Move zfsdev_state_{init,destroy} to common code

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <freqlabs@FreeBSD.org>
Closes #11833

include/os/freebsd/zfs/sys/zfs_znode_impl.h

@@ -77,8 +77,6 @@ typedef struct zfs_soft_state {
 	void *zss_data;
 } zfs_soft_state_t;
 
-extern minor_t zfsdev_minor_alloc(void);
-
 /*
  * Range locking rules
  * --------------------

include/sys/zfs_ioctl.h

@@ -567,7 +567,6 @@ typedef struct zfsdev_state {
 
 extern void *zfsdev_get_state(minor_t minor, enum zfsdev_state_type which);
 extern int zfsdev_getminor(int fd, minor_t *minorp);
-extern minor_t zfsdev_minor_alloc(void);
 
 extern uint_t zfs_fsyncer_key;
 extern uint_t zfs_allow_log_key;

include/sys/zfs_ioctl_impl.h

@@ -91,6 +91,10 @@ void zfs_vfs_rele(zfsvfs_t *);
 long zfsdev_ioctl_common(uint_t, zfs_cmd_t *, int);
 int zfsdev_attach(void);
 void zfsdev_detach(void);
+void zfsdev_private_set_state(void *, zfsdev_state_t *);
+zfsdev_state_t *zfsdev_private_get_state(void *);
+int zfsdev_state_init(void *);
+void zfsdev_state_destroy(void *);
 int zfs_kmod_init(void);
 void zfs_kmod_fini(void);
 

module/os/freebsd/zfs/kmod_core.c

@@ -113,7 +113,6 @@ static int zfs__fini(void);
 static void zfs_shutdown(void *, int);
 
 static eventhandler_tag zfs_shutdown_event_tag;
-extern zfsdev_state_t *zfsdev_state_list;
 
 #define	ZFS_MIN_KSTACK_PAGES 4
 
@@ -182,66 +181,29 @@ out:
 static void
 zfsdev_close(void *data)
 {
-	zfsdev_state_t *zs = data;
-
-	ASSERT(zs != NULL);
-	ASSERT3S(zs->zs_minor, >, 0);
-
-	zfs_onexit_destroy(zs->zs_onexit);
-	zfs_zevent_destroy(zs->zs_zevent);
-	zs->zs_onexit = NULL;
-	zs->zs_zevent = NULL;
-	membar_producer();
-	zs->zs_minor = -1;
+	zfsdev_state_destroy(data);
 }
 
-static int
-zfs_ctldev_init(struct cdev *devp)
+void
+zfsdev_private_set_state(void *priv __unused, zfsdev_state_t *zs)
 {
-	boolean_t newzs = B_FALSE;
-	minor_t minor;
-	zfsdev_state_t *zs, *zsprev = NULL;
-
-	ASSERT(MUTEX_HELD(&zfsdev_state_lock));
-
-	minor = zfsdev_minor_alloc();
-	if (minor == 0)
-		return (SET_ERROR(ENXIO));
-
-	for (zs = zfsdev_state_list; zs != NULL; zs = zs->zs_next) {
-		if (zs->zs_minor == -1)
-			break;
-		zsprev = zs;
-	}
-
-	if (!zs) {
-		zs = kmem_zalloc(sizeof (zfsdev_state_t), KM_SLEEP);
-		newzs = B_TRUE;
-	}
-
 	devfs_set_cdevpriv(zs, zfsdev_close);
+}
 
-	zfs_onexit_init((zfs_onexit_t **)&zs->zs_onexit);
-	zfs_zevent_init((zfs_zevent_t **)&zs->zs_zevent);
-
-	if (newzs) {
-		zs->zs_minor = minor;
-		wmb();
-		zsprev->zs_next = zs;
-	} else {
-		wmb();
-		zs->zs_minor = minor;
-	}
-	return (0);
+zfsdev_state_t *
+zfsdev_private_get_state(void *priv)
+{
+	return (priv);
 }
 
 static int
-zfsdev_open(struct cdev *devp, int flag, int mode, struct thread *td)
+zfsdev_open(struct cdev *devp __unused, int flag __unused, int mode __unused,
+    struct thread *td __unused)
 {
 	int error;
 
 	mutex_enter(&zfsdev_state_lock);
-	error = zfs_ctldev_init(devp);
+	error = zfsdev_state_init(NULL);
 	mutex_exit(&zfsdev_state_lock);
 
 	return (error);

module/os/linux/zfs/zfs_ioctl_os.c

@@ -87,69 +87,20 @@ zfs_vfs_rele(zfsvfs_t *zfsvfs)
 	deactivate_super(zfsvfs->z_sb);
 }
 
-static int
-zfsdev_state_init(struct file *filp)
+void
+zfsdev_private_set_state(void *priv, zfsdev_state_t *zs)
 {
-	zfsdev_state_t *zs, *zsprev = NULL;
-	minor_t minor;
-	boolean_t newzs = B_FALSE;
-
-	ASSERT(MUTEX_HELD(&zfsdev_state_lock));
-
-	minor = zfsdev_minor_alloc();
-	if (minor == 0)
-		return (SET_ERROR(ENXIO));
-
-	for (zs = zfsdev_state_list; zs != NULL; zs = zs->zs_next) {
-		if (zs->zs_minor == -1)
-			break;
-		zsprev = zs;
-	}
-
-	if (!zs) {
-		zs = kmem_zalloc(sizeof (zfsdev_state_t), KM_SLEEP);
-		newzs = B_TRUE;
-	}
+	struct file *filp = priv;
 
 	filp->private_data = zs;
-
-	zfs_onexit_init((zfs_onexit_t **)&zs->zs_onexit);
-	zfs_zevent_init((zfs_zevent_t **)&zs->zs_zevent);
-
-	/*
-	 * In order to provide for lock-free concurrent read access
-	 * to the minor list in zfsdev_get_state(), new entries
-	 * must be completely written before linking them into the
-	 * list whereas existing entries are already linked; the last
-	 * operation must be updating zs_minor (from -1 to the new
-	 * value).
-	 */
-	if (newzs) {
-		zs->zs_minor = minor;
-		smp_wmb();
-		zsprev->zs_next = zs;
-	} else {
-		smp_wmb();
-		zs->zs_minor = minor;
-	}
-
-	return (0);
 }
 
-static void
-zfsdev_state_destroy(struct file *filp)
+zfsdev_state_t *
+zfsdev_private_get_state(void *priv)
 {
-	zfsdev_state_t *zs = filp->private_data;
+	struct file *filp = priv;
 
-	ASSERT(zs != NULL);
-	ASSERT3S(zs->zs_minor, >, 0);
-
-	zfs_onexit_destroy(zs->zs_onexit);
-	zfs_zevent_destroy(zs->zs_zevent);
-	zs->zs_onexit = NULL;
-	zs->zs_zevent = NULL;
-	membar_producer();
-	zs->zs_minor = -1;
+	return (filp->private_data);
 }
 
 static int

module/zfs/zfs_ioctl.c

@@ -7378,7 +7378,7 @@ zfsdev_get_state(minor_t minor, enum zfsdev_state_type which)
  * Find a free minor number.  The zfsdev_state_list is expected to
  * be short since it is only a list of currently open file handles.
  */
-minor_t
+static minor_t
 zfsdev_minor_alloc(void)
 {
 	static minor_t last_minor = 0;
@@ -7398,6 +7398,79 @@ zfsdev_minor_alloc(void)
 	return (0);
 }
 
+int
+zfsdev_state_init(void *priv)
+{
+	zfsdev_state_t *zs, *zsprev = NULL;
+	minor_t minor;
+	boolean_t newzs = B_FALSE;
+
+	ASSERT(MUTEX_HELD(&zfsdev_state_lock));
+
+	minor = zfsdev_minor_alloc();
+	if (minor == 0)
+		return (SET_ERROR(ENXIO));
+
+	for (zs = zfsdev_state_list; zs != NULL; zs = zs->zs_next) {
+		if (zs->zs_minor == -1)
+			break;
+		zsprev = zs;
+	}
+
+	if (!zs) {
+		zs = kmem_zalloc(sizeof (zfsdev_state_t), KM_SLEEP);
+		newzs = B_TRUE;
+	}
+
+	zfsdev_private_set_state(priv, zs);
+
+	zfs_onexit_init((zfs_onexit_t **)&zs->zs_onexit);
+	zfs_zevent_init((zfs_zevent_t **)&zs->zs_zevent);
+
+	/*
+	 * In order to provide for lock-free concurrent read access
+	 * to the minor list in zfsdev_get_state(), new entries
+	 * must be completely written before linking them into the
+	 * list whereas existing entries are already linked; the last
+	 * operation must be updating zs_minor (from -1 to the new
+	 * value).
+	 */
+	if (newzs) {
+		zs->zs_minor = minor;
+		membar_producer();
+		zsprev->zs_next = zs;
+	} else {
+		membar_producer();
+		zs->zs_minor = minor;
+	}
+
+	return (0);
+}
+
+void
+zfsdev_state_destroy(void *priv)
+{
+	zfsdev_state_t *zs = zfsdev_private_get_state(priv);
+
+	ASSERT(zs != NULL);
+	ASSERT3S(zs->zs_minor, >, 0);
+
+	/*
+	 * The last reference to this zfsdev file descriptor is being dropped.
+	 * We don't have to worry about lookup grabbing this state object, and
+	 * zfsdev_state_init() will not try to reuse this object until it is
+	 * invalidated by setting zs_minor to -1.  Invalidation must be done
+	 * last, with a memory barrier to ensure ordering.  This lets us avoid
+	 * taking the global zfsdev state lock around destruction.
+	 */
+	zfs_onexit_destroy(zs->zs_onexit);
+	zfs_zevent_destroy(zs->zs_zevent);
+	zs->zs_onexit = NULL;
+	zs->zs_zevent = NULL;
+	membar_producer();
+	zs->zs_minor = -1;
+}
+
 long
 zfsdev_ioctl_common(uint_t vecnum, zfs_cmd_t *zc, int flag)
 {