f2fs: support FALLOC_FL_ZERO_RANGE

index 86bcc9c..b8099aa 100644
@@ -890,6 +890,108 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
 	return ret;
 }
 
+static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
+								int mode)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index, pg_start, pg_end;
+	loff_t new_size = i_size_read(inode);
+	loff_t off_start, off_end;
+	int ret = 0;
+
+	if (!S_ISREG(inode->i_mode))
+		return -EINVAL;
+
+	ret = inode_newsize_ok(inode, (len + offset));
+	if (ret)
+		return ret;
+
+	f2fs_balance_fs(sbi);
+
+	if (f2fs_has_inline_data(inode)) {
+		ret = f2fs_convert_inline_inode(inode);
+		if (ret)
+			return ret;
+	}
+
+	ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1);
+	if (ret)
+		return ret;
+
+	truncate_pagecache_range(inode, offset, offset + len - 1);
+
+	pg_start = ((unsigned long long) offset) >> PAGE_CACHE_SHIFT;
+	pg_end = ((unsigned long long) offset + len) >> PAGE_CACHE_SHIFT;
+
+	off_start = offset & (PAGE_CACHE_SIZE - 1);
+	off_end = (offset + len) & (PAGE_CACHE_SIZE - 1);
+
+	if (pg_start == pg_end) {
+		fill_zero(inode, pg_start, off_start, off_end - off_start);
+		if (offset + len > new_size)
+			new_size = offset + len;
+		new_size = max_t(loff_t, new_size, offset + len);
+	} else {
+		if (off_start) {
+			fill_zero(inode, pg_start++, off_start,
+					PAGE_CACHE_SIZE - off_start);
+			new_size = max_t(loff_t, new_size,
+						pg_start << PAGE_CACHE_SHIFT);
+		}
+
+		for (index = pg_start; index < pg_end; index++) {
+			struct dnode_of_data dn;
+			struct page *ipage;
+
+			f2fs_lock_op(sbi);
+
+			ipage = get_node_page(sbi, inode->i_ino);
+			if (IS_ERR(ipage)) {
+				ret = PTR_ERR(ipage);
+				f2fs_unlock_op(sbi);
+				goto out;
+			}
+
+			set_new_dnode(&dn, inode, ipage, NULL, 0);
+			ret = f2fs_reserve_block(&dn, index);
+			if (ret) {
+				f2fs_unlock_op(sbi);
+				goto out;
+			}
+
+			if (dn.data_blkaddr != NEW_ADDR) {
+				invalidate_blocks(sbi, dn.data_blkaddr);
+
+				dn.data_blkaddr = NEW_ADDR;
+				set_data_blkaddr(&dn);
+
+				dn.data_blkaddr = NULL_ADDR;
+				f2fs_update_extent_cache(&dn);
+			}
+			f2fs_put_dnode(&dn);
+			f2fs_unlock_op(sbi);
+
+			new_size = max_t(loff_t, new_size,
+					(index + 1) << PAGE_CACHE_SHIFT);
+		}
+
+		if (off_end) {
+			fill_zero(inode, pg_end, 0, off_end);
+			new_size = max_t(loff_t, new_size, offset + len);
+		}
+	}
+
+out:
+	if (!(mode & FALLOC_FL_KEEP_SIZE) && i_size_read(inode) < new_size) {
+		i_size_write(inode, new_size);
+		mark_inode_dirty(inode);
+		update_inode_page(inode);
+	}
+
+	return ret;
+}
+
 static int expand_inode_data(struct inode *inode, loff_t offset,
 					loff_t len, int mode)
 {

@@ -958,7 +1060,7 @@ static long f2fs_fallocate(struct file *file, int mode,
 	long ret;
 
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
-			FALLOC_FL_COLLAPSE_RANGE))
+			FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
 		return -EOPNOTSUPP;
 
 	mutex_lock(&inode->i_mutex);

@@ -967,6 +1069,8 @@ static long f2fs_fallocate(struct file *file, int mode,
 		ret = punch_hole(inode, offset, len);
 	else if (mode & FALLOC_FL_COLLAPSE_RANGE)
 		ret = f2fs_collapse_range(inode, offset, len);
+	else if (mode & FALLOC_FL_ZERO_RANGE)
+		ret = f2fs_zero_range(inode, offset, len, mode);
 	else
 		ret = expand_inode_data(inode, offset, len, mode);