[GFS2] Streamline indirect pointer tree height calculation

This patch improves the calculation of the tree height in order to reduce
the number of operations which are carried out on each call to gfs2_block_map.
In the common case, we now make a single comparison, rather than calculating
the required tree height from scratch each time. Also in the case that the
tree does need some extra height, we start from the current height rather from
zero when we work out what the new height ought to be.

In addition the di_height field is moved into the inode proper and reduced
in size to a u8 since the value must be between 0 and GFS2_MAX_META_HEIGHT (10).

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 37 insertions, 71 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index a25444ac648b..5a3187049dd7 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -166,7 +166,7 @@ int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page)
 		di->di_blocks = cpu_to_be64(ip->i_di.di_blocks);
 	}
 
-	ip->i_di.di_height = 1;
+	ip->i_height = 1;
 	di->di_height = cpu_to_be16(1);
 
 out_brelse:
@@ -177,43 +177,6 @@ out:
 }
 
 /**
- * calc_tree_height - Calculate the height of a metadata tree
- * @ip: The GFS2 inode
- * @size: The proposed size of the file
- *
- * Work out how tall a metadata tree needs to be in order to accommodate a
- * file of a particular size. If size is less than the current size of
- * the inode, then the current size of the inode is used instead of the
- * supplied one.
- *
- * Returns: the height the tree should be
- */
-
-static unsigned int calc_tree_height(struct gfs2_inode *ip, u64 size)
-{
-	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-	u64 *arr;
-	unsigned int max, height;
-
-	if (ip->i_di.di_size > size)
-		size = ip->i_di.di_size;
-
-	if (gfs2_is_dir(ip)) {
-		arr = sdp->sd_jheightsize;
-		max = sdp->sd_max_jheight;
-	} else {
-		arr = sdp->sd_heightsize;
-		max = sdp->sd_max_height;
-	}
-
-	for (height = 0; height < max; height++)
-		if (arr[height] >= size)
-			break;
-
-	return height;
-}
-
-/**
  * build_height - Build a metadata tree of the requested height
  * @ip: The GFS2 inode
  * @height: The height to build to
@@ -225,7 +188,7 @@ static unsigned int calc_tree_height(struct gfs2_inode *ip, u64 size)
 static int build_height(struct inode *inode, unsigned height)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
-	unsigned new_height = height - ip->i_di.di_height;
+	unsigned new_height = height - ip->i_height;
 	struct buffer_head *dibh;
 	struct buffer_head *blocks[GFS2_MAX_META_HEIGHT];
 	struct gfs2_dinode *di;
@@ -234,7 +197,7 @@ static int build_height(struct inode *inode, unsigned height)
 	u64 bn;
 	unsigned n;
 
-	if (height <= ip->i_di.di_height)
+	if (height <= ip->i_height)
 		return 0;
 
 	error = gfs2_meta_inode_buffer(ip, &dibh);
@@ -270,10 +233,10 @@ static int build_height(struct inode *inode, unsigned height)
 	di = (struct gfs2_dinode *)dibh->b_data;
 	gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
 	*(__be64 *)(di + 1) = cpu_to_be64(bn);
-	ip->i_di.di_height += new_height;
+	ip->i_height += new_height;
 	ip->i_di.di_blocks += new_height;
 	gfs2_set_inode_blocks(&ip->i_inode);
-	di->di_height = cpu_to_be16(ip->i_di.di_height);
+	di->di_height = cpu_to_be16(ip->i_height);
 	di->di_blocks = cpu_to_be64(ip->i_di.di_blocks);
 	brelse(dibh);
 	return error;
@@ -345,7 +308,7 @@ static void find_metapath(struct gfs2_inode *ip, u64 block,
 	u64 b = block;
 	unsigned int i;
 
-	for (i = ip->i_di.di_height; i--;)
+	for (i = ip->i_height; i--;)
 		mp->mp_list[i] = do_div(b, sdp->sd_inptrs);
 
 }
@@ -407,7 +370,7 @@ static int lookup_block(struct gfs2_inode *ip, struct buffer_head *bh,
 	if (!create)
 		return 0;
 
-	if (height == ip->i_di.di_height - 1 && !gfs2_is_dir(ip))
+	if (height == ip->i_height - 1 && !gfs2_is_dir(ip))
 		*block = gfs2_alloc_data(ip);
 	else
 		*block = gfs2_alloc_meta(ip);
@@ -458,8 +421,7 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
 	struct buffer_head *bh;
-	unsigned int bsize;
-	unsigned int height;
+	unsigned int bsize = sdp->sd_sb.sb_bsize;
 	unsigned int end_of_metadata;
 	unsigned int x;
 	int error = 0;
@@ -470,7 +432,7 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
 	struct metapath mp;
 	u64 size;
 	struct buffer_head *dibh = NULL;
-
+	const u64 *arr = sdp->sd_heightsize;
 	BUG_ON(maxlen == 0);
 
 	if (gfs2_assert_warn(sdp, !gfs2_is_stuffed(ip)))
@@ -480,23 +442,25 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
 	clear_buffer_mapped(bh_map);
 	clear_buffer_new(bh_map);
 	clear_buffer_boundary(bh_map);
-	bsize = gfs2_is_dir(ip) ? sdp->sd_jbsize : sdp->sd_sb.sb_bsize;
+	if (gfs2_is_dir(ip)) {
+		bsize = sdp->sd_jbsize;
+		arr = sdp->sd_jheightsize;
+	}
 	size = (lblock + 1) * bsize;
 
-	if (size > ip->i_di.di_size) {
-		height = calc_tree_height(ip, size);
-		if (ip->i_di.di_height < height) {
-			if (!create)
-				goto out_ok;
-	
-			error = build_height(inode, height);
-			if (error)
-				goto out_fail;
-		}
+	if (size > arr[ip->i_height]) {
+		u8 height = ip->i_height;
+		if (!create)
+			goto out_ok;
+		while (size > arr[height])
+			height++;
+		error = build_height(inode, height);
+		if (error)
+			goto out_fail;
 	}
 
 	find_metapath(ip, lblock, &mp);
-	end_of_metadata = ip->i_di.di_height - 1;
+	end_of_metadata = ip->i_height - 1;
 	error = gfs2_meta_inode_buffer(ip, &bh);
 	if (error)
 		goto out_fail;
@@ -624,7 +588,7 @@ static int recursive_scan(struct gfs2_inode *ip, struct buffer_head *dibh,
 	if (error)
 		goto out;
 
-	if (height < ip->i_di.di_height - 1)
+	if (height < ip->i_height - 1)
 		for (; top < bottom; top++, first = 0) {
 			if (!*top)
 				continue;
@@ -682,7 +646,7 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
 		sm->sm_first = 0;
 	}
 
-	metadata = (height != ip->i_di.di_height - 1);
+	metadata = (height != ip->i_height - 1);
 	if (metadata)
 		revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;
 
@@ -807,7 +771,6 @@ static int do_grow(struct gfs2_inode *ip, u64 size)
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct gfs2_alloc *al;
 	struct buffer_head *dibh;
-	unsigned int h;
 	int error;
 
 	al = gfs2_alloc_get(ip);
@@ -833,20 +796,23 @@ static int do_grow(struct gfs2_inode *ip, u64 size)
 		goto out_ipres;
 
 	if (size > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)) {
+		const u64 *arr = sdp->sd_heightsize;
 		if (gfs2_is_stuffed(ip)) {
 			error = gfs2_unstuff_dinode(ip, NULL);
 			if (error)
 				goto out_end_trans;
 		}
 
-		h = calc_tree_height(ip, size);
-		if (ip->i_di.di_height < h) {
-			down_write(&ip->i_rw_mutex);
-			error = build_height(&ip->i_inode, h);
-			up_write(&ip->i_rw_mutex);
-			if (error)
-				goto out_end_trans;
+		down_write(&ip->i_rw_mutex);
+		if (size > arr[ip->i_height]) {
+			u8 height = ip->i_height;
+			while(size > arr[height])
+				height++;
+			error = build_height(&ip->i_inode, height);
 		}
+		up_write(&ip->i_rw_mutex);
+		if (error)
+			goto out_end_trans;
 	}
 
 	ip->i_di.di_size = size;
@@ -989,7 +955,7 @@ out:
 
 static int trunc_dealloc(struct gfs2_inode *ip, u64 size)
 {
-	unsigned int height = ip->i_di.di_height;
+	unsigned int height = ip->i_height;
 	u64 lblock;
 	struct metapath mp;
 	int error;
@@ -1040,7 +1006,7 @@ static int trunc_end(struct gfs2_inode *ip)
 		goto out;
 
 	if (!ip->i_di.di_size) {
-		ip->i_di.di_height = 0;
+		ip->i_height = 0;
 		ip->i_di.di_goal_meta =
 			ip->i_di.di_goal_data =
 			ip->i_no_addr;