linux-kernel - Re: [RFC 09/23] filemap: use mapping_min

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Date:   Fri, 15 Sep 2023 20:54:07 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Pankaj Raghav <kernel@...kajraghav.com>
Cc:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        p.raghav@...sung.com, david@...morbit.com, da.gomez@...sung.com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        djwong@...nel.org, linux-mm@...ck.org, chandan.babu@...cle.com,
        mcgrof@...nel.org, gost.dev@...sung.com
Subject: Re: [RFC 09/23] filemap: use mapping_min_order while allocating
 folios

On Fri, Sep 15, 2023 at 08:38:34PM +0200, Pankaj Raghav wrote:
> From: Pankaj Raghav <p.raghav@...sung.com>
> 
> Allocate al teast mapping_min_order when creating new folio for the
> filemap in filemap_create_folio() and do_read_cache_folio().

This patch is where you should be doing:

	index &= ~(folio_nr_pages(folio) - 1UL);

(or similar)

> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
>  mm/filemap.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 21e1341526ab..e4d46f79e95d 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2502,7 +2502,8 @@ static int filemap_create_folio(struct file *file,
>  	struct folio *folio;
>  	int error;
>  
> -	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
> +	folio = filemap_alloc_folio(mapping_gfp_mask(mapping),
> +				    mapping_min_folio_order(mapping));
>  	if (!folio)
>  		return -ENOMEM;
>  
> @@ -3696,7 +3697,8 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
>  repeat:
>  	folio = filemap_get_folio(mapping, index);
>  	if (IS_ERR(folio)) {
> -		folio = filemap_alloc_folio(gfp, 0);
> +		folio = filemap_alloc_folio(gfp,
> +					    mapping_min_folio_order(mapping));
>  		if (!folio)
>  			return ERR_PTR(-ENOMEM);
>  		err = filemap_add_folio(mapping, folio, index, gfp);
> -- 
> 2.40.1
>