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.
Michal