tree 2a48bb53591f330162a0ec1d4be855694b8059ab
parent e61588d1d2775304a3a58807f3f37584e775ad3c
author Dangyi Liu <dangyi@google.com> 1652941026 +0000
committer CQ Bot <fuchsia-internal-scoped@luci-project-accounts.iam.gserviceaccount.com> 1652941026 +0000

Revert "[kernel][vm] Robust PageRequest batching"

This reverts commit 2f5df2c170150b19c0fd8adfae34817b8f7a6566.

Reason for revert: causing kernel panic in CI

Original change's description:
> [kernel][vm] Robust PageRequest batching
>
> Changes the batching state from being inferred from the return value of
> PageSource::GetPage, to being queryable from the PageSource. This has
> three benefits
> 1. If an in progress batch request is given to the wrong PageSource it
> can be detected and safely handled. This cannot happen today, but could
> happen when there are additional implementors of PageRequestInterface.
> Specifically with an anonmyous page requester you could have a
> copy-on-write child of a pager backed VMO that has CommitRange called.
> The first page could be present in the parent, but missing in the
> child, requiring a page allocation, which could fail causing the
> PageRequest to be filled in. Since its in batch mode we would continue
> and then possibly find a page missing from the root vmo, and attempt
> to fill in the PageRequest using the PageSource.
> 2. The ZX_ERR_NEXT state that previously meant further batching was
> possible is also used for loop control everywhere in the VM system.
> Propagating GetPage statuses up to the root caller therefore has the
> chance of colliding with an attempt to perform a ForEveryPage or
> equivalent iteration. This does not happen today, but this is a hazard
> that would not be easily detected.
> 3. Additional assertions can be added using this state to ensure the
> page request API is used correctly.
>
> Bug: 99890
> Run-All-Tests: True
> Change-Id: Id35c487c52591f709656c412e5f13933e0225883
> Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/679849
> Commit-Queue: Adrian Danis <adanis@google.com>
> Fuchsia-Auto-Submit: Adrian Danis <adanis@google.com>
> Reviewed-by: Rasha Eqbal <rashaeqbal@google.com>

Bug: 99890
Change-Id: Ib30888a3c8e328841fca0b67e86add0230a77286
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/681056
Commit-Queue: Dangyi Liu <dangyi@google.com>
Reviewed-by: RubberStamper 🤖 <android-build-ayeaye@system.gserviceaccount.com>