[roll] Roll fuchsia [kernel][vm] Introduce supply_zero_offset
Pager-backed VMOs get a new supply_zero_offset, which is the offset
beyond which new page requests are implicitly fulfilled with zero pages
instead of forwarding a read request to the user pager.
The supply_zero_offset is used as follows:
- The supply_zero_offset is initialized to the VMO size on creation.
- A resize up leaves the supply_zero_offset unchanged.
- A resize down sets the supply_zero_offset to min(supply_zero_offset,
size).
- The kernel supplies zero pages for the range [supply_zero_offset,
size).
This CL introduces the supply_zero_offset and updates it on resizes.
Supplying zero pages beyond supply_zero_offset will be implemented in a
following CL.
Test: kernel-unittests
Original-Bug: 94371
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/650102
Original-Revision: ff2165343ba603c922290200a9bfc7434b63bccd
GitOrigin-RevId: a83dcfe5c32b8450d237118fa925201dc5755859
Change-Id: Ie6e1e38784d26b6b2ef7cecbdb6c4d5142033348
diff --git a/stem b/stem
index 1f5829e..df24a45 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
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+ revision="ff2165343ba603c922290200a9bfc7434b63bccd"/>
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