On Sat, Aug 18, 2018 at 4:22 AM, Matthew Wilcox [off-list ref] wrote:

On Fri, Aug 17, 2018 at 04:18:34PM -0700, Roman Gushchin wrote:

quoted

-                     scan = div64_u64(scan * fraction[file],
-                                      denominator);
+                     if (scan > 1)
+                             scan = div64_u64(scan * fraction[file],
+                                              denominator);

Wouldn't we be better off doing a div_round_up?  ie:

        scan = div64_u64(scan * fraction[file] + denominator - 1, denominator);

although i'd rather hide that in a new macro in math64.h than opencode it
here.

All numbers here should be up to nr_pages * 200 and fit into unsigned long.
I see no reason for u64. If they overflow then u64 wouldn't help either.

There is macro DIV_ROUND_UP in kernel.h