It looks like some xfs filesystems on ms-be104[0123] are reporting negative usage:
/dev/sda3 94G 30G 64G 32% /srv/swift-storage/sda3 /dev/sda4 297G 340M 297G 1% /srv/swift-storage/sda4 /dev/sdb4 297G 340M 297G 1% /srv/swift-storage/sdb4 /dev/sdl1 3.7T -13T 17T - /srv/swift-storage/sdl1 /dev/sdj1 3.7T -13T 17T - /srv/swift-storage/sdj1 /dev/sdi1 3.7T -29T 33T - /srv/swift-storage/sdi1 /dev/sdb3 94G 35G 59G 38% /srv/swift-storage/sdb3 /dev/sdn1 3.7T -14T 17T - /srv/swift-storage/sdn1 /dev/sdh1 3.7T -13T 17T - /srv/swift-storage/sdh1 /dev/sdc1 3.7T 3.0T 674G 82% /srv/swift-storage/sdc1 /dev/sdk1 3.7T 3.1T 643G 83% /srv/swift-storage/sdk1 /dev/sdm1 3.7T 3.1T 632G 84% /srv/swift-storage/sdm1 /dev/sdf1 3.7T 3.1T 612G 84% /srv/swift-storage/sdf1 /dev/sdg1 3.7T 3.1T 623G 84% /srv/swift-storage/sdg1 /dev/sdd1 3.7T 3.1T 641G 83% /srv/swift-storage/sdd1 tmpfs 13G 0 13G 0% /run/user/4849 /dev/sde1 3.7T -13T 17T - /srv/swift-storage/sde1
These hosts are part of the last batch of additions to eqiad, their counterparts in codfw don't seem to be affected.
Looking at e.g. ms-be1040 it seems the issue started in may around different times for different filesystems: