qmeventd: improve getting VMID from PID in presence of legacy cgroup entries

On a hybrid cgroup system, the /proc/<PID>/cgroup file looks like

> 13:pids:/qemu.slice/110.scope
> 12:perf_event:/
> 11:devices:/qemu.slice
> 10:misc:/
> 9:hugetlb:/
> 8:freezer:/
> 7:cpu,cpuacct:/qemu.slice/110.scope
> 6:memory:/qemu.slice/110.scope
> 5:rdma:/
> 4:cpuset:/
> 3:blkio:/qemu.slice
> 2:net_cls,net_prio:/
> 1:name=systemd:/qemu.slice/110.scope
> 0::/qemu.slice/110.scope

but the order doesn't seem to be deterministic, so it can happen that
an entry like '11:devices:/qemu.slice' is the first to match the
'/qemu.slice' part, which previously made the code expect to find the
VMID.

To improve detection, as a first step, match the trailing slash too.

Reported in the community forum:
https://forum.proxmox.com/threads/129320/post-571654

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

diff --git a/qmeventd/qmeventd.c b/qmeventd/qmeventd.c
index 921c0dca1607b5e9d974a039516c555ac26e7c8a..503bce6901cf4ba467ccb516f0ff3d56dabc5a4e 100644 (file)
--- a/qmeventd/qmeventd.c
+++ b/qmeventd/qmeventd.c
@@ -109,7 +109,7 @@ get_vmid_from_pid(pid_t pid)
        }
        cgroup_path++;
 
-       if (strncmp(cgroup_path, "/qemu.slice", 11)) {
+       if (strncmp(cgroup_path, "/qemu.slice/", 12)) {
            continue;
        }
 
@@ -142,7 +142,7 @@ get_vmid_from_pid(pid_t pid)
     if (errno) {
        fprintf(stderr, "error parsing vmid for %d: %s\n", pid, strerror(errno));
     } else {
-       fprintf(stderr, "error parsing vmid for %d: no qemu.slice cgroup entry\n", pid);
+       fprintf(stderr, "error parsing vmid for %d: no matching qemu.slice cgroup entry\n", pid);
     }
 
 ret: