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SubjectRe: [patch 3/8] procfs: Add ability to plug in auxiliary fdinfo providers
On Wed, Aug 15, 2012 at 10:29:27PM +0100, Al Viro wrote:
> This, BTW, is too convoluted for its own good. What you need is
> something like
> struct whatever {
> struct seq_file *m;
> struct file *f;
> int flags;
> };
> with single allocation of that sucker in your ->open(). Set
> file->private_data to address of seq_file field in your object *before*
> calling seq_open() and don't bother with m->private at all - just use
> container_of(m, struct whatever, m) in your ->show() to get to that
> structure...

Al, does the version below looks better? (Since it's harder to review diff,
here is the code after the patch applied).
---
struct proc_fdinfo {
struct seq_file m;
struct file *fd_file;
int f_flags;
};

static int seq_show(struct seq_file *m, void *v)
{
struct proc_fdinfo *fdinfo = container_of(m, struct proc_fdinfo, m);
seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
(long long)fdinfo->fd_file->f_pos, fdinfo->f_flags);
return 0;
}

static int seq_fdinfo_open(struct inode *inode, struct file *file)
{
struct proc_fdinfo *fdinfo = NULL;
struct files_struct *files = NULL;
struct task_struct *task;
struct file *fd_file;
int f_flags, ret;

ret = -ENOENT;

task = get_proc_task(inode);
if (task) {
files = get_files_struct(task);
put_task_struct(task);
}

if (files) {
int fd = proc_fd(inode);

spin_lock(&files->file_lock);
fd_file = fcheck_files(files, fd);
if (fd_file) {
struct fdtable *fdt = files_fdtable(files);

f_flags = fd_file->f_flags & ~O_CLOEXEC;
if (close_on_exec(fd, fdt))
f_flags |= O_CLOEXEC;

get_file(fd_file);
ret = 0;
}
spin_unlock(&files->file_lock);

put_files_struct(files);
}

if (ret)
return ret;

ret = -ENOMEM;
fdinfo = kmalloc(sizeof(*fdinfo), GFP_KERNEL);
if (!fdinfo)
goto err_put;

fdinfo->fd_file = fd_file;
fdinfo->f_flags = f_flags;
file->private_data = &fdinfo->m;

ret = single_open(file, seq_show, NULL);
if (ret)
goto err_free;

return 0;

err_free:
kfree(fdinfo);
err_put:
fput(fd_file);
return ret;
}

static int seq_fdinfo_release(struct inode *inode, struct file *file)
{
struct proc_fdinfo *fdinfo =
container_of((struct seq_file *)file->private_data,
struct proc_fdinfo, m);
fput(fdinfo->fd_file);
return single_release(inode, file);
}

static const struct file_operations proc_fdinfo_file_operations = {
.open = seq_fdinfo_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_fdinfo_release,
};
---
From: Cyrill Gorcunov <gorcunov@openvz.org>
Subject: procfs: Convert /proc/pid/fdinfo/ handling routines to seq-file v2

This patch converts /proc/pid/fdinfo/ handling routines to seq-file which
is needed to extend seq operations and plug in auxiliary fdinfo provides
from subsystems like eventfd/eventpoll/fsnotify.

Note the proc_fd_link no longer call for proc_fd_info, simply because
proc_fd_info is converted to seq_fdinfo_open (which is seq-file open()
prototype).

v2 (by Al Viro):
- Don't use helper function with optional arguments, thus proc_fd_info get deprecated
- Use proc_fdinfo structure with seq_file embedded, thus we can use container_of helper
- Use fput to free reference to the file we've grabbed

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Pavel Emelyanov <xemul@parallels.com>
CC: Al Viro <viro@ZenIV.linux.org.uk>
CC: Alexey Dobriyan <adobriyan@gmail.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: James Bottomley <jbottomley@parallels.com>
---
fs/proc/fd.c | 145 ++++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 99 insertions(+), 46 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
@@ -6,61 +6,105 @@
#include <linux/namei.h>
#include <linux/pid.h>
#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/seq_file.h>

#include <linux/proc_fs.h>

#include "internal.h"
#include "fd.h"

-#define PROC_FDINFO_MAX 64
+struct proc_fdinfo {
+ struct seq_file m;
+ struct file *fd_file;
+ int f_flags;
+};
+
+static int seq_show(struct seq_file *m, void *v)
+{
+ struct proc_fdinfo *fdinfo = container_of(m, struct proc_fdinfo, m);
+ seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
+ (long long)fdinfo->fd_file->f_pos, fdinfo->f_flags);
+ return 0;
+}

-static int proc_fd_info(struct inode *inode, struct path *path, char *info)
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
{
- struct task_struct *task = get_proc_task(inode);
+ struct proc_fdinfo *fdinfo = NULL;
struct files_struct *files = NULL;
- int fd = proc_fd(inode);
- struct file *file;
+ struct task_struct *task;
+ struct file *fd_file;
+ int f_flags, ret;

+ ret = -ENOENT;
+
+ task = get_proc_task(inode);
if (task) {
files = get_files_struct(task);
put_task_struct(task);
}
+
if (files) {
- /*
- * We are not taking a ref to the file structure, so we must
- * hold ->file_lock.
- */
+ int fd = proc_fd(inode);
+
spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (file) {
- unsigned int f_flags;
- struct fdtable *fdt;
+ fd_file = fcheck_files(files, fd);
+ if (fd_file) {
+ struct fdtable *fdt = files_fdtable(files);

- fdt = files_fdtable(files);
- f_flags = file->f_flags & ~O_CLOEXEC;
+ f_flags = fd_file->f_flags & ~O_CLOEXEC;
if (close_on_exec(fd, fdt))
f_flags |= O_CLOEXEC;

- if (path) {
- *path = file->f_path;
- path_get(&file->f_path);
- }
- if (info)
- snprintf(info, PROC_FDINFO_MAX,
- "pos:\t%lli\n"
- "flags:\t0%o\n",
- (long long) file->f_pos,
- f_flags);
- spin_unlock(&files->file_lock);
- put_files_struct(files);
- return 0;
+ get_file(fd_file);
+ ret = 0;
}
spin_unlock(&files->file_lock);
+
put_files_struct(files);
}
- return -ENOENT;
+
+ if (ret)
+ return ret;
+
+ ret = -ENOMEM;
+ fdinfo = kmalloc(sizeof(*fdinfo), GFP_KERNEL);
+ if (!fdinfo)
+ goto err_put;
+
+ fdinfo->fd_file = fd_file;
+ fdinfo->f_flags = f_flags;
+ file->private_data = &fdinfo->m;
+
+ ret = single_open(file, seq_show, NULL);
+ if (ret)
+ goto err_free;
+
+ return 0;
+
+err_free:
+ kfree(fdinfo);
+err_put:
+ fput(fd_file);
+ return ret;
}

+static int seq_fdinfo_release(struct inode *inode, struct file *file)
+{
+ struct proc_fdinfo *fdinfo =
+ container_of((struct seq_file *)file->private_data,
+ struct proc_fdinfo, m);
+ fput(fdinfo->fd_file);
+ return single_release(inode, file);
+}
+
+static const struct file_operations proc_fdinfo_file_operations = {
+ .open = seq_fdinfo_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_fdinfo_release,
+};
+
static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
{
struct files_struct *files;
@@ -130,7 +174,32 @@ static const struct dentry_operations ti

static int proc_fd_link(struct dentry *dentry, struct path *path)
{
- return proc_fd_info(dentry->d_inode, path, NULL);
+ struct files_struct *files = NULL;
+ struct task_struct *task;
+ int ret = -ENOENT;
+
+ task = get_proc_task(dentry->d_inode);
+ if (task) {
+ files = get_files_struct(task);
+ put_task_struct(task);
+ }
+
+ if (files) {
+ int fd = proc_fd(dentry->d_inode);
+ struct file *fd_file;
+
+ spin_lock(&files->file_lock);
+ fd_file = fcheck_files(files, fd);
+ if (fd_file) {
+ *path = fd_file->f_path;
+ path_get(&fd_file->f_path);
+ ret = 0;
+ }
+ spin_unlock(&files->file_lock);
+ put_files_struct(files);
+ }
+
+ return ret;
}

static struct dentry *
@@ -245,22 +314,6 @@ out_no_task:
return retval;
}

-static ssize_t proc_fdinfo_read(struct file *file, char __user *buf,
- size_t len, loff_t *ppos)
-{
- char tmp[PROC_FDINFO_MAX];
- int err = proc_fd_info(file->f_path.dentry->d_inode, NULL, tmp);
- if (!err)
- err = simple_read_from_buffer(buf, len, ppos, tmp, strlen(tmp));
- return err;
-}
-
-static const struct file_operations proc_fdinfo_file_operations = {
- .open = nonseekable_open,
- .read = proc_fdinfo_read,
- .llseek = no_llseek,
-};
-
static int proc_readfd(struct file *filp, void *dirent, filldir_t filldir)
{
return proc_readfd_common(filp, dirent, filldir, proc_fd_instantiate);

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