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authorAndre Noll <maan@systemlinux.org>2009-06-16 16:18:43 +1000
committerNeilBrown <neilb@suse.de>2009-06-16 16:18:43 +1000
commitdc58266385e51420298275c90a616c34f1473a73 (patch)
treef7532a7886f71c0b4e863033e95f8b57fb1ca1f2
parent45e3e1935e2857c54783291107d33323b3ef33c8 (diff)
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>
-rw-r--r--drivers/md/raid0.c40
-rw-r--r--drivers/md/raid0.h2
2 files changed, 21 insertions, 21 deletions
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 925507e7d67..bb245a6d16c 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);
}
diff --git a/drivers/md/raid0.h b/drivers/md/raid0.h
index 824b12eb1d4..556666fec3a 100644
--- a/drivers/md/raid0.h
+++ b/drivers/md/raid0.h
@@ -3,7 +3,7 @@
struct strip_zone
{
- sector_t zone_start; /* Zone offset in md_dev (in sectors) */
+ sector_t zone_end; /* Start of the next zone (in sectors) */
sector_t dev_start; /* Zone offset in real dev (in sectors) */
sector_t sectors; /* Zone size in sectors */
int nb_dev; /* # of devices attached to the zone */