DM RAID: Add message/status support for changing sync action

dm-raid

-------

=======

The device-mapper RAID (dm-raid) target provides a bridge from DM to MD.

It allows the MD RAID drivers to be accessed using a device-mapper

interface.

Mapping Table Interface

-----------------------

The target is named "raid" and it accepts the following parameters:

  <raid_type> <#raid_params> <raid_params> \

    followed by optional parameters (in any order):

	[sync|nosync]   Force or prevent RAID initialization.

	[rebuild <idx>]	Rebuild drive number idx (first drive is 0).

	[rebuild <idx>]	Rebuild drive number 'idx' (first drive is 0).

	[daemon_sleep <ms>]

		Interval between runs of the bitmap daemon that

	[min_recovery_rate <kB/sec/disk>]  Throttle RAID initialization

	[max_recovery_rate <kB/sec/disk>]  Throttle RAID initialization

	[write_mostly <idx>]		   Drive index is write-mostly

	[max_write_behind <sectors>]       See '-write-behind=' (man mdadm)

	[stripe_cache <sectors>]           Stripe cache size (higher RAIDs only)

	[write_mostly <idx>]		   Mark drive index 'idx' write-mostly.

	[max_write_behind <sectors>]       See '--write-behind=' (man mdadm)

	[stripe_cache <sectors>]           Stripe cache size (RAID 4/5/6 only)

	[region_size <sectors>]

		The region_size multiplied by the number of regions is the

		logical size of the array.  The bitmap records the device

	given for both the metadata and data drives for a given position.

Example tables

Example Tables

--------------

# RAID4 - 4 data drives, 1 parity (no metadata devices)

# No metadata devices specified to hold superblock/bitmap info

        raid4 4 2048 sync min_recovery_rate 20 \

        5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82

Status Output

-------------

'dmsetup table' displays the table used to construct the mapping.

The optional parameters are always printed in the order listed

above with "sync" or "nosync" always output ahead of the other

arguments, regardless of the order used when originally loading the table.

Arguments that can be repeated are ordered by value.

'dmsetup status' yields information on the state and health of the

array.

The output is as follows:

'dmsetup status' yields information on the state and health of the array.

The output is as follows (normally a single line, but expanded here for

clarity):

1: <s> <l> raid \

2:      <raid_type> <#devices> <1 health char for each dev> <resync_ratio>

2:      <raid_type> <#devices> <health_chars> \

3:      <sync_ratio> <sync_action> <mismatch_cnt>

Line 1 is the standard output produced by device-mapper.

Line 2 is produced by the raid target, and best explained by example:

        0 1960893648 raid raid4 5 AAAAA 2/490221568

Line 2 & 3 are produced by the raid target and are best explained by example:

        0 1960893648 raid raid4 5 AAAAA 2/490221568 init 0

Here we can see the RAID type is raid4, there are 5 devices - all of

which are 'A'live, and the array is 2/490221568 complete with recovery.

Faulty or missing devices are marked 'D'.  Devices that are out-of-sync

are marked 'a'.

which are 'A'live, and the array is 2/490221568 complete with its initial

recovery.  Here is a fuller description of the individual fields:

	<raid_type>     Same as the <raid_type> used to create the array.

	<health_chars>  One char for each device, indicating: 'A' = alive and

			in-sync, 'a' = alive but not in-sync, 'D' = dead/failed.

	<sync_ratio>    The ratio indicating how much of the array has undergone

			the process described by 'sync_action'.  If the

			'sync_action' is "check" or "repair", then the process

			of "resync" or "recover" can be considered complete.

	<sync_action>   One of the following possible states:

			idle    - No synchronization action is being performed.

			frozen  - The current action has been halted.

			resync  - Array is undergoing its initial synchronization

				  or is resynchronizing after an unclean shutdown

				  (possibly aided by a bitmap).

			recover - A device in the array is being rebuilt or

				  replaced.

			check   - A user-initiated full check of the array is

				  being performed.  All blocks are read and

				  checked for consistency.  The number of

				  discrepancies found are recorded in

				  <mismatch_cnt>.  No changes are made to the

				  array by this action.

			repair  - The same as "check", but discrepancies are

				  corrected.

			reshape - The array is undergoing a reshape.

	<mismatch_cnt>  The number of discrepancies found between mirror copies

			in RAID1/10 or wrong parity values found in RAID4/5/6.

			This value is valid only after a "check" of the array

			is performed.  A healthy array has a 'mismatch_cnt' of 0.

Message Interface

-----------------

The dm-raid target will accept certain actions through the 'message' interface.

('man dmsetup' for more information on the message interface.)  These actions

include:

	"idle"   - Halt the current sync action.

	"frozen" - Freeze the current sync action.

	"resync" - Initiate/continue a resync.

	"recover"- Initiate/continue a recover process.

	"check"  - Initiate a check (i.e. a "scrub") of the array.

	"repair" - Initiate a repair of the array.

	"reshape"- Currently unsupported (-EINVAL).

Version History

---------------

1.3.1	Allow device replacement/rebuild for RAID 10

1.3.2   Fix/improve redundancy checking for RAID10

1.4.0	Non-functional change.  Removes arg from mapping function.

1.4.1   Add RAID10 "far" and "offset" algorithm support.

1.4.1   RAID10 fix redundancy validation checks (commit 55ebbb5).

1.4.2   Add RAID10 "far" and "offset" algorithm support.

1.5.0   Add message interface to allow manipulation of the sync_action.

	New status (STATUSTYPE_INFO) fields: sync_action and mismatch_cnt.

	return DM_MAPIO_SUBMITTED;

}

static const char *decipher_sync_action(struct mddev *mddev)

{

	if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))

		return "frozen";

	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||

	    (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {

		if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))

			return "reshape";

		if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {

			if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))

				return "resync";

			else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))

				return "check";

			return "repair";

		}

		if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))

			return "recover";

	}

	return "idle";

}

static void raid_status(struct dm_target *ti, status_type_t type,

			unsigned status_flags, char *result, unsigned maxlen)

{

			sync = rs->md.recovery_cp;

		if (sync >= rs->md.resync_max_sectors) {

			/*

			 * Sync complete.

			 */

			array_in_sync = 1;

			sync = rs->md.resync_max_sectors;

		} else if (test_bit(MD_RECOVERY_REQUESTED, &rs->md.recovery)) {

			/*

			 * If "check" or "repair" is occurring, the array has

			 * undergone and initial sync and the health characters

			 * should not be 'a' anymore.

			 */

			array_in_sync = 1;

		} else {

			/*

			 * The array may be doing an initial sync, or it may

				if (!test_bit(In_sync, &rs->dev[i].rdev.flags))

					array_in_sync = 1;

		}

		/*

		 * Status characters:

		 *  'D' = Dead/Failed device

		       (unsigned long long) sync,

		       (unsigned long long) rs->md.resync_max_sectors);

		/*

		 * Sync action:

		 *   See Documentation/device-mapper/dm-raid.c for

		 *   information on each of these states.

		 */

		DMEMIT(" %s", decipher_sync_action(&rs->md));

		/*

		 * resync_mismatches/mismatch_cnt

		 *   This field shows the number of discrepancies found when

		 *   performing a "check" of the array.

		 */

		DMEMIT(" %llu",

		       (unsigned long long)

		       atomic64_read(&rs->md.resync_mismatches));

		break;

	case STATUSTYPE_TABLE:

		/* The string you would use to construct this array */

	}

}

static int raid_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)

static int raid_message(struct dm_target *ti, unsigned argc, char **argv)

{

	struct raid_set *rs = ti->private;

	struct mddev *mddev = &rs->md;

	if (!strcasecmp(argv[0], "reshape")) {

		DMERR("Reshape not supported.");

		return -EINVAL;

	}

	if (!mddev->pers || !mddev->pers->sync_request)

		return -EINVAL;

	if (!strcasecmp(argv[0], "frozen"))

		set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

	else

		clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);

	if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) {

		if (mddev->sync_thread) {

			set_bit(MD_RECOVERY_INTR, &mddev->recovery);

			md_reap_sync_thread(mddev);

		}

	} else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||

		   test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))

		return -EBUSY;

	else if (!strcasecmp(argv[0], "resync"))

		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

	else if (!strcasecmp(argv[0], "recover")) {

		set_bit(MD_RECOVERY_RECOVER, &mddev->recovery);

		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

	} else {

		if (!strcasecmp(argv[0], "check"))

			set_bit(MD_RECOVERY_CHECK, &mddev->recovery);

		else if (!!strcasecmp(argv[0], "repair"))

			return -EINVAL;

		set_bit(MD_RECOVERY_REQUESTED, &mddev->recovery);

		set_bit(MD_RECOVERY_SYNC, &mddev->recovery);

	}

	if (mddev->ro == 2) {

		/* A write to sync_action is enough to justify

		 * canceling read-auto mode

		 */

		mddev->ro = 0;

		if (!mddev->suspended)

			md_wakeup_thread(mddev->sync_thread);

	}

	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

	if (!mddev->suspended)

		md_wakeup_thread(mddev->thread);

	return 0;

}

static int raid_iterate_devices(struct dm_target *ti,

				iterate_devices_callout_fn fn, void *data)

{

	struct raid_set *rs = ti->private;

	unsigned i;

static struct target_type raid_target = {

	.name = "raid",

	.version = {1, 4, 2},

	.version = {1, 5, 0},

	.module = THIS_MODULE,

	.ctr = raid_ctr,

	.dtr = raid_dtr,

	.map = raid_map,

	.status = raid_status,

	.message = raid_message,

	.iterate_devices = raid_iterate_devices,

	.io_hints = raid_io_hints,

	.presuspend = raid_presuspend,