Remove state:"nosave"/"zerovalue" annotations from all waiter.Queues.

Prior to cl/318010298, //pkg/state couldn't handle pointers to struct fields,
which meant that it couldn't handle intrusive linked lists, which meant that it
couldn't handle waiter.Queue, which meant that it couldn't handle epoll. As a
result, VFS1 unregisters all epoll waiters before saving and re-registers them
after loading, and waitable VFS1 file implementations tag their waiter.Queues
state:"nosave" (causing them to be skipped by the save/restore machinery) or
state:"zerovalue" (causing them to only be checked for zero-value-equality on
save).

VFS2 required cl/318010298 to support save/restore (due to the Impl inheritance
pattern used by vfs.FileDescription, vfs.Dentry, etc.); correspondingly, VFS2
epoll assumes that waiter.Queues *will be* saved and loaded correctly, and VFS2
file implementations do not tag waiter.Queues.

Some waiter.Queues, e.g. pipe.Pipe.Queue and kernel.Task.signalQueue, are used
by both VFS1 and VFS2 (the latter via signalfd); as a result of the above,
tagging these Queues state:"nosave" or state:"zerovalue" breaks VFS2 epoll.
Remove VFS1 epoll unregistration before saving (bringing it in line with VFS2),
and remove these tags from all waiter.Queues.

Also clean up after the epoll test added by cl/402323053, which implied this
issue (by instantiating DisableSave in the new test) without reporting it.

PiperOrigin-RevId: 402596216

6 files changed, 8 insertions, 7 deletions

diff --git a/pkg/sentry/fs/fdpipe/pipe.go b/pkg/sentry/fs/fdpipe/pipe.go
index 4370cce33..d2eb03bb7 100644
--- a/pkg/sentry/fs/fdpipe/pipe.go
+++ b/pkg/sentry/fs/fdpipe/pipe.go
@@ -45,7 +45,8 @@ type pipeOperations struct {
 	fsutil.FileNoIoctl              `state:"nosave"`
 	fsutil.FileNoSplice             `state:"nosave"`
 	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
-	waiter.Queue                    `state:"nosave"`
+
+	waiter.Queue
 
 	// flags are the flags used to open the pipe.
 	flags fs.FileFlags `state:".(fs.FileFlags)"`
diff --git a/pkg/sentry/fs/host/inode.go b/pkg/sentry/fs/host/inode.go
index 92d58e3e9..99c37291e 100644
--- a/pkg/sentry/fs/host/inode.go
+++ b/pkg/sentry/fs/host/inode.go
@@ -70,7 +70,7 @@ type inodeFileState struct {
 	descriptor *descriptor `state:"wait"`
 
 	// Event queue for blocking operations.
-	queue waiter.Queue `state:"zerovalue"`
+	queue waiter.Queue
 
 	// sattr is used to restore the inodeOperations.
 	sattr fs.StableAttr `state:"wait"`
diff --git a/pkg/sentry/fs/inotify.go b/pkg/sentry/fs/inotify.go
index 51cd6cd37..941f37116 100644
--- a/pkg/sentry/fs/inotify.go
+++ b/pkg/sentry/fs/inotify.go
@@ -43,7 +43,7 @@ type Inotify struct {
 	// user, since we may aggressively reuse an id on S/R.
 	id uint64
 
-	waiter.Queue `state:"nosave"`
+	waiter.Queue
 
 	// evMu *only* protects the events list. We need a separate lock because
 	// while queuing events, a watch needs to lock the event queue, and using mu
diff --git a/pkg/sentry/fs/lock/lock.go b/pkg/sentry/fs/lock/lock.go
index 7d7a207cc..e39d340fe 100644
--- a/pkg/sentry/fs/lock/lock.go
+++ b/pkg/sentry/fs/lock/lock.go
@@ -132,7 +132,7 @@ type Locks struct {
 	locks LockSet
 
 	// blockedQueue is the queue of waiters that are waiting on a lock.
-	blockedQueue waiter.Queue `state:"zerovalue"`
+	blockedQueue waiter.Queue
 }
 
 // Blocker is the interface used for blocking locks. Passing a nil Blocker
diff --git a/pkg/sentry/fs/timerfd/timerfd.go b/pkg/sentry/fs/timerfd/timerfd.go
index 1c8518d71..ca8be8683 100644
--- a/pkg/sentry/fs/timerfd/timerfd.go
+++ b/pkg/sentry/fs/timerfd/timerfd.go
@@ -43,7 +43,7 @@ type TimerOperations struct {
 	fsutil.FileNoopFlush            `state:"nosave"`
 	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
 
-	events waiter.Queue `state:"zerovalue"`
+	events waiter.Queue
 	timer  *ktime.Timer
 
 	// val is the number of timer expirations since the last successful call to
diff --git a/pkg/sentry/fs/tty/line_discipline.go b/pkg/sentry/fs/tty/line_discipline.go
index f9fca6d8e..f2c9e9668 100644
--- a/pkg/sentry/fs/tty/line_discipline.go
+++ b/pkg/sentry/fs/tty/line_discipline.go
@@ -102,10 +102,10 @@ type lineDiscipline struct {
 	column int
 
 	// masterWaiter is used to wait on the master end of the TTY.
-	masterWaiter waiter.Queue `state:"zerovalue"`
+	masterWaiter waiter.Queue
 
 	// replicaWaiter is used to wait on the replica end of the TTY.
-	replicaWaiter waiter.Queue `state:"zerovalue"`
+	replicaWaiter waiter.Queue
 }
 
 func newLineDiscipline(termios linux.KernelTermios) *lineDiscipline {