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// SPDX-License-Identifier: CDDL-1.0
/*
* 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 https://opensource.org/licenses/CDDL-1.0.
* 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.
* Copyright (c) 2013, 2020 by Delphix. All rights reserved.
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/kmem.h>
#include <sys/sunddi.h>
#include <sys/zfs_ioctl.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
* simply by opening ZFS_DEV. This causes the ZFS driver to do create
* some private data for the file descriptor and 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_remove_head(&zo->zo_actions)) != NULL) {
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));
}
/*
* 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.
*/
zfs_file_t *
zfs_onexit_fd_hold(int fd, minor_t *minorp)
{
zfs_onexit_t *zo = NULL;
zfs_file_t *fp = zfs_file_get(fd);
if (fp == NULL)
return (NULL);
int error = zfsdev_getminor(fp, minorp);
if (error) {
zfs_onexit_fd_rele(fp);
return (NULL);
}
zo = zfsdev_get_state(*minorp, ZST_ONEXIT);
if (zo == NULL) {
zfs_onexit_fd_rele(fp);
return (NULL);
}
return (fp);
}
void
zfs_onexit_fd_rele(zfs_file_t *fp)
{
zfs_file_put(fp);
}
static int
zfs_onexit_minor_to_state(minor_t minor, zfs_onexit_t **zo)
{
*zo = zfsdev_get_state(minor, ZST_ONEXIT);
if (*zo == NULL)
return (SET_ERROR(EBADF));
return (0);
}
/*
* Add a callback to be invoked when the calling process exits.
*/
int
zfs_onexit_add_cb(minor_t minor, void (*func)(void *), void *data,
uintptr_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 = (uintptr_t)ap;
return (0);
}
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