchunk;
        int rc;
 
+       if (conn->sndbuf_desc->is_attached)
+               return 0;
+
        for (dstchunk = 0; dstchunk < 2; dstchunk++) {
                for (srcchunk = 0; srcchunk < 2; srcchunk++) {
                        void *data = conn->sndbuf_desc->cpu_addr + src_off;