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Date:	Thu, 24 Jul 2014 04:09:19 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Miklos Szeredi <miklos@...redi.hu>
cc:	linux-kernel@...r.kernel.org, hch@...radead.org,
	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	Miklos Szeredi <mszeredi@...e.cz>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 5/7] shmem: support RENAME_EXCHANGE

On Wed, 23 Jul 2014, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> This is really simple in tmpfs since the VFS already takes care of
> shuffling the dentries.  Just adjust nlink on parent directories and touch
> c & mtimes.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> Cc: Hugh Dickins <hughd@...gle.com>

Acked-by: Hugh Dickins <hughd@...gle.com>

> ---
>  mm/shmem.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 791b05514f9a..75d5ac806f1e 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2016,6 +2016,28 @@ static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
>  	return shmem_unlink(dir, dentry);
>  }
>  
> +static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
> +{
> +	bool old_is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
> +	bool new_is_dir = S_ISDIR(new_dentry->d_inode->i_mode);
> +
> +	if (old_dir != new_dir && old_is_dir != new_is_dir) {
> +		if (old_is_dir) {
> +			drop_nlink(old_dir);
> +			inc_nlink(new_dir);
> +		} else {
> +			drop_nlink(new_dir);
> +			inc_nlink(old_dir);
> +		}
> +	}
> +	old_dir->i_ctime = old_dir->i_mtime =
> +	new_dir->i_ctime = new_dir->i_mtime =
> +	old_dentry->d_inode->i_ctime =
> +	new_dentry->d_inode->i_ctime = CURRENT_TIME;
> +
> +	return 0;
> +}
> +
>  /*
>   * The VFS layer already does all the dentry stuff for rename,
>   * we just have to decrement the usage count for the target if
> @@ -2027,9 +2049,12 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
>  	struct inode *inode = old_dentry->d_inode;
>  	int they_are_dirs = S_ISDIR(inode->i_mode);
>  
> -	if (flags & ~(RENAME_NOREPLACE))
> +	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
>  		return -EINVAL;
>  
> +	if (flags & RENAME_EXCHANGE)
> +		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
> +
>  	if (!simple_empty(new_dentry))
>  		return -ENOTEMPTY;
>  
> -- 
> 1.8.1.4
--
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