mm: fix arithmetic for max_prop_frac when setting max_ratio

Since now bdi->max_ratio is part per million, fix the wrong arithmetic for max_prop_frac when setting max_ratio. Otherwise the miscalculated max_prop_frac will affect the incrementing of writeout completion count when max_ratio is not 100%. Link: https://lkml.kernel.org/r/[email protected] Fixes: efc3e6a ("mm: split off __bdi_set_max_ratio() function") Signed-off-by: Jingbo Xu <[email protected]> Cc: Joseph Qi <[email protected]> Cc: Matthew Wilcox (Oracle) <[email protected]> Cc: Stefan Roesch <[email protected]> Signed-off-by: Andrew Morton <[email protected]>
sydarn · Dec 29, 2023 · fa151a3 · fa151a3
1 parent e0646b7
commit fa151a3
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
@@ -728,7 +728,8 @@ static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ra
 		ret = -EINVAL;
 	} else {
 		bdi->max_ratio = max_ratio;
-		bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
+		bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) /
+						(100 * BDI_RATIO_SCALE);
 	}
 	spin_unlock_bh(&bdi_lock);