Re: [PATCH 20/21] AUTOFS: Make sure all dentries refs are released before calling kill_anon_super()

[Andrew Morton <akpm@osdl.org>]

On Thu, 06 Jul 2006 11:11:07 -0400
Trond Myklebust <Trond.Myklebust@netapp.com> wrote:

> From: David Howells <dhowells@redhat.com>
> 
> Make sure all dentries refs are released before calling kill_anon_super() so
> that the assumption that generic_shutdown_super() can completely destroy the
> dentry tree for there will be no external references holds true.
> 
> What was being done in the put_super() superblock op, is now done in the
> kill_sb() filesystem op instead, prior to calling kill_anon_super().
> 
> This makes the struct autofs_sb_info::root member variable redundant (since
> sb->s_root is still available), and so that is removed.  The calls to
> shrink_dcache_sb() are also removed since they're also redundant as
> shrink_dcache_for_umount() will now be called after the cleanup routine.
> 

AFAIK, Ian is still off thinking about this one?

> 
>  fs/autofs4/autofs_i.h |    3 +--
>  fs/autofs4/init.c     |    2 +-
>  fs/autofs4/inode.c    |   22 ++++------------------
>  fs/autofs4/waitq.c    |    1 -
>  4 files changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
> index d6603d0..47e38f3 100644
> --- a/fs/autofs4/autofs_i.h
> +++ b/fs/autofs4/autofs_i.h
> @@ -96,7 +96,6 @@ #define AUTOFS_TYPE_OFFSET       0x0004
>  
>  struct autofs_sb_info {
>  	u32 magic;
> -	struct dentry *root;
>  	int pipefd;
>  	struct file *pipe;
>  	pid_t oz_pgrp;
> @@ -231,4 +230,4 @@ out:
>  }
>  
>  void autofs4_dentry_release(struct dentry *);
> -
> +extern void autofs4_kill_sb(struct super_block *);
> diff --git a/fs/autofs4/init.c b/fs/autofs4/init.c
> index 5d91933..723a1c5 100644
> --- a/fs/autofs4/init.c
> +++ b/fs/autofs4/init.c
> @@ -24,7 +24,7 @@ static struct file_system_type autofs_fs
>  	.owner		= THIS_MODULE,
>  	.name		= "autofs",
>  	.get_sb		= autofs_get_sb,
> -	.kill_sb	= kill_anon_super,
> +	.kill_sb	= autofs4_kill_sb,
>  };
>  
>  static int __init init_autofs4_fs(void)
> diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
> index fde78b1..1bf68c5 100644
> --- a/fs/autofs4/inode.c
> +++ b/fs/autofs4/inode.c
> @@ -95,7 +95,7 @@ void autofs4_free_ino(struct autofs_info
>   */
>  static void autofs4_force_release(struct autofs_sb_info *sbi)
>  {
> -	struct dentry *this_parent = sbi->root;
> +	struct dentry *this_parent = sbi->sb->s_root;
>  	struct list_head *next;
>  
>  	spin_lock(&dcache_lock);
> @@ -126,7 +126,7 @@ resume:
>  		spin_lock(&dcache_lock);
>  	}
>  
> -	if (this_parent != sbi->root) {
> +	if (this_parent != sbi->sb->s_root) {
>  		struct dentry *dentry = this_parent;
>  
>  		next = this_parent->d_u.d_child.next;
> @@ -139,15 +139,9 @@ resume:
>  		goto resume;
>  	}
>  	spin_unlock(&dcache_lock);
> -
> -	dput(sbi->root);
> -	sbi->root = NULL;
> -	shrink_dcache_sb(sbi->sb);
> -
> -	return;
>  }
>  
> -static void autofs4_put_super(struct super_block *sb)
> +void autofs4_kill_sb(struct super_block *sb)
>  {
>  	struct autofs_sb_info *sbi = autofs4_sbi(sb);
>  
> @@ -162,6 +156,7 @@ static void autofs4_put_super(struct sup
>  	kfree(sbi);
>  
>  	DPRINTK("shutting down");
> +	kill_anon_super(sb);
>  }
>  
>  static int autofs4_show_options(struct seq_file *m, struct vfsmount *mnt)
> @@ -188,7 +183,6 @@ static int autofs4_show_options(struct s
>  }
>  
>  static struct super_operations autofs4_sops = {
> -	.put_super	= autofs4_put_super,
>  	.statfs		= simple_statfs,
>  	.show_options	= autofs4_show_options,
>  };
> @@ -314,7 +308,6 @@ int autofs4_fill_super(struct super_bloc
>  
>  	s->s_fs_info = sbi;
>  	sbi->magic = AUTOFS_SBI_MAGIC;
> -	sbi->root = NULL;
>  	sbi->pipefd = -1;
>  	sbi->catatonic = 0;
>  	sbi->exp_timeout = 0;
> @@ -396,13 +389,6 @@ int autofs4_fill_super(struct super_bloc
>  	sbi->pipefd = pipefd;
>  
>  	/*
> -	 * Take a reference to the root dentry so we get a chance to
> -	 * clean up the dentry tree on umount.
> -	 * See autofs4_force_release.
> -	 */
> -	sbi->root = dget(root);
> -
> -	/*
>  	 * Success! Install the root dentry now to indicate completion.
>  	 */
>  	s->s_root = root;
> diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
> index ce103e7..c0a6c8d 100644
> --- a/fs/autofs4/waitq.c
> +++ b/fs/autofs4/waitq.c
> @@ -45,7 +45,6 @@ void autofs4_catatonic_mode(struct autof
>  		fput(sbi->pipe);	/* Close the pipe */
>  		sbi->pipe = NULL;
>  	}
> -	shrink_dcache_sb(sbi->sb);
>  }
>  
>  static int autofs4_write(struct file *file, const void *addr, int bytes)