/*
* 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) 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 int 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);
ASSERT3U(rc->rc_count, >=, 0);
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, INT, ZMOD_RW,
"Maximum reference holders being tracked");
/* END CSTYLED */
#endif /* ZFS_DEBUG */
