Re: [PATCH] daemon: Fix btrfs volume device reverse-translation
by Richard W.M. Jones
On Wed, Dec 10, 2025 at 01:22:33PM +0200, Arye Yurkovsky wrote:
> I tested your patch & it works as-well.
Thanks for testing, This is upstream in
commit c7b204bce3c860c10663fcb9250dd934eaf3390a.
Rich.
> On Wed, Dec 3, 2025 at 1:25 PM Richard W.M. Jones <rjones(a)redhat.com> wrote:
>
> On Wed, Dec 03, 2025 at 11:18:29AM +0000, Richard W.M. Jones via Libguestfs
> wrote:
> > +/* btrfsvol:/dev/sdX also needs reversing. */
> > +static char *
> > +reverse_btrfsvol (const char *device)
> > +{
> > + const char prefix[] = "btrfsvol:";
> > + const char *device_start, *device_end;
> > + CLEANUP_FREE char *device_name = NULL;
> > + CLEANUP_FREE char *reversed_device = NULL;
> > + char *ret;
> > +
> > + device_start = device + strlen (prefix);
> > + device_end = strchr (device_start + strlen ("/dev/"), '/');
> > + device_name = strndup (device_start, device_end - device_start);
>
> ^^ Missing an error check here.
>
> I added this in my copy:
>
> if (device_name == NULL) {
> reply_with_perror ("strndup");
> return NULL;
> }
>
> > +
> > + reversed_device = reverse_device_name_translation (device_name);
> > + if (reversed_device == NULL)
> > + return NULL;
> > +
> > + /* Construct the final btrfsvol: and return it, caller frees. */
> > + if (asprintf (&ret, "%s%s%s", prefix, reversed_device, device_end) ==
> -1) {
> > + reply_with_perror ("asprintf");
> > + return NULL;
> > + }
> > +
> > + return ret;
> > +}
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/
> ~rjones
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--
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[PATCH] daemon: Fix btrfs volume device reverse-translation
by Arye Yurkovsky
Devices associated with btrfs volumes are not reverse-translated
(e.g., btrfsvol:/dev/sdX to sdY).
Forward translation occurs, creating a path mismatch.
This causes errors in subsequent btrfs commands.
---
daemon/device-name-translation.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/daemon/device-name-translation.c b/daemon/device-name-translation.c
index cfebc6495..eaf9a4686 100644
--- a/daemon/device-name-translation.c
+++ b/daemon/device-name-translation.c
@@ -251,9 +251,28 @@ device_name_translation (const char *device)
char *
reverse_device_name_translation (const char *device)
{
+ const char *original_device = device;
char *ret = NULL;
size_t i;
+ const char *prefix = "";
+ const char *suffix = "";
+ bool btrfsvol = STRPREFIX (device, "btrfsvol:");
+ if (btrfsvol) {
+ prefix = "btrfsvol:";
+
+ const char *device_start = device + strlen (prefix);
+ const char *device_end = strchr (device_start + strlen ("/dev/"), '/');
+ device = strndup(device_start, device_end - device_start);
+ if (device == NULL) {
+ perror ("strndup");
+ return NULL;
+ }
+
+ suffix = device_end;
+
+ }
+
/* Look it up in the cache, and if found return the canonical name.
* If not found return a copy of the original string.
*/
@@ -265,13 +284,19 @@ reverse_device_name_translation (const char *device)
char drv[16];
guestfs_int_drive_name (i, drv);
- if (asprintf (&ret, "/dev/sd%s%s", drv, &device[len]) == -1) {
+ if (asprintf (&ret, "%s/dev/sd%s%s%s", prefix, drv, &device[len], suffix) == -1) {
reply_with_perror ("asprintf");
+ if (btrfsvol)
+ free (device);
return NULL;
}
break;
}
}
+ if (btrfsvol) {
+ free (device);
+ device = original_device;
+ }
if (ret == NULL) {
ret = strdup (device);
--
2.52.0.460.gd25c4c69ec-goog
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