[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 <[e-mail]>

fs/gfs2/bmap.c

···
 		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:
···
 out:
 	up_write(&ip->i_rw_mutex);
 	return error;
-}
-
-/**
- * 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;
 }
 
 /**
···
 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;
···
 	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);
···
 	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;
···
 	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);
 
 }
···
 	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);
···
 	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;
···
 	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)))
···
 	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;
···
 	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;
···
 		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;
 
···
 	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);
···
 		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;
···
 
 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;
···
 		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;

fs/gfs2/incore.h

···
 	u64 di_goal_data;	/* data block goal */
 	u64 di_generation;	/* generation number for NFS */
 	u32 di_flags;		/* GFS2_DIF_... */
-	u16 di_height;		/* height of metadata */
 	/* These only apply to directories  */
 	u16 di_depth;		/* Number of bits in the table */
 	u32 di_entries;		/* The number of entries in the directory */
···
 	u64 i_last_rg_alloc;
 
 	struct rw_semaphore i_rw_mutex;
+	u8 i_height;
 };
 
 /*
···
 	u32 sd_qc_per_block;
 	u32 sd_max_dirres;	/* Max blocks needed to add a directory entry */
 	u32 sd_max_height;	/* Max height of a file's metadata tree */
-	u64 sd_heightsize[GFS2_MAX_META_HEIGHT];
+	u64 sd_heightsize[GFS2_MAX_META_HEIGHT + 1];
 	u32 sd_max_jheight; /* Max height of journaled file's meta tree */
-	u64 sd_jheightsize[GFS2_MAX_META_HEIGHT];
+	u64 sd_jheightsize[GFS2_MAX_META_HEIGHT + 1];
 
 	struct gfs2_args sd_args;	/* Mount arguments */
 	struct gfs2_tune sd_tune;	/* Filesystem tuning structure */

fs/gfs2/inode.c

···
 {
 	struct gfs2_dinode_host *di = &ip->i_di;
 	const struct gfs2_dinode *str = buf;
+	u16 height;
 
-	if (ip->i_no_addr != be64_to_cpu(str->di_num.no_addr)) {
-		if (gfs2_consist_inode(ip))
-			gfs2_dinode_print(ip);
-		return -EIO;
-	}
+	if (unlikely(ip->i_no_addr != be64_to_cpu(str->di_num.no_addr)))
+		goto corrupt;
 	ip->i_no_formal_ino = be64_to_cpu(str->di_num.no_formal_ino);
 	ip->i_inode.i_mode = be32_to_cpu(str->di_mode);
 	ip->i_inode.i_rdev = 0;
···
 
 	di->di_flags = be32_to_cpu(str->di_flags);
 	gfs2_set_inode_flags(&ip->i_inode);
-	di->di_height = be16_to_cpu(str->di_height);
+	height = be16_to_cpu(str->di_height);
+	if (unlikely(height > GFS2_MAX_META_HEIGHT))
+		goto corrupt;
+	ip->i_height = (u8)height;
 
 	di->di_depth = be16_to_cpu(str->di_depth);
 	di->di_entries = be32_to_cpu(str->di_entries);
···
 		gfs2_set_aops(&ip->i_inode);
 
 	return 0;
+corrupt:
+	if (gfs2_consist_inode(ip))
+		gfs2_dinode_print(ip);
+	return -EIO;
 }
 
 /**
···
 	str->di_generation = cpu_to_be64(di->di_generation);
 
 	str->di_flags = cpu_to_be32(di->di_flags);
-	str->di_height = cpu_to_be16(di->di_height);
+	str->di_height = cpu_to_be16(ip->i_height);
 	str->di_payload_format = cpu_to_be32(S_ISDIR(ip->i_inode.i_mode) &&
 					     !(ip->i_di.di_flags & GFS2_DIF_EXHASH) ?
 					     GFS2_FORMAT_DE : 0);
···
 	printk(KERN_INFO "  di_goal_data = %llu\n",
 	       (unsigned long long)di->di_goal_data);
 	printk(KERN_INFO "  di_flags = 0x%.8X\n", di->di_flags);
-	printk(KERN_INFO "  di_height = %u\n", di->di_height);
 	printk(KERN_INFO "  di_depth = %u\n", di->di_depth);
 	printk(KERN_INFO "  di_entries = %u\n", di->di_entries);
 	printk(KERN_INFO "  di_eattr = %llu\n",

fs/gfs2/inode.h

···
 
 static inline int gfs2_is_stuffed(const struct gfs2_inode *ip)
 {
-	return !ip->i_di.di_height;
+	return !ip->i_height;
 }
 
 static inline int gfs2_is_jdata(const struct gfs2_inode *ip)

fs/gfs2/super.c

···
 		sdp->sd_heightsize[x] = space;
 	}
 	sdp->sd_max_height = x;
+	sdp->sd_heightsize[x] = ~0;
 	gfs2_assert(sdp, sdp->sd_max_height <= GFS2_MAX_META_HEIGHT);
 
 	sdp->sd_jheightsize[0] = sdp->sd_sb.sb_bsize -
···
 		sdp->sd_jheightsize[x] = space;
 	}
 	sdp->sd_max_jheight = x;
+	sdp->sd_jheightsize[x] = ~0;
 	gfs2_assert(sdp, sdp->sd_max_jheight <= GFS2_MAX_META_HEIGHT);
 
 	return 0;