RDMA/core: Remove ucontext_lock from the uverbs_destry_ufile_hw() path

This lock only serializes ucontext creation. Instead of checking the
ucontext_lock during destruction hold the existing hw_destroy_rwsem during
creation, which is the standard pattern for object creation.

The simplification of locking is needed for the next patch.

Link: https://lore.kernel.org/r/1578506740-22188-4-git-send-email-yishaih@mellanox.comSigned-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/rdma_core.c

@@ -845,9 +845,7 @@ static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,
 }
 
 /*
- * Destroy the uncontext and every uobject associated with it. If called with
- * reason != RDMA_REMOVE_CLOSE this will not return until the destruction has
- * been completed and ufile->ucontext is NULL.
+ * Destroy the uncontext and every uobject associated with it.
  *
  * This is internally locked and can be called in parallel from multiple
  * contexts.
@@ -855,22 +853,6 @@ static int __uverbs_cleanup_ufile(struct ib_uverbs_file *ufile,
 void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,
 			     enum rdma_remove_reason reason)
 {
-	if (reason == RDMA_REMOVE_CLOSE) {
-		/*
-		 * During destruction we might trigger something that
-		 * synchronously calls release on any file descriptor. For
-		 * this reason all paths that come from file_operations
-		 * release must use try_lock. They can progress knowing that
-		 * there is an ongoing uverbs_destroy_ufile_hw that will clean
-		 * up the driver resources.
-		 */
-		if (!mutex_trylock(&ufile->ucontext_lock))
-			return;
-
-	} else {
-		mutex_lock(&ufile->ucontext_lock);
-	}
-
 	down_write(&ufile->hw_destroy_rwsem);
 
 	/*
@@ -899,7 +881,6 @@ void uverbs_destroy_ufile_hw(struct ib_uverbs_file *ufile,
 
 done:
 	up_write(&ufile->hw_destroy_rwsem);
-	mutex_unlock(&ufile->ucontext_lock);
 }
 
 const struct uverbs_obj_type_class uverbs_fd_class = {

drivers/infiniband/core/uverbs_cmd.c

@@ -218,6 +218,8 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)
 	if (ret)
 		return ret;
 
+	if (!down_read_trylock(&file->hw_destroy_rwsem))
+		return -EIO;
 	mutex_lock(&file->ucontext_lock);
 	ib_dev = srcu_dereference(file->device->ib_dev,
 				  &file->device->disassociate_srcu);
@@ -284,7 +286,7 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)
 	smp_store_release(&file->ucontext, ucontext);
 
 	mutex_unlock(&file->ucontext_lock);
-
+	up_read(&file->hw_destroy_rwsem);
 	return 0;
 
 err_uobj:
@@ -298,6 +300,7 @@ static int ib_uverbs_get_context(struct uverbs_attr_bundle *attrs)
 
 err:
 	mutex_unlock(&file->ucontext_lock);
+	up_read(&file->hw_destroy_rwsem);
 	return ret;
 }