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Date:   Fri, 15 Sep 2023 20:03:14 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Pankaj Raghav <kernel@pankajraghav.com>
Cc:     linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
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        djwong@kernel.org, linux-mm@kvack.org, chandan.babu@oracle.com,
        mcgrof@kernel.org, gost.dev@samsung.com
Subject: Re: [RFC 01/23] fs: Allow fine-grained control of folio sizes
Message-ID: <ZQSqctT6k7uKQHmF@casper.infradead.org>
References: <20230915183848.1018717-1-kernel@pankajraghav.com>
 <20230915183848.1018717-2-kernel@pankajraghav.com>
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On Fri, Sep 15, 2023 at 08:38:26PM +0200, Pankaj Raghav wrote:
> +static inline void mapping_set_folio_orders(struct address_space *mapping,
> +					    unsigned int min, unsigned int max)
> +{
> +	/*
> +	 * XXX: max is ignored as only minimum folio order is supported
> +	 * currently.
> +	 */

I think we need some sanity checking ...

	if (min == 1)
		min = 2;
	if (max < min)
		max = min;
	if (max > MAX_PAGECACHE_ORDER)
		max = MAX_PAGECACHE_ORDER;

> +	mapping->flags = (mapping->flags & ~AS_FOLIO_ORDER_MASK) |
> +			 (min << AS_FOLIO_ORDER_MIN) |
> +			 (MAX_PAGECACHE_ORDER << AS_FOLIO_ORDER_MAX);
> +}