From 6c3072243dfbf70062de5f610e14fd6ed2ce5f32 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Fri, 31 Jan 2020 14:14:52 -0800 Subject: Implement file locks for regular tmpfs files in VFSv2. Add a file lock implementation that can be embedded into various filesystem implementations. Updates #1480 PiperOrigin-RevId: 292614758 --- pkg/sentry/vfs/lock/BUILD | 13 ++++++++ pkg/sentry/vfs/lock/lock.go | 72 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 85 insertions(+) create mode 100644 pkg/sentry/vfs/lock/BUILD create mode 100644 pkg/sentry/vfs/lock/lock.go (limited to 'pkg/sentry/vfs') diff --git a/pkg/sentry/vfs/lock/BUILD b/pkg/sentry/vfs/lock/BUILD new file mode 100644 index 000000000..d9ab063b7 --- /dev/null +++ b/pkg/sentry/vfs/lock/BUILD @@ -0,0 +1,13 @@ +load("//tools:defs.bzl", "go_library") + +package(licenses = ["notice"]) + +go_library( + name = "lock", + srcs = ["lock.go"], + visibility = ["//pkg/sentry:internal"], + deps = [ + "//pkg/sentry/fs/lock", + "//pkg/syserror", + ], +) diff --git a/pkg/sentry/vfs/lock/lock.go b/pkg/sentry/vfs/lock/lock.go new file mode 100644 index 000000000..724dfe743 --- /dev/null +++ b/pkg/sentry/vfs/lock/lock.go @@ -0,0 +1,72 @@ +// 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 lock provides POSIX and BSD style file locking for VFS2 file +// implementations. +// +// The actual implementations can be found in the lock package under +// sentry/fs/lock. +package lock + +import ( + fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock" + "gvisor.dev/gvisor/pkg/syserror" +) + +// FileLocks supports POSIX and BSD style locks, which correspond to fcntl(2) +// and flock(2) respectively in Linux. It can be embedded into various file +// implementations for VFS2 that support locking. +// +// Note that in Linux these two types of locks are _not_ cooperative, because +// race and deadlock conditions make merging them prohibitive. We do the same +// and keep them oblivious to each other. +type FileLocks struct { + // bsd is a set of BSD-style advisory file wide locks, see flock(2). + bsd fslock.Locks + + // posix is a set of POSIX-style regional advisory locks, see fcntl(2). + posix fslock.Locks +} + +// LockBSD tries to acquire a BSD-style lock on the entire file. +func (fl *FileLocks) LockBSD(uid fslock.UniqueID, t fslock.LockType, block fslock.Blocker) error { + if fl.bsd.LockRegion(uid, t, fslock.LockRange{0, fslock.LockEOF}, block) { + return nil + } + return syserror.ErrWouldBlock +} + +// UnlockBSD releases a BSD-style lock on the entire file. +// +// This operation is always successful, even if there did not exist a lock on +// the requested region held by uid in the first place. +func (fl *FileLocks) UnlockBSD(uid fslock.UniqueID) { + fl.bsd.UnlockRegion(uid, fslock.LockRange{0, fslock.LockEOF}) +} + +// LockPOSIX tries to acquire a POSIX-style lock on a file region. +func (fl *FileLocks) LockPOSIX(uid fslock.UniqueID, t fslock.LockType, rng fslock.LockRange, block fslock.Blocker) error { + if fl.posix.LockRegion(uid, t, rng, block) { + return nil + } + return syserror.ErrWouldBlock +} + +// UnlockPOSIX releases a POSIX-style lock on a file region. +// +// This operation is always successful, even if there did not exist a lock on +// the requested region held by uid in the first place. +func (fl *FileLocks) UnlockPOSIX(uid fslock.UniqueID, rng fslock.LockRange) { + fl.posix.UnlockRegion(uid, rng) +} -- cgit v1.2.3 From dcffddf0cae026411e7e678744a1e39dc2b513cf Mon Sep 17 00:00:00 2001 From: Fabricio Voznika Date: Tue, 4 Feb 2020 11:47:41 -0800 Subject: Remove argument from vfs.MountNamespace.DecRef() Updates #1035 PiperOrigin-RevId: 293194631 --- pkg/sentry/fsimpl/devtmpfs/devtmpfs.go | 2 +- pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go | 2 +- pkg/sentry/fsimpl/testutil/testutil.go | 2 +- pkg/sentry/fsimpl/tmpfs/benchmark_test.go | 4 ++-- pkg/sentry/fsimpl/tmpfs/regular_file_test.go | 2 +- pkg/sentry/vfs/mount.go | 3 ++- 6 files changed, 8 insertions(+), 7 deletions(-) (limited to 'pkg/sentry/vfs') diff --git a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go index d36fa74fb..e03a0c665 100644 --- a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go +++ b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go @@ -86,7 +86,7 @@ func NewAccessor(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth // Release must be called when a is no longer in use. func (a *Accessor) Release() { a.root.DecRef() - a.mntns.DecRef(a.vfsObj) + a.mntns.DecRef() } // accessorContext implements context.Context by extending an existing diff --git a/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go b/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go index 82c58c900..73308a2b5 100644 --- a/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go +++ b/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go @@ -45,7 +45,7 @@ func TestDevtmpfs(t *testing.T) { if err != nil { t.Fatalf("failed to create tmpfs root mount: %v", err) } - defer mntns.DecRef(vfsObj) + defer mntns.DecRef() root := mntns.Root() defer root.DecRef() devpop := vfs.PathOperation{ diff --git a/pkg/sentry/fsimpl/testutil/testutil.go b/pkg/sentry/fsimpl/testutil/testutil.go index 1c98335c1..69fd84ddd 100644 --- a/pkg/sentry/fsimpl/testutil/testutil.go +++ b/pkg/sentry/fsimpl/testutil/testutil.go @@ -98,7 +98,7 @@ func (s *System) WithTemporaryContext(ctx context.Context) *System { // Destroy release resources associated with a test system. func (s *System) Destroy() { s.Root.DecRef() - s.mns.DecRef(s.VFS) // Reference on mns passed to NewSystem. + s.mns.DecRef() // Reference on mns passed to NewSystem. } // ReadToEnd reads the contents of fd until EOF to a string. diff --git a/pkg/sentry/fsimpl/tmpfs/benchmark_test.go b/pkg/sentry/fsimpl/tmpfs/benchmark_test.go index 54241c8e8..9fce5e4b4 100644 --- a/pkg/sentry/fsimpl/tmpfs/benchmark_test.go +++ b/pkg/sentry/fsimpl/tmpfs/benchmark_test.go @@ -183,7 +183,7 @@ func BenchmarkVFS2MemfsStat(b *testing.B) { if err != nil { b.Fatalf("failed to create tmpfs root mount: %v", err) } - defer mntns.DecRef(vfsObj) + defer mntns.DecRef() var filePathBuilder strings.Builder filePathBuilder.WriteByte('/') @@ -374,7 +374,7 @@ func BenchmarkVFS2MemfsMountStat(b *testing.B) { if err != nil { b.Fatalf("failed to create tmpfs root mount: %v", err) } - defer mntns.DecRef(vfsObj) + defer mntns.DecRef() var filePathBuilder strings.Builder filePathBuilder.WriteByte('/') diff --git a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go index 2b52992ea..e9f71e334 100644 --- a/pkg/sentry/fsimpl/tmpfs/regular_file_test.go +++ b/pkg/sentry/fsimpl/tmpfs/regular_file_test.go @@ -51,7 +51,7 @@ func newTmpfsRoot(ctx context.Context) (*vfs.VirtualFilesystem, vfs.VirtualDentr root := mntns.Root() return vfsObj, root, func() { root.DecRef() - mntns.DecRef(vfsObj) + mntns.DecRef() }, nil } diff --git a/pkg/sentry/vfs/mount.go b/pkg/sentry/vfs/mount.go index d39528051..1fbb420f9 100644 --- a/pkg/sentry/vfs/mount.go +++ b/pkg/sentry/vfs/mount.go @@ -423,7 +423,8 @@ func (mntns *MountNamespace) IncRef() { } // DecRef decrements mntns' reference count. -func (mntns *MountNamespace) DecRef(vfs *VirtualFilesystem) { +func (mntns *MountNamespace) DecRef() { + vfs := mntns.root.fs.VirtualFilesystem() if refs := atomic.AddInt64(&mntns.refs, -1); refs == 0 { vfs.mountMu.Lock() vfs.mounts.seq.BeginWrite() -- cgit v1.2.3