linux-kernel - [RFC v1 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL

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Message-Id: <20200228154322.329228-3-imbrenda@linux.ibm.com>
Date:   Fri, 28 Feb 2020 16:43:21 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     linux-next@...r.kernel.org, akpm@...ux-foundation.org
Cc:     borntraeger@...ibm.com, david@...hat.com, aarcange@...hat.com,
        linux-mm@...ck.org, frankja@...ux.ibm.com, sfr@...b.auug.org.au,
        jhubbard@...dia.com, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org
Subject: [RFC v1 1/2] mm/gup: fixup for 9947ea2c1e608e32 "mm/gup: track FOLL_PIN pages"

In case pin fails, we need to unpin, a simple put_page will not be enough

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 mm/gup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index f589299b0d4a..0b9a806898f3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2134,7 +2134,10 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 			goto pte_unmap;
 
 		if (unlikely(pte_val(pte) != pte_val(*ptep))) {
-			put_page(head);
+			if (flags & FOLL_GET)
+				put_page(head);
+			else if (flags & FOLL_PIN)
+				unpin_user_page(head);
 			goto pte_unmap;
 		}
 
-- 
2.24.1