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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Song Liu <songliubraving@fb.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Rik van Riel <riel@surriel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 099/142] mm,thp: stop leaking unreleased file pages
Date:   Mon,  1 Jun 2020 19:54:17 +0200
Message-Id: <20200601174048.229621580@linuxfoundation.org>
In-Reply-To: <20200601174037.904070960@linuxfoundation.org>
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From: Hugh Dickins <hughd@google.com>

[ Upstream commit 2f33a706027c94cd4f70fcd3e3f4a17c1ce4ea4b ]

When collapse_file() calls try_to_release_page(), it has already isolated
the page: so if releasing buffers happens to fail (as it sometimes does),
remember to putback_lru_page(): otherwise that page is left unreclaimable
and unfreeable, and the file extent uncollapsible.

Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: <stable@vger.kernel.org>	[5.4+]
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2005231837500.1766@eggly.anvils
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/khugepaged.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a8a57bebb5fa..f765475be359 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1655,6 +1655,7 @@ static void collapse_file(struct mm_struct *mm,
 		if (page_has_private(page) &&
 		    !try_to_release_page(page, GFP_KERNEL)) {
 			result = SCAN_PAGE_HAS_PRIVATE;
+			putback_lru_page(page);
 			goto out_unlock;
 		}
 
-- 
2.25.1