Commit be1aa03b authored by Joonsoo Kim's avatar Joonsoo Kim Committed by Linus Torvalds

mm/compaction: change the timing to check to drop the spinlock

It is odd to drop the spinlock when we scan (SWAP_CLUSTER_MAX - 1) th
pfn page.  This may results in below situation while isolating

1. try isolate 0x0 ~ 0x200 pfn pages.
2. When low_pfn is 0x1ff, ((low_pfn+1) % SWAP_CLUSTER_MAX) == 0, so drop
   the spinlock.
3. Then, to complete isolating, retry to aquire the lock.

I think that it is better to use SWAP_CLUSTER_MAX th pfn for checking the
criteria about dropping the lock.  This has no harm 0x0 pfn, because, at
this time, locked variable would be false.
Signed-off-by: default avatarJoonsoo Kim <>
Acked-by: default avatarVlastimil Babka <>
Cc: Mel Gorman <>
Cc: Rik van Riel <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 01ead534
......@@ -487,7 +487,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
for (; low_pfn < end_pfn; low_pfn++) {
/* give a chance to irqs before checking need_resched() */
if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {
if (should_release_lock(&zone->lru_lock)) {
spin_unlock_irqrestore(&zone->lru_lock, flags);
locked = false;
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