f2fs: fix to determine start_cp_addr by sbi->cur_cp_pack

BugLink: https://bugs.launchpad.net/bugs/1818797

commit 8508e44a upstream.

We don't guarantee cp_addr is fixed by cp_version.
This is to sync with f2fs-tools.
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
[bwh: Backported to 4.4: adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

fs/f2fs/checkpoint.c

@@ -710,6 +710,11 @@ int get_valid_checkpoint(struct f2fs_sb_info *sbi)
 	if (sanity_check_ckpt(sbi))
 		goto fail_no_cp;
 
+	if (cur_page == cp1)
+		sbi->cur_cp_pack = 1;
+	else
+		sbi->cur_cp_pack = 2;
+
 	if (cp_blks <= 1)
 		goto done;
 
@@ -1008,7 +1013,7 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 				le32_to_cpu(ckpt->checksum_offset)))
 				= cpu_to_le32(crc32);
 
-	start_blk = __start_cp_addr(sbi);
+	start_blk = __start_cp_next_addr(sbi);
 
 	/* need to wait for end_io results */
 	wait_on_all_pages_writeback(sbi);
@@ -1063,6 +1068,7 @@ static void do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 	clear_prefree_segments(sbi, cpc);
 	clear_sbi_flag(sbi, SBI_IS_DIRTY);
+	__set_cp_next_pack(sbi);
 }
 
 /*

fs/f2fs/f2fs.h

@@ -731,6 +731,7 @@ struct f2fs_sb_info {
 
 	/* for checkpoint */
 	struct f2fs_checkpoint *ckpt;		/* raw checkpoint pointer */
+	int cur_cp_pack;			/* remain current cp pack */
 	struct inode *meta_inode;		/* cache meta blocks */
 	struct mutex cp_mutex;			/* checkpoint procedure lock */
 	struct rw_semaphore cp_rwsem;		/* blocking FS operations */
@@ -1140,22 +1141,27 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag)
 
 static inline block_t __start_cp_addr(struct f2fs_sb_info *sbi)
 {
-	block_t start_addr;
-	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
-	unsigned long long ckpt_version = cur_cp_version(ckpt);
-
-	start_addr = le32_to_cpu(F2FS_RAW_SUPER(sbi)->cp_blkaddr);
+	block_t start_addr = le32_to_cpu(F2FS_RAW_SUPER(sbi)->cp_blkaddr);
 
-	/*
-	 * odd numbered checkpoint should at cp segment 0
-	 * and even segment must be at cp segment 1
-	 */
-	if (!(ckpt_version & 1))
+	if (sbi->cur_cp_pack == 2)
 		start_addr += sbi->blocks_per_seg;
+	return start_addr;
+}
 
+static inline block_t __start_cp_next_addr(struct f2fs_sb_info *sbi)
+{
+	block_t start_addr = le32_to_cpu(F2FS_RAW_SUPER(sbi)->cp_blkaddr);
+
+	if (sbi->cur_cp_pack == 1)
+		start_addr += sbi->blocks_per_seg;
 	return start_addr;
 }
 
+static inline void __set_cp_next_pack(struct f2fs_sb_info *sbi)
+{
+	sbi->cur_cp_pack = (sbi->cur_cp_pack == 1) ? 2 : 1;
+}
+
 static inline block_t __start_sum_addr(struct f2fs_sb_info *sbi)
 {
 	return le32_to_cpu(F2FS_CKPT(sbi)->cp_pack_start_sum);