Re: [PATCH v2 02/11] qemu: Drop two layers of nesting of memoryBackingDir

On 30. 3. 2020 13:09, Daniel P. Berrangé wrote: > On Thu, Mar 26, 2020 at 04:15:06PM +0100, Michal Privoznik wrote: >> Initially introduced in v3.10.0-rc1~172. >> >> When generating a path for memory-backend-file or -mem-path, qemu >> driver will use the following pattern: >> >> $memoryBackingDir/libvirt/qemu/$id-$shortName >> >> where $memoryBackingDir defaults to /var/lib/libvirt/qemu/ram but >> can be overridden in qemu.conf. Anyway, the "/libvirt/qemu/" part >> looks redundant, because it's already contained in the default, >> or creates unnecessary nesting if overridden in qemu.conf. > > I think this was copied from our earlier huge pages code > which used /dev/hugepages, and then added "/libvirt/qemu" > to it. > > Now we're stripping off "/libvirt/qemu" though, we're liable > to a filename clashes if someone edits qemu.conf to point to > /dev/shm. > > IOW, even though "/libvirt/qemu" is redundant when using our > default path, I think we need to keep it to avoid clashing > with custom paths. Alright. So what if I'd squash this in? diff --git i/src/qemu/qemu_conf.c w/src/qemu/qemu_conf.c index 9786e19f8f..2ead5d5920 100644 --- i/src/qemu/qemu_conf.c +++ w/src/qemu/qemu_conf.c @@ -970,7 +970,18 @@ static int virQEMUDriverConfigLoadMemoryEntry(virQEMUDriverConfigPtr cfg, virConfPtr conf) { - return virConfGetValueString(conf, "memory_backing_dir", &cfg->memoryBackingDir); + char *dir = NULL; + int rc; + + if ((rc = virConfGetValueString(conf, "memory_backing_dir", &dir)) < 0) { + return -1; + } else if (rc > 0) { + VIR_FREE(cfg->memoryBackingDir); + cfg->memoryBackingDir = g_strdup_printf("%s/libvirt/qemu", dir); + return 1; + } + + return 0; } This way we would drop "/libvirt/qemu" in the default configuration and keep it if user overrides it in qemu.conf.