getSourceMount(): simplify
The flow of getSourceMount was:
1 get all entries from /proc/self/mountinfo
2 do a linear search for the `source` directory
3 if found, return its data
4 get the parent directory of `source`, goto 2
The repeated linear search through the whole mountinfo (which can have
thousands of records) is inefficient. Instead, let's just
1 collect all the relevant records (only those mount points
that can be a parent of `source`)
2 find the record with the longest mountpath, return its data
This was tested manually with something like
```go
func TestGetSourceMount(t *testing.T) {
mnt, flags, err := getSourceMount("/sys/devices/msr/")
assert.NoError(t, err)
t.Logf("mnt: %v, flags: %v", mnt, flags)
}
```
...but it relies on having a specific mount points on the system
being used for testing.
[v2: add unit tests for ParentsFilter]
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Kir Kolyshkin authored on 2018/01/26 13:13:46Showing 3 changed files
| ... | ... |
@@ -380,15 +380,6 @@ func specMapping(s []idtools.IDMap) []specs.LinuxIDMapping {
|
| 380 | 380 |
return ids |
| 381 | 381 |
} |
| 382 | 382 |
|
| 383 |
-func getMountInfo(mountinfo []*mount.Info, dir string) *mount.Info {
|
|
| 384 |
- for _, m := range mountinfo {
|
|
| 385 |
- if m.Mountpoint == dir {
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- return m |
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- } |
|
| 388 |
- } |
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- return nil |
|
| 390 |
-} |
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- |
|
| 392 | 383 |
// Get the source mount point of directory passed in as argument. Also return |
| 393 | 384 |
// optional fields. |
| 394 | 385 |
func getSourceMount(source string) (string, string, error) {
|
| ... | ... |
@@ -398,29 +389,26 @@ func getSourceMount(source string) (string, string, error) {
|
| 398 | 398 |
return "", "", err |
| 399 | 399 |
} |
| 400 | 400 |
|
| 401 |
- mountinfos, err := mount.GetMounts(nil) |
|
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+ mi, err := mount.GetMounts(mount.ParentsFilter(sourcePath)) |
|
| 402 | 402 |
if err != nil {
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| 403 | 403 |
return "", "", err |
| 404 | 404 |
} |
| 405 |
- |
|
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- mountinfo := getMountInfo(mountinfos, sourcePath) |
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- if mountinfo != nil {
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- return sourcePath, mountinfo.Optional, nil |
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+ if len(mi) < 1 {
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+ return "", "", fmt.Errorf("Can't find mount point of %s", source)
|
|
| 409 | 407 |
} |
| 410 | 408 |
|
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- path := sourcePath |
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- for {
|
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- path = filepath.Dir(path) |
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- |
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- mountinfo = getMountInfo(mountinfos, path) |
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- if mountinfo != nil {
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- return path, mountinfo.Optional, nil |
|
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- } |
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- |
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- if path == "/" {
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- break |
|
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+ // find the longest mount point |
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+ var idx, maxlen int |
|
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+ for i := range mi {
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+ if len(mi[i].Mountpoint) > maxlen {
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+ maxlen = len(mi[i].Mountpoint) |
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+ idx = i |
|
| 422 | 415 |
} |
| 423 | 416 |
} |
| 417 |
+ // and return it unless it's "/" |
|
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+ if mi[idx].Mountpoint != "/" {
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+ return mi[idx].Mountpoint, mi[idx].Optional, nil |
|
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+ } |
|
| 424 | 421 |
|
| 425 | 422 |
// If we are here, we did not find parent mount. Something is wrong. |
| 426 | 423 |
return "", "", fmt.Errorf("Could not find source mount of %s", source)
|
| ... | ... |
@@ -36,6 +36,17 @@ func SingleEntryFilter(mp string) FilterFunc {
|
| 36 | 36 |
} |
| 37 | 37 |
} |
| 38 | 38 |
|
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+// ParentsFilter returns all entries whose mount points |
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+// can be parents of a path specified, discarding others. |
|
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+// For example, given `/var/lib/docker/something`, entries |
|
| 42 |
+// like `/var/lib/docker`, `/var` and `/` are returned. |
|
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+func ParentsFilter(path string) FilterFunc {
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+ return func(m *Info) (bool, bool) {
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+ skip := !strings.HasPrefix(path, m.Mountpoint) |
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+ return skip, false |
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+ } |
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+} |
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+ |
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| 39 | 50 |
// GetMounts retrieves a list of mounts for the current running process, |
| 40 | 51 |
// with an optional filter applied (use nil for no filter). |
| 41 | 52 |
func GetMounts(f FilterFunc) ([]*Info, error) {
|
| ... | ... |
@@ -499,4 +499,10 @@ func TestParseMountinfoFilters(t *testing.T) {
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| 499 | 499 |
infos, err = parseInfoFile(r, PrefixFilter("nonexistent"))
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| 500 | 500 |
assert.NilError(t, err) |
| 501 | 501 |
assert.Equal(t, 0, len(infos)) |
| 502 |
+ |
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+ r.Reset([]byte(fedoraMountinfo)) |
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+ infos, err = parseInfoFile(r, ParentsFilter("/sys/fs/cgroup/cpu,cpuacct"))
|
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+ assert.NilError(t, err) |
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+ // there should be 4 results returned: /sys/fs/cgroup/cpu,cpuacct /sys/fs/cgroup /sys / |
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+ assert.Equal(t, 4, len(infos)) |
|
| 502 | 508 |
} |