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|
// 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 fsutil
import (
"fmt"
"io"
"sync"
"gvisor.googlesource.com/gvisor/pkg/log"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
"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/usage"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
// Lock order (compare the lock order model in mm/mm.go):
//
// CachingInodeOperations.attrMu ("fs locks")
// CachingInodeOperations.mapsMu ("memmap.Mappable locks not taken by Translate")
// CachingInodeOperations.dataMu ("memmap.Mappable locks taken by Translate")
// CachedFileObject locks
// CachingInodeOperations caches the metadata and content of a CachedFileObject.
// It implements a subset of InodeOperations. As a utility it can be used to
// implement the full set of InodeOperations. Generally it should not be
// embedded to avoid unexpected inherited behavior.
//
// CachingInodeOperations implements Mappable for the CachedFileObject:
//
// - If CachedFileObject.FD returns a value >= 0 then the file descriptor
// will be memory mapped on the host.
//
// - Otherwise, the contents of CachedFileObject are buffered into memory
// managed by the CachingInodeOperations.
//
// Implementations of FileOperations for a CachedFileObject must read and
// write through CachingInodeOperations using Read and Write respectively.
//
// Implementations of InodeOperations.WriteOut must call Sync to write out
// in-memory modifications of data and metadata to the CachedFileObject.
//
// +stateify savable
type CachingInodeOperations struct {
// backingFile is a handle to a cached file object.
backingFile CachedFileObject
// mfp is used to allocate memory that caches backingFile's contents.
mfp pgalloc.MemoryFileProvider
// forcePageCache indicates the sentry page cache should be used regardless
// of whether the platform supports host mapped I/O or not. This must not be
// modified after inode creation.
forcePageCache bool
attrMu sync.Mutex `state:"nosave"`
// attr is unstable cached metadata.
//
// attr is protected by attrMu. attr.Size is protected by both attrMu and
// dataMu; reading it requires locking either mutex, while mutating it
// requires locking both.
attr fs.UnstableAttr
// dirtyAttr is metadata that was updated in-place but hasn't yet
// been successfully written out.
//
// dirtyAttr is protected by attrMu.
dirtyAttr fs.AttrMask
mapsMu sync.Mutex `state:"nosave"`
// mappings tracks mappings of the cached file object into
// memmap.MappingSpaces.
//
// mappings is protected by mapsMu.
mappings memmap.MappingSet
dataMu sync.RWMutex `state:"nosave"`
// cache maps offsets into the cached file to offsets into
// mfp.MemoryFile() that store the file's data.
//
// cache is protected by dataMu.
cache FileRangeSet
// dirty tracks dirty segments in cache.
//
// dirty is protected by dataMu.
dirty DirtySet
// hostFileMapper caches internal mappings of backingFile.FD().
hostFileMapper *HostFileMapper
// refs tracks active references to data in the cache.
//
// refs is protected by dataMu.
refs frameRefSet
}
// CachedFileObject is a file that may require caching.
type CachedFileObject interface {
// ReadToBlocksAt reads up to dsts.NumBytes() bytes from the file to dsts,
// starting at offset, and returns the number of bytes read. ReadToBlocksAt
// may return a partial read without an error.
ReadToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error)
// WriteFromBlocksAt writes up to srcs.NumBytes() bytes from srcs to the
// file, starting at offset, and returns the number of bytes written.
// WriteFromBlocksAt may return a partial write without an error.
WriteFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error)
// SetMaskedAttributes sets the attributes in attr that are true in mask
// on the backing file.
//
// SetMaskedAttributes may be called at any point, regardless of whether
// the file was opened.
SetMaskedAttributes(ctx context.Context, mask fs.AttrMask, attr fs.UnstableAttr) error
// Sync instructs the remote filesystem to sync the file to stable storage.
Sync(ctx context.Context) error
// FD returns a host file descriptor. Return value must be -1 or not -1
// for the lifetime of the CachedFileObject.
//
// FD is called iff the file has been memory mapped. This implies that
// the file was opened (see fs.InodeOperations.GetFile).
FD() int
}
// NewCachingInodeOperations returns a new CachingInodeOperations backed by
// a CachedFileObject and its initial unstable attributes.
func NewCachingInodeOperations(ctx context.Context, backingFile CachedFileObject, uattr fs.UnstableAttr, forcePageCache bool) *CachingInodeOperations {
mfp := pgalloc.MemoryFileProviderFromContext(ctx)
if mfp == nil {
panic(fmt.Sprintf("context.Context %T lacks non-nil value for key %T", ctx, pgalloc.CtxMemoryFileProvider))
}
return &CachingInodeOperations{
backingFile: backingFile,
mfp: mfp,
forcePageCache: forcePageCache,
attr: uattr,
hostFileMapper: NewHostFileMapper(),
}
}
// Release implements fs.InodeOperations.Release.
func (c *CachingInodeOperations) Release() {
c.mapsMu.Lock()
defer c.mapsMu.Unlock()
c.dataMu.Lock()
defer c.dataMu.Unlock()
// The cache should be empty (something has gone terribly wrong if we're
// releasing an inode that is still memory-mapped).
if !c.mappings.IsEmpty() || !c.cache.IsEmpty() || !c.dirty.IsEmpty() {
panic(fmt.Sprintf("Releasing CachingInodeOperations with mappings:\n%s\ncache contents:\n%s\ndirty segments:\n%s", &c.mappings, &c.cache, &c.dirty))
}
}
// UnstableAttr implements fs.InodeOperations.UnstableAttr.
func (c *CachingInodeOperations) UnstableAttr(ctx context.Context, inode *fs.Inode) (fs.UnstableAttr, error) {
c.attrMu.Lock()
attr := c.attr
c.attrMu.Unlock()
return attr, nil
}
// SetPermissions implements fs.InodeOperations.SetPermissions.
func (c *CachingInodeOperations) SetPermissions(ctx context.Context, inode *fs.Inode, perms fs.FilePermissions) bool {
c.attrMu.Lock()
defer c.attrMu.Unlock()
now := ktime.NowFromContext(ctx)
masked := fs.AttrMask{Perms: true}
if err := c.backingFile.SetMaskedAttributes(ctx, masked, fs.UnstableAttr{Perms: perms}); err != nil {
return false
}
c.attr.Perms = perms
c.touchStatusChangeTimeLocked(now)
return true
}
// SetOwner implements fs.InodeOperations.SetOwner.
func (c *CachingInodeOperations) SetOwner(ctx context.Context, inode *fs.Inode, owner fs.FileOwner) error {
if !owner.UID.Ok() && !owner.GID.Ok() {
return nil
}
c.attrMu.Lock()
defer c.attrMu.Unlock()
now := ktime.NowFromContext(ctx)
masked := fs.AttrMask{
UID: owner.UID.Ok(),
GID: owner.GID.Ok(),
}
if err := c.backingFile.SetMaskedAttributes(ctx, masked, fs.UnstableAttr{Owner: owner}); err != nil {
return err
}
if owner.UID.Ok() {
c.attr.Owner.UID = owner.UID
}
if owner.GID.Ok() {
c.attr.Owner.GID = owner.GID
}
c.touchStatusChangeTimeLocked(now)
return nil
}
// SetTimestamps implements fs.InodeOperations.SetTimestamps.
func (c *CachingInodeOperations) SetTimestamps(ctx context.Context, inode *fs.Inode, ts fs.TimeSpec) error {
if ts.ATimeOmit && ts.MTimeOmit {
return nil
}
c.attrMu.Lock()
defer c.attrMu.Unlock()
// Replace requests to use the "system time" with the current time to
// ensure that cached timestamps remain consistent with the remote
// filesystem.
now := ktime.NowFromContext(ctx)
if ts.ATimeSetSystemTime {
ts.ATime = now
}
if ts.MTimeSetSystemTime {
ts.MTime = now
}
masked := fs.AttrMask{
AccessTime: !ts.ATimeOmit,
ModificationTime: !ts.MTimeOmit,
}
if err := c.backingFile.SetMaskedAttributes(ctx, masked, fs.UnstableAttr{AccessTime: ts.ATime, ModificationTime: ts.MTime}); err != nil {
return err
}
if !ts.ATimeOmit {
c.attr.AccessTime = ts.ATime
}
if !ts.MTimeOmit {
c.attr.ModificationTime = ts.MTime
}
c.touchStatusChangeTimeLocked(now)
return nil
}
// Truncate implements fs.InodeOperations.Truncate.
func (c *CachingInodeOperations) Truncate(ctx context.Context, inode *fs.Inode, size int64) error {
c.attrMu.Lock()
defer c.attrMu.Unlock()
// c.attr.Size is protected by both c.attrMu and c.dataMu.
c.dataMu.Lock()
now := ktime.NowFromContext(ctx)
masked := fs.AttrMask{Size: true}
attr := fs.UnstableAttr{Size: size}
if err := c.backingFile.SetMaskedAttributes(ctx, masked, attr); err != nil {
c.dataMu.Unlock()
return err
}
oldSize := c.attr.Size
c.attr.Size = size
c.touchModificationTimeLocked(now)
// We drop c.dataMu here so that we can lock c.mapsMu and invalidate
// mappings below. This allows concurrent calls to Read/Translate/etc.
// These functions synchronize with an in-progress Truncate by refusing to
// use cache contents beyond the new c.attr.Size. (We are still holding
// c.attrMu, so we can't race with Truncate/Write.)
c.dataMu.Unlock()
// Nothing left to do unless shrinking the file.
if size >= oldSize {
return nil
}
oldpgend := fs.OffsetPageEnd(oldSize)
newpgend := fs.OffsetPageEnd(size)
// Invalidate past translations of truncated pages.
if newpgend != oldpgend {
c.mapsMu.Lock()
c.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,
})
c.mapsMu.Unlock()
}
// We are now guaranteed that there are no translations of truncated pages,
// and can remove them from the cache. Since truncated pages have been
// removed from the backing file, they should be dropped without being
// written back.
c.dataMu.Lock()
defer c.dataMu.Unlock()
c.cache.Truncate(uint64(size), c.mfp.MemoryFile())
c.dirty.KeepClean(memmap.MappableRange{uint64(size), oldpgend})
return nil
}
// WriteOut implements fs.InodeOperations.WriteOut.
func (c *CachingInodeOperations) WriteOut(ctx context.Context, inode *fs.Inode) error {
c.attrMu.Lock()
// Write dirty pages back.
c.dataMu.Lock()
err := SyncDirtyAll(ctx, &c.cache, &c.dirty, uint64(c.attr.Size), c.mfp.MemoryFile(), c.backingFile.WriteFromBlocksAt)
c.dataMu.Unlock()
if err != nil {
c.attrMu.Unlock()
return err
}
// SyncDirtyAll above would have grown if needed. On shrinks, the backing
// file is called directly, so size is never needs to be updated.
c.dirtyAttr.Size = false
// Write out cached attributes.
if err := c.backingFile.SetMaskedAttributes(ctx, c.dirtyAttr, c.attr); err != nil {
c.attrMu.Unlock()
return err
}
c.dirtyAttr = fs.AttrMask{}
c.attrMu.Unlock()
// Fsync the remote file.
return c.backingFile.Sync(ctx)
}
// IncLinks increases the link count and updates cached access time.
func (c *CachingInodeOperations) IncLinks(ctx context.Context) {
c.attrMu.Lock()
c.attr.Links++
c.touchModificationTimeLocked(ktime.NowFromContext(ctx))
c.attrMu.Unlock()
}
// DecLinks decreases the link count and updates cached access time.
func (c *CachingInodeOperations) DecLinks(ctx context.Context) {
c.attrMu.Lock()
c.attr.Links--
c.touchModificationTimeLocked(ktime.NowFromContext(ctx))
c.attrMu.Unlock()
}
// TouchAccessTime updates the cached access time in-place to the
// current time. It does not update status change time in-place. See
// mm/filemap.c:do_generic_file_read -> include/linux/h:file_accessed.
func (c *CachingInodeOperations) TouchAccessTime(ctx context.Context, inode *fs.Inode) {
if inode.MountSource.Flags.NoAtime {
return
}
c.attrMu.Lock()
c.touchAccessTimeLocked(ktime.NowFromContext(ctx))
c.attrMu.Unlock()
}
// touchAccesstimeLocked updates the cached access time in-place to the current
// time.
//
// Preconditions: c.attrMu is locked for writing.
func (c *CachingInodeOperations) touchAccessTimeLocked(now time.Time) {
c.attr.AccessTime = now
c.dirtyAttr.AccessTime = true
}
// TouchModificationTime updates the cached modification and status change time
// in-place to the current time.
func (c *CachingInodeOperations) TouchModificationTime(ctx context.Context) {
c.attrMu.Lock()
c.touchModificationTimeLocked(ktime.NowFromContext(ctx))
c.attrMu.Unlock()
}
// touchModificationTimeLocked updates the cached modification and status
// change time in-place to the current time.
//
// Preconditions: c.attrMu is locked for writing.
func (c *CachingInodeOperations) touchModificationTimeLocked(now time.Time) {
c.attr.ModificationTime = now
c.dirtyAttr.ModificationTime = true
c.attr.StatusChangeTime = now
c.dirtyAttr.StatusChangeTime = true
}
// touchStatusChangeTimeLocked updates the cached status change time
// in-place to the current time.
//
// Preconditions: c.attrMu is locked for writing.
func (c *CachingInodeOperations) touchStatusChangeTimeLocked(now time.Time) {
c.attr.StatusChangeTime = now
c.dirtyAttr.StatusChangeTime = true
}
// UpdateUnstable updates the cached unstable attributes. Only non-dirty
// attributes are updated.
func (c *CachingInodeOperations) UpdateUnstable(attr fs.UnstableAttr) {
// All attributes are protected by attrMu.
c.attrMu.Lock()
if !c.dirtyAttr.Usage {
c.attr.Usage = attr.Usage
}
if !c.dirtyAttr.Perms {
c.attr.Perms = attr.Perms
}
if !c.dirtyAttr.UID {
c.attr.Owner.UID = attr.Owner.UID
}
if !c.dirtyAttr.GID {
c.attr.Owner.GID = attr.Owner.GID
}
if !c.dirtyAttr.AccessTime {
c.attr.AccessTime = attr.AccessTime
}
if !c.dirtyAttr.ModificationTime {
c.attr.ModificationTime = attr.ModificationTime
}
if !c.dirtyAttr.StatusChangeTime {
c.attr.StatusChangeTime = attr.StatusChangeTime
}
if !c.dirtyAttr.Links {
c.attr.Links = attr.Links
}
// Size requires holding attrMu and dataMu.
c.dataMu.Lock()
if !c.dirtyAttr.Size {
c.attr.Size = attr.Size
}
c.dataMu.Unlock()
c.attrMu.Unlock()
}
// Read reads from frames and otherwise directly from the backing file
// into dst starting at offset until dst is full, EOF is reached, or an
// error is encountered.
//
// Read may partially fill dst and return a nil error.
func (c *CachingInodeOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
if dst.NumBytes() == 0 {
return 0, nil
}
// Have we reached EOF? We check for this again in
// inodeReadWriter.ReadToBlocks to avoid holding c.attrMu (which would
// serialize reads) or c.dataMu (which would violate lock ordering), but
// check here first (before calling into MM) since reading at EOF is
// common: getting a return value of 0 from a read syscall is the only way
// to detect EOF.
//
// TODO: Separate out c.attr.Size and use atomics instead of
// c.dataMu.
c.dataMu.RLock()
size := c.attr.Size
c.dataMu.RUnlock()
if offset >= size {
return 0, io.EOF
}
n, err := dst.CopyOutFrom(ctx, &inodeReadWriter{ctx, c, offset})
// Compare Linux's mm/filemap.c:do_generic_file_read() => file_accessed().
c.TouchAccessTime(ctx, file.Dirent.Inode)
return n, err
}
// Write writes to frames and otherwise directly to the backing file
// from src starting at offset and until src is empty or an error is
// encountered.
//
// If Write partially fills src, a non-nil error is returned.
func (c *CachingInodeOperations) Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
// Hot path. Avoid defers.
if src.NumBytes() == 0 {
return 0, nil
}
c.attrMu.Lock()
// Compare Linux's mm/filemap.c:__generic_file_write_iter() => file_update_time().
c.touchModificationTimeLocked(ktime.NowFromContext(ctx))
n, err := src.CopyInTo(ctx, &inodeReadWriter{ctx, c, offset})
c.attrMu.Unlock()
return n, err
}
type inodeReadWriter struct {
ctx context.Context
c *CachingInodeOperations
offset int64
}
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (rw *inodeReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
// Hot path. Avoid defers.
rw.c.dataMu.RLock()
// Compute the range to read.
if rw.offset >= rw.c.attr.Size {
rw.c.dataMu.RUnlock()
return 0, io.EOF
}
end := fs.ReadEndOffset(rw.offset, int64(dsts.NumBytes()), rw.c.attr.Size)
if end == rw.offset { // dsts.NumBytes() == 0?
rw.c.dataMu.RUnlock()
return 0, nil
}
mem := rw.c.mfp.MemoryFile()
var done uint64
seg, gap := rw.c.cache.Find(uint64(rw.offset))
for rw.offset < end {
mr := memmap.MappableRange{uint64(rw.offset), uint64(end)}
switch {
case seg.Ok():
// Get internal mappings from the cache.
ims, err := mem.MapInternal(seg.FileRangeOf(seg.Range().Intersect(mr)), usermem.Read)
if err != nil {
rw.c.dataMu.RUnlock()
return done, err
}
// Copy from internal mappings.
n, err := safemem.CopySeq(dsts, ims)
done += n
rw.offset += int64(n)
dsts = dsts.DropFirst64(n)
if err != nil {
rw.c.dataMu.RUnlock()
return done, err
}
// Continue.
seg, gap = seg.NextNonEmpty()
case gap.Ok():
// Read directly from the backing file.
gapmr := gap.Range().Intersect(mr)
dst := dsts.TakeFirst64(gapmr.Length())
n, err := rw.c.backingFile.ReadToBlocksAt(rw.ctx, dst, gapmr.Start)
done += n
rw.offset += int64(n)
dsts = dsts.DropFirst64(n)
// Partial reads are fine. But we must stop reading.
if n != dst.NumBytes() || err != nil {
rw.c.dataMu.RUnlock()
return done, err
}
// Continue.
seg, gap = gap.NextSegment(), FileRangeGapIterator{}
default:
break
}
}
rw.c.dataMu.RUnlock()
return done, nil
}
// maybeGrowFile grows the file's size if data has been written past the old
// size.
//
// Preconditions: rw.c.attrMu and rw.c.dataMu bust be locked.
func (rw *inodeReadWriter) maybeGrowFile() {
// If the write ends beyond the file's previous size, it causes the
// file to grow.
if rw.offset > rw.c.attr.Size {
rw.c.attr.Size = rw.offset
rw.c.dirtyAttr.Size = true
}
if rw.offset > rw.c.attr.Usage {
// This is incorrect if CachingInodeOperations is caching a sparse
// file. (In Linux, keeping inode::i_blocks up to date is the
// filesystem's responsibility.)
rw.c.attr.Usage = rw.offset
rw.c.dirtyAttr.Usage = true
}
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
//
// Preconditions: rw.c.attrMu must be locked.
func (rw *inodeReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
// Hot path. Avoid defers.
rw.c.dataMu.Lock()
// Compute the range to write.
end := fs.WriteEndOffset(rw.offset, int64(srcs.NumBytes()))
if end == rw.offset { // srcs.NumBytes() == 0?
rw.c.dataMu.Unlock()
return 0, nil
}
mf := rw.c.mfp.MemoryFile()
var done uint64
seg, gap := rw.c.cache.Find(uint64(rw.offset))
for rw.offset < end {
mr := memmap.MappableRange{uint64(rw.offset), uint64(end)}
switch {
case seg.Ok() && seg.Start() < mr.End:
// Get internal mappings from the cache.
segMR := seg.Range().Intersect(mr)
ims, err := mf.MapInternal(seg.FileRangeOf(segMR), usermem.Write)
if err != nil {
rw.maybeGrowFile()
rw.c.dataMu.Unlock()
return done, err
}
// Copy to internal mappings.
n, err := safemem.CopySeq(ims, srcs)
done += n
rw.offset += int64(n)
srcs = srcs.DropFirst64(n)
rw.c.dirty.MarkDirty(segMR)
if err != nil {
rw.maybeGrowFile()
rw.c.dataMu.Unlock()
return done, err
}
// Continue.
seg, gap = seg.NextNonEmpty()
case gap.Ok() && gap.Start() < mr.End:
// Write directly to the backing file.
gapmr := gap.Range().Intersect(mr)
src := srcs.TakeFirst64(gapmr.Length())
n, err := rw.c.backingFile.WriteFromBlocksAt(rw.ctx, src, gapmr.Start)
done += n
rw.offset += int64(n)
srcs = srcs.DropFirst64(n)
// Partial writes are fine. But we must stop writing.
if n != src.NumBytes() || err != nil {
rw.maybeGrowFile()
rw.c.dataMu.Unlock()
return done, err
}
// Continue.
seg, gap = gap.NextSegment(), FileRangeGapIterator{}
default:
break
}
}
rw.maybeGrowFile()
rw.c.dataMu.Unlock()
return done, nil
}
// AddMapping implements memmap.Mappable.AddMapping.
func (c *CachingInodeOperations) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
// Hot path. Avoid defers.
c.mapsMu.Lock()
mapped := c.mappings.AddMapping(ms, ar, offset, writable)
// Do this unconditionally since whether we have c.backingFile.FD() >= 0
// can change across save/restore.
for _, r := range mapped {
c.hostFileMapper.IncRefOn(r)
}
if !usage.IncrementalMappedAccounting && !c.forcePageCache && c.backingFile.FD() >= 0 {
for _, r := range mapped {
usage.MemoryAccounting.Inc(r.Length(), usage.Mapped)
}
}
c.mapsMu.Unlock()
return nil
}
// RemoveMapping implements memmap.Mappable.RemoveMapping.
func (c *CachingInodeOperations) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
// Hot path. Avoid defers.
c.mapsMu.Lock()
unmapped := c.mappings.RemoveMapping(ms, ar, offset, writable)
for _, r := range unmapped {
c.hostFileMapper.DecRefOn(r)
}
if !c.forcePageCache && c.backingFile.FD() >= 0 {
if !usage.IncrementalMappedAccounting {
for _, r := range unmapped {
usage.MemoryAccounting.Dec(r.Length(), usage.Mapped)
}
}
c.mapsMu.Unlock()
return
}
// Writeback dirty mapped memory now that there are no longer any
// mappings that reference it. This is our naive memory eviction
// strategy.
mf := c.mfp.MemoryFile()
c.dataMu.Lock()
for _, r := range unmapped {
if err := SyncDirty(ctx, r, &c.cache, &c.dirty, uint64(c.attr.Size), mf, c.backingFile.WriteFromBlocksAt); err != nil {
log.Warningf("Failed to writeback cached data %v: %v", r, err)
}
c.cache.Drop(r, mf)
c.dirty.KeepClean(r)
}
c.dataMu.Unlock()
c.mapsMu.Unlock()
}
// CopyMapping implements memmap.Mappable.CopyMapping.
func (c *CachingInodeOperations) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
return c.AddMapping(ctx, ms, dstAR, offset, writable)
}
// Translate implements memmap.Mappable.Translate.
func (c *CachingInodeOperations) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
// Hot path. Avoid defer.
if !c.forcePageCache && c.backingFile.FD() >= 0 {
return []memmap.Translation{
{
Source: optional,
File: c,
Offset: optional.Start,
Perms: usermem.AnyAccess,
},
}, nil
}
c.dataMu.Lock()
// Constrain translations to c.attr.Size (rounded up) to prevent
// translation to pages that may be concurrently truncated.
pgend := fs.OffsetPageEnd(c.attr.Size)
var beyondEOF bool
if required.End > pgend {
if required.Start >= pgend {
c.dataMu.Unlock()
return nil, &memmap.BusError{io.EOF}
}
beyondEOF = true
required.End = pgend
}
if optional.End > pgend {
optional.End = pgend
}
mf := c.mfp.MemoryFile()
cerr := c.cache.Fill(ctx, required, maxFillRange(required, optional), mf, usage.PageCache, c.backingFile.ReadToBlocksAt)
var ts []memmap.Translation
var translatedEnd uint64
for seg := c.cache.FindSegment(required.Start); seg.Ok() && seg.Start() < required.End; seg, _ = seg.NextNonEmpty() {
segMR := seg.Range().Intersect(optional)
// TODO: Make Translations writable even if writability is
// not required if already kept-dirty by another writable translation.
perms := usermem.AccessType{
Read: true,
Execute: true,
}
if at.Write {
// From this point forward, this memory can be dirtied through the
// mapping at any time.
c.dirty.KeepDirty(segMR)
perms.Write = true
}
ts = append(ts, memmap.Translation{
Source: segMR,
File: mf,
Offset: seg.FileRangeOf(segMR).Start,
Perms: perms,
})
translatedEnd = segMR.End
}
c.dataMu.Unlock()
// Don't return the error returned by c.cache.Fill if it occurred outside
// of required.
if translatedEnd < required.End && cerr != nil {
return ts, &memmap.BusError{cerr}
}
if beyondEOF {
return ts, &memmap.BusError{io.EOF}
}
return ts, nil
}
func maxFillRange(required, optional memmap.MappableRange) memmap.MappableRange {
const maxReadahead = 64 << 10 // 64 KB, chosen arbitrarily
if required.Length() >= maxReadahead {
return required
}
if optional.Length() <= maxReadahead {
return optional
}
optional.Start = required.Start
if optional.Length() <= maxReadahead {
return optional
}
optional.End = optional.Start + maxReadahead
return optional
}
// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
func (c *CachingInodeOperations) InvalidateUnsavable(ctx context.Context) error {
// Whether we have a host fd (and consequently what platform.File is
// mapped) can change across save/restore, so invalidate all translations
// unconditionally.
c.mapsMu.Lock()
defer c.mapsMu.Unlock()
c.mappings.InvalidateAll(memmap.InvalidateOpts{})
// Sync the cache's contents so that if we have a host fd after restore,
// the remote file's contents are coherent.
mf := c.mfp.MemoryFile()
c.dataMu.Lock()
defer c.dataMu.Unlock()
if err := SyncDirtyAll(ctx, &c.cache, &c.dirty, uint64(c.attr.Size), mf, c.backingFile.WriteFromBlocksAt); err != nil {
return err
}
// Discard the cache so that it's not stored in saved state. This is safe
// because per InvalidateUnsavable invariants, no new translations can have
// been returned after we invalidated all existing translations above.
c.cache.DropAll(mf)
c.dirty.RemoveAll()
return nil
}
// IncRef implements platform.File.IncRef. This is used when we directly map an
// underlying host fd and CachingInodeOperations is used as the platform.File
// during translation.
func (c *CachingInodeOperations) IncRef(fr platform.FileRange) {
// Hot path. Avoid defers.
c.dataMu.Lock()
seg, gap := c.refs.Find(fr.Start)
for {
switch {
case seg.Ok() && seg.Start() < fr.End:
seg = c.refs.Isolate(seg, fr)
seg.SetValue(seg.Value() + 1)
seg, gap = seg.NextNonEmpty()
case gap.Ok() && gap.Start() < fr.End:
newRange := gap.Range().Intersect(fr)
if usage.IncrementalMappedAccounting {
usage.MemoryAccounting.Inc(newRange.Length(), usage.Mapped)
}
seg, gap = c.refs.InsertWithoutMerging(gap, newRange, 1).NextNonEmpty()
default:
c.refs.MergeAdjacent(fr)
c.dataMu.Unlock()
return
}
}
}
// DecRef implements platform.File.DecRef. This is used when we directly map an
// underlying host fd and CachingInodeOperations is used as the platform.File
// during translation.
func (c *CachingInodeOperations) DecRef(fr platform.FileRange) {
// Hot path. Avoid defers.
c.dataMu.Lock()
seg := c.refs.FindSegment(fr.Start)
for seg.Ok() && seg.Start() < fr.End {
seg = c.refs.Isolate(seg, fr)
if old := seg.Value(); old == 1 {
if usage.IncrementalMappedAccounting {
usage.MemoryAccounting.Dec(seg.Range().Length(), usage.Mapped)
}
seg = c.refs.Remove(seg).NextSegment()
} else {
seg.SetValue(old - 1)
seg = seg.NextSegment()
}
}
c.refs.MergeAdjacent(fr)
c.dataMu.Unlock()
}
// MapInternal implements platform.File.MapInternal. This is used when we
// directly map an underlying host fd and CachingInodeOperations is used as the
// platform.File during translation.
func (c *CachingInodeOperations) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
return c.hostFileMapper.MapInternal(fr, c.backingFile.FD(), at.Write)
}
// FD implements platform.File.FD. This is used when we directly map an
// underlying host fd and CachingInodeOperations is used as the platform.File
// during translation.
func (c *CachingInodeOperations) FD() int {
return c.backingFile.FD()
}
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