Port inotify to vfs2, with support in tmpfs.

Support in other filesystem impls is still needed. Unlike in Linux and vfs1, we
need to plumb inotify down to each filesystem implementation in order to keep
track of links/inode structures properly.

IN_EXCL_UNLINK still needs to be implemented, as well as a few inotify hooks
that are not present in either vfs1 or vfs2. Those will be addressed in
subsequent changes.

Updates #1479.

PiperOrigin-RevId: 313781995

1 files changed, 37 insertions, 3 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 7c04570f1..b4159f904 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -177,6 +177,12 @@ func (fs *filesystem) doCreateAt(rp *vfs.ResolvingPath, dir bool, create func(pa
 	if err := create(parentDir, name); err != nil {
 		return err
 	}
+
+	ev := linux.IN_CREATE
+	if dir {
+		ev |= linux.IN_ISDIR
+	}
+	parentDir.inode.watches.Notify(name, uint32(ev), 0)
 	parentDir.inode.touchCMtime()
 	return nil
 }
@@ -241,6 +247,7 @@ func (fs *filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs.
 			return syserror.EMLINK
 		}
 		d.inode.incLinksLocked()
+		d.inode.watches.Notify("", linux.IN_ATTRIB, 0)
 		parentDir.insertChildLocked(fs.newDentry(d.inode), name)
 		return nil
 	})
@@ -354,6 +361,7 @@ afterTrailingSymlink:
 		if err != nil {
 			return nil, err
 		}
+		parentDir.inode.watches.Notify(name, linux.IN_CREATE, 0)
 		parentDir.inode.touchCMtime()
 		return fd, nil
 	}
@@ -559,6 +567,8 @@ func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 		newParentDir.inode.touchCMtime()
 	}
 	renamed.inode.touchCtime()
+
+	vfs.InotifyRename(ctx, &renamed.inode.watches, &oldParentDir.inode.watches, &newParentDir.inode.watches, oldName, newName, renamed.inode.isDir())
 	return nil
 }
 
@@ -603,6 +613,7 @@ func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 		return err
 	}
 	parentDir.removeChildLocked(child)
+	parentDir.inode.watches.Notify(name, linux.IN_DELETE|linux.IN_ISDIR, 0)
 	// Remove links for child, child/., and child/..
 	child.inode.decLinksLocked()
 	child.inode.decLinksLocked()
@@ -620,7 +631,14 @@ func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts
 	if err != nil {
 		return err
 	}
-	return d.inode.setStat(ctx, rp.Credentials(), &opts.Stat)
+	if err := d.inode.setStat(ctx, rp.Credentials(), &opts.Stat); err != nil {
+		return err
+	}
+
+	if ev := vfs.InotifyEventFromStatMask(opts.Stat.Mask); ev != 0 {
+		d.InotifyWithParent(ev, 0)
+	}
+	return nil
 }
 
 // StatAt implements vfs.FilesystemImpl.StatAt.
@@ -700,6 +718,12 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	if err := vfsObj.PrepareDeleteDentry(mntns, &child.vfsd); err != nil {
 		return err
 	}
+
+	// Generate inotify events. Note that this must take place before the link
+	// count of the child is decremented, or else the watches may be dropped
+	// before these events are added.
+	vfs.InotifyRemoveChild(&child.inode.watches, &parentDir.inode.watches, name)
+
 	parentDir.removeChildLocked(child)
 	child.inode.decLinksLocked()
 	vfsObj.CommitDeleteDentry(&child.vfsd)
@@ -756,7 +780,12 @@ func (fs *filesystem) SetxattrAt(ctx context.Context, rp *vfs.ResolvingPath, opt
 	if err != nil {
 		return err
 	}
-	return d.inode.setxattr(rp.Credentials(), &opts)
+	if err := d.inode.setxattr(rp.Credentials(), &opts); err != nil {
+		return err
+	}
+
+	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	return nil
 }
 
 // RemovexattrAt implements vfs.FilesystemImpl.RemovexattrAt.
@@ -767,7 +796,12 @@ func (fs *filesystem) RemovexattrAt(ctx context.Context, rp *vfs.ResolvingPath,
 	if err != nil {
 		return err
 	}
-	return d.inode.removexattr(rp.Credentials(), name)
+	if err := d.inode.removexattr(rp.Credentials(), name); err != nil {
+		return err
+	}
+
+	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	return nil
 }
 
 // PrependPath implements vfs.FilesystemImpl.PrependPath.