Commit 67cc2b81 authored by NeilBrown's avatar NeilBrown
Browse files

md/raid5: finish support for DDF/raid6 



DDF requires RAID6 calculations over different devices in a different
order.
For md/raid6, we calculate over just the data devices, starting
immediately after the 'Q' block.
For ddf/raid6 we calculate over all devices, using zeros in place of
the P and Q blocks.

This requires unfortunately complex loops...

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 99c0fb5f

drivers/md/raid5.c

+40 −18
Original line number Diff line number Diff line
@@ -136,6 +136,10 @@ static inline void raid5_set_bi_hw_segments(struct bio *bio, unsigned int cnt) 
/* Find first data disk in a raid6 stripe */

static inline int raid6_d0(struct stripe_head *sh)

{

	if (sh->ddf_layout)

		/* ddf always start from first device */

		return 0;

	/* md starts just after Q block */

	if (sh->qd_idx == sh->disks - 1)

		return 0;

	else
@@ -152,13 +156,15 @@ static inline int raid6_next_disk(int disk, int raid_disks) 
 * 0 .. raid_disks-3, the parity disk is raid_disks-2 and the Q disk

 * is raid_disks-1.  This help does that mapping.

 */

static int raid6_idx_to_slot(int idx, struct stripe_head *sh, int *count)

static int raid6_idx_to_slot(int idx, struct stripe_head *sh,

			     int *count, int syndrome_disks)

{

	int slot;



	if (idx == sh->pd_idx)

		return sh->disks - 2;

		return syndrome_disks;

	if (idx == sh->qd_idx)

		return sh->disks - 1;

		return syndrome_disks + 1;

	slot = (*count)++;

	return slot;

}
@@ -1267,6 +1273,7 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector, 
	unsigned long chunk_number;

	unsigned int chunk_offset;

	int pd_idx, qd_idx;

	int ddf_layout = 0;

	sector_t new_sector;

	int sectors_per_chunk = conf->chunk_size >> 9;

	int raid_disks = previous ? conf->previous_raid_disks
@@ -1386,6 +1393,7 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector, 
				qd_idx = 0;

			} else if (*dd_idx >= pd_idx)

				(*dd_idx) += 2; /* D D P Q D */

			ddf_layout = 1;

			break;



		case ALGORITHM_ROTATING_N_RESTART:
@@ -1400,6 +1408,7 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector, 
				qd_idx = 0;

			} else if (*dd_idx >= pd_idx)

				(*dd_idx) += 2; /* D D P Q D */

			ddf_layout = 1;

			break;



		case ALGORITHM_ROTATING_N_CONTINUE:
@@ -1407,6 +1416,7 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector, 
			pd_idx = raid_disks - 1 - (stripe % raid_disks);

			qd_idx = (pd_idx + raid_disks - 1) % raid_disks;

			*dd_idx = (pd_idx + 1 + *dd_idx) % raid_disks;

			ddf_layout = 1;

			break;



		case ALGORITHM_LEFT_ASYMMETRIC_6:
@@ -1454,6 +1464,7 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector, 
	if (sh) {

		sh->pd_idx = pd_idx;

		sh->qd_idx = qd_idx;

		sh->ddf_layout = ddf_layout;

	}

	/*

	 * Finally, compute the new sector number
@@ -1642,9 +1653,10 @@ static void compute_parity6(struct stripe_head *sh, int method) 
{

	raid5_conf_t *conf = sh->raid_conf;

	int i, pd_idx, qd_idx, d0_idx, disks = sh->disks, count;

	int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);

	struct bio *chosen;

	/**** FIX THIS: This could be very bad if disks is close to 256 ****/

	void *ptrs[disks];

	void *ptrs[syndrome_disks+2];



	pd_idx = sh->pd_idx;

	qd_idx = sh->qd_idx;
@@ -1687,23 +1699,28 @@ static void compute_parity6(struct stripe_head *sh, int method) 
		}



	/* Note that unlike RAID-5, the ordering of the disks matters greatly.*/

	/* FIX: Is this ordering of drives even remotely optimal? */



	for (i = 0; i < disks; i++)

		ptrs[i] = (void *)raid6_empty_zero_page;



	count = 0;

	i = d0_idx;

	do {

		int slot = raid6_idx_to_slot(i, sh, &count);

		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);



		ptrs[slot] = page_address(sh->dev[i].page);

		if (slot < sh->disks - 2 &&

		if (slot < syndrome_disks &&

		    !test_bit(R5_UPTODATE, &sh->dev[i].flags)) {

			printk(KERN_ERR "block %d/%d not uptodate "

			       "on parity calc\n", i, count);

			BUG();

		}



		i = raid6_next_disk(i, disks);

	} while (i != d0_idx);

	BUG_ON(count+2 != disks);

	BUG_ON(count != syndrome_disks);



	raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);

	raid6_call.gen_syndrome(syndrome_disks+2, STRIPE_SIZE, ptrs);



	switch(method) {

	case RECONSTRUCT_WRITE:
@@ -1761,24 +1778,28 @@ static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero) 
static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)

{

	int i, count, disks = sh->disks;

	int syndrome_disks = sh->ddf_layout ? disks : disks-2;

	int d0_idx = raid6_d0(sh);

	int faila = -1, failb = -1;

	/**** FIX THIS: This could be very bad if disks is close to 256 ****/

	void *ptrs[disks];

	void *ptrs[syndrome_disks+2];



	for (i = 0; i < disks ; i++)

		ptrs[i] = (void *)raid6_empty_zero_page;

	count = 0;

	i = d0_idx;

	do {

		int slot;

		slot = raid6_idx_to_slot(i, sh, &count);

		int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);



		ptrs[slot] = page_address(sh->dev[i].page);



		if (i == dd_idx1)

			faila = slot;

		if (i == dd_idx2)

			failb = slot;

		i = raid6_next_disk(i, disks);

	} while (i != d0_idx);

	BUG_ON(count+2 != disks);

	BUG_ON(count != syndrome_disks);



	BUG_ON(faila == failb);

	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
@@ -1787,9 +1808,9 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2) 
		 (unsigned long long)sh->sector, dd_idx1, dd_idx2,

		 faila, failb);



	if ( failb == disks-1 ) {

	if (failb == syndrome_disks+1) {

		/* Q disk is one of the missing disks */

		if ( faila == disks-2 ) {

		if (faila == syndrome_disks) {

			/* Missing P+Q, just recompute */

			compute_parity6(sh, UPDATE_PARITY);

			return;
@@ -1804,12 +1825,13 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2) 
	}



	/* We're missing D+P or D+D; */

	if (failb == disks-2) {

	if (failb == syndrome_disks) {

		/* We're missing D+P. */

		raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);

		raid6_datap_recov(syndrome_disks+2, STRIPE_SIZE, faila, ptrs);

	} else {

		/* We're missing D+D. */

		raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);

		raid6_2data_recov(syndrome_disks+2, STRIPE_SIZE, faila, failb,

				  ptrs);

	}



	/* Both the above update both missing blocks */

drivers/md/raid5.h

+1 −0
Original line number Diff line number Diff line
@@ -201,6 +201,7 @@ struct stripe_head { 
	sector_t		sector;		/* sector of this row */

	short			pd_idx;		/* parity disk index */

	short			qd_idx;		/* 'Q' disk index for raid6 */

	short			ddf_layout;/* use DDF ordering to calculate Q */

	unsigned long		state;		/* state flags */

	atomic_t		count;	      /* nr of active thread/requests */

	spinlock_t		lock;

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