Minor filesystem cleanups

- Update the remaining platform.File references in comments and
  documentation. platform.File has been moved in memmap by commit
  f347a578b7 ("Move platform.File in memmap").

- Remove redundant bit operations in statTo in tmpfs. STATX_SIZE and
  STATX_BLOCKS has been set at the beginning of the function, there
  is no need to do it again for regular files.

- Change "\tmp" to "/tmp" in pathname, as '\' is not a valid path
  delimiter in Linux. "/tmp" looks better.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>

pkg/sentry/fsimpl/gofer/gofer.go

@@ -950,7 +950,7 @@ type dentry struct {
 	// tracks dirty segments in cache. dirty is protected by dataMu.
 	dirty fsutil.DirtySet
 
-	// pf implements platform.File for mappings of hostFD.
+	// pf implements memmap.File for mappings of hostFD.
 	pf dentryPlatformFile
 
 	// If this dentry represents a symbolic link, InteropModeShared is not in

pkg/sentry/fsimpl/tmpfs/tmpfs.go

@@ -642,7 +642,6 @@ func (i *inode) statTo(stat *linux.Statx) {
 	stat.DevMinor = i.fs.devMinor
 	switch impl := i.impl.(type) {
 	case *regularFile:
-		stat.Mask |= linux.STATX_SIZE | linux.STATX_BLOCKS
 		stat.Size = uint64(impl.size.Load())
 		// TODO(jamieliu): This should be impl.data.Span() / 512, but this is
 		// too expensive to compute here. Cache it in regularFile.

pkg/sentry/mm/README.md

@@ -265,7 +265,7 @@ In the sentry:
     [`memmap.Mappable.AddMapping` and `memmap.Mappable.RemoveMapping`][memmap].
 
 -   Host files that may be mapped into host VMAs are represented by type
-    [`platform.File`][platform].
+    [`memmap.File`][memmap].
 
 -   Host VMAs are represented in the sentry by type [`mm.pma`][mm] ("platform
     mapping area"), stored in `mm.MemoryManager.pmas`.

pkg/sentry/mm/io.go

@@ -26,7 +26,7 @@ import (
 // There are two supported ways to copy data to/from application virtual
 // memory:
 //
-// 1. Internally-mapped copying: Determine the platform.File that backs the
+// 1. Internally-mapped copying: Determine the memmap.File that backs the
 // copied-to/from virtual address, obtain a mapping of its pages, and read or
 // write to the mapping.
 //

runsc/boot/vfs.go

@@ -704,7 +704,7 @@ func (c *containerMounter) mountSubmounts(ctx context.Context, conf *config.Conf
 	}
 
 	if err := c.mountTmp(ctx, conf, creds, mns); err != nil {
-		return fmt.Errorf(`mount submount "\tmp": %w`, err)
+		return fmt.Errorf(`mount submount "/tmp": %w`, err)
 	}
 	return nil
 }