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Commit 6e53636f authored by Heinz Mauelshagen's avatar Heinz Mauelshagen Committed by Mike Snitzer
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dm raid: add raid4/5/6 journal write-back support via journal_mode option 



Commit 63c32ed4 ("dm raid: add raid4/5/6 journaling support") added
journal support to close the raid4/5/6 "write hole" -- in terms of
writethrough caching.

Introduce a "journal_mode" feature and use the new
r5c_journal_mode_set() API to add support for switching the journal
device's cache mode between write-through (the current default) and
write-back.

NOTE: If the journal device is not layered on resilent storage and it
fails, write-through mode will cause the "write hole" to reoccur.  But
if the journal fails while in write-back mode it will cause data loss
for any dirty cache entries unless resilent storage is used for the
journal.

Signed-off-by: default avatarHeinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 4464e36e

Documentation/device-mapper/dm-raid.txt

+10 −1
Original line number Diff line number Diff line
@@ -170,6 +170,13 @@ The target is named "raid" and it accepts the following parameters: 
		Takeover/reshape is not possible with a raid4/5/6 journal device;

		it has to be deconfigured before requesting these.



	[journal_mode <mode>]

		This option sets the caching mode on journaled raid4/5/6 raid sets

		(see 'journal_dev <dev>' above) to 'writethrough' or 'writeback'.

		If 'writeback' is selected the journal device has to be resilient

		and must not suffer from the 'write hole' problem itself (e.g. use

		raid1 or raid10) to avoid a single point of failure.



<#raid_devs>: The number of devices composing the array.

	Each device consists of two entries.  The first is the device

	containing the metadata (if any); the second is the one containing the
@@ -254,7 +261,8 @@ recovery. Here is a fuller description of the individual fields: 
	<data_offset>   The current data offset to the start of the user data on

			each component device of a raid set (see the respective

			raid parameter to support out-of-place reshaping).

	<journal_char>	'A' - active raid4/5/6 journal device.

	<journal_char>	'A' - active write-through journal device.

			'a' - active write-back journal device.

			'D' - dead journal device.

			'-' - no journal device.
@@ -334,3 +342,4 @@ Version History 
1.10.1  Fix data corruption on reshape request

1.11.0  Fix table line argument order

	(wrong raid10_copies/raid10_format sequence)

1.11.1  Add raid4/5/6 journal write-back support via journal_mode option

drivers/md/dm-raid.c

+91 −13
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2010-2011 Neil Brown

 * Copyright (C) 2010-2016 Red Hat, Inc. All rights reserved.

 * Copyright (C) 2010-2017 Red Hat, Inc. All rights reserved.

 *

 * This file is released under the GPL.

 */
@@ -79,7 +79,10 @@ struct raid_dev { 
#define __CTR_FLAG_RAID10_USE_NEAR_SETS 14 /* 2 */ /* Only with raid10! */



/* New for v1.10.0 */

#define __CTR_FLAG_JOURNAL_DEV		15 /* 2 */ /* Only with raid4/5/6! */

#define __CTR_FLAG_JOURNAL_DEV		15 /* 2 */ /* Only with raid4/5/6 (journal device)! */



/* New for v1.11.1 */

#define __CTR_FLAG_JOURNAL_MODE		16 /* 2 */ /* Only with raid4/5/6 (journal mode)! */



/*

 * Flags for rs->ctr_flags field.
@@ -100,6 +103,7 @@ struct raid_dev { 
#define CTR_FLAG_DATA_OFFSET		(1 << __CTR_FLAG_DATA_OFFSET)

#define CTR_FLAG_RAID10_USE_NEAR_SETS	(1 << __CTR_FLAG_RAID10_USE_NEAR_SETS)

#define CTR_FLAG_JOURNAL_DEV		(1 << __CTR_FLAG_JOURNAL_DEV)

#define CTR_FLAG_JOURNAL_MODE		(1 << __CTR_FLAG_JOURNAL_MODE)



#define RESUME_STAY_FROZEN_FLAGS (CTR_FLAG_DELTA_DISKS | CTR_FLAG_DATA_OFFSET)
@@ -175,7 +179,8 @@ struct raid_dev { 
				 CTR_FLAG_REGION_SIZE | \

				 CTR_FLAG_DELTA_DISKS | \

				 CTR_FLAG_DATA_OFFSET | \

				 CTR_FLAG_JOURNAL_DEV)

				 CTR_FLAG_JOURNAL_DEV | \

				 CTR_FLAG_JOURNAL_MODE)



#define RAID6_VALID_FLAGS	(CTR_FLAG_SYNC | \

				 CTR_FLAG_REBUILD | \
@@ -186,7 +191,8 @@ struct raid_dev { 
				 CTR_FLAG_REGION_SIZE | \

				 CTR_FLAG_DELTA_DISKS | \

				 CTR_FLAG_DATA_OFFSET | \

				 CTR_FLAG_JOURNAL_DEV)

				 CTR_FLAG_JOURNAL_DEV | \

				 CTR_FLAG_JOURNAL_MODE)

/* ...valid options definitions per raid level */



/*
@@ -239,6 +245,7 @@ struct raid_set { 
	struct journal_dev {

		struct dm_dev *dev;

		struct md_rdev rdev;

		int mode;

	} journal_dev;



	struct raid_dev dev[0];
@@ -326,6 +333,7 @@ static struct arg_name_flag { 
	{ CTR_FLAG_DELTA_DISKS, "delta_disks"},

	{ CTR_FLAG_RAID10_USE_NEAR_SETS, "raid10_use_near_sets"},

	{ CTR_FLAG_JOURNAL_DEV, "journal_dev" },

	{ CTR_FLAG_JOURNAL_MODE, "journal_mode" },

};



/* Return argument name string for given @flag */
@@ -344,6 +352,39 @@ static const char *dm_raid_arg_name_by_flag(const uint32_t flag) 
	return NULL;

}



/* Define correlation of raid456 journal cache modes and dm-raid target line parameters */

static struct {

	const int mode;

	const char *param;

} _raid456_journal_mode[] = {

	{ R5C_JOURNAL_MODE_WRITE_THROUGH , "writethrough" },

	{ R5C_JOURNAL_MODE_WRITE_BACK    , "writeback" }

};



/* Return MD raid4/5/6 journal mode for dm @journal_mode one */

static int dm_raid_journal_mode_to_md(const char *mode)

{

	int m = ARRAY_SIZE(_raid456_journal_mode);



	while (m--)

		if (!strcasecmp(mode, _raid456_journal_mode[m].param))

			return _raid456_journal_mode[m].mode;



	return -EINVAL;

}



/* Return dm-raid raid4/5/6 journal mode string for @mode */

static const char *md_journal_mode_to_dm_raid(const int mode)

{

	int m = ARRAY_SIZE(_raid456_journal_mode);



	while (m--)

		if (mode == _raid456_journal_mode[m].mode)

			return _raid456_journal_mode[m].param;



	return "unknown";

}



/*

 * Bool helpers to test for various raid levels of a raid set.

 * It's level as reported by the superblock rather than
@@ -1183,7 +1224,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as, 
			continue;

		}



		/* "journal_dev dev" */

		/* "journal_dev <dev>" */

		if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_JOURNAL_DEV))) {

			int r;

			struct md_rdev *jdev;
@@ -1211,10 +1252,32 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as, 
				rs->ti->error = "No space for raid4/5/6 journal";

				return -ENOSPC;

			}

			rs->journal_dev.mode = R5C_JOURNAL_MODE_WRITE_THROUGH;

			set_bit(Journal, &jdev->flags);

			continue;

		}



		/* "journal_mode <mode>" ("journal_dev" mandatory!) */

		if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_JOURNAL_MODE))) {

			int r;



			if (!test_bit(__CTR_FLAG_JOURNAL_DEV, &rs->ctr_flags)) {

				rs->ti->error = "raid4/5/6 'journal_mode' is invalid without 'journal_dev'";

				return -EINVAL;

			}

			if (test_and_set_bit(__CTR_FLAG_JOURNAL_MODE, &rs->ctr_flags)) {

				rs->ti->error = "Only one raid4/5/6 'journal_mode' argument allowed";

				return -EINVAL;

			}

			r = dm_raid_journal_mode_to_md(arg);

			if (r < 0) {

				rs->ti->error = "Invalid 'journal_mode' argument";

				return r;

			}

			rs->journal_dev.mode = r;

			continue;

		}



		/*

		 * Parameters with number values from here on.

		 */
@@ -3076,6 +3139,16 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	rs->callbacks.congested_fn = raid_is_congested;

	dm_table_add_target_callbacks(ti->table, &rs->callbacks);



	/* If raid4/5/6 journal mode explictely requested (only possible with journal dev) -> set it */

	if (test_bit(__CTR_FLAG_JOURNAL_MODE, &rs->ctr_flags)) {

		r = r5c_journal_mode_set(&rs->md, rs->journal_dev.mode);

		if (r) {

			ti->error = "Failed to set raid4/5/6 journal mode";

			mddev_unlock(&rs->md);

			goto bad_journal_mode_set;

		}

	}



	mddev_suspend(&rs->md);



	/* Try to adjust the raid4/5/6 stripe cache size to the stripe size */
@@ -3109,6 +3182,7 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	mddev_unlock(&rs->md);

	return 0;



bad_journal_mode_set:

bad_stripe_cache:

bad_check_reshape:

	md_stop(&rs->md);
@@ -3180,18 +3254,18 @@ static const char *decipher_sync_action(struct mddev *mddev) 
 * Status characters:

 *

 *  'D' = Dead/Failed raid set component or raid4/5/6 journal device

 *  'a' = Alive but not in-sync

 *  'A' = Alive and in-sync raid set component or alive raid4/5/6 journal device

 *  'a' = Alive but not in-sync raid set component _or_ alive raid4/5/6 'write_back' journal device

 *  'A' = Alive and in-sync raid set component _or_ alive raid4/5/6 'write_through' journal device

 *  '-' = Non-existing device (i.e. uspace passed '- -' into the ctr)

 */

static const char *__raid_dev_status(struct md_rdev *rdev, bool array_in_sync)

static const char *__raid_dev_status(struct raid_set *rs, struct md_rdev *rdev, bool array_in_sync)

{

	if (!rdev->bdev)

		return "-";

	else if (test_bit(Faulty, &rdev->flags))

		return "D";

	else if (test_bit(Journal, &rdev->flags))

		return "A";

		return (rs->journal_dev.mode == R5C_JOURNAL_MODE_WRITE_THROUGH) ? "A" : "a";

	else if (!array_in_sync || !test_bit(In_sync, &rdev->flags))

		return "a";

	else
@@ -3315,7 +3389,7 @@ static void raid_status(struct dm_target *ti, status_type_t type, 


		/* HM FIXME: do we want another state char for raid0? It shows 'D'/'A'/'-' now */

		for (i = 0; i < rs->raid_disks; i++)

			DMEMIT(__raid_dev_status(&rs->dev[i].rdev, array_in_sync));

			DMEMIT(__raid_dev_status(rs, &rs->dev[i].rdev, array_in_sync));



		/*

		 * In-sync/Reshape ratio:
@@ -3366,7 +3440,7 @@ static void raid_status(struct dm_target *ti, status_type_t type, 
		 * v1.10.0+:

		 */

		DMEMIT(" %s", test_bit(__CTR_FLAG_JOURNAL_DEV, &rs->ctr_flags) ?

			      __raid_dev_status(&rs->journal_dev.rdev, 0) : "-");

			      __raid_dev_status(rs, &rs->journal_dev.rdev, 0) : "-");

		break;



	case STATUSTYPE_TABLE:
@@ -3381,7 +3455,8 @@ static void raid_status(struct dm_target *ti, status_type_t type, 
				  write_mostly_params +

				  hweight32(rs->ctr_flags & CTR_FLAG_OPTIONS_NO_ARGS) +

				  hweight32(rs->ctr_flags & CTR_FLAG_OPTIONS_ONE_ARG) * 2 +

				  (test_bit(__CTR_FLAG_JOURNAL_DEV, &rs->ctr_flags) ? 2 : 0);

				  (test_bit(__CTR_FLAG_JOURNAL_DEV, &rs->ctr_flags) ? 2 : 0) +

				  (test_bit(__CTR_FLAG_JOURNAL_MODE, &rs->ctr_flags) ? 2 : 0);



		/* Emit table line */

		/* This has to be in the documented order for userspace! */
@@ -3433,6 +3508,9 @@ static void raid_status(struct dm_target *ti, status_type_t type, 
		if (test_bit(__CTR_FLAG_JOURNAL_DEV, &rs->ctr_flags))

			DMEMIT(" %s %s", dm_raid_arg_name_by_flag(CTR_FLAG_JOURNAL_DEV),

					__get_dev_name(rs->journal_dev.dev));

		if (test_bit(__CTR_FLAG_JOURNAL_MODE, &rs->ctr_flags))

			DMEMIT(" %s %s", dm_raid_arg_name_by_flag(CTR_FLAG_JOURNAL_MODE),

					 md_journal_mode_to_dm_raid(rs->journal_dev.mode));

		DMEMIT(" %d", rs->raid_disks);

		for (i = 0; i < rs->raid_disks; i++)

			DMEMIT(" %s %s", __get_dev_name(rs->dev[i].meta_dev),
@@ -3793,7 +3871,7 @@ static void raid_resume(struct dm_target *ti) 


static struct target_type raid_target = {

	.name = "raid",

	.version = {1, 11, 0},

	.version = {1, 11, 1},

	.module = THIS_MODULE,

	.ctr = raid_ctr,

	.dtr = raid_dtr,