vfs/epoll: add epoll_create1(2) implement

Linux Programmer's Manual

NAME
       epoll_create, epoll_create1 - open an epoll file descriptor

...
SYNOPSIS
       #include <sys/epoll.h>

       int epoll_create1(int flags);
...

   epoll_create1()
       If flags is 0, then, other than the fact that the obsolete
       size argument is dropped, epoll_create1() is the same as
       epoll_create(). The following value can be included in flags
       to obtain different behavior:

       EPOLL_CLOEXEC
              Set the close-on-exec (FD_CLOEXEC) flag on the new file
              descriptor. See the description of the O_CLOEXEC flag in
              open(2) for reasons why this may be useful.

https://man7.org/linux/man-pages/man7/epoll.7.html

fs/Kconfig

@@ -30,6 +30,12 @@ config FS_AUTOMOUNTER_DEBUG
 		system debug is not enable.  This is useful primarily for in vivo
 		unit testing of the auto-mount feature.
 
+config FS_NEPOLL_DESCRIPTORS
+	int "Maximum number of default epoll descriptors for epoll_create1(2)"
+	default 8
+	---help---
+		The maximum number of default epoll descriptors for epoll_create1(2)
+
 config DISABLE_PSEUDOFS_OPERATIONS
 	bool "Disable pseudo-filesystem operations"
 	default y if DEFAULT_SMALL

fs/vfs/fs_epoll.c

@@ -80,6 +80,31 @@ int epoll_create(int size)
   return (int)((intptr_t)eph);
 }
 
+/****************************************************************************
+ * Name: epoll_create1
+ *
+ * Description:
+ *
+ * Input Parameters:
+ *
+ * Returned Value:
+ *
+ ****************************************************************************/
+
+int epoll_create1(int flags)
+{
+  /* For current implementation, Close-on-exec is a default behavior,
+   * the handle of epoll(2) is not a real file handle.
+   */
+
+  if (flags != EPOLL_CLOEXEC)
+    {
+      return EINVAL;
+    }
+
+  return epoll_create(CONFIG_FS_NEPOLL_DESCRIPTORS);
+}
+
 /****************************************************************************
  * Name: epoll_close
  *

include/sys/epoll.h

@@ -76,6 +76,14 @@ enum EPOLL_EVENTS
 #define EPOLLHUP EPOLLHUP
   };
 
+/* Flags to be passed to epoll_create1.  */
+
+enum
+{
+    EPOLL_CLOEXEC = 02000000
+#define EPOLL_CLOEXEC EPOLL_CLOEXEC
+};
+
 typedef union poll_data
 {
   void        *ptr;
@@ -108,8 +116,10 @@ struct epoll_head
  ****************************************************************************/
 
 int epoll_create(int size);
+int epoll_create1(int flags);
 int epoll_ctl(int epfd, int op, int fd, struct epoll_event *ev);
-int epoll_wait(int epfd, struct epoll_event *evs, int maxevents, int timeout);
+int epoll_wait(int epfd, struct epoll_event *evs,
+               int maxevents, int timeout);
 
 void epoll_close(int epfd);