linux-kernel - [PATCH stable 6.1] mm: Fix is_zero_page() usage in try_grab

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Message-ID: <20250416202441.3911142-1-alex.williamson@redhat.com>
Date: Wed, 16 Apr 2025 14:24:39 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: 
Cc: Alex Williamson <alex.williamson@...hat.com>,
	Salvatore Bonaccorso <carnil@...ian.org>,
	Milan Broz <gmazyland@...il.com>,
	stable@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH stable 6.1] mm: Fix is_zero_page() usage in try_grab_page()

The backport of upstream commit c8070b787519 ("mm: Don't pin ZERO_PAGE
in pin_user_pages()") into v6.1.130 noted below in Fixes does not
account for commit 0f0892356fa1 ("mm: allow multiple error returns in
try_grab_page()"), which changed the return value of try_grab_page()
from bool to int.  Therefore returning 0, success in the upstream
version, becomes an error here.  Fix the return value.

Fixes: 476c1dfefab8 ("mm: Don't pin ZERO_PAGE in pin_user_pages()")
Link: https://lore.kernel.org/all/Z_6uhLQjJ7SSzI13@eldamar.lan
Reported-by: Salvatore Bonaccorso <carnil@...ian.org>
Reported-by: Milan Broz <gmazyland@...il.com>
Cc: stable@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: Sasha Levin <sashal@...nel.org>
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
 mm/gup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index b1daaa9d89aa..76a2b0943e2d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -232,7 +232,7 @@ bool __must_check try_grab_page(struct page *page, unsigned int flags)
 		 * and it is used in a *lot* of places.
 		 */
 		if (is_zero_page(page))
-			return 0;
+			return true;
 
 		/*
 		 * Similar to try_grab_folio(): be sure to *also*
-- 
2.48.1