Re: [PATCH v3 02/11] KVM: guest_memfd: Handle final folio_put() of guest_memfd pages

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+#endif
+
  #endif
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 6dc2494bd002..734afda268ab 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -933,6 +933,17 @@ enum pagetype {
       PGTY_slab       = 0xf5,
       PGTY_zsmalloc   = 0xf6,
       PGTY_unaccepted = 0xf7,
+     /*
+      * guestmem folios are used to back VM memory as managed by guest_memfd.
+      * Once the last reference is put, instead of freeing these folios back
+      * to the page allocator, they are returned to guest_memfd.
+      *
+      * For now, guestmem will only be set on these folios as long as they
+      * cannot be mapped to user space ("private state"), with the plan of

Might be a bit misleading as I don't think it's set yet as of this series.
But I guess we can keep it to avoid another update later.

You're right, it's not in this series. But as you said, the idea is to
have the least amount of churn in the core mm code.

I proposed adding the latter, to make it clearer that the purpose of these things is to be mapped to user space long-term (-> be a proper folio, like hugetlb folios will have to be), compared to long-term not being a folio (slab, offline, unaccepted, ...).

Might become relevant for people working on the memdesc work, to know what to do here.

(or at least have less questions :) )

--
Cheers,

David / dhildenb





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