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    SubjectRe: [PATCH 5/5] hugetlbfs: fix confusing hugetlbfs stat
    On 07/22/22 14:38, Miaohe Lin wrote:
    > On 2022/7/22 8:28, Mike Kravetz wrote:
    > > On 07/21/22 21:16, Miaohe Lin wrote:
    > >> When size option is not specified, f_blocks, f_bavail and f_bfree will be
    > >> set to -1 instead of 0. Likewise, when nr_inodes is not specified, f_files
    > >> and f_ffree will be set to -1 too. Check max_hpages and max_inodes against
    > >> -1 first to make sure 0 is reported for max/free/used when no limit is set
    > >> as the comment states.
    > >
    > > Just curious, where are you seeing values reported as -1? The check
    >
    > From the standard statvfs() function.
    >
    > > for sbinfo->spool was supposed to handle these cases. Seems like it
    >
    > sbinfo->spool could be created when ctx->max_hpages == -1 while
    > ctx->min_hpages != -1 in hugetlbfs_fill_super.
    >
    > > should handle the max_hpages == -1 case. But, it doesn't look like it
    > > considers the max_inodes == -1 case.
    > >
    > > If I create/mount a hugetlb filesystem without specifying size or nr_inodes,
    > > df seems to report zero instead of -1.
    > >
    > > Just want to understand the reasoning behind the change.

    Thanks for the additional information (and test program)!

    From the hugetlbfs documentation:
    "If the ``size``, ``min_size`` or ``nr_inodes`` option is not provided on
    command line then no limits are set."

    So, having those values set to -1 indicates there is no limit set.

    With this change, 0 is reported for the case where there is no limit set as
    well as the case where the max value is 0.

    There may be some value in reporting -1 as is done today.

    To be honest, I am not sure what is the correct behavior here. Unless
    there is a user visible issue/problem, I am hesitant to change. Other
    opinions are welcome.
    --
    Mike Kravetz

    >
    > I wrote a test program:
    >
    > #include <sys/statvfs.h>
    > #include <stdio.h>
    >
    > int main(void)
    > {
    > struct statvfs buf;
    >
    > if (statvfs("/root/huge/", &buf) == -1) {
    > printf("statvfs() error\n");
    > return -1;
    > }
    > printf("f_blocks %lld, f_bavail %lld, f_bfree %lld, f_files %lld, f_ffree %lld\n",
    > buf.f_blocks, buf.f_bavail, buf.f_bfree, buf.f_files, buf.f_ffree);
    > return 0;
    > }
    >
    > And test it in my env:
    > [root@localhost ~]# mount -t hugetlbfs none /root/huge/
    > [root@localhost ~]# ./stat
    > f_blocks 0, f_bavail 0, f_bfree 0, f_files 0, f_ffree 0
    > [root@localhost ~]# umount /root/huge/
    > [root@localhost ~]# mount -t hugetlbfs -o min_size=32M none /root/huge/
    > [root@localhost ~]# ./stat
    > f_blocks -1, f_bavail -1, f_bfree -1, f_files -1, f_ffree -1
    > [root@localhost ~]# umount /root/huge/
    > [root@localhost ~]# mount -t hugetlbfs -o min_size=32M,size=64M none /root/huge/
    > [root@localhost ~]# ./stat
    > f_blocks 32, f_bavail 32, f_bfree 32, f_files -1, f_ffree -1
    > [root@localhost ~]# umount /root/huge/
    > [root@localhost ~]# mount -t hugetlbfs -o min_size=32M,size=64M,nr_inodes=1024 none /root/huge/
    > [root@localhost ~]# ./stat
    > f_blocks 32, f_bavail 32, f_bfree 32, f_files 1024, f_ffree 1023
    > [root@localhost ~]# umount /root/huge/
    >
    > Or am I miss something?
    >
    > >
    >
    > Thanks.

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