virtiofs: increment lookup count in link()

[benhillis]

link() returns a fuse_entry_out for the target inode, which creates a kernel dentry reference that will later be released via forget(). Without incrementing the lookup count, the subsequent forget would undercount and potentially free the inode prematurely.

[Copilot]

Pull request overview

This PR fixes virtio-fs inode lifetime accounting for link(). Because link() returns a fuse_entry_out for an existing inode, it implicitly creates an additional kernel lookup reference that must be balanced by a later forget(); without incrementing the inode lookup count, the inode could be removed prematurely.

Changes:

• Increment the target inode’s lookup count in Fuse::link() before returning fuse_entry_out.
• Add a VirtioFsInode::add_ref() helper to increment lookup count without updating the inode’s stored path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
vm/devices/virtio/virtiofs/src/lib.rs	Ensures link() properly accounts for the kernel dentry/lookup reference by incrementing the target inode’s lookup count.
vm/devices/virtio/virtiofs/src/inode.rs	Introduces add_ref() as a small API to increment lookup_count without changing the stored path.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.