Re: [libvirt PATCH 12/17] util: Try to get limits from /proc

On Mon, 2021-03-08 at 10:50 +0000, Daniel P. Berrangé wrote: > On Fri, Mar 05, 2021 at 08:13:59PM +0100, Andrea Bolognani wrote: > > + if (!(label = virProcessLimitResourceToLabel(resource))) { > > + virReportError(VIR_ERR_INTERNAL_ERROR, > > + _("Unknown resource %d requested for process %lld"), > > + resource, (long long)pid); > > + return -1; > > Setting errors on -1 This is only hit if virProcessGetLimitFromProc() has been asked to obtain limits for a resource it doesn't know how to fetch, which indicates a bug in libvirt and is thus reported as internal error.

> > + procfile = g_strdup_printf("/proc/%lld/limits", (long long)pid); > > + > > + if (!g_file_get_contents(procfile, &buf, &len, NULL)) > > + return -1; > > Not setting errors on -1 This is simply "file couldn't be read", which would be the case on FreeBSD for example.

> > + /* For whatever reason, using prlimit() on another process - even > > + * when it's just to obtain the current limit rather than changing > > + * it - requires CAP_SYS_RESOURCE, which we might not have in a > > + * containerized environment; on the other hand, no particular > > + * permission is needed to poke around /proc, so try that if going > > + * through the syscall didn't work */ > > + if (virProcessGetLimitFromProc(pid, resource, old_limit) == 0) > > + return 0; > > This ought to be conditional for Linux only and error reporting needs > to be made consistent. The intent above was to have this fail quietly on non-Linux without adding checks for it, but sure I can have an actual stub on other platforms instead. -- Andrea Bolognani / Red Hat / Virtualization