Kill indirect include of file.h from eventfd.h, use fdget() in cgroup.c

kernel/cgroup.c is the only place in the tree that relies on eventfd.h
pulling file.h; move that include there.  Switch from eventfd_fget()/fput()
to fdget()/fdput(), while we are at it - eventfd_ctx_fileget() will fail
on non-eventfd descriptors just fine, no need to do that check twice...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/eventfd.h

@@ -9,7 +9,6 @@
 #define _LINUX_EVENTFD_H
 
 #include <linux/fcntl.h>
-#include <linux/file.h>
 #include <linux/wait.h>
 
 /*
@@ -26,6 +25,8 @@
 #define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
 #define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
 
+struct file;
+
 #ifdef CONFIG_EVENTFD
 
 struct file *eventfd_file_create(unsigned int count, int flags);

kernel/cgroup.c

@@ -60,6 +60,7 @@
 #include <linux/poll.h>
 #include <linux/flex_array.h> /* used in cgroup_attach_task */
 #include <linux/kthread.h>
+#include <linux/file.h>
 
 #include <linux/atomic.h>
 
@@ -4034,8 +4035,8 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
 	struct cgroup_event *event;
 	struct cgroup_subsys_state *cfile_css;
 	unsigned int efd, cfd;
-	struct file *efile;
-	struct file *cfile;
+	struct fd efile;
+	struct fd cfile;
 	char *endp;
 	int ret;
 
@@ -4058,31 +4059,31 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
 	init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
 	INIT_WORK(&event->remove, cgroup_event_remove);
 
-	efile = eventfd_fget(efd);
-	if (IS_ERR(efile)) {
-		ret = PTR_ERR(efile);
+	efile = fdget(efd);
+	if (!efile.file) {
+		ret = -EBADF;
 		goto out_kfree;
 	}
 
-	event->eventfd = eventfd_ctx_fileget(efile);
+	event->eventfd = eventfd_ctx_fileget(efile.file);
 	if (IS_ERR(event->eventfd)) {
 		ret = PTR_ERR(event->eventfd);
 		goto out_put_efile;
 	}
 
-	cfile = fget(cfd);
-	if (!cfile) {
+	cfile = fdget(cfd);
+	if (!cfile.file) {
 		ret = -EBADF;
 		goto out_put_eventfd;
 	}
 
 	/* the process need read permission on control file */
 	/* AV: shouldn't we check that it's been opened for read instead? */
-	ret = inode_permission(file_inode(cfile), MAY_READ);
+	ret = inode_permission(file_inode(cfile.file), MAY_READ);
 	if (ret < 0)
 		goto out_put_cfile;
 
-	event->cft = __file_cft(cfile);
+	event->cft = __file_cft(cfile.file);
 	if (IS_ERR(event->cft)) {
 		ret = PTR_ERR(event->cft);
 		goto out_put_cfile;
@@ -4103,7 +4104,7 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
 
 	ret = -EINVAL;
 	event->css = cgroup_css(cgrp, event->cft->ss);
-	cfile_css = css_from_dir(cfile->f_dentry->d_parent, event->cft->ss);
+	cfile_css = css_from_dir(cfile.file->f_dentry->d_parent, event->cft->ss);
 	if (event->css && event->css == cfile_css && css_tryget(event->css))
 		ret = 0;
 
@@ -4121,25 +4122,25 @@ static int cgroup_write_event_control(struct cgroup_subsys_state *dummy_css,
 	if (ret)
 		goto out_put_css;
 
-	efile->f_op->poll(efile, &event->pt);
+	efile.file->f_op->poll(efile.file, &event->pt);
 
 	spin_lock(&cgrp->event_list_lock);
 	list_add(&event->list, &cgrp->event_list);
 	spin_unlock(&cgrp->event_list_lock);
 
-	fput(cfile);
-	fput(efile);
+	fdput(cfile);
+	fdput(efile);
 
 	return 0;
 
 out_put_css:
 	css_put(event->css);
 out_put_cfile:
-	fput(cfile);
+	fdput(cfile);
 out_put_eventfd:
 	eventfd_ctx_put(event->eventfd);
 out_put_efile:
-	fput(efile);
+	fdput(efile);
 out_kfree:
 	kfree(event);