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Subject[patch 2/8] procfs: Convert /proc/pid/fdinfo/ handling routines to seq-file
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).

Also, to eliminate code duplication (and Pavel's concerns) the fdinfo_open_helper
function introduced which is used in both seq_fdinfo_open and proc_fd_link.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: 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 | 123 +++++++++++++++++++++++++++++++++++------------------------
1 file changed, 75 insertions(+), 48 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 +6,104 @@
#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 {
+ loff_t f_pos;
+ int f_flags;
+};

-static int proc_fd_info(struct inode *inode, struct path *path, char *info)
+static int fdinfo_open_helper(struct inode *inode, int *f_flags, struct path *path)
{
- struct task_struct *task = get_proc_task(inode);
struct files_struct *files = NULL;
- int fd = proc_fd(inode);
- struct file *file;
+ struct task_struct *task;
+ int 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.
- */
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (file) {
- unsigned int f_flags;
- struct fdtable *fdt;
-
- fdt = files_fdtable(files);
- f_flags = file->f_flags & ~O_CLOEXEC;
- if (close_on_exec(fd, fdt))
- f_flags |= O_CLOEXEC;
+ int fd = proc_fd(inode);
+ struct file *fd_file;

+ spin_lock(&files->file_lock);
+ fd_file = fcheck_files(files, fd);
+ if (fd_file) {
+ if (f_flags) {
+ struct fdtable *fdt = files_fdtable(files);
+
+ *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);
+ *path = fd_file->f_path;
+ path_get(&fd_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;
+ ret = 0;
}
spin_unlock(&files->file_lock);
put_files_struct(files);
}
- return -ENOENT;
+
+ return ret;
}

+static int seq_show(struct seq_file *m, void *v)
+{
+ struct proc_fdinfo *fdinfo = m->private;
+ seq_printf(m, "pos:\t%lli\nflags:\t0%o\n",
+ (long long)fdinfo->f_pos,
+ fdinfo->f_flags);
+ return 0;
+}
+
+static int seq_fdinfo_open(struct inode *inode, struct file *file)
+{
+ struct proc_fdinfo *fdinfo = NULL;
+ int ret = -ENOENT;
+
+ fdinfo = kzalloc(sizeof(*fdinfo), GFP_KERNEL);
+ if (!fdinfo)
+ return -ENOMEM;
+
+ ret = fdinfo_open_helper(inode, &fdinfo->f_flags, NULL);
+ if (!ret) {
+ ret = single_open(file, seq_show, fdinfo);
+ if (!ret)
+ fdinfo = NULL;
+ }
+
+ kfree(fdinfo);
+ 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;
+
+ kfree(fdinfo);
+
+ 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 +173,7 @@ 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);
+ return fdinfo_open_helper(dentry->d_inode, NULL, path);
}

static struct dentry *
@@ -245,22 +288,6 @@ 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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