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, 7 insertions, 8 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_inotify.go b/pkg/sentry/syscalls/linux/sys_inotify.go
index 9cfa660fa..a4f36e01f 100644
--- a/pkg/sentry/syscalls/linux/sys_inotify.go
+++ b/pkg/sentry/syscalls/linux/sys_inotify.go
@@ -22,7 +22,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 )
 
 const allFlags = int(linux.IN_NONBLOCK | linux.IN_CLOEXEC)
@@ -44,9 +43,9 @@ func InotifyInit1(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.
 	n := fs.NewFile(t, dirent, fileFlags, fs.NewInotify(t))
 	defer n.DecRef()
 
-	fd, err := t.FDMap().NewFDFrom(0, n, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, n, kernel.FDFlags{
 		CloseOnExec: flags&linux.IN_CLOEXEC != 0,
-	}, t.ThreadGroup().Limits())
+	})
 
 	if err != nil {
 		return 0, nil, err
@@ -63,8 +62,8 @@ func InotifyInit(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // fdToInotify resolves an fd to an inotify object. If successful, the file will
 // have an extra ref and the caller is responsible for releasing the ref.
-func fdToInotify(t *kernel.Task, fd kdefs.FD) (*fs.Inotify, *fs.File, error) {
-	file := t.FDMap().GetFile(fd)
+func fdToInotify(t *kernel.Task, fd int32) (*fs.Inotify, *fs.File, error) {
+	file := t.GetFile(fd)
 	if file == nil {
 		// Invalid fd.
 		return nil, nil, syscall.EBADF
@@ -82,7 +81,7 @@ func fdToInotify(t *kernel.Task, fd kdefs.FD) (*fs.Inotify, *fs.File, error) {
 
 // InotifyAddWatch implements the inotify_add_watch() syscall.
 func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	mask := args[2].Uint()
 
@@ -114,7 +113,7 @@ func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kern
 		}
 
 		// Copy out to the return frame.
-		fd = kdefs.FD(ino.AddWatch(dirent, mask))
+		fd = ino.AddWatch(dirent, mask)
 
 		return nil
 	})
@@ -123,7 +122,7 @@ func InotifyAddWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kern
 
 // InotifyRmWatch implements the inotify_rm_watch() syscall.
 func InotifyRmWatch(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	wd := args[1].Int()
 
 	ino, file, err := fdToInotify(t, fd)