Commit c93983bf authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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[PATCH] md: support stripe/offset mode in raid10 



The "industry standard" DDF format allows for a stripe/offset layout where
data is duplicated on different stripes.  e.g.

  A  B  C  D
  D  A  B  C
  E  F  G  H
  H  E  F  G

(columns are drives, rows are stripes, LETTERS are chunks of data).

This is similar to raid10's 'far' mode, but not quite the same.  So enhance
'far' mode with a 'far/offset' option which follows the layout of DDFs
stripe/offset.

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7c7546cc

drivers/md/raid10.c

+43 −21
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 
 *    raid_disks

 *    near_copies (stored in low byte of layout)

 *    far_copies (stored in second byte of layout)

 *    far_offset (stored in bit 16 of layout )

 *

 * The data to be stored is divided into chunks using chunksize.

 * Each device is divided into far_copies sections.
@@ -36,10 +37,14 @@ 
 * near_copies copies of each chunk is stored (each on a different drive).

 * The starting device for each section is offset near_copies from the starting

 * device of the previous section.

 * Thus there are (near_copies*far_copies) of each chunk, and each is on a different

 * Thus they are (near_copies*far_copies) of each chunk, and each is on a different

 * drive.

 * near_copies and far_copies must be at least one, and their product is at most

 * raid_disks.

 *

 * If far_offset is true, then the far_copies are handled a bit differently.

 * The copies are still in different stripes, but instead of be very far apart

 * on disk, there are adjacent stripes.

 */



/*
@@ -357,8 +362,7 @@ static int raid10_end_write_request(struct bio *bio, unsigned int bytes_done, in 
 * With this layout, and block is never stored twice on the one device.

 *

 * raid10_find_phys finds the sector offset of a given virtual sector

 * on each device that it is on. If a block isn't on a device,

 * that entry in the array is set to MaxSector.

 * on each device that it is on.

 *

 * raid10_find_virt does the reverse mapping, from a device and a

 * sector offset to a virtual address
@@ -381,6 +385,8 @@ static void raid10_find_phys(conf_t *conf, r10bio_t *r10bio) 
	chunk *= conf->near_copies;

	stripe = chunk;

	dev = sector_div(stripe, conf->raid_disks);

	if (conf->far_offset)

		stripe *= conf->far_copies;



	sector += stripe << conf->chunk_shift;
@@ -414,6 +420,15 @@ static sector_t raid10_find_virt(conf_t *conf, sector_t sector, int dev) 
{

	sector_t offset, chunk, vchunk;



	offset = sector & conf->chunk_mask;

	if (conf->far_offset) {

		int fc;

		chunk = sector >> conf->chunk_shift;

		fc = sector_div(chunk, conf->far_copies);

		dev -= fc * conf->near_copies;

		if (dev < 0)

			dev += conf->raid_disks;

	} else {

		while (sector > conf->stride) {

			sector -= conf->stride;

			if (dev < conf->near_copies)
@@ -421,9 +436,8 @@ static sector_t raid10_find_virt(conf_t *conf, sector_t sector, int dev) 
			else

				dev -= conf->near_copies;

		}



	offset = sector & conf->chunk_mask;

		chunk = sector >> conf->chunk_shift;

	}

	vchunk = chunk * conf->raid_disks + dev;

	sector_div(vchunk, conf->near_copies);

	return (vchunk << conf->chunk_shift) + offset;
@@ -900,9 +914,12 @@ static void status(struct seq_file *seq, mddev_t *mddev) 
		seq_printf(seq, " %dK chunks", mddev->chunk_size/1024);

	if (conf->near_copies > 1)

		seq_printf(seq, " %d near-copies", conf->near_copies);

	if (conf->far_copies > 1)

	if (conf->far_copies > 1) {

		if (conf->far_offset)

			seq_printf(seq, " %d offset-copies", conf->far_copies);

		else

			seq_printf(seq, " %d far-copies", conf->far_copies);



	}

	seq_printf(seq, " [%d/%d] [", conf->raid_disks,

						conf->working_disks);

	for (i = 0; i < conf->raid_disks; i++)
@@ -1915,7 +1932,7 @@ static int run(mddev_t *mddev) 
	mirror_info_t *disk;

	mdk_rdev_t *rdev;

	struct list_head *tmp;

	int nc, fc;

	int nc, fc, fo;

	sector_t stride, size;



	if (mddev->chunk_size == 0) {
@@ -1925,8 +1942,9 @@ static int run(mddev_t *mddev) 


	nc = mddev->layout & 255;

	fc = (mddev->layout >> 8) & 255;

	fo = mddev->layout & (1<<16);

	if ((nc*fc) <2 || (nc*fc) > mddev->raid_disks ||

	    (mddev->layout >> 16)) {

	    (mddev->layout >> 17)) {

		printk(KERN_ERR "raid10: %s: unsupported raid10 layout: 0x%8x\n",

		       mdname(mddev), mddev->layout);

		goto out;
@@ -1958,12 +1976,16 @@ static int run(mddev_t *mddev) 
	conf->near_copies = nc;

	conf->far_copies = fc;

	conf->copies = nc*fc;

	conf->far_offset = fo;

	conf->chunk_mask = (sector_t)(mddev->chunk_size>>9)-1;

	conf->chunk_shift = ffz(~mddev->chunk_size) - 9;

	if (fo)

		conf->stride = 1 << conf->chunk_shift;

	else {

		stride = mddev->size >> (conf->chunk_shift-1);

		sector_div(stride, fc);

		conf->stride = stride << conf->chunk_shift;



	}

	conf->r10bio_pool = mempool_create(NR_RAID10_BIOS, r10bio_pool_alloc,

						r10bio_pool_free, conf);

	if (!conf->r10bio_pool) {

include/linux/raid/raid10.h

+6 −1
Original line number Diff line number Diff line
@@ -24,11 +24,16 @@ struct r10_private_data_s { 
	int 			far_copies;   /* number of copies layed out

					       * at large strides across drives

					       */

	int			far_offset;   /* far_copies are offset by 1 stripe

					       * instead of many

					       */

	int			copies;	      /* near_copies * far_copies.

					       * must be <= raid_disks

					       */

	sector_t		stride;	      /* distance between far copies.

					       * This is size / far_copies

					       * This is size / far_copies unless

					       * far_offset, in which case it is

					       * 1 stripe.

					       */



	int chunk_shift; /* shift from chunks to sectors */