RDMA/ucma: Remove closing and the close_wq

Use cancel_work_sync() to ensure that the wq is not running and simply
assign NULL to ctx->cm_id to indicate if the work ran or not. Delete the
close_wq since flush_workqueue() is no longer needed.

Link: https://lore.kernel.org/r/20200818120526.702120-15-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 40539c9625d69c388af0a2f2dfc09afec8543fe8..46d37e470e984996fe63176e36be596c6c3d6aac 100644 (file)
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -80,7 +80,6 @@ struct ucma_file {
        struct list_head        ctx_list;
        struct list_head        event_list;
        wait_queue_head_t       poll_wait;
-       struct workqueue_struct *close_wq;
 };
 
 struct ucma_context {
@@ -96,10 +95,6 @@ struct ucma_context {
        u64                     uid;
 
        struct list_head        list;
-       /* mark that device is in process of destroying the internal HW
-        * resources, protected by the ctx_table lock
-        */
-       int                     closing;
        /* sync between removal event and id destroy, protected by file mut */
        int                     destroying;
        struct work_struct      close_work;
@@ -148,12 +143,9 @@ static struct ucma_context *ucma_get_ctx(struct ucma_file *file, int id)
 
        xa_lock(&ctx_table);
        ctx = _ucma_find_context(id, file);
-       if (!IS_ERR(ctx)) {
-               if (ctx->closing)
-                       ctx = ERR_PTR(-EIO);
-               else if (!refcount_inc_not_zero(&ctx->ref))
+       if (!IS_ERR(ctx))
+               if (!refcount_inc_not_zero(&ctx->ref))
                        ctx = ERR_PTR(-ENXIO);
-       }
        xa_unlock(&ctx_table);
        return ctx;
 }
@@ -193,6 +185,14 @@ static void ucma_close_id(struct work_struct *work)
        wait_for_completion(&ctx->comp);
        /* No new events will be generated after destroying the id. */
        rdma_destroy_id(ctx->cm_id);
+
+       /*
+        * At this point ctx->ref is zero so the only place the ctx can be is in
+        * a uevent or in __destroy_id(). Since the former doesn't touch
+        * ctx->cm_id and the latter sync cancels this, there is no races with
+        * this store.
+        */
+       ctx->cm_id = NULL;
 }
 
 static struct ucma_context *ucma_alloc_ctx(struct ucma_file *file)
@@ -356,12 +356,8 @@ static int ucma_event_handler(struct rdma_cm_id *cm_id,
                wake_up_interruptible(&ctx->file->poll_wait);
        }
 
-       if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL && !ctx->destroying) {
-               xa_lock(&ctx_table);
-               ctx->closing = 1;
-               xa_unlock(&ctx_table);
-               queue_work(ctx->file->close_wq, &ctx->close_work);
-       }
+       if (event->event == RDMA_CM_EVENT_DEVICE_REMOVAL && !ctx->destroying)
+               queue_work(system_unbound_wq, &ctx->close_work);
        return 0;
 }
 
@@ -577,17 +573,10 @@ static int __destroy_id(struct ucma_context *ctx)
                ucma_put_ctx(ctx);
        }
 
-       flush_workqueue(ctx->file->close_wq);
+       cancel_work_sync(&ctx->close_work);
        /* At this point it's guaranteed that there is no inflight closing task */
-       xa_lock(&ctx_table);
-       if (!ctx->closing) {
-               xa_unlock(&ctx_table);
-               ucma_put_ctx(ctx);
-               wait_for_completion(&ctx->comp);
-               rdma_destroy_id(ctx->cm_id);
-       } else {
-               xa_unlock(&ctx_table);
-       }
+       if (ctx->cm_id)
+               ucma_close_id(&ctx->close_work);
        return ucma_free_ctx(ctx);
 }
 
@@ -1788,13 +1777,6 @@ static int ucma_open(struct inode *inode, struct file *filp)
        if (!file)
                return -ENOMEM;
 
-       file->close_wq = alloc_ordered_workqueue("ucma_close_id",
-                                                WQ_MEM_RECLAIM);
-       if (!file->close_wq) {
-               kfree(file);
-               return -ENOMEM;
-       }
-
        INIT_LIST_HEAD(&file->event_list);
        INIT_LIST_HEAD(&file->ctx_list);
        init_waitqueue_head(&file->poll_wait);
@@ -1825,7 +1807,6 @@ static int ucma_close(struct inode *inode, struct file *filp)
                xa_erase(&ctx_table, ctx->id);
                __destroy_id(ctx);
        }
-       destroy_workqueue(file->close_wq);
        kfree(file);
        return 0;
 }