sysfs: Basic support for multiple super blocks

Add all of the necessary bioler plate to support
multiple superblocks in sysfs.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 59 insertions, 2 deletions

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 776137828dca..db0b1f2138af 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -72,16 +72,70 @@ static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
         return 0;
 }
 
+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;
+        int found = 1;
+        return found;
+}
+
+static int sysfs_set_super(struct super_block *sb, void *data)
+{
+        int error;
+        error = set_anon_super(sb, data);
+        if (!error)
+                sb->s_fs_info = data;
+        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);
+        struct sysfs_super_info *info;
+        struct super_block *sb;
+        int error;
+
+        error = -ENOMEM;
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                goto out;
+        sb = sget(fs_type, sysfs_test_super, sysfs_set_super, info);
+        if (IS_ERR(sb) || sb->s_fs_info != info)
+                kfree(info);
+        if (IS_ERR(sb)) {
+                kfree(info);
+                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) {
+                        deactivate_locked_super(sb);
+                        goto out;
+                }
+                sb->s_flags |= MS_ACTIVE;
+        }
+
+        simple_set_mnt(mnt, sb);
+        error = 0;
+out:
+        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);
 }
 
 static struct file_system_type sysfs_fs_type = {
         .name           = "sysfs",
         .get_sb         = sysfs_get_sb,
-        .kill_sb        = kill_anon_super,
+        .kill_sb        = sysfs_kill_sb,
 };
 
 int __init sysfs_init(void)
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 30f5a44fb5d3..030a39dbb02c 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -114,6 +114,9 @@ struct sysfs_addrm_cxt {
 /*
  * mount.c
  */
+struct sysfs_super_info {
+};
+#define sysfs_info(SB) ((struct sysfs_super_info *)(SB->s_fs_info))
 extern struct sysfs_dirent sysfs_root;
 extern struct kmem_cache *sysfs_dir_cachep;