1 files changed, 246 insertions, 0 deletions
diff --git a/module/zfs/zfs_onexit.c b/module/zfs/zfs_onexit.c
new file mode 100644
index 000000000..9706de2b4
--- /dev/null
+++ b/module/zfs/zfs_onexit.c
@@ -0,0 +1,246 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/errno.h>
+#include <sys/open.h>
+#include <sys/kmem.h>
+#include <sys/conf.h>
+#include <sys/ddi.h>
+#include <sys/sunddi.h>
+#include <sys/zfs_ioctl.h>
+#include <sys/mkdev.h>
+#include <sys/zfs_onexit.h>
+#include <sys/zvol.h>
+
+/*
+ * ZFS kernel routines may add/delete callback routines to be invoked
+ * upon process exit (triggered via the close operation from the /dev/zfs
+ * driver).
+ *
+ * These cleanup callbacks are intended to allow for the accumulation
+ * of kernel state across multiple ioctls.  User processes participate
+ * by opening ZFS_DEV with O_EXCL. This causes the ZFS driver to do a
+ * clone-open, generating a unique minor number. The process then passes
+ * along that file descriptor to each ioctl that might have a cleanup operation.
+ *
+ * Consumers of the onexit routines should call zfs_onexit_fd_hold() early
+ * on to validate the given fd and add a reference to its file table entry.
+ * This allows the consumer to do its work and then add a callback, knowing
+ * that zfs_onexit_add_cb() won't fail with EBADF.  When finished, consumers
+ * should call zfs_onexit_fd_rele().
+ *
+ * A simple example is zfs_ioc_recv(), where we might create an AVL tree
+ * with dataset/GUID mappings and then reuse that tree on subsequent
+ * zfs_ioc_recv() calls.
+ *
+ * On the first zfs_ioc_recv() call, dmu_recv_stream() will kmem_alloc()
+ * the AVL tree and pass it along with a callback function to
+ * zfs_onexit_add_cb(). The zfs_onexit_add_cb() routine will register the
+ * callback and return an action handle.
+ *
+ * The action handle is then passed from user space to subsequent
+ * zfs_ioc_recv() calls, so that dmu_recv_stream() can fetch its AVL tree
+ * by calling zfs_onexit_cb_data() with the device minor number and
+ * action handle.
+ *
+ * If the user process exits abnormally, the callback is invoked implicitly
+ * as part of the driver close operation.  Once the user space process is
+ * finished with the accumulated kernel state, it can also just call close(2)
+ * on the cleanup fd to trigger the cleanup callback.
+ */
+
+void
+zfs_onexit_init(zfs_onexit_t **zop)
+{
+	zfs_onexit_t *zo;
+
+	zo = *zop = kmem_zalloc(sizeof (zfs_onexit_t), KM_SLEEP);
+	mutex_init(&zo->zo_lock, NULL, MUTEX_DEFAULT, NULL);
+	list_create(&zo->zo_actions, sizeof (zfs_onexit_action_node_t),
+	    offsetof(zfs_onexit_action_node_t, za_link));
+}
+
+void
+zfs_onexit_destroy(zfs_onexit_t *zo)
+{
+	zfs_onexit_action_node_t *ap;
+
+	mutex_enter(&zo->zo_lock);
+	while ((ap = list_head(&zo->zo_actions)) != NULL) {
+		list_remove(&zo->zo_actions, ap);
+		mutex_exit(&zo->zo_lock);
+		ap->za_func(ap->za_data);
+		kmem_free(ap, sizeof (zfs_onexit_action_node_t));
+		mutex_enter(&zo->zo_lock);
+	}
+	mutex_exit(&zo->zo_lock);
+
+	list_destroy(&zo->zo_actions);
+	mutex_destroy(&zo->zo_lock);
+	kmem_free(zo, sizeof (zfs_onexit_t));
+}
+
+static int
+zfs_onexit_minor_to_state(minor_t minor, zfs_onexit_t **zo)
+{
+	*zo = zfsdev_get_soft_state(minor, ZSST_CTLDEV);
+	if (*zo == NULL)
+		return (EBADF);
+
+	return (0);
+}
+
+/*
+ * Consumers might need to operate by minor number instead of fd, since
+ * they might be running in another thread (e.g. txg_sync_thread). Callers
+ * of this function must call zfs_onexit_fd_rele() when they're finished
+ * using the minor number.
+ */
+int
+zfs_onexit_fd_hold(int fd, minor_t *minorp)
+{
+	file_t *fp;
+	zfs_onexit_t *zo;
+
+	fp = getf(fd);
+	if (fp == NULL)
+		return (EBADF);
+
+	*minorp = getminor(fp->f_vnode->v_rdev);
+	return (zfs_onexit_minor_to_state(*minorp, &zo));
+}
+
+void
+zfs_onexit_fd_rele(int fd)
+{
+	releasef(fd);
+}
+
+/*
+ * Add a callback to be invoked when the calling process exits.
+ */
+int
+zfs_onexit_add_cb(minor_t minor, void (*func)(void *), void *data,
+    uint64_t *action_handle)
+{
+	zfs_onexit_t *zo;
+	zfs_onexit_action_node_t *ap;
+	int error;
+
+	error = zfs_onexit_minor_to_state(minor, &zo);
+	if (error)
+		return (error);
+
+	ap = kmem_alloc(sizeof (zfs_onexit_action_node_t), KM_SLEEP);
+	list_link_init(&ap->za_link);
+	ap->za_func = func;
+	ap->za_data = data;
+
+	mutex_enter(&zo->zo_lock);
+	list_insert_tail(&zo->zo_actions, ap);
+	mutex_exit(&zo->zo_lock);
+	if (action_handle)
+		*action_handle = (uint64_t)(uintptr_t)ap;
+
+	return (0);
+}
+
+static zfs_onexit_action_node_t *
+zfs_onexit_find_cb(zfs_onexit_t *zo, uint64_t action_handle)
+{
+	zfs_onexit_action_node_t *match;
+	zfs_onexit_action_node_t *ap;
+	list_t *l;
+
+	ASSERT(MUTEX_HELD(&zo->zo_lock));
+
+	match = (zfs_onexit_action_node_t *)(uintptr_t)action_handle;
+	l = &zo->zo_actions;
+	for (ap = list_head(l); ap != NULL; ap = list_next(l, ap)) {
+		if (match == ap)
+			break;
+	}
+	return (ap);
+}
+
+/*
+ * Delete the callback, triggering it first if 'fire' is set.
+ */
+int
+zfs_onexit_del_cb(minor_t minor, uint64_t action_handle, boolean_t fire)
+{
+	zfs_onexit_t *zo;
+	zfs_onexit_action_node_t *ap;
+	int error;
+
+	error = zfs_onexit_minor_to_state(minor, &zo);
+	if (error)
+		return (error);
+
+	mutex_enter(&zo->zo_lock);
+	ap = zfs_onexit_find_cb(zo, action_handle);
+	if (ap != NULL) {
+		list_remove(&zo->zo_actions, ap);
+		mutex_exit(&zo->zo_lock);
+		if (fire)
+			ap->za_func(ap->za_data);
+		kmem_free(ap, sizeof (zfs_onexit_action_node_t));
+	} else {
+		mutex_exit(&zo->zo_lock);
+		error = ENOENT;
+	}
+
+	return (error);
+}
+
+/*
+ * Return the data associated with this callback.  This allows consumers
+ * of the cleanup-on-exit interfaces to stash kernel data across system
+ * calls, knowing that it will be cleaned up if the calling process exits.
+ */
+int
+zfs_onexit_cb_data(minor_t minor, uint64_t action_handle, void **data)
+{
+	zfs_onexit_t *zo;
+	zfs_onexit_action_node_t *ap;
+	int error;
+
+	*data = NULL;
+
+	error = zfs_onexit_minor_to_state(minor, &zo);
+	if (error)
+		return (error);
+
+	mutex_enter(&zo->zo_lock);
+	ap = zfs_onexit_find_cb(zo, action_handle);
+	if (ap != NULL)
+		*data = ap->za_data;
+	else
+		error = ENOENT;
+	mutex_exit(&zo->zo_lock);
+
+	return (error);
+}