[v2,16/20] nfs{,4}_lookup_validate(): use stable parent inode passed by caller

we can't kill __nfs_lookup_revalidate() completely, but ->d_parent boilerplate
in it is gone

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/nfs/dir.c | 43 +++++++++++++------------------------------
 1 file changed, 13 insertions(+), 30 deletions(-)

On Thu, 2025-01-16 at 05:23 +0000, Al Viro wrote:
> we can't kill __nfs_lookup_revalidate() completely, but ->d_parent boilerplate
> in it is gone
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
>  fs/nfs/dir.c | 43 +++++++++++++------------------------------
>  1 file changed, 13 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 9910d9796f4c..c28983ee75ca 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -1732,8 +1732,8 @@ static int nfs_lookup_revalidate_dentry(struct inode *dir,
>   * cached dentry and do a new lookup.
>   */
>  static int
> -nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
> -			 unsigned int flags)
> +nfs_do_lookup_revalidate(struct inode *dir, const struct qstr *name,
> +			 struct dentry *dentry, unsigned int flags)
>  {
>  	struct inode *inode;
>  	int error = 0;
> @@ -1785,39 +1785,26 @@ nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
>  }
>  
>  static int
> -__nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags,
> -			int (*reval)(struct inode *, struct dentry *, unsigned int))
> +__nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
>  {
> -	struct dentry *parent;
> -	struct inode *dir;
> -	int ret;
> -
>  	if (flags & LOOKUP_RCU) {
>  		if (dentry->d_fsdata == NFS_FSDATA_BLOCKED)
>  			return -ECHILD;
> -		parent = READ_ONCE(dentry->d_parent);
> -		dir = d_inode_rcu(parent);
> -		if (!dir)
> -			return -ECHILD;
> -		ret = reval(dir, dentry, flags);
> -		if (parent != READ_ONCE(dentry->d_parent))
> -			return -ECHILD;
>  	} else {
>  		/* Wait for unlink to complete - see unblock_revalidate() */
>  		wait_var_event(&dentry->d_fsdata,
>  			       smp_load_acquire(&dentry->d_fsdata)
>  			       != NFS_FSDATA_BLOCKED);
> -		parent = dget_parent(dentry);
> -		ret = reval(d_inode(parent), dentry, flags);
> -		dput(parent);
>  	}
> -	return ret;
> +	return 0;
>  }
>  
>  static int nfs_lookup_revalidate(struct inode *dir, const struct qstr *name,
>  				 struct dentry *dentry, unsigned int flags)
>  {
> -	return __nfs_lookup_revalidate(dentry, flags, nfs_do_lookup_revalidate);
> +	if (__nfs_lookup_revalidate(dentry, flags))
> +		return -ECHILD;
> +	return nfs_do_lookup_revalidate(dir, name, dentry, flags);
>  }
>  
>  static void block_revalidate(struct dentry *dentry)
> @@ -2216,11 +2203,14 @@ int nfs_atomic_open(struct inode *dir, struct dentry *dentry,
>  EXPORT_SYMBOL_GPL(nfs_atomic_open);
>  
>  static int
> -nfs4_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
> -			  unsigned int flags)
> +nfs4_lookup_revalidate(struct inode *dir, const struct qstr *name,
> +		       struct dentry *dentry, unsigned int flags)
>  {
>  	struct inode *inode;
>  
> +	if (__nfs_lookup_revalidate(dentry, flags))
> +		return -ECHILD;
> +
>  	trace_nfs_lookup_revalidate_enter(dir, dentry, flags);
>  
>  	if (!(flags & LOOKUP_OPEN) || (flags & LOOKUP_DIRECTORY))
> @@ -2259,14 +2249,7 @@ nfs4_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
>  	return nfs_lookup_revalidate_dentry(dir, dentry, inode, flags);
>  
>  full_reval:
> -	return nfs_do_lookup_revalidate(dir, dentry, flags);
> -}
> -
> -static int nfs4_lookup_revalidate(struct inode *dir, const struct qstr *name,
> -				  struct dentry *dentry, unsigned int flags)
> -{
> -	return __nfs_lookup_revalidate(dentry, flags,
> -			nfs4_do_lookup_revalidate);
> +	return nfs_do_lookup_revalidate(dir, name, dentry, flags);
>  }
>  
>  #endif /* CONFIG_NFSV4 */

Much nicer without the "reval" callback.

Reviewed-by: Jeff Layton <jlayton@kernel.org>