1 files changed, 32 insertions, 17 deletions

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91ae46098ea4..7d7b74e94687 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -296,29 +296,44 @@ static inline int ext4_ext_space_root_idx(struct inode *inode, int check)
  * to allocate @blocks
  * Worse case is one block per extent
  */
-int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks)
+int ext4_ext_calc_metadata_amount(struct inode *inode, sector_t lblock)
 {
-        int lcap, icap, rcap, leafs, idxs, num;
-        int newextents = blocks;
-
-        rcap = ext4_ext_space_root_idx(inode, 0);
-        lcap = ext4_ext_space_block(inode, 0);
-        icap = ext4_ext_space_block_idx(inode, 0);
+        struct ext4_inode_info *ei = EXT4_I(inode);
+        int idxs, num = 0;
 
-        /* number of new leaf blocks needed */
-        num = leafs = (newextents + lcap - 1) / lcap;
+        idxs = ((inode->i_sb->s_blocksize - sizeof(struct ext4_extent_header))
+                / sizeof(struct ext4_extent_idx));
 
         /*
-         * Worse case, we need separate index block(s)
-         * to link all new leaf blocks
+         * If the new delayed allocation block is contiguous with the
+         * previous da block, it can share index blocks with the
+         * previous block, so we only need to allocate a new index
+         * block every idxs leaf blocks.  At ldxs**2 blocks, we need
+         * an additional index block, and at ldxs**3 blocks, yet
+         * another index blocks.
          */
-        idxs = (leafs + icap - 1) / icap;
-        do {
-                num += idxs;
-                idxs = (idxs + icap - 1) / icap;
-        } while (idxs > rcap);
+        if (ei->i_da_metadata_calc_len &&
+            ei->i_da_metadata_calc_last_lblock+1 == lblock) {
+                if ((ei->i_da_metadata_calc_len % idxs) == 0)
+                        num++;
+                if ((ei->i_da_metadata_calc_len % (idxs*idxs)) == 0)
+                        num++;
+                if ((ei->i_da_metadata_calc_len % (idxs*idxs*idxs)) == 0) {
+                        num++;
+                        ei->i_da_metadata_calc_len = 0;
+                } else
+                        ei->i_da_metadata_calc_len++;
+                ei->i_da_metadata_calc_last_lblock++;
+                return num;
+        }
 
-        return num;
+        /*
+         * In the worst case we need a new set of index blocks at
+         * every level of the inode's extent tree.
+         */
+        ei->i_da_metadata_calc_len = 1;
+        ei->i_da_metadata_calc_last_lblock = lblock;
+        return ext_depth(inode) + 1;
 }
 
 static int