From: Arnd Bergmann <arnd@arndb.de>
To: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>, Michal Hocko <mhocko@suse.com>,
Wang Long <wanglong19@meituan.com>,
Matthew Wilcox <willy@infradead.org>,
Dave Chinner <dchinner@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH] mm: fix uninitialized variable warnings
Date: Fri, 2 Nov 2018 16:31:06 +0100 [thread overview]
Message-ID: <20181102153138.1399758-1-arnd@arndb.de> (raw)
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 <arnd@arndb.de>
---
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
next reply other threads:[~2018-11-02 15:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-02 15:31 Arnd Bergmann [this message]
2018-11-05 9:01 ` [PATCH] mm: fix uninitialized variable warnings Jan Kara
2018-11-05 15:35 ` Arnd Bergmann
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