[PATCH 35/39] sysfs, kernfs: make super_blocks bind to different kernfs_roots

Tejun Heo
2013-11-03T09:55:38Z

kernfs is being updated to allow multiple sysfs_dirent hierarchies so
that it can also be used by other users. Currently, sysfs
super_blocks are always attached to one kernfs_root - sysfs_root - and
distinguished only by their namespace tags.

This patch adds sysfs_super_info->root and update
sysfs_fill/test_super() so that super_blocks are identified by the
combination of both the associated kernfs_root and namespace tag.
This allows mounting different kernfs hierarchies.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/sysfs/mount.c | 10 ++++++----
fs/sysfs/sysfs.h | 6 ++++++
2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 0b5661b..f143b20 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -37,6 +37,7 @@ struct sysfs_dirent *sysfs_root_sd;

static int sysfs_fill_super(struct super_block *sb)
{
+ struct sysfs_super_info *info = sysfs_info(sb);
struct inode *inode;
struct dentry *root;

@@ -48,7 +49,7 @@ static int sysfs_fill_super(struct super_block *sb)

/* get root inode, initialize and unlock it */
mutex_lock(&sysfs_mutex);
- inode = sysfs_get_inode(sb, sysfs_root_sd);
+ inode = sysfs_get_inode(sb, info->root->sd);
mutex_unlock(&sysfs_mutex);
if (!inode) {
pr_debug("sysfs: could not get root inode\n");
@@ -61,8 +62,8 @@ static int sysfs_fill_super(struct super_block *sb)
pr_debug("%s: could not get root dentry!\n", __func__);
return -ENOMEM;
}
- kernfs_get(sysfs_root_sd);
- root->d_fsdata = sysfs_root_sd;
+ kernfs_get(info->root->sd);
+ root->d_fsdata = info->root->sd;
sb->s_root = root;
sb->s_d_op = &sysfs_dentry_ops;
return 0;
@@ -73,7 +74,7 @@ static int sysfs_test_super(struct super_block *sb, void *data)
struct sysfs_super_info *sb_info = sysfs_info(sb);
struct sysfs_super_info *info = data;

- return sb_info->ns == info->ns;
+ return sb_info->root == info->root && sb_info->ns == info->ns;
}

static int sysfs_set_super(struct super_block *sb, void *data)
@@ -110,6 +111,7 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
if (!info)
return ERR_PTR(-ENOMEM);

+ info->root = sysfs_root;
info->ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);

sb = sget(fs_type, sysfs_test_super, sysfs_set_super, flags, info);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 2b217ce..93b4b68 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -20,6 +20,12 @@

struct sysfs_super_info {
/*
+ * The root associated with this super_block. Each super_block is
+ * identified by the root and ns it's associated with.
+ */
+ struct kernfs_root *root;
+
+ /*
* Each sb is associated with one namespace tag, currently the network
* namespace of the task which mounted this sysfs instance. If multiple
* tags become necessary, make the following an array and compare
--
1.8.3.1