maxpct option for small xfs filesystems

[Alexander Tsvetkov]

Hello,

I'm trying to understand the expected behaviour of "maxpct" option in 
case of small xfs filesystem
comparing the maximum percentage defined for this option with the 
percentage of actually allocated
inodes in filesystem, but the result of prepared test case doesn't 
correspond to the expectations:

[root at fedora ~]#mkfs.xfs -f -d size=16m -i maxpct=1 /dev/sdb2
[root at fedora ~]# mount /dev/sdb2 /mnt/scratch/
[root at fedora ~]# mount | grep scratch
/dev/sdb2 on /mnt/scratch type xfs 
(rw,relatime,seclabel,attr2,inode64,noquota)
[root at fedora ~]# xfs_info /mnt/scratch/
meta-data=/dev/sdb2        isize=256    agcount=1, agsize=4096 blks
                  =                       sectsz=512   attr=2, projid32bit=1
                  =                       crc=0        finobt=0
data          =                       bsize=4096   blocks=4096, imaxpct=1
                  =                       sunit=0      swidth=0 blks
naming     =version 2        bsize=4096   ascii-ci=0 ftype=0
log            =internal           bsize=4096   blocks=853, version=2
                  =                       sectsz=512   sunit=0 blks, 
lazy-count=1
realtime    =none               extsz=4096   blocks=0, rtextents=0

then trying to fill filesystem with lot of empty files until enospc 
obtained and break the loop:

[root at fedora ~]# for i in {0..100000}; do str=$(mktemp 
--tmpdir=/mnt/scratch tmp.XXXXXXXXXX); echo $str; done

filesystem is full with created files:

[root at fedora ~]# df -Th | grep scratch
/dev/sdb2      xfs        13M   13M  148K  99% /mnt/scratch

and from the number of actually created inodes:

[root at fedora ~]# xfs_db -c "blockget -n" -c "ncheck" /dev/sdb2 | wc -l
40512

it's calculated the space allocated for file inodes 9.9Mb (40512*256b 
inode size) that is about 77% of filesystem
space instead of defined maximum with maxpct=1% or even default 25% value.

Thanks,
Alexander Tsvetkov