From ab5bd5cbc8d4b868378d062eed3d4240930fbb86 Mon Sep 17 00:00:00 2001 From: Andre Noll Date: Mon, 13 Oct 2008 11:55:12 +1100 Subject: md: Convert remaining 1k representations in linear.c to sectors. This patch renames hash_spacing and preshift to spacing and sector_shift respectively with the following change of semantics: Case 1: (sizeof(sector_t) <= sizeof(u32)). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In this case, we have sector_shift = preshift = 0 and spacing = 2 * hash_spacing. Hence, the index for the hash table which is computed by the new code in which_dev() as sector / spacing equals the old value which was (sector/2) / hash_spacing. Note also that the value of nb_zone stays the same because both sz and base double. Case 2: (sizeof(sector_t) > sizeof(u32)). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (aka the shifting dance case). Here we have sector_shift = preshift + 1 and spacing = 2 * hash_spacing during the computation of nb_zone and curr_sector, but spacing = hash_spacing in which_dev() because in the last hunk of the patch for linear.c we shift down conf->spacing (= 2 * hash_spacing) by one more bit than in the old code. Hence in the computation of nb_zone, sz and base have the same value as before, so nb_zone is not affected. Also curr_sector in the next hunk stays the same. In which_dev() the hash table index is computed as (sector >> sector_shift) / spacing In view of sector_shift = preshift + 1 and spacing = hash_spacing, this equals ((sector/2) >> preshift) / hash_spacing which is the value computed by the old code. Signed-off-by: Andre Noll Signed-off-by: NeilBrown --- drivers/md/linear.c | 35 +++++++++++++++++------------------ 1 file changed, 17 insertions(+), 18 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/linear.c b/drivers/md/linear.c index 13e928bde7c..09a64b9cbde 100644 --- a/drivers/md/linear.c +++ b/drivers/md/linear.c @@ -33,14 +33,13 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector) { dev_info_t *hash; linear_conf_t *conf = mddev_to_conf(mddev); - sector_t block = sector >> 1; /* * sector_div(a,b) returns the remainer and sets a to a/b */ - block >>= conf->preshift; - (void)sector_div(block, conf->hash_spacing); - hash = conf->hash_table[block]; + sector >>= conf->sector_shift; + (void)sector_div(sector, conf->spacing); + hash = conf->hash_table[sector]; while (sector >= hash->num_sectors + hash->start_sector) hash++; @@ -164,25 +163,25 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) * that is larger than min_sectors and use the size of that as * the actual spacing */ - conf->hash_spacing = conf->array_sectors / 2; + 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->hash_spacing * 2) - conf->hash_spacing = tmp / 2; + if (tmp >= min_sectors && tmp < conf->spacing) + conf->spacing = tmp; } - /* hash_spacing may be too large for sector_div to work with, + /* spacing may be too large for sector_div to work with, * so we might need to pre-shift */ - conf->preshift = 0; + conf->sector_shift = 0; if (sizeof(sector_t) > sizeof(u32)) { - sector_t space = conf->hash_spacing; + sector_t space = conf->spacing; while (space > (sector_t)(~(u32)0)) { space >>= 1; - conf->preshift++; + conf->sector_shift++; } } /* @@ -194,9 +193,9 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) unsigned round; unsigned long base; - sz = conf->array_sectors >> (conf->preshift + 1); + sz = conf->array_sectors >> conf->sector_shift; sz += 1; /* force round-up */ - base = conf->hash_spacing >> conf->preshift; + base = conf->spacing >> conf->sector_shift; round = sector_div(sz, base); nb_zone = sz + (round ? 1 : 0); } @@ -221,7 +220,7 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) i = 0; for (curr_sector = 0; curr_sector < conf->array_sectors; - curr_sector += conf->hash_spacing * 2) { + curr_sector += conf->spacing) { while (i < raid_disks-1 && curr_sector >= conf->disks[i+1].start_sector) @@ -230,12 +229,12 @@ static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks) *table ++ = conf->disks + i; } - if (conf->preshift) { - conf->hash_spacing >>= conf->preshift; - /* round hash_spacing up so that when we divide by it, + 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->hash_spacing++; + conf->spacing++; } BUG_ON(table - conf->hash_table > nb_zone); -- cgit v1.2.3