minio/pkg/disk/stat_linux.go
Tamer Fahmy 0bf981278e Provide the correct free block size volume/disk information (#4943)
On *NIX platforms the statfs(2) system call returns a struct containing both the
free blocks in the filesystem (Statfs_t.Bfree) and the free blocks available to
the unprivileged or non-superuser (Statfs_t.Bavail).

The `Bfree` and `Bavail` fields (with `Bfree >= Bavail`) will be set to
different values on e.g. filesystems such as ext4 that reserve a certain
percentage of the filesystem blocks which may only be allocated by admnistrative
privileged processes.

The calculations for the `Total` disk space need to subtract the difference
between the `Bfree` and `Bavail` fields for it to correctly show the total
available storage space available for unprivileged users.

This implicitly fixes a bug where the `Used = Total - Free` calculation yielded
different (and also incorrect) results for identical contents stored when only
the sizes of the disks or backing volumes differed. (as can be witnessed in the
`Used:` value displayed in the Minio browser)

See:
- https://wiki.archlinux.org/index.php/ext4#Reserved_blocks
- http://man7.org/linux/man-pages/man2/statfs.2.html
- https://man.openbsd.org/statfs
- http://lingrok.org/xref/coreutils/src/df.c#893
2017-09-25 18:46:19 -07:00

42 lines
1.2 KiB
Go

// +build linux
/*
* Minio Cloud Storage, (C) 2015, 2016, 2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package disk
import (
"syscall"
)
// GetInfo returns total and free bytes available in a directory, e.g. `/`.
func GetInfo(path string) (info Info, err error) {
s := syscall.Statfs_t{}
err = syscall.Statfs(path, &s)
if err != nil {
return Info{}, err
}
fsReservedBlocks := uint64(s.Bfree) - uint64(s.Bavail)
info = Info{
Total: uint64(s.Bsize) * (uint64(s.Blocks) - fsReservedBlocks),
Free: uint64(s.Bsize) * uint64(s.Bavail),
Files: uint64(s.Files),
Ffree: uint64(s.Ffree),
FSType: getFSType(int64(s.Type)),
}
return info, nil
}