Implement IN_EXCL_UNLINK inotify option in vfs2.

Limited to tmpfs. Inotify support in other filesystem implementations to
follow.

Updates #1479

PiperOrigin-RevId: 313828648

3 files changed, 20 insertions, 15 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/directory.go b/pkg/sentry/fsimpl/tmpfs/directory.go
index 8bc475f88..70387cb9c 100644
--- a/pkg/sentry/fsimpl/tmpfs/directory.go
+++ b/pkg/sentry/fsimpl/tmpfs/directory.go
@@ -79,6 +79,7 @@ func (dir *directory) removeChildLocked(child *dentry) {
 	dir.iterMu.Lock()
 	dir.childList.Remove(child)
 	dir.iterMu.Unlock()
+	child.unlinked = true
 }
 
 type directoryFD struct {
@@ -112,7 +113,7 @@ func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallba
 	dir.iterMu.Lock()
 	defer dir.iterMu.Unlock()
 
-	fd.dentry().InotifyWithParent(linux.IN_ACCESS, 0)
+	fd.dentry().InotifyWithParent(linux.IN_ACCESS, 0, vfs.PathEvent)
 	fd.inode().touchAtime(fd.vfsfd.Mount())
 
 	if fd.off == 0 {
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index b4159f904..183eb975c 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -182,7 +182,7 @@ func (fs *filesystem) doCreateAt(rp *vfs.ResolvingPath, dir bool, create func(pa
 	if dir {
 		ev |= linux.IN_ISDIR
 	}
-	parentDir.inode.watches.Notify(name, uint32(ev), 0)
+	parentDir.inode.watches.Notify(name, uint32(ev), 0, vfs.InodeEvent)
 	parentDir.inode.touchCMtime()
 	return nil
 }
@@ -247,7 +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)
+		d.inode.watches.Notify("", linux.IN_ATTRIB, 0, vfs.InodeEvent)
 		parentDir.insertChildLocked(fs.newDentry(d.inode), name)
 		return nil
 	})
@@ -361,7 +361,7 @@ afterTrailingSymlink:
 		if err != nil {
 			return nil, err
 		}
-		parentDir.inode.watches.Notify(name, linux.IN_CREATE, 0)
+		parentDir.inode.watches.Notify(name, linux.IN_CREATE, 0, vfs.PathEvent)
 		parentDir.inode.touchCMtime()
 		return fd, nil
 	}
@@ -613,7 +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)
+	parentDir.inode.watches.Notify(name, linux.IN_DELETE|linux.IN_ISDIR, 0, vfs.InodeEvent)
 	// Remove links for child, child/., and child/..
 	child.inode.decLinksLocked()
 	child.inode.decLinksLocked()
@@ -636,7 +636,7 @@ func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts
 	}
 
 	if ev := vfs.InotifyEventFromStatMask(opts.Stat.Mask); ev != 0 {
-		d.InotifyWithParent(ev, 0)
+		d.InotifyWithParent(ev, 0, vfs.InodeEvent)
 	}
 	return nil
 }
@@ -784,7 +784,7 @@ func (fs *filesystem) SetxattrAt(ctx context.Context, rp *vfs.ResolvingPath, opt
 		return err
 	}
 
-	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	d.InotifyWithParent(linux.IN_ATTRIB, 0, vfs.InodeEvent)
 	return nil
 }
 
@@ -800,7 +800,7 @@ func (fs *filesystem) RemovexattrAt(ctx context.Context, rp *vfs.ResolvingPath,
 		return err
 	}
 
-	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	d.InotifyWithParent(linux.IN_ATTRIB, 0, vfs.InodeEvent)
 	return nil
 }
 
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 1d83b6840..f0e098702 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -163,6 +163,11 @@ type dentry struct {
 	// filesystem.mu.
 	name string
 
+	// unlinked indicates whether this dentry has been unlinked from its parent.
+	// It is only set to true on an unlink operation, and never set from true to
+	// false. unlinked is protected by filesystem.mu.
+	unlinked bool
+
 	// dentryEntry (ugh) links dentries into their parent directory.childList.
 	dentryEntry
 
@@ -202,7 +207,7 @@ func (d *dentry) DecRef() {
 }
 
 // InotifyWithParent implements vfs.DentryImpl.InotifyWithParent.
-func (d *dentry) InotifyWithParent(events uint32, cookie uint32) {
+func (d *dentry) InotifyWithParent(events uint32, cookie uint32, et vfs.EventType) {
 	if d.inode.isDir() {
 		events |= linux.IN_ISDIR
 	}
@@ -211,9 +216,9 @@ func (d *dentry) InotifyWithParent(events uint32, cookie uint32) {
 	if d.parent != nil {
 		// Note that d.parent or d.name may be stale if there is a concurrent
 		// rename operation. Inotify does not provide consistency guarantees.
-		d.parent.inode.watches.Notify(d.name, events, cookie)
+		d.parent.inode.watches.NotifyWithExclusions(d.name, events, cookie, et, d.unlinked)
 	}
-	d.inode.watches.Notify("", events, cookie)
+	d.inode.watches.Notify("", events, cookie, et)
 }
 
 // Watches implements vfs.DentryImpl.Watches.
@@ -676,9 +681,8 @@ func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions)
 		return err
 	}
 
-	// Generate inotify events.
 	if ev := vfs.InotifyEventFromStatMask(opts.Stat.Mask); ev != 0 {
-		d.InotifyWithParent(ev, 0)
+		d.InotifyWithParent(ev, 0, vfs.InodeEvent)
 	}
 	return nil
 }
@@ -701,7 +705,7 @@ func (fd *fileDescription) Setxattr(ctx context.Context, opts vfs.SetxattrOption
 	}
 
 	// Generate inotify events.
-	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	d.InotifyWithParent(linux.IN_ATTRIB, 0, vfs.InodeEvent)
 	return nil
 }
 
@@ -713,7 +717,7 @@ func (fd *fileDescription) Removexattr(ctx context.Context, name string) error {
 	}
 
 	// Generate inotify events.
-	d.InotifyWithParent(linux.IN_ATTRIB, 0)
+	d.InotifyWithParent(linux.IN_ATTRIB, 0, vfs.InodeEvent)
 	return nil
 }