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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>
This commit is contained in:
Miaohe Lin 2022-04-29 14:40:43 +08:00 committed by akpm
parent 6cf9a34967
commit 4a1c383910
1 changed files with 3 additions and 3 deletions
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6
mm/z3fold.c
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@ -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 @@ next:
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)) {