From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by kanga.kvack.org (Postfix) with ESMTP id C8E366B0003 for ; Fri, 2 Nov 2018 11:31:54 -0400 (EDT) Received: by mail-wm1-f71.google.com with SMTP id t74-v6so1071427wmt.0 for ; Fri, 02 Nov 2018 08:31:54 -0700 (PDT) Received: from mout.kundenserver.de (mout.kundenserver.de. [217.72.192.74]) by mx.google.com with ESMTPS id e8-v6si7805250wrw.379.2018.11.02.08.31.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 02 Nov 2018 08:31:53 -0700 (PDT) From: Arnd Bergmann Subject: [PATCH] mm: fix uninitialized variable warnings Date: Fri, 2 Nov 2018 16:31:06 +0100 Message-Id: <20181102153138.1399758-1-arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Jan Kara Cc: Arnd Bergmann , Michal Hocko , Wang Long , Matthew Wilcox , Dave Chinner , linux-mm@kvack.org, linux-kernel@vger.kernel.org In a rare randconfig build, I got a warning about possibly uninitialized variables: mm/page-writeback.c: In function 'balance_dirty_pages': mm/page-writeback.c:1623:16: error: 'writeback' may be used uninitialized in this function [-Werror=maybe-uninitialized] mdtc->dirty += writeback; ^~ mm/page-writeback.c:1624:4: error: 'filepages' may be used uninitialized in this function [-Werror=maybe-uninitialized] mdtc_calc_avail(mdtc, filepages, headroom); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ mm/page-writeback.c:1624:4: error: 'headroom' may be used uninitialized in this function [-Werror=maybe-uninitialized] The compiler evidently fails to notice that the usage is in dead code after 'mdtc' is set to NULL when CONFIG_CGROUP_WRITEBACK is disabled. Adding an IS_ENABLED() check makes this clear to the compiler. Signed-off-by: Arnd Bergmann --- mm/page-writeback.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 3f690bae6b78..f02535b7731a 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1611,7 +1611,7 @@ static void balance_dirty_pages(struct bdi_writeback *wb, bg_thresh = gdtc->bg_thresh; } - if (mdtc) { + if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { unsigned long filepages, headroom, writeback; /* @@ -1944,7 +1944,7 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb) wb_calc_thresh(gdtc->wb, gdtc->bg_thresh)) return true; - if (mdtc) { + if (IS_ENABLED(CONFIG_CGROUP_WRITEBACK) && mdtc) { unsigned long filepages, headroom, writeback; mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty, -- 2.18.0