[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, 12 insertions, 8 deletions

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 37725ade3c51..ff66ab7a17c8 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -248,12 +248,10 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 {
         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;
@@ -290,7 +288,10 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
 
         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);
@@ -300,6 +301,10 @@ static int gfs2_dinode_in(struct gfs2_inode *ip, const void *buf)
                 gfs2_set_aops(&ip->i_inode);
 
         return 0;
+corrupt:
+        if (gfs2_consist_inode(ip))
+                gfs2_dinode_print(ip);
+        return -EIO;
 }
 
 /**
@@ -1401,7 +1406,7 @@ void gfs2_dinode_out(const struct gfs2_inode *ip, void *buf)
         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);
@@ -1430,7 +1435,6 @@ void gfs2_dinode_print(const struct gfs2_inode *ip)
         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",