IB/uverbs: Don't store struct file * for event files

The file member of struct ib_uverbs_event_file was only used to keep
track of whether the file had been closed or not.  The only thing we
ever did with the value was check if it was NULL or not.  Simplify the
code and get rid of the need to keep track of the struct file * we
allocate by replacing the file member with an is_closed member.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/uverbs.h

@@ -81,13 +81,13 @@ struct ib_uverbs_device {
 
 struct ib_uverbs_event_file {
 	struct kref				ref;
-	struct file			       *file;
 	struct ib_uverbs_file		       *uverbs_file;
 	spinlock_t				lock;
-	int					is_async;
 	wait_queue_head_t			poll_wait;
 	struct fasync_struct		       *async_queue;
 	struct list_head			event_list;
+	int					is_async;
+	int					is_closed;
 };
 
 struct ib_uverbs_file {

drivers/infiniband/core/uverbs_main.c

@@ -352,7 +352,7 @@ static int ib_uverbs_event_close(struct inode *inode, struct file *filp)
 	struct ib_uverbs_event *entry, *tmp;
 
 	spin_lock_irq(&file->lock);
-	file->file = NULL;
+	file->is_closed = 1;
 	list_for_each_entry_safe(entry, tmp, &file->event_list, list) {
 		if (entry->counter)
 			list_del(&entry->obj_list);
@@ -390,7 +390,7 @@ void ib_uverbs_comp_handler(struct ib_cq *cq, void *cq_context)
 		return;
 
 	spin_lock_irqsave(&file->lock, flags);
-	if (!file->file) {
+	if (file->is_closed) {
 		spin_unlock_irqrestore(&file->lock, flags);
 		return;
 	}
@@ -423,7 +423,7 @@ static void ib_uverbs_async_handler(struct ib_uverbs_file *file,
 	unsigned long flags;
 
 	spin_lock_irqsave(&file->async_file->lock, flags);
-	if (!file->async_file->file) {
+	if (!file->async_file->is_closed) {
 		spin_unlock_irqrestore(&file->async_file->lock, flags);
 		return;
 	}
@@ -509,6 +509,7 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 	ev_file->uverbs_file = uverbs_file;
 	ev_file->async_queue = NULL;
 	ev_file->is_async    = is_async;
+	ev_file->is_closed   = 0;
 
 	*fd = get_unused_fd();
 	if (*fd < 0) {
@@ -522,8 +523,6 @@ struct file *ib_uverbs_alloc_event_file(struct ib_uverbs_file *uverbs_file,
 		goto err_fd;
 	}
 
-	ev_file->file      = filp;
-
 	/*
 	 * fops_get() can't fail here, because we're coming from a
 	 * system call on a uverbs file, which will already have a