Fix Lost sub directory structure when mapping to a VHD volume#40857
Fix Lost sub directory structure when mapping to a VHD volume#40857kvega005 wants to merge 25 commits into
Conversation
There was a problem hiding this comment.
Pull request overview
This PR fixes an issue where newly formatted ext4 VHD-backed named volumes appear non-empty due to the default lost+found directory, which causes Docker to skip initial copy-up (seeding) from the container image.
Changes:
- Removes
lost+foundfrom freshly formatted (and re-opened) VHD-backed ext4 volumes when it is the only root entry, enabling Docker seeding behavior. - Adds
WSLCVirtualMachinehelpers to list a directory and remove an empty directory in the guest VM. - Adds an end-to-end regression test to validate VHD volume seeding and absence of
lost+found, plus a new localized warning string.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| test/windows/WSLCTests.cpp | Adds an e2e test verifying VHD named volumes seed image data and do not contain lost+found. |
| src/windows/wslcsession/WSLCVirtualMachine.h | Declares new helpers for removing an empty directory and listing directory contents. |
| src/windows/wslcsession/WSLCVirtualMachine.cpp | Implements the new helpers using guest rmdir and ls -A. |
| src/windows/wslcsession/WSLCVhdVolume.cpp | Removes lost+found post-format/mount (create + open paths) when it is the sole root entry; emits warning if removal fails. |
| localization/strings/en-US/Resources.resw | Adds a warning string for when lost+found cannot be removed. |
OneBlue
left a comment
OneBlue
left a comment
There was a problem hiding this comment.
Change looks good, minor comment in ListDirectory's implementation
|
|
||
| auto mountCleanup = wil::scope_exit_log(WI_DIAGNOSTICS_INFO, [&]() { VirtualMachine.Unmount(virtualMachinePath.c_str()); }); | ||
|
|
||
| // mkfs.ext4 always creates a lost+found directory at the filesystem root, |
There was a problem hiding this comment.
Would it be another option to not create the lost and found directory? maybe this is configurable via an option to mkfs?
|
As an alternative, could we use a subdirectory in the ext4 filesystem for the data so docker doesn't see the lost+found? |
I brought that up to @OneBlue before I sent out the PR. It came down to, in his words, "whether we expect to ever be able to mount the VHD to another tool when the container is not running." It might be a bit of strange behavior for users. |
Summary of the Pull Request
Fixes VHD-backed named volumes showing only an empty
lost+founddirectory instead of the container image's contents on first use.When a VHD volume is formatted with
mkfs.ext4, ext4 always creates alost+founddirectory at the filesystem root. Docker only seeds a named volume with the image's contents (copy-up) when the volume appears empty, so the straylost+foundmade VHD volumes look non-empty and silently suppressed seeding — guest (Docker-native) volumes were unaffected. This change removes thelost+founddirectory after formatting so VHD volumes seed just like guest volumes.PR Checklist
en-US/Resources.reswDetailed Description of the Pull Request / Additional comments
Root cause: ext4's
lost+foundmakes a freshly formatted VHD volume non-empty, so Docker skips copy-up and the image's files never get seeded into the volume.Changes:
WSLCVhdVolume: After formatting + mounting,RemoveLostFoundDirectory()stripslost+foundso Docker seeds the volume. The deletion is gated: it only runs whenlost+foundis the sole entry in the volume root, so a volume that already holds data is never touched. Becausermdironly removes empty directories, alost+foundthat captured recovered data is left intact and a localized warning is emitted.Open) path, so volumes created before this fix get migrated (seeded) on next reattach.Notes:
fsck/e2fsck, solost+founddoes not reappear once removed.Validation Steps Performed
NamedVolumesVhdSeedsImageData: creates a VHD volume, mounts it over/etc(guaranteed-populated by the Debian test image), and verifies the image's/etccontent (passwd) is seeded whilelost+foundis absent.lost+foundvisible) and confirmed the fix seeds image contents.