Re: [PATCH] permit fs->get_sb() to return alternative root

[Trond Myklebust <trond.myklebust@fys.uio.no>]

På ty , 18/05/2004 klokka 10:14, skreiv David Howells:
> Hi Al, Linux,
> 
> Here's a patch to add an extra argument to the get_sb() method of struct
> file_system_type that allows a filesystem to suggest an alternative dentry to
> be attached to the vfsmount structure. If no such suggestion is made,
> sb->s_root is selected as usual.

Cool..

> @@ -762,15 +763,18 @@
>  		}
>  	}
>  
> -	sb = type->get_sb(type, flags, name, data);
> +	root = NULL;
> +	sb = type->get_sb(type, flags, name, data, &root);
>  	if (IS_ERR(sb))
>  		goto out_free_secdata;
> +	if (!root)
> +		root = sb->s_root;
>   	error = security_sb_kern_mount(sb, secdata);
>   	if (error)
>   		goto out_sb;
>  	mnt->mnt_sb = sb;
> -	mnt->mnt_root = dget(sb->s_root);
> -	mnt->mnt_mountpoint = sb->s_root;
> +	mnt->mnt_root = dget(root);
> +	mnt->mnt_mountpoint = mnt->mnt_root;

This looks a bit iffy... Shouldn't that be

 +	if (!root)
 +		root = dget(sb->s_root);
....
 +	mnt->mnt_root = root;

Unless the filesystem has taken a reference to the dentry in "root", it
just won't be guaranteed to still exist.

Cheers,
  Trond
-
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