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, 8 insertions, 9 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_sync.go b/pkg/sentry/syscalls/linux/sys_sync.go
index 37225735f..3e55235bd 100644
--- a/pkg/sentry/syscalls/linux/sys_sync.go
+++ b/pkg/sentry/syscalls/linux/sys_sync.go
@@ -19,7 +19,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -32,9 +31,9 @@ func Sync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Syncfs implements linux system call syncfs(2).
 func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -47,9 +46,9 @@ func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Fsync implements linux syscall fsync(2).
 func Fsync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -63,9 +62,9 @@ func Fsync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 //
 // At the moment, it just calls Fsync, which is a big hammer, but correct.
 func Fdatasync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}
@@ -79,6 +78,7 @@ func Fdatasync(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 func SyncFileRange(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	var err error
 
+	fd := args[0].Int()
 	offset := args[1].Int64()
 	nbytes := args[2].Int64()
 	uflags := args[3].Uint()
@@ -97,8 +97,7 @@ func SyncFileRange(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel
 		nbytes = fs.FileMaxOffset
 	}
 
-	fd := kdefs.FD(args[0].Int())
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syserror.EBADF
 	}