Decouple filemem from platform and move it to pgalloc.MemoryFile.

This is in preparation for improved page cache reclaim, which requires
greater integration between the page cache and page allocator.

PiperOrigin-RevId: 238444706
Change-Id: Id24141b3678d96c7d7dc24baddd9be555bffafe4

1 files changed, 168 insertions, 0 deletions

diff --git a/pkg/sentry/pgalloc/pgalloc_test.go b/pkg/sentry/pgalloc/pgalloc_test.go
new file mode 100644
index 000000000..726623c1a
--- /dev/null
+++ b/pkg/sentry/pgalloc/pgalloc_test.go
@@ -0,0 +1,168 @@
+// Copyright 2018 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pgalloc
+
+import (
+	"testing"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+const (
+	page     = usermem.PageSize
+	hugepage = usermem.HugePageSize
+)
+
+func TestFindUnallocatedRange(t *testing.T) {
+	for _, test := range []struct {
+		desc           string
+		usage          *usageSegmentDataSlices
+		start          uint64
+		length         uint64
+		alignment      uint64
+		unallocated    uint64
+		minUnallocated uint64
+	}{
+		{
+			desc:           "Initial allocation succeeds",
+			usage:          &usageSegmentDataSlices{},
+			start:          0,
+			length:         page,
+			alignment:      page,
+			unallocated:    0,
+			minUnallocated: 0,
+		},
+		{
+			desc: "Allocation begins at start of file",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{page},
+				End:    []uint64{2 * page},
+				Values: []usageInfo{{refs: 1}},
+			},
+			start:          0,
+			length:         page,
+			alignment:      page,
+			unallocated:    0,
+			minUnallocated: 0,
+		},
+		{
+			desc: "In-use frames are not allocatable",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{0, page},
+				End:    []uint64{page, 2 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 2}},
+			},
+			start:          0,
+			length:         page,
+			alignment:      page,
+			unallocated:    2 * page,
+			minUnallocated: 2 * page,
+		},
+		{
+			desc: "Reclaimable frames are not allocatable",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{0, page, 2 * page},
+				End:    []uint64{page, 2 * page, 3 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 0}, {refs: 1}},
+			},
+			start:          0,
+			length:         page,
+			alignment:      page,
+			unallocated:    3 * page,
+			minUnallocated: 3 * page,
+		},
+		{
+			desc: "Gaps between in-use frames are allocatable",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{0, 2 * page},
+				End:    []uint64{page, 3 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 1}},
+			},
+			start:          0,
+			length:         page,
+			alignment:      page,
+			unallocated:    page,
+			minUnallocated: page,
+		},
+		{
+			desc: "Inadequately-sized gaps are rejected",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{0, 2 * page},
+				End:    []uint64{page, 3 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 1}},
+			},
+			start:          0,
+			length:         2 * page,
+			alignment:      page,
+			unallocated:    3 * page,
+			minUnallocated: page,
+		},
+		{
+			desc: "Hugepage alignment is honored",
+			usage: &usageSegmentDataSlices{
+				Start: []uint64{0, hugepage + page},
+				// Hugepage-sized gap here that shouldn't be allocated from
+				// since it's incorrectly aligned.
+				End:    []uint64{page, hugepage + 2*page},
+				Values: []usageInfo{{refs: 1}, {refs: 1}},
+			},
+			start:          0,
+			length:         hugepage,
+			alignment:      hugepage,
+			unallocated:    2 * hugepage,
+			minUnallocated: page,
+		},
+		{
+			desc: "Pages before start ignored",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{page, 3 * page},
+				End:    []uint64{2 * page, 4 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 2}},
+			},
+			start:          page,
+			length:         page,
+			alignment:      page,
+			unallocated:    2 * page,
+			minUnallocated: 2 * page,
+		},
+		{
+			desc: "start may be in the middle of segment",
+			usage: &usageSegmentDataSlices{
+				Start:  []uint64{0, 3 * page},
+				End:    []uint64{2 * page, 4 * page},
+				Values: []usageInfo{{refs: 1}, {refs: 2}},
+			},
+			start:          page,
+			length:         page,
+			alignment:      page,
+			unallocated:    2 * page,
+			minUnallocated: 2 * page,
+		},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			var usage usageSet
+			if err := usage.ImportSortedSlices(test.usage); err != nil {
+				t.Fatalf("Failed to initialize usage from %v: %v", test.usage, err)
+			}
+			unallocated, minUnallocated := findUnallocatedRange(&usage, test.start, test.length, test.alignment)
+			if unallocated != test.unallocated {
+				t.Errorf("findUnallocatedRange(%v, %x, %x, %x): got unallocated %x, wanted %x", test.usage, test.start, test.length, test.alignment, unallocated, test.unallocated)
+			}
+			if minUnallocated != test.minUnallocated {
+				t.Errorf("findUnallocatedRange(%v, %x, %x, %x): got minUnallocated %x, wanted %x", test.usage, test.start, test.length, test.alignment, minUnallocated, test.minUnallocated)
+			}
+		})
+	}
+}