1 files changed, 7 insertions, 6 deletions

diff --git a/mm/zbud.c b/mm/zbud.c
index f26e7fcc7fa2..ecf1dbef6983 100644
--- a/mm/zbud.c
+++ b/mm/zbud.c
@@ -60,15 +60,17 @@
  * NCHUNKS_ORDER determines the internal allocation granularity, effectively
  * adjusting internal fragmentation.  It also determines the number of
  * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
- * allocation granularity will be in chunks of size PAGE_SIZE/64, and there
- * will be 64 freelists per pool.
+ * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk
+ * in allocated page is occupied by zbud header, NCHUNKS will be calculated to
+ * 63 which shows the max number of free chunks in zbud page, also there will be
+ * 63 freelists per pool.
  */
 #define NCHUNKS_ORDER   6
 
 #define CHUNK_SHIFT     (PAGE_SHIFT - NCHUNKS_ORDER)
 #define CHUNK_SIZE      (1 << CHUNK_SHIFT)
-#define NCHUNKS         (PAGE_SIZE >> CHUNK_SHIFT)
 #define ZHDR_SIZE_ALIGNED CHUNK_SIZE
+#define NCHUNKS         ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
 
 /**
  * struct zbud_pool - stores metadata for each zbud pool
@@ -268,10 +270,9 @@ static int num_free_chunks(struct zbud_header *zhdr)
 {
         /*
          * Rather than branch for different situations, just use the fact that
-         * free buddies have a length of zero to simplify everything. -1 at the
-         * end for the zbud header.
+         * free buddies have a length of zero to simplify everything.
          */
-        return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks - 1;
+        return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
 }
 
 /*****************