sysfs, kernfs: make super_blocks bind to different kernfs_roots

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 0b5661b..f143b20 100644 (file)
--- 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 (file)
--- 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