f2fs: fix to caclulate required free section correctly

When calculating required free section during file defragmenting, we
should skip holes in file, otherwise we will probably fail to defrag
sparse file with large size.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -2125,10 +2125,12 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
 			continue;
 		}
 
-		if (blk_end && blk_end != map.m_pblk) {
+		if (blk_end && blk_end != map.m_pblk)
 			fragmented = true;
-			break;
-		}
+
+		/* record total count of block that we're going to move */
+		total += map.m_len;
+
 		blk_end = map.m_pblk + map.m_len;
 
 		map.m_lblk += map.m_len;
@@ -2137,10 +2139,7 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
 	if (!fragmented)
 		goto out;
 
-	map.m_lblk = pg_start;
-	map.m_len = pg_end - pg_start;
-
-	sec_num = (map.m_len + BLKS_PER_SEC(sbi) - 1) / BLKS_PER_SEC(sbi);
+	sec_num = (total + BLKS_PER_SEC(sbi) - 1) / BLKS_PER_SEC(sbi);
 
 	/*
 	 * make sure there are enough free section for LFS allocation, this can
@@ -2152,6 +2151,10 @@ static int f2fs_defragment_range(struct f2fs_sb_info *sbi,
 		goto out;
 	}
 
+	map.m_lblk = pg_start;
+	map.m_len = pg_end - pg_start;
+	total = 0;
+
 	while (map.m_lblk < pg_end) {
 		pgoff_t idx;
 		int cnt = 0;