- Fix nullfs vnode reference leak in nullfs_reclaim_lowervp(). The

  null_hashget() obtains the reference on the nullfs vnode, which must
  be dropped.

- Fix a wart which existed from the introduction of the nullfs
  caching, do not unlock lower vnode in the nullfs_reclaim_lowervp().
  It should be innocent, but now it is also formally safe.  Inform the
  nullfs_reclaim() about this using the NULLV_NOUNLOCK flag set on
  nullfs inode.

- Add a callback to the upper filesystems for the lower vnode
  unlinking. When inactivating a nullfs vnode, check if the lower
  vnode was unlinked, indicated by nullfs flag NULLV_DROP or VV_NOSYNC
  on the lower vnode, and reclaim upper vnode if so.  This allows
  nullfs to purge cached vnodes for the unlinked lower vnode, avoiding
  excessive caching.

Reported by:	G??ran L??wkrantz <goran.lowkrantz@ismobile.com>
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

1 files changed, 15 insertions, 2 deletions

diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index a9c86f6..a953dae 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -608,7 +608,7 @@ typedef	int vfs_mount_t(struct mount *mp);
 typedef int vfs_sysctl_t(struct mount *mp, fsctlop_t op,
 		    struct sysctl_req *req);
 typedef void vfs_susp_clean_t(struct mount *mp);
-typedef void vfs_reclaim_lowervp_t(struct mount *mp, struct vnode *lowervp);
+typedef void vfs_notify_lowervp_t(struct mount *mp, struct vnode *lowervp);
 
 struct vfsops {
 	vfs_mount_t		*vfs_mount;
@@ -626,7 +626,8 @@ struct vfsops {
 	vfs_extattrctl_t	*vfs_extattrctl;
 	vfs_sysctl_t		*vfs_sysctl;
 	vfs_susp_clean_t	*vfs_susp_clean;
-	vfs_reclaim_lowervp_t	*vfs_reclaim_lowervp;
+	vfs_notify_lowervp_t	*vfs_reclaim_lowervp;
+	vfs_notify_lowervp_t	*vfs_unlink_lowervp;
 };
 
 vfs_statfs_t	__vfs_statfs;
@@ -747,6 +748,14 @@ vfs_statfs_t	__vfs_statfs;
 	}								\
 } while (0)
 
+#define	VFS_UNLINK_LOWERVP(MP, VP) do {					\
+	if (*(MP)->mnt_op->vfs_unlink_lowervp != NULL) {		\
+		VFS_PROLOGUE(MP);					\
+		(*(MP)->mnt_op->vfs_unlink_lowervp)((MP), (VP));	\
+		VFS_EPILOGUE(MP);					\
+	}								\
+} while (0)
+
 #define VFS_KNOTE_LOCKED(vp, hint) do					\
 {									\
 	if (((vp)->v_vflag & VV_NOKNOTE) == 0)				\
@@ -759,6 +768,9 @@ vfs_statfs_t	__vfs_statfs;
 		VN_KNOTE((vp), (hint), 0);				\
 } while (0)
 
+#define	VFS_NOTIFY_UPPER_RECLAIM	1
+#define	VFS_NOTIFY_UPPER_UNLINK		2
+
 #include <sys/module.h>
 
 /*
@@ -840,6 +852,7 @@ int	vfs_modevent(module_t, int, void *);
 void	vfs_mount_error(struct mount *, const char *, ...);
 void	vfs_mountroot(void);			/* mount our root filesystem */
 void	vfs_mountedfrom(struct mount *, const char *from);
+void	vfs_notify_upper(struct vnode *, int);
 void	vfs_oexport_conv(const struct oexport_args *oexp,
 	    struct export_args *exp);
 void	vfs_ref(struct mount *);