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author | Sandeep K Sinha <sandeepksinha@gmail.com> | 2009-06-16 16:55:26 +1000 |
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committer | NeilBrown <neilb@suse.de> | 2009-06-16 16:55:26 +1000 |
commit | 45d4582f219619e368ea91ea1189085e1c5f1969 (patch) | |
tree | 15c38d1090d67ecb600c395a5155f2630804d851 /drivers/md/linear.c | |
parent | 070ec55d07157a3041f92654135c3c6e2eaaf901 (diff) | |
download | kernel_samsung_smdk4412-45d4582f219619e368ea91ea1189085e1c5f1969.zip kernel_samsung_smdk4412-45d4582f219619e368ea91ea1189085e1c5f1969.tar.gz kernel_samsung_smdk4412-45d4582f219619e368ea91ea1189085e1c5f1969.tar.bz2 |
md: Removal of hash table in linear raid
Get rid of sector_div and hash table for linear raid and replace
with a linear search in which_dev.
The hash table adds a lot of complexity for little if any gain.
Ultimately a binary search will be used which will have smaller
cache foot print, a similar number of memory access, and no
divisions.
Signed-off-by: Sandeep K Sinha <sandeepksinha@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/linear.c')
-rw-r--r-- | drivers/md/linear.c | 93 |
1 files changed, 3 insertions, 90 deletions
diff --git a/drivers/md/linear.c b/drivers/md/linear.c index 31f8ec7..92bcd3d 100644 --- a/drivers/md/linear.c +++ b/drivers/md/linear.c @@ -29,13 +29,8 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector) { dev_info_t *hash; linear_conf_t *conf = mddev->private; - sector_t idx = sector >> conf->sector_shift; - /* - * sector_div(a,b) returns the remainer and sets a to a/b - */ - (void)sector_div(idx, conf->spacing); - hash = conf->hash_table[idx]; + hash = conf->disks; while (sector >= hash->num_sectors + hash->start_sector) hash++; @@ -114,11 +109,8 @@ static sector_t linear_size(mddev_t *mddev, sector_t sectors, int raid_disks) static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) { linear_conf_t *conf; - dev_info_t **table; mdk_rdev_t *rdev; - int i, nb_zone, cnt; - sector_t min_sectors; - sector_t curr_sector; + int i, cnt; conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t), GFP_KERNEL); @@ -159,63 +151,8 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) goto out; } - min_sectors = conf->array_sectors; - sector_div(min_sectors, PAGE_SIZE/sizeof(struct dev_info *)); - if (min_sectors == 0) - min_sectors = 1; - - /* min_sectors 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_sectors and use the size of that as - * the actual spacing - */ - conf->spacing = conf->array_sectors; - for (i=0; i < cnt-1 ; i++) { - sector_t tmp = 0; - int j; - for (j = i; j < cnt - 1 && tmp < min_sectors; j++) - tmp += conf->disks[j].num_sectors; - if (tmp >= min_sectors && tmp < conf->spacing) - conf->spacing = tmp; - } - - /* spacing may be too large for sector_div to work with, - * so we might need to pre-shift - */ - conf->sector_shift = 0; - if (sizeof(sector_t) > sizeof(u32)) { - sector_t space = conf->spacing; - while (space > (sector_t)(~(u32)0)) { - space >>= 1; - conf->sector_shift++; - } - } /* - * This code was restructured to work around a gcc-2.95.3 internal - * compiler error. Alter it with care. - */ - { - sector_t sz; - unsigned round; - unsigned long base; - - sz = conf->array_sectors >> conf->sector_shift; - sz += 1; /* force round-up */ - base = conf->spacing >> conf->sector_shift; - round = sector_div(sz, base); - nb_zone = sz + (round ? 1 : 0); - } - 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. + * Here we calculate the device offsets. */ conf->disks[0].start_sector = 0; for (i = 1; i < raid_disks; i++) @@ -223,29 +160,6 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) conf->disks[i-1].start_sector + conf->disks[i-1].num_sectors; - table = conf->hash_table; - i = 0; - for (curr_sector = 0; - curr_sector < conf->array_sectors; - curr_sector += conf->spacing) { - - while (i < raid_disks-1 && - curr_sector >= conf->disks[i+1].start_sector) - i++; - - *table ++ = conf->disks + i; - } - - if (conf->sector_shift) { - conf->spacing >>= conf->sector_shift; - /* round spacing up so that when we divide by it, - * we err on the side of "too-low", which is safest. - */ - conf->spacing++; - } - - BUG_ON(table - conf->hash_table > nb_zone); - return conf; out: @@ -309,7 +223,6 @@ static int linear_stop (mddev_t *mddev) blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/ do { linear_conf_t *t = conf->prev; - kfree(conf->hash_table); kfree(conf); conf = t; } while (conf); |