tune2fs: teach tune2fs to use a random value for "-c random"

Addresses-Debian-Bug: #926293
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

2 files changed, 21 insertions, 18 deletions

diff --git a/misc/tune2fs.8.in b/misc/tune2fs.8.in
index 1a181a73b..b963f30ed 100644
--- a/misc/tune2fs.8.in
+++ b/misc/tune2fs.8.in
@@ -117,6 +117,9 @@ Adjust the number of mounts after which the filesystem will be checked by
 .BR e2fsck (8).
 If
 .I max-mount-counts
+is the string "random", tune2fs will use a random value between 20 and 40.
+If
+.I max-mount-counts
 is 0 or \-1, the number of times the filesystem is mounted will be disregarded
 by
 .BR e2fsck (8)
@@ -127,21 +130,13 @@ checked will avoid all filesystems being checked at one time
 when using journaled filesystems.
 .sp
 Mount-count-dependent checking is disabled by default to avoid
-unanticipated long reboots while e2fsck does its work.  However,
-you may wish to consider the consequences of disabling
-mount-count-dependent checking entirely.  Bad disk drives, cables,
-memory, and kernel bugs could all corrupt a filesystem without
-marking the filesystem dirty or in error.  If you are using
-journaling on your filesystem, your filesystem will
-.B never
-be marked dirty, so it will not normally be checked.  A
-filesystem error detected by the kernel will still force
-an fsck on the next reboot, but it may already be too late
-to prevent data loss at that point.
-.sp
-See also the
-.B \-i
-option for time-dependent checking.
+unanticipated long reboots while e2fsck does its work.  If you
+are concerned about file system corruptions caused by potential hardware
+problems of kernel bugs, a better solution than mount-count-dependent
+checking is to use the
+.BR e2scrub (8)
+program.  This does require placing the file system on an LVM volume,
+however.
 .TP
 .BI \-C " mount-count"
 Set the number of times the filesystem has been mounted.
diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 11715ba49..f739f16cd 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -1826,8 +1826,15 @@ static void parse_tune2fs_options(int argc, char **argv)
 	while ((c = getopt(argc, argv, optstring)) != EOF)
 		switch (c) {
 		case 'c':
+			open_flag = EXT2_FLAG_RW;
+			c_flag = 1;
+			if (strcmp(optarg, "random") == 0) {
+				max_mount_count = 65536;
+				break;
+			}
 			max_mount_count = strtol(optarg, &tmp, 0);
-			if (*tmp || max_mount_count > 16000) {
+			if (*tmp || max_mount_count > 16000 ||
+			    max_mount_count < -16000) {
 				com_err(program_name, 0,
 					_("bad mounts count - %s"),
 					optarg);
@@ -1835,8 +1842,6 @@ static void parse_tune2fs_options(int argc, char **argv)
 			}
 			if (max_mount_count == 0)
 				max_mount_count = -1;
-			c_flag = 1;
-			open_flag = EXT2_FLAG_RW;
 			break;
 		case 'C':
 			mount_count = strtoul(optarg, &tmp, 0);
@@ -3104,6 +3109,9 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n"
 	fs->flags |= EXT2_FLAG_SUPER_ONLY;
 
 	if (c_flag) {
+		if (max_mount_count == 65536)
+			max_mount_count = EXT2_DFL_MAX_MNT_COUNT +
+				(random() % EXT2_DFL_MAX_MNT_COUNT);
 		sb->s_max_mnt_count = max_mount_count;
 		ext2fs_mark_super_dirty(fs);
 		printf(_("Setting maximal mount count to %d\n"),