From: NeilBrown <neilb@cse.unsw.edu.au>
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: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
drivers/md/linear.c | 99 ++++++++++++++++++++++++++++++--------------
include/linux/raid/linear.h | 4 -
2 files changed, 70 insertions(+), 33 deletions(-)
diff -puN drivers/md/linear.c~md-support-md-linear-array-with-components-greater-than-2-terabytes drivers/md/linear.c
--- devel/drivers/md/linear.c~md-support-md-linear-array-with-components-greater-than-2-terabytes 2005-08-21 22:35:53.000000000 -0700
+++ devel-akpm/drivers/md/linear.c 2005-08-21 22:35:53.000000000 -0700
@@ -38,7 +38,8 @@ static inline dev_info_t *which_dev(mdde
/*
* 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(mdde
}
/**
- * 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);
}
-
- conf->hash_table = kmalloc (sizeof (dev_info_t*) * nb_zone,
+ BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
+
+ 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;
-
- disk->offset = curr_offset;
- curr_offset += disk->size;
-
- /* 'curr_offset' is the end of this disk
- * 'start' is the start of table
+ i = 0;
+ for (curr_offset = 0;
+ curr_offset < mddev->array_size;
+ curr_offset += conf->hash_spacing) {
+
+ while (i < mddev->raid_disks-1 &&
+ curr_offset >= conf->disks[i+1].offset)
+ i++;
+
+ *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.
*/
- while (start < curr_offset) {
- *table++ = disk;
- start += conf->smallest->size;
- }
+ 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_fi
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;
diff -puN include/linux/raid/linear.h~md-support-md-linear-array-with-components-greater-than-2-terabytes include/linux/raid/linear.h
--- devel/include/linux/raid/linear.h~md-support-md-linear-array-with-components-greater-than-2-terabytes 2005-08-21 22:35:53.000000000 -0700
+++ devel-akpm/include/linux/raid/linear.h 2005-08-21 22:35:53.000000000 -0700
@@ -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];
};
_