drivers: md: use ktime_get_real_seconds()

get_seconds() API is not y2038 safe on 32 bit systems and the API
is deprecated. Replace it with calls to ktime_get_real_seconds()
API instead. Change mddev structure types to time64_t accordingly.

32 bit signed timestamps will overflow in the year 2038.

Change the user interface mdu_array_info_s structure timestamps:
ctime and utime values used in ioctls GET_ARRAY_INFO and
SET_ARRAY_INFO to unsigned int. This will extend the field to last
until the year 2106.
The long term plan is to get rid of ctime and utime values in
this structure as this information can be read from the on-disk
meta data directly.

Clamp the tim64_t timestamps to positive values with a max of U32_MAX
when returning from GET_ARRAY_INFO ioctl to accommodate above changes
in the data type of timestamps to unsigned int.

v0.90 on disk meta data uses u32 for maintaining time stamps.
So this will also last until year 2106.
Assumption is that the usage of v0.90 will be deprecated by
year 2106.

Timestamp fields in the on disk meta data for v1.0 version already
use 64 bit data types. Remove the truncation of the bits while
writing to or reading from these from the disk.

Signed-off-by: Deepa Dinamani <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Signed-off-by: NeilBrown <[e-mail]>

drivers/md/md.c

···
 	memcpy(&sb->set_uuid2, mddev->uuid+8, 4);
 	memcpy(&sb->set_uuid3, mddev->uuid+12,4);
 
-	sb->ctime = mddev->ctime;
+	sb->ctime = clamp_t(time64_t, mddev->ctime, 0, U32_MAX);
 	sb->level = mddev->level;
 	sb->size = mddev->dev_sectors / 2;
 	sb->raid_disks = mddev->raid_disks;
 	sb->md_minor = mddev->md_minor;
 	sb->not_persistent = 0;
-	sb->utime = mddev->utime;
+	sb->utime = clamp_t(time64_t, mddev->utime, 0, U32_MAX);
 	sb->state = 0;
 	sb->events_hi = (mddev->events>>32);
 	sb->events_lo = (u32)mddev->events;
···
 		mddev->patch_version = 0;
 		mddev->external = 0;
 		mddev->chunk_sectors = le32_to_cpu(sb->chunksize);
-		mddev->ctime = le64_to_cpu(sb->ctime) & ((1ULL << 32)-1);
-		mddev->utime = le64_to_cpu(sb->utime) & ((1ULL << 32)-1);
+		mddev->ctime = le64_to_cpu(sb->ctime);
+		mddev->utime = le64_to_cpu(sb->utime);
 		mddev->level = le32_to_cpu(sb->level);
 		mddev->clevel[0] = 0;
 		mddev->layout = le32_to_cpu(sb->layout);
···
 
 	spin_lock(&mddev->lock);
 
-	mddev->utime = get_seconds();
+	mddev->utime = ktime_get_real_seconds();
 
 	if (test_and_clear_bit(MD_CHANGE_DEVS, &mddev->flags))
 		force_change = 1;
···
 	info.major_version = mddev->major_version;
 	info.minor_version = mddev->minor_version;
 	info.patch_version = MD_PATCHLEVEL_VERSION;
-	info.ctime         = mddev->ctime;
+	info.ctime         = clamp_t(time64_t, mddev->ctime, 0, U32_MAX);
 	info.level         = mddev->level;
 	info.size          = mddev->dev_sectors / 2;
 	if (info.size != mddev->dev_sectors / 2) /* overflow */
···
 	info.md_minor      = mddev->md_minor;
 	info.not_persistent= !mddev->persistent;
 
-	info.utime         = mddev->utime;
+	info.utime         = clamp_t(time64_t, mddev->utime, 0, U32_MAX);
 	info.state         = 0;
 	if (mddev->in_sync)
 		info.state = (1<<MD_SB_CLEAN);
···
 		/* ensure mddev_put doesn't delete this now that there
 		 * is some minimal configuration.
 		 */
-		mddev->ctime         = get_seconds();
+		mddev->ctime         = ktime_get_real_seconds();
 		return 0;
 	}
 	mddev->major_version = MD_MAJOR_VERSION;
 	mddev->minor_version = MD_MINOR_VERSION;
 	mddev->patch_version = MD_PATCHLEVEL_VERSION;
-	mddev->ctime         = get_seconds();
+	mddev->ctime         = ktime_get_real_seconds();
 
 	mddev->level         = info->level;
 	mddev->clevel[0]     = 0;

drivers/md/md.h

···
 							 * managed externally */
 	char				metadata_type[17]; /* externally set*/
 	int				chunk_sectors;
-	time_t				ctime, utime;
+	time64_t			ctime, utime;
 	int				level, layout;
 	char				clevel[16];
 	int				raid_disks;

include/uapi/linux/raid/md_u.h

···
 	int major_version;
 	int minor_version;
 	int patch_version;
-	int ctime;
+	unsigned int ctime;
 	int level;
 	int size;
 	int nr_disks;
···
 	/*
 	 * Generic state information
 	 */
-	int utime;		/*  0 Superblock update time		      */
+	unsigned int utime;	/*  0 Superblock update time		      */
 	int state;		/*  1 State bits (clean, ...)		      */
 	int active_disks;	/*  2 Number of currently active disks	      */
 	int working_disks;	/*  3 Number of working disks		      */