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-rw-r--r--mm/zbud.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/mm/zbud.c b/mm/zbud.c
index f26e7fc..ecf1dbe 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;
}
/*****************
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