xfs: make xfs btree stats less huge

Embedding a switch statement in every btree stats inc/add adds a lot
of code overhead to the core btree infrastructure paths. Stats are
supposed to be small and lightweight, but the btree stats have
become big and bloated as we've added more btrees. It needs fixing
because the reflink code will just add more overhead again.

Convert the v2 btree stats to arrays instead of independent
variables, and instead use the type to index the specific btree
array via an enum. This allows us to use array based indexing
to update the stats, rather than having to derefence variables
specific to the btree type.

If we then wrap the xfsstats structure in a union and place uint32_t
array beside it, and calculate the correct btree stats array base
array index when creating a btree cursor,  we can easily access
entries in the stats structure without having to switch names based
on the btree type.

We then replace with the switch statement with a simple set of stats
wrapper macros, resulting in a significant simplification of the
btree stats code, and:

   text	   data	    bss	    dec	    hex	filename
  48905	    144	      8	  49057	   bfa1	fs/xfs/libxfs/xfs_btree.o.old
  36793	    144	      8	  36945	   9051	fs/xfs/libxfs/xfs_btree.o

it reduces the core btree infrastructure code size by close to 25%!

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 4 insertions, 39 deletions

diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index c2b01d1c79ee..b69b947c4c1b 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -96,46 +96,10 @@ union xfs_btree_rec {
 /*
  * Generic stats interface
  */
-#define __XFS_BTREE_STATS_INC(mp, type, stat) \
-	XFS_STATS_INC(mp, xs_ ## type ## _2_ ## stat)
 #define XFS_BTREE_STATS_INC(cur, stat)	\
-do {    \
-	struct xfs_mount *__mp = cur->bc_mp; \
-	switch (cur->bc_btnum) {  \
-	case XFS_BTNUM_BNO: __XFS_BTREE_STATS_INC(__mp, abtb, stat); break; \
-	case XFS_BTNUM_CNT: __XFS_BTREE_STATS_INC(__mp, abtc, stat); break; \
-	case XFS_BTNUM_BMAP: __XFS_BTREE_STATS_INC(__mp, bmbt, stat); break; \
-	case XFS_BTNUM_INO: __XFS_BTREE_STATS_INC(__mp, ibt, stat); break; \
-	case XFS_BTNUM_FINO: __XFS_BTREE_STATS_INC(__mp, fibt, stat); break; \
-	case XFS_BTNUM_RMAP: __XFS_BTREE_STATS_INC(__mp, rmap, stat); break; \
-	case XFS_BTNUM_REFC: __XFS_BTREE_STATS_INC(__mp, refcbt, stat); break; \
-	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break;	\
-	}       \
-} while (0)
-
-#define __XFS_BTREE_STATS_ADD(mp, type, stat, val) \
-	XFS_STATS_ADD(mp, xs_ ## type ## _2_ ## stat, val)
-#define XFS_BTREE_STATS_ADD(cur, stat, val)  \
-do {    \
-	struct xfs_mount *__mp = cur->bc_mp; \
-	switch (cur->bc_btnum) {  \
-	case XFS_BTNUM_BNO:	\
-		__XFS_BTREE_STATS_ADD(__mp, abtb, stat, val); break; \
-	case XFS_BTNUM_CNT:	\
-		__XFS_BTREE_STATS_ADD(__mp, abtc, stat, val); break; \
-	case XFS_BTNUM_BMAP:	\
-		__XFS_BTREE_STATS_ADD(__mp, bmbt, stat, val); break; \
-	case XFS_BTNUM_INO:	\
-		__XFS_BTREE_STATS_ADD(__mp, ibt, stat, val); break; \
-	case XFS_BTNUM_FINO:	\
-		__XFS_BTREE_STATS_ADD(__mp, fibt, stat, val); break; \
-	case XFS_BTNUM_RMAP:	\
-		__XFS_BTREE_STATS_ADD(__mp, rmap, stat, val); break; \
-	case XFS_BTNUM_REFC:	\
-		__XFS_BTREE_STATS_ADD(__mp, refcbt, stat, val); break; \
-	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break; \
-	}       \
-} while (0)
+	XFS_STATS_INC_OFF((cur)->bc_mp, (cur)->bc_statoff + __XBTS_ ## stat)
+#define XFS_BTREE_STATS_ADD(cur, stat, val)	\
+	XFS_STATS_ADD_OFF((cur)->bc_mp, (cur)->bc_statoff + __XBTS_ ## stat, val)
 
 #define	XFS_BTREE_MAXLEVELS	9	/* max of all btrees */
 
@@ -253,6 +217,7 @@ typedef struct xfs_btree_cur
 	__uint8_t	bc_nlevels;	/* number of levels in the tree */
 	__uint8_t	bc_blocklog;	/* log2(blocksize) of btree blocks */
 	xfs_btnum_t	bc_btnum;	/* identifies which btree type */
+	int		bc_statoff;	/* offset of btre stats array */
 	union {
 		struct {			/* needed for BNO, CNT, INO */
 			struct xfs_buf	*agbp;	/* agf/agi buffer pointer */