linux-kernel - Re: [PATCH v5 1/4] fs/ufs: Use the offset_in

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Date:   Thu, 29 Dec 2022 16:41:31 -0800
From:   Ira Weiny <ira.weiny@...el.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>
CC:     Evgeniy Dushistov <dushistov@...l.ru>,
        Al Viro <viro@...iv.linux.org.uk>,
        <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v5 1/4] fs/ufs: Use the offset_in_page() helper

On Thu, Dec 29, 2022 at 11:50:57PM +0100, Fabio M. De Francesco wrote:
> Use the offset_in_page() helper because it is more suitable than doing
> explicit subtractions between pointers to directory entries and kernel
> virtual addresses of mapped pages.
> 
> Cc: Ira Weiny <ira.weiny@...el.com>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

> Suggested-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---
>  fs/ufs/dir.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/ufs/dir.c b/fs/ufs/dir.c
> index 391efaf1d528..69f78583c9c1 100644
> --- a/fs/ufs/dir.c
> +++ b/fs/ufs/dir.c
> @@ -87,8 +87,7 @@ void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
>  		  struct page *page, struct inode *inode,
>  		  bool update_times)
>  {
> -	loff_t pos = page_offset(page) +
> -			(char *) de - (char *) page_address(page);
> +	loff_t pos = page_offset(page) + offset_in_page(de);
>  	unsigned len = fs16_to_cpu(dir->i_sb, de->d_reclen);
>  	int err;
>  
> @@ -371,8 +370,7 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	return -EINVAL;
>  
>  got_it:
> -	pos = page_offset(page) +
> -			(char*)de - (char*)page_address(page);
> +	pos = page_offset(page) + offset_in_page(de);
>  	err = ufs_prepare_chunk(page, pos, rec_len);
>  	if (err)
>  		goto out_unlock;
> @@ -497,8 +495,8 @@ int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
>  {
>  	struct super_block *sb = inode->i_sb;
>  	char *kaddr = page_address(page);
> -	unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
> -	unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);
> +	unsigned int from = offset_in_page(dir) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
> +	unsigned int to = offset_in_page(dir) + fs16_to_cpu(sb, dir->d_reclen);
>  	loff_t pos;
>  	struct ufs_dir_entry *pde = NULL;
>  	struct ufs_dir_entry *de = (struct ufs_dir_entry *) (kaddr + from);
> @@ -522,7 +520,7 @@ int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
>  		de = ufs_next_entry(sb, de);
>  	}
>  	if (pde)
> -		from = (char*)pde - (char*)page_address(page);
> +		from = offset_in_page(pde);
>  
>  	pos = page_offset(page) + from;
>  	lock_page(page);
> -- 
> 2.39.0
>