f2fs: choose hardlimit when softlimit is larger than hardlimit in f2fs_statfs_project()

f2fs: choose hardlimit when softlimit is larger than hardlimit in f2fs_statfs_project()

Setting softlimit larger than hardlimit seems meaningless
for disk quota but currently it is allowed. In this case,
there may be a bit of comfusion for users when they run
df comamnd to directory which has project quota.

For example, we set 20M softlimit and 10M hardlimit of
block usage limit for project quota of test_dir(project id 123).

[root@hades f2fs]# repquota -P -a
*** Report for project quotas on device /dev/nvme0n1p8
Block grace time: 7days; Inode grace time: 7days
Block limits File limits
Project used soft hard grace used soft hard grace
----------------------------------------------------------------------
0 -- 4 0 0 1 0 0
123 +- 10248 20480 10240 2 0 0

The result of df command as below:

[root@hades f2fs]# df -h /mnt/f2fs/test
Filesystem Size Used Avail Use% Mounted on
/dev/nvme0n1p8 20M 11M 10M 51% /mnt/f2fs

Even though it looks like there is another 10M free space to use,
if we write new data to diretory test(inherit project id),
the write will fail with errno(-EDQUOT).

After this patch, the df result looks like below.

[root@hades f2fs]# df -h /mnt/f2fs/test
Filesystem Size Used Avail Use% Mounted on
/dev/nvme0n1p8 10M 10M 0 100% /mnt/f2fs

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>