isolate_migratepages_block() used rcu_read_lock() with the intention
of safeguarding against the mem_cgroup being destroyed concurrently;
but its TestClearPageLRU already protects against that. Delete the
unnecessary rcu_read_lock() and _unlock().
Hugh Dickin' helped on commit log polishing, Thanks!
Signed-off-by: Alex Shi <alex....@linux.alibaba.com>
Acked-by: Hugh Dickins <hu...@google.com>
Cc: Hugh Dickins <hu...@google.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: linux...@kvack.org
Cc: linux-kernel@vger.kernel.org
---
mm/compaction.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 8049d3530812..02af220fb992 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -995,7 +995,6 @@ isolate_migratepages_block(struct compact_control *cc,
unsigned long low_pfn,
if (!TestClearPageLRU(page))
goto isolate_fail_put;
- rcu_read_lock();
lruvec = mem_cgroup_page_lruvec(page, pgdat);
/* If we already hold the lock, we can skip some rechecking */
@@ -1005,7 +1004,6 @@ isolate_migratepages_block(struct compact_control *cc,
unsigned long low_pfn,
compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
locked = lruvec;
- rcu_read_unlock();
lruvec_memcg_debug(lruvec, page);
@@ -1026,8 +1024,7 @@ isolate_migratepages_block(struct compact_control *cc,
unsigned long low_pfn,
SetPageLRU(page);
goto isolate_fail_put;
}
- } else
- rcu_read_unlock();
+ }
/* The whole page is taken off the LRU; skip the tail pages. */
if (PageCompound(page))
--
2.29.GIT
