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util: support systems using the new cgroup v2 structure #3091

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May 7, 2022
Merged

util: support systems using the new cgroup v2 structure #3091

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26 changes: 18 additions & 8 deletions internal/util/pidlimit.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,32 +27,44 @@ import (
)

const (
procCgroup = "/proc/self/cgroup"
sysPidsMaxFmt = "/sys/fs/cgroup/pids%s/pids.max"
procCgroup = "/proc/self/cgroup"
sysPidsMaxFmtCgroupV1 = "/sys/fs/cgroup/pids%s/pids.max"
sysPidsMaxFmtCgroupV2 = "/sys/fs/cgroup%s/pids.max"
)

// return the cgouprs "pids.max" file of the current process
//
// find the line containing the pids group from the /proc/self/cgroup file
// $ grep 'pids' /proc/self/cgroup
// getCgroupPidsFile return the cgroups "pids.max" file of the
// current process
// For cgroup v1, find the line containing the pids group from the /proc/self/cgroup file
// $ grep ':pids:' /proc/self/cgroup
// 7:pids:/kubepods.slice/kubepods-besteffort.slice/....scope
// $ cat /sys/fs/cgroup/pids + *.scope + /pids.max.
// The entry for cgroup v2 is always in the format "0::...scope", no subsystem given.
// (see https://www.kernel.org/doc/Documentation/cgroup-v2.txt)
func getCgroupPidsFile() (string, error) {
cgroup, err := os.Open(procCgroup)
if err != nil {
return "", err
}
defer cgroup.Close() // #nosec: error on close is not critical here

pidsMax := ""
scanner := bufio.NewScanner(cgroup)
var slice string
for scanner.Scan() {
parts := strings.SplitN(scanner.Text(), ":", 3)
if parts == nil || len(parts) < 3 {
continue
}
// No cgroup subsystem given, then it is cgroupv2
if parts[0] == "0" && parts[1] == "" {
slice = parts[2]
pidsMax = fmt.Sprintf(sysPidsMaxFmtCgroupV2, slice)

break
}
if parts[1] == "pids" {
slice = parts[2]
pidsMax = fmt.Sprintf(sysPidsMaxFmtCgroupV1, slice)

break
}
Expand All @@ -61,8 +73,6 @@ func getCgroupPidsFile() (string, error) {
return "", fmt.Errorf("could not find a cgroup for 'pids'")
}

pidsMax := fmt.Sprintf(sysPidsMaxFmt, slice)

return pidsMax, nil
}

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