/// <summary>Find the cgroup path for the specified subsystem.</summary>
/// <param name="subsystem">The subsystem, e.g. "memory".</param>
/// <returns>The cgroup path if found; otherwise, null.</returns>
private static string FindCGroupPath(string subsystem, out CGroupVersion version)
{
if (TryFindHierarchyMount(subsystem, out version, out string hierarchyRoot, out string hierarchyMount) &&
TryFindCGroupPathForSubsystem(subsystem, out string cgroupPathRelativeToMount))
{
// For a host cgroup, we need to append the relative path.
// In a docker container, the root and relative path are the same and we don't need to append.
return((hierarchyRoot != cgroupPathRelativeToMount) ?
hierarchyMount + cgroupPathRelativeToMount :
hierarchyMount);
}
return(null);
}
internal static bool TryFindHierarchyMount(string mountInfoFilePath, string subsystem, out CGroupVersion version, out string root, out string path)
{
if (File.Exists(mountInfoFilePath))
{
try
{
using (var reader = new StreamReader(mountInfoFilePath))
{
string line;
while ((line = reader.ReadLine()) != null)
{
// Look for an entry that has cgroup as the "filesystem type"
// and, for cgroup1, that has options containing the specified subsystem
// See man page for /proc/[pid]/mountinfo for details, e.g.:
// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
// but (7) is optional and could exist as multiple fields; the (8) separator marks
// the end of the optional values.
const string Separator = " - ";
int endOfOptionalFields = line.IndexOf(Separator);
if (endOfOptionalFields == -1)
{
// Malformed line.
continue;
}
string postSeparatorLine = line.Substring(endOfOptionalFields + Separator.Length);
string[] postSeparatorlineParts = postSeparatorLine.Split(' ');
if (postSeparatorlineParts.Length < 3)
{
// Malformed line.
continue;
}
bool validCGroup1Entry = ((postSeparatorlineParts[0] == "cgroup") &&
(Array.IndexOf(postSeparatorlineParts[2].Split(','), subsystem) >= 0));
bool validCGroup2Entry = postSeparatorlineParts[0] == "cgroup2";
if (!validCGroup1Entry && !validCGroup2Entry)
{
// Not the relevant entry.
continue;
}
// Found the relevant entry. Extract the cgroup version, mount root and path.
switch (postSeparatorlineParts[0])
{
case "cgroup":
version = CGroupVersion.CGroup1;
break;
case "cgroup2":
version = CGroupVersion.CGroup2;
break;
default:
version = CGroupVersion.None;
Debug.Fail($"invalid value for CGroupVersion \"{postSeparatorlineParts[0]}\"");
break;
}
string[] lineParts = line.Substring(0, endOfOptionalFields).Split(' ');
root = lineParts[3];
path = lineParts[4];
return(true);
}
}
}
catch (Exception e)
{
Debug.Fail($"Failed to read or parse \"{ProcMountInfoFilePath}\": {e}");
}
}
version = CGroupVersion.None;
root = null;
path = null;
return(false);
}
/// <summary>Find the cgroup mount information for the specified subsystem.</summary>
/// <param name="subsystem">The subsystem, e.g. "memory".</param>
/// <param name="root">The path of the directory in the filesystem which forms the root of this mount; null if not found.</param>
/// <param name="path">The path of the mount point relative to the process's root directory; null if not found.</param>
/// <returns>true if the mount was found; otherwise, null.</returns>
private static bool TryFindHierarchyMount(string subsystem, out CGroupVersion version, out string root, out string path)
{
return(TryFindHierarchyMount(ProcMountInfoFilePath, subsystem, out version, out root, out path));
}
private static bool TryFindHierarchyMount(string subsystem, out CGroupVersion version, [NotNullWhen(true)] out string?root, [NotNullWhen(true)] out string?path)
{
return(TryFindHierarchyMount(ProcMountInfoFilePath, subsystem, out version, out root, out path));
}
