Btrfs: make sure the chunk allocator doesn't create zero length chunks

A recent commit allowed for smaller chunks to be created, but didn't
make sure they were always bigger than a stripe.  After some divides,
this led to zero length stripes.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9bf1f581b872..b584e9a2add2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2249,6 +2249,12 @@ again:
         if (!looped)
                 calc_size = max_t(u64, min_stripe_size, calc_size);
 
+        /*
+         * we're about to do_div by the stripe_len so lets make sure
+         * we end up with something bigger than a stripe
+         */
+        calc_size = max_t(u64, calc_size, stripe_len * 4);
+
         do_div(calc_size, stripe_len);
         calc_size *= stripe_len;