Skip to content

boot: an overlay is mounted once its NBD device has a size #28

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We鈥檒l occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
aledbf merged 1 commit into from
Sep 29, 2026
Merged

boot: an overlay is mounted once its NBD device has a size #28

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
10 changes: 7 additions & 3 deletions boot/bench_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -621,11 +621,15 @@ func editOverlay(t *testing.T, overlay string, v variant) {
mustRun(t, "sudo", "qemu-nbd", "--connect="+dev, "-f", "qcow2", overlay)
defer mustRun(t, "sudo", "qemu-nbd", "--disconnect", dev)

// The kernel needs a moment to read the partition table it will not find: this image is
// partitionless, so the device itself is the filesystem.
// The device's size arrives after qemu-nbd returns: a mount before it reads a device of
// zero bytes and fails with "can't read superblock", which a runner reconnecting right after
// the previous boot's disconnect did (the kernel logged the capacity change 7 ms after the
// failed mount). blkid -p and not blkid: without it blkid answers from its cache, and said
// ext4 about a device that was still empty.
var ok bool
for range 20 {
if exec.Command("sudo", "blkid", dev).Run() == nil {
size, err := exec.Command("sudo", "blockdev", "--getsize64", dev).Output()
if err == nil && strings.TrimSpace(string(size)) != "0" && exec.Command("sudo", "blkid", "-p", dev).Run() == nil {
ok = true
break
}
Expand Down