Remove map from fd_map, change to fd_table.

This renames FDMap to FDTable and drops the kernel.FD type, which had an entire
package to itself and didn't serve much use (it was freely cast between types,
and served as more of an annoyance than providing any protection.)

Based on BenchmarkFDLookupAndDecRef-12, we can expect 5-10 ns per lookup
operation, and 10-15 ns per concurrent lookup operation of savings.

This also fixes two tangential usage issues with the FDMap. Namely, non-atomic
use of NewFDFrom and associated calls to Remove (that are both racy and fail to
drop the reference on the underlying file.)

PiperOrigin-RevId: 256285890

1 files changed, 11 insertions, 11 deletions

diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go
index 89f7d9f94..7e27d1f49 100644
--- a/runsc/boot/loader.go
+++ b/runsc/boot/loader.go
@@ -517,13 +517,13 @@ func (l *Loader) run() error {
 		// Create the FD map, which will set stdin, stdout, and stderr.  If console
 		// is true, then ioctl calls will be passed through to the host fd.
 		ctx := l.rootProcArgs.NewContext(l.k)
-		fdm, err := createFDMap(ctx, l.rootProcArgs.Limits, l.console, l.stdioFDs)
+		fdTable, err := createFDTable(ctx, l.console, l.stdioFDs)
 		if err != nil {
 			return fmt.Errorf("importing fds: %v", err)
 		}
 		// CreateProcess takes a reference on FDMap if successful. We won't need
 		// ours either way.
-		l.rootProcArgs.FDMap = fdm
+		l.rootProcArgs.FDTable = fdTable
 
 		// cid for root container can be empty. Only subcontainers need it to set
 		// the mount location.
@@ -562,13 +562,13 @@ func (l *Loader) run() error {
 			return fmt.Errorf("creating init process: %v", err)
 		}
 
-		// CreateProcess takes a reference on FDMap if successful.
-		l.rootProcArgs.FDMap.DecRef()
+		// CreateProcess takes a reference on FDTable if successful.
+		l.rootProcArgs.FDTable.DecRef()
 	}
 
 	ep.tg = l.k.GlobalInit()
 	if l.console {
-		ttyFile := l.rootProcArgs.FDMap.GetFile(0)
+		ttyFile, _ := l.rootProcArgs.FDTable.Get(0)
 		defer ttyFile.DecRef()
 		ep.tty = ttyFile.FileOperations.(*host.TTYFileOperations)
 
@@ -648,13 +648,13 @@ func (l *Loader) startContainer(spec *specs.Spec, conf *Config, cid string, file
 
 	// Create the FD map, which will set stdin, stdout, and stderr.
 	ctx := procArgs.NewContext(l.k)
-	fdm, err := createFDMap(ctx, procArgs.Limits, false, stdioFDs)
+	fdTable, err := createFDTable(ctx, false, stdioFDs)
 	if err != nil {
 		return fmt.Errorf("importing fds: %v", err)
 	}
-	// CreateProcess takes a reference on FDMap if successful. We won't need ours
-	// either way.
-	procArgs.FDMap = fdm
+	// CreateProcess takes a reference on fdTable if successful. We won't
+	// need ours either way.
+	procArgs.FDTable = fdTable
 
 	// Can't take ownership away from os.File. dup them to get a new FDs.
 	var goferFDs []int
@@ -683,8 +683,8 @@ func (l *Loader) startContainer(spec *specs.Spec, conf *Config, cid string, file
 	}
 	l.k.StartProcess(tg)
 
-	// CreateProcess takes a reference on FDMap if successful.
-	procArgs.FDMap.DecRef()
+	// CreateProcess takes a reference on FDTable if successful.
+	procArgs.FDTable.DecRef()
 
 	l.processes[eid].tg = tg
 	return nil