On 06/29/2016 10:12 AM, Joonsoo Kim wrote:
@@ -1035,8 +1034,12 @@ static void isolate_freepages(struct com
continue;
/* Found a block suitable for isolating free pages from. */
- isolate_freepages_block(cc, &isolate_start_pfn,
- block_end_pfn, freelist, false);
+ isolated = isolate_freepages_block(cc, &isolate_start_pfn,
+ block_end_pfn, freelist, false);
+ /* If isolation failed early, do not continue needlessly */
+ if (!isolated && isolate_start_pfn < block_end_pfn &&
+ cc->nr_migratepages > cc->nr_freepages)
+ break;
Hello, David.
Minchan found the bug on this patch.
Was it reported in some mail to linux-mm before the patch was sent to
Linus, or just now?
isolate_freepages_block() could return positive number if it is
stopped due to memory shortage. In this case, above branch would not
catch this situation due to positive 'isolated' and go through the
Uh, right. It could have isolated something successfully and only then
fail to isolate some more, so isolated is non-zero. I've missed this
corner case in review :(
following code.
if ((cc->nr_freepages >= cc->nr_migratepages) || XXX)
else
VM_BUG_ON(isolate_start_pfn < block_end_pfn);
In this case, cc->nr_freepages could be lower than cc->nr_migratepages
and isolate_start_pfn < block_end_pfn so it triggers VM_BUG_ON().
If my analysis is correct, please fix it.
David?
Thanks.
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