dm stripe: support for non power of 2 chunksize

Support non-power-of-2 chunk sizes with dm striping for proper alignment
of stripe IO on storage that has non-power-of-2 optimal IO sizes (e.g.
RAID6 10+2).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 19 insertions, 25 deletions

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 992c9d4c3bd9..9690daa11c83 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -30,9 +30,7 @@ struct stripe_c {
         /* The size of this target / num. stripes */
         sector_t stripe_width;
 
-        /* stripe chunk size */
-        uint32_t chunk_shift;
-        sector_t chunk_mask;
+        uint32_t chunk_size;
 
         /* Needed for handling events */
         struct dm_target *ti;
@@ -90,7 +88,7 @@ static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
 
 /*
  * Construct a striped mapping.
- * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
+ * <number of stripes> <chunk size> [<dev_path> <offset>]+
  */
 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
@@ -111,21 +109,14 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                 return -EINVAL;
         }
 
-        if (kstrtouint(argv[1], 10, &chunk_size)) {
-                ti->error = "Invalid chunk_size";
-                return -EINVAL;
-        }
-
-        /*
-         * chunk_size is a power of two
-         */
-        if (!is_power_of_2(chunk_size) ||
+        if (kstrtouint(argv[1], 10, &chunk_size) ||
             (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
-                ti->error = "Invalid chunk size";
+                ti->error = "Invalid chunk_size";
                 return -EINVAL;
         }
 
-        if (ti->len & (chunk_size - 1)) {
+        width = ti->len;
+        if (sector_div(width, chunk_size)) {
                 ti->error = "Target length not divisible by "
                     "chunk size";
                 return -EINVAL;
@@ -172,8 +163,7 @@ static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         ti->num_flush_requests = stripes;
         ti->num_discard_requests = stripes;
 
-        sc->chunk_shift = ffs(chunk_size) - 1;
-        sc->chunk_mask = ((sector_t) chunk_size) - 1;
+        sc->chunk_size = chunk_size;
 
         /*
          * Get the stripe destinations.
@@ -212,8 +202,8 @@ static void stripe_dtr(struct dm_target *ti)
 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
                               uint32_t *stripe, sector_t *result)
 {
-        sector_t offset = dm_target_offset(sc->ti, sector);
-        sector_t chunk = offset >> sc->chunk_shift;
+        sector_t chunk = dm_target_offset(sc->ti, sector);
+        sector_t chunk_offset = sector_div(chunk, sc->chunk_size);
 
         if (sc->stripes_shift < 0)
                 *stripe = sector_div(chunk, sc->stripes);
@@ -222,7 +212,7 @@ static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
                 chunk >>= sc->stripes_shift;
         }
 
-        *result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
+        *result = (chunk * sc->chunk_size) + chunk_offset;
 }
 
 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
@@ -233,9 +223,13 @@ static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
         stripe_map_sector(sc, sector, &stripe, result);
         if (stripe == target_stripe)
                 return;
-        *result &= ~sc->chunk_mask;                     /* round down */
+
+        /* round down */
+        sector = *result;
+        *result -= sector_div(sector, sc->chunk_size);
+
         if (target_stripe < stripe)
-                *result += sc->chunk_mask + 1;          /* next chunk */
+                *result += sc->chunk_size;              /* next chunk */
 }
 
 static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
@@ -320,7 +314,7 @@ static int stripe_status(struct dm_target *ti,
 
         case STATUSTYPE_TABLE:
                 DMEMIT("%d %llu", sc->stripes,
-                        (unsigned long long)sc->chunk_mask + 1);
+                        (unsigned long long)sc->chunk_size);
                 for (i = 0; i < sc->stripes; i++)
                         DMEMIT(" %s %llu", sc->stripe[i].dev->name,
                             (unsigned long long)sc->stripe[i].physical_start);
@@ -387,7 +381,7 @@ static void stripe_io_hints(struct dm_target *ti,
                             struct queue_limits *limits)
 {
         struct stripe_c *sc = ti->private;
-        unsigned chunk_size = (sc->chunk_mask + 1) << 9;
+        unsigned chunk_size = sc->chunk_size << SECTOR_SHIFT;
 
         blk_limits_io_min(limits, chunk_size);
         blk_limits_io_opt(limits, chunk_size * sc->stripes);
@@ -415,7 +409,7 @@ static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 
 static struct target_type stripe_target = {
         .name   = "striped",
-        .version = {1, 4, 0},
+        .version = {1, 5, 0},
         .module = THIS_MODULE,
         .ctr    = stripe_ctr,
         .dtr    = stripe_dtr,