md: raid0 :Enables chunk size other than powers of 2.

Maintain two flows, one for pow2 chunk sizes (which uses masks and
shift), and a flow for the general case (which uses sector_div).
This is for the sake of performance.

 - introduce map_sector and is_io_in_chunk_boundary to encapsulate
   those two flows better for raid0_make_request
 - fix blk_mergeable to support the two flows.

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

1 files changed, 77 insertions, 30 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 39936a217f95..7cd2671cc794 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -273,7 +273,12 @@ static int raid0_mergeable_bvec(struct request_queue *q,
         unsigned int chunk_sectors = mddev->chunk_size >> 9;
         unsigned int bio_sectors = bvm->bi_size >> 9;
 
-        max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
+        if (is_power_of_2(mddev->chunk_size))
+                max =  (chunk_sectors - ((sector & (chunk_sectors-1))
+                                                + bio_sectors)) << 9;
+        else
+                max =  (chunk_sectors - (sector_div(sector, chunk_sectors)
+                                                + bio_sectors)) << 9;
         if (max < 0) max = 0; /* bio_add cannot handle a negative return */
         if (max <= biovec->bv_len && bio_sectors == 0)
                 return biovec->bv_len;
@@ -299,9 +304,8 @@ static int raid0_run(mddev_t *mddev)
 {
         int ret;
 
-        if (mddev->chunk_size == 0 ||
-            !is_power_of_2(mddev->chunk_size)) {
-                printk(KERN_ERR "md/raid0: chunk size must be a power of 2.\n");
+        if (mddev->chunk_size == 0) {
+                printk(KERN_ERR "md/raid0: chunk size must be set.\n");
                 return -EINVAL;
         }
         blk_queue_max_sectors(mddev->queue, mddev->chunk_size >> 9);
@@ -367,15 +371,65 @@ static struct strip_zone *find_zone(struct raid0_private_data *conf,
         BUG();
 }
 
-static int raid0_make_request (struct request_queue *q, struct bio *bio)
+/*
+ * remaps the bio to the target device. we separate two flows.
+ * power 2 flow and a general flow for the sake of perfromance
+*/
+static mdk_rdev_t *map_sector(mddev_t *mddev, struct strip_zone *zone,
+                                sector_t sector, sector_t *sector_offset)
 {
-        mddev_t *mddev = q->queuedata;
-        unsigned int sect_in_chunk, chunksect_bits, chunk_sects;
+        unsigned int sect_in_chunk;
+        sector_t chunk;
         raid0_conf_t *conf = mddev->private;
+        unsigned int chunk_sects = mddev->chunk_size >> 9;
+
+        if (is_power_of_2(mddev->chunk_size)) {
+                int chunksect_bits = ffz(~chunk_sects);
+                /* find the sector offset inside the chunk */
+                sect_in_chunk  = sector & (chunk_sects - 1);
+                sector >>= chunksect_bits;
+                /* chunk in zone */
+                chunk = *sector_offset;
+                /* quotient is the chunk in real device*/
+                sector_div(chunk, zone->nb_dev << chunksect_bits);
+        } else{
+                sect_in_chunk = sector_div(sector, chunk_sects);
+                chunk = *sector_offset;
+                sector_div(chunk, chunk_sects * zone->nb_dev);
+        }
+        /*
+        *  position the bio over the real device
+        *  real sector = chunk in device + starting of zone
+        *       + the position in the chunk
+        */
+        *sector_offset = (chunk * chunk_sects) + sect_in_chunk;
+        return conf->devlist[(zone - conf->strip_zone)*mddev->raid_disks
+                             + sector_div(sector, zone->nb_dev)];
+}
+
+/*
+ * Is io distribute over 1 or more chunks ?
+*/
+static inline int is_io_in_chunk_boundary(mddev_t *mddev,
+                        unsigned int chunk_sects, struct bio *bio)
+{
+        if (likely(is_power_of_2(mddev->chunk_size))) {
+                return chunk_sects >= ((bio->bi_sector & (chunk_sects-1))
+                                        + (bio->bi_size >> 9));
+        } else{
+                sector_t sector = bio->bi_sector;
+                return chunk_sects >= (sector_div(sector, chunk_sects)
+                                                + (bio->bi_size >> 9));
+        }
+}
+
+static int raid0_make_request(struct request_queue *q, struct bio *bio)
+{
+        mddev_t *mddev = q->queuedata;
+        unsigned int chunk_sects;
+        sector_t sector_offset;
         struct strip_zone *zone;
         mdk_rdev_t *tmp_dev;
-        sector_t chunk;
-        sector_t sector, rsect, sector_offset;
         const int rw = bio_data_dir(bio);
         int cpu;
 
@@ -391,10 +445,8 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
         part_stat_unlock();
 
         chunk_sects = mddev->chunk_size >> 9;
-        chunksect_bits = ffz(~chunk_sects);
-        sector = bio->bi_sector;
-
-        if (unlikely(chunk_sects < (bio->bi_sector & (chunk_sects - 1)) + (bio->bi_size >> 9))) {
+        if (unlikely(!is_io_in_chunk_boundary(mddev, chunk_sects, bio))) {
+                sector_t sector = bio->bi_sector;
                 struct bio_pair *bp;
                 /* Sanity check -- queue functions should prevent this happening */
                 if (bio->bi_vcnt != 1 ||
@@ -403,7 +455,12 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
                 /* This is a one page bio that upper layers
                  * refuse to split for us, so we need to split it.
                  */
-                bp = bio_split(bio, chunk_sects - (bio->bi_sector & (chunk_sects - 1)));
+                if (likely(is_power_of_2(mddev->chunk_size)))
+                        bp = bio_split(bio, chunk_sects - (sector &
+                                                           (chunk_sects-1)));
+                else
+                        bp = bio_split(bio, chunk_sects -
+                                       sector_div(sector, chunk_sects));
                 if (raid0_make_request(q, &bp->bio1))
                         generic_make_request(&bp->bio1);
                 if (raid0_make_request(q, &bp->bio2))
@@ -412,24 +469,14 @@ static int raid0_make_request (struct request_queue *q, struct bio *bio)
                 bio_pair_release(bp);
                 return 0;
         }
-        sector_offset = sector;
-        zone = find_zone(conf, &sector_offset);
-        sect_in_chunk = bio->bi_sector & (chunk_sects - 1);
-        {
-                sector_t x = sector_offset >> chunksect_bits;
-
-                sector_div(x, zone->nb_dev);
-                chunk = x;
 
-                x = sector >> chunksect_bits;
-                tmp_dev = conf->devlist[(zone - conf->strip_zone)*mddev->raid_disks
-                                        + sector_div(x, zone->nb_dev)];
-        }
-        rsect = (chunk << chunksect_bits) + zone->dev_start + sect_in_chunk;
- 
+        sector_offset = bio->bi_sector;
+        zone =  find_zone(mddev->private, &sector_offset);
+        tmp_dev = map_sector(mddev, zone, bio->bi_sector,
+                             &sector_offset);
         bio->bi_bdev = tmp_dev->bdev;
-        bio->bi_sector = rsect + tmp_dev->data_offset;
-
+        bio->bi_sector = sector_offset + zone->dev_start +
+                tmp_dev->data_offset;
         /*
          * Let the main block layer submit the IO and resolve recursion:
          */