The patch titled
Subject: mm/compaction: remove rcu_read_lock during page compaction
has been added to the -mm tree. Its filename is
mm-compaction-remove-rcu_read_lock-during-page-compaction.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-remove-rcu_read_lock-during-page-compaction.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-remove-rcu_read_lock-during-page-compaction.patch
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------------------------------------------------------
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Subject: mm/compaction: remove rcu_read_lock during page compaction
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 Dickins helped on commit log polishing, Thanks!
Link: https://lkml.kernel.org/r/1608614453-10739-3-git-send-email-alex.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
--- a/mm/compaction.c~mm-compaction-remove-rcu_read_lock-during-page-compaction
+++ a/mm/compaction.c
@@ -995,7 +995,6 @@ isolate_migratepages_block(struct compac
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 compac
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 compac
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))
_
Patches currently in -mm which might be from alex.shi@xxxxxxxxxxxxxxxxx are
mm-memcg-revise-the-using-condition-of-lock_page_lruvec-function-series.patch
mm-memcg-remove-rcu-locking-for-lock_page_lruvec-function-series.patch
mm-vmscan-__isolate_lru_page_prepare-clean-up.patch
mm-compaction-remove-rcu_read_lock-during-page-compaction.patch
