[vfs] Refactor hostfs mmap into kernfs util.

PiperOrigin-RevId: 339505487

4 files changed, 4 insertions, 162 deletions

diff --git a/pkg/sentry/fsimpl/host/BUILD b/pkg/sentry/fsimpl/host/BUILD
index dc0f86061..4ae9d6d5e 100644
--- a/pkg/sentry/fsimpl/host/BUILD
+++ b/pkg/sentry/fsimpl/host/BUILD
@@ -33,7 +33,6 @@ go_library(
         "host.go",
         "inode_refs.go",
         "ioctl_unsafe.go",
-        "mmap.go",
         "save_restore.go",
         "socket.go",
         "socket_iovec.go",
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index eeed0f97d..39b902a3e 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -48,6 +48,7 @@ type inode struct {
 	kernfs.InodeNoStatFS
 	kernfs.InodeNotDirectory
 	kernfs.InodeNotSymlink
+	kernfs.CachedMappable
 	kernfs.InodeTemporary // This holds no meaning as this inode can't be Looked up and is always valid.
 
 	locks vfs.FileLocks
@@ -96,16 +97,6 @@ type inode struct {
 	// Event queue for blocking operations.
 	queue waiter.Queue
 
-	// mapsMu protects mappings.
-	mapsMu sync.Mutex `state:"nosave"`
-
-	// If this file is mmappable, mappings tracks mappings of hostFD into
-	// memmap.MappingSpaces.
-	mappings memmap.MappingSet
-
-	// pf implements platform.File for mappings of hostFD.
-	pf inodePlatformFile
-
 	// If haveBuf is non-zero, hostFD represents a pipe, and buf contains data
 	// read from the pipe from previous calls to inode.beforeSave(). haveBuf
 	// and buf are protected by bufMu. haveBuf is accessed using atomic memory
@@ -135,7 +126,7 @@ func newInode(ctx context.Context, fs *filesystem, hostFD int, savable bool, fil
 		isTTY:    isTTY,
 		savable:  savable,
 	}
-	i.pf.inode = i
+	i.CachedMappable.Init(hostFD)
 	i.EnableLeakCheck()
 
 	// If the hostFD can return EWOULDBLOCK when set to non-blocking, do so and
@@ -439,14 +430,7 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre
 			oldpgend, _ := usermem.PageRoundUp(oldSize)
 			newpgend, _ := usermem.PageRoundUp(s.Size)
 			if oldpgend != newpgend {
-				i.mapsMu.Lock()
-				i.mappings.Invalidate(memmap.MappableRange{newpgend, oldpgend}, memmap.InvalidateOpts{
-					// Compare Linux's mm/truncate.c:truncate_setsize() =>
-					// truncate_pagecache() =>
-					// mm/memory.c:unmap_mapping_range(evencows=1).
-					InvalidatePrivate: true,
-				})
-				i.mapsMu.Unlock()
+				i.CachedMappable.InvalidateRange(memmap.MappableRange{newpgend, oldpgend})
 			}
 		}
 	}
@@ -797,7 +781,7 @@ func (f *fileDescription) ConfigureMMap(_ context.Context, opts *memmap.MMapOpts
 		return syserror.ENODEV
 	}
 	i := f.inode
-	i.pf.fileMapperInitOnce.Do(i.pf.fileMapper.Init)
+	i.CachedMappable.InitFileMapperOnce()
 	return vfs.GenericConfigureMMap(&f.vfsfd, i, opts)
 }
 
diff --git a/pkg/sentry/fsimpl/host/mmap.go b/pkg/sentry/fsimpl/host/mmap.go
deleted file mode 100644
index 3d7eb2f96..000000000
--- a/pkg/sentry/fsimpl/host/mmap.go
+++ /dev/null
@@ -1,133 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// 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 host
-
-import (
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/safemem"
-	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
-	"gvisor.dev/gvisor/pkg/sentry/memmap"
-	"gvisor.dev/gvisor/pkg/sync"
-	"gvisor.dev/gvisor/pkg/usermem"
-)
-
-// inodePlatformFile implements memmap.File. It exists solely because inode
-// cannot implement both kernfs.Inode.IncRef and memmap.File.IncRef.
-//
-// inodePlatformFile should only be used if inode.canMap is true.
-//
-// +stateify savable
-type inodePlatformFile struct {
-	*inode
-
-	// fdRefsMu protects fdRefs.
-	fdRefsMu sync.Mutex `state:"nosave"`
-
-	// fdRefs counts references on memmap.File offsets. It is used solely for
-	// memory accounting.
-	fdRefs fsutil.FrameRefSet
-
-	// fileMapper caches mappings of the host file represented by this inode.
-	fileMapper fsutil.HostFileMapper
-
-	// fileMapperInitOnce is used to lazily initialize fileMapper.
-	fileMapperInitOnce sync.Once `state:"nosave"`
-}
-
-// IncRef implements memmap.File.IncRef.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) IncRef(fr memmap.FileRange) {
-	i.fdRefsMu.Lock()
-	i.fdRefs.IncRefAndAccount(fr)
-	i.fdRefsMu.Unlock()
-}
-
-// DecRef implements memmap.File.DecRef.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) DecRef(fr memmap.FileRange) {
-	i.fdRefsMu.Lock()
-	i.fdRefs.DecRefAndAccount(fr)
-	i.fdRefsMu.Unlock()
-}
-
-// MapInternal implements memmap.File.MapInternal.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inodePlatformFile) MapInternal(fr memmap.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
-	return i.fileMapper.MapInternal(fr, i.hostFD, at.Write)
-}
-
-// FD implements memmap.File.FD.
-func (i *inodePlatformFile) FD() int {
-	return i.hostFD
-}
-
-// AddMapping implements memmap.Mappable.AddMapping.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inode) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
-	i.mapsMu.Lock()
-	mapped := i.mappings.AddMapping(ms, ar, offset, writable)
-	for _, r := range mapped {
-		i.pf.fileMapper.IncRefOn(r)
-	}
-	i.mapsMu.Unlock()
-	return nil
-}
-
-// RemoveMapping implements memmap.Mappable.RemoveMapping.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inode) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
-	i.mapsMu.Lock()
-	unmapped := i.mappings.RemoveMapping(ms, ar, offset, writable)
-	for _, r := range unmapped {
-		i.pf.fileMapper.DecRefOn(r)
-	}
-	i.mapsMu.Unlock()
-}
-
-// CopyMapping implements memmap.Mappable.CopyMapping.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inode) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
-	return i.AddMapping(ctx, ms, dstAR, offset, writable)
-}
-
-// Translate implements memmap.Mappable.Translate.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inode) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
-	mr := optional
-	return []memmap.Translation{
-		{
-			Source: mr,
-			File:   &i.pf,
-			Offset: mr.Start,
-			Perms:  usermem.AnyAccess,
-		},
-	}, nil
-}
-
-// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
-//
-// Precondition: i.inode.canMap must be true.
-func (i *inode) InvalidateUnsavable(ctx context.Context) error {
-	// We expect the same host fd across save/restore, so all translations
-	// should be valid.
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/host/save_restore.go b/pkg/sentry/fsimpl/host/save_restore.go
index 7e32a8863..8800652a9 100644
--- a/pkg/sentry/fsimpl/host/save_restore.go
+++ b/pkg/sentry/fsimpl/host/save_restore.go
@@ -68,11 +68,3 @@ func (i *inode) afterLoad() {
 		}
 	}
 }
-
-// afterLoad is invoked by stateify.
-func (i *inodePlatformFile) afterLoad() {
-	if i.fileMapper.IsInited() {
-		// Ensure that we don't call i.fileMapper.Init() again.
-		i.fileMapperInitOnce.Do(func() {})
-	}
-}