Greg,

Here is an updated version of the sysfs tagged directories that improves
a bit the situation over the previous one. 

I've modified the patch 09 ("Enable tagging for net_class directories in 
sysfs") to be a bit less intrusive in sysfs core. I removed the #ifdef'd
parts you didn't like in fs/sysfs/mount.c, and replaced it by a generic 
routine sysfs_ns_exit() that is called, if needed, by the namespace when
it exits. This routine goes through every sysfs super blocks and calls 
the callback passed by the namespace to clean its tag.

The patch is now splitted in two: 
* 09/11: the generic routine,
* 10/11: the remaining network parts.

The generic part can be merge with patch 05 ("sysfs: Implement sysfs 
tagged directory support.") but I left it separate for now to ease 
reviews.

Serge's patch for user namespace is modified to use this new service too.
No more #ifdef CONFIG_NET or #ifdef CONFIG_USER_NS in fs/sysfs/mount.c 
now.


But, currently, a new namespace that wants to add its tag to sysfs dirs
still need to modify fs/sysfs/mount.c in a few routines to manage the
new tag member added in struct sysfs_tag_info: sysfs_fill_super(), 
sysfs_test_super(), sysfs_kill_sb() (see the last two patches).
These changes are only the initialization and a bunch of comparisons.

If we really want to go further, to get rid of these, I've thought 
about:

* Extending sysfs_tagged_dir_operations with super blocks operations: 
  - fill_sb_tag, test_sb_tag, kill_sb_tag

* Add routines in sysfs to allow registration/unregistration of these 
  operations structs in a list:
  - sysfs_register_tagged_dir_ops()...

* Each subsystem concerned implements and registers its operations at 
  boot.

* In sysfs_fill_super(), sysfs_test_super() and sysfs_kill_sb(), add 
  loops to go through all registered operations structs and calls the 
  corresponding operations if it's present.

But... I thought it was a bit overkill for the few namespaces that will 
actually need sysfs tagged directories.


(Below you'll find the traditional introduction for sysfs tagged dirs 
and the updated changelog)

Thanks,
Benjamin

--
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.

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
---------
* V5:
  - Make namespace tags a bit less intrusive in sysfs core:
    - New patch 09: Added a generic sysfs_ns_exit routine called by 
      exiting namespaces. A callback is passed to this routine to 
      execute the subsystem specific code.
    - Modified patches 09 and 10 (now 10 and 11) ("netns tagging" and 
      "userns tagging") to use this new routine instead of adding 
      #ifdef'd code in fs/sysfs/mount.c.
  - Added missing -ENOMEM in fs/sysfs/dir.c:prep_rename() (Roel Kluin)
* 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

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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

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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,

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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 |  195 ++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 137 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 +816,113 @@ 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) {
+			error = -ENOMEM;
+			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 +937,21 @@ 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 +960,12 @@ 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 +974,29 @@ 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 +1005,11 @@ 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 +1018,17 @@ 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;
 }

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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;
 }

-- 
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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)
 {

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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) {
@@ -895,19 +919,24 @@ 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);
@@ -920,7 +949,7 @@ 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 */
@@ -935,6 +964,8 @@ 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) {
@@ -942,6 +973,20 @@ 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);
@@ -964,11 +1009,13 @@ 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)
@@ -1002,7 +1049,7 @@ 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;
@@ -1041,10 +1088,11 @@ 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;
@@ -1062,6 +1110,8 @@ 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 a

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;
 };
 

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Add sysfs routine sysfs_ns_exit() to allow a namespace to go away while
sysfs is still mounted. 

The exiting namespace calls this routine and pass it a callback to be 
called for every sysfs superblocks present. The callback contains the 
necessary code to clean the superblock tag data associated with this 
namespace.

Signed-off-by: Benjamin Thery <benjamin.thery@bull.net>
---
 fs/sysfs/mount.c      |   21 +++++++++++++++++++++
 include/linux/sysfs.h |    8 ++++++++
 2 files changed, 29 insertions(+)

Index: linux-mm/fs/sysfs/mount.c
===================================================================
--- linux-mm.orig/fs/sysfs/mount.c
+++ linux-mm/fs/sysfs/mount.c
@@ -181,6 +181,27 @@ restart:
 	spin_unlock(&sb_lock);
 }
 
+/* Clean sysfs tags related to a given namespace when it exits */
+void sysfs_ns_exit(void (*func)(struct sysfs_tag_info *, void *), void *data)
+{
+	/* Allow the 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);
+		/* Call the cleaning routine provided by the namespace.
+		 * data is the current namespace id passed by the namespace.
+		 */
+		func(&info->tag, data);
+	}
+	mutex_unlock(&sysfs_mutex);
+	sysfs_release_supers();
+	mutex_unlock(&sysfs_rename_mutex);
+}
+
 int __init sysfs_init(void)
 {
 	int err = -ENOMEM;
Index: linux-mm/include/linux/sysfs.h
===================================================================
--- linux-mm.orig/include/linux/sysfs.h
+++ linux-mm/include/linux/sysfs.h
@@ -134,6 +134,9 @@ void sysfs_printk_last_file(void);
 int sysfs_enable_tagging(struct kobject *kobj,
 			 const struct sysfs_tagged_dir_operations *tag_ops);
 
+void sysfs_ns_exit(void (*func)(struct sysfs_tag_info *, void *),
+		   void *data);
+
 extern int __must_check sysfs_init(void);
 
 #else /* CONFIG_SYSFS */
@@ -247,6 +250,11 @@ static inline int sysfs_enable_tagging(s
 	return 0;
 }
 
+static inline void sysfs_ns_exit(void (*func)(struct sysfs_tag_info *, void *),
+				 void *data)
+{
+}
+
 static inline int __must_check sysfs_init(void)
 {
 	return 0;

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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               |    3 +++
 include/linux/sched.h          |    1 +
 include/linux/sysfs.h          |    2 ++
 include/linux/user_namespace.h |    1 +
 kernel/user.c                  |   21 +++++++++++++++++++++
 kernel/user_namespace.c        |   13 ++++++++++++-
 6 files changed, 40 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;
 }
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 {
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);
 
@@ -66,11 +66,22 @@ struct user_namespace * copy_user_ns(int
 	return new_ns;
 }
 
+/* clear sysfs tag when user namespace exits */
+static void sysfs_userns_exit(struct sysfs_tag_info *tag_info, void *data)
+{
+	struct user_namespace *ns = (struct user_namespace *)data;
+
+	if (tag_info->user_ns != ns)
+		return;
+	tag_info->user_ns = NULL;
+}
+
 void free_user_ns(struct kref *kref)
 {
 	struct user_namespace *ns;
 
 	ns = container_of(kref, struct user_namespace, kref);
+	sysfs_ns_exit(sysfs_userns_exit, ns);
 	release_uids(ns);
 	kfree(ns);
 }

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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;

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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      |    8 ++++++++
 include/linux/sysfs.h |    2 ++
 net/Kconfig           |    2 +-
 net/core/net-sysfs.c  |   45 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 56 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);
 }
 
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>
@@ -385,6 +387,28 @@ static struct attribute_group wireless_g
 };
 #endif
 
+/*
+ * sysfs: allow the net namespace to go away while sysfs is still mounted.
+ */
+static void net_sysfs_net_exit_cb(struct sysfs_tag_info *tag_info, void *data)
+{
+	struct net *net = (struct net *)data;
+
+	if (tag_info->net_ns != net)
+		return;
+	release_net(tag_info->net_ns);
+	tag_info->net_ns = NULL;
+}
+
+void net_sysfs_net_exit(struct net *net)
+{
+	sysfs_ns_exit(net_sysfs_net_exit_cb, net);
+}
+
+static struct pernet_operations net_sysfs_ops = {
+	.exit = net_sysfs_net_exit,
+};
+
 #endif /* CONFIG_SYSFS */
 
 #ifdef CONFIG_HOTPLUG
@@ -421,6 +445,23 @@ 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 +471,7 @@ 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
@@ -477,5 +519,8 @@ void netdev_initialize_kobject(struct ne
 
 int netdev_kobject_init(void)
 {
+#ifdef CONFIG_SYSFS
+	register_pernet_subsys(&net_sysfs_ops);
+#endif
 	return class_register(&net_class);
 }

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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>
> ---
>  fs/sysfs/mount.c               |    3 +++
>  include/linux/sched.h          |    1 +
>  include/linux/sysfs.h          |    2 ++
>  include/linux/user_namespace.h |    1 +
>  kernel/user.c                  |   21 +++++++++++++++++++++
>  kernel/user_namespace.c        |   13 ++++++++++++-
>  6 files changed, 40 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;
>  }
> 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 {
> 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;

Hmm, funky.  I don't know where this came from - or actually, I think it
survived from the second of 4 or 5 quick attempts to figure out where
to do the tagging for userns...

I don't think the kset should be here :)

Otherwise, looks good, thanks Benjamin.

-serge

>  	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);
> 
> @@ -66,11 +66,22 @@ struct user_namespace * copy_user_ns(int
>  	return new_ns;
>  }
> 
> +/* clear sysfs tag when user namespace exits */
> +static void sysfs_userns_exit(struct sysfs_tag_info *tag_info, void *data)
> +{
> +	struct user_namespace *ns = (struct user_namespace *)data;
> +
> +	if (tag_info->user_ns != ns)
> +		return;
> +	tag_info->user_ns = NULL;
> +}
> +
>  void free_user_ns(struct kref *kref)
>  {
>  	struct user_namespace *ns;
> 
>  	ns = container_of(kref, struct user_namespace, kref);
> +	sysfs_ns_exit(sysfs_userns_exit, ns);
>  	release_uids(ns);
>  	kfree(ns);
>  }
> 
> -- 
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Quoting Benjamin Thery (benjamin.thery@bull.net):
> Greg,
> 
> Here is an updated version of the sysfs tagged directories that improves
> a bit the situation over the previous one. 
> 
> I've modified the patch 09 ("Enable tagging for net_class directories in 
> sysfs") to be a bit less intrusive in sysfs core. I removed the #ifdef'd
> parts you didn't like in fs/sysfs/mount.c, and replaced it by a generic 
> routine sysfs_ns_exit() that is called, if needed, by the namespace when
> it exits. This routine goes through every sysfs super blocks and calls 
> the callback passed by the namespace to clean its tag.
> 
> The patch is now splitted in two: 
> * 09/11: the generic routine,
> * 10/11: the remaining network parts.
> 
> The generic part can be merge with patch 05 ("sysfs: Implement sysfs 
> tagged directory support.") but I left it separate for now to ease 
> reviews.

Thanks.  Not nearly as radical as I'd feared.

Greg, does this address your concern?  It stops the need to put any
non-braindead code (i.e. the _exit notifier stuff) in fs/sysfs/mount.c for
any new namespaces needing sysfs tagging, leaving only simple
comparison/assignments.

> Serge's patch for user namespace is modified to use this new service too.
> No more #ifdef CONFIG_NET or #ifdef CONFIG_USER_NS in fs/sysfs/mount.c 
> now.
> 
> 
> But, currently, a new namespace that wants to add its tag to sysfs dirs
> still need to modify fs/sysfs/mount.c in a few routines to manage the
> new tag member added in struct sysfs_tag_info: sysfs_fill_super(), 
> sysfs_test_super(), sysfs_kill_sb() (see the last two patches).
> These changes are only the initialization and a bunch of comparisons.
> 
> If we really want to go further, to get rid of these, I've thought 
> about:
> 
> * Extending sysfs_tagged_dir_operations with super blocks operations: 
>   - fill_sb_tag, test_sb_tag, kill_sb_tag
> 
> * Add routines in sysfs to allow registration/unregistration of these 
>   operations structs in a list:
>   - sysfs_register_tagged_dir_ops()...
> 
> * Each subsystem concerned implements and registers its operations at 
>   boot.
>
> * In sysfs_fill_super(), sysfs_test_super() and sysfs_kill_sb(), add 
>   loops to go through all registered operations structs and calls the 
>   corresponding operations if it's present.
> 
> But... I thought it was a bit overkill for the few namespaces that will 
> actually need sysfs tagged directories.

Agreed.  We expect device namespaces...  anything else?

thanks,
-serge
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On Tue, Jun 10, 2008 at 05:50:24PM -0500, Serge E. Hallyn wrote:
> Quoting Benjamin Thery (benjamin.thery@bull.net):
> > Greg,
> > 
> > Here is an updated version of the sysfs tagged directories that improves
> > a bit the situation over the previous one. 
> > 
> > I've modified the patch 09 ("Enable tagging for net_class directories in 
> > sysfs") to be a bit less intrusive in sysfs core. I removed the #ifdef'd
> > parts you didn't like in fs/sysfs/mount.c, and replaced it by a generic 
> > routine sysfs_ns_exit() that is called, if needed, by the namespace when
> > it exits. This routine goes through every sysfs super blocks and calls 
> > the callback passed by the namespace to clean its tag.
> > 
> > The patch is now splitted in two: 
> > * 09/11: the generic routine,
> > * 10/11: the remaining network parts.
> > 
> > The generic part can be merge with patch 05 ("sysfs: Implement sysfs 
> > tagged directory support.") but I left it separate for now to ease 
> > reviews.
> 
> Thanks.  Not nearly as radical as I'd feared.
> 
> Greg, does this address your concern?  It stops the need to put any
> non-braindead code (i.e. the _exit notifier stuff) in fs/sysfs/mount.c for
> any new namespaces needing sysfs tagging, leaving only simple
> comparison/assignments.

Sorry, I've been swamped with other things this week and haven't gotten
a chance to look this over.  Hopefully by the end of the week...  It's
in my queue though, don't worry it will not get lost.

thanks,

greg k-h
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Daniel Lezcano wrote:
> Tejun Heo wrote:
>> Hello,
>>
>> Daniel Lezcano wrote:
>>>> I think it would be great if sysfs_chmod_file can do all-or-nothing
>>>> instead of failing half way through but given the interface of
>>>> notify_change(), it could be difficult to implement.  Any ideas?
>>> Is it acceptable to queue the notifications in a list until we are in
>>> the loop and loop again to notify when exiting the first loop without
>>> error ?
>>
>> Can you please take a look at the following patch?
>>
>> http://article.gmane.org/gmane.linux.file-systems/24484
>>
>> Which replaces notify_change() call to two calls to sysfs_setattr() and
>> fsnotify_change().  The latter never fails and the former should always
>> succeed if inode_change_ok() succeeds (inode_setattr() never fails
>> unless the size is changing), so I think the correct thing to do is...
>>
>> * Separate out sysfs_do_setattr() which doesn't do inode_change_ok() and
>> just sets the attributes.  Making it a void function which triggers
>> WARN_ON() when inode_setattr() fails would be a good idea.
>>
>> * Implement sysfs_chmod_file() in similar way rename/move are
>> implemented - allocate all resources and check conditions and then iff
>> everything looks okay commit the operation by calling sysfs_do_setattr().
>>
>> How does that sound?
> 
> Does this patch looks like what you are describing ?

Yeah, something like that.  With looping for all the inodes added, it
looks like it will work fine.

Thanks.

-- 
tejun
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