Commit 3fed40cc ("Btrfs: cleanup duplicated division functions"), which
was merged into 3.8-rc1, has introduced a regression by removing logic
that was guarding us against bad user input.  Bring it back.

Signed-off-by: Ilya Dryomov <idryo...@gmail.com>
---
 fs/btrfs/volumes.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 86279c3..b577aee 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2614,7 +2614,14 @@ static int chunk_usage_filter(struct btrfs_fs_info 
*fs_info, u64 chunk_offset,
        cache = btrfs_lookup_block_group(fs_info, chunk_offset);
        chunk_used = btrfs_block_group_used(&cache->item);
 
-       user_thresh = div_factor_fine(cache->key.offset, bargs->usage);
+       if (bargs->usage == 0)
+               user_thresh = 0;
+       else if (bargs->usage > 100)
+               user_thresh = cache->key.offset;
+       else
+               user_thresh = div_factor_fine(cache->key.offset,
+                                             bargs->usage);
+
        if (chunk_used < user_thresh)
                ret = 0;
 
-- 
1.7.9.1

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