[patch 1/7] procfs: Add ability to plug in auxiliary fdinfo providers

From: Cyrill Gorcunov
Date: Wed Sep 12 2012 - 17:37:42 EST

This patch brings ability to print out auxiliary data associated
with file in procfs interface /proc/pid/fdinfo/fd.

In particular further patches make eventfd, evenpoll, signalfd
and fsnotify to print additional information complete enough
to restore these objects after checkpoint.

To simplify the code we add show_fdinfo callback inside
struct file_operations (as Al and Pavel are proposing).

Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
CC: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CC: Alexey Dobriyan <adobriyan@xxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: James Bottomley <jbottomley@xxxxxxxxxxxxx>
CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
CC: Alexey Dobriyan <adobriyan@xxxxxxxxx>
CC: Matthew Helsley <matt.helsley@xxxxxxxxx>
CC: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
CC: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
fs/proc/fd.c | 2 ++
include/linux/fs.h | 3 +++
2 files changed, 5 insertions(+)

Index: linux-2.6.git/fs/proc/fd.c
--- linux-2.6.git.orig/fs/proc/fd.c
+++ linux-2.6.git/fs/proc/fd.c
@@ -50,6 +50,8 @@ static int seq_show(struct seq_file *m,
if (!ret) {
seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
(long long)file->f_pos, f_flags);
+ if (file->f_op->show_fdinfo)
+ ret = file->f_op->show_fdinfo(m, file);

Index: linux-2.6.git/include/linux/fs.h
--- linux-2.6.git.orig/include/linux/fs.h
+++ linux-2.6.git/include/linux/fs.h
@@ -1774,6 +1774,8 @@ struct block_device_operations;

+struct seq_file;
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
@@ -1802,6 +1804,7 @@ struct file_operations {
int (*setlease)(struct file *, long, struct file_lock **);
long (*fallocate)(struct file *file, int mode, loff_t offset,
loff_t len);
+ int (*show_fdinfo)(struct seq_file *m, struct file *f);

struct inode_operations {

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