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

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 12 Nov 2012 14:14:41 +0400
Cyrill Gorcunov <gorcunov@openvz.org> wrote:

> 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).
>
> ...
>
> --- linux-2.6.git.orig/include/linux/fs.h
> +++ linux-2.6.git/include/linux/fs.h
> @@ -1517,6 +1517,8 @@ struct block_device_operations;
>  #define HAVE_COMPAT_IOCTL 1
>  #define HAVE_UNLOCKED_IOCTL 1
>  
> +struct seq_file;
> +

We already have a forward declaration of seq_file in fs.h.  At line
1583(!).

This is why forward declarations should always be placed at the start
of the file, please.

--- a/include/linux/fs.h~procfs-add-ability-to-plug-in-auxiliary-fdinfo-providers-fix
+++ a/include/linux/fs.h
@@ -44,6 +44,7 @@ struct vm_area_struct;
 struct vfsmount;
 struct cred;
 struct swap_info_struct;
+struct seq_file;
 
 extern void __init inode_init(void);
 extern void __init inode_init_early(void);
@@ -1517,8 +1518,6 @@ struct block_device_operations;
 #define HAVE_COMPAT_IOCTL 1
 #define HAVE_UNLOCKED_IOCTL 1
 
-struct seq_file;
-
 struct file_operations {
 	struct module *owner;
 	loff_t (*llseek) (struct file *, loff_t, int);
@@ -1583,8 +1582,6 @@ struct inode_operations {
 			   umode_t create_mode, int *opened);
 } ____cacheline_aligned;
 
-struct seq_file;
-
 ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
 			      unsigned long nr_segs, unsigned long fast_segs,
 			      struct iovec *fast_pointer,
_