[PATCH] epoll: microoptimisations

From: Davide Libenzi <davidel@xmailserver.org>

- Inline eventpoll_release() so that __fput() does not need to call in
  epoll code if the file itself is not registered inside an epoll fd

- Add <linux/types.h> inclusion due __u32 and __u64 usage

- Fix debug printf that would otherwise panic if enabled with the new
  epoll code

fs/eventpoll.c

@@ -443,28 +443,16 @@ void eventpoll_init_file(struct file *file)
 
 
 /*
- * This is called from inside fs/file_table.c:__fput() to unlink files
- * from the eventpoll interface. We need to have this facility to cleanup
- * correctly files that are closed without being removed from the eventpoll
- * interface.
+ * This is called from eventpoll_release() to unlink files from the eventpoll
+ * interface. We need to have this facility to cleanup correctly files that are
+ * closed without being removed from the eventpoll interface.
  */
-void eventpoll_release(struct file *file)
+void eventpoll_release_file(struct file *file)
 {
 	struct list_head *lsthead = &file->f_ep_links;
 	struct eventpoll *ep;
 	struct epitem *epi;
 
-	/*
-	 * Fast check to avoid the get/release of the semaphore. Since
-	 * we're doing this outside the semaphore lock, it might return
-	 * false negatives, but we don't care. It'll help in 99.99% of cases
-	 * to avoid the semaphore lock. False positives simply cannot happen
-	 * because the file in on the way to be removed and nobody ( but
-	 * eventpoll ) has still a reference to this file.
-	 */
-	if (list_empty(lsthead))
-		return;
-
 	/*
 	 * We don't want to get "file->f_ep_lock" because it is not
 	 * necessary. It is not necessary because we're in the "struct file"
@@ -541,7 +529,7 @@ asmlinkage long sys_epoll_create(int size)
 /*
  * The following function implement the controller interface for the eventpoll
  * file that enable the insertion/removal/change of file descriptors inside
- * the interest set. It rapresents the kernel part of the user spcae epoll_ctl(2).
+ * the interest set. It rapresents the kernel part of the user space epoll_ctl(2).
  */
 asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event *event)
 {
@@ -551,8 +539,8 @@ asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event *even
 	struct epitem *epi;
 	struct epoll_event epds;
 
-	DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %u)\n",
-		     current, epfd, op, fd, event->events));
+	DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p)\n",
+		     current, epfd, op, fd, event));
 
 	error = -EFAULT;
 	if (copy_from_user(&epds, event, sizeof(struct epoll_event)))
@@ -633,8 +621,8 @@ asmlinkage long sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event *even
 eexit_2:
 	fput(file);
 eexit_1:
-	DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %u) = %d\n",
-		     current, epfd, op, fd, event->events, error));
+	DNPRINTK(3, (KERN_INFO "[%p] eventpoll: sys_epoll_ctl(%d, %d, %d, %p) = %d\n",
+		     current, epfd, op, fd, event, error));
 
 	return error;
 }

include/linux/eventpoll.h

@@ -14,6 +14,8 @@
 #ifndef _LINUX_EVENTPOLL_H
 #define _LINUX_EVENTPOLL_H
 
+#include <linux/types.h>
+
 
 /* Valid opcodes to issue to sys_epoll_ctl() */
 #define EPOLL_CTL_ADD 1
@@ -55,8 +57,37 @@ asmlinkage long sys_epoll_wait(int epfd, struct epoll_event *events, int maxeven
 /* Used to initialize the epoll bits inside the "struct file" */
 void eventpoll_init_file(struct file *file);
 
-/* Used in fs/file_table.c:__fput() to unlink files from the eventpoll interface */
-void eventpoll_release(struct file *file);
+/* Used to release the epoll bits inside the "struct file" */
+void eventpoll_release_file(struct file *file);
+
+/*
+ * This is called from inside fs/file_table.c:__fput() to unlink files
+ * from the eventpoll interface. We need to have this facility to cleanup
+ * correctly files that are closed without being removed from the eventpoll
+ * interface.
+ */
+static inline void eventpoll_release(struct file *file)
+{
+
+	/*
+	 * Fast check to avoid the get/release of the semaphore. Since
+	 * we're doing this outside the semaphore lock, it might return
+	 * false negatives, but we don't care. It'll help in 99.99% of cases
+	 * to avoid the semaphore lock. False positives simply cannot happen
+	 * because the file in on the way to be removed and nobody ( but
+	 * eventpoll ) has still a reference to this file.
+	 */
+	if (likely(list_empty(&file->f_ep_links)))
+		return;
+
+	/*
+	 * The file is being closed while it is still linked to an epoll
+	 * descriptor. We need to handle this by correctly unlinking it
+	 * from its containers.
+	 */
+	eventpoll_release_file(file);
+}
+
 
 #else