Re: kernel BUG at include/linux/mm.h:1020!

[Mel Gorman <mgorman@techsingularity.net>]

On Mon, Mar 25, 2019 at 09:06:14PM +0500, Mikhail Gavrilov wrote:
> >         }
> > -
> > -       /* Leave no distance if no suitable block was reset */
> > -       if (reset_migrate >= reset_free) {
> > -               zone->compact_cached_migrate_pfn[0] = migrate_pfn;
> > -               zone->compact_cached_migrate_pfn[1] = migrate_pfn;
> > -               zone->compact_cached_free_pfn = free_pfn;
> > -       }
> >  }
> >
> >  void reset_isolation_suitable(pg_data_t *pgdat)
> >
> 
> Kernel panic are still occurs.
> 

Ok, thanks.

Trying one last time before putting together a debugging patch to see
exactly what PFNs are triggering as I still have not reproduced this on a
local machine. This is another replacement that is based on the assumption
that it's the free_pfn at the end of the zone that is triggering the
warning and it happens to be the case the end of a zone is aligned. Sorry
for the frustration with this and for persisting.

diff --git a/mm/compaction.c b/mm/compaction.c
index f171a83707ce..b4930bf93c8a 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -242,6 +242,7 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
 							bool check_target)
 {
 	struct page *page = pfn_to_online_page(pfn);
+	struct page *block_page;
 	struct page *end_page;
 	unsigned long block_pfn;
 
@@ -267,20 +268,26 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
 	    get_pageblock_migratetype(page) != MIGRATE_MOVABLE)
 		return false;
 
+	/* Ensure the start of the pageblock or zone is online and valid */
+	block_pfn = pageblock_start_pfn(pfn);
+	block_page = pfn_to_online_page(max(block_pfn, zone->zone_start_pfn));
+	if (block_page) {
+		page = block_page;
+		pfn = block_pfn;
+	}
+
+	/* Ensure the end of the pageblock or zone is online and valid */
+	block_pfn += pageblock_nr_pages;
+	block_pfn = min(block_pfn, zone_end_pfn(zone) - 1);
+	end_page = pfn_to_online_page(block_pfn);
+	if (!end_page)
+		return false;
+
 	/*
 	 * Only clear the hint if a sample indicates there is either a
 	 * free page or an LRU page in the block. One or other condition
 	 * is necessary for the block to be a migration source/target.
 	 */
-	block_pfn = pageblock_start_pfn(pfn);
-	pfn = max(block_pfn, zone->zone_start_pfn);
-	page = pfn_to_page(pfn);
-	if (zone != page_zone(page))
-		return false;
-	pfn = block_pfn + pageblock_nr_pages;
-	pfn = min(pfn, zone_end_pfn(zone));
-	end_page = pfn_to_page(pfn);
-
 	do {
 		if (pfn_valid_within(pfn)) {
 			if (check_source && PageLRU(page)) {
@@ -309,7 +316,7 @@ __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source,
 static void __reset_isolation_suitable(struct zone *zone)
 {
 	unsigned long migrate_pfn = zone->zone_start_pfn;
-	unsigned long free_pfn = zone_end_pfn(zone);
+	unsigned long free_pfn = zone_end_pfn(zone) - 1;
 	unsigned long reset_migrate = free_pfn;
 	unsigned long reset_free = migrate_pfn;
 	bool source_set = false;



-- 
Mel Gorman
SUSE Labs