[PATCH 4/4] xfs: use separate btree cursor slab for each btree type

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Now that we have the infrastructure to track the max possible height of
each btree type, we can create a separate slab zone for cursors of each
type of btree.  For smaller indices like the free space btrees, this
means that we can pack more cursors into a slab page, improving slab
utilization.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_btree.c |   12 ++++++------
 fs/xfs/libxfs/xfs_btree.h |    9 +--------
 fs/xfs/xfs_super.c        |   33 ++++++++++++++++++++++++---------
 3 files changed, 31 insertions(+), 23 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 120280c998f8..3131de9ae631 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -26,7 +26,6 @@
 /*
  * Cursor allocation zone.
  */
-kmem_zone_t	*xfs_btree_cur_zone;
 struct xfs_btree_cur_zone xfs_btree_cur_zones[XFS_BTNUM_MAX] = {
 	[XFS_BTNUM_BNO]		= { .name = "xfs_alloc_btree_cur" },
 	[XFS_BTNUM_INO]		= { .name = "xfs_ialloc_btree_cur" },
@@ -364,6 +363,7 @@ xfs_btree_del_cursor(
 	struct xfs_btree_cur	*cur,		/* btree cursor */
 	int			error)		/* del because of error */
 {
+	struct xfs_btree_cur_zone *bczone = &xfs_btree_cur_zones[cur->bc_btnum];
 	int			i;		/* btree level */
 
 	/*
@@ -386,10 +386,10 @@ xfs_btree_del_cursor(
 		kmem_free(cur->bc_ops);
 	if (!(cur->bc_flags & XFS_BTREE_LONG_PTRS) && cur->bc_ag.pag)
 		xfs_perag_put(cur->bc_ag.pag);
-	if (cur->bc_maxlevels > XFS_BTREE_CUR_ZONE_MAXLEVELS)
+	if (cur->bc_maxlevels > bczone->maxlevels)
 		kmem_free(cur);
 	else
-		kmem_cache_free(xfs_btree_cur_zone, cur);
+		kmem_cache_free(bczone->zone, cur);
 }
 
 /*
@@ -5021,12 +5021,12 @@ xfs_btree_alloc_cursor(
 {
 	struct xfs_btree_cur	*cur;
 	unsigned int		maxlevels = xfs_btree_maxlevels(mp, btnum);
+	struct xfs_btree_cur_zone *bczone = &xfs_btree_cur_zones[btnum];
 
-	if (maxlevels > XFS_BTREE_CUR_ZONE_MAXLEVELS)
+	if (maxlevels > bczone->maxlevels)
 		cur = kmem_zalloc(xfs_btree_cur_sizeof(maxlevels), KM_NOFS);
 	else
-		cur = kmem_cache_zalloc(xfs_btree_cur_zone,
-				GFP_NOFS | __GFP_NOFAIL);
+		cur = kmem_cache_zalloc(bczone->zone, GFP_NOFS | __GFP_NOFAIL);
 	cur->bc_tp = tp;
 	cur->bc_mp = mp;
 	cur->bc_btnum = btnum;
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 5bebd26f8b2c..854235a8adac 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -13,8 +13,6 @@ struct xfs_trans;
 struct xfs_ifork;
 struct xfs_perag;
 
-extern kmem_zone_t	*xfs_btree_cur_zone;
-
 /*
  * Generic key, ptr and record wrapper structures.
  *
@@ -92,12 +90,6 @@ uint32_t xfs_btree_magic(int crc, xfs_btnum_t btnum);
 #define XFS_BTREE_STATS_ADD(cur, stat, val)	\
 	XFS_STATS_ADD_OFF((cur)->bc_mp, (cur)->bc_statoff + __XBTS_ ## stat, val)
 
-/*
- * The btree cursor zone hands out cursors that can handle up to this many
- * levels.  This is the known maximum for all btree types.
- */
-#define XFS_BTREE_CUR_ZONE_MAXLEVELS	(9)
-
 struct xfs_btree_ops {
 	/* size of the key and record structures */
 	size_t	key_len;
@@ -588,6 +580,7 @@ void xfs_btree_absolute_minrecs(unsigned int *minrecs, unsigned int bc_flags,
 
 struct xfs_btree_cur_zone {
 	const char		*name;
+	kmem_zone_t		*zone;
 	unsigned int		maxlevels;
 };
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 83abe9bfe3ef..426dcba213ac 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1969,7 +1969,14 @@ xfs_init_btree_zones(void)
 	z[XFS_BTNUM_REFC].maxlevels	= xfs_refcountbt_absolute_maxlevels();
 
 	for_each_xfs_btnum(btnum) {
-		ASSERT(z[btnum].maxlevels <= XFS_BTREE_CUR_ZONE_MAXLEVELS);
+		if (z[btnum].name == NULL)
+			continue;
+		ASSERT(z[btnum].maxlevels >= 1);
+		z[btnum].zone = kmem_cache_create(z[btnum].name,
+				xfs_btree_cur_sizeof(z[btnum].maxlevels),
+				0, 0, NULL);
+		if (!z[btnum].zone)
+			return -ENOMEM;
 	}
 
 	/* struct copies for btree types that share zones */
@@ -1979,6 +1986,20 @@ xfs_init_btree_zones(void)
 	return 0;
 }
 
+STATIC void
+xfs_destroy_btree_zones(void)
+{
+	struct xfs_btree_cur_zone	*z = xfs_btree_cur_zones;
+	xfs_btnum_t			btnum;
+
+	/* don't free shared zones */
+	z[XFS_BTNUM_CNT].zone = NULL;
+	z[XFS_BTNUM_FINO].zone = NULL;
+
+	for_each_xfs_btnum(btnum)
+		kmem_cache_destroy(z[btnum].zone);
+}
+
 STATIC int __init
 xfs_init_zones(void)
 {
@@ -2000,12 +2021,6 @@ xfs_init_zones(void)
 	if (error)
 		goto out_destroy_bmap_free_item_zone;
 
-	xfs_btree_cur_zone = kmem_cache_create("xfs_btree_cur",
-			xfs_btree_cur_sizeof(XFS_BTREE_CUR_ZONE_MAXLEVELS),
-			0, 0, NULL);
-	if (!xfs_btree_cur_zone)
-		goto out_destroy_bmap_free_item_zone;
-
 	xfs_da_state_zone = kmem_cache_create("xfs_da_state",
 					      sizeof(struct xfs_da_state),
 					      0, 0, NULL);
@@ -2141,7 +2156,7 @@ xfs_init_zones(void)
  out_destroy_da_state_zone:
 	kmem_cache_destroy(xfs_da_state_zone);
  out_destroy_btree_cur_zone:
-	kmem_cache_destroy(xfs_btree_cur_zone);
+	xfs_destroy_btree_zones();
  out_destroy_bmap_free_item_zone:
 	kmem_cache_destroy(xfs_bmap_free_item_zone);
  out_destroy_log_ticket_zone:
@@ -2173,7 +2188,7 @@ xfs_destroy_zones(void)
 	kmem_cache_destroy(xfs_trans_zone);
 	kmem_cache_destroy(xfs_ifork_zone);
 	kmem_cache_destroy(xfs_da_state_zone);
-	kmem_cache_destroy(xfs_btree_cur_zone);
+	xfs_destroy_btree_zones();
 	kmem_cache_destroy(xfs_bmap_free_item_zone);
 	kmem_cache_destroy(xfs_log_ticket_zone);
 }