Re: [PATCH v3 6/9] fuse: convert fuse_writepages_fill() to use a folio for its tmp page

[Josef Bacik <josef@toxicpanda.com>]

On Fri, Aug 23, 2024 at 09:27:27AM -0700, Joanne Koong wrote:
> To pave the way for refactoring out the shared logic in
> fuse_writepages_fill() and fuse_writepage_locked(), this change converts
> the temporary page in fuse_writepages_fill() to use the folio API.
> 
> This is similar to the change in e0887e095a80 ("fuse: Convert
> fuse_writepage_locked to take a folio"), which converted the tmp page in
> fuse_writepage_locked() to use the folio API.
> 
> inc_node_page_state() is intentionally preserved here instead of
> converting to node_stat_add_folio() since it is updating the stat of the
> underlying page and to better maintain API symmetry with
> dec_node_page_stat() in fuse_writepage_finish_stat().
> 
> No functional changes added.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> ---
>  fs/fuse/file.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index a51b0b085616..905b202a7acd 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -2260,7 +2260,7 @@ static int fuse_writepages_fill(struct folio *folio,
>  	struct inode *inode = data->inode;
>  	struct fuse_inode *fi = get_fuse_inode(inode);
>  	struct fuse_conn *fc = get_fuse_conn(inode);
> -	struct page *tmp_page;
> +	struct folio *tmp_folio;
>  	int err;
>  
>  	if (wpa && fuse_writepage_need_send(fc, &folio->page, ap, data)) {
> @@ -2269,8 +2269,8 @@ static int fuse_writepages_fill(struct folio *folio,
>  	}
>  
>  	err = -ENOMEM;
> -	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
> -	if (!tmp_page)
> +	tmp_folio = folio_alloc(GFP_NOFS | __GFP_HIGHMEM, 0);
> +	if (!tmp_folio)
>  		goto out_unlock;
>  
>  	/*
> @@ -2290,7 +2290,7 @@ static int fuse_writepages_fill(struct folio *folio,
>  		err = -ENOMEM;
>  		wpa = fuse_writepage_args_alloc();
>  		if (!wpa) {
> -			__free_page(tmp_page);
> +			folio_put(tmp_folio);
>  			goto out_unlock;
>  		}
>  		fuse_writepage_add_to_bucket(fc, wpa);
> @@ -2308,14 +2308,14 @@ static int fuse_writepages_fill(struct folio *folio,
>  	}
>  	folio_start_writeback(folio);
>  
> -	copy_highpage(tmp_page, &folio->page);
> -	ap->pages[ap->num_pages] = tmp_page;
> +	folio_copy(tmp_folio, folio);
> +	ap->pages[ap->num_pages] = &tmp_folio->page;
>  	ap->descs[ap->num_pages].offset = 0;
>  	ap->descs[ap->num_pages].length = PAGE_SIZE;
>  	data->orig_pages[ap->num_pages] = &folio->page;
>  
>  	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
> -	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
> +	inc_node_page_state(&tmp_folio->page, NR_WRITEBACK_TEMP);

I *think* you can use

node_stat_add_folio(tmp_folio, NR_WRITEBACK_TEMP);

here instead of inc_node_page_state().  Thanks,

Josef