Re: 2.6.24-rc3: find complains about /proc/net

[Pavel Emelyanov <xemul@openvz.org>]

Eric W. Biederman wrote:
> Below is a preliminary patch.  It solves the directory issue but it doesn't
> play well with proc_mnt and proc_flush_task.  It works by simply caching the
> network namespace when we mount proc so we don't have to be fancy and dynamic.

Nice... Where should we apply this patch to?

> Something for the discussion anyway.
> 
> I will start sorting out what makes sense tomorrow.
> 
> Eric
> 
> 
>>From f359fde2469ba8be2123a465e788a83c7e6831e9 Mon Sep 17 00:00:00 2001
> From: Eric W. Biederman <ebiederm@xmission.com>
> Date: Tue, 20 Nov 2007 19:36:05 -0700
> Subject: [PATCH] proc: Fix /proc/net directory listings.
> 
> Having proc dynamically display the contents of /proc/net is
> hard.  So make life simpler by capturing the network namespace
> when we mount proc and only displaying that network namespace.
> 
> ---
>  fs/proc/base.c          |    8 ++--
>  fs/proc/generic.c       |    4 ++-
>  fs/proc/internal.h      |   13 +++++++
>  fs/proc/proc_net.c      |   89 ++++-------------------------------------------
>  fs/proc/root.c          |   50 ++++++++++++++++++--------
>  include/linux/proc_fs.h |    4 ++
>  6 files changed, 66 insertions(+), 102 deletions(-)
> 
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index aeaf0d0..9d4f06a 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2395,7 +2395,7 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, struct
>  	if (tgid == ~0U)
>  		goto out;
>  
> -	ns = dentry->d_sb->s_fs_info;
> +	ns = proc_sbi(dentry->d_sb)->pid_ns;
>  	rcu_read_lock();
>  	task = find_task_by_pid_ns(tgid, ns);
>  	if (task)
> @@ -2476,7 +2476,7 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
>  			goto out;
>  	}
>  
> -	ns = filp->f_dentry->d_sb->s_fs_info;
> +	ns = proc_sbi(filp->f_dentry->d_sb)->pid_ns;
>  	tgid = filp->f_pos - TGID_OFFSET;
>  	for (task = next_tgid(tgid, ns);
>  	     task;
> @@ -2615,7 +2615,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
>  	if (tid == ~0U)
>  		goto out;
>  
> -	ns = dentry->d_sb->s_fs_info;
> +	ns = proc_sbi(dentry->d_sb)->pid_ns;
>  	rcu_read_lock();
>  	task = find_task_by_pid_ns(tid, ns);
>  	if (task)
> @@ -2758,7 +2758,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
>  	/* f_version caches the tgid value that the last readdir call couldn't
>  	 * return. lseek aka telldir automagically resets f_version to 0.
>  	 */
> -	ns = filp->f_dentry->d_sb->s_fs_info;
> +	ns = proc_sbi(filp->f_dentry->d_sb)->pid_ns;
>  	tid = (int)filp->f_version;
>  	filp->f_version = 0;
>  	for (task = first_tid(leader, tid, pos - 2, ns);
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index 1bdb624..b58f0ec 100644
> --- a/fs/proc/generic.c
> +++ b/fs/proc/generic.c
> @@ -398,7 +398,9 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
>  				continue;
>  			if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
>  				unsigned int ino = de->low_ino;
> -
> +				
> +				if (de->shadow_proc)
> +					de = de->shadow_proc(dentry->d_sb, de);
>  				de_get(de);
>  				spin_unlock(&proc_subdir_lock);
>  				error = -EINVAL;
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index 1820eb2..a26f115 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -11,6 +11,18 @@
>  
>  #include <linux/proc_fs.h>
>  
> +struct pid_namespace;
> +struct net;
> +struct proc_sb_info {
> +	struct pid_namespace *pid_ns;
> +	struct net	     *net_ns;
> +};
> +
> +static inline struct proc_sb_info *proc_sbi(struct super_block *sb)
> +{
> +	return sb->s_fs_info;
> +}
> +
>  #ifdef CONFIG_PROC_SYSCTL
>  extern int proc_sys_init(void);
>  #else
> @@ -78,3 +90,4 @@ static inline int proc_fd(struct inode *inode)
>  {
>  	return PROC_I(inode)->fd;
>  }
> +
> diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
> index 131f9c6..8a82e29 100644
> --- a/fs/proc/proc_net.c
> +++ b/fs/proc/proc_net.c
> @@ -50,89 +50,15 @@ struct net *get_proc_net(const struct inode *inode)
>  }
>  EXPORT_SYMBOL_GPL(get_proc_net);
>  
> -static struct proc_dir_entry *proc_net_shadow;
> +static struct proc_dir_entry *shadow_pde;
>  
> -static struct dentry *proc_net_shadow_dentry(struct dentry *parent,
> -						struct proc_dir_entry *de)
> +static struct proc_dir_entry *proc_net_shadow(struct super_block *sb,
> +					      struct proc_dir_entry *de)
>  {
> -	struct dentry *shadow = NULL;
> -	struct inode *inode;
> -	if (!de)
> -		goto out;
> -	de_get(de);
> -	inode = proc_get_inode(parent->d_inode->i_sb, de->low_ino, de);
> -	if (!inode)
> -		goto out_de_put;
> -	shadow = d_alloc_name(parent, de->name);
> -	if (!shadow)
> -		goto out_iput;
> -	shadow->d_op = parent->d_op; /* proc_dentry_operations */
> -	d_instantiate(shadow, inode);
> -out:
> -	return shadow;
> -out_iput:
> -	iput(inode);
> -out_de_put:
> -	de_put(de);
> -	goto out;
> -}
> -
> -static void *proc_net_follow_link(struct dentry *parent, struct nameidata *nd)
> -{
> -	struct net *net = current->nsproxy->net_ns;
> -	struct dentry *shadow;
> -	shadow = proc_net_shadow_dentry(parent, net->proc_net);
> -	if (!shadow)
> -		return ERR_PTR(-ENOENT);
> -
> -	dput(nd->dentry);
> -	/* My dentry count is 1 and that should be enough as the
> -	 * shadow dentry is thrown away immediately.
> -	 */
> -	nd->dentry = shadow;
> -	return NULL;
> +	struct proc_sb_info *sbi = proc_sbi(sb);
> +	return sbi->net_ns->proc_net;
>  }
>  
> -static struct dentry *proc_net_lookup(struct inode *dir, struct dentry *dentry,
> -				      struct nameidata *nd)
> -{
> -	struct net *net = current->nsproxy->net_ns;
> -	struct dentry *shadow;
> -
> -	shadow = proc_net_shadow_dentry(nd->dentry, net->proc_net);
> -	if (!shadow)
> -		return ERR_PTR(-ENOENT);
> -
> -	dput(nd->dentry);
> -	nd->dentry = shadow;
> -
> -	return shadow->d_inode->i_op->lookup(shadow->d_inode, dentry, nd);
> -}
> -
> -static int proc_net_setattr(struct dentry *dentry, struct iattr *iattr)
> -{
> -	struct net *net = current->nsproxy->net_ns;
> -	struct dentry *shadow;
> -	int ret;
> -
> -	shadow = proc_net_shadow_dentry(dentry->d_parent, net->proc_net);
> -	if (!shadow)
> -		return -ENOENT;
> -	ret = shadow->d_inode->i_op->setattr(shadow, iattr);
> -	dput(shadow);
> -	return ret;
> -}
> -
> -static const struct file_operations proc_net_dir_operations = {
> -	.read			= generic_read_dir,
> -};
> -
> -static struct inode_operations proc_net_dir_inode_operations = {
> -	.follow_link	= proc_net_follow_link,
> -	.lookup		= proc_net_lookup,
> -	.setattr	= proc_net_setattr,
> -};
> -
>  static __net_init int proc_net_ns_init(struct net *net)
>  {
>  	struct proc_dir_entry *root, *netd, *net_statd;
> @@ -185,9 +111,8 @@ static struct pernet_operations __net_initdata proc_net_ns_ops = {
>  
>  int __init proc_net_init(void)
>  {
> -	proc_net_shadow = proc_mkdir("net", NULL);
> -	proc_net_shadow->proc_iops = &proc_net_dir_inode_operations;
> -	proc_net_shadow->proc_fops = &proc_net_dir_operations;
> +	shadow_pde = proc_mkdir("net", NULL);
> +	shadow_pde->shadow_proc = proc_net_shadow;
>  
>  	return register_pernet_subsys(&proc_net_ns_ops);
>  }
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index ec9cb3b..e60ac83 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -19,6 +19,7 @@
>  #include <linux/smp_lock.h>
>  #include <linux/mount.h>
>  #include <linux/pid_namespace.h>
> +#include <net/net_namespace.h>
>  
>  #include "internal.h"
>  
> @@ -26,15 +27,23 @@ struct proc_dir_entry *proc_bus, *proc_root_fs, *proc_root_driver;
>  
>  static int proc_test_super(struct super_block *sb, void *data)
>  {
> -	return sb->s_fs_info == data;
> +	struct proc_sb_info *sbi = proc_sbi(sb), *info = data;
> +	return	(sbi->pid_ns == info->pid_ns) &&
> +		(sbi->net_ns == info->net_ns);
>  }
>  
>  static int proc_set_super(struct super_block *sb, void *data)
>  {
> -	struct pid_namespace *ns;
> -
> -	ns = (struct pid_namespace *)data;
> -	sb->s_fs_info = get_pid_ns(ns);
> +	
> +	struct proc_sb_info *new, *info = data;
> +	
> +	new = kzalloc(sizeof(*new), GFP_KERNEL);
> +	if (!new)
> +		return -ENOMEM;
> +	*new = *info;
> +	get_pid_ns(new->pid_ns);
> +	get_net(new->net_ns);
> +	sb->s_fs_info = new;
>  	return set_anon_super(sb, NULL);
>  }
>  
> @@ -43,7 +52,7 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  {
>  	int err;
>  	struct super_block *sb;
> -	struct pid_namespace *ns;
> +	struct proc_sb_info info, *sbi;
>  	struct proc_inode *ei;
>  
>  	if (proc_mnt) {
> @@ -57,12 +66,14 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  			ei->pid = find_get_pid(1);
>  	}
>  
> +	info.pid_ns = current->nsproxy->pid_ns;
> +	info.net_ns = current->nsproxy->net_ns;
>  	if (flags & MS_KERNMOUNT)
> -		ns = (struct pid_namespace *)data;
> +		sbi = data;
>  	else
> -		ns = current->nsproxy->pid_ns;
> +		sbi = &info;
>  
> -	sb = sget(fs_type, proc_test_super, proc_set_super, ns);
> +	sb = sget(fs_type, proc_test_super, proc_set_super, sbi);
>  	if (IS_ERR(sb))
>  		return PTR_ERR(sb);
>  
> @@ -78,12 +89,13 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  		ei = PROC_I(sb->s_root->d_inode);
>  		if (!ei->pid) {
>  			rcu_read_lock();
> -			ei->pid = get_pid(find_pid_ns(1, ns));
> +			ei->pid = get_pid(find_pid_ns(1, sbi->pid_ns));
>  			rcu_read_unlock();
>  		}
>  
>  		sb->s_flags |= MS_ACTIVE;
> -		ns->proc_mnt = mnt;
> +		if (!sbi->pid_ns->proc_mnt)
> +			sbi->pid_ns->proc_mnt = mnt;
>  	}
>  
>  	return simple_set_mnt(mnt, sb);
> @@ -91,11 +103,13 @@ static int proc_get_sb(struct file_system_type *fs_type,
>  
>  static void proc_kill_sb(struct super_block *sb)
>  {
> -	struct pid_namespace *ns;
> +	struct proc_sb_info *sbi;
>  
> -	ns = (struct pid_namespace *)sb->s_fs_info;
> +	sbi = proc_sbi(sb);
>  	kill_anon_super(sb);
> -	put_pid_ns(ns);
> +	put_pid_ns(sbi->pid_ns);
> +	put_net(sbi->net_ns);
> +	kfree(sbi);
>  }
>  
>  static struct file_system_type proc_fs_type = {
> @@ -106,13 +120,16 @@ static struct file_system_type proc_fs_type = {
>  
>  void __init proc_root_init(void)
>  {
> +	struct proc_sb_info info;
>  	int err = proc_init_inodecache();
>  	if (err)
>  		return;
>  	err = register_filesystem(&proc_fs_type);
>  	if (err)
>  		return;
> -	proc_mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
> +	info.pid_ns = &init_pid_ns;
> +	info.net_ns = current->nsproxy->net_ns;
> +	proc_mnt = kern_mount_data(&proc_fs_type, &info);
>  	err = PTR_ERR(proc_mnt);
>  	if (IS_ERR(proc_mnt)) {
>  		unregister_filesystem(&proc_fs_type);
> @@ -214,8 +231,11 @@ struct proc_dir_entry proc_root = {
>  
>  int pid_ns_prepare_proc(struct pid_namespace *ns)
>  {
> +	struct proc_sb_info info;
>  	struct vfsmount *mnt;
>  
> +	info.pid_ns = ns;
> +	info.net_ns = current->nsproxy->net_ns;
>  	mnt = kern_mount_data(&proc_fs_type, ns);
>  	if (IS_ERR(mnt))
>  		return PTR_ERR(mnt);
> diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
> index 2b3c1d8..c22c558 100644
> --- a/include/linux/proc_fs.h
> +++ b/include/linux/proc_fs.h
> @@ -48,6 +48,9 @@ typedef	int (read_proc_t)(char *page, char **start, off_t off,
>  typedef	int (write_proc_t)(struct file *file, const char __user *buffer,
>  			   unsigned long count, void *data);
>  typedef int (get_info_t)(char *, char **, off_t, int);
> +struct proc_dir_entry;
> +typedef struct proc_dir_entry *(shadow_proc_t)(struct super_block *sb,
> +						  struct proc_dir_entry *pde);
>  
>  struct proc_dir_entry {
>  	unsigned int low_ino;
> @@ -79,6 +82,7 @@ struct proc_dir_entry {
>  	int pde_users;	/* number of callers into module in progress */
>  	spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
>  	struct completion *pde_unload_completion;
> +	shadow_proc_t *shadow_proc;
>  };
>  
>  struct kcore_list {