Increase the number of caller memory storage slots from 2 or 4 to

MEMSTAT_MAXCALLER (8), and expose MEMSTAT_MAXCALLER via memstat.h so
that applications can check their assumptions about how many slots
are available.

Remove 'spare' memory storage in struct malloc_type, since we now
don't expose the data structure internals to applications and rely
on accessor methods, this approach to ABI stability isn't required.

MFC after:	7 days

2 files changed, 12 insertions, 8 deletions

diff --git a/lib/libmemstat/memstat.h b/lib/libmemstat/memstat.h
index 847719c83052..5269a33be714 100644
--- a/lib/libmemstat/memstat.h
+++ b/lib/libmemstat/memstat.h
@@ -36,6 +36,14 @@
 #define	MEMSTAT_MAXCPU	16
 
 /*
+ * Amount of caller data to maintain for each caller data slot.  Applications
+ * must not request more than this number of caller save data, or risk
+ * corrupting internal libmemstat(3) data structures.  A compile time check
+ * in the application is probably appropriate.
+ */
+#define	MEMSTAT_MAXCALLER	8
+
+/*
  * libmemstat(3) is able to extract memory data from different allocators;
  * when it does so, it tags which allocator it got the data from so that
  * consumers can determine which fields are usable, as data returned varies
diff --git a/lib/libmemstat/memstat_internal.h b/lib/libmemstat/memstat_internal.h
index 94319177c373..1e974df06d7d 100644
--- a/lib/libmemstat/memstat_internal.h
+++ b/lib/libmemstat/memstat_internal.h
@@ -65,13 +65,12 @@ struct memory_type {
 	uint64_t	 mt_count;	/* Number of current allocations. */
 	uint64_t	 mt_free;	/* Number of cached free items. */
 	uint64_t	 mt_failures;	/* Number of allocation failures. */
-	uint64_t	 _mt_spare_uint64[4];	/* Spare. */
 
 	/*
 	 * Caller-owned memory.
 	 */
-	void		*mt_caller_pointer[4];	/* Caller-owned pointers. */
-	uint64_t	 mt_caller_uint64[4];	/* Caller-owned longs. */
+	void		*mt_caller_pointer[MEMSTAT_MAXCALLER];	/* Pointers. */
+	uint64_t	 mt_caller_uint64[MEMSTAT_MAXCALLER];	/* Integers. */
 
 	/*
 	 * For allocators making use of per-CPU caches, we also provide raw
@@ -86,7 +85,6 @@ struct memory_type {
 	 * global stats above.
 	 */
 	uint64_t	 mt_zonefree;	/* Free items in zone. */
-	uint64_t	 _mt_spare_uint642[4];	/* Spare. */
 
 	/*
 	 * Per-CPU measurements fall into two categories: per-CPU allocation,
@@ -98,14 +96,12 @@ struct memory_type {
 		uint64_t	 mtp_numallocs;	/* Per-CPU mt_numallocs. */
 		uint64_t	 mtp_numfrees;	/* Per-CPU mt_numfrees. */
 		uint64_t	 mtp_sizemask;	/* Per-CPU mt_sizemask. */
-		void		*mtp_caller_pointer[2];	/* Caller data. */
-		uint64_t	 mtp_caller_uint64[2];	/* Caller data. */
-		uint64_t	 _mtp_spare_uint64[3];	/* Per-CPU spare. */
+		void		*mtp_caller_pointer[MEMSTAT_MAXCALLER];
+		uint64_t	 mtp_caller_uint64[MEMSTAT_MAXCALLER];
 	}	mt_percpu_alloc[MEMSTAT_MAXCPU];
 
 	struct {
 		uint64_t	 mtp_free;	/* Per-CPU cache free items. */
-		uint64_t	 _mtp_spare_uint64[3];	/* Per-CPU spare. */
 	}	mt_percpu_cache[MEMSTAT_MAXCPU];
 
 	LIST_ENTRY(memory_type)	mt_list;	/* List of types. */