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-rw-r--r--include/linux/idr.h7
1 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/idr.h b/include/linux/idr.h
index e968db71e33a..88607523e2df 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -117,10 +117,13 @@ void idr_init(struct idr *idp);
/*
* IDA - IDR based id allocator, use when translation from id to
* pointer isn't necessary.
+ *
+ * IDA_BITMAP_LONGS is calculated to be one less to accommodate
+ * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
*/
#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
-#define IDA_BITMAP_LONGS (128 / sizeof(long) - 1)
-#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
+#define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
+#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
struct ida_bitmap {
long nr_busy;