Add IfChange/ThenChange reminders in fs/proc

There is a lot of code duplication for VFSv2 and this
serves as remind to keep the copies in sync.

Updates #1195

PiperOrigin-RevId: 290139234

pkg/sentry/fs/proc/cgroup.go

@@ -21,6 +21,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 )
 
+// LINT.IfChange
+
 func newCGroupInode(ctx context.Context, msrc *fs.MountSource, cgroupControllers map[string]string) *fs.Inode {
 	// From man 7 cgroups: "For each cgroup hierarchy of which the process
 	// is a member, there is one entry containing three colon-separated
@@ -39,3 +41,5 @@ func newCGroupInode(ctx context.Context, msrc *fs.MountSource, cgroupControllers
 
 	return newStaticProcInode(ctx, msrc, []byte(data))
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/cpuinfo.go

@@ -22,6 +22,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 )
 
+// LINT.IfChange
+
 func newCPUInfo(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 	k := kernel.KernelFromContext(ctx)
 	features := k.FeatureSet()
@@ -35,3 +37,5 @@ func newCPUInfo(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 	}
 	return newStaticProcInode(ctx, msrc, buf.Bytes())
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/exec_args.go

@@ -29,6 +29,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // execArgType enumerates the types of exec arguments that are exposed through
 // proc.
 type execArgType int
@@ -201,3 +203,5 @@ func (f *execArgFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequen
 	}
 	return int64(n), err
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task.go)

pkg/sentry/fs/proc/fds.go

@@ -28,6 +28,8 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
+// LINT.IfChange
+
 // walkDescriptors finds the descriptor (file-flag pair) for the fd identified
 // by p, and calls the toInodeOperations callback with that descriptor.  This is a helper
 // method for implementing fs.InodeOperations.Lookup.
@@ -277,3 +279,5 @@ func (fdid *fdInfoDir) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.
 	}
 	return fs.NewFile(ctx, dirent, flags, fops), nil
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task_files.go)

pkg/sentry/fs/proc/filesystems.go

@@ -23,6 +23,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/seqfile"
 )
 
+// LINT.IfChange
+
 // filesystemsData backs /proc/filesystems.
 //
 // +stateify savable
@@ -59,3 +61,5 @@ func (*filesystemsData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle
 	// Return the SeqData and advance the generation counter.
 	return []seqfile.SeqData{{Buf: buf.Bytes(), Handle: (*filesystemsData)(nil)}}, 1
 }
+
+// LINT.ThenChange(../../fsimpl/proc/filesystem.go)

pkg/sentry/fs/proc/fs.go

@@ -21,6 +21,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 )
 
+// LINT.IfChange
+
 // filesystem is a procfs.
 //
 // +stateify savable
@@ -79,3 +81,5 @@ func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSou
 	// never want them cached.
 	return New(ctx, fs.NewNonCachingMountSource(ctx, f, flags), cgroups)
 }
+
+// LINT.ThenChange(../../fsimpl/proc/filesystem.go)

pkg/sentry/fs/proc/inode.go

@@ -26,6 +26,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
+// LINT.IfChange
+
 // taskOwnedInodeOps wraps an fs.InodeOperations and overrides the UnstableAttr
 // method to return either the task or root as the owner, depending on the
 // task's dumpability.
@@ -131,3 +133,5 @@ func newProcInode(ctx context.Context, iops fs.InodeOperations, msrc *fs.MountSo
 	}
 	return fs.NewInode(ctx, iops, msrc, sattr)
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks.go)

pkg/sentry/fs/proc/loadavg.go

@@ -22,6 +22,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/seqfile"
 )
 
+// LINT.IfChange
+
 // loadavgData backs /proc/loadavg.
 //
 // +stateify savable
@@ -53,3 +55,5 @@ func (d *loadavgData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle)
 		},
 	}, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/meminfo.go

@@ -25,6 +25,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
+// LINT.IfChange
+
 // meminfoData backs /proc/meminfo.
 //
 // +stateify savable
@@ -83,3 +85,5 @@ func (d *meminfoData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle)
 	fmt.Fprintf(&buf, "Shmem:          %8d kB\n", snapshot.Tmpfs/1024)
 	return []seqfile.SeqData{{Buf: buf.Bytes(), Handle: (*meminfoData)(nil)}}, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/mounts.go

@@ -25,6 +25,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 )
 
+// LINT.IfChange
+
 // forEachMountSource runs f for the process root mount and  each mount that is a
 // descendant of the root.
 func forEachMount(t *kernel.Task, fn func(string, *fs.Mount)) {
@@ -195,3 +197,5 @@ func (mf *mountsFile) ReadSeqFileData(ctx context.Context, handle seqfile.SeqHan
 
 	return []seqfile.SeqData{{Buf: buf.Bytes(), Handle: (*mountsFile)(nil)}}, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/net.go

@@ -38,6 +38,8 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 )
 
+// LINT.IfChange
+
 // newNet creates a new proc net entry.
 func (p *proc) newNetDir(ctx context.Context, k *kernel.Kernel, msrc *fs.MountSource) *fs.Inode {
 	var contents map[string]*fs.Inode
@@ -831,3 +833,5 @@ func (n *netUDP) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]se
 	}
 	return data, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_net.go)

pkg/sentry/fs/proc/proc.go

@@ -31,6 +31,8 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
+// LINT.IfChange
+
 // proc is a root proc node.
 //
 // +stateify savable
@@ -249,3 +251,5 @@ func (rpf *rootProcFile) Readdir(ctx context.Context, file *fs.File, ser fs.Dent
 	}
 	return offset, nil
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks.go)

pkg/sentry/fs/proc/stat.go

@@ -24,6 +24,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 )
 
+// LINT.IfChange
+
 // statData backs /proc/stat.
 //
 // +stateify savable
@@ -140,3 +142,5 @@ func (s *statData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]
 		},
 	}, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task_files.go)

pkg/sentry/fs/proc/sys.go

@@ -31,6 +31,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // mmapMinAddrData backs /proc/sys/vm/mmap_min_addr.
 //
 // +stateify savable
@@ -160,3 +162,5 @@ func (hf *hostnameFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequ
 }
 
 var _ fs.FileOperations = (*hostnameFile)(nil)
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_sys.go)

pkg/sentry/fs/proc/sys_net.go

@@ -30,6 +30,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 type tcpMemDir int
 
 const (
@@ -364,3 +366,5 @@ func (p *proc) newSysNetDir(ctx context.Context, msrc *fs.MountSource) *fs.Inode
 	d := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
 	return newProcInode(ctx, d, msrc, fs.SpecialDirectory, nil)
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_sys.go)

pkg/sentry/fs/proc/task.go

@@ -37,6 +37,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // getTaskMM returns t's MemoryManager. If getTaskMM succeeds, the MemoryManager's
 // users count is incremented, and must be decremented by the caller when it is
 // no longer in use.
@@ -800,3 +802,5 @@ func (f *auxvecFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequenc
 	n, err := dst.CopyOut(ctx, buf[offset:])
 	return int64(n), err
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task.go|../../fsimpl/proc/task_files.go)

pkg/sentry/fs/proc/uid_gid_map.go

@@ -30,6 +30,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // idMapInodeOperations implements fs.InodeOperations for
 // /proc/[pid]/{uid,gid}_map.
 //
@@ -177,3 +179,5 @@ func (imfo *idMapFileOperations) Write(ctx context.Context, file *fs.File, src u
 	// count, even if fewer bytes were used.
 	return int64(srclen), nil
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task_files.go)

pkg/sentry/fs/proc/uptime.go

@@ -28,6 +28,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // uptime is a file containing the system uptime.
 //
 // +stateify savable
@@ -85,3 +87,5 @@ func (f *uptimeFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequenc
 	n, err := dst.CopyOut(ctx, s[offset:])
 	return int64(n), err
 }
+
+// LINT.ThenChange(../../fsimpl/proc/tasks_files.go)

pkg/sentry/fs/proc/version.go

@@ -22,6 +22,8 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 )
 
+// LINT.IfChange
+
 // versionData backs /proc/version.
 //
 // +stateify savable
@@ -76,3 +78,5 @@ func (v *versionData) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle)
 		},
 	}, 0
 }
+
+// LINT.ThenChange(../../fsimpl/proc/task_files.go)