Received-SPF: pass (google.com: domain of linux-kernel+bounces-23809-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Thu, 11 Jan 2024 15:42:55 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Byungchul Park <byungchul@sk.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	kernel_team@skhynix.com, akpm@linux-foundation.org,
	ying.huang@intel.com, namit@vmware.com, xhao@linux.alibaba.com,
	mgorman@techsingularity.net, hughd@google.com, david@redhat.com,
	peterz@infradead.org, luto@kernel.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com
Subject: Re: [v5 4/7] mm: Separate move/undo doing on folio list from
 migrate_pages_batch()
Message-ID: <ZaAMf5JX2D3N7Epi@casper.infradead.org>
References: <20240111060757.13563-1-byungchul@sk.com>
 <20240111060757.13563-5-byungchul@sk.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240111060757.13563-5-byungchul@sk.com>

On Thu, Jan 11, 2024 at 03:07:54PM +0900, Byungchul Park wrote:
> +static void migrate_folios_move(struct list_head *src_folios,
> +		struct list_head *dst_folios,
> +		free_folio_t put_new_folio, unsigned long private,
> +		enum migrate_mode mode, int reason,
> +		struct list_head *ret_folios,
> +		struct migrate_pages_stats *stats,
> +		int *retry, int *thp_retry, int *nr_failed,
> +		int *nr_retry_pages)
> +{
> +	struct folio *folio, *folio2, *dst, *dst2;
> +	bool is_thp;
> +	int nr_pages;
> +	int rc;
> +
> +	dst = list_first_entry(dst_folios, struct folio, lru);
> +	dst2 = list_next_entry(dst, lru);
> +	list_for_each_entry_safe(folio, folio2, src_folios, lru) {
> +		is_thp = folio_test_large(folio) && folio_test_pmd_mappable(folio);

You don't need to call folio_test_large() first.  folio_order() includes
a call to test_large() so it can return 0.

> +		nr_pages = folio_nr_pages(folio);

.. or since you're calculating this anyway,

		is_thp = nr_pages >= HPAGE_PMD_NR
perhaps