btrfs: if BTRFS_IOC_DEV_INFO returns /dev/root generate a friendly error message

On systems that boot without initrd on a btrfs root file systems the
BTRFS_IOC_DEV_INFO ioctl returns /dev/root as backing device. That
sucks, since that is not a real device visible to userspace.

Since this has been that way since forever, and it doesn't look like the
kernel will get fixed soon for this, let's at least generate a useful
error message in this case.

This is not a bug fix, just a tweak to make this more recognizable.

Once the kernel gets fixed to report the correct device nodes in this
case, in a way userspace can make sense of them things will magically
work for systemd, too.

(Note that this doesn't add a log message about this to really all cases
we call get_device() in, but just the main ones that are called in early
boot context, after all all there's no benefit in seeing this message
too many times.)

https://github.com/systemd/systemd/issues/16953
https://bugs.freedesktop.org/show_bug.cgi?id=84689
https://bugzilla.kernel.org/show_bug.cgi?id=89721

1 files changed, 3 insertions, 0 deletions

diff --git a/src/partition/growfs.c b/src/partition/growfs.c
index c097963e0c..8c1a84d981 100644
--- a/src/partition/growfs.c
+++ b/src/partition/growfs.c
@@ -11,6 +11,7 @@
 #include <sys/vfs.h>
 
 #include "blockdev-util.h"
+#include "btrfs-util.h"
 #include "cryptsetup-util.h"
 #include "device-nodes.h"
 #include "dissect-image.h"
@@ -212,6 +213,8 @@ static int run(int argc, char *argv[]) {
                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "\"%s\" is not a mount point: %m", arg_target);
 
         r = get_block_device(arg_target, &devno);
+        if (r == -EUCLEAN)
+                return btrfs_log_dev_root(LOG_ERR, r, arg_target);
         if (r < 0)
                 return log_error_errno(r, "Failed to determine block device of \"%s\": %m", arg_target);