Ocfs2: Optimize ocfs2 truncate to use ocfs2_remove_btree_range() instead.

Truncate is just a special case of punching holes(from new i_size to
end), we therefore could take advantage of the existing
ocfs2_remove_btree_range() to reduce the comlexity and redundancy in
alloc.c.  The goal here is to make truncate more generic and
straightforward.

Several functions only used by ocfs2_commit_truncate() will smiply be
removed.

ocfs2_remove_btree_range() was originally used by the hole punching
code, which didn't take refcount trees into account (definitely a bug).
We therefore need to change that func a bit to handle refcount trees.
It must take the refcount lock, calculate and reserve blocks for
refcount tree changes, and decrease refcounts at the end.  We replace 
ocfs2_lock_allocators() here by adding a new func
ocfs2_reserve_blocks_for_rec_trunc() which accepts some extra blocks to
reserve.  This will not hurt any other code using
ocfs2_remove_btree_range() (such as dir truncate and hole punching).

I merged the following steps into one patch since they may be
logically doing one thing, though I know it looks a little bit fat
to review.

1). Remove redundant code used by ocfs2_commit_truncate(), since we're
    moving to ocfs2_remove_btree_range anyway.

2). Add a new func ocfs2_reserve_blocks_for_rec_trunc() for purpose of
    accepting some extra blocks to reserve.

3). Change ocfs2_prepare_refcount_change_for_del() a bit to fit our
    needs.  It's safe to do this since it's only being called by
    truncate.

4). Change ocfs2_remove_btree_range() a bit to take refcount case into
    account.

5). Finally, we change ocfs2_commit_truncate() to call
    ocfs2_remove_btree_range() in a proper way.

The patch has been tested normally for sanity check, stress tests
with heavier workload will be expected.

Based on this patch, fixing the punching holes bug will be fairly easy.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 157 insertions, 528 deletions

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index 0cb2945eb817..0cb4248e03cd 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -5587,19 +5587,97 @@ out:
 	return ret;
 }
 
+/*
+ * ocfs2_reserve_blocks_for_rec_trunc() would look basically the
+ * same as ocfs2_lock_alloctors(), except for it accepts a blocks
+ * number to reserve some extra blocks, and it only handles meta
+ * data allocations.
+ *
+ * Currently, only ocfs2_remove_btree_range() uses it for truncating
+ * and punching holes.
+ */
+static int ocfs2_reserve_blocks_for_rec_trunc(struct inode *inode,
+					      struct ocfs2_extent_tree *et,
+					      u32 extents_to_split,
+					      struct ocfs2_alloc_context **ac,
+					      int extra_blocks)
+{
+	int ret = 0, num_free_extents;
+	unsigned int max_recs_needed = 2 * extents_to_split;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+
+	*ac = NULL;
+
+	num_free_extents = ocfs2_num_free_extents(osb, et);
+	if (num_free_extents < 0) {
+		ret = num_free_extents;
+		mlog_errno(ret);
+		goto out;
+	}
+
+	if (!num_free_extents ||
+	    (ocfs2_sparse_alloc(osb) && num_free_extents < max_recs_needed))
+		extra_blocks += ocfs2_extend_meta_needed(et->et_root_el);
+
+	if (extra_blocks) {
+		ret = ocfs2_reserve_new_metadata_blocks(osb, extra_blocks, ac);
+		if (ret < 0) {
+			if (ret != -ENOSPC)
+				mlog_errno(ret);
+			goto out;
+		}
+	}
+
+out:
+	if (ret) {
+		if (*ac) {
+			ocfs2_free_alloc_context(*ac);
+			*ac = NULL;
+		}
+	}
+
+	return ret;
+}
+
 int ocfs2_remove_btree_range(struct inode *inode,
 			     struct ocfs2_extent_tree *et,
-			     u32 cpos, u32 phys_cpos, u32 len,
-			     struct ocfs2_cached_dealloc_ctxt *dealloc)
+			     u32 cpos, u32 phys_cpos, u32 len, int flags,
+			     struct ocfs2_cached_dealloc_ctxt *dealloc,
+			     u64 refcount_loc)
 {
-	int ret;
+	int ret, credits = 0, extra_blocks = 0;
 	u64 phys_blkno = ocfs2_clusters_to_blocks(inode->i_sb, phys_cpos);
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 	struct inode *tl_inode = osb->osb_tl_inode;
 	handle_t *handle;
 	struct ocfs2_alloc_context *meta_ac = NULL;
+	struct ocfs2_refcount_tree *ref_tree = NULL;
+
+	if ((flags & OCFS2_EXT_REFCOUNTED) && len) {
+		BUG_ON(!(OCFS2_I(inode)->ip_dyn_features &
+			 OCFS2_HAS_REFCOUNT_FL));
+
+		ret = ocfs2_lock_refcount_tree(osb, refcount_loc, 1,
+					       &ref_tree, NULL);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		ret = ocfs2_prepare_refcount_change_for_del(inode,
+							    refcount_loc,
+							    phys_blkno,
+							    len,
+							    &credits,
+							    &extra_blocks);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+	}
 
-	ret = ocfs2_lock_allocators(inode, et, 0, 1, NULL, &meta_ac);
+	ret = ocfs2_reserve_blocks_for_rec_trunc(inode, et, 1, &meta_ac,
+						 extra_blocks);
 	if (ret) {
 		mlog_errno(ret);
 		return ret;
@@ -5615,7 +5693,8 @@ int ocfs2_remove_btree_range(struct inode *inode,
 		}
 	}
 
-	handle = ocfs2_start_trans(osb, ocfs2_remove_extent_credits(osb->sb));
+	handle = ocfs2_start_trans(osb,
+			ocfs2_remove_extent_credits(osb->sb) + credits);
 	if (IS_ERR(handle)) {
 		ret = PTR_ERR(handle);
 		mlog_errno(ret);
@@ -5642,9 +5721,20 @@ int ocfs2_remove_btree_range(struct inode *inode,
 
 	ocfs2_journal_dirty(handle, et->et_root_bh);
 
-	ret = ocfs2_truncate_log_append(osb, handle, phys_blkno, len);
-	if (ret)
-		mlog_errno(ret);
+	if (phys_blkno) {
+		if (flags & OCFS2_EXT_REFCOUNTED)
+			ret = ocfs2_decrease_refcount(inode, handle,
+					ocfs2_blocks_to_clusters(osb->sb,
+								 phys_blkno),
+					len, meta_ac,
+					dealloc, 1);
+		else
+			ret = ocfs2_truncate_log_append(osb, handle,
+							phys_blkno, len);
+		if (ret)
+			mlog_errno(ret);
+
+	}
 
 out_commit:
 	ocfs2_commit_trans(osb, handle);
@@ -5654,6 +5744,9 @@ out:
 	if (meta_ac)
 		ocfs2_free_alloc_context(meta_ac);
 
+	if (ref_tree)
+		ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
+
 	return ret;
 }
 
@@ -6481,417 +6574,6 @@ static int ocfs2_cache_extent_block_free(struct ocfs2_cached_dealloc_ctxt *ctxt,
 					 le16_to_cpu(eb->h_suballoc_bit));
 }
 
-/* This function will figure out whether the currently last extent
- * block will be deleted, and if it will, what the new last extent
- * block will be so we can update his h_next_leaf_blk field, as well
- * as the dinodes i_last_eb_blk */
-static int ocfs2_find_new_last_ext_blk(struct inode *inode,
-				       unsigned int clusters_to_del,
-				       struct ocfs2_path *path,
-				       struct buffer_head **new_last_eb)
-{
-	int next_free, ret = 0;
-	u32 cpos;
-	struct ocfs2_extent_rec *rec;
-	struct ocfs2_extent_block *eb;
-	struct ocfs2_extent_list *el;
-	struct buffer_head *bh = NULL;
-
-	*new_last_eb = NULL;
-
-	/* we have no tree, so of course, no last_eb. */
-	if (!path->p_tree_depth)
-		goto out;
-
-	/* trunc to zero special case - this makes tree_depth = 0
-	 * regardless of what it is.  */
-	if (OCFS2_I(inode)->ip_clusters == clusters_to_del)
-		goto out;
-
-	el = path_leaf_el(path);
-	BUG_ON(!el->l_next_free_rec);
-
-	/*
-	 * Make sure that this extent list will actually be empty
-	 * after we clear away the data. We can shortcut out if
-	 * there's more than one non-empty extent in the
-	 * list. Otherwise, a check of the remaining extent is
-	 * necessary.
-	 */
-	next_free = le16_to_cpu(el->l_next_free_rec);
-	rec = NULL;
-	if (ocfs2_is_empty_extent(&el->l_recs[0])) {
-		if (next_free > 2)
-			goto out;
-
-		/* We may have a valid extent in index 1, check it. */
-		if (next_free == 2)
-			rec = &el->l_recs[1];
-
-		/*
-		 * Fall through - no more nonempty extents, so we want
-		 * to delete this leaf.
-		 */
-	} else {
-		if (next_free > 1)
-			goto out;
-
-		rec = &el->l_recs[0];
-	}
-
-	if (rec) {
-		/*
-		 * Check it we'll only be trimming off the end of this
-		 * cluster.
-		 */
-		if (le16_to_cpu(rec->e_leaf_clusters) > clusters_to_del)
-			goto out;
-	}
-
-	ret = ocfs2_find_cpos_for_left_leaf(inode->i_sb, path, &cpos);
-	if (ret) {
-		mlog_errno(ret);
-		goto out;
-	}
-
-	ret = ocfs2_find_leaf(INODE_CACHE(inode), path_root_el(path), cpos, &bh);
-	if (ret) {
-		mlog_errno(ret);
-		goto out;
-	}
-
-	eb = (struct ocfs2_extent_block *) bh->b_data;
-	el = &eb->h_list;
-
-	/* ocfs2_find_leaf() gets the eb from ocfs2_read_extent_block().
-	 * Any corruption is a code bug. */
-	BUG_ON(!OCFS2_IS_VALID_EXTENT_BLOCK(eb));
-
-	*new_last_eb = bh;
-	get_bh(*new_last_eb);
-	mlog(0, "returning block %llu, (cpos: %u)\n",
-	     (unsigned long long)le64_to_cpu(eb->h_blkno), cpos);
-out:
-	brelse(bh);
-
-	return ret;
-}
-
-/*
- * Trim some clusters off the rightmost edge of a tree. Only called
- * during truncate.
- *
- * The caller needs to:
- *   - start journaling of each path component.
- *   - compute and fully set up any new last ext block
- */
-static int ocfs2_trim_tree(struct inode *inode, struct ocfs2_path *path,
-			   handle_t *handle, struct ocfs2_truncate_context *tc,
-			   u32 clusters_to_del, u64 *delete_start, u8 *flags)
-{
-	int ret, i, index = path->p_tree_depth;
-	u32 new_edge = 0;
-	u64 deleted_eb = 0;
-	struct buffer_head *bh;
-	struct ocfs2_extent_list *el;
-	struct ocfs2_extent_rec *rec;
-
-	*delete_start = 0;
-	*flags = 0;
-
-	while (index >= 0) {
-		bh = path->p_node[index].bh;
-		el = path->p_node[index].el;
-
-		mlog(0, "traveling tree (index = %d, block = %llu)\n",
-		     index,  (unsigned long long)bh->b_blocknr);
-
-		BUG_ON(le16_to_cpu(el->l_next_free_rec) == 0);
-
-		if (index !=
-		    (path->p_tree_depth - le16_to_cpu(el->l_tree_depth))) {
-			ocfs2_error(inode->i_sb,
-				    "Inode %lu has invalid ext. block %llu",
-				    inode->i_ino,
-				    (unsigned long long)bh->b_blocknr);
-			ret = -EROFS;
-			goto out;
-		}
-
-find_tail_record:
-		i = le16_to_cpu(el->l_next_free_rec) - 1;
-		rec = &el->l_recs[i];
-
-		mlog(0, "Extent list before: record %d: (%u, %u, %llu), "
-		     "next = %u\n", i, le32_to_cpu(rec->e_cpos),
-		     ocfs2_rec_clusters(el, rec),
-		     (unsigned long long)le64_to_cpu(rec->e_blkno),
-		     le16_to_cpu(el->l_next_free_rec));
-
-		BUG_ON(ocfs2_rec_clusters(el, rec) < clusters_to_del);
-
-		if (le16_to_cpu(el->l_tree_depth) == 0) {
-			/*
-			 * If the leaf block contains a single empty
-			 * extent and no records, we can just remove
-			 * the block.
-			 */
-			if (i == 0 && ocfs2_is_empty_extent(rec)) {
-				memset(rec, 0,
-				       sizeof(struct ocfs2_extent_rec));
-				el->l_next_free_rec = cpu_to_le16(0);
-
-				goto delete;
-			}
-
-			/*
-			 * Remove any empty extents by shifting things
-			 * left. That should make life much easier on
-			 * the code below. This condition is rare
-			 * enough that we shouldn't see a performance
-			 * hit.
-			 */
-			if (ocfs2_is_empty_extent(&el->l_recs[0])) {
-				le16_add_cpu(&el->l_next_free_rec, -1);
-
-				for(i = 0;
-				    i < le16_to_cpu(el->l_next_free_rec); i++)
-					el->l_recs[i] = el->l_recs[i + 1];
-
-				memset(&el->l_recs[i], 0,
-				       sizeof(struct ocfs2_extent_rec));
-
-				/*
-				 * We've modified our extent list. The
-				 * simplest way to handle this change
-				 * is to being the search from the
-				 * start again.
-				 */
-				goto find_tail_record;
-			}
-
-			le16_add_cpu(&rec->e_leaf_clusters, -clusters_to_del);
-
-			/*
-			 * We'll use "new_edge" on our way back up the
-			 * tree to know what our rightmost cpos is.
-			 */
-			new_edge = le16_to_cpu(rec->e_leaf_clusters);
-			new_edge += le32_to_cpu(rec->e_cpos);
-
-			/*
-			 * The caller will use this to delete data blocks.
-			 */
-			*delete_start = le64_to_cpu(rec->e_blkno)
-				+ ocfs2_clusters_to_blocks(inode->i_sb,
-					le16_to_cpu(rec->e_leaf_clusters));
-			*flags = rec->e_flags;
-
-			/*
-			 * If it's now empty, remove this record.
-			 */
-			if (le16_to_cpu(rec->e_leaf_clusters) == 0) {
-				memset(rec, 0,
-				       sizeof(struct ocfs2_extent_rec));
-				le16_add_cpu(&el->l_next_free_rec, -1);
-			}
-		} else {
-			if (le64_to_cpu(rec->e_blkno) == deleted_eb) {
-				memset(rec, 0,
-				       sizeof(struct ocfs2_extent_rec));
-				le16_add_cpu(&el->l_next_free_rec, -1);
-
-				goto delete;
-			}
-
-			/* Can this actually happen? */
-			if (le16_to_cpu(el->l_next_free_rec) == 0)
-				goto delete;
-
-			/*
-			 * We never actually deleted any clusters
-			 * because our leaf was empty. There's no
-			 * reason to adjust the rightmost edge then.
-			 */
-			if (new_edge == 0)
-				goto delete;
-
-			rec->e_int_clusters = cpu_to_le32(new_edge);
-			le32_add_cpu(&rec->e_int_clusters,
-				     -le32_to_cpu(rec->e_cpos));
-
-			 /*
-			  * A deleted child record should have been
-			  * caught above.
-			  */
-			 BUG_ON(le32_to_cpu(rec->e_int_clusters) == 0);
-		}
-
-delete:
-		ocfs2_journal_dirty(handle, bh);
-
-		mlog(0, "extent list container %llu, after: record %d: "
-		     "(%u, %u, %llu), next = %u.\n",
-		     (unsigned long long)bh->b_blocknr, i,
-		     le32_to_cpu(rec->e_cpos), ocfs2_rec_clusters(el, rec),
-		     (unsigned long long)le64_to_cpu(rec->e_blkno),
-		     le16_to_cpu(el->l_next_free_rec));
-
-		/*
-		 * We must be careful to only attempt delete of an
-		 * extent block (and not the root inode block).
-		 */
-		if (index > 0 && le16_to_cpu(el->l_next_free_rec) == 0) {
-			struct ocfs2_extent_block *eb =
-				(struct ocfs2_extent_block *)bh->b_data;
-
-			/*
-			 * Save this for use when processing the
-			 * parent block.
-			 */
-			deleted_eb = le64_to_cpu(eb->h_blkno);
-
-			mlog(0, "deleting this extent block.\n");
-
-			ocfs2_remove_from_cache(INODE_CACHE(inode), bh);
-
-			BUG_ON(ocfs2_rec_clusters(el, &el->l_recs[0]));
-			BUG_ON(le32_to_cpu(el->l_recs[0].e_cpos));
-			BUG_ON(le64_to_cpu(el->l_recs[0].e_blkno));
-
-			ret = ocfs2_cache_extent_block_free(&tc->tc_dealloc, eb);
-			/* An error here is not fatal. */
-			if (ret < 0)
-				mlog_errno(ret);
-		} else {
-			deleted_eb = 0;
-		}
-
-		index--;
-	}
-
-	ret = 0;
-out:
-	return ret;
-}
-
-static int ocfs2_do_truncate(struct ocfs2_super *osb,
-			     unsigned int clusters_to_del,
-			     struct inode *inode,
-			     struct buffer_head *fe_bh,
-			     handle_t *handle,
-			     struct ocfs2_truncate_context *tc,
-			     struct ocfs2_path *path,
-			     struct ocfs2_alloc_context *meta_ac)
-{
-	int status;
-	struct ocfs2_dinode *fe;
-	struct ocfs2_extent_block *last_eb = NULL;
-	struct ocfs2_extent_list *el;
-	struct buffer_head *last_eb_bh = NULL;
-	u64 delete_blk = 0;
-	u8 rec_flags;
-
-	fe = (struct ocfs2_dinode *) fe_bh->b_data;
-
-	status = ocfs2_find_new_last_ext_blk(inode, clusters_to_del,
-					     path, &last_eb_bh);
-	if (status < 0) {
-		mlog_errno(status);
-		goto bail;
-	}
-
-	/*
-	 * Each component will be touched, so we might as well journal
-	 * here to avoid having to handle errors later.
-	 */
-	status = ocfs2_journal_access_path(INODE_CACHE(inode), handle, path);
-	if (status < 0) {
-		mlog_errno(status);
-		goto bail;
-	}
-
-	if (last_eb_bh) {
-		status = ocfs2_journal_access_eb(handle, INODE_CACHE(inode), last_eb_bh,
-						 OCFS2_JOURNAL_ACCESS_WRITE);
-		if (status < 0) {
-			mlog_errno(status);
-			goto bail;
-		}
-
-		last_eb = (struct ocfs2_extent_block *) last_eb_bh->b_data;
-	}
-
-	el = &(fe->id2.i_list);
-
-	/*
-	 * Lower levels depend on this never happening, but it's best
-	 * to check it up here before changing the tree.
-	 */
-	if (el->l_tree_depth && el->l_recs[0].e_int_clusters == 0) {
-		ocfs2_error(inode->i_sb,
-			    "Inode %lu has an empty extent record, depth %u\n",
-			    inode->i_ino, le16_to_cpu(el->l_tree_depth));
-		status = -EROFS;
-		goto bail;
-	}
-
-	dquot_free_space_nodirty(inode,
-			ocfs2_clusters_to_bytes(osb->sb, clusters_to_del));
-	spin_lock(&OCFS2_I(inode)->ip_lock);
-	OCFS2_I(inode)->ip_clusters = le32_to_cpu(fe->i_clusters) -
-				      clusters_to_del;
-	spin_unlock(&OCFS2_I(inode)->ip_lock);
-	le32_add_cpu(&fe->i_clusters, -clusters_to_del);
-	inode->i_blocks = ocfs2_inode_sector_count(inode);
-
-	status = ocfs2_trim_tree(inode, path, handle, tc,
-				 clusters_to_del, &delete_blk, &rec_flags);
-	if (status) {
-		mlog_errno(status);
-		goto bail;
-	}
-
-	if (le32_to_cpu(fe->i_clusters) == 0) {
-		/* trunc to zero is a special case. */
-		el->l_tree_depth = 0;
-		fe->i_last_eb_blk = 0;
-	} else if (last_eb)
-		fe->i_last_eb_blk = last_eb->h_blkno;
-
-	ocfs2_journal_dirty(handle, fe_bh);
-
-	if (last_eb) {
-		/* If there will be a new last extent block, then by
-		 * definition, there cannot be any leaves to the right of
-		 * him. */
-		last_eb->h_next_leaf_blk = 0;
-		ocfs2_journal_dirty(handle, last_eb_bh);
-	}
-
-	if (delete_blk) {
-		if (rec_flags & OCFS2_EXT_REFCOUNTED)
-			status = ocfs2_decrease_refcount(inode, handle,
-					ocfs2_blocks_to_clusters(osb->sb,
-								 delete_blk),
-					clusters_to_del, meta_ac,
-					&tc->tc_dealloc, 1);
-		else
-			status = ocfs2_truncate_log_append(osb, handle,
-							   delete_blk,
-							   clusters_to_del);
-		if (status < 0) {
-			mlog_errno(status);
-			goto bail;
-		}
-	}
-	status = 0;
-bail:
-	brelse(last_eb_bh);
-	mlog_exit(status);
-	return status;
-}
-
 static int ocfs2_zero_func(handle_t *handle, struct buffer_head *bh)
 {
 	set_buffer_uptodate(bh);
@@ -7300,26 +6982,29 @@ out:
  */
 int ocfs2_commit_truncate(struct ocfs2_super *osb,
 			  struct inode *inode,
-			  struct buffer_head *fe_bh,
-			  struct ocfs2_truncate_context *tc)
+			  struct buffer_head *di_bh)
 {
-	int status, i, credits, tl_sem = 0;
-	u32 clusters_to_del, new_highest_cpos, range;
+	int status = 0, i, flags = 0;
+	u32 new_highest_cpos, range, trunc_cpos, trunc_len, phys_cpos, coff;
 	u64 blkno = 0;
 	struct ocfs2_extent_list *el;
-	handle_t *handle = NULL;
-	struct inode *tl_inode = osb->osb_tl_inode;
+	struct ocfs2_extent_rec *rec;
 	struct ocfs2_path *path = NULL;
-	struct ocfs2_dinode *di = (struct ocfs2_dinode *)fe_bh->b_data;
-	struct ocfs2_alloc_context *meta_ac = NULL;
-	struct ocfs2_refcount_tree *ref_tree = NULL;
+	struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;
+	struct ocfs2_extent_list *root_el = &(di->id2.i_list);
+	u64 refcount_loc = le64_to_cpu(di->i_refcount_loc);
+	struct ocfs2_extent_tree et;
+	struct ocfs2_cached_dealloc_ctxt dealloc;
 
 	mlog_entry_void();
 
+	ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode), di_bh);
+	ocfs2_init_dealloc_ctxt(&dealloc);
+
 	new_highest_cpos = ocfs2_clusters_for_bytes(osb->sb,
 						     i_size_read(inode));
 
-	path = ocfs2_new_path(fe_bh, &di->id2.i_list,
+	path = ocfs2_new_path(di_bh, &di->id2.i_list,
 			      ocfs2_journal_access_di);
 	if (!path) {
 		status = -ENOMEM;
@@ -7338,8 +7023,6 @@ start:
 		goto bail;
 	}
 
-	credits = 0;
-
 	/*
 	 * Truncate always works against the rightmost tree branch.
 	 */
@@ -7374,101 +7057,62 @@ start:
 	}
 
 	i = le16_to_cpu(el->l_next_free_rec) - 1;
-	range = le32_to_cpu(el->l_recs[i].e_cpos) +
-		ocfs2_rec_clusters(el, &el->l_recs[i]);
-	if (i == 0 && ocfs2_is_empty_extent(&el->l_recs[i])) {
-		clusters_to_del = 0;
-	} else if (le32_to_cpu(el->l_recs[i].e_cpos) >= new_highest_cpos) {
-		clusters_to_del = ocfs2_rec_clusters(el, &el->l_recs[i]);
-		blkno = le64_to_cpu(el->l_recs[i].e_blkno);
+	rec = &el->l_recs[i];
+	flags = rec->e_flags;
+	range = le32_to_cpu(rec->e_cpos) + ocfs2_rec_clusters(el, rec);
+
+	if (i == 0 && ocfs2_is_empty_extent(rec)) {
+		/*
+		 * Lower levels depend on this never happening, but it's best
+		 * to check it up here before changing the tree.
+		*/
+		if (root_el->l_tree_depth && rec->e_int_clusters == 0) {
+			ocfs2_error(inode->i_sb, "Inode %lu has an empty "
+				    "extent record, depth %u\n", inode->i_ino,
+				    le16_to_cpu(root_el->l_tree_depth));
+			status = -EROFS;
+			goto bail;
+		}
+		trunc_cpos = le32_to_cpu(rec->e_cpos);
+		trunc_len = 0;
+		blkno = 0;
+	} else if (le32_to_cpu(rec->e_cpos) >= new_highest_cpos) {
+		/*
+		 * Truncate entire record.
+		 */
+		trunc_cpos = le32_to_cpu(rec->e_cpos);
+		trunc_len = ocfs2_rec_clusters(el, rec);
+		blkno = le64_to_cpu(rec->e_blkno);
 	} else if (range > new_highest_cpos) {
-		clusters_to_del = (ocfs2_rec_clusters(el, &el->l_recs[i]) +
-				   le32_to_cpu(el->l_recs[i].e_cpos)) -
-				  new_highest_cpos;
-		blkno = le64_to_cpu(el->l_recs[i].e_blkno) +
-			ocfs2_clusters_to_blocks(inode->i_sb,
-				ocfs2_rec_clusters(el, &el->l_recs[i]) -
-				clusters_to_del);
+		/*
+		 * Partial truncate. it also should be
+		 * the last truncate we're doing.
+		 */
+		trunc_cpos = new_highest_cpos;
+		trunc_len = range - new_highest_cpos;
+		coff = new_highest_cpos - le32_to_cpu(rec->e_cpos);
+		blkno = le64_to_cpu(rec->e_blkno) +
+				ocfs2_clusters_to_blocks(inode->i_sb, coff);
 	} else {
+		/*
+		 * Truncate completed, leave happily.
+		 */
 		status = 0;
 		goto bail;
 	}
 
-	mlog(0, "clusters_to_del = %u in this pass, tail blk=%llu\n",
-	     clusters_to_del, (unsigned long long)path_leaf_bh(path)->b_blocknr);
-
-	if (el->l_recs[i].e_flags & OCFS2_EXT_REFCOUNTED && clusters_to_del) {
-		BUG_ON(!(OCFS2_I(inode)->ip_dyn_features &
-			 OCFS2_HAS_REFCOUNT_FL));
-
-		status = ocfs2_lock_refcount_tree(osb,
-						le64_to_cpu(di->i_refcount_loc),
-						1, &ref_tree, NULL);
-		if (status) {
-			mlog_errno(status);
-			goto bail;
-		}
-
-		status = ocfs2_prepare_refcount_change_for_del(inode, fe_bh,
-							       blkno,
-							       clusters_to_del,
-							       &credits,
-							       &meta_ac);
-		if (status < 0) {
-			mlog_errno(status);
-			goto bail;
-		}
-	}
-
-	mutex_lock(&tl_inode->i_mutex);
-	tl_sem = 1;
-	/* ocfs2_truncate_log_needs_flush guarantees us at least one
-	 * record is free for use. If there isn't any, we flush to get
-	 * an empty truncate log.  */
-	if (ocfs2_truncate_log_needs_flush(osb)) {
-		status = __ocfs2_flush_truncate_log(osb);
-		if (status < 0) {
-			mlog_errno(status);
-			goto bail;
-		}
-	}
-
-	credits += ocfs2_calc_tree_trunc_credits(osb->sb, clusters_to_del,
-						(struct ocfs2_dinode *)fe_bh->b_data,
-						el);
-	handle = ocfs2_start_trans(osb, credits);
-	if (IS_ERR(handle)) {
-		status = PTR_ERR(handle);
-		handle = NULL;
-		mlog_errno(status);
-		goto bail;
-	}
+	phys_cpos = ocfs2_blocks_to_clusters(inode->i_sb, blkno);
 
-	status = ocfs2_do_truncate(osb, clusters_to_del, inode, fe_bh, handle,
-				   tc, path, meta_ac);
+	status = ocfs2_remove_btree_range(inode, &et, trunc_cpos,
+					  phys_cpos, trunc_len, flags, &dealloc,
+					  refcount_loc);
 	if (status < 0) {
 		mlog_errno(status);
 		goto bail;
 	}
 
-	mutex_unlock(&tl_inode->i_mutex);
-	tl_sem = 0;
-
-	ocfs2_commit_trans(osb, handle);
-	handle = NULL;
-
 	ocfs2_reinit_path(path, 1);
 
-	if (meta_ac) {
-		ocfs2_free_alloc_context(meta_ac);
-		meta_ac = NULL;
-	}
-
-	if (ref_tree) {
-		ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
-		ref_tree = NULL;
-	}
-
 	/*
 	 * The check above will catch the case where we've truncated
 	 * away all allocation.
@@ -7479,25 +7123,10 @@ bail:
 
 	ocfs2_schedule_truncate_log_flush(osb, 1);
 
-	if (tl_sem)
-		mutex_unlock(&tl_inode->i_mutex);
-
-	if (handle)
-		ocfs2_commit_trans(osb, handle);
-
-	if (meta_ac)
-		ocfs2_free_alloc_context(meta_ac);
-
-	if (ref_tree)
-		ocfs2_unlock_refcount_tree(osb, ref_tree, 1);
-
-	ocfs2_run_deallocs(osb, &tc->tc_dealloc);
+	ocfs2_run_deallocs(osb, &dealloc);
 
 	ocfs2_free_path(path);
 
-	/* This will drop the ext_alloc cluster lock for us */
-	ocfs2_free_truncate_context(tc);
-
 	mlog_exit(status);
 	return status;
 }