Sorry, looking at this again I'm a bit confused. What does vt9p_detach() have to do with directory unmounting? vt9p_detach() runs when the virtio device itself is detached, which I presume wouldn't happen unless someone used devctl(8) to do so explicitly. What am I missing?

In D57500#1351592, @markj wrote:

Sorry, looking at this again I'm a bit confused. What does vt9p_detach() have to do with directory unmounting? vt9p_detach() runs when the virtio device itself is detached, which I presume wouldn't happen unless someone used devctl(8) to do so explicitly. What am I missing?

The title was misleading. It should be "disallow P9 device to detach if a session is in progress." My bad.

What does vt9p_detach() have to do with directory unmounting

We don't check whether someone is using the channel before detaching the device. If you unmount after kldunload, then you get a panic.

Edit: actually, it seems you don't even need to umount for the panic. Just kldunload is enough.

njain15_protonmail.com retitled this revision from p9fs: Disallow directory unmounting if a session is in progress to p9fs: Disallow P9 device to detach if a session is in progress.Mon, Aug 17, 7:39 PM

Closed by commit rGb39457bb1566: virtio_p9fs: Disallow detach if a session is in progress (authored by njain15_protonmail.com, committed by markj). · Explain WhyTue, Aug 18, 2:43 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rGb39457bb1566: virtio_p9fs: Disallow detach if a session is in progress.

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