zbud_alloc() incorrectly verifies the size of allocation limit. It
should deny the allocation request greater than (PAGE_SIZE -
ZHDR_SIZE_ALIGNED - CHUNK_SIZE), not (PAGE_SIZE - ZHDR_SIZE_ALIGNED)
which has no remaining spaces for its buddy. There is no point in
spending the entire zbud page storing only a single page, since we don't
have any benefits.

Signed-off-by: Heesub Shin <heesub.s...@samsung.com>
---
 mm/zbud.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/zbud.c b/mm/zbud.c
index 9bb4710..ad1e781 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -257,7 +257,7 @@ int zbud_alloc(struct zbud_pool *pool, int size, gfp_t gfp,
 
        if (size <= 0 || gfp & __GFP_HIGHMEM)
                return -EINVAL;
-       if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED)
+       if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
                return -ENOSPC;
        chunks = size_to_chunks(size);
        spin_lock(&pool->lock);
-- 
1.8.3.2

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