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

10 files changed, 67 insertions, 59 deletions

diff --git a/pkg/sentry/mm/BUILD b/pkg/sentry/mm/BUILD
index a85ffdef8..c78cb4280 100644
--- a/pkg/sentry/mm/BUILD
+++ b/pkg/sentry/mm/BUILD
@@ -111,6 +111,7 @@ go_library(
         "//pkg/sentry/kernel/shm",
         "//pkg/sentry/limits",
         "//pkg/sentry/memmap",
+        "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
         "//pkg/sentry/platform/safecopy",
         "//pkg/sentry/safemem",
@@ -133,6 +134,7 @@ go_test(
         "//pkg/sentry/context/contexttest",
         "//pkg/sentry/limits",
         "//pkg/sentry/memmap",
+        "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
         "//pkg/sentry/usermem",
         "//pkg/syserror",
diff --git a/pkg/sentry/mm/README.md b/pkg/sentry/mm/README.md
index e485a5ca5..e6efbf565 100644
--- a/pkg/sentry/mm/README.md
+++ b/pkg/sentry/mm/README.md
@@ -153,7 +153,7 @@ manner, and the sentry handles the fault:
     represented by a host file descriptor and offset, since (as noted in
     "Background") this is the memory mapping primitive provided by the host
     kernel. In general, memory is allocated from a temporary host file using the
-    `filemem` package. Supposing that the sentry allocates offset 0x3000 from
+    `pgalloc` package. Supposing that the sentry allocates offset 0x3000 from
     host file "memory-file", the resulting state is:
 
         Sentry VMA:     VA:0x400000 -> /tmp/foo:0x0
@@ -274,7 +274,7 @@ In the sentry:
     methods
     [`platform.AddressSpace.MapFile` and `platform.AddressSpace.Unmap`][platform].
 
-[filemem]: https://gvisor.googlesource.com/gvisor/+/master/pkg/sentry/platform/filemem/filemem.go
 [memmap]: https://gvisor.googlesource.com/gvisor/+/master/pkg/sentry/memmap/memmap.go
 [mm]: https://gvisor.googlesource.com/gvisor/+/master/pkg/sentry/mm/mm.go
+[pgalloc]: https://gvisor.googlesource.com/gvisor/+/master/pkg/sentry/pgalloc/pgalloc.go
 [platform]: https://gvisor.googlesource.com/gvisor/+/master/pkg/sentry/platform/platform.go
diff --git a/pkg/sentry/mm/aio_context.go b/pkg/sentry/mm/aio_context.go
index 5e86d3b49..6cec6387a 100644
--- a/pkg/sentry/mm/aio_context.go
+++ b/pkg/sentry/mm/aio_context.go
@@ -21,6 +21,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/refs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usage"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
@@ -201,24 +202,24 @@ func (ctx *AIOContext) WaitChannel() (chan struct{}, bool) {
 type aioMappable struct {
 	refs.AtomicRefCount
 
-	p  platform.Platform
-	fr platform.FileRange
+	mfp pgalloc.MemoryFileProvider
+	fr  platform.FileRange
 }
 
 var aioRingBufferSize = uint64(usermem.Addr(linux.AIORingSize).MustRoundUp())
 
-func newAIOMappable(p platform.Platform) (*aioMappable, error) {
-	fr, err := p.Memory().Allocate(aioRingBufferSize, usage.Anonymous)
+func newAIOMappable(mfp pgalloc.MemoryFileProvider) (*aioMappable, error) {
+	fr, err := mfp.MemoryFile().Allocate(aioRingBufferSize, usage.Anonymous)
 	if err != nil {
 		return nil, err
 	}
-	return &aioMappable{p: p, fr: fr}, nil
+	return &aioMappable{mfp: mfp, fr: fr}, nil
 }
 
 // DecRef implements refs.RefCounter.DecRef.
 func (m *aioMappable) DecRef() {
 	m.AtomicRefCount.DecRefWithDestructor(func() {
-		m.p.Memory().DecRef(m.fr)
+		m.mfp.MemoryFile().DecRef(m.fr)
 	})
 }
 
@@ -299,7 +300,7 @@ func (m *aioMappable) Translate(ctx context.Context, required, optional memmap.M
 		return []memmap.Translation{
 			{
 				Source: source,
-				File:   m.p.Memory(),
+				File:   m.mfp.MemoryFile(),
 				Offset: m.fr.Start + source.Start,
 			},
 		}, err
@@ -320,7 +321,7 @@ func (mm *MemoryManager) NewAIOContext(ctx context.Context, events uint32) (uint
 	// libaio peeks inside looking for a magic number. This function allocates
 	// a page per context and keeps it set to zeroes to ensure it will not
 	// match AIO_RING_MAGIC and make libaio happy.
-	m, err := newAIOMappable(mm.p)
+	m, err := newAIOMappable(mm.mfp)
 	if err != nil {
 		return 0, err
 	}
diff --git a/pkg/sentry/mm/lifecycle.go b/pkg/sentry/mm/lifecycle.go
index 1ee8ae74e..a71286f14 100644
--- a/pkg/sentry/mm/lifecycle.go
+++ b/pkg/sentry/mm/lifecycle.go
@@ -23,14 +23,16 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/limits"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
 // NewMemoryManager returns a new MemoryManager with no mappings and 1 user.
-func NewMemoryManager(p platform.Platform) *MemoryManager {
+func NewMemoryManager(p platform.Platform, mfp pgalloc.MemoryFileProvider) *MemoryManager {
 	return &MemoryManager{
 		p:           p,
+		mfp:         mfp,
 		haveASIO:    p.SupportsAddressSpaceIO(),
 		privateRefs: &privateRefs{},
 		users:       1,
@@ -60,6 +62,7 @@ func (mm *MemoryManager) Fork(ctx context.Context) (*MemoryManager, error) {
 	defer mm.mappingMu.RUnlock()
 	mm2 := &MemoryManager{
 		p:           mm.p,
+		mfp:         mm.mfp,
 		haveASIO:    mm.haveASIO,
 		layout:      mm.layout,
 		privateRefs: mm.privateRefs,
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index e2c636f38..6ed838d64 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -40,6 +40,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
@@ -50,10 +51,9 @@ import (
 //
 // +stateify savable
 type MemoryManager struct {
-	// p is the platform.
-	//
-	// p is immutable.
-	p platform.Platform
+	// p and mfp are immutable.
+	p   platform.Platform
+	mfp pgalloc.MemoryFileProvider
 
 	// haveASIO is the cached result of p.SupportsAddressSpaceIO(). Aside from
 	// eliminating an indirect call in the hot I/O path, this makes
@@ -369,8 +369,8 @@ func (v *vma) loadRealPerms(b int) {
 // +stateify savable
 type pma struct {
 	// file is the file mapped by this pma. Only pmas for which file ==
-	// platform.Platform.Memory() may be saved. pmas hold a reference to the
-	// corresponding file range while they exist.
+	// MemoryManager.mfp.MemoryFile() may be saved. pmas hold a reference to
+	// the corresponding file range while they exist.
 	file platform.File `state:"nosave"`
 
 	// off is the offset into file at which this pma begins.
@@ -387,7 +387,7 @@ type pma struct {
 
 	// private is true if this pma represents private memory.
 	//
-	// If private is true, file must be platform.Platform.Memory(), the pma
+	// If private is true, file must be MemoryManager.mfp.MemoryFile(), the pma
 	// holds a reference on the mapped memory that is tracked in privateRefs,
 	// and calls to Invalidate for which
 	// memmap.InvalidateOpts.InvalidatePrivate is false should ignore the pma.
@@ -405,9 +405,9 @@ type pma struct {
 type privateRefs struct {
 	mu sync.Mutex `state:"nosave"`
 
-	// refs maps offsets into Platform.Memory() to the number of pmas (or,
-	// equivalently, MemoryManagers) that share ownership of the memory at that
-	// offset.
+	// refs maps offsets into MemoryManager.mfp.MemoryFile() to the number of
+	// pmas (or, equivalently, MemoryManagers) that share ownership of the
+	// memory at that offset.
 	refs fileRefcountSet
 }
 
diff --git a/pkg/sentry/mm/mm_test.go b/pkg/sentry/mm/mm_test.go
index f2db43196..e12cb3bd1 100644
--- a/pkg/sentry/mm/mm_test.go
+++ b/pkg/sentry/mm/mm_test.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context/contexttest"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/limits"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
@@ -29,7 +30,8 @@ import (
 
 func testMemoryManager(ctx context.Context) *MemoryManager {
 	p := platform.FromContext(ctx)
-	mm := NewMemoryManager(p)
+	mfp := pgalloc.MemoryFileProviderFromContext(ctx)
+	mm := NewMemoryManager(p, mfp)
 	mm.layout = arch.MmapLayout{
 		MinAddr:      p.MinUserAddress(),
 		MaxAddr:      p.MaxUserAddress(),
diff --git a/pkg/sentry/mm/pma.go b/pkg/sentry/mm/pma.go
index d102035d8..bb779a45b 100644
--- a/pkg/sentry/mm/pma.go
+++ b/pkg/sentry/mm/pma.go
@@ -328,8 +328,8 @@ func (mm *MemoryManager) insertPMAsLocked(ctx context.Context, vseg vmaIterator,
 		// Limit the range we allocate to ar, aligned to privateAllocUnit.
 		maskAR := privateAligned(ar)
 		allocAR := optAR.Intersect(maskAR)
-		mem := mm.p.Memory()
-		fr, err := mem.Allocate(uint64(allocAR.Length()), usage.Anonymous)
+		mf := mm.mfp.MemoryFile()
+		fr, err := mf.Allocate(uint64(allocAR.Length()), usage.Anonymous)
 		if err != nil {
 			return pgap, err
 		}
@@ -342,10 +342,10 @@ func (mm *MemoryManager) insertPMAsLocked(ctx context.Context, vseg vmaIterator,
 		}
 
 		mm.addRSSLocked(allocAR)
-		mem.IncRef(fr)
+		mf.IncRef(fr)
 
 		return mm.pmas.Insert(pgap, allocAR, pma{
-			file:              mem,
+			file:              mf,
 			off:               fr.Start,
 			vmaEffectivePerms: vma.effectivePerms,
 			vmaMaxPerms:       vma.maxPerms,
@@ -426,7 +426,7 @@ func (mm *MemoryManager) breakCopyOnWriteLocked(pseg pmaIterator, ar usermem.Add
 	// Limit the range we copy to ar, aligned to privateAllocUnit.
 	maskAR := privateAligned(ar)
 	var invalidatedIterators, didUnmapAS bool
-	mem := mm.p.Memory()
+	mf := mm.mfp.MemoryFile()
 	for {
 		if mm.isPMACopyOnWriteLocked(pseg) {
 			// Determine the range to copy.
@@ -438,7 +438,7 @@ func (mm *MemoryManager) breakCopyOnWriteLocked(pseg pmaIterator, ar usermem.Add
 			}
 
 			// Copy contents.
-			fr, err := platform.AllocateAndFill(mem, uint64(copyAR.Length()), usage.Anonymous, &safemem.BlockSeqReader{mm.internalMappingsLocked(pseg, copyAR)})
+			fr, err := mf.AllocateAndFill(uint64(copyAR.Length()), usage.Anonymous, &safemem.BlockSeqReader{mm.internalMappingsLocked(pseg, copyAR)})
 			if _, ok := err.(safecopy.BusError); ok {
 				// If we got SIGBUS during the copy, deliver SIGBUS to
 				// userspace (instead of SIGSEGV) if we're breaking
@@ -449,7 +449,7 @@ func (mm *MemoryManager) breakCopyOnWriteLocked(pseg pmaIterator, ar usermem.Add
 				return pseg.PrevGap(), invalidatedIterators, err
 			}
 			mm.incPrivateRef(fr)
-			mem.IncRef(fr)
+			mf.IncRef(fr)
 
 			// Unmap all of maskAR, not just copyAR, to minimize host syscalls.
 			// AddressSpace mappings must be removed before mm.decPrivateRef().
@@ -471,7 +471,7 @@ func (mm *MemoryManager) breakCopyOnWriteLocked(pseg pmaIterator, ar usermem.Add
 			}
 			pma.file.DecRef(pseg.fileRange())
 
-			pma.file = mem
+			pma.file = mf
 			pma.off = fr.Start
 			pma.private = true
 			pma.needCOW = false
@@ -881,9 +881,9 @@ func (mm *MemoryManager) decPrivateRef(fr platform.FileRange) {
 	refSet.MergeAdjacent(fr)
 	mm.privateRefs.mu.Unlock()
 
-	mem := mm.p.Memory()
+	mf := mm.mfp.MemoryFile()
 	for _, fr := range freed {
-		mem.DecRef(fr)
+		mf.DecRef(fr)
 	}
 }
 
diff --git a/pkg/sentry/mm/save_restore.go b/pkg/sentry/mm/save_restore.go
index 6e7080a84..46e0e0754 100644
--- a/pkg/sentry/mm/save_restore.go
+++ b/pkg/sentry/mm/save_restore.go
@@ -37,12 +37,12 @@ func (mm *MemoryManager) InvalidateUnsavable(ctx context.Context) error {
 
 // beforeSave is invoked by stateify.
 func (mm *MemoryManager) beforeSave() {
-	mem := mm.p.Memory()
+	mf := mm.mfp.MemoryFile()
 	for pseg := mm.pmas.FirstSegment(); pseg.Ok(); pseg = pseg.NextSegment() {
-		if pma := pseg.ValuePtr(); pma.file != mem {
+		if pma := pseg.ValuePtr(); pma.file != mf {
 			// InvalidateUnsavable should have caused all such pmas to be
 			// invalidated.
-			panic(fmt.Sprintf("Can't save pma %#v with non-Memory file of type %T:\n%s", pseg.Range(), pma.file, mm))
+			panic(fmt.Sprintf("Can't save pma %#v with non-MemoryFile of type %T:\n%s", pseg.Range(), pma.file, mm))
 		}
 	}
 }
@@ -50,8 +50,8 @@ func (mm *MemoryManager) beforeSave() {
 // afterLoad is invoked by stateify.
 func (mm *MemoryManager) afterLoad() {
 	mm.haveASIO = mm.p.SupportsAddressSpaceIO()
-	mem := mm.p.Memory()
+	mf := mm.mfp.MemoryFile()
 	for pseg := mm.pmas.FirstSegment(); pseg.Ok(); pseg = pseg.NextSegment() {
-		pseg.ValuePtr().file = mem
+		pseg.ValuePtr().file = mf
 	}
 }
diff --git a/pkg/sentry/mm/special_mappable.go b/pkg/sentry/mm/special_mappable.go
index 64d0dd3f6..aa94d7d6a 100644
--- a/pkg/sentry/mm/special_mappable.go
+++ b/pkg/sentry/mm/special_mappable.go
@@ -18,6 +18,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/refs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usage"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
@@ -33,24 +34,24 @@ import (
 type SpecialMappable struct {
 	refs.AtomicRefCount
 
-	p    platform.Platform
+	mfp  pgalloc.MemoryFileProvider
 	fr   platform.FileRange
 	name string
 }
 
 // NewSpecialMappable returns a SpecialMappable that owns fr, which represents
-// offsets in p.Memory() that contain the SpecialMappable's data. The
+// offsets in mfp.MemoryFile() that contain the SpecialMappable's data. The
 // SpecialMappable will use the given name in /proc/[pid]/maps.
 //
 // Preconditions: fr.Length() != 0.
-func NewSpecialMappable(name string, p platform.Platform, fr platform.FileRange) *SpecialMappable {
-	return &SpecialMappable{p: p, fr: fr, name: name}
+func NewSpecialMappable(name string, mfp pgalloc.MemoryFileProvider, fr platform.FileRange) *SpecialMappable {
+	return &SpecialMappable{mfp: mfp, fr: fr, name: name}
 }
 
 // DecRef implements refs.RefCounter.DecRef.
 func (m *SpecialMappable) DecRef() {
 	m.AtomicRefCount.DecRefWithDestructor(func() {
-		m.p.Memory().DecRef(m.fr)
+		m.mfp.MemoryFile().DecRef(m.fr)
 	})
 }
 
@@ -99,7 +100,7 @@ func (m *SpecialMappable) Translate(ctx context.Context, required, optional memm
 		return []memmap.Translation{
 			{
 				Source: source,
-				File:   m.p.Memory(),
+				File:   m.mfp.MemoryFile(),
 				Offset: m.fr.Start + source.Start,
 			},
 		}, err
@@ -109,19 +110,19 @@ func (m *SpecialMappable) Translate(ctx context.Context, required, optional memm
 
 // InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
 func (m *SpecialMappable) InvalidateUnsavable(ctx context.Context) error {
-	// Since data is stored in platform.Platform.Memory(), the contents of
-	// which are preserved across save/restore, we don't need to do anything.
+	// Since data is stored in pgalloc.MemoryFile, the contents of which are
+	// preserved across save/restore, we don't need to do anything.
 	return nil
 }
 
-// Platform returns the Platform whose Memory stores the SpecialMappable's
-// contents.
-func (m *SpecialMappable) Platform() platform.Platform {
-	return m.p
+// MemoryFileProvider returns the MemoryFileProvider whose MemoryFile stores
+// the SpecialMappable's contents.
+func (m *SpecialMappable) MemoryFileProvider() pgalloc.MemoryFileProvider {
+	return m.mfp
 }
 
-// FileRange returns the offsets into Platform().Memory() that store the
-// SpecialMappable's contents.
+// FileRange returns the offsets into MemoryFileProvider().MemoryFile() that
+// store the SpecialMappable's contents.
 func (m *SpecialMappable) FileRange() platform.FileRange {
 	return m.fr
 }
@@ -137,7 +138,7 @@ func (m *SpecialMappable) Length() uint64 {
 // TODO: The use of SpecialMappable is a lazy code reuse hack. Linux
 // uses an ephemeral file created by mm/shmem.c:shmem_zero_setup(); we should
 // do the same to get non-zero device and inode IDs.
-func NewSharedAnonMappable(length uint64, p platform.Platform) (*SpecialMappable, error) {
+func NewSharedAnonMappable(length uint64, mfp pgalloc.MemoryFileProvider) (*SpecialMappable, error) {
 	if length == 0 {
 		return nil, syserror.EINVAL
 	}
@@ -145,10 +146,9 @@ func NewSharedAnonMappable(length uint64, p platform.Platform) (*SpecialMappable
 	if !ok {
 		return nil, syserror.EINVAL
 	}
-
-	fr, err := p.Memory().Allocate(uint64(alignedLen), usage.Anonymous)
+	fr, err := mfp.MemoryFile().Allocate(uint64(alignedLen), usage.Anonymous)
 	if err != nil {
 		return nil, err
 	}
-	return NewSpecialMappable("/dev/zero (deleted)", p, fr), nil
+	return NewSpecialMappable("/dev/zero (deleted)", mfp, fr), nil
 }
diff --git a/pkg/sentry/mm/syscalls.go b/pkg/sentry/mm/syscalls.go
index fd6929e08..b56e0d3b9 100644
--- a/pkg/sentry/mm/syscalls.go
+++ b/pkg/sentry/mm/syscalls.go
@@ -24,7 +24,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/futex"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/limits"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
@@ -99,7 +99,7 @@ func (mm *MemoryManager) MMap(ctx context.Context, opts memmap.MMapOpts) (userme
 			if opts.MappingIdentity != nil {
 				return 0, syserror.EINVAL
 			}
-			m, err := NewSharedAnonMappable(opts.Length, platform.FromContext(ctx))
+			m, err := NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
 			if err != nil {
 				return 0, err
 			}
@@ -965,7 +965,7 @@ func (mm *MemoryManager) Decommit(addr usermem.Addr, length uint64) error {
 	// ensures that Decommit immediately reduces host memory usage.
 	var didUnmapAS bool
 	pseg := mm.pmas.LowerBoundSegment(ar.Start)
-	mem := mm.p.Memory()
+	mf := mm.mfp.MemoryFile()
 	for vseg := mm.vmas.LowerBoundSegment(ar.Start); vseg.Ok() && vseg.Start() < ar.End; vseg = vseg.NextSegment() {
 		vma := vseg.ValuePtr()
 		if vma.mlockMode != memmap.MLockNone {
@@ -984,7 +984,7 @@ func (mm *MemoryManager) Decommit(addr usermem.Addr, length uint64) error {
 			if pma.private && !mm.isPMACopyOnWriteLocked(pseg) {
 				psegAR := pseg.Range().Intersect(ar)
 				if vsegAR.IsSupersetOf(psegAR) && vma.mappable == nil {
-					if err := mem.Decommit(pseg.fileRangeOf(psegAR)); err == nil {
+					if err := mf.Decommit(pseg.fileRangeOf(psegAR)); err == nil {
 						pseg = pseg.NextSegment()
 						continue
 					}