Ceph » CephFS

first, set the maxbytes quota for a directory in cephfs,for example the directory named test and the quota is 10G;

then mount the cephfs : ceph-fuse -n client.admin /mnt/cephfs -r /test;

then write some test data :dd if=/dev/zero of=/mnt/cephfs/file bs=1M count=20000;

check the "df -h" command output:
Filesystem Size Used Avail Use% Mounted on
ceph-fuse 10G -64Y -6.0G 100% /mnt/cephfs

use the "strace df" , a syscall shows :
statfs64("/mnt/cephfs", {f_type=0x65735546, f_bsize=4194304, f_blocks=2560, f_bfree=18446744073709550080, f_bavail=18446744073709550080, f_fsid={0, 0}, f_namelen=255, f_frsize=4194304}) = 0

obviously f_bfree is wrong, and its value is 2^64, 64Y is 2^86

This bug was found on ceph-10.2.7, but 12.0.2 has this problem too.