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>

2 files changed, 19 insertions, 15 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 0d62ad6df212..07ef936afc71 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -55,7 +55,7 @@ static int raid0_congested(void *data, int bits)
 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 @@ static int create_strip_zones(mddev_t *mddev)
                 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 @@ static int create_strip_zones(mddev_t *mddev)
                 }
 
                 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 @@ static int raid0_stop(mddev_t *mddev)
         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 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
         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 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
                 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;
diff --git a/drivers/md/raid0.h b/drivers/md/raid0.h
index dbcf1da916b7..124ba34c8eed 100644
--- a/drivers/md/raid0.h
+++ b/drivers/md/raid0.h
@@ -5,7 +5,6 @@ struct strip_zone
 {
         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 */
         mdk_rdev_t **dev;       /* Devices attached to the zone */
 };