smb: server: simplify sibling_list handling in smb_direct_flush_send_list/send_done

We have a list handling that is much easier to understand:

1. Before smb_direct_flush_send_list() is called all
   struct smbdirect_send_io messages are part of
   send_ctx->msg_list

2. Before smb_direct_flush_send_list() calls
   smb_direct_post_send() we remove the last
   element in send_ctx->msg_list and move all
   others into last->sibling_list. As only
   last has IB_SEND_SIGNALED and gets a completion
   vis send_done().

3. send_done() has an easy way to free all others
   in sendmsg->sibling_list (if there are any).
   And use list_for_each_entry_safe() instead of
   a complex custom logic.

This will help us to share send_done() in common
code soon, as it will work fine for the client too,
where last->sibling_list is currently always an empty list.

Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index 9dabaf74db312388f3807aadfa65ab3180ac2199..2aa8e4d4c9121717b8f3f45b5969d240cb716e1a 100644 (file)
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -523,6 +523,12 @@ static void smb_direct_free_sendmsg(struct smbdirect_socket *sc,
 {
        int i;
 
+       /*
+        * The list needs to be empty!
+        * The caller should take care of it.
+        */
+       WARN_ON_ONCE(!list_empty(&msg->sibling_list));
+
        if (msg->num_sge > 0) {
                ib_dma_unmap_single(sc->ib.dev,
                                    msg->sge[0].addr, msg->sge[0].length,
@@ -908,9 +914,8 @@ static void smb_direct_post_recv_credits(struct work_struct *work)
 
 static void send_done(struct ib_cq *cq, struct ib_wc *wc)
 {
-       struct smbdirect_send_io *sendmsg, *sibling;
+       struct smbdirect_send_io *sendmsg, *sibling, *next;
        struct smbdirect_socket *sc;
-       struct list_head *pos, *prev, *end;
 
        sendmsg = container_of(wc->wr_cqe, struct smbdirect_send_io, cqe);
        sc = sendmsg->socket;
@@ -919,27 +924,26 @@ static void send_done(struct ib_cq *cq, struct ib_wc *wc)
                    ib_wc_status_msg(wc->status), wc->status,
                    wc->opcode);
 
+       /*
+        * Free possible siblings and then the main send_io
+        */
+       list_for_each_entry_safe(sibling, next, &sendmsg->sibling_list, sibling_list) {
+               list_del_init(&sibling->sibling_list);
+               smb_direct_free_sendmsg(sc, sibling);
+       }
+       /* Note this frees wc->wr_cqe, but not wc */
+       smb_direct_free_sendmsg(sc, sendmsg);
+
        if (wc->status != IB_WC_SUCCESS || wc->opcode != IB_WC_SEND) {
                pr_err("Send error. status='%s (%d)', opcode=%d\n",
                       ib_wc_status_msg(wc->status), wc->status,
                       wc->opcode);
                smb_direct_disconnect_rdma_connection(sc);
+               return;
        }
 
        if (atomic_dec_and_test(&sc->send_io.pending.count))
                wake_up(&sc->send_io.pending.zero_wait_queue);
-
-       /* iterate and free the list of messages in reverse. the list's head
-        * is invalid.
-        */
-       for (pos = &sendmsg->sibling_list, prev = pos->prev, end = sendmsg->sibling_list.next;
-            prev != end; pos = prev, prev = prev->prev) {
-               sibling = container_of(pos, struct smbdirect_send_io, sibling_list);
-               smb_direct_free_sendmsg(sc, sibling);
-       }
-
-       sibling = container_of(pos, struct smbdirect_send_io, sibling_list);
-       smb_direct_free_sendmsg(sc, sibling);
 }
 
 static int manage_credits_prior_sending(struct smbdirect_socket *sc)
@@ -1029,17 +1033,29 @@ static int smb_direct_flush_send_list(struct smbdirect_socket *sc,
        last->wr.send_flags = IB_SEND_SIGNALED;
        last->wr.wr_cqe = &last->cqe;
 
+       /*
+        * Remove last from send_ctx->msg_list
+        * and splice the rest of send_ctx->msg_list
+        * to last->sibling_list.
+        *
+        * send_ctx->msg_list is a valid empty list
+        * at the end.
+        */
+       list_del_init(&last->sibling_list);
+       list_splice_tail_init(&send_ctx->msg_list, &last->sibling_list);
+       send_ctx->wr_cnt = 0;
+
        ret = smb_direct_post_send(sc, &first->wr);
-       if (!ret) {
-               smb_direct_send_ctx_init(send_ctx,
-                                        send_ctx->need_invalidate_rkey,
-                                        send_ctx->remote_key);
-       } else {
-               list_for_each_entry_safe(first, last, &send_ctx->msg_list,
-                                        sibling_list) {
-                       smb_direct_free_sendmsg(sc, first);
+       if (ret) {
+               struct smbdirect_send_io *sibling, *next;
+
+               list_for_each_entry_safe(sibling, next, &last->sibling_list, sibling_list) {
+                       list_del_init(&sibling->sibling_list);
+                       smb_direct_free_sendmsg(sc, sibling);
                }
+               smb_direct_free_sendmsg(sc, last);
        }
+
        return ret;
 }