RDMA/ucma: Change backlog into an atomic

There is no reason to grab the file->mut just to do this inc/dec work. Use
an atomic.

Link: https://lore.kernel.org/r/20200818120526.702120-12-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index ad78b05..8be8ff1 100644 (file)
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -88,7 +88,7 @@ struct ucma_context {
        struct completion       comp;
        refcount_t              ref;
        int                     events_reported;
-       int                     backlog;
+       atomic_t                backlog;
 
        struct ucma_file        *file;
        struct rdma_cm_id       *cm_id;
@@ -348,12 +348,11 @@ static int ucma_event_handler(struct rdma_cm_id *cm_id,
        uevent->resp.ece.attr_mod = event->ece.attr_mod;
 
        if (event->event == RDMA_CM_EVENT_CONNECT_REQUEST) {
-               if (!ctx->backlog) {
+               if (!atomic_add_unless(&ctx->backlog, -1, 0)) {
                        ret = -ENOMEM;
                        kfree(uevent);
                        goto out;
                }
-               ctx->backlog--;
        } else if (!ctx->uid || ctx->cm_id != cm_id) {
                /*
                 * We ignore events for new connections until userspace has set
@@ -432,7 +431,7 @@ static ssize_t ucma_get_event(struct ucma_file *file, const char __user *inbuf,
        }
 
        if (ctx) {
-               uevent->ctx->backlog++;
+               atomic_inc(&uevent->ctx->backlog);
                uevent->cm_id->context = ctx;
                ucma_finish_ctx(ctx);
        }
@@ -1136,10 +1135,12 @@ static ssize_t ucma_listen(struct ucma_file *file, const char __user *inbuf,
        if (IS_ERR(ctx))
                return PTR_ERR(ctx);
 
-       ctx->backlog = cmd.backlog > 0 && cmd.backlog < max_backlog ?
-                      cmd.backlog : max_backlog;
+       if (cmd.backlog <= 0 || cmd.backlog > max_backlog)
+               cmd.backlog = max_backlog;
+       atomic_set(&ctx->backlog, cmd.backlog);
+
        mutex_lock(&ctx->mutex);
-       ret = rdma_listen(ctx->cm_id, ctx->backlog);
+       ret = rdma_listen(ctx->cm_id, cmd.backlog);
        mutex_unlock(&ctx->mutex);
        ucma_put_ctx(ctx);
        return ret;