Re: [PATCH v4 2/3] fs/ufs: Change the signature of ufs_get_page()

[Ira Weiny]

On Wed, Dec 21, 2022 at 06:28:01PM +0100, Fabio M. De Francesco wrote:
> Change the signature of ufs_get_page() in order to prepare this function
> to the conversion to the use of kmap_local_page(). Change also those call
> sites which are required to conform its invocations to the new
> signature.
> 
> Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
> Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@xxxxxxxxx>
> ---
>  fs/ufs/dir.c | 49 +++++++++++++++++++++----------------------------
>  1 file changed, 21 insertions(+), 28 deletions(-)
> 
> diff --git a/fs/ufs/dir.c b/fs/ufs/dir.c
> index 69f78583c9c1..9fa86614d2d1 100644
> --- a/fs/ufs/dir.c
> +++ b/fs/ufs/dir.c
> @@ -185,7 +185,7 @@ static bool ufs_check_page(struct page *page)
>  	return false;
>  }
>  
> -static struct page *ufs_get_page(struct inode *dir, unsigned long n)
> +static void *ufs_get_page(struct inode *dir, unsigned long n, struct page **p)
>  {
>  	struct address_space *mapping = dir->i_mapping;
>  	struct page *page = read_mapping_page(mapping, n, NULL);
> @@ -195,8 +195,10 @@ static struct page *ufs_get_page(struct inode *dir, unsigned long n)
>  			if (!ufs_check_page(page))
>  				goto fail;
>  		}
> +		*p = page;
> +		return page_address(page);
>  	}
> -	return page;
> +	return ERR_CAST(page);
>  
>  fail:
>  	ufs_put_page(page);
> @@ -227,15 +229,12 @@ ufs_next_entry(struct super_block *sb, struct ufs_dir_entry *p)
>  
>  struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)
>  {
> -	struct page *page = ufs_get_page(dir, 0);
> -	struct ufs_dir_entry *de = NULL;
> +	struct ufs_dir_entry *de = ufs_get_page(dir, 0, p);

I don't know why but ufs_get_page() returning an address read really odd to me.
But rolling around my head alternative names nothing seems better than this.

>  
> -	if (!IS_ERR(page)) {
> -		de = ufs_next_entry(dir->i_sb,
> -				    (struct ufs_dir_entry *)page_address(page));
> -		*p = page;
> -	}
> -	return de;
> +	if (!IS_ERR(de))
> +		return ufs_next_entry(dir->i_sb, de);
> +	else
> +		return NULL;
>  }
>  
>  /*
> @@ -273,11 +272,10 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  		start = 0;
>  	n = start;
>  	do {
> -		char *kaddr;
> -		page = ufs_get_page(dir, n);
> -		if (!IS_ERR(page)) {
> -			kaddr = page_address(page);
> -			de = (struct ufs_dir_entry *) kaddr;
> +		char *kaddr = ufs_get_page(dir, n, &page);
> +
> +		if (!IS_ERR(kaddr)) {
> +			de = (struct ufs_dir_entry *)kaddr;
>  			kaddr += ufs_last_byte(dir, n) - reclen;
>  			while ((char *) de <= kaddr) {
>  				if (ufs_match(sb, namelen, name, de))
> @@ -328,12 +326,10 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	for (n = 0; n <= npages; n++) {
>  		char *dir_end;
>  
> -		page = ufs_get_page(dir, n);
> -		err = PTR_ERR(page);
> -		if (IS_ERR(page))
> -			goto out;
> +		kaddr = ufs_get_page(dir, n, &page);
> +		if (IS_ERR(kaddr))
> +			return PTR_ERR(kaddr);
>  		lock_page(page);
> -		kaddr = page_address(page);
>  		dir_end = kaddr + ufs_last_byte(dir, n);
>  		de = (struct ufs_dir_entry *)kaddr;
>  		kaddr += PAGE_SIZE - reclen;
> @@ -395,7 +391,6 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	/* OFFSET_CACHE */
>  out_put:
>  	ufs_put_page(page);
> -out:
>  	return err;
>  out_unlock:
>  	unlock_page(page);
> @@ -429,6 +424,7 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>  	unsigned chunk_mask = ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
>  	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);
>  	unsigned flags = UFS_SB(sb)->s_flags;
> +	struct page *page;

NIT: Does page now leave the scope of the for loop?

>  
>  	UFSD("BEGIN\n");
>  
> @@ -439,16 +435,14 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>  		char *kaddr, *limit;
>  		struct ufs_dir_entry *de;

Couldn't that be declared here?

Regardless I don't think this is broken.

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

>  
> -		struct page *page = ufs_get_page(inode, n);
> -
> -		if (IS_ERR(page)) {
> +		kaddr = ufs_get_page(inode, n, &page);
> +		if (IS_ERR(kaddr)) {
>  			ufs_error(sb, __func__,
>  				  "bad page in #%lu",
>  				  inode->i_ino);
>  			ctx->pos += PAGE_SIZE - offset;
>  			return -EIO;
>  		}
> -		kaddr = page_address(page);
>  		if (unlikely(need_revalidate)) {
>  			if (offset) {
>  				offset = ufs_validate_entry(sb, kaddr, offset, chunk_mask);
> @@ -595,12 +589,11 @@ int ufs_empty_dir(struct inode * inode)
>  	for (i = 0; i < npages; i++) {
>  		char *kaddr;
>  		struct ufs_dir_entry *de;
> -		page = ufs_get_page(inode, i);
>  
> -		if (IS_ERR(page))
> +		kaddr = ufs_get_page(inode, i, &page);
> +		if (IS_ERR(kaddr))
>  			continue;
>  
> -		kaddr = page_address(page);
>  		de = (struct ufs_dir_entry *)kaddr;
>  		kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);
>  
> -- 
> 2.39.0
>