[PATCH v14 15/20] mm/swap: serialize memcg changes during pagevec_lru_move_fn

Alex Shi
2020-07-03T05:09:30Z

Hugh Dickins' found a memcg change bug on original version:
If we want to change the pgdat->lru_lock to memcg's lruvec lock, we have
to serialize mem_cgroup_move_account during pagevec_lru_move_fn. The
possible bad scenario would like:

cpu 0 cpu 1
lruvec = mem_cgroup_page_lruvec()
if (!isolate_lru_page())
mem_cgroup_move_account

spin_lock_irqsave(&lruvec->lru_lock <== wrong lock.

So we need the ClearPageLRU to block isolate_lru_page(), then serialize
the memcg change here.

Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
mm/swap.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/mm/swap.c b/mm/swap.c
index b24d5f69b93a..55eb2c2eed03 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -203,7 +203,7 @@ int get_kernel_page(unsigned long start, int write, struct page **pages)
EXPORT_SYMBOL_GPL(get_kernel_page);

static void pagevec_lru_move_fn(struct pagevec *pvec,
- void (*move_fn)(struct page *page, struct lruvec *lruvec))
+ void (*move_fn)(struct page *page, struct lruvec *lruvec), bool add)
{
int i;
struct pglist_data *pgdat = NULL;
@@ -221,8 +221,15 @@ static void pagevec_lru_move_fn(struct pagevec *pvec,
spin_lock_irqsave(&pgdat->lru_lock, flags);
}

+ /* new page add to lru or page moving between lru */
+ if (!add && !TestClearPageLRU(page))
+ continue;
+
lruvec = mem_cgroup_page_lruvec(page, pgdat);
(*move_fn)(page, lruvec);
+
+ if (!add)
+ SetPageLRU(page);
}
if (pgdat)
spin_unlock_irqrestore(&pgdat->lru_lock, flags);
@@ -259,7 +266,7 @@ void rotate_reclaimable_page(struct page *page)
local_lock_irqsave(&lru_rotate.lock, flags);
pvec = this_cpu_ptr(&lru_rotate.pvec);
if (!pagevec_add(pvec, page) || PageCompound(page))
- pagevec_lru_move_fn(pvec, pagevec_move_tail_fn);
+ pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, false);
local_unlock_irqrestore(&lru_rotate.lock, flags);
}
}
@@ -328,7 +335,7 @@ static void activate_page_drain(int cpu)
struct pagevec *pvec = &per_cpu(lru_pvecs.activate_page, cpu);

if (pagevec_count(pvec))
- pagevec_lru_move_fn(pvec, __activate_page);
+ pagevec_lru_move_fn(pvec, __activate_page, false);
}

static bool need_activate_page_drain(int cpu)
@@ -346,7 +353,7 @@ void activate_page(struct page *page)
pvec = this_cpu_ptr(&lru_pvecs.activate_page);
get_page(page);
if (!pagevec_add(pvec, page) || PageCompound(page))
- pagevec_lru_move_fn(pvec, __activate_page);
+ pagevec_lru_move_fn(pvec, __activate_page, false);
local_unlock(&lru_pvecs.lock);
}
}
@@ -621,21 +628,21 @@ void lru_add_drain_cpu(int cpu)

/* No harm done if a racing interrupt already did this */
local_lock_irqsave(&lru_rotate.lock, flags);
- pagevec_lru_move_fn(pvec, pagevec_move_tail_fn);
+ pagevec_lru_move_fn(pvec, pagevec_move_tail_fn, false);
local_unlock_irqrestore(&lru_rotate.lock, flags);
}

pvec = &per_cpu(lru_pvecs.lru_deactivate_file, cpu);
if (pagevec_count(pvec))
- pagevec_lru_move_fn(pvec, lru_deactivate_file_fn);
+ pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, false);

pvec = &per_cpu(lru_pvecs.lru_deactivate, cpu);
if (pagevec_count(pvec))
- pagevec_lru_move_fn(pvec, lru_deactivate_fn);
+ pagevec_lru_move_fn(pvec, lru_deactivate_fn, false);

pvec = &per_cpu(lru_pvecs.lru_lazyfree, cpu);
if (pagevec_count(pvec))
- pagevec_lru_move_fn(pvec, lru_lazyfree_fn);
+ pagevec_lru_move_fn(pvec, lru_lazyfree_fn, false);

activate_page_drain(cpu);
}
@@ -664,7 +671,7 @@ void deactivate_file_page(struct page *page)
pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate_file);

if (!pagevec_add(pvec, page) || PageCompound(page))
- pagevec_lru_move_fn(pvec, lru_deactivate_file_fn);
+ pagevec_lru_move_fn(pvec, lru_deactivate_file_fn, false);
local_unlock(&lru_pvecs.lock);
}
}
@@ -686,7 +693,7 @@ void deactivate_page(struct page *page)
pvec = this_cpu_ptr(&lru_pvecs.lru_deactivate);
get_page(page);
if (!pagevec_add(pvec, page) || PageCompound(page))
- pagevec_lru_move_fn(pvec, lru_deactivate_fn);
+ pagevec_lru_move_fn(pvec, lru_deactivate_fn, false);
local_unlock(&lru_pvecs.lock);
}
}
@@ -708,7 +715,7 @@ void mark_page_lazyfree(struct page *page)
pvec = this_cpu_ptr(&lru_pvecs.lru_lazyfree);
get_page(page);
if (!pagevec_add(pvec, page) || PageCompound(page))
- pagevec_lru_move_fn(pvec, lru_lazyfree_fn);
+ pagevec_lru_move_fn(pvec, lru_lazyfree_fn, false);
local_unlock(&lru_pvecs.lock);
}
}
@@ -976,7 +983,7 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec)
*/
void __pagevec_lru_add(struct pagevec *pvec)
{
- pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn);
+ pagevec_lru_move_fn(pvec, __pagevec_lru_add_fn, true);
}

/**
--
1.8.3.1