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Diffstat (limited to 'module/zfs/zfs_onexit.c')
| -rw-r--r-- | module/zfs/zfs_onexit.c | 173 |
1 files changed, 173 insertions, 0 deletions
diff --git a/module/zfs/zfs_onexit.c b/module/zfs/zfs_onexit.c new file mode 100644 index 000000000000..2a1332e715ee --- /dev/null +++ b/module/zfs/zfs_onexit.c @@ -0,0 +1,173 @@ +/* + * 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. + * 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_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)); +} + +/* + * 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) +{ + zfs_onexit_t *zo = NULL; + int error; + + error = zfsdev_getminor(fd, minorp); + if (error) { + zfs_onexit_fd_rele(fd); + return (error); + } + + zo = zfsdev_get_state(*minorp, ZST_ONEXIT); + if (zo == NULL) { + zfs_onexit_fd_rele(fd); + return (SET_ERROR(EBADF)); + } + return (0); +} + +void +zfs_onexit_fd_rele(int fd) +{ + zfs_file_put(fd); +} + +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, + 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); +} |