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From: Lance Yang <ioworker0@gmail.com>
To: baolin.wang@linux.alibaba.com
Cc: david@redhat.com,
	akpm@linux-foundation.org,
	linux-kernel@vger.kernel.org,
	linux-mm@kvack.org,
	Lance Yang <ioworker0@gmail.com>
Subject: Re: [PATCH] mm: huge_memory: add the missing folio_test_pmd_mappable() for THP split statistics
Date: Mon, 22 Apr 2024 14:17:20 +0800
Message-Id: <20240422061720.61697-1-ioworker0@gmail.com>
In-Reply-To: <a5341defeef27c9ac7b85c97f030f93e4368bbc1.1711694852.git.baolin.wang@linux.alibaba.com>
References: <a5341defeef27c9ac7b85c97f030f93e4368bbc1.1711694852.git.baolin.wang@linux.alibaba.com>
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Hey Baolin,

Maybe I spotted a bug and made a change to this patch as follows.

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 824eff9211db..f3c4e08c6d30 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2994,6 +2994,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 	XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
 	struct anon_vma *anon_vma = NULL;
 	struct address_space *mapping = NULL;
+	int order = folio_order(folio);
 	int extra_pins, ret;
 	pgoff_t end;
 	bool is_hzp;
@@ -3172,7 +3173,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 		i_mmap_unlock_read(mapping);
 out:
 	xas_destroy(&xas);
-	if (folio_test_pmd_mappable(folio))

IIUC, if we split the folio successfully, it won’t be large here.

+	if (order >= HPAGE_PMD_ORDER)
 		count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
 	return ret;
 }

Thanks,
Lance