f2fs: fix to release discard entries during checkpoint

In f2fs_fill_super, if there is any IO error occurs during recovery,
cached discard entries will be leaked, in order to avoid this, make
write_checkpoint() handle memory release by itself, besides, move
clear_prefree_segments to write_checkpoint for readability.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -1184,7 +1184,6 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	if (unlikely(f2fs_cp_error(sbi)))
 		return -EIO;
 
-	clear_prefree_segments(sbi, cpc);
 	clear_sbi_flag(sbi, SBI_IS_DIRTY);
 	clear_sbi_flag(sbi, SBI_NEED_CP);
 
@@ -1261,8 +1260,12 @@ int write_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 
 	/* unlock all the fs_lock[] in do_checkpoint() */
 	err = do_checkpoint(sbi, cpc);
-
-	f2fs_wait_all_discard_bio(sbi);
+	if (err) {
+		release_discard_addrs(sbi);
+	} else {
+		clear_prefree_segments(sbi, cpc);
+		f2fs_wait_all_discard_bio(sbi);
+	}
 
 	unblock_operations(sbi);
 	stat_inc_cp_count(sbi->stat_info);

fs/f2fs/super.c

@@ -738,7 +738,6 @@ static void f2fs_put_super(struct super_block *sb)
 	 * In addition, EIO will skip do checkpoint, we need this as well.
 	 */
 	release_ino_entry(sbi, true);
-	release_discard_addrs(sbi);
 
 	f2fs_leave_shrinker(sbi);
 	mutex_unlock(&sbi->umount_mutex);