fs, epoll: add procfs fdinfo helper

This allows 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 enabled: 1

[avagin@: fix for unitialized ret variable]

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: James Bottomley <jbottomley@parallels.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Helsley <matt.helsley@gmail.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@onelan.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index fadf5958af4bf6314d36751ebbf210647c1a33ee..38cf166cbedbd2639599ed5eb42906a566a4c071 100644 (file)
--- a/fs/eventpoll.c
+++ b/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:
@@ -813,8 +815,35 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
        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 = 0;
+
+       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 enabled: %d\n",
+                                epi->ffd.fd, epi->event.events,
+                                (long long)epi->event.data,
+                                ep_is_linked(&epi->rdllink));
+               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,