/* * 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) 2005, 2010, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2012, 2021 by Delphix. All rights reserved. */ #include <sys/zfs_context.h> #include <sys/zfs_refcount.h> #ifdef ZFS_DEBUG /* * Reference count tracking is disabled by default. It's memory requirements * are reasonable, however as implemented it consumes a significant amount of * cpu time. Until its performance is improved it should be manually enabled. */ int reference_tracking_enable = B_FALSE; static uint_t reference_history = 3; /* tunable */ static kmem_cache_t *reference_cache; static kmem_cache_t *reference_history_cache; void zfs_refcount_init(void) { reference_cache = kmem_cache_create("reference_cache", sizeof (reference_t), 0, NULL, NULL, NULL, NULL, NULL, 0); reference_history_cache = kmem_cache_create("reference_history_cache", sizeof (uint64_t), 0, NULL, NULL, NULL, NULL, NULL, 0); } void zfs_refcount_fini(void) { kmem_cache_destroy(reference_cache); kmem_cache_destroy(reference_history_cache); } void zfs_refcount_create(zfs_refcount_t *rc) { mutex_init(&rc->rc_mtx, NULL, MUTEX_DEFAULT, NULL); list_create(&rc->rc_list, sizeof (reference_t), offsetof(reference_t, ref_link)); list_create(&rc->rc_removed, sizeof (reference_t), offsetof(reference_t, ref_link)); rc->rc_count = 0; rc->rc_removed_count = 0; rc->rc_tracked = reference_tracking_enable; } void zfs_refcount_create_tracked(zfs_refcount_t *rc) { zfs_refcount_create(rc); rc->rc_tracked = B_TRUE; } void zfs_refcount_create_untracked(zfs_refcount_t *rc) { zfs_refcount_create(rc); rc->rc_tracked = B_FALSE; } void zfs_refcount_destroy_many(zfs_refcount_t *rc, uint64_t number) { reference_t *ref; ASSERT3U(rc->rc_count, ==, number); while ((ref = list_head(&rc->rc_list))) { list_remove(&rc->rc_list, ref); kmem_cache_free(reference_cache, ref); } list_destroy(&rc->rc_list); while ((ref = list_head(&rc->rc_removed))) { list_remove(&rc->rc_removed, ref); kmem_cache_free(reference_history_cache, ref->ref_removed); kmem_cache_free(reference_cache, ref); } list_destroy(&rc->rc_removed); mutex_destroy(&rc->rc_mtx); } void zfs_refcount_destroy(zfs_refcount_t *rc) { zfs_refcount_destroy_many(rc, 0); } int zfs_refcount_is_zero(zfs_refcount_t *rc) { return (zfs_refcount_count(rc) == 0); } int64_t zfs_refcount_count(zfs_refcount_t *rc) { return (atomic_load_64(&rc->rc_count)); } int64_t zfs_refcount_add_many(zfs_refcount_t *rc, uint64_t number, const void *holder) { reference_t *ref = NULL; int64_t count; if (!rc->rc_tracked) { count = atomic_add_64_nv(&(rc)->rc_count, number); ASSERT3U(count, >=, number); return (count); } ref = kmem_cache_alloc(reference_cache, KM_SLEEP); ref->ref_holder = holder; ref->ref_number = number; mutex_enter(&rc->rc_mtx); list_insert_head(&rc->rc_list, ref); rc->rc_count += number; count = rc->rc_count; mutex_exit(&rc->rc_mtx); return (count); } int64_t zfs_refcount_add(zfs_refcount_t *rc, const void *holder) { return (zfs_refcount_add_many(rc, 1, holder)); } int64_t zfs_refcount_remove_many(zfs_refcount_t *rc, uint64_t number, const void *holder) { reference_t *ref; int64_t count; if (!rc->rc_tracked) { count = atomic_add_64_nv(&(rc)->rc_count, -number); ASSERT3S(count, >=, 0); return (count); } mutex_enter(&rc->rc_mtx); ASSERT3U(rc->rc_count, >=, number); for (ref = list_head(&rc->rc_list); ref; ref = list_next(&rc->rc_list, ref)) { if (ref->ref_holder == holder && ref->ref_number == number) { list_remove(&rc->rc_list, ref); if (reference_history > 0) { ref->ref_removed = kmem_cache_alloc(reference_history_cache, KM_SLEEP); list_insert_head(&rc->rc_removed, ref); rc->rc_removed_count++; if (rc->rc_removed_count > reference_history) { ref = list_tail(&rc->rc_removed); list_remove(&rc->rc_removed, ref); kmem_cache_free(reference_history_cache, ref->ref_removed); kmem_cache_free(reference_cache, ref); rc->rc_removed_count--; } } else { kmem_cache_free(reference_cache, ref); } rc->rc_count -= number; count = rc->rc_count; mutex_exit(&rc->rc_mtx); return (count); } } panic("No such hold %p on refcount %llx", holder, (u_longlong_t)(uintptr_t)rc); return (-1); } int64_t zfs_refcount_remove(zfs_refcount_t *rc, const void *holder) { return (zfs_refcount_remove_many(rc, 1, holder)); } void zfs_refcount_transfer(zfs_refcount_t *dst, zfs_refcount_t *src) { int64_t count, removed_count; list_t list, removed; list_create(&list, sizeof (reference_t), offsetof(reference_t, ref_link)); list_create(&removed, sizeof (reference_t), offsetof(reference_t, ref_link)); mutex_enter(&src->rc_mtx); count = src->rc_count; removed_count = src->rc_removed_count; src->rc_count = 0; src->rc_removed_count = 0; list_move_tail(&list, &src->rc_list); list_move_tail(&removed, &src->rc_removed); mutex_exit(&src->rc_mtx); mutex_enter(&dst->rc_mtx); dst->rc_count += count; dst->rc_removed_count += removed_count; list_move_tail(&dst->rc_list, &list); list_move_tail(&dst->rc_removed, &removed); mutex_exit(&dst->rc_mtx); list_destroy(&list); list_destroy(&removed); } void zfs_refcount_transfer_ownership_many(zfs_refcount_t *rc, uint64_t number, const void *current_holder, const void *new_holder) { reference_t *ref; boolean_t found = B_FALSE; if (!rc->rc_tracked) return; mutex_enter(&rc->rc_mtx); for (ref = list_head(&rc->rc_list); ref; ref = list_next(&rc->rc_list, ref)) { if (ref->ref_holder == current_holder && ref->ref_number == number) { ref->ref_holder = new_holder; found = B_TRUE; break; } } ASSERT(found); mutex_exit(&rc->rc_mtx); } void zfs_refcount_transfer_ownership(zfs_refcount_t *rc, const void *current_holder, const void *new_holder) { return (zfs_refcount_transfer_ownership_many(rc, 1, current_holder, new_holder)); } /* * If tracking is enabled, return true if a reference exists that matches * the "holder" tag. If tracking is disabled, then return true if a reference * might be held. */ boolean_t zfs_refcount_held(zfs_refcount_t *rc, const void *holder) { reference_t *ref; if (!rc->rc_tracked) return (zfs_refcount_count(rc) > 0); mutex_enter(&rc->rc_mtx); for (ref = list_head(&rc->rc_list); ref; ref = list_next(&rc->rc_list, ref)) { if (ref->ref_holder == holder) { mutex_exit(&rc->rc_mtx); return (B_TRUE); } } mutex_exit(&rc->rc_mtx); return (B_FALSE); } /* * If tracking is enabled, return true if a reference does not exist that * matches the "holder" tag. If tracking is disabled, always return true * since the reference might not be held. */ boolean_t zfs_refcount_not_held(zfs_refcount_t *rc, const void *holder) { reference_t *ref; if (!rc->rc_tracked) return (B_TRUE); mutex_enter(&rc->rc_mtx); for (ref = list_head(&rc->rc_list); ref; ref = list_next(&rc->rc_list, ref)) { if (ref->ref_holder == holder) { mutex_exit(&rc->rc_mtx); return (B_FALSE); } } mutex_exit(&rc->rc_mtx); return (B_TRUE); } EXPORT_SYMBOL(zfs_refcount_create); EXPORT_SYMBOL(zfs_refcount_destroy); EXPORT_SYMBOL(zfs_refcount_is_zero); EXPORT_SYMBOL(zfs_refcount_count); EXPORT_SYMBOL(zfs_refcount_add); EXPORT_SYMBOL(zfs_refcount_remove); EXPORT_SYMBOL(zfs_refcount_held); /* BEGIN CSTYLED */ ZFS_MODULE_PARAM(zfs, , reference_tracking_enable, INT, ZMOD_RW, "Track reference holders to refcount_t objects"); ZFS_MODULE_PARAM(zfs, , reference_history, UINT, ZMOD_RW, "Maximum reference holders being tracked"); /* END CSTYLED */ #endif /* ZFS_DEBUG */