linux-kernel - [PATCH v2 3/5] mm: Support removing arbitrary sized pages from mapping

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Message-ID: <20191017164223.2762148-4-songliubraving@fb.com>
Date:   Thu, 17 Oct 2019 09:42:20 -0700
From:   Song Liu <songliubraving@...com>
To:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <akpm@...ux-foundation.org>
CC:     <matthew.wilcox@...cle.com>, <kernel-team@...com>,
        <william.kucharski@...cle.com>, <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Song Liu <songliubraving@...com>
Subject: [PATCH v2 3/5] 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.

Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: William Kucharski <william.kucharski@...cle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Signed-off-by: Song Liu <songliubraving@...com>
---
 mm/vmscan.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c6659bb758a4..f870da1f4bb7 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 */
-- 
2.17.1