This allow us to print out eventpoll target file descriptor,
events and data, the /proc/pid/fdinfo/fd consists of

 | pos: 0
 | flags:       02
 | tfd:        5 events:       1d data: ffffffffffffffff

This feature is CONFIG_CHECKPOINT_RESTORE only.

Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org>
CC: Pavel Emelyanov <xe...@parallels.com>
CC: Al Viro <v...@zeniv.linux.org.uk>
CC: Alexey Dobriyan <adobri...@gmail.com>
CC: Andrew Morton <a...@linux-foundation.org>
CC: James Bottomley <jbottom...@parallels.com>
CC: Matthew Helsley <matt.hels...@gmail.com>
---
 fs/eventpoll.c |   28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

Index: linux-2.6.git/fs/eventpoll.c
===================================================================
--- linux-2.6.git.orig/fs/eventpoll.c
+++ linux-2.6.git/fs/eventpoll.c
@@ -38,6 +38,8 @@
 #include <asm/io.h>
 #include <asm/mman.h>
 #include <linux/atomic.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 
 /*
  * LOCKING:
@@ -783,8 +785,34 @@ static unsigned int ep_eventpoll_poll(st
        return pollflags != -1 ? pollflags : 0;
 }
 
+#ifdef CONFIG_PROC_FS
+static int ep_show_fdinfo(struct seq_file *m, struct file *f)
+{
+       struct eventpoll *ep = f->private_data;
+       struct rb_node *rbp;
+       int ret;
+
+       mutex_lock(&ep->mtx);
+       for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+               struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
+
+               ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",
+                                epi->ffd.fd, epi->event.events,
+                                (long long)epi->event.data);
+               if (ret)
+                       break;
+       }
+       mutex_unlock(&ep->mtx);
+
+       return ret;
+}
+#endif
+
 /* File callbacks that implement the eventpoll file behaviour */
 static const struct file_operations eventpoll_fops = {
+#ifdef CONFIG_PROC_FS
+       .show_fdinfo    = ep_show_fdinfo,
+#endif
        .release        = ep_eventpoll_release,
        .poll           = ep_eventpoll_poll,
        .llseek         = noop_llseek,

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