livelock in vfs_bio_getpages with vn_io_fault_uiomove

I'm trying to adapt fusefs to use vn_io_fault_uiomove to fix the
deadlock described in the comments above vn_io_fault_doio [^1].  I can
reproduce the deadlock readily enough, and the fix seems simple enough
in other filesystems [^2][^3].  But when I try to apply the same fix
to fusefs, the deadlock changes into a livelock.  vfs_bio_getpages
loops infinitely because it reaches the "redo = true" state.  But on
looping, it never attempts to read from fusefs again.  Instead,
breadn_flags returns 0 without ever calling bufstrategy, from which I
infer that getblkx returned a block with B_CACHE set.  Despite that,
at least one of the requested pages in vfs_bio_getpages fails the
vm_page_all_valid(ma[i]) check.  Debugging further is wandering
outside my areas of expertise.  Could somebody please give me a tip?
What is supposed to mark those pages as valid?  Are there any other
undocumented conditions needed to use vn_io_fault_uiomove that msdosfs
and nfscl just happened to already meet?

Grateful for any help,
-Alan

[^1] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238340
[^2] https://github.com/freebsd/freebsd-src/commit/2aa3944510b50cbe6999344985a5a9c3208063b2
[^3] https://github.com/freebsd/freebsd-src/commit/ddfc47fdc98460b757c6d1dbe4562a0a339f228b