linux-kernel - [PATCH 12/15] mm: Support removing arbitrary sized pages from mapping

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Message-Id: <20190925005214.27240-13-willy@infradead.org>
Date:   Tue, 24 Sep 2019 17:52:11 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     William Kucharski <william.kucharski@...cle.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH 12/15] mm: Support removing arbitrary sized pages from mapping

From: William Kucharski <william.kucharski@...cle.com>

__remove_mapping() assumes that pages can only be either base pages
or HPAGE_PMD_SIZE.  Ask the page what size it is.

Signed-off-by: William Kucharski <william.kucharski@...cle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/vmscan.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a7f9f379e523..9f44868e640b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -932,10 +932,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page,
 	 * Note that if SetPageDirty is always performed via set_page_dirty,
 	 * and thus under the i_pages lock, then this ordering is not required.
 	 */
-	if (unlikely(PageTransHuge(page)) && PageSwapCache(page))
-		refcount = 1 + HPAGE_PMD_NR;
-	else
-		refcount = 2;
+	refcount = 1 + compound_nr(page);
 	if (!page_ref_freeze(page, refcount))
 		goto cannot_free;
 	/* note: atomic_cmpxchg in page_ref_freeze provides the smp_rmb */
-- 
2.23.0