From 4a1c3839108afcfec02f4d62d6862b2451b442ab Mon Sep 17 00:00:00 2001
From: Miaohe Lin <linmiaohe@huawei.com>
Date: Fri, 29 Apr 2022 14:40:43 +0800
Subject: [PATCH] mm/z3fold: always clear PAGE_CLAIMED under z3fold page lock
Think about the below race window:
CPU1 CPU2
z3fold_reclaim_page z3fold_free
test_and_set_bit PAGE_CLAIMED
failed to reclaim page
z3fold_page_lock(zhdr);
add back to the lru list;
z3fold_page_unlock(zhdr);
get_z3fold_header
page_claimed=test_and_set_bit PAGE_CLAIMED
clear_bit(PAGE_CLAIMED, &page->private);
if (!page_claimed) /* it's false true */
free_handle is not called
free_handle won't be called in this case. So z3fold_buddy_slots will leak.
Fix it by always clear PAGE_CLAIMED under z3fold page lock.
Link: https://lkml.kernel.org/r/20220429064051.61552-8-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/z3fold.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index a1c150fc8def1..4a3cd2ff15b05 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -1221,8 +1221,8 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
return;
}
if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
- put_z3fold_header(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ put_z3fold_header(zhdr);
return;
}
if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
@@ -1424,8 +1424,8 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
spin_unlock(&pool->lock);
if (list_empty(&zhdr->buddy))
add_to_unbuddied(pool, zhdr);
- z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
}
/* We started off locked to we need to lock the pool back */
@@ -1577,8 +1577,8 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
if (!z3fold_page_trylock(zhdr))
return -EAGAIN;
if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
- z3fold_page_unlock(zhdr);
clear_bit(PAGE_CLAIMED, &page->private);
+ z3fold_page_unlock(zhdr);
return -EBUSY;
}
if (work_pending(&zhdr->work)) {
--
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