On Fri, Mar 19, 2021 at 02:20:01PM +0100, Oscar Salvador wrote:

Currently, isolate_migratepages_{range,block} and their callers use
a pfn == 0 vs pfn != 0 scheme to let the caller know whether there was
any error during isolation.
This does not work as soon as we need to start reporting different error
codes and make sure we pass them down the chain, so they are properly
interpreted by functions like e.g: alloc_contig_range.

Let us rework isolate_migratepages_{range,block} so we can report error
codes.
Since isolate_migratepages_block will stop returning the next pfn to be
scanned, we reuse the cc->migrate_pfn field to keep track of that.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Vlastimil Babka <redacted>

Hi Andrew,

I realized a missed place wrt. error handling.
could you squash this on top?

diff --git a/mm/compaction.c b/mm/compaction.c
index cd090a675321..9b989fc3168d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c

@@ -809,6 +809,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 	bool skip_on_failure = false;
 	unsigned long next_skip_pfn = 0;
 	bool skip_updated = false;
+	int ret = 0;
 
 	cc->migrate_pfn = low_pfn;
 

@@ -877,8 +878,8 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 			if (fatal_signal_pending(current)) {
 				cc->contended = true;
+				ret = -EINTR;
 
-				low_pfn = 0;
 				goto fatal_pending;
 			}
 

@@ -1134,7 +1135,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 
 	cc->migrate_pfn = low_pfn;
 
-	return 0;
+	return ret;
 }

Thanks a lot

-- 
Oscar Salvador
SUSE L3