md/raid5: allow for more than 2^31 chunks.

With many large drives and small chunk sizes it is possible
to create a RAID5 with more than 2^31 chunks.  Make sure this
works.

Reported-by: Brett King <king.br@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Cc: stable@kernel.org

1 files changed, 7 insertions, 12 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e3e9a36ea3b..20e48401910 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1650,8 +1650,8 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector,
                                      int previous, int *dd_idx,
                                      struct stripe_head *sh)
 {
-        long stripe;
-        unsigned long chunk_number;
+        sector_t stripe;
+        sector_t chunk_number;
         unsigned int chunk_offset;
         int pd_idx, qd_idx;
         int ddf_layout = 0;
@@ -1671,17 +1671,12 @@ static sector_t raid5_compute_sector(raid5_conf_t *conf, sector_t r_sector,
          */
         chunk_offset = sector_div(r_sector, sectors_per_chunk);
         chunk_number = r_sector;
-        BUG_ON(r_sector != chunk_number);
 
         /*
          * Compute the stripe number
          */
-        stripe = chunk_number / data_disks;
-
-        /*
-         * Compute the data disk and parity disk indexes inside the stripe
-         */
-        *dd_idx = chunk_number % data_disks;
+        stripe = chunk_number;
+        *dd_idx = sector_div(stripe, data_disks);
 
         /*
          * Select the parity disk based on the user selected algorithm.
@@ -1870,14 +1865,14 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous)
                                  : conf->algorithm;
         sector_t stripe;
         int chunk_offset;
-        int chunk_number, dummy1, dd_idx = i;
+        sector_t chunk_number;
+        int dummy1, dd_idx = i;
         sector_t r_sector;
         struct stripe_head sh2;
 
 
         chunk_offset = sector_div(new_sector, sectors_per_chunk);
         stripe = new_sector;
-        BUG_ON(new_sector != stripe);
 
         if (i == sh->pd_idx)
                 return 0;
@@ -1970,7 +1965,7 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous)
         }
 
         chunk_number = stripe * data_disks + i;
-        r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
+        r_sector = chunk_number * sectors_per_chunk + chunk_offset;
 
         check = raid5_compute_sector(conf, r_sector,
                                      previous, &dummy1, &sh2);