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btrfs: fix percent calculation for bg reclaim message

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commit 95cd356ca23c3807b5f3503687161e216b1c520d upstream.

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 <forza@tnonline.net>
Link: https://lore.kernel.org/linux-btrfs/e99483.c11a58d.1863591ca52@tnonline.net/
Fixes: 5f93e776c673 ("btrfs: zoned: print unusable percentage when reclaiming block groups")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add Qu's note ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johannes Thumshirn 2023-02-21 10:11:24 -08:00 committed by Greg Kroah-Hartman
parent f8cd8754a0
commit 2072e75b49
1 changed files with 2 additions and 1 deletions
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3
fs/btrfs/block-group.c
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@ -1554,7 +1554,8 @@ void btrfs_reclaim_bgs_work(struct work_struct *work)
btrfs_info(fs_info,
"reclaiming chunk %llu with %llu%% used %llu%% unusable",
bg->start, div_u64(bg->used * 100, bg->length),
bg->start,
div64_u64(bg->used * 100, bg->length),
div64_u64(zone_unusable * 100, bg->length));
trace_btrfs_reclaim_block_group(bg);
ret = btrfs_relocate_chunk(fs_info, bg->start);