kernfs: implement kernfs_root->supers list

Currently, there's no way to find out which super_blocks are
associated with a given kernfs_root.  Let's implement it - the planned
inotify extension to kernfs_notify() needs it.

Make kernfs_super_info point back to the super_block and chain it at
kernfs_root->supers.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 78f3403..43aa979 100644 (file)
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -711,6 +711,7 @@ struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
                return ERR_PTR(-ENOMEM);
 
        ida_init(&root->ino_ida);
+       INIT_LIST_HEAD(&root->supers);
 
        kn = __kernfs_new_node(root, "", S_IFDIR | S_IRUGO | S_IXUGO,
                               KERNFS_DIR);

diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-internal.h
index 8be13b2..dc84a3e 100644 (file)
--- a/fs/kernfs/kernfs-internal.h
+++ b/fs/kernfs/kernfs-internal.h
@@ -49,6 +49,8 @@ static inline struct kernfs_root *kernfs_root(struct kernfs_node *kn)
  * mount.c
  */
 struct kernfs_super_info {
+       struct super_block      *sb;
+
        /*
         * The root associated with this super_block.  Each super_block is
         * identified by the root and ns it's associated with.
@@ -62,6 +64,9 @@ struct kernfs_super_info {
         * an array and compare kernfs_node tag against every entry.
         */
        const void              *ns;
+
+       /* anchored at kernfs_root->supers, protected by kernfs_mutex */
+       struct list_head        node;
 };
 #define kernfs_info(SB) ((struct kernfs_super_info *)(SB->s_fs_info))
 

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 6a5f04a..f25a7c0 100644 (file)
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -68,6 +68,7 @@ static int kernfs_fill_super(struct super_block *sb)
        struct inode *inode;
        struct dentry *root;
 
+       info->sb = sb;
        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
        sb->s_magic = SYSFS_MAGIC;
@@ -166,12 +167,18 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
                *new_sb_created = !sb->s_root;
 
        if (!sb->s_root) {
+               struct kernfs_super_info *info = kernfs_info(sb);
+
                error = kernfs_fill_super(sb);
                if (error) {
                        deactivate_locked_super(sb);
                        return ERR_PTR(error);
                }
                sb->s_flags |= MS_ACTIVE;
+
+               mutex_lock(&kernfs_mutex);
+               list_add(&info->node, &root->supers);
+               mutex_unlock(&kernfs_mutex);
        }
 
        return dget(sb->s_root);
@@ -190,6 +197,10 @@ void kernfs_kill_sb(struct super_block *sb)
        struct kernfs_super_info *info = kernfs_info(sb);
        struct kernfs_node *root_kn = sb->s_root->d_fsdata;
 
+       mutex_lock(&kernfs_mutex);
+       list_del(&info->node);
+       mutex_unlock(&kernfs_mutex);
+
        /*
         * Remove the superblock from fs_supers/s_instances
         * so we can't find it, before freeing kernfs_super_info.

diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index b0122dc..589318b 100644 (file)
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -144,6 +144,10 @@ struct kernfs_root {
        /* private fields, do not use outside kernfs proper */
        struct ida              ino_ida;
        struct kernfs_syscall_ops *syscall_ops;
+
+       /* list of kernfs_super_info of this root, protected by kernfs_mutex */
+       struct list_head        supers;
+
        wait_queue_head_t       deactivate_waitq;
 };