signal/timer/event fds: anonymous inode source

This patch add an anonymous inode source, to be used for files that need
and inode only in order to create a file*. We do not care of having an
inode for each file, and we do not even care of having different names in
the associated dentries (dentry names will be same for classes of file*).
This allow code reuse, and will be used by epoll, signalfd and timerfd
(and whatever else there'll be).

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/init/Kconfig b/init/Kconfig
index 322b1f8..a80bd83 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -475,9 +475,19 @@
 	  support for "fast userspace mutexes".  The resulting kernel may not
 	  run glibc-based applications correctly.
 
+config ANON_INODES
+	bool "Enable anonymous inode source" if EMBEDDED
+	default y
+	help
+	  Anonymous inode source for pseudo-files like epoll, signalfd,
+	  timerfd and eventfd.
+
+	  If unsure, say Y.
+
 config EPOLL
 	bool "Enable eventpoll support" if EMBEDDED
 	default y
+	depends on ANON_INODES
 	help
 	  Disabling this option will cause the kernel to be built without
 	  support for epoll family of system calls.