[PATCH 1/2] EXT4: Punch Hole Optimizations: Skip un-needed extent lookup

[Allison Henderson <achender@linux.vnet.ibm.com>]

This patch optimizes the punch hole operation by skipping the
tree walking code that is used by truncate.  Since punch hole
is done through map blocks, the path to the extent is already
known in this function, so we do not need to look it up again.

Signed-off-by: Allison Henderson <achender@linux.vnet.ibm.com>
---
v2->v3
Rebased to apply onto latest ext4 code

:100644 100644 f815cc8... dc5a077... M	fs/ext4/extents.c
 fs/ext4/extents.c |   23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f815cc8..dc5a077 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3497,8 +3497,27 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 
 			ext4_ext_mark_uninitialized(ex);
 
-			err = ext4_ext_remove_space(inode, map->m_lblk,
-				map->m_lblk + punched_out);
+			ext4_ext_invalidate_cache(inode);
+
+			err = ext4_ext_rm_leaf(handle, inode, path,
+				map->m_lblk, map->m_lblk + punched_out);
+
+			if (!err && path->p_hdr->eh_entries == 0) {
+				/*
+				 * Punch hole freed all of this sub tree,
+				 * so we need to correct eh_depth
+				 */
+				err = ext4_ext_get_access(handle, inode, path);
+				if (err == 0) {
+					ext_inode_hdr(inode)->eh_depth = 0;
+					ext_inode_hdr(inode)->eh_max =
+					cpu_to_le16(ext4_ext_space_root(
+						inode, 0));
+
+					err = ext4_ext_dirty(
+						handle, inode, path);
+				}
+			}
 
 			goto out2;
 		}
-- 
1.7.1