Re: [PATCH v2 1/2] Revert "NFS: nfs_rename() handle -ERESTARTSYS dentry left behind"

[Jeff Layton <jlayton@redhat.com>]

On Thu, 2017-06-15 at 16:59 -0400, Benjamin Coddington wrote:
> This reverts commit 920b4530fb80430ff30ef83efe21ba1fa5623731 which could
> call d_move() without holding the directory's i_mutex, and reverts commit
> d4ea7e3c5c0e341c15b073016dbf3ab6c65f12f3 "NFS: Fix old dentry rehash after
> move", which was a follow-up fix.
> 
> Fixes: 920b4530fb80 ("NFS: nfs_rename() handle -ERESTARTSYS dentry left behind")
> Cc: stable@vger.kernel.org # v4.10+
> ---
>  fs/nfs/dir.c | 45 ++++++++++++++++++---------------------------
>  1 file changed, 18 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 32ccd7754f8a..1faf337b316f 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -1946,29 +1946,6 @@ nfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
>  }
>  EXPORT_SYMBOL_GPL(nfs_link);
>  
> -static void
> -nfs_complete_rename(struct rpc_task *task, struct nfs_renamedata *data)
> -{
> -	struct dentry *old_dentry = data->old_dentry;
> -	struct dentry *new_dentry = data->new_dentry;
> -	struct inode *old_inode = d_inode(old_dentry);
> -	struct inode *new_inode = d_inode(new_dentry);
> -
> -	nfs_mark_for_revalidate(old_inode);
> -
> -	switch (task->tk_status) {
> -	case 0:
> -		if (new_inode != NULL)
> -			nfs_drop_nlink(new_inode);
> -		d_move(old_dentry, new_dentry);
> -		nfs_set_verifier(new_dentry,
> -					nfs_save_change_attribute(data->new_dir));
> -		break;
> -	case -ENOENT:
> -		nfs_dentry_handle_enoent(old_dentry);
> -	}
> -}
> -
>  /*
>   * RENAME
>   * FIXME: Some nfsds, like the Linux user space nfsd, may generate a
> @@ -1999,7 +1976,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>  {
>  	struct inode *old_inode = d_inode(old_dentry);
>  	struct inode *new_inode = d_inode(new_dentry);
> -	struct dentry *dentry = NULL;
> +	struct dentry *dentry = NULL, *rehash = NULL;
>  	struct rpc_task *task;
>  	int error = -EBUSY;
>  
> @@ -2022,8 +1999,10 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>  		 * To prevent any new references to the target during the
>  		 * rename, we unhash the dentry in advance.
>  		 */
> -		if (!d_unhashed(new_dentry))
> +		if (!d_unhashed(new_dentry)) {
>  			d_drop(new_dentry);
> +			rehash = new_dentry;
> +		}
>  
>  		if (d_count(new_dentry) > 2) {
>  			int err;
> @@ -2040,6 +2019,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>  				goto out;
>  
>  			new_dentry = dentry;
> +			rehash = NULL;
>  			new_inode = NULL;
>  		}
>  	}
> @@ -2048,8 +2028,7 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>  	if (new_inode != NULL)
>  		NFS_PROTO(new_inode)->return_delegation(new_inode);
>  
> -	task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry,
> -					nfs_complete_rename);
> +	task = nfs_async_rename(old_dir, new_dir, old_dentry, new_dentry, NULL);
>  	if (IS_ERR(task)) {
>  		error = PTR_ERR(task);
>  		goto out;
> @@ -2059,9 +2038,21 @@ int nfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>  	if (error == 0)
>  		error = task->tk_status;
>  	rpc_put_task(task);
> +	nfs_mark_for_revalidate(old_inode);
>  out:
> +	if (rehash)
> +		d_rehash(rehash);
>  	trace_nfs_rename_exit(old_dir, old_dentry,
>  			new_dir, new_dentry, error);
> +	if (!error) {
> +		if (new_inode != NULL)
> +			nfs_drop_nlink(new_inode);
> +		d_move(old_dentry, new_dentry);
> +		nfs_set_verifier(new_dentry,
> +					nfs_save_change_attribute(new_dir));
> +	} else if (error == -ENOENT)
> +		nfs_dentry_handle_enoent(old_dentry);
> +

Could you add a comment about why we need to do the d_move here instead
of in the completion handler? I worry that someone else may make the
same mistake later if we don't leave some breadcrumbs.

>  	/* new dentry created? */
>  	if (dentry)
>  		dput(dentry);

You can add this to both. Thanks for turning this around quickly:

Reviewed-by: Jeff Layton <jlayton@redhat.com>