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Message-ID: <20120814195649.GB31043@moon>
Date: Tue, 14 Aug 2012 23:56:49 +0400
From: Cyrill Gorcunov <gorcunov@...nvz.org>
To: Al Viro <viro@...IV.linux.org.uk>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Pavel Emelyanov <xemul@...allels.com>,
James Bottomley <jbottomley@...allels.com>,
Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 3/8] procfs: Add ability to plug in auxiliary fdinfo
providers
On Tue, Aug 14, 2012 at 10:35:58PM +0400, Cyrill Gorcunov wrote:
> On Tue, Aug 14, 2012 at 07:31:42PM +0100, Al Viro wrote:
> > > Initially we considered to inject some "show" metod to
> > > file_operations but since there really a number of
> > > file_operations declared inside kernel (and in real the
> > > further patches cover onle eventfd/epoll/inotify) the
> > > waste of memory space will be inacceptable I think.
> >
> > NAK. This is too ugly to live. Put it into file_operations,
> > with NULL meaning default output, or don't do it at all.
> >
> > And no, "it's only if you enable CONFIG_SOME_SHIT" gambit won't
> > fly - we have all seen it played too many times. All it takes
> > is one politically-inclined induhvidual adding a dependency to
> > some "vertically integrated" turd (*cough* systemd *spit* udev
> > *cough*) and we are stuck with the damn thing. CGROUP shite
> > is already there, DEVTMPFS is well on its way, etc.
>
> OK, I'll put it into file_operations then (actually Pavel was
> proposing the same but I've been scared by amount of file_operations
> declared). Thanks!
Al, does the patch below looks better? If so I'll fix up the rest.
---
fs/proc/fd.c | 109 ++++++++++++++++++++++++++++++++++++++----------
include/linux/fs.h | 3 +
include/linux/proc_fs.h | 8 +++
3 files changed, 99 insertions(+), 21 deletions(-)
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
@@ -8,18 +8,14 @@
#include <linux/security.h>
#include <linux/file.h>
#include <linux/seq_file.h>
+#include <linux/spinlock.h>
#include <linux/proc_fs.h>
#include "internal.h"
#include "fd.h"
-struct proc_fdinfo {
- loff_t f_pos;
- int f_flags;
-};
-
-static int fdinfo_open_helper(struct inode *inode, int *f_flags, struct path *path)
+static int fdinfo_open_helper(struct inode *inode, int *f_flags, struct file **f_file, struct path *path)
{
struct files_struct *files = NULL;
struct task_struct *task;
@@ -49,6 +45,10 @@ static int fdinfo_open_helper(struct ino
*path = fd_file->f_path;
path_get(&fd_file->f_path);
}
+ if (f_file) {
+ *f_file = fd_file;
+ get_file(fd_file);
+ }
ret = 0;
}
spin_unlock(&files->file_lock);
@@ -58,43 +58,110 @@ static int fdinfo_open_helper(struct ino
return ret;
}
+static void *seq_start(struct seq_file *m, loff_t *pos)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+
+ extra->pos = *pos;
+
+ return *pos == 0 ? extra :
+ (extra->fdinfo_ops ?
+ extra->fdinfo_ops->start(m, pos) : NULL);
+}
+
+static void seq_stop(struct seq_file *m, void *v)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+
+ if (extra->fdinfo_ops && extra->pos > 0)
+ extra->fdinfo_ops->stop(m, v);
+}
+
+static void *seq_next(struct seq_file *m, void *p, loff_t *pos)
+{
+ struct proc_fdinfo_extra *extra = m->private;
+ void *v = NULL;
+
+ if (extra->fdinfo_ops) {
+ int ret = 0;
+
+ if (*pos == 0) {
+ v = extra->fdinfo_ops->start(m, pos);
+ if (v) {
+ ret = extra->fdinfo_ops->show(m, v);
+ p = v;
+ } else
+ ret = -1;
+ }
+
+ if (!ret)
+ v = extra->fdinfo_ops->next(m, p, pos);
+ } else
+ ++*pos;
+
+ extra->pos = *pos;
+ return v;
+}
+
static int seq_show(struct seq_file *m, void *v)
{
- struct proc_fdinfo *fdinfo = m->private;
+ struct proc_fdinfo_extra *extra = m->private;
+
+ if (extra->fdinfo_ops && extra->pos > 0)
+ return extra->fdinfo_ops->show(m, v);
+
seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
- (long long)fdinfo->f_pos,
- fdinfo->f_flags);
+ (long long)extra->f_file->f_pos,
+ extra->f_flags);
return 0;
}
+static const struct seq_operations fdinfo_seq_ops = {
+ .start = seq_start,
+ .next = seq_next,
+ .stop = seq_stop,
+ .show = seq_show,
+};
+
static int seq_fdinfo_open(struct inode *inode, struct file *file)
{
- struct proc_fdinfo *fdinfo = NULL;
- int ret = -ENOENT;
+ struct proc_fdinfo_extra *extra;
+ struct seq_file *m;
+ int ret;
- fdinfo = kzalloc(sizeof(*fdinfo), GFP_KERNEL);
- if (!fdinfo)
+ extra = kzalloc(sizeof(*extra), GFP_KERNEL);
+ if (!extra)
return -ENOMEM;
- ret = fdinfo_open_helper(inode, &fdinfo->f_flags, NULL);
+ ret = seq_open(file, &fdinfo_seq_ops);
if (!ret) {
- ret = single_open(file, seq_show, fdinfo);
+ ret = -ENOENT;
+ m = file->private_data;
+ m->private = extra;
+
+ ret = fdinfo_open_helper(inode, &extra->f_flags,
+ &extra->f_file, NULL);
if (!ret)
- fdinfo = NULL;
+ extra->fdinfo_ops = extra->f_file->f_op->fdinfo_ops;
}
- kfree(fdinfo);
+ if (ret) {
+ if (extra->f_file)
+ put_filp(extra->f_file);
+ kfree(extra);
+ }
return ret;
}
static int seq_fdinfo_release(struct inode *inode, struct file *file)
{
struct seq_file *m = file->private_data;
- struct proc_fdinfo *fdinfo = m->private;
+ struct proc_fdinfo_extra *extra = m->private;
- kfree(fdinfo);
+ put_filp(extra->f_file);
+ kfree(m->private);
- return single_release(inode, file);
+ return seq_release(inode, file);
}
static const struct file_operations proc_fdinfo_file_operations = {
@@ -173,7 +240,7 @@ static const struct dentry_operations ti
static int proc_fd_link(struct dentry *dentry, struct path *path)
{
- return fdinfo_open_helper(dentry->d_inode, NULL, path);
+ return fdinfo_open_helper(dentry->d_inode, NULL, NULL, path);
}
static struct dentry *
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
@@ -1775,8 +1775,11 @@ struct block_device_operations;
#define HAVE_COMPAT_IOCTL 1
#define HAVE_UNLOCKED_IOCTL 1
+struct seq_operations;
+
struct file_operations {
struct module *owner;
+ struct seq_operations *fdinfo_ops;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
Index: linux-2.6.git/include/linux/proc_fs.h
===================================================================
--- linux-2.6.git.orig/include/linux/proc_fs.h
+++ linux-2.6.git/include/linux/proc_fs.h
@@ -100,6 +100,14 @@ struct vmcore {
loff_t offset;
};
+/* auxiliary data allocated per fdinfo reader */
+struct proc_fdinfo_extra {
+ loff_t pos;
+ struct file *f_file;
+ struct seq_operations *fdinfo_ops;
+ unsigned int f_flags;
+};
+
#ifdef CONFIG_PROC_FS
extern void proc_root_init(void);
--
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