commit 49f357a22b3fa3eeac042dfa0a6cae920c174e48
author NeilBrown <neilb@suse.de> Tue Jun 16 16:50:35 2009 +1000
committer NeilBrown <neilb@suse.de> Tue Jun 16 16:50:35 2009 +1000
tree 55d90a158e990ea38c2487167c3d9a4f7f7943cf
parent fb5ab4b5d6e16fd5006c9f800d0116f3547cb760

md: raid0: remove ->sectors from the strip_zone structure.

storing ->sectors is redundant as is can be computed from the
difference  z->zone_end - (z-1)->zone_end

The one place where it is used, it is just as efficient to use
a zone_end value instead.

And removing it makes strip_zone smaller, so they array of these that
is searched on every request has a better chance to say in cache.

So discard the field and get the value from elsewhere.

Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/raid0.c

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 0d62ad6..07ef936 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -55,7 +55,7 @@
 static int create_strip_zones(mddev_t *mddev)
 {
 	int i, c, j, err;
-	sector_t curr_zone_end;
+	sector_t curr_zone_end, sectors;
 	mdk_rdev_t *smallest, *rdev1, *rdev2, *rdev;
 	struct strip_zone *zone;
 	int cnt;
@@ -153,10 +153,9 @@
 		goto abort;
 	}
 	zone->nb_dev = cnt;
-	zone->sectors = smallest->sectors * cnt;
-	zone->zone_end = zone->sectors;
+	zone->zone_end = smallest->sectors * cnt;
 
-	curr_zone_end = zone->sectors;
+	curr_zone_end = zone->zone_end;
 
 	/* now do the other zones */
 	for (i = 1; i < conf->nr_strip_zones; i++)
@@ -189,11 +188,11 @@
 		}
 
 		zone->nb_dev = c;
-		zone->sectors = (smallest->sectors - zone->dev_start) * c;
+		sectors = (smallest->sectors - zone->dev_start) * c;
 		printk(KERN_INFO "raid0: zone->nb_dev: %d, sectors: %llu\n",
-			zone->nb_dev, (unsigned long long)zone->sectors);
+			zone->nb_dev, (unsigned long long)sectors);
 
-		curr_zone_end += zone->sectors;
+		curr_zone_end += sectors;
 		zone->zone_end = curr_zone_end;
 
 		printk(KERN_INFO "raid0: current zone start: %llu\n",
@@ -310,16 +309,22 @@
 	return 0;
 }
 
-/* Find the zone which holds a particular offset */
+/* Find the zone which holds a particular offset
+ * Update *sectorp to be an offset in that zone
+ */
 static struct strip_zone *find_zone(struct raid0_private_data *conf,
-		sector_t sector)
+				    sector_t *sectorp)
 {
 	int i;
 	struct strip_zone *z = conf->strip_zone;
+	sector_t sector = *sectorp;
 
 	for (i = 0; i < conf->nr_strip_zones; i++)
-		if (sector < z[i].zone_end)
+		if (sector < z[i].zone_end) {
+			if (i)
+				*sectorp = sector - z[i-1].zone_end;
 			return z + i;
+		}
 	BUG();
 }
 
@@ -331,7 +336,7 @@
 	struct strip_zone *zone;
 	mdk_rdev_t *tmp_dev;
 	sector_t chunk;
-	sector_t sector, rsect;
+	sector_t sector, rsect, sector_offset;
 	const int rw = bio_data_dir(bio);
 	int cpu;
 
@@ -368,11 +373,11 @@
 		bio_pair_release(bp);
 		return 0;
 	}
-	zone = find_zone(conf, sector);
+	sector_offset = sector;
+	zone = find_zone(conf, &sector_offset);
 	sect_in_chunk = bio->bi_sector & (chunk_sects - 1);
 	{
-		sector_t x = (zone->sectors + sector - zone->zone_end)
-				>> chunksect_bits;
+		sector_t x = sector_offset >> chunksect_bits;
 
 		sector_div(x, zone->nb_dev);
 		chunk = x;