ext4: optimize starting extent in ext4_ext_rm_leaf()

Both hole punch and truncate use ext4_ext_rm_leaf() for removing
blocks.  Currently we choose the last extent as the starting
point for removing blocks:

	ex = EXT_LAST_EXTENT(eh);

This is OK for truncate but for hole punch we can optimize the extent
selection as the path is already initialized.  We could use this
information to select proper starting extent.  The code change in this
patch will not affect truncate as for truncate path[depth].p_ext will
always be NULL.

Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 575faa09025381ad9ba92d4bc1e93673a2bd0dde..7097b0f680e62bbf674364008ef66887a5e0fdca 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2504,7 +2504,9 @@ ext4_ext_rm_leaf(handle_t *handle, struct inode *inode,
                return -EIO;
        }
        /* find where to start removing */
-       ex = EXT_LAST_EXTENT(eh);
+       ex = path[depth].p_ext;
+       if (!ex)
+               ex = EXT_LAST_EXTENT(eh);
 
        ex_ee_block = le32_to_cpu(ex->ee_block);
        ex_ee_len = ext4_ext_get_actual_len(ex);