mkfs.f2fs: add -r (fake_seed) flag

r flag sets the checkpointing seed to 0 (initially used to
remove randomness for apex generation)

Signed-off-by: Theotime Combes <tcombes@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

4 files changed, 13 insertions, 2 deletions

diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
index 20abdf7..b5bda13 100644
--- a/include/f2fs_fs.h
+++ b/include/f2fs_fs.h
@@ -407,6 +407,7 @@ struct f2fs_configuration {
 	time_t fixed_time;
 
 	/* mkfs parameters */
+	int fake_seed;
 	u_int32_t next_free_nid;
 	u_int32_t quota_inum;
 	u_int32_t quota_dnum;
diff --git a/man/mkfs.f2fs.8 b/man/mkfs.f2fs.8
index 729afdf..e2aee76 100644
--- a/man/mkfs.f2fs.8
+++ b/man/mkfs.f2fs.8
@@ -59,6 +59,9 @@ mkfs.f2fs \- create an F2FS file system
 .B \-q
 ]
 [
+.B \-r
+]
+[
 .B \-R
 .I root_owner
 ]
@@ -216,6 +219,9 @@ Default is disabled.
 Quiet mode.
 With it, mkfs.f2fs does not show any messages, including the basic messages.
 .TP
+.BI \-r
+Sets the checkpointing srand seed to 0.
+.TP
 .BI \-R
 Give root_owner option for initial uid/gid assignment.
 Default is set by getuid()/getgid(), and assigned by "-R $uid:$gid".
diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
index cb27b42..a6c542e 100644
--- a/mkfs/f2fs_format.c
+++ b/mkfs/f2fs_format.c
@@ -670,7 +670,7 @@ static int f2fs_write_check_point_pack(void)
 	}
 
 	/* 1. cp page 1 of checkpoint pack 1 */
-	srand(time(NULL));
+	srand((c.fake_seed) ? 0 : time(NULL));
 	cp->checkpoint_ver = cpu_to_le64(rand() | 0x1);
 	set_cp(cur_node_segno[0], c.cur_seg[CURSEG_HOT_NODE]);
 	set_cp(cur_node_segno[1], c.cur_seg[CURSEG_WARM_NODE]);
diff --git a/mkfs/f2fs_format_main.c b/mkfs/f2fs_format_main.c
index 9fe049c..f2f0a80 100644
--- a/mkfs/f2fs_format_main.c
+++ b/mkfs/f2fs_format_main.c
@@ -58,6 +58,7 @@ static void mkfs_usage()
 	MSG(0, "  -O feature1[,feature2,...] e.g. \"encrypt\"\n");
 	MSG(0, "  -C [encoding[:flag1,...]] Support casefolding with optional flags\n");
 	MSG(0, "  -q quiet mode\n");
+	MSG(0, "  -r set checkpointing seed (srand()) to 0\n");
 	MSG(0, "  -R root_owner [default: 0:0]\n");
 	MSG(0, "  -s # of segments per section [default:1]\n");
 	MSG(0, "  -S sparse mode\n");
@@ -124,7 +125,7 @@ static void add_default_options(void)
 
 static void f2fs_parse_options(int argc, char *argv[])
 {
-	static const char *option_string = "qa:c:C:d:e:E:g:il:mo:O:R:s:S:z:t:T:U:Vfw:";
+	static const char *option_string = "qa:c:C:d:e:E:g:il:mo:O:rR:s:S:z:t:T:U:Vfw:";
 	int32_t option=0;
 	int val;
 	char *token;
@@ -184,6 +185,9 @@ static void f2fs_parse_options(int argc, char *argv[])
 			if (parse_feature(feature_table, optarg))
 				mkfs_usage();
 			break;
+		case 'r':
+			c.fake_seed = 1;
+			break;
 		case 'R':
 			if (parse_root_owner(optarg, &c.root_uid, &c.root_gid))
 				mkfs_usage();