btrfs: fix percent calculation for bg reclaim message

We have a report, that the info message for block-group reclaim is
crossing the 100% used mark.

This is happening as we were truncating the divisor for the division
(the block_group->length) to a 32bit value.

Fix this by using div64_u64() to not truncate the divisor.

In the worst case, it can lead to a div by zero error and should be
possible to trigger on 4 disks RAID0, and each device is large enough:

  $ mkfs.btrfs  -f /dev/test/scratch[1234] -m raid1 -d raid0
  btrfs-progs v6.1
  [...]
  Filesystem size:    40.00GiB
  Block group profiles:
    Data:             RAID0             4.00GiB <<<
    Metadata:         RAID1           256.00MiB
    System:           RAID1             8.00MiB

Reported-by: Forza <[email protected]>
Link: https://lore.kernel.org/linux-btrfs/[email protected]/
Fixes: 5f93e776c673 ("btrfs: zoned: print unusable percentage when reclaiming block groups")
CC: [email protected] # 5.15+
Reviewed-by: Anand Jain <[email protected]>
Reviewed-by: Qu Wenruo <[email protected]>
Signed-off-by: Johannes Thumshirn <[email protected]>
Reviewed-by: David Sterba <[email protected]>
[ add Qu's note ]
Signed-off-by: David Sterba <[email protected]>

0 files changed, 0 insertions, 0 deletions