Btrfs: fix max chunk size check in chunk allocator

Fix a bug, where in case we need to adjust stripe_size so that the
length of the resulting chunk is less than or equal to max_chunk_size,
DUP chunks turn out to be only half as big as they could be.

Cc: Arne Jansen <sensille@gmx.net>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 759d02486d7c..ce289af526f0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3324,12 +3324,14 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
         stripe_size = devices_info[ndevs-1].max_avail;
         num_stripes = ndevs * dev_stripes;
 
-        if (stripe_size * num_stripes > max_chunk_size * ncopies) {
+        if (stripe_size * ndevs > max_chunk_size * ncopies) {
                 stripe_size = max_chunk_size * ncopies;
-                do_div(stripe_size, num_stripes);
+                do_div(stripe_size, ndevs);
         }
 
         do_div(stripe_size, dev_stripes);
+
+        /* align to BTRFS_STRIPE_LEN */
         do_div(stripe_size, BTRFS_STRIPE_LEN);
         stripe_size *= BTRFS_STRIPE_LEN;