md: Avoid OOPS when reshaping raid1 to raid0

raid1 arrays do not have the notion of chunk size. Calculate the
largest chunk sector size we can use to avoid a divide by zero OOPS
when aligning the size of the new array to the chunk size.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 17 insertions, 1 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index c9809453a346..de63a1fc3737 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -632,6 +632,7 @@ static void *raid0_takeover_raid10(struct mddev *mddev)
 static void *raid0_takeover_raid1(struct mddev *mddev)
 {
         struct r0conf *priv_conf;
+        int chunksect;
 
         /* Check layout:
          *  - (N - 1) mirror drives must be already faulty
@@ -642,10 +643,25 @@ static void *raid0_takeover_raid1(struct mddev *mddev)
                 return ERR_PTR(-EINVAL);
         }
 
+        /*
+         * a raid1 doesn't have the notion of chunk size, so
+         * figure out the largest suitable size we can use.
+         */
+        chunksect = 64 * 2; /* 64K by default */
+
+        /* The array must be an exact multiple of chunksize */
+        while (chunksect && (mddev->array_sectors & (chunksect - 1)))
+                chunksect >>= 1;
+
+        if ((chunksect << 9) < PAGE_SIZE)
+                /* array size does not allow a suitable chunk size */
+                return ERR_PTR(-EINVAL);
+
         /* Set new parameters */
         mddev->new_level = 0;
         mddev->new_layout = 0;
-        mddev->new_chunk_sectors = 128; /* by default set chunk size to 64k */
+        mddev->new_chunk_sectors = chunksect;
+        mddev->chunk_sectors = chunksect;
         mddev->delta_disks = 1 - mddev->raid_disks;
         mddev->raid_disks = 1;
         /* make sure it will be not marked as dirty */