[PATCH 00/10] sysfs tagged directories V4

[PATCH 00/10] sysfs tagged directories V4

[Benjamin Thery]

Here is an updated version of Eric Biederman's patchset to implement
tagged directories in sysfs ported on top of 2.6.26-rc2-mm1.

Andrew,
Can you consider merging this patchset in -mm until gregkh has time 
to re-review it and take it (or reject it)?
We think having it in -mm, could be good for wider testing of this
proposed new feature in sysfs.

Thanks,
Benjamin

--

With the introduction of network namespaces, there can be duplicate 
network interface names on the same machine. Indeed, two network 
interfaces can have the same name if they reside in different network
namespaces. 

* Network interfaces names show up in sysfs.
* Today there is nothing in sysfs that is currently per namespace.
* Therefore we need to support multiple mounts of sysfs each showing a 
  different network namespace.

We introduce tagged directories in sysfs for this purpose.

Of course the usefulness of this feature is not limited to network stuff:
Serge Hallyn wrote a patch to fix a similar issue with user namespaces based 
on this patchset. His patch is included at the end of the patchset.

Tested with and without SYSFS_DEPRECATED. No regression found so far.

Changelog
---------
* V4:
  - Ported to 2.6.26-rc2-mm1
  - Updated patch for user namespace by Serge Hallyn (patch 10).
* V3:
  - Removed patch 10 ("avoid kobject name conflict with different 
    namespaces"), a better one was provided by Eric.
  - Removed patch 11 ("sysfs: user namespaces: add ns to user_struct"),
    Serge needs to rework some parts of it.
  - Change Acked-by: to Signed-off-by:, someone told me it is more 
    appropriate (as I'm in the delivery path).


Here is the announcement Eric wrote back in December to introduce his 
patchset:

"
Now that we have network namespace support merged it is time to
revisit the sysfs support so we can remove the dependency on !SYSFS.
[...]
The bulk of the patches are the changes to allow multiple sysfs
superblocks.

Then comes the tagged directory sysfs support which uses information
captured at mount time to decide which object with which tag will
appear in a directory.

Then the support for renaming and deleting objects where the source
may be ambiguous because of tagging.

Then finally the network namespace support so it is clear how all
of this tied together.
"

Regards,
Benjamin

-- 

[PATCH 01/10] sysfs: Support for preventing unmounts.

[Benjamin Thery]

sysfs: Support for preventing unmounts.

To support mounting multiple instances of sysfs occassionally I
need to walk through all of the currently present sysfs super blocks.

To allow this iteration this patch adds sysfs_grab_supers
and sysfs_release_supers.  While a piece of code is in
a section surrounded by these no more sysfs super blocks
will be either created or destroyed.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/mount.c |   79 +++++++++++++++++++++++++++++++++++++++++++++++++------
 fs/sysfs/sysfs.h |   10 ++++++
 2 files changed, 81 insertions(+), 8 deletions(-)

Index: linux-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/fs/sysfs/mount.c
@@ -41,47 +41,110 @@ struct sysfs_dirent sysfs_root = {
 
 static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
 {
-	struct inode *inode;
-	struct dentry *root;
+	struct sysfs_super_info *info = NULL;
+	struct inode *inode = NULL;
+	struct dentry *root = NULL;
+	int error;
 
 	sb->s_blocksize = PAGE_CACHE_SIZE;
 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
 	sb->s_magic = SYSFS_MAGIC;
 	sb->s_op = &sysfs_ops;
 	sb->s_time_gran = 1;
-	sysfs_sb = sb;
+	if (!sysfs_sb)
+		sysfs_sb = sb;
+
+	error = -ENOMEM;
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		goto out_err;
 
 	/* get root inode, initialize and unlock it */
+	error = -ENOMEM;
 	inode = sysfs_get_inode(&sysfs_root);
 	if (!inode) {
 		pr_debug("sysfs: could not get root inode\n");
-		return -ENOMEM;
+		goto out_err;
 	}
 
 	/* instantiate and link root dentry */
+	error = -ENOMEM;
 	root = d_alloc_root(inode);
 	if (!root) {
 		pr_debug("%s: could not get root dentry!\n",__func__);
-		iput(inode);
-		return -ENOMEM;
+		goto out_err;
 	}
 	root->d_fsdata = &sysfs_root;
 	sb->s_root = root;
+	sb->s_fs_info = info;
 	return 0;
+
+out_err:
+	dput(root);
+	iput(inode);
+	kfree(info);
+	if (sysfs_sb == sb)
+		sysfs_sb = NULL;
+	return error;
 }
 
 static int sysfs_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
-	return get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+	int rc;
+	mutex_lock(&sysfs_rename_mutex);
+	rc = get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+	mutex_unlock(&sysfs_rename_mutex);
+	return rc;
 }
 
-static struct file_system_type sysfs_fs_type = {
+struct file_system_type sysfs_fs_type = {
 	.name		= "sysfs",
 	.get_sb		= sysfs_get_sb,
 	.kill_sb	= kill_anon_super,
 };
 
+void sysfs_grab_supers(void)
+{
+	/* must hold sysfs_rename_mutex */
+	struct super_block *sb;
+	/* Loop until I have taken s_umount on all sysfs superblocks */
+restart:
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		if (sysfs_info(sb)->grabbed)
+			continue;
+		/* Wait for unmount activity to complete. */
+		if (sb->s_count < S_BIAS) {
+			sb->s_count += 1;
+			spin_unlock(&sb_lock);
+			down_read(&sb->s_umount);
+			drop_super(sb);
+			goto restart;
+		}
+		atomic_inc(&sb->s_active);
+		sysfs_info(sb)->grabbed = 1;
+	}
+	spin_unlock(&sb_lock);
+}
+
+void sysfs_release_supers(void)
+{
+	/* must hold sysfs_rename_mutex */
+	struct super_block *sb;
+restart:
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		if (!sysfs_info(sb)->grabbed)
+			continue;
+		sysfs_info(sb)->grabbed = 0;
+		spin_unlock(&sb_lock);
+		deactivate_super(sb);
+		goto restart;
+	}
+	spin_unlock(&sb_lock);
+}
+
 int __init sysfs_init(void)
 {
 	int err = -ENOMEM;
Index: linux-mm/fs/sysfs/sysfs.h
===================================================================
--- linux-mm.orig/fs/sysfs/sysfs.h
+++ linux-mm/fs/sysfs/sysfs.h
@@ -85,6 +85,12 @@ struct sysfs_addrm_cxt {
 	int			cnt;
 };
 
+struct sysfs_super_info {
+	int	grabbed;
+};
+
+#define sysfs_info(SB) ((struct sysfs_super_info *)(SB)->s_fs_info)
+
 /*
  * mount.c
  */
@@ -92,6 +98,10 @@ extern struct sysfs_dirent sysfs_root;
 extern struct super_block *sysfs_sb;
 extern struct kmem_cache *sysfs_dir_cachep;
 extern struct vfsmount *sysfs_mount;
+extern struct file_system_type sysfs_fs_type;
+
+void sysfs_grab_supers(void);
+void sysfs_release_supers(void);
 
 /*
  * dir.c

-- 

[PATCH 02/10] sysfs: sysfs_get_dentry add a sb parameter

[Benjamin Thery]

sysfs: sysfs_get_dentry add a sb parameter

In preparation for multiple mounts of sysfs add a superblock parameter to
sysfs_get_dentry.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/dir.c   |   12 +++++++-----
 fs/sysfs/file.c  |    2 +-
 fs/sysfs/sysfs.h |    3 ++-
 3 files changed, 10 insertions(+), 7 deletions(-)

Index: linux-mm/fs/sysfs/dir.c
===================================================================
--- linux-mm.orig/fs/sysfs/dir.c
+++ linux-mm/fs/sysfs/dir.c
@@ -87,6 +87,7 @@ static void sysfs_unlink_sibling(struct 
 
 /**
  *	sysfs_get_dentry - get dentry for the given sysfs_dirent
+ *	@sb: superblock of the dentry to return
  *	@sd: sysfs_dirent of interest
  *
  *	Get dentry for @sd.  Dentry is looked up if currently not
@@ -99,9 +100,10 @@ static void sysfs_unlink_sibling(struct 
  *	RETURNS:
  *	Pointer to found dentry on success, ERR_PTR() value on error.
  */
-struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
+struct dentry *sysfs_get_dentry(struct super_block *sb,
+				struct sysfs_dirent *sd)
 {
-	struct dentry *dentry = dget(sysfs_sb->s_root);
+	struct dentry *dentry = dget(sb->s_root);
 
 	while (dentry->d_fsdata != sd) {
 		struct sysfs_dirent *cur;
@@ -790,7 +792,7 @@ int sysfs_rename_dir(struct kobject * ko
 		goto out;	/* nothing to rename */
 
 	/* get the original dentry */
-	old_dentry = sysfs_get_dentry(sd);
+	old_dentry = sysfs_get_dentry(sysfs_sb, sd);
 	if (IS_ERR(old_dentry)) {
 		error = PTR_ERR(old_dentry);
 		old_dentry = NULL;
@@ -858,7 +860,7 @@ int sysfs_move_dir(struct kobject *kobj,
 		goto out;	/* nothing to move */
 
 	/* get dentries */
-	old_dentry = sysfs_get_dentry(sd);
+	old_dentry = sysfs_get_dentry(sysfs_sb, sd);
 	if (IS_ERR(old_dentry)) {
 		error = PTR_ERR(old_dentry);
 		old_dentry = NULL;
@@ -866,7 +868,7 @@ int sysfs_move_dir(struct kobject *kobj,
 	}
 	old_parent = old_dentry->d_parent;
 
-	new_parent = sysfs_get_dentry(new_parent_sd);
+	new_parent = sysfs_get_dentry(sysfs_sb, new_parent_sd);
 	if (IS_ERR(new_parent)) {
 		error = PTR_ERR(new_parent);
 		new_parent = NULL;
Index: linux-mm/fs/sysfs/file.c
===================================================================
--- linux-mm.orig/fs/sysfs/file.c
+++ linux-mm/fs/sysfs/file.c
@@ -584,7 +584,7 @@ int sysfs_chmod_file(struct kobject *kob
 		goto out;
 
 	mutex_lock(&sysfs_rename_mutex);
-	victim = sysfs_get_dentry(victim_sd);
+	victim = sysfs_get_dentry(sysfs_sb, victim_sd);
 	mutex_unlock(&sysfs_rename_mutex);
 	if (IS_ERR(victim)) {
 		rc = PTR_ERR(victim);
Index: linux-mm/fs/sysfs/sysfs.h
===================================================================
--- linux-mm.orig/fs/sysfs/sysfs.h
+++ linux-mm/fs/sysfs/sysfs.h
@@ -113,7 +113,8 @@ extern spinlock_t sysfs_assoc_lock;
 extern const struct file_operations sysfs_dir_operations;
 extern const struct inode_operations sysfs_dir_inode_operations;
 
-struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd);
+struct dentry *sysfs_get_dentry(struct super_block *sb,
+				struct sysfs_dirent *sd);
 struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd);
 void sysfs_put_active_two(struct sysfs_dirent *sd);
 void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,

-- 

[PATCH 03/10] sysfs: Implement __sysfs_get_dentry

[Benjamin Thery]

sysfs: Implement __sysfs_get_dentry

This function is similar but much simpler to sysfs_get_dentry
returns a sysfs dentry if one curently exists.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/dir.c |   39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

Index: linux-mm/fs/sysfs/dir.c
===================================================================
--- linux-mm.orig/fs/sysfs/dir.c
+++ linux-mm/fs/sysfs/dir.c
@@ -777,6 +777,45 @@ void sysfs_remove_dir(struct kobject * k
 	__sysfs_remove_dir(sd);
 }
 
+/**
+ *	__sysfs_get_dentry - get dentry for the given sysfs_dirent
+ *	@sb: superblock of the dentry to return
+ *	@sd: sysfs_dirent of interest
+ *
+ *	Get dentry for @sd.  Only return a dentry if one currently
+ *	exists.
+ *
+ *	LOCKING:
+ *	Kernel thread context (may sleep)
+ *
+ *	RETURNS:
+ *	Pointer to found dentry on success, NULL on failure.
+ */
+static struct dentry *__sysfs_get_dentry(struct super_block *sb,
+					 struct sysfs_dirent *sd)
+{
+	struct inode *inode;
+	struct dentry *dentry = NULL;
+
+	inode = ilookup5_nowait(sysfs_sb, sd->s_ino, sysfs_ilookup_test, sd);
+	if (inode && !(inode->i_state & I_NEW)) {
+		struct dentry *alias;
+		spin_lock(&dcache_lock);
+		list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+			if (!IS_ROOT(alias) && d_unhashed(alias))
+				continue;
+			if (alias->d_sb != sb)
+				continue;
+			dentry = alias;
+			dget_locked(dentry);
+			break;
+		}
+		spin_unlock(&dcache_lock);
+	}
+	iput(inode);
+	return dentry;
+}
+
 int sysfs_rename_dir(struct kobject * kobj, const char *new_name)
 {
 	struct sysfs_dirent *sd = kobj->sd;

-- 

[PATCH 04/10] sysfs: Rename Support multiple superblocks

[Benjamin Thery]

sysfs: Rename Support multiple superblocks

This patch modifies the sysfs_rename_dir and sysfs_move_dir routines
to support multiple sysfs dentry tries rooted in different
sysfs superblocks.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/dir.c |  194 +++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 136 insertions(+), 58 deletions(-)

Index: linux-mm/fs/sysfs/dir.c
===================================================================
--- linux-mm.orig/fs/sysfs/dir.c
+++ linux-mm/fs/sysfs/dir.c
@@ -816,43 +816,112 @@ static struct dentry *__sysfs_get_dentry
 	return dentry;
 }
 
+struct sysfs_rename_struct {
+	struct list_head list;
+	struct dentry *old_dentry;
+	struct dentry *new_dentry;
+	struct dentry *old_parent;
+	struct dentry *new_parent;
+};
+
+static void post_rename(struct list_head *head)
+{
+	struct sysfs_rename_struct *srs;
+	while (!list_empty(head)) {
+		srs = list_entry(head->next, struct sysfs_rename_struct, list);
+		dput(srs->old_dentry);
+		dput(srs->new_dentry);
+		dput(srs->old_parent);
+		dput(srs->new_parent);
+		list_del(&srs->list);
+		kfree(srs);
+	}
+}
+
+static int prep_rename(struct list_head *head,
+	struct sysfs_dirent *sd, struct sysfs_dirent *new_parent_sd,
+	const char *name)
+{
+	struct sysfs_rename_struct *srs;
+	struct super_block *sb;
+	struct dentry *dentry;
+	int error;
+
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		dentry = sysfs_get_dentry(sb, sd);
+		if (dentry == ERR_PTR(-EXDEV))
+			continue;
+		if (IS_ERR(dentry)) {
+			error = PTR_ERR(dentry);
+			goto err_out;
+		}
+
+		srs = kzalloc(sizeof(*srs), GFP_KERNEL);
+		if (!srs) {
+			dput(dentry);
+			goto err_out;
+		}
+
+		INIT_LIST_HEAD(&srs->list);
+		list_add(head, &srs->list);
+		srs->old_dentry = dentry;
+		srs->old_parent = dget(dentry->d_parent);
+
+		dentry = sysfs_get_dentry(sb, new_parent_sd);
+		if (IS_ERR(dentry)) {
+			error = PTR_ERR(dentry);
+			goto err_out;
+		}
+		srs->new_parent = dentry;
+
+		error = -ENOMEM;
+		dentry = d_alloc_name(srs->new_parent, name);
+		if (!dentry)
+			goto err_out;
+		srs->new_dentry = dentry;
+	}
+	return 0;
+
+err_out:
+	post_rename(head);
+	return error;
+}
+
 int sysfs_rename_dir(struct kobject * kobj, const char *new_name)
 {
 	struct sysfs_dirent *sd = kobj->sd;
-	struct dentry *parent = NULL;
-	struct dentry *old_dentry = NULL, *new_dentry = NULL;
+	struct list_head todo;
+	struct sysfs_rename_struct *srs;
+	struct inode *parent_inode = NULL;
 	const char *dup_name = NULL;
 	int error;
 
+	INIT_LIST_HEAD(&todo);
 	mutex_lock(&sysfs_rename_mutex);
 
 	error = 0;
 	if (strcmp(sd->s_name, new_name) == 0)
 		goto out;	/* nothing to rename */
 
-	/* get the original dentry */
-	old_dentry = sysfs_get_dentry(sysfs_sb, sd);
-	if (IS_ERR(old_dentry)) {
-		error = PTR_ERR(old_dentry);
-		old_dentry = NULL;
-		goto out;
-	}
+	sysfs_grab_supers();
+	error = prep_rename(&todo, sd, sd->s_parent, new_name);
+	if (error)
+		goto out_release;
 
-	parent = old_dentry->d_parent;
+	error = -ENOMEM;
+	mutex_lock(&sysfs_mutex);
+	parent_inode = sysfs_get_inode(sd->s_parent);
+	mutex_unlock(&sysfs_mutex);
+	if (!parent_inode)
+		goto out_release;
 
-	/* lock parent and get dentry for new name */
-	mutex_lock(&parent->d_inode->i_mutex);
+	mutex_lock(&parent_inode->i_mutex);
 	mutex_lock(&sysfs_mutex);
 
 	error = -EEXIST;
 	if (sysfs_find_dirent(sd->s_parent, new_name))
 		goto out_unlock;
 
-	error = -ENOMEM;
-	new_dentry = d_alloc_name(parent, new_name);
-	if (!new_dentry)
-		goto out_unlock;
-
 	/* rename kobject and sysfs_dirent */
 	error = -ENOMEM;
 	new_name = dup_name = kstrdup(new_name, GFP_KERNEL);
@@ -867,17 +936,21 @@ int sysfs_rename_dir(struct kobject * ko
 	sd->s_name = new_name;
 
 	/* rename */
-	d_add(new_dentry, NULL);
-	d_move(old_dentry, new_dentry);
+	list_for_each_entry(srs, &todo, list) {
+		d_add(srs->new_dentry, NULL);
+		d_move(srs->old_dentry, srs->new_dentry);
+	}
 
 	error = 0;
- out_unlock:
+out_unlock:
 	mutex_unlock(&sysfs_mutex);
-	mutex_unlock(&parent->d_inode->i_mutex);
+	mutex_unlock(&parent_inode->i_mutex);
 	kfree(dup_name);
-	dput(old_dentry);
-	dput(new_dentry);
- out:
+out_release:
+	iput(parent_inode);
+	post_rename(&todo);
+	sysfs_release_supers();
+out:
 	mutex_unlock(&sysfs_rename_mutex);
 	return error;
 }
@@ -886,10 +959,12 @@ int sysfs_move_dir(struct kobject *kobj,
 {
 	struct sysfs_dirent *sd = kobj->sd;
 	struct sysfs_dirent *new_parent_sd;
-	struct dentry *old_parent, *new_parent = NULL;
-	struct dentry *old_dentry = NULL, *new_dentry = NULL;
+	struct list_head todo;
+	struct sysfs_rename_struct *srs;
+	struct inode *old_parent_inode = NULL, *new_parent_inode = NULL;
 	int error;
 
+	INIT_LIST_HEAD(&todo);
 	mutex_lock(&sysfs_rename_mutex);
 	BUG_ON(!sd->s_parent);
 	new_parent_sd = new_parent_kobj->sd ? new_parent_kobj->sd : &sysfs_root;
@@ -898,26 +973,29 @@ int sysfs_move_dir(struct kobject *kobj,
 	if (sd->s_parent == new_parent_sd)
 		goto out;	/* nothing to move */
 
-	/* get dentries */
-	old_dentry = sysfs_get_dentry(sysfs_sb, sd);
-	if (IS_ERR(old_dentry)) {
-		error = PTR_ERR(old_dentry);
-		old_dentry = NULL;
-		goto out;
-	}
-	old_parent = old_dentry->d_parent;
-
-	new_parent = sysfs_get_dentry(sysfs_sb, new_parent_sd);
-	if (IS_ERR(new_parent)) {
-		error = PTR_ERR(new_parent);
-		new_parent = NULL;
-		goto out;
-	}
+	sysfs_grab_supers();
+	error = prep_rename(&todo, sd, new_parent_sd, sd->s_name);
+	if (error)
+		goto out_release;
+
+	error = -ENOMEM;
+	mutex_lock(&sysfs_mutex);
+	old_parent_inode = sysfs_get_inode(sd->s_parent);
+	mutex_unlock(&sysfs_mutex);
+	if (!old_parent_inode)
+		goto out_release;
+
+	error = -ENOMEM;
+	mutex_lock(&sysfs_mutex);
+	new_parent_inode = sysfs_get_inode(new_parent_sd);
+	mutex_unlock(&sysfs_mutex);
+	if (!new_parent_inode)
+		goto out_release;
 
 again:
-	mutex_lock(&old_parent->d_inode->i_mutex);
-	if (!mutex_trylock(&new_parent->d_inode->i_mutex)) {
-		mutex_unlock(&old_parent->d_inode->i_mutex);
+	mutex_lock(&old_parent_inode->i_mutex);
+	if (!mutex_trylock(&new_parent_inode->i_mutex)) {
+		mutex_unlock(&old_parent_inode->i_mutex);
 		goto again;
 	}
 	mutex_lock(&sysfs_mutex);
@@ -926,14 +1004,11 @@ again:
 	if (sysfs_find_dirent(new_parent_sd, sd->s_name))
 		goto out_unlock;
 
-	error = -ENOMEM;
-	new_dentry = d_alloc_name(new_parent, sd->s_name);
-	if (!new_dentry)
-		goto out_unlock;
-
 	error = 0;
-	d_add(new_dentry, NULL);
-	d_move(old_dentry, new_dentry);
+	list_for_each_entry(srs, &todo, list) {
+		d_add(srs->new_dentry, NULL);
+		d_move(srs->old_dentry, srs->new_dentry);
+	}
 
 	/* Remove from old parent's list and insert into new parent's list. */
 	sysfs_unlink_sibling(sd);
@@ -942,14 +1017,17 @@ again:
 	sd->s_parent = new_parent_sd;
 	sysfs_link_sibling(sd);
 
- out_unlock:
+out_unlock:
 	mutex_unlock(&sysfs_mutex);
-	mutex_unlock(&new_parent->d_inode->i_mutex);
-	mutex_unlock(&old_parent->d_inode->i_mutex);
- out:
-	dput(new_parent);
-	dput(old_dentry);
-	dput(new_dentry);
+	mutex_unlock(&new_parent_inode->i_mutex);
+	mutex_unlock(&old_parent_inode->i_mutex);
+
+out_release:
+	iput(new_parent_inode);
+	iput(old_parent_inode);
+	post_rename(&todo);
+	sysfs_release_supers();
+out:
 	mutex_unlock(&sysfs_rename_mutex);
 	return error;
 }

-- 

[PATCH 05/10] sysfs: sysfs_chmod_file handle multiple superblocks

[Benjamin Thery]

sysfs: sysfs_chmod_file handle multiple superblocks

Teach sysfs_chmod_file how to handle multiple sysfs
superblocks.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/file.c |   54 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 30 insertions(+), 24 deletions(-)

Index: linux-mm/fs/sysfs/file.c
===================================================================
--- linux-mm.orig/fs/sysfs/file.c
+++ linux-mm/fs/sysfs/file.c
@@ -573,7 +573,8 @@ EXPORT_SYMBOL_GPL(sysfs_add_file_to_grou
 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 {
 	struct sysfs_dirent *victim_sd = NULL;
-	struct dentry *victim = NULL;
+	struct super_block *sb;
+	struct dentry *victim;
 	struct inode * inode;
 	struct iattr newattrs;
 	int rc;
@@ -584,31 +585,36 @@ int sysfs_chmod_file(struct kobject *kob
 		goto out;
 
 	mutex_lock(&sysfs_rename_mutex);
-	victim = sysfs_get_dentry(sysfs_sb, victim_sd);
-	mutex_unlock(&sysfs_rename_mutex);
-	if (IS_ERR(victim)) {
-		rc = PTR_ERR(victim);
-		victim = NULL;
-		goto out;
-	}
-
-	inode = victim->d_inode;
+	sysfs_grab_supers();
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		victim = sysfs_get_dentry(sb, victim_sd);
+		if (victim == ERR_PTR(-EXDEV))
+			continue;
+		if (IS_ERR(victim)) {
+			rc = PTR_ERR(victim);
+			victim = NULL;
+			goto out_unlock;
+		}
+
+		inode = victim->d_inode;
+		mutex_lock(&inode->i_mutex);
+		newattrs.ia_mode = (mode & S_IALLUGO) |
+				   (inode->i_mode & ~S_IALLUGO);
+		newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+		rc = notify_change(victim, &newattrs);
+		if (rc == 0) {
+			mutex_lock(&sysfs_mutex);
+			victim_sd->s_mode = newattrs.ia_mode;
+			mutex_unlock(&sysfs_mutex);
+		}
+		mutex_unlock(&inode->i_mutex);
 
-	mutex_lock(&inode->i_mutex);
-
-	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
-	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
-	rc = notify_change(victim, &newattrs);
-
-	if (rc == 0) {
-		mutex_lock(&sysfs_mutex);
-		victim_sd->s_mode = newattrs.ia_mode;
-		mutex_unlock(&sysfs_mutex);
+		dput(victim);
 	}
-
-	mutex_unlock(&inode->i_mutex);
- out:
-	dput(victim);
+out_unlock:
+	sysfs_release_supers();
+	mutex_unlock(&sysfs_rename_mutex);
+out:
 	sysfs_put(victim_sd);
 	return rc;
 }

-- 

[PATCH 06/10] sysfs: Implement sysfs tagged directory support.

[Benjamin Thery]

sysfs: Implement sysfs tagged directory support.

The problem.  When implementing a network namespace I need to be able
to have multiple network devices with the same name.  Currently this
is a problem for /sys/class/net/*, /sys/devices/virtual/net/*, and
potentially a few other directories of the form /sys/ ... /net/*.

What this patch does is to add an additional tag field to the
sysfs dirent structure.  For directories that should show different
contents depending on the context such as /sys/class/net/, and
/sys/devices/virtual/net/ this tag field is used to specify the
context in which those directories should be visible.  Effectively
this is the same as creating multiple distinct directories with
the same name but internally to sysfs the result is nicer.

I am calling the concept of a single directory that looks like multiple
directories all at the same path in the filesystem tagged directories.

For the networking namespace the set of directories whose contents I need
to filter with tags can depend on the presence or absence of hotplug
hardware or which modules are currently loaded.  Which means I need
a simple race free way to setup those directories as tagged.

To achieve a race free design all tagged directories are created
and managed by sysfs itself. The upper level code that knows what
tagged directories we need provides just two methods that enable
this:
  sb_tag() - that returns a "void *" tag that identifies the context of
	the process that mounted sysfs.
  kobject_tag(kobj) - that returns a "void *" tag that identifies the context
	a kobject should be in.
Everything else is left up to sysfs.

For the network namespace sb_tag and kobject_tag are essentially
one line functions, and look to remain that.

The work needed in sysfs is more extensive.  At each directory
or symlink creating I need to check if the directory it is being
created in is a tagged directory and if so generate the appropriate
tag to place on the sysfs_dirent.  Likewise at each symlink or
directory removal I need to check if the sysfs directory it is
being removed from is a tagged directory and if so figure out
which tag goes along with the name I am deleting.

Currently only directories which hold kobjects, and
symlinks are supported.  There is not enough information
in the current file attribute interfaces to give us anything
to discriminate on which makes it useless, and there are
no potential users which makes it an uninteresting problem
to solve.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/bin.c        |    2 
 fs/sysfs/dir.c        |  185 ++++++++++++++++++++++++++++++++++++++++++++++----
 fs/sysfs/file.c       |    8 +-
 fs/sysfs/group.c      |    4 -
 fs/sysfs/inode.c      |    7 +
 fs/sysfs/mount.c      |   44 ++++++++++-
 fs/sysfs/symlink.c    |    2 
 fs/sysfs/sysfs.h      |   17 ++++
 include/linux/sysfs.h |   17 ++++
 9 files changed, 257 insertions(+), 29 deletions(-)

Index: linux-mm/fs/sysfs/bin.c
===================================================================
--- linux-mm.orig/fs/sysfs/bin.c
+++ linux-mm/fs/sysfs/bin.c
@@ -252,7 +252,7 @@ int sysfs_create_bin_file(struct kobject
 
 void sysfs_remove_bin_file(struct kobject * kobj, struct bin_attribute * attr)
 {
-	sysfs_hash_and_remove(kobj->sd, attr->attr.name);
+	sysfs_hash_and_remove(kobj, kobj->sd, attr->attr.name);
 }
 
 EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
Index: linux-mm/fs/sysfs/dir.c
===================================================================
--- linux-mm.orig/fs/sysfs/dir.c
+++ linux-mm/fs/sysfs/dir.c
@@ -103,8 +103,17 @@ static void sysfs_unlink_sibling(struct 
 struct dentry *sysfs_get_dentry(struct super_block *sb,
 				struct sysfs_dirent *sd)
 {
-	struct dentry *dentry = dget(sb->s_root);
+	struct dentry *dentry;
+
+	/* Bail if this sd won't show up in this superblock */
+	if (sd->s_parent && sd->s_parent->s_flags & SYSFS_FLAG_TAGGED) {
+		const void *tag;
+		tag = sysfs_lookup_tag(sd->s_parent, sb);
+		if (sd->s_tag.tag != tag)
+			return ERR_PTR(-EXDEV);
+	}
 
+	dentry = dget(sb->s_root);
 	while (dentry->d_fsdata != sd) {
 		struct sysfs_dirent *cur;
 		struct dentry *parent;
@@ -423,7 +432,11 @@ void sysfs_addrm_start(struct sysfs_addr
  */
 int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
 {
-	if (sysfs_find_dirent(acxt->parent_sd, sd->s_name)) {
+	const void *tag = NULL;
+
+	tag = sysfs_creation_tag(acxt->parent_sd, sd);
+
+	if (sysfs_find_dirent(acxt->parent_sd, tag, sd->s_name)) {
 		printk(KERN_WARNING "sysfs: duplicate filename '%s' "
 		       "can not be created\n", sd->s_name);
 		WARN_ON(1);
@@ -439,6 +452,9 @@ int sysfs_add_one(struct sysfs_addrm_cxt
 
 	sd->s_parent = sysfs_get(acxt->parent_sd);
 
+	if (sd->s_parent->s_flags & SYSFS_FLAG_TAGGED)
+		sd->s_tag.tag = tag;
+
 	if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
 		inc_nlink(acxt->parent_inode);
 
@@ -585,13 +601,18 @@ void sysfs_addrm_finish(struct sysfs_add
  *	Pointer to sysfs_dirent if found, NULL if not.
  */
 struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
+				       const void *tag,
 				       const unsigned char *name)
 {
 	struct sysfs_dirent *sd;
 
-	for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling)
+	for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) {
+		if ((parent_sd->s_flags & SYSFS_FLAG_TAGGED) &&
+		    (sd->s_tag.tag != tag))
+			continue;
 		if (!strcmp(sd->s_name, name))
 			return sd;
+	}
 	return NULL;
 }
 
@@ -615,7 +636,7 @@ struct sysfs_dirent *sysfs_get_dirent(st
 	struct sysfs_dirent *sd;
 
 	mutex_lock(&sysfs_mutex);
-	sd = sysfs_find_dirent(parent_sd, name);
+	sd = sysfs_find_dirent(parent_sd, NULL, name);
 	sysfs_get(sd);
 	mutex_unlock(&sysfs_mutex);
 
@@ -681,13 +702,16 @@ static struct dentry * sysfs_lookup(stru
 				struct nameidata *nd)
 {
 	struct dentry *ret = NULL;
-	struct sysfs_dirent *parent_sd = dentry->d_parent->d_fsdata;
+	struct dentry *parent = dentry->d_parent;
+	struct sysfs_dirent *parent_sd = parent->d_fsdata;
 	struct sysfs_dirent *sd;
 	struct inode *inode;
+	const void *tag;
 
 	mutex_lock(&sysfs_mutex);
 
-	sd = sysfs_find_dirent(parent_sd, dentry->d_name.name);
+	tag = sysfs_lookup_tag(parent_sd, parent->d_sb);
+	sd = sysfs_find_dirent(parent_sd, tag, dentry->d_name.name);
 
 	/* no such entry */
 	if (!sd) {
@@ -894,19 +918,24 @@ int sysfs_rename_dir(struct kobject * ko
 	struct sysfs_rename_struct *srs;
 	struct inode *parent_inode = NULL;
 	const char *dup_name = NULL;
+	const void *old_tag, *tag;
 	int error;
 
 	INIT_LIST_HEAD(&todo);
 	mutex_lock(&sysfs_rename_mutex);
+	old_tag = sysfs_dirent_tag(sd);
+	tag = sysfs_creation_tag(sd->s_parent, sd);
 
 	error = 0;
-	if (strcmp(sd->s_name, new_name) == 0)
+	if ((old_tag == tag) && (strcmp(sd->s_name, new_name) == 0))
 		goto out;	/* nothing to rename */
 
 	sysfs_grab_supers();
-	error = prep_rename(&todo, sd, sd->s_parent, new_name);
-	if (error)
-		goto out_release;
+	if (old_tag == tag) {
+		error = prep_rename(&todo, sd, sd->s_parent, new_name);
+		if (error)
+			goto out_release;
+	}
 
 	error = -ENOMEM;
 	mutex_lock(&sysfs_mutex);
@@ -919,7 +948,7 @@ int sysfs_rename_dir(struct kobject * ko
 	mutex_lock(&sysfs_mutex);
 
 	error = -EEXIST;
-	if (sysfs_find_dirent(sd->s_parent, new_name))
+	if (sysfs_find_dirent(sd->s_parent, tag, new_name))
 		goto out_unlock;
 
 	/* rename kobject and sysfs_dirent */
@@ -934,6 +963,8 @@ int sysfs_rename_dir(struct kobject * ko
 
 	dup_name = sd->s_name;
 	sd->s_name = new_name;
+	if (sd->s_parent->s_flags & SYSFS_FLAG_TAGGED)
+		sd->s_tag.tag = tag;
 
 	/* rename */
 	list_for_each_entry(srs, &todo, list) {
@@ -941,6 +972,20 @@ int sysfs_rename_dir(struct kobject * ko
 		d_move(srs->old_dentry, srs->new_dentry);
 	}
 
+	/* If we are moving across superblocks drop the dcache entries */
+	if (old_tag != tag) {
+		struct super_block *sb;
+		struct dentry *dentry;
+		list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+			dentry = __sysfs_get_dentry(sb, sd);
+			if (!dentry)
+				continue;
+			shrink_dcache_parent(dentry);
+			d_drop(dentry);
+			dput(dentry);
+		}
+	}
+
 	error = 0;
 out_unlock:
 	mutex_unlock(&sysfs_mutex);
@@ -963,11 +1008,13 @@ int sysfs_move_dir(struct kobject *kobj,
 	struct sysfs_rename_struct *srs;
 	struct inode *old_parent_inode = NULL, *new_parent_inode = NULL;
 	int error;
+	const void *tag;
 
 	INIT_LIST_HEAD(&todo);
 	mutex_lock(&sysfs_rename_mutex);
 	BUG_ON(!sd->s_parent);
 	new_parent_sd = new_parent_kobj->sd ? new_parent_kobj->sd : &sysfs_root;
+	tag = sysfs_dirent_tag(sd);
 
 	error = 0;
 	if (sd->s_parent == new_parent_sd)
@@ -1001,7 +1048,7 @@ again:
 	mutex_lock(&sysfs_mutex);
 
 	error = -EEXIST;
-	if (sysfs_find_dirent(new_parent_sd, sd->s_name))
+	if (sysfs_find_dirent(new_parent_sd, tag, sd->s_name))
 		goto out_unlock;
 
 	error = 0;
@@ -1040,10 +1087,11 @@ static inline unsigned char dt_type(stru
 
 static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
-	struct dentry *dentry = filp->f_path.dentry;
-	struct sysfs_dirent * parent_sd = dentry->d_fsdata;
+	struct dentry *parent = filp->f_path.dentry;
+	struct sysfs_dirent *parent_sd = parent->d_fsdata;
 	struct sysfs_dirent *pos;
 	ino_t ino;
+	const void *tag;
 
 	if (filp->f_pos == 0) {
 		ino = parent_sd->s_ino;
@@ -1061,6 +1109,8 @@ static int sysfs_readdir(struct file * f
 	if ((filp->f_pos > 1) && (filp->f_pos < INT_MAX)) {
 		mutex_lock(&sysfs_mutex);
 
+		tag = sysfs_lookup_tag(parent_sd, parent->d_sb);
+
 		/* Skip the dentries we have already reported */
 		pos = parent_sd->s_dir.children;
 		while (pos && (filp->f_pos > pos->s_ino))
@@ -1070,6 +1120,10 @@ static int sysfs_readdir(struct file * f
 			const char * name;
 			int len;
 
+			if ((parent_sd->s_flags & SYSFS_FLAG_TAGGED) &&
+			    (pos->s_tag.tag != tag))
+				continue;
+
 			name = pos->s_name;
 			len = strlen(name);
 			filp->f_pos = ino = pos->s_ino;
@@ -1090,3 +1144,106 @@ const struct file_operations sysfs_dir_o
 	.read		= generic_read_dir,
 	.readdir	= sysfs_readdir,
 };
+
+const void *sysfs_creation_tag(struct sysfs_dirent *parent_sd,
+			       struct sysfs_dirent *sd)
+{
+	const void *tag = NULL;
+
+	if (parent_sd->s_flags & SYSFS_FLAG_TAGGED) {
+		struct kobject *kobj;
+		switch (sysfs_type(sd)) {
+		case SYSFS_DIR:
+			kobj = sd->s_dir.kobj;
+			break;
+		case SYSFS_KOBJ_LINK:
+			kobj = sd->s_symlink.target_sd->s_dir.kobj;
+			break;
+		default:
+			BUG();
+		}
+		tag = parent_sd->s_tag.ops->kobject_tag(kobj);
+	}
+	return tag;
+}
+
+const void *sysfs_removal_tag(struct kobject *kobj, struct sysfs_dirent *dir_sd)
+{
+	const void *tag = NULL;
+
+	if (dir_sd->s_flags & SYSFS_FLAG_TAGGED)
+		tag = kobj->sd->s_tag.tag;
+
+	return tag;
+}
+
+const void *sysfs_lookup_tag(struct sysfs_dirent *dir_sd,
+			     struct super_block *sb)
+{
+	const void *tag = NULL;
+
+	if (dir_sd->s_flags & SYSFS_FLAG_TAGGED)
+		tag = dir_sd->s_tag.ops->sb_tag(&sysfs_info(sb)->tag);
+
+	return tag;
+}
+
+const void *sysfs_dirent_tag(struct sysfs_dirent *sd)
+{
+	const void *tag = NULL;
+
+	if (sd->s_parent && (sd->s_parent->s_flags & SYSFS_FLAG_TAGGED))
+		tag = sd->s_tag.tag;
+
+	return tag;
+}
+
+/**
+ *	sysfs_enable_tagging - Automatically tag all of the children in a
+ *	directory.
+ *	@kobj:	object whose children should be filtered by tags
+ *
+ *	Once tagging has been enabled on a directory the contents
+ *	of the directory become dependent upon context captured when
+ *	sysfs was mounted.
+ *
+ *	tag_ops->sb_tag() returns the context for a given superblock.
+ *
+ *	tag_ops->kobject_tag() returns the context that a given kobj
+ *	resides in.
+ *
+ *	Using those methods the sysfs code on tagged directories
+ *	carefully stores the files so that when we lookup files
+ *	we get the proper answer for our context.
+ *
+ *	If the context of a kobject is changed it is expected that
+ *	the kobject will be renamed so the appopriate sysfs data structures
+ *	can be updated.
+ */
+int sysfs_enable_tagging(struct kobject *kobj,
+	const struct sysfs_tagged_dir_operations *tag_ops)
+{
+	struct sysfs_dirent *sd;
+	int err;
+
+	err = -ENOENT;
+	sd = kobj->sd;
+
+	mutex_lock(&sysfs_mutex);
+	err = -EINVAL;
+	/* We can only enable tagging on empty directories
+	 * where tagging is not already enabled, and
+	 * who are not subdirectories of directories where tagging is
+	 * enabled.
+	 */
+	if (!sd->s_dir.children && (sysfs_type(sd) == SYSFS_DIR) &&
+	    !(sd->s_flags & SYSFS_FLAG_TAGGED) &&
+	    sd->s_parent &&
+	    !(sd->s_parent->s_flags & SYSFS_FLAG_TAGGED)) {
+		err = 0;
+		sd->s_flags |= SYSFS_FLAG_TAGGED;
+		sd->s_tag.ops = tag_ops;
+	}
+	mutex_unlock(&sysfs_mutex);
+	return err;
+}
Index: linux-mm/fs/sysfs/file.c
===================================================================
--- linux-mm.orig/fs/sysfs/file.c
+++ linux-mm/fs/sysfs/file.c
@@ -460,9 +460,9 @@ void sysfs_notify(struct kobject *k, cha
 	mutex_lock(&sysfs_mutex);
 
 	if (sd && dir)
-		sd = sysfs_find_dirent(sd, dir);
+		sd = sysfs_find_dirent(sd, NULL, dir);
 	if (sd && attr)
-		sd = sysfs_find_dirent(sd, attr);
+		sd = sysfs_find_dirent(sd, NULL, attr);
 	if (sd) {
 		struct sysfs_open_dirent *od;
 
@@ -631,7 +631,7 @@ EXPORT_SYMBOL_GPL(sysfs_chmod_file);
 
 void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr)
 {
-	sysfs_hash_and_remove(kobj->sd, attr->name);
+	sysfs_hash_and_remove(kobj, kobj->sd, attr->name);
 }
 
 
@@ -651,7 +651,7 @@ void sysfs_remove_file_from_group(struct
 	else
 		dir_sd = sysfs_get(kobj->sd);
 	if (dir_sd) {
-		sysfs_hash_and_remove(dir_sd, attr->name);
+		sysfs_hash_and_remove(kobj, dir_sd, attr->name);
 		sysfs_put(dir_sd);
 	}
 }
Index: linux-mm/fs/sysfs/group.c
===================================================================
--- linux-mm.orig/fs/sysfs/group.c
+++ linux-mm/fs/sysfs/group.c
@@ -23,7 +23,7 @@ static void remove_files(struct sysfs_di
 	int i;
 
 	for (i = 0, attr = grp->attrs; *attr; i++, attr++)
-		sysfs_hash_and_remove(dir_sd, (*attr)->name);
+		sysfs_hash_and_remove(kobj, dir_sd, (*attr)->name);
 }
 
 static int create_files(struct sysfs_dirent *dir_sd, struct kobject *kobj,
@@ -39,7 +39,7 @@ static int create_files(struct sysfs_dir
 		 * visibility.  Do this by first removing then
 		 * re-adding (if required) the file */
 		if (update)
-			sysfs_hash_and_remove(dir_sd, (*attr)->name);
+			sysfs_hash_and_remove(kobj, dir_sd, (*attr)->name);
 		if (grp->is_visible) {
 			mode = grp->is_visible(kobj, *attr, i);
 			if (!mode)
Index: linux-mm/fs/sysfs/inode.c
===================================================================
--- linux-mm.orig/fs/sysfs/inode.c
+++ linux-mm/fs/sysfs/inode.c
@@ -217,17 +217,20 @@ struct inode * sysfs_get_inode(struct sy
 	return inode;
 }
 
-int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name)
+int sysfs_hash_and_remove(struct kobject *kobj, struct sysfs_dirent *dir_sd,
+			  const char *name)
 {
 	struct sysfs_addrm_cxt acxt;
 	struct sysfs_dirent *sd;
+	const void *tag;
 
 	if (!dir_sd)
 		return -ENOENT;
 
 	sysfs_addrm_start(&acxt, dir_sd);
+	tag = sysfs_removal_tag(kobj, dir_sd);
 
-	sd = sysfs_find_dirent(dir_sd, name);
+	sd = sysfs_find_dirent(dir_sd, tag, name);
 	if (sd)
 		sysfs_remove_one(&acxt, sd);
 
Index: linux-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/fs/sysfs/mount.c
@@ -75,6 +75,7 @@ static int sysfs_fill_super(struct super
 		goto out_err;
 	}
 	root->d_fsdata = &sysfs_root;
+	root->d_sb = sb;
 	sb->s_root = root;
 	sb->s_fs_info = info;
 	return 0;
@@ -88,20 +89,55 @@ out_err:
 	return error;
 }
 
+static int sysfs_test_super(struct super_block *sb, void *ptr)
+{
+	struct task_struct *task = ptr;
+	struct sysfs_super_info *info = sysfs_info(sb);
+	int found = 1;
+
+	return found;
+}
+
 static int sysfs_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
-	int rc;
+	struct super_block *sb;
+	int error;
 	mutex_lock(&sysfs_rename_mutex);
-	rc = get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+	sb = sget(fs_type, sysfs_test_super, set_anon_super, current);
+	if (IS_ERR(sb)) {
+		error = PTR_ERR(sb);
+		goto out;
+	}
+	if (!sb->s_root) {
+		sb->s_flags = flags;
+		error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
+		if (error) {
+			up_write(&sb->s_umount);
+			deactivate_super(sb);
+			goto out;
+		}
+		sb->s_flags |= MS_ACTIVE;
+	}
+	do_remount_sb(sb, flags, data, 0);
+	error = simple_set_mnt(mnt, sb);
+out:
 	mutex_unlock(&sysfs_rename_mutex);
-	return rc;
+	return error;
+}
+
+static void sysfs_kill_sb(struct super_block *sb)
+{
+	struct sysfs_super_info *info = sysfs_info(sb);
+
+	kill_anon_super(sb);
+	kfree(info);
 }
 
 struct file_system_type sysfs_fs_type = {
 	.name		= "sysfs",
 	.get_sb		= sysfs_get_sb,
-	.kill_sb	= kill_anon_super,
+	.kill_sb	= sysfs_kill_sb,
 };
 
 void sysfs_grab_supers(void)
Index: linux-mm/fs/sysfs/symlink.c
===================================================================
--- linux-mm.orig/fs/sysfs/symlink.c
+++ linux-mm/fs/sysfs/symlink.c
@@ -94,7 +94,7 @@ void sysfs_remove_link(struct kobject * 
 	else
 		parent_sd = kobj->sd;
 
-	sysfs_hash_and_remove(parent_sd, name);
+	sysfs_hash_and_remove(kobj, parent_sd, name);
 }
 
 static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
Index: linux-mm/fs/sysfs/sysfs.h
===================================================================
--- linux-mm.orig/fs/sysfs/sysfs.h
+++ linux-mm/fs/sysfs/sysfs.h
@@ -46,6 +46,10 @@ struct sysfs_dirent {
 	const char		*s_name;
 
 	union {
+		const struct sysfs_tagged_dir_operations	*ops;
+		const void 					*tag;
+	} s_tag;
+	union {
 		struct sysfs_elem_dir		s_dir;
 		struct sysfs_elem_symlink	s_symlink;
 		struct sysfs_elem_attr		s_attr;
@@ -69,6 +73,7 @@ struct sysfs_dirent {
 
 #define SYSFS_FLAG_MASK			~SYSFS_TYPE_MASK
 #define SYSFS_FLAG_REMOVED		0x0200
+#define SYSFS_FLAG_TAGGED		0x0400
 
 static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
 {
@@ -87,6 +92,7 @@ struct sysfs_addrm_cxt {
 
 struct sysfs_super_info {
 	int	grabbed;
+	struct sysfs_tag_info tag;
 };
 
 #define sysfs_info(SB) ((struct sysfs_super_info *)(SB)->s_fs_info)
@@ -113,6 +119,13 @@ extern spinlock_t sysfs_assoc_lock;
 extern const struct file_operations sysfs_dir_operations;
 extern const struct inode_operations sysfs_dir_inode_operations;
 
+extern const void *sysfs_creation_tag(struct sysfs_dirent *parent_sd,
+				      struct sysfs_dirent *sd);
+extern const void *sysfs_removal_tag(struct kobject *kobj,
+				     struct sysfs_dirent *dir_sd);
+extern const void *sysfs_lookup_tag(struct sysfs_dirent *dir_sd,
+				    struct super_block *sb);
+extern const void *sysfs_dirent_tag(struct sysfs_dirent *sd);
 struct dentry *sysfs_get_dentry(struct super_block *sb,
 				struct sysfs_dirent *sd);
 struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd);
@@ -124,6 +137,7 @@ void sysfs_remove_one(struct sysfs_addrm
 void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt);
 
 struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
+				       const void *tag,
 				       const unsigned char *name);
 struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
 				      const unsigned char *name);
@@ -155,7 +169,8 @@ static inline void sysfs_put(struct sysf
  */
 struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
 int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
-int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
+int sysfs_hash_and_remove(struct kobject *kobj, struct sysfs_dirent *dir_sd,
+			  const char *name);
 int sysfs_inode_init(void);
 
 /*
Index: linux-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/include/linux/sysfs.h
@@ -78,6 +78,14 @@ struct sysfs_ops {
 	ssize_t	(*store)(struct kobject *,struct attribute *,const char *, size_t);
 };
 
+struct sysfs_tag_info {
+};
+
+struct sysfs_tagged_dir_operations {
+	const void *(*sb_tag)(struct sysfs_tag_info *info);
+	const void *(*kobject_tag)(struct kobject *kobj);
+};
+
 #ifdef CONFIG_SYSFS
 
 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
@@ -117,6 +125,9 @@ void sysfs_remove_file_from_group(struct
 void sysfs_notify(struct kobject *kobj, char *dir, char *attr);
 void sysfs_printk_last_file(void);
 
+int sysfs_enable_tagging(struct kobject *,
+			 const struct sysfs_tagged_dir_operations *);
+
 extern int __must_check sysfs_init(void);
 
 #else /* CONFIG_SYSFS */
@@ -213,6 +224,12 @@ static inline void sysfs_notify(struct k
 {
 }
 
+static inline int sysfs_enable_tagging(struct kobject *kobj,
+		       const struct sysfs_tagged_dir_operations *tag_ops)
+{
+	return 0;
+}
+
 static inline int __must_check sysfs_init(void)
 {
 	return 0;

-- 

[PATCH 07/10] sysfs: Implement sysfs_delete_link and sysfs_rename_link

[Benjamin Thery]

sysfs: Implement sysfs_delete_link and sysfs_rename_link

When removing a symlink sysfs_remove_link does not provide
enough information to figure out which tagged directory the symlink
falls in.  So I need sysfs_delete_link which is passed the target
of the symlink to delete.

Further half the time when we are removing a symlink the code is
actually renaming the symlink but not doing so explicitly because
we don't have a symlink rename method. So I have added sysfs_rename_link
as well.

Both of these functions now have enough information to find a symlink
in a tagged directory.  The only restriction is that they must be called
before the target kobject is renamed or deleted.  If they are called
later I loose track of which tag the target kobject was marked with
and can no longer find the old symlink to remove it.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/symlink.c    |   31 +++++++++++++++++++++++++++++++
 include/linux/sysfs.h |   17 +++++++++++++++++
 2 files changed, 48 insertions(+)

Index: linux-mm/fs/sysfs/symlink.c
===================================================================
--- linux-mm.orig/fs/sysfs/symlink.c
+++ linux-mm/fs/sysfs/symlink.c
@@ -80,6 +80,21 @@ int sysfs_create_link(struct kobject * k
 }
 
 /**
+ *	sysfs_delete_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@name:	name of the symlink to remove.
+ *
+ *	Unlike sysfs_remove_link sysfs_delete_link has enough information
+ *	to successfully delete symlinks in tagged directories.
+ */
+void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
+			const char *name)
+{
+	sysfs_hash_and_remove(targ, kobj->sd, name);
+}
+
+/**
  *	sysfs_remove_link - remove symlink in object's directory.
  *	@kobj:	object we're acting for.
  *	@name:	name of the symlink to remove.
@@ -97,6 +112,22 @@ void sysfs_remove_link(struct kobject * 
 	sysfs_hash_and_remove(kobj, parent_sd, name);
 }
 
+/**
+ *	sysfs_rename_link - rename symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@old:	previous name of the symlink.
+ *	@new:	new name of the symlink.
+ *
+ *	A helper function for the common rename symlink idiom.
+ */
+int sysfs_rename_link(struct kobject *kobj, struct kobject *targ,
+			const char *old, const char *new)
+{
+	sysfs_delete_link(kobj, targ, old);
+	return sysfs_create_link(kobj, targ, new);
+}
+
 static int sysfs_get_target_path(struct sysfs_dirent *parent_sd,
 				 struct sysfs_dirent *target_sd, char *path)
 {
Index: linux-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/include/linux/sysfs.h
@@ -111,6 +111,12 @@ int __must_check sysfs_create_link(struc
 				   const char *name);
 void sysfs_remove_link(struct kobject *kobj, const char *name);
 
+int sysfs_rename_link(struct kobject *kobj, struct kobject *target,
+			const char *old_name, const char *new_name);
+
+void sysfs_delete_link(struct kobject *dir, struct kobject *targ,
+			const char *name);
+
 int __must_check sysfs_create_group(struct kobject *kobj,
 				    const struct attribute_group *grp);
 int sysfs_update_group(struct kobject *kobj,
@@ -192,6 +198,17 @@ static inline void sysfs_remove_link(str
 {
 }
 
+static inline int sysfs_rename_link(struct kobject *k, struct kobject *t,
+				    const char *old_name, const char *new_name)
+{
+	return 0;
+}
+
+static inline void sysfs_delete_link(struct kobject *k, struct kobject *t,
+				     const char *name)
+{
+}
+
 static inline int sysfs_create_group(struct kobject *kobj,
 				     const struct attribute_group *grp)
 {

-- 

[PATCH 08/10] driver core: Implement tagged directory support for device classes.

[Benjamin Thery]

driver core: Implement tagged directory support for device classes.

This patch enables tagging on every class directory if struct class
has tag_ops.

In addition device_del and device_rename were modified to use
sysfs_delete_link and sysfs_rename_link respectively to ensure
when these operations happen on devices whose classes have
tag_ops that they work properly.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 drivers/base/class.c   |   30 ++++++++++++++++++++++++++----
 drivers/base/core.c    |   41 ++++++++++++++++++++++-------------------
 include/linux/device.h |    2 ++
 3 files changed, 50 insertions(+), 23 deletions(-)

Index: linux-mm/drivers/base/class.c
===================================================================
--- linux-mm.orig/drivers/base/class.c
+++ linux-mm/drivers/base/class.c
@@ -134,6 +134,17 @@ static void remove_class_attrs(struct cl
 	}
 }
 
+static int class_setup_tagging(struct class *cls)
+{
+	const struct sysfs_tagged_dir_operations *tag_ops;
+
+	tag_ops = cls->tag_ops;
+	if (!tag_ops)
+		return 0;
+
+	return sysfs_enable_tagging(&cls->subsys.kobj, tag_ops);
+}
+
 int class_register(struct class *cls)
 {
 	int error;
@@ -162,11 +173,22 @@ int class_register(struct class *cls)
 	cls->subsys.kobj.ktype = &class_ktype;
 
 	error = kset_register(&cls->subsys);
-	if (!error) {
-		error = add_class_attrs(class_get(cls));
-		class_put(cls);
-	}
+	if (error)
+		goto out;
+
+	error = class_setup_tagging(cls);
+	if (error)
+		goto out_unregister;
+
+	error = add_class_attrs(cls);
+	if (error)
+		goto out_unregister;
+
+out:
 	return error;
+out_unregister:
+	kset_unregister(&cls->subsys);
+	goto out;
 }
 
 void class_unregister(struct class *cls)
Index: linux-mm/drivers/base/core.c
===================================================================
--- linux-mm.orig/drivers/base/core.c
+++ linux-mm/drivers/base/core.c
@@ -617,6 +617,10 @@ static struct kobject *get_device_parent
 			kobject_put(k);
 			return NULL;
 		}
+		/* If we created a new class-directory setup tagging */
+		if (dev->class->tag_ops)
+			sysfs_enable_tagging(k, dev->class->tag_ops);
+
 		/* do not emit an uevent for this simple "glue" directory */
 		return k;
 	}
@@ -751,12 +755,13 @@ static void device_remove_class_symlinks
 
 	if (dev->kobj.parent != &dev->class->subsys.kobj &&
 	    device_is_not_partition(dev))
-		sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
+		sysfs_delete_link(&dev->class->subsys.kobj, &dev->kobj,
+				  dev->bus_id);
 #else
 	if (dev->parent && device_is_not_partition(dev))
 		sysfs_remove_link(&dev->kobj, "device");
 
-	sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id);
+	sysfs_delete_link(&dev->class->subsys.kobj, &dev->kobj, dev->bus_id);
 #endif
 
 	sysfs_remove_link(&dev->kobj, "subsystem");
@@ -1282,6 +1287,15 @@ int device_rename(struct device *dev, ch
 	strlcpy(old_device_name, dev->bus_id, BUS_ID_SIZE);
 	strlcpy(dev->bus_id, new_name, BUS_ID_SIZE);
 
+#ifndef CONFIG_SYSFS_DEPRECATED
+	if (dev->class && (dev->kobj.parent != &dev->class->subsys.kobj)) {
+		error = sysfs_rename_link(&dev->class->subsys.kobj,
+			&dev->kobj, old_device_name, new_name);
+		if (error)
+			goto out;
+	}
+#endif
+
 	error = kobject_rename(&dev->kobj, new_name);
 	if (error) {
 		strlcpy(dev->bus_id, old_device_name, BUS_ID_SIZE);
@@ -1290,24 +1304,13 @@ int device_rename(struct device *dev, ch
 
 #ifdef CONFIG_SYSFS_DEPRECATED
 	if (old_class_name) {
+		error = -ENOMEM;
 		new_class_name = make_class_name(dev->class->name, &dev->kobj);
-		if (new_class_name) {
-			error = sysfs_create_link(&dev->parent->kobj,
-						  &dev->kobj, new_class_name);
-			if (error)
-				goto out;
-			sysfs_remove_link(&dev->parent->kobj, old_class_name);
-		}
-	}
-#else
-	if (dev->class) {
-		sysfs_remove_link(&dev->class->subsys.kobj, old_device_name);
-		error = sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj,
-					  dev->bus_id);
-		if (error) {
-			dev_err(dev, "%s: sysfs_create_symlink failed (%d)\n",
-				__func__, error);
-		}
+		if (new_class_name)
+			error = sysfs_rename_link(&dev->parent->kobj,
+						  &dev->kobj,
+						  old_class_name,
+						  new_class_name);
 	}
 #endif
 
Index: linux-mm/include/linux/device.h
===================================================================
--- linux-mm.orig/include/linux/device.h
+++ linux-mm/include/linux/device.h
@@ -199,6 +199,8 @@ struct class {
 	int (*suspend)(struct device *dev, pm_message_t state);
 	int (*resume)(struct device *dev);
 
+	const struct sysfs_tagged_dir_operations *tag_ops;
+
 	struct pm_ops *pm;
 };
 

-- 

[PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Benjamin Thery]

net: Enable tagging for net_class directories in sysfs

The problem.  Network devices show up in sysfs and with the network
namespace active multiple devices with the same name can show up in
the same directory, ouch!

To avoid that problem and allow existing applications in network namespaces
to see the same interface that is currently presented in sysfs, this
patch enables the tagging directory support in sysfs.

By using the network namespace pointers as tags to separate out the
the sysfs directory entries we ensure that we don't have conflicts
in the directories and applications only see a limited set of
the network devices.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/mount.c      |   36 ++++++++++++++++++++++++++++++++++++
 include/linux/sysfs.h |    2 ++
 net/Kconfig           |    2 +-
 net/core/net-sysfs.c  |   20 ++++++++++++++++++++
 4 files changed, 59 insertions(+), 1 deletion(-)

Index: linux-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/fs/sysfs/mount.c
@@ -16,6 +16,8 @@
 #include <linux/mount.h>
 #include <linux/pagemap.h>
 #include <linux/init.h>
+#include <linux/nsproxy.h>
+#include <net/net_namespace.h>
 
 #include "sysfs.h"
 
@@ -78,6 +80,7 @@ static int sysfs_fill_super(struct super
 	root->d_sb = sb;
 	sb->s_root = root;
 	sb->s_fs_info = info;
+	info->tag.net_ns = hold_net(current->nsproxy->net_ns);
 	return 0;
 
 out_err:
@@ -95,6 +98,9 @@ static int sysfs_test_super(struct super
 	struct sysfs_super_info *info = sysfs_info(sb);
 	int found = 1;
 
+	if (task->nsproxy->net_ns != info->tag.net_ns)
+		found = 0;
+
 	return found;
 }
 
@@ -131,6 +137,8 @@ static void sysfs_kill_sb(struct super_b
 	struct sysfs_super_info *info = sysfs_info(sb);
 
 	kill_anon_super(sb);
+	if (info->tag.net_ns)
+		release_net(info->tag.net_ns);
 	kfree(info);
 }
 
@@ -181,6 +189,31 @@ restart:
 	spin_unlock(&sb_lock);
 }
 
+#ifdef CONFIG_NET
+static void sysfs_net_exit(struct net *net)
+{
+	/* Allow the net namespace to go away while sysfs is still mounted. */
+	struct super_block *sb;
+	mutex_lock(&sysfs_rename_mutex);
+	sysfs_grab_supers();
+	mutex_lock(&sysfs_mutex);
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		struct sysfs_super_info *info = sysfs_info(sb);
+		if (info->tag.net_ns != net)
+			continue;
+		release_net(info->tag.net_ns);
+		info->tag.net_ns = NULL;
+	}
+	mutex_unlock(&sysfs_mutex);
+	sysfs_release_supers();
+	mutex_unlock(&sysfs_rename_mutex);
+}
+
+static struct pernet_operations sysfs_net_ops = {
+	.exit = sysfs_net_exit,
+};
+#endif
+
 int __init sysfs_init(void)
 {
 	int err = -ENOMEM;
@@ -205,6 +238,9 @@ int __init sysfs_init(void)
 			unregister_filesystem(&sysfs_fs_type);
 			goto out_err;
 		}
+#ifdef CONFIG_NET
+		register_pernet_subsys(&sysfs_net_ops);
+#endif
 	} else
 		goto out_err;
 out:
Index: linux-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/include/linux/sysfs.h
@@ -19,6 +19,7 @@
 
 struct kobject;
 struct module;
+struct net;
 
 /* FIXME
  * The *owner field is no longer used, but leave around
@@ -79,6 +80,7 @@ struct sysfs_ops {
 };
 
 struct sysfs_tag_info {
+	struct net *net_ns;
 };
 
 struct sysfs_tagged_dir_operations {
Index: linux-mm/net/Kconfig
===================================================================
--- linux-mm.orig/net/Kconfig
+++ linux-mm/net/Kconfig
@@ -30,7 +30,7 @@ menu "Networking options"
 config NET_NS
 	bool "Network namespace support"
 	default n
-	depends on EXPERIMENTAL && !SYSFS && NAMESPACES
+	depends on EXPERIMENTAL && NAMESPACES
 	help
 	  Allow user space to create what appear to be multiple instances
 	  of the network stack.
Index: linux-mm/net/core/net-sysfs.c
===================================================================
--- linux-mm.orig/net/core/net-sysfs.c
+++ linux-mm/net/core/net-sysfs.c
@@ -13,7 +13,9 @@
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
 #include <linux/if_arp.h>
+#include <linux/nsproxy.h>
 #include <net/sock.h>
+#include <net/net_namespace.h>
 #include <linux/rtnetlink.h>
 #include <linux/wireless.h>
 #include <net/iw_handler.h>
@@ -421,6 +423,23 @@ static void netdev_release(struct device
 	kfree((char *)dev - dev->padded);
 }
 
+static const void *net_sb_tag(struct sysfs_tag_info *info)
+{
+	return info->net_ns;
+}
+
+static const void *net_kobject_tag(struct kobject *kobj)
+{
+	struct net_device *dev;
+	dev = container_of(kobj, struct net_device, dev.kobj);
+	return dev_net(dev);
+}
+
+static const struct sysfs_tagged_dir_operations net_tagged_dir_operations = {
+	.sb_tag = net_sb_tag,
+	.kobject_tag = net_kobject_tag,
+};
+
 static struct class net_class = {
 	.name = "net",
 	.dev_release = netdev_release,
@@ -430,6 +449,7 @@ static struct class net_class = {
 #ifdef CONFIG_HOTPLUG
 	.dev_uevent = netdev_uevent,
 #endif
+	.tag_ops = &net_tagged_dir_operations,
 };
 
 /* Delete sysfs entries but hold kobject reference until after all

-- 

Re: [PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Greg KH]

On Mon, Jun 02, 2008 at 03:46:08PM +0200, Benjamin Thery wrote:
> net: Enable tagging for net_class directories in sysfs
> 
> The problem.  Network devices show up in sysfs and with the network
> namespace active multiple devices with the same name can show up in
> the same directory, ouch!
> 
> To avoid that problem and allow existing applications in network namespaces
> to see the same interface that is currently presented in sysfs, this
> patch enables the tagging directory support in sysfs.
> 
> By using the network namespace pointers as tags to separate out the
> the sysfs directory entries we ensure that we don't have conflicts
> in the directories and applications only see a limited set of
> the network devices.

I don't like it how the network subsystem is starting to leach into the
sysfs core here.  What happens when the next subsystem wants to do the
same thing?  And then the next one?  Will they all have to do this kind
of intrusive changes to sysfs?

Can't this be done only in the network subsystem?

thanks,

greg k-h

Re: [PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Serge E. Hallyn]

Quoting Greg KH (gregkh@suse.de):
> On Mon, Jun 02, 2008 at 03:46:08PM +0200, Benjamin Thery wrote:
> > net: Enable tagging for net_class directories in sysfs
> > 
> > The problem.  Network devices show up in sysfs and with the network
> > namespace active multiple devices with the same name can show up in
> > the same directory, ouch!
> > 
> > To avoid that problem and allow existing applications in network namespaces
> > to see the same interface that is currently presented in sysfs, this
> > patch enables the tagging directory support in sysfs.
> > 
> > By using the network namespace pointers as tags to separate out the
> > the sysfs directory entries we ensure that we don't have conflicts
> > in the directories and applications only see a limited set of
> > the network devices.
> 
> I don't like it how the network subsystem is starting to leach into the
> sysfs core here.  What happens when the next subsystem wants to do the
> same thing?  And then the next one?  Will they all have to do this kind
> of intrusive changes to sysfs?

At least as far as the tagging goes, each namespace which needs to do
this (network, devices, and user, at least) will add a field to the
tag structure and call sysfs_enable_tagging() on the relevant
directories.  So no more core sysfs changes should be needed, as Eric
tried to make this generic enough to be generally useful.

> Can't this be done only in the network subsystem?

sysfs/kobject layer has to somehow decide what to show for
/sys/class/net contents based on the mountpoint, right, so I don't see
how the network subsystem could do it.

The only non-tagging alternative I'd see would be to keep entirely
separate kobject pools for each namespace.  To do that we'd probably
want to break /sys/class/net into a separate fs that can be
remounted, so at least we don't have to keep the rest of the kobject
pools (/sys/firmware, kernel, etc) in sync...

Eric had mentioned before breaking /sys into multiple mountpoints, so
I'll assume the fact that he implemented tagging means that there was
too much cross-linking and whatnot across the /sys tree to make that
feasible.

More importantly, that approach would require more core sysfs changes
for the next namespace, whereas the tagging approach does not!

thanks,
-serge

Re: [PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Benjamin Thery]

Greg KH wrote:
> On Mon, Jun 02, 2008 at 03:46:08PM +0200, Benjamin Thery wrote:
>> net: Enable tagging for net_class directories in sysfs
>>
>> The problem.  Network devices show up in sysfs and with the network
>> namespace active multiple devices with the same name can show up in
>> the same directory, ouch!
>>
>> To avoid that problem and allow existing applications in network namespaces
>> to see the same interface that is currently presented in sysfs, this
>> patch enables the tagging directory support in sysfs.
>>
>> By using the network namespace pointers as tags to separate out the
>> the sysfs directory entries we ensure that we don't have conflicts
>> in the directories and applications only see a limited set of
>> the network devices.
> 
> I don't like it how the network subsystem is starting to leach into the
> sysfs core here.  What happens when the next subsystem wants to do the
> same thing?  And then the next one?  Will they all have to do this kind
> of intrusive changes to sysfs?
 >
 > Can't this be done only in the network subsystem?

I'm not sure to understand exactly what you mean.

What you don't like is seeing these hunks of network code in
fs/sysfs/mount.c? And you prefer to see these bits of code resides in
the network subsystem instead and see only "generic" sysfs services in
fs/sysfs/mount.c?

If this is it, I have some idea to implement a less intrusive
sysfs_net_exit(), which can be shared with the other namespaces.
Serge introduces the same kind of changes in patch 10 to fix an issue in 
  user namespace. I think we can share a bit of code and move the parts
specific to each namespace in their own subsystems.

Benjamin

> 
> thanks,
> 
> greg k-h
> 
> 


-- 
B e n j a m i n   T h e r y  - BULL/DT/Open Software R&D

    http://www.bull.com

Re: [PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Greg KH]

On Tue, Jun 03, 2008 at 05:24:21PM +0200, Benjamin Thery wrote:
> Greg KH wrote:
>> On Mon, Jun 02, 2008 at 03:46:08PM +0200, Benjamin Thery wrote:
>>> net: Enable tagging for net_class directories in sysfs
>>>
>>> The problem.  Network devices show up in sysfs and with the network
>>> namespace active multiple devices with the same name can show up in
>>> the same directory, ouch!
>>>
>>> To avoid that problem and allow existing applications in network 
>>> namespaces
>>> to see the same interface that is currently presented in sysfs, this
>>> patch enables the tagging directory support in sysfs.
>>>
>>> By using the network namespace pointers as tags to separate out the
>>> the sysfs directory entries we ensure that we don't have conflicts
>>> in the directories and applications only see a limited set of
>>> the network devices.
>> I don't like it how the network subsystem is starting to leach into the
>> sysfs core here.  What happens when the next subsystem wants to do the
>> same thing?  And then the next one?  Will they all have to do this kind
>> of intrusive changes to sysfs?
> >
> > Can't this be done only in the network subsystem?
>
> I'm not sure to understand exactly what you mean.
>
> What you don't like is seeing these hunks of network code in
> fs/sysfs/mount.c? And you prefer to see these bits of code resides in
> the network subsystem instead and see only "generic" sysfs services in
> fs/sysfs/mount.c?

Yes, exactly.

I don't want the problem that if more subsystems want to implement
something like this, they too need to modify the sysfs core.

And the mess with the #ifdef, that's not nice either :)

> If this is it, I have some idea to implement a less intrusive
> sysfs_net_exit(), which can be shared with the other namespaces.
> Serge introduces the same kind of changes in patch 10 to fix an issue in  
> user namespace. I think we can share a bit of code and move the parts
> specific to each namespace in their own subsystems.

I think that would be a good idea.  Care to redo the series?

thanks,

greg k-h

Re: [PATCH 09/10] netns: Enable tagging for net_class directories in sysfs

[Benjamin Thery]

Quoting Greg KH <gregkh@suse.de>:

> On Tue, Jun 03, 2008 at 05:24:21PM +0200, Benjamin Thery wrote:
>> Greg KH wrote:
>>> On Mon, Jun 02, 2008 at 03:46:08PM +0200, Benjamin Thery wrote:
>>>> net: Enable tagging for net_class directories in sysfs
>>>>
>>>> The problem.  Network devices show up in sysfs and with the network
>>>> namespace active multiple devices with the same name can show up in
>>>> the same directory, ouch!
>>>>
>>>> To avoid that problem and allow existing applications in network
>>>> namespaces
>>>> to see the same interface that is currently presented in sysfs, this
>>>> patch enables the tagging directory support in sysfs.
>>>>
>>>> By using the network namespace pointers as tags to separate out the
>>>> the sysfs directory entries we ensure that we don't have conflicts
>>>> in the directories and applications only see a limited set of
>>>> the network devices.
>>> I don't like it how the network subsystem is starting to leach into the
>>> sysfs core here.  What happens when the next subsystem wants to do the
>>> same thing?  And then the next one?  Will they all have to do this kind
>>> of intrusive changes to sysfs?
>> >
>> > Can't this be done only in the network subsystem?
>>
>> I'm not sure to understand exactly what you mean.
>>
>> What you don't like is seeing these hunks of network code in
>> fs/sysfs/mount.c? And you prefer to see these bits of code resides in
>> the network subsystem instead and see only "generic" sysfs services in
>> fs/sysfs/mount.c?
>
> Yes, exactly.
>
> I don't want the problem that if more subsystems want to implement
> something like this, they too need to modify the sysfs core.
>
> And the mess with the #ifdef, that's not nice either :)

OK. This is clear now :)

>> If this is it, I have some idea to implement a less intrusive
>> sysfs_net_exit(), which can be shared with the other namespaces.
>> Serge introduces the same kind of changes in patch 10 to fix an issue in
>> user namespace. I think we can share a bit of code and move the parts
>> specific to each namespace in their own subsystems.
>
> I think that would be a good idea.  Care to redo the series?

I'm already working on it.
I'll try to re-post in a couple of days.

Benjamin

>
> thanks,
>
> greg k-h
>
>



----------------------------------------------------------------
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[PATCH 10/10] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched

[Benjamin Thery]

Mark the /sys/kernel/uids directory to be tagged so that processes in
different user namespaces can remount /sys and see their own uid
listings.

Without this patch, having CONFIG_FAIR_SCHED=y makes user namespaces
unusable, because when you 
  clone(CLONE_NEWUSER)
it will auto-create the root userid and try to create
/sys/kernel/uids/0.  Since that already exists from the parent user
namespace, the create fails, and the clone misleadingly ends up
returning -ENOMEM.

This patch fixes the issue by allowing each user namespace to remount
/sys, and having /sys filter the /sys/kernel/uid/ entries by user
namespace.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/mount.c               |   24 ++++++++++++++++++++++++
 include/linux/sched.h          |    1 +
 include/linux/sysfs.h          |    9 +++++++++
 include/linux/user_namespace.h |    1 +
 kernel/user.c                  |   21 +++++++++++++++++++++
 kernel/user_namespace.c        |    3 ++-
 6 files changed, 58 insertions(+), 1 deletion(-)

Index: linux-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/fs/sysfs/mount.c
@@ -81,6 +81,7 @@ static int sysfs_fill_super(struct super
 	sb->s_root = root;
 	sb->s_fs_info = info;
 	info->tag.net_ns = hold_net(current->nsproxy->net_ns);
+	info->tag.user_ns = current->nsproxy->user_ns;
 	return 0;
 
 out_err:
@@ -100,6 +101,8 @@ static int sysfs_test_super(struct super
 
 	if (task->nsproxy->net_ns != info->tag.net_ns)
 		found = 0;
+	if (task->nsproxy->user_ns != info->tag.user_ns)
+		found = 0;
 
 	return found;
 }
@@ -214,6 +217,27 @@ static struct pernet_operations sysfs_ne
 };
 #endif
 
+#ifdef CONFIG_USER_NS
+void sysfs_userns_exit(struct user_namespace *user_ns)
+{
+	/* Allow the net namespace to go away while sysfs is still mounted. */
+	struct super_block *sb;
+	printk(KERN_NOTICE "sysfs: user namespace exiting\n");
+	mutex_lock(&sysfs_rename_mutex);
+	sysfs_grab_supers();
+	mutex_lock(&sysfs_mutex);
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		struct sysfs_super_info *info = sysfs_info(sb);
+		if (info->tag.user_ns != user_ns)
+			continue;
+		info->tag.user_ns = NULL;
+	}
+	mutex_unlock(&sysfs_mutex);
+	sysfs_release_supers();
+	mutex_unlock(&sysfs_rename_mutex);
+}
+#endif
+
 int __init sysfs_init(void)
 {
 	int err = -ENOMEM;
Index: linux-mm/include/linux/sched.h
===================================================================
--- linux-mm.orig/include/linux/sched.h
+++ linux-mm/include/linux/sched.h
@@ -600,6 +600,7 @@ struct user_struct {
 	/* Hash table maintenance information */
 	struct hlist_node uidhash_node;
 	uid_t uid;
+	struct user_namespace *user_ns;
 
 #ifdef CONFIG_USER_SCHED
 	struct task_group *tg;
Index: linux-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/include/linux/sysfs.h
@@ -20,6 +20,7 @@
 struct kobject;
 struct module;
 struct net;
+struct user_namespace;
 
 /* FIXME
  * The *owner field is no longer used, but leave around
@@ -81,6 +82,7 @@ struct sysfs_ops {
 
 struct sysfs_tag_info {
 	struct net *net_ns;
+	struct user_namespace *user_ns;
 };
 
 struct sysfs_tagged_dir_operations {
@@ -138,6 +140,9 @@ int sysfs_enable_tagging(struct kobject 
 
 extern int __must_check sysfs_init(void);
 
+struct user_namespace;
+void sysfs_userns_exit(struct user_namespace *user_ns);
+
 #else /* CONFIG_SYSFS */
 
 static inline int sysfs_schedule_callback(struct kobject *kobj,
@@ -254,6 +259,10 @@ static inline int __must_check sysfs_ini
 	return 0;
 }
 
+static inline void sysfs_userns_exit(struct user_namespace *user_ns)
+{
+}
+
 static inline void sysfs_printk_last_file(void)
 {
 }
Index: linux-mm/include/linux/user_namespace.h
===================================================================
--- linux-mm.orig/include/linux/user_namespace.h
+++ linux-mm/include/linux/user_namespace.h
@@ -12,6 +12,7 @@
 struct user_namespace {
 	struct kref		kref;
 	struct hlist_head	uidhash_table[UIDHASH_SZ];
+	struct kset		*kset;
 	struct user_struct	*root_user;
 };
 
Index: linux-mm/kernel/user.c
===================================================================
--- linux-mm.orig/kernel/user.c
+++ linux-mm/kernel/user.c
@@ -53,6 +53,7 @@ struct user_struct root_user = {
 	.files		= ATOMIC_INIT(0),
 	.sigpending	= ATOMIC_INIT(0),
 	.locked_shm     = 0,
+	.user_ns	= &init_user_ns,
 #ifdef CONFIG_USER_SCHED
 	.tg		= &init_task_group,
 #endif
@@ -236,6 +237,23 @@ static void uids_release(struct kobject 
 	return;
 }
 
+static const void *userns_sb_tag(struct sysfs_tag_info *info)
+{
+	return info->user_ns;
+}
+
+static const void *userns_kobject_tag(struct kobject *kobj)
+{
+	struct user_struct *up;
+	up = container_of(kobj, struct user_struct, kobj);
+	return up->user_ns;
+}
+
+static struct sysfs_tagged_dir_operations userns_tagged_dir_operations = {
+	.sb_tag = userns_sb_tag,
+	.kobject_tag = userns_kobject_tag,
+};
+
 static struct kobj_type uids_ktype = {
 	.sysfs_ops = &kobj_sysfs_ops,
 	.default_attrs = uids_attributes,
@@ -272,6 +290,8 @@ int __init uids_sysfs_init(void)
 	if (!uids_kset)
 		return -ENOMEM;
 
+	sysfs_enable_tagging(&uids_kset->kobj, &userns_tagged_dir_operations);
+
 	return uids_user_create(&root_user);
 }
 
@@ -404,6 +424,7 @@ struct user_struct *alloc_uid(struct use
 			goto out_unlock;
 
 		new->uid = uid;
+		new->user_ns = ns;
 		atomic_set(&new->__count, 1);
 
 		if (sched_create_user(new) < 0)
Index: linux-mm/kernel/user_namespace.c
===================================================================
--- linux-mm.orig/kernel/user_namespace.c
+++ linux-mm/kernel/user_namespace.c
@@ -22,7 +22,7 @@ static struct user_namespace *clone_user
 	struct user_struct *new_user;
 	int n;
 
-	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+	ns = kzalloc(sizeof(struct user_namespace), GFP_KERNEL);
 	if (!ns)
 		return ERR_PTR(-ENOMEM);
 
@@ -71,6 +71,7 @@ void free_user_ns(struct kref *kref)
 	struct user_namespace *ns;
 
 	ns = container_of(kref, struct user_namespace, kref);
+	sysfs_userns_exit(ns);
 	release_uids(ns);
 	kfree(ns);
 }

-- 

Re: [PATCH 10/10] sysfs: user namespaces: fix bug with clone(CLONE_NEWUSER) with fairsched

[Serge E. Hallyn]

Quoting Benjamin Thery (benjamin.thery@bull.net):
> Mark the /sys/kernel/uids directory to be tagged so that processes in
> different user namespaces can remount /sys and see their own uid
> listings.
> 
> Without this patch, having CONFIG_FAIR_SCHED=y makes user namespaces
> unusable, because when you 
>   clone(CLONE_NEWUSER)
> it will auto-create the root userid and try to create
> /sys/kernel/uids/0.  Since that already exists from the parent user
> namespace, the create fails, and the clone misleadingly ends up
> returning -ENOMEM.
> 
> This patch fixes the issue by allowing each user namespace to remount
> /sys, and having /sys filter the /sys/kernel/uid/ entries by user
> namespace.
> 
> Signed-off-by: Serge Hallyn <serue@us.ibm.com>
> Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>

Thanks for picking this up, Benjamin.

Eric, please look this one over.  I think I removed everything that
shouldn't be here from the last version, and at this point only
do what I need to to access the user_ns where we need it, and tag
the appropriate /sys/ files.

thanks,
-serge

> ---
>  fs/sysfs/mount.c               |   24 ++++++++++++++++++++++++
>  include/linux/sched.h          |    1 +
>  include/linux/sysfs.h          |    9 +++++++++
>  include/linux/user_namespace.h |    1 +
>  kernel/user.c                  |   21 +++++++++++++++++++++
>  kernel/user_namespace.c        |    3 ++-
>  6 files changed, 58 insertions(+), 1 deletion(-)
> 
> Index: linux-mm/fs/sysfs/mount.c
> ===================================================================
> --- linux-mm.orig/fs/sysfs/mount.c
> +++ linux-mm/fs/sysfs/mount.c
> @@ -81,6 +81,7 @@ static int sysfs_fill_super(struct super
>  	sb->s_root = root;
>  	sb->s_fs_info = info;
>  	info->tag.net_ns = hold_net(current->nsproxy->net_ns);
> +	info->tag.user_ns = current->nsproxy->user_ns;
>  	return 0;
> 
>  out_err:
> @@ -100,6 +101,8 @@ static int sysfs_test_super(struct super
> 
>  	if (task->nsproxy->net_ns != info->tag.net_ns)
>  		found = 0;
> +	if (task->nsproxy->user_ns != info->tag.user_ns)
> +		found = 0;
> 
>  	return found;
>  }
> @@ -214,6 +217,27 @@ static struct pernet_operations sysfs_ne
>  };
>  #endif
> 
> +#ifdef CONFIG_USER_NS
> +void sysfs_userns_exit(struct user_namespace *user_ns)
> +{
> +	/* Allow the net namespace to go away while sysfs is still mounted. */
> +	struct super_block *sb;
> +	printk(KERN_NOTICE "sysfs: user namespace exiting\n");
> +	mutex_lock(&sysfs_rename_mutex);
> +	sysfs_grab_supers();
> +	mutex_lock(&sysfs_mutex);
> +	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
> +		struct sysfs_super_info *info = sysfs_info(sb);
> +		if (info->tag.user_ns != user_ns)
> +			continue;
> +		info->tag.user_ns = NULL;
> +	}
> +	mutex_unlock(&sysfs_mutex);
> +	sysfs_release_supers();
> +	mutex_unlock(&sysfs_rename_mutex);
> +}
> +#endif
> +
>  int __init sysfs_init(void)
>  {
>  	int err = -ENOMEM;
> Index: linux-mm/include/linux/sched.h
> ===================================================================
> --- linux-mm.orig/include/linux/sched.h
> +++ linux-mm/include/linux/sched.h
> @@ -600,6 +600,7 @@ struct user_struct {
>  	/* Hash table maintenance information */
>  	struct hlist_node uidhash_node;
>  	uid_t uid;
> +	struct user_namespace *user_ns;
> 
>  #ifdef CONFIG_USER_SCHED
>  	struct task_group *tg;
> Index: linux-mm/include/linux/sysfs.h
> ===================================================================
> --- linux-mm.orig/include/linux/sysfs.h
> +++ linux-mm/include/linux/sysfs.h
> @@ -20,6 +20,7 @@
>  struct kobject;
>  struct module;
>  struct net;
> +struct user_namespace;
> 
>  /* FIXME
>   * The *owner field is no longer used, but leave around
> @@ -81,6 +82,7 @@ struct sysfs_ops {
> 
>  struct sysfs_tag_info {
>  	struct net *net_ns;
> +	struct user_namespace *user_ns;
>  };
> 
>  struct sysfs_tagged_dir_operations {
> @@ -138,6 +140,9 @@ int sysfs_enable_tagging(struct kobject 
> 
>  extern int __must_check sysfs_init(void);
> 
> +struct user_namespace;
> +void sysfs_userns_exit(struct user_namespace *user_ns);
> +
>  #else /* CONFIG_SYSFS */
> 
>  static inline int sysfs_schedule_callback(struct kobject *kobj,
> @@ -254,6 +259,10 @@ static inline int __must_check sysfs_ini
>  	return 0;
>  }
> 
> +static inline void sysfs_userns_exit(struct user_namespace *user_ns)
> +{
> +}
> +
>  static inline void sysfs_printk_last_file(void)
>  {
>  }
> Index: linux-mm/include/linux/user_namespace.h
> ===================================================================
> --- linux-mm.orig/include/linux/user_namespace.h
> +++ linux-mm/include/linux/user_namespace.h
> @@ -12,6 +12,7 @@
>  struct user_namespace {
>  	struct kref		kref;
>  	struct hlist_head	uidhash_table[UIDHASH_SZ];
> +	struct kset		*kset;
>  	struct user_struct	*root_user;
>  };
> 
> Index: linux-mm/kernel/user.c
> ===================================================================
> --- linux-mm.orig/kernel/user.c
> +++ linux-mm/kernel/user.c
> @@ -53,6 +53,7 @@ struct user_struct root_user = {
>  	.files		= ATOMIC_INIT(0),
>  	.sigpending	= ATOMIC_INIT(0),
>  	.locked_shm     = 0,
> +	.user_ns	= &init_user_ns,
>  #ifdef CONFIG_USER_SCHED
>  	.tg		= &init_task_group,
>  #endif
> @@ -236,6 +237,23 @@ static void uids_release(struct kobject 
>  	return;
>  }
> 
> +static const void *userns_sb_tag(struct sysfs_tag_info *info)
> +{
> +	return info->user_ns;
> +}
> +
> +static const void *userns_kobject_tag(struct kobject *kobj)
> +{
> +	struct user_struct *up;
> +	up = container_of(kobj, struct user_struct, kobj);
> +	return up->user_ns;
> +}
> +
> +static struct sysfs_tagged_dir_operations userns_tagged_dir_operations = {
> +	.sb_tag = userns_sb_tag,
> +	.kobject_tag = userns_kobject_tag,
> +};
> +
>  static struct kobj_type uids_ktype = {
>  	.sysfs_ops = &kobj_sysfs_ops,
>  	.default_attrs = uids_attributes,
> @@ -272,6 +290,8 @@ int __init uids_sysfs_init(void)
>  	if (!uids_kset)
>  		return -ENOMEM;
> 
> +	sysfs_enable_tagging(&uids_kset->kobj, &userns_tagged_dir_operations);
> +
>  	return uids_user_create(&root_user);
>  }
> 
> @@ -404,6 +424,7 @@ struct user_struct *alloc_uid(struct use
>  			goto out_unlock;
> 
>  		new->uid = uid;
> +		new->user_ns = ns;
>  		atomic_set(&new->__count, 1);
> 
>  		if (sched_create_user(new) < 0)
> Index: linux-mm/kernel/user_namespace.c
> ===================================================================
> --- linux-mm.orig/kernel/user_namespace.c
> +++ linux-mm/kernel/user_namespace.c
> @@ -22,7 +22,7 @@ static struct user_namespace *clone_user
>  	struct user_struct *new_user;
>  	int n;
> 
> -	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
> +	ns = kzalloc(sizeof(struct user_namespace), GFP_KERNEL);
>  	if (!ns)
>  		return ERR_PTR(-ENOMEM);
> 
> @@ -71,6 +71,7 @@ void free_user_ns(struct kref *kref)
>  	struct user_namespace *ns;
> 
>  	ns = container_of(kref, struct user_namespace, kref);
> +	sysfs_userns_exit(ns);
>  	release_uids(ns);
>  	kfree(ns);
>  }
> 
> -- 

Re: [PATCH 00/10] sysfs tagged directories V4

[Dan Smith]

[-- Attachment #1: Type: text/plain, Size: 498 bytes --]

BT> Here is an updated version of Eric Biederman's patchset to
BT> implement tagged directories in sysfs ported on top of
BT> 2.6.26-rc2-mm1.

With this set applied, I am able to clone() with CLONE_NEWNET, get an
isolated netns, and move interfaces into that namespace.  This removes
the last barrier blocking the implementation of full containers (with
network isolation) in libvirt.

Thanks!

-- 
Dan Smith
IBM Linux Technology Center
Open Hypervisor Team
email: danms@us.ibm.com

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