Commit 15945fee authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
Browse files

[PATCH] md: support md/linear array with components greater than 2 terabytes. 



linear currently uses division by the size of the smallest componenet device
to find which device a request goes to.  If that smallest device is larger
than 2 terabytes, then the division will not work on some systems.

So we introduce a pre-shift, and take care not to make the hash table too
large, much like the code in raid0.

Also get rid of conf->nr_zones, which is not needed.

Signed-off-by: default avatarNeil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4b6d287f

drivers/md/linear.c

+66 −29
Original line number Diff line number Diff line
@@ -38,7 +38,8 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector) 
	/*

	 * sector_div(a,b) returns the remainer and sets a to a/b

	 */

	(void)sector_div(block, conf->smallest->size);

	block >>= conf->preshift;

	(void)sector_div(block, conf->hash_spacing);

	hash = conf->hash_table[block];



	while ((sector>>1) >= (hash->size + hash->offset))
@@ -47,7 +48,7 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector) 
}



/**

 *	linear_mergeable_bvec -- tell bio layer if a two requests can be merged

 *	linear_mergeable_bvec -- tell bio layer if two requests can be merged

 *	@q: request queue

 *	@bio: the buffer head that's been built up so far

 *	@biovec: the request that could be merged to it.
@@ -116,7 +117,7 @@ static int linear_run (mddev_t *mddev) 
	dev_info_t **table;

	mdk_rdev_t *rdev;

	int i, nb_zone, cnt;

	sector_t start;

	sector_t min_spacing;

	sector_t curr_offset;

	struct list_head *tmp;
@@ -127,11 +128,6 @@ static int linear_run (mddev_t *mddev) 
	memset(conf, 0, sizeof(*conf) + mddev->raid_disks*sizeof(dev_info_t));

	mddev->private = conf;



	/*

	 * Find the smallest device.

	 */



	conf->smallest = NULL;

	cnt = 0;

	mddev->array_size = 0;
@@ -159,8 +155,6 @@ static int linear_run (mddev_t *mddev) 
		disk->size = rdev->size;

		mddev->array_size += rdev->size;



		if (!conf->smallest || (disk->size < conf->smallest->size))

			conf->smallest = disk;

		cnt++;

	}

	if (cnt != mddev->raid_disks) {
@@ -168,6 +162,36 @@ static int linear_run (mddev_t *mddev) 
		goto out;

	}



	min_spacing = mddev->array_size;

	sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));



	/* min_spacing is the minimum spacing that will fit the hash

	 * table in one PAGE.  This may be much smaller than needed.

	 * We find the smallest non-terminal set of consecutive devices

	 * that is larger than min_spacing as use the size of that as

	 * the actual spacing

	 */

	conf->hash_spacing = mddev->array_size;

	for (i=0; i < cnt-1 ; i++) {

		sector_t sz = 0;

		int j;

		for (j=i; i<cnt-1 && sz < min_spacing ; j++)

			sz += conf->disks[j].size;

		if (sz >= min_spacing && sz < conf->hash_spacing)

			conf->hash_spacing = sz;

	}



	/* hash_spacing may be too large for sector_div to work with,

	 * so we might need to pre-shift

	 */

	conf->preshift = 0;

	if (sizeof(sector_t) > sizeof(u32)) {

		sector_t space = conf->hash_spacing;

		while (space > (sector_t)(~(u32)0)) {

			space >>= 1;

			conf->preshift++;

		}

	}

	/*

	 * This code was restructured to work around a gcc-2.95.3 internal

	 * compiler error.  Alter it with care.
@@ -177,39 +201,52 @@ static int linear_run (mddev_t *mddev) 
		unsigned round;

		unsigned long base;



		sz = mddev->array_size;

		base = conf->smallest->size;

		sz = mddev->array_size >> conf->preshift;

		sz += 1; /* force round-up */

		base = conf->hash_spacing >> conf->preshift;

		round = sector_div(sz, base);

		nb_zone = conf->nr_zones = sz + (round ? 1 : 0);

		nb_zone = sz + (round ? 1 : 0);

	}

	BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));



	conf->hash_table = kmalloc (sizeof (dev_info_t*) * nb_zone,

	conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,

					GFP_KERNEL);

	if (!conf->hash_table)

		goto out;



	/*

	 * Here we generate the linear hash table

	 * First calculate the device offsets.

	 */

	conf->disks[0].offset = 0;

	for (i=1; i<mddev->raid_disks; i++)

		conf->disks[i].offset =

			conf->disks[i-1].offset +

			conf->disks[i-1].size;



	table = conf->hash_table;

	start = 0;

	curr_offset = 0;

	for (i = 0; i < cnt; i++) {

		dev_info_t *disk = conf->disks + i;

	i = 0;

	for (curr_offset = 0;

	     curr_offset < mddev->array_size;

	     curr_offset += conf->hash_spacing) {



		disk->offset = curr_offset;

		curr_offset += disk->size;

		while (i < mddev->raid_disks-1 &&

		       curr_offset >= conf->disks[i+1].offset)

			i++;



		/* 'curr_offset' is the end of this disk

		 * 'start' is the start of table

		 */

		while (start < curr_offset) {

			*table++ = disk;

			start += conf->smallest->size;

		*table ++ = conf->disks + i;

	}



	if (conf->preshift) {

		conf->hash_spacing >>= conf->preshift;

		/* round hash_spacing up so that when we divide by it,

		 * we err on the side of "too-low", which is safest.

		 */

		conf->hash_spacing++;

	}

	if (table-conf->hash_table != nb_zone)

		BUG();



	BUG_ON(table - conf->hash_table > nb_zone);



	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);

	mddev->queue->unplug_fn = linear_unplug;
@@ -299,7 +336,7 @@ static void linear_status (struct seq_file *seq, mddev_t *mddev) 
	sector_t s = 0;

  

	seq_printf(seq, "      ");

	for (j = 0; j < conf->nr_zones; j++)

	for (j = 0; j < mddev->raid_disks; j++)

	{

		char b[BDEVNAME_SIZE];

		s += conf->smallest_size;

include/linux/raid/linear.h

+2 −2
Original line number Diff line number Diff line
@@ -14,8 +14,8 @@ typedef struct dev_info dev_info_t; 
struct linear_private_data

{

	dev_info_t		**hash_table;

	dev_info_t		*smallest;

	int			nr_zones;

	sector_t		hash_spacing;

	int			preshift; /* shift before dividing by hash_spacing */

	dev_info_t		disks[0];

};

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