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authorAndre Noll <maan@systemlinux.org>2009-06-16 08:18:43 +0200
committerNeilBrown <neilb@suse.de>2009-06-16 08:18:43 +0200
commitdc58266385e51420298275c90a616c34f1473a73 (patch)
treef7532a7886f71c0b4e863033e95f8b57fb1ca1f2 /drivers/md/raid0.c
parentMerge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/sam/kb... (diff)
downloadlinux-dc58266385e51420298275c90a616c34f1473a73.tar.xz
linux-dc58266385e51420298275c90a616c34f1473a73.zip
md: raid0: Replace hash table lookup by looping over all strip_zones.
The number of strip_zones of a raid0 array is bounded by the number of drives in the array and is in fact much smaller for typical setups. For example, any raid0 array containing identical disks will have only a single strip_zone. Therefore, the hash tables which are used for quickly finding the strip_zone that holds a particular sector are of questionable value and add quite a bit of unnecessary complexity. This patch replaces the hash table lookup by equivalent code which simply loops over all strip zones to find the zone that holds the given sector. In order to make this loop as fast as possible, the zone->start field of struct strip_zone has been renamed to zone_end, and it now stores the beginning of the next zone in sectors. This allows to save one addition in the loop. Subsequent cleanup patches will remove the hash table structure. Signed-off-by: Andre Noll <maan@systemlinux.org> Signed-off-by: NeilBrown <neilb@suse.de>
Diffstat (limited to 'drivers/md/raid0.c')
-rw-r--r--drivers/md/raid0.c40
1 files changed, 20 insertions, 20 deletions
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 925507e7d673..bb245a6d16c8 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -52,7 +52,6 @@ static int raid0_congested(void *data, int bits)
return ret;
}
-
static int create_strip_zones (mddev_t *mddev)
{
int i, c, j;
@@ -158,7 +157,7 @@ static int create_strip_zones (mddev_t *mddev)
}
zone->nb_dev = cnt;
zone->sectors = smallest->sectors * cnt;
- zone->zone_start = 0;
+ zone->zone_end = zone->sectors;
current_start = smallest->sectors;
curr_zone_start = zone->sectors;
@@ -198,14 +197,13 @@ static int create_strip_zones (mddev_t *mddev)
printk(KERN_INFO "raid0: zone->nb_dev: %d, sectors: %llu\n",
zone->nb_dev, (unsigned long long)zone->sectors);
- zone->zone_start = curr_zone_start;
+ zone->zone_end = curr_zone_start + zone->sectors;
curr_zone_start += zone->sectors;
current_start = smallest->sectors;
printk(KERN_INFO "raid0: current zone start: %llu\n",
(unsigned long long)current_start);
}
-
/* Now find appropriate hash spacing.
* We want a number which causes most hash entries to cover
* at most two strips, but the hash table must be at most
@@ -398,6 +396,19 @@ static int raid0_stop (mddev_t *mddev)
return 0;
}
+/* Find the zone which holds a particular offset */
+static struct strip_zone *find_zone(struct raid0_private_data *conf,
+ sector_t sector)
+{
+ int i;
+ struct strip_zone *z = conf->strip_zone;
+
+ for (i = 0; i < conf->nr_strip_zones; i++)
+ if (sector < z[i].zone_end)
+ return z + i;
+ BUG();
+}
+
static int raid0_make_request (struct request_queue *q, struct bio *bio)
{
mddev_t *mddev = q->queuedata;
@@ -443,22 +454,11 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
bio_pair_release(bp);
return 0;
}
-
-
- {
- sector_t x = sector >> conf->sector_shift;
- sector_div(x, (u32)conf->spacing);
- zone = conf->hash_table[x];
- }
-
- while (sector >= zone->zone_start + zone->sectors)
- zone++;
-
+ zone = find_zone(conf, sector);
sect_in_chunk = bio->bi_sector & (chunk_sects - 1);
-
-
{
- sector_t x = (sector - zone->zone_start) >> chunksect_bits;
+ sector_t x = (zone->sectors + sector - zone->zone_end)
+ >> chunksect_bits;
sector_div(x, zone->nb_dev);
chunk = x;
@@ -503,8 +503,8 @@ static void raid0_status (struct seq_file *seq, mddev_t *mddev)
seq_printf(seq, "%s/", bdevname(
conf->strip_zone[j].dev[k]->bdev,b));
- seq_printf(seq, "] zs=%d ds=%d s=%d\n",
- conf->strip_zone[j].zone_start,
+ seq_printf(seq, "] ze=%d ds=%d s=%d\n",
+ conf->strip_zone[j].zone_end,
conf->strip_zone[j].dev_start,
conf->strip_zone[j].sectors);
}