[PATCH] erofs-utils: mkfs: add `--mkfs-time` option

[Gao Xiang]

Some users need a fixed build time in the superblock for reproducible
builds rather than a fixed timestamp everywhere.

Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
---
 include/erofs/config.h |  1 +
 man/mkfs.erofs.1       | 14 ++++++++++++--
 mkfs/main.c            | 18 ++++++++++++++++--
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/include/erofs/config.h b/include/erofs/config.h
index 56650e3..ae366c1 100644
--- a/include/erofs/config.h
+++ b/include/erofs/config.h
@@ -27,6 +27,7 @@ enum {
 };
 
 enum {
+	TIMESTAMP_UNSPECIFIED,
 	TIMESTAMP_NONE,
 	TIMESTAMP_FIXED,
 	TIMESTAMP_CLAMPING,
diff --git a/man/mkfs.erofs.1 b/man/mkfs.erofs.1
index 3bff41d..d599fac 100644
--- a/man/mkfs.erofs.1
+++ b/man/mkfs.erofs.1
@@ -100,8 +100,10 @@ Set the volume label for the filesystem to
 The maximum length of the volume label is 16 bytes.
 .TP
 .BI "\-T " #
-Set all files to the given UNIX timestamp. Reproducible builds require setting
-all to a specific one. By default, the source file's modification time is used.
+Specify a UNIX timestamp for image creation time for reproducible builds.
+If \fI--mkfs-time\fR is not specified, it will behave as \fI--all-time\fR:
+setting all files to the specified UNIX timestamp instead of using the
+modification times of the source files.
 .TP
 .BI "\-U " UUID
 Set the universally unique identifier (UUID) of the filesystem to
@@ -112,6 +114,10 @@ like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
 .B \-\-all-root
 Make all files owned by root.
 .TP
+.B \-\-all-time
+(used together with \fB-T\fR) set all files to the fixed timestamp. This is the
+default.
+.TP
 .BI "\-\-blobdev " file
 Specify an extra blob device to store chunk-based data.
 .TP
@@ -177,6 +183,10 @@ can reduce total metadata size. Implied by
 .BI "\-\-max-extent-bytes " #
 Specify maximum decompressed extent size in bytes.
 .TP
+.B \-\-mkfs-time
+(used together with \fB-T\fR) the given timestamp is only applied to the build
+time.
+.TP
 .B "\-\-preserve-mtime"
 Use extended inodes instead of compact inodes if the file modification time
 would overflow compact inodes. This is the default. Overrides
diff --git a/mkfs/main.c b/mkfs/main.c
index aba5ce4..b7129eb 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -82,6 +82,8 @@ static struct option long_options[] = {
 	{"clean", optional_argument, NULL, 522},
 	{"incremental", optional_argument, NULL, 523},
 	{"root-xattr-isize", required_argument, NULL, 524},
+	{"mkfs-time", no_argument, NULL, 525},
+	{"all-time", no_argument, NULL, 526},
 	{0, 0, 0, 0},
 };
 
@@ -150,7 +152,9 @@ static void usage(int argc, char **argv)
 		" -C#                   specify the size of compress physical cluster in bytes\n"
 		" -EX[,...]             X=extended options\n"
 		" -L volume-label       set the volume label (maximum 16)\n"
-		" -T#                   set a fixed UNIX timestamp # to all files\n"
+		" -T#                   specify a fixed UNIX timestamp # as build time\n"
+		"    --all-time         the timestamp is also applied to all files (default)\n"
+		"    --mkfs-time        the timestamp is applied as build time only\n"
 		" -UX                   use a given filesystem UUID\n"
 		" --all-root            make all files owned by root\n"
 		" --blobdev=X           specify an extra device X to store chunked data\n"
@@ -548,6 +552,7 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 	int opt, i, err;
 	bool quiet = false;
 	int tarerofs_decoder = 0;
+	bool has_timestamp = false;
 
 	while ((opt = getopt_long(argc, argv, "C:E:L:T:U:b:d:x:z:Vh",
 				  long_options, NULL)) != -1) {
@@ -607,7 +612,7 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 				erofs_err("invalid UNIX timestamp %s", optarg);
 				return -EINVAL;
 			}
-			cfg.c_timeinherit = TIMESTAMP_FIXED;
+			has_timestamp = true;
 			break;
 		case 'U':
 			if (erofs_uuid_parse(optarg, fixeduuid)) {
@@ -829,6 +834,12 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 				return -EINVAL;
 			}
 			break;
+		case 525:
+			cfg.c_timeinherit = TIMESTAMP_NONE;
+			break;
+		case 526:
+			cfg.c_timeinherit = TIMESTAMP_FIXED;
+			break;
 		case 'V':
 			version();
 			exit(0);
@@ -984,6 +995,9 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 		}
 		cfg.c_mkfs_pclustersize_packed = pclustersize_packed;
 	}
+
+	if (has_timestamp && cfg.c_timeinherit == TIMESTAMP_UNSPECIFIED)
+		cfg.c_timeinherit = TIMESTAMP_FIXED;
 	return 0;
 }
 
-- 
2.43.5