Non power of 2 chunksize support is needed to properly align stripe IO

on storage that has non power of 2 optimal IO sizes (e.g. RAID6 10+2).

Use sector_div to support non power of 2 chunksize for the pool's
data device.  sector_div provides comparable performance to the power of 2
math that was performed until now (as tested on modern x86_64 hardware).

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>

diff --git a/Documentation/device-mapper/striped.txt b/Documentation/device-mapper/striped.txt
index 953fe1d68068fd5b94ee1143f0969102d96be809..45f3b91ea4c3259ba19388b40935d60f276ff6ec 100644 (file)
--- a/Documentation/device-mapper/striped.txt
+++ b/Documentation/device-mapper/striped.txt
@@ -9,8 +9,8 @@ devices in parallel.
 
 Parameters: <num devs> <chunk size> [<dev path> <offset>]+
     <num devs>: Number of underlying devices.
-    <chunk size>: Size of each chunk of data. Must be a power-of-2 and at
-                  least as large as the system's PAGE_SIZE.
+    <chunk size>: Size of each chunk of data. Must be at least as
+                  large as the system's PAGE_SIZE.
     <dev path>: Full pathname to the underlying block-device, or a
                 "major:minor" device-number.
     <offset>: Starting sector within the device.

diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index 992c9d4c3bd93f42d8b95f19919939f293cb2ede..9690daa11c83526bd7cdc8376cac7d2b7398b1ef 100644 (file)
--- 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,