cifs: smbd: Check send queue size before posting a send

Sometimes the remote peer may return more send credits than the send queue
depth. If all the send credits are used to post senasd, we may overflow the
send queue.

Fix this by checking the send queue size before posting a send.

Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 79d8dcbd0034368e029f4eed7779d2bd32f0c99d..c7ef2d7ce0ef8d391c8dfe0cb46ccdd287a61c8d 100644 (file)
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -287,6 +287,7 @@ static void send_done(struct ib_cq *cq, struct ib_wc *wc)
        if (atomic_dec_and_test(&request->info->send_pending))
                wake_up(&request->info->wait_send_pending);
 
+       wake_up(&request->info->wait_post_send);
 
        mempool_free(request, request->info->request_mempool);
 }
@@ -939,7 +940,14 @@ static int smbd_post_send(struct smbd_connection *info,
        send_wr.opcode = IB_WR_SEND;
        send_wr.send_flags = IB_SEND_SIGNALED;
 
-       atomic_inc(&info->send_pending);
+wait_sq:
+       wait_event(info->wait_post_send,
+               atomic_read(&info->send_pending) < info->send_credit_target);
+       if (unlikely(atomic_inc_return(&info->send_pending) >
+                               info->send_credit_target)) {
+               atomic_dec(&info->send_pending);
+               goto wait_sq;
+       }
 
        rc = ib_post_send(info->id->qp, &send_wr, NULL);
        if (rc) {
@@ -1733,6 +1741,7 @@ static struct smbd_connection *_smbd_get_connection(
        init_waitqueue_head(&info->wait_send_pending);
        atomic_set(&info->send_pending, 0);
 
+       init_waitqueue_head(&info->wait_post_send);
 
        INIT_WORK(&info->disconnect_work, smbd_disconnect_rdma_work);
        INIT_WORK(&info->post_send_credits_work, smbd_post_send_credits);

diff --git a/fs/cifs/smbdirect.h b/fs/cifs/smbdirect.h
index f70c7119a456ca4c8445864cdc34da854e6e8881..07c8f5638c3948a829d8ba4e21c25cd84267d993 100644 (file)
--- a/fs/cifs/smbdirect.h
+++ b/fs/cifs/smbdirect.h
@@ -114,6 +114,7 @@ struct smbd_connection {
        /* Activity accoutning */
        atomic_t send_pending;
        wait_queue_head_t wait_send_pending;
+       wait_queue_head_t wait_post_send;
 
        /* Receive queue */
        struct list_head receive_queue;