diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
index f7b483f0de2a..d62010166c34 100644
--- a/fs/ocfs2/suballoc.c
+++ b/fs/ocfs2/suballoc.c
@@ -294,6 +294,68 @@ static int ocfs2_validate_group_descriptor(struct super_block *sb,
 	return ocfs2_validate_gd_self(sb, bh, 0);
 }
 
+/*
+ * hint gd may already be released in _ocfs2_free_suballoc_bits(),
+ * we first check gd descriptor signature, then do the
+ * ocfs2_read_group_descriptor() jobs.
+ *
+ * When the group descriptor is invalid, we return 'rc=0' and
+ * '*released=1'. The caller should handle this case. Otherwise,
+ * we return the real error code.
+ */
+static int ocfs2_read_hint_group_descriptor(struct inode *inode,
+			struct ocfs2_dinode *di, u64 gd_blkno,
+			struct buffer_head **bh, int *released)
+{
+	int rc;
+	struct buffer_head *tmp = *bh;
+	struct ocfs2_group_desc *gd;
+
+	*released = 0;
+
+	rc = ocfs2_read_block(INODE_CACHE(inode), gd_blkno, &tmp, NULL);
+	if (rc)
+		goto out;
+
+	gd = (struct ocfs2_group_desc *) tmp->b_data;
+	if (!OCFS2_IS_VALID_GROUP_DESC(gd)) {
+		/*
+		 * Invalid gd cache was set in ocfs2_read_block(),
+		 * which will affect block_group allocation.
+		 * Path:
+		 * ocfs2_reserve_suballoc_bits
+		 *  ocfs2_block_group_alloc
+		 *   ocfs2_block_group_alloc_contig
+		 *    ocfs2_set_new_buffer_uptodate
+		 */
+		ocfs2_remove_from_cache(INODE_CACHE(inode), tmp);
+		*released = 1; /* we return 'rc=0' for this case */
+		goto free_bh;
+	}
+
+	/* below jobs same with ocfs2_read_group_descriptor() */
+	if (!buffer_jbd(tmp)) {
+		rc = ocfs2_validate_group_descriptor(inode->i_sb, tmp);
+		if (rc)
+			goto free_bh;
+	}
+
+	rc = ocfs2_validate_gd_parent(inode->i_sb, di, tmp, 0);
+	if (rc)
+		goto free_bh;
+
+	/* If ocfs2_read_block() got us a new bh, pass it up. */
+	if (!*bh)
+		*bh = tmp;
+
+	return rc;
+
+free_bh:
+	brelse(tmp);
+out:
+	return rc;
+}
+
 int ocfs2_read_group_descriptor(struct inode *inode, struct ocfs2_dinode *di,
 				u64 gd_blkno, struct buffer_head **bh)
 {
@@ -1722,7 +1784,7 @@ static int ocfs2_search_one_group(struct ocfs2_alloc_context *ac,
 				  u32 bits_wanted,
 				  u32 min_bits,
 				  struct ocfs2_suballoc_result *res,
-				  u16 *bits_left)
+				  u16 *bits_left, int *released)
 {
 	int ret;
 	struct buffer_head *group_bh = NULL;
@@ -1730,9 +1792,11 @@ static int ocfs2_search_one_group(struct ocfs2_alloc_context *ac,
 	struct ocfs2_dinode *di = (struct ocfs2_dinode *)ac->ac_bh->b_data;
 	struct inode *alloc_inode = ac->ac_inode;
 
-	ret = ocfs2_read_group_descriptor(alloc_inode, di,
-					  res->sr_bg_blkno, &group_bh);
-	if (ret < 0) {
+	ret = ocfs2_read_hint_group_descriptor(alloc_inode, di,
+				res->sr_bg_blkno, &group_bh, released);
+	if (*released) {
+		return 0;
+	} else if (ret < 0) {
 		mlog_errno(ret);
 		return ret;
 	}
@@ -1934,7 +1998,7 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
 				     u32 min_bits,
 				     struct ocfs2_suballoc_result *res)
 {
-	int status;
+	int status, released;
 	u16 victim, i;
 	u16 bits_left = 0;
 	u64 hint = ac->ac_last_group;
@@ -1961,6 +2025,7 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
 		goto bail;
 	}
 
+	/* the hint bg may already be released, we quiet search this group. */
 	res->sr_bg_blkno = hint;
 	if (res->sr_bg_blkno) {
 		/* Attempt to short-circuit the usual search mechanism
@@ -1968,7 +2033,12 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
 		 * allocation group. This helps us maintain some
 		 * contiguousness across allocations. */
 		status = ocfs2_search_one_group(ac, handle, bits_wanted,
-						min_bits, res, &bits_left);
+						min_bits, res, &bits_left,
+						&released);
+		if (released) {
+			res->sr_bg_blkno = 0;
+			goto chain_search;
+		}
 		if (!status)
 			goto set_hint;
 		if (status < 0 && status != -ENOSPC) {
@@ -1976,7 +2046,7 @@ static int ocfs2_claim_suballoc_bits(struct ocfs2_alloc_context *ac,
 			goto bail;
 		}
 	}
-
+chain_search:
 	cl = (struct ocfs2_chain_list *) &fe->id2.i_chain;
 
 	victim = ocfs2_find_victim_chain(cl);
@@ -2077,6 +2147,12 @@ int ocfs2_claim_metadata(handle_t *handle,
 	return status;
 }
 
+/*
+ * after ocfs2 has the ability to release block group unused space,
+ * the ->ip_last_used_group may be invalid. so this function returns
+ * ac->ac_last_group need to verify.
+ * refer the 'hint' in ocfs2_claim_suballoc_bits() for more details.
+ */
 static void ocfs2_init_inode_ac_group(struct inode *dir,
 				      struct buffer_head *parent_di_bh,
 				      struct ocfs2_alloc_context *ac)
@@ -2514,6 +2590,197 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
 	return status;
 }
 
+/*
+ * Reclaim the suballocator managed space to main bitmap.
+ * This function first works on the suballocator then switch to the
+ * main bitmap.
+ *
+ * handle: The transaction handle
+ * alloc_inode: The suballoc inode
+ * alloc_bh: The buffer_head of suballoc inode
+ * group_bh: The group descriptor buffer_head of suballocator managed.
+ *           Caller should release the input group_bh.
+ */
+static int _reclaim_to_main_bm(handle_t *handle,
+			struct inode *alloc_inode,
+			struct buffer_head *alloc_bh,
+			struct buffer_head *group_bh)
+{
+	int idx, status = 0;
+	int i, next_free_rec, len = 0;
+	__le16 old_bg_contig_free_bits = 0;
+	u16 start_bit;
+	u32 tmp_used;
+	u64 bg_blkno, start_blk;
+	unsigned int count;
+	struct ocfs2_chain_rec *rec;
+	struct buffer_head *main_bm_bh = NULL;
+	struct inode *main_bm_inode = NULL;
+	struct ocfs2_super *osb = OCFS2_SB(alloc_inode->i_sb);
+	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) alloc_bh->b_data;
+	struct ocfs2_chain_list *cl = &fe->id2.i_chain;
+	struct ocfs2_group_desc *group = (struct ocfs2_group_desc *) group_bh->b_data;
+
+	idx = le16_to_cpu(group->bg_chain);
+	rec = &(cl->cl_recs[idx]);
+
+	status = ocfs2_extend_trans(handle,
+				ocfs2_calc_group_alloc_credits(osb->sb,
+						 le16_to_cpu(cl->cl_cpg)));
+	if (status) {
+		mlog_errno(status);
+		goto bail;
+	}
+	status = ocfs2_journal_access_di(handle, INODE_CACHE(alloc_inode),
+					 alloc_bh, OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		goto bail;
+	}
+
+	/*
+	 * Only clear the suballocator rec item in-place.
+	 *
+	 * If idx is not the last, we don't compress (remove the empty item)
+	 * the cl_recs[]. If not, we need to do lots jobs.
+	 *
+	 * Compress cl_recs[] code example:
+	 * if (idx != cl->cl_next_free_rec - 1)
+	 * 	memmove(&cl->cl_recs[idx], &cl->cl_recs[idx + 1],
+	 * 		sizeof(struct ocfs2_chain_rec) *
+	 * 		(cl->cl_next_free_rec - idx - 1));
+	 * for(i = idx; i < cl->cl_next_free_rec-1; i++) {
+	 * 	group->bg_chain = "later group->bg_chain";
+	 * 	group->bg_blkno = xxx;
+	 * 	... ...
+	 * }
+	 */
+
+	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_total);
+	fe->id1.bitmap1.i_total = cpu_to_le32(tmp_used - le32_to_cpu(rec->c_total));
+
+	/* Substraction 1 for the block group itself */
+	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_used);
+	fe->id1.bitmap1.i_used = cpu_to_le32(tmp_used - 1);
+
+	tmp_used = le32_to_cpu(fe->i_clusters);
+	fe->i_clusters = cpu_to_le32(tmp_used - le16_to_cpu(cl->cl_cpg));
+
+	spin_lock(&OCFS2_I(alloc_inode)->ip_lock);
+	OCFS2_I(alloc_inode)->ip_clusters -= le32_to_cpu(fe->i_clusters);
+	fe->i_size = cpu_to_le64(ocfs2_clusters_to_bytes(alloc_inode->i_sb,
+					     le32_to_cpu(fe->i_clusters)));
+	spin_unlock(&OCFS2_I(alloc_inode)->ip_lock);
+	i_size_write(alloc_inode, le64_to_cpu(fe->i_size));
+	alloc_inode->i_blocks = ocfs2_inode_sector_count(alloc_inode);
+
+	ocfs2_journal_dirty(handle, alloc_bh);
+	ocfs2_update_inode_fsync_trans(handle, alloc_inode, 0);
+
+	start_blk = le64_to_cpu(rec->c_blkno);
+	count = le32_to_cpu(rec->c_total) / le16_to_cpu(cl->cl_bpc);
+
+	/*
+	 * If the rec is the last one, let's compress the chain list by
+	 * removing the empty cl_recs[] at the end.
+	 */
+	next_free_rec = le16_to_cpu(cl->cl_next_free_rec);
+	if (idx == (next_free_rec - 1)) {
+		len++; /* the last item should be counted first */
+		for (i = (next_free_rec - 2); i > 0; i--) {
+			if (cl->cl_recs[i].c_free == cl->cl_recs[i].c_total)
+				len++;
+			else
+				break;
+		}
+	}
+	le16_add_cpu(&cl->cl_next_free_rec, -len);
+
+	rec->c_free = 0;
+	rec->c_total = 0;
+	rec->c_blkno = 0;
+	ocfs2_remove_from_cache(INODE_CACHE(alloc_inode), group_bh);
+	memset(group, 0, sizeof(struct ocfs2_group_desc));
+
+	/* prepare job for reclaim clusters */
+	main_bm_inode = ocfs2_get_system_file_inode(osb,
+						    GLOBAL_BITMAP_SYSTEM_INODE,
+						    OCFS2_INVALID_SLOT);
+	if (!main_bm_inode)
+		goto bail; /* ignore the error in reclaim path */
+
+	inode_lock(main_bm_inode);
+
+	status = ocfs2_inode_lock(main_bm_inode, &main_bm_bh, 1);
+	if (status < 0)
+		goto free_bm_inode; /* ignore the error in reclaim path */
+
+	ocfs2_block_to_cluster_group(main_bm_inode, start_blk, &bg_blkno,
+				     &start_bit);
+	fe = (struct ocfs2_dinode *) main_bm_bh->b_data;
+	cl = &fe->id2.i_chain;
+	/* reuse group_bh, caller will release the input group_bh */
+	group_bh = NULL;
+
+	/* reclaim clusters to global_bitmap */
+	status = ocfs2_read_group_descriptor(main_bm_inode, fe, bg_blkno,
+					     &group_bh);
+	if (status < 0) {
+		mlog_errno(status);
+		goto free_bm_bh;
+	}
+	group = (struct ocfs2_group_desc *) group_bh->b_data;
+
+	if ((count + start_bit) > le16_to_cpu(group->bg_bits)) {
+		ocfs2_error(alloc_inode->i_sb,
+			"reclaim length (%d) beyands block group length (%d)",
+			count + start_bit, le16_to_cpu(group->bg_bits));
+		goto free_group_bh;
+	}
+
+	old_bg_contig_free_bits = group->bg_contig_free_bits;
+	status = ocfs2_block_group_clear_bits(handle, main_bm_inode,
+					      group, group_bh,
+					      start_bit, count, 0,
+					      _ocfs2_clear_bit);
+	if (status < 0) {
+		mlog_errno(status);
+		goto free_group_bh;
+	}
+
+	status = ocfs2_journal_access_di(handle, INODE_CACHE(main_bm_inode),
+					 main_bm_bh, OCFS2_JOURNAL_ACCESS_WRITE);
+	if (status < 0) {
+		mlog_errno(status);
+		ocfs2_block_group_set_bits(handle, main_bm_inode, group, group_bh,
+				start_bit, count,
+				le16_to_cpu(old_bg_contig_free_bits), 1);
+		goto free_group_bh;
+	}
+
+	idx = le16_to_cpu(group->bg_chain);
+	rec = &(cl->cl_recs[idx]);
+
+	le32_add_cpu(&rec->c_free, count);
+	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_used);
+	fe->id1.bitmap1.i_used = cpu_to_le32(tmp_used - count);
+	ocfs2_journal_dirty(handle, main_bm_bh);
+
+free_group_bh:
+	brelse(group_bh);
+
+free_bm_bh:
+	ocfs2_inode_unlock(main_bm_inode, 1);
+	brelse(main_bm_bh);
+
+free_bm_inode:
+	inode_unlock(main_bm_inode);
+	iput(main_bm_inode);
+
+bail:
+	return status;
+}
+
 /*
  * expects the suballoc inode to already be locked.
  */
@@ -2526,12 +2793,13 @@ static int _ocfs2_free_suballoc_bits(handle_t *handle,
 				     void (*undo_fn)(unsigned int bit,
 						     unsigned long *bitmap))
 {
-	int status = 0;
+	int idx, status = 0;
 	u32 tmp_used;
 	struct ocfs2_dinode *fe = (struct ocfs2_dinode *) alloc_bh->b_data;
 	struct ocfs2_chain_list *cl = &fe->id2.i_chain;
 	struct buffer_head *group_bh = NULL;
 	struct ocfs2_group_desc *group;
+	struct ocfs2_chain_rec *rec;
 	__le16 old_bg_contig_free_bits = 0;
 
 	/* The alloc_bh comes from ocfs2_free_dinode() or
@@ -2577,12 +2845,26 @@ static int _ocfs2_free_suballoc_bits(handle_t *handle,
 		goto bail;
 	}
 
-	le32_add_cpu(&cl->cl_recs[le16_to_cpu(group->bg_chain)].c_free,
-		     count);
+	idx = le16_to_cpu(group->bg_chain);
+	rec = &(cl->cl_recs[idx]);
+
+	le32_add_cpu(&rec->c_free, count);
 	tmp_used = le32_to_cpu(fe->id1.bitmap1.i_used);
 	fe->id1.bitmap1.i_used = cpu_to_le32(tmp_used - count);
 	ocfs2_journal_dirty(handle, alloc_bh);
 
+	/*
+	 * Reclaim suballocator free space.
+	 * Bypass: global_bitmap, not empty rec, first rec in cl_recs[]
+	 */
+	if (ocfs2_is_cluster_bitmap(alloc_inode) ||
+	    (le32_to_cpu(rec->c_free) != (le32_to_cpu(rec->c_total) - 1)) ||
+	    (le16_to_cpu(cl->cl_next_free_rec) == 1)) {
+		goto bail;
+	}
+
+	_reclaim_to_main_bm(handle, alloc_inode, alloc_bh, group_bh);
+
 bail:
 	brelse(group_bh);
 	return status;
