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@xxxxxxxx>
---
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
