--- /dev/null
+/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
+ * vim:expandtab:shiftwidth=8:tabstop=8:
+ *
+ * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ *
+ * Author: Nikita Danilov <nikita.danilov@sun.com>
+ *
+ * This file is part of Lustre, http://www.lustre.org.
+ *
+ * Lustre is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * Lustre is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Lustre; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+#ifndef __LUSTRE_LU_REF_H
+#define __LUSTRE_LU_REF_H
+
+#include <libcfs/list.h>
+
+/** \defgroup lu_ref lu_ref
+ *
+ * An interface to track references between objects. Mostly for debugging.
+ *
+ * Suppose there is a reference counted data-structure struct foo. To track
+ * who acquired references to instance of struct foo, add lu_ref field to it:
+ *
+ * \code
+ * struct foo {
+ * atomic_t foo_refcount;
+ * struct lu_ref foo_reference;
+ * ...
+ * };
+ * \endcode
+ *
+ * foo::foo_reference has to be initialized by calling
+ * lu_ref_init(). Typically there will be functions or macros to increment and
+ * decrement foo::foo_refcount, let's say they are foo_get(struct foo *foo)
+ * and foo_put(struct foo *foo), respectively.
+ *
+ * Whenever foo_get() is called to acquire a reference on a foo, lu_ref_add()
+ * has to be called to insert into foo::foo_reference a record, describing
+ * acquired reference. Dually, lu_ref_del() removes matching record. Typical
+ * usages are:
+ *
+ * \code
+ * struct bar *bar;
+ *
+ * // bar owns a reference to foo.
+ * bar->bar_foo = foo_get(foo);
+ * lu_ref_add(&foo->foo_reference, "bar", bar);
+ *
+ * ...
+ *
+ * // reference from bar to foo is released.
+ * lu_ref_del(&foo->foo_reference, "bar", bar);
+ * foo_put(bar->bar_foo);
+ *
+ *
+ * // current thread acquired a temporary reference to foo.
+ * foo_get(foo);
+ * lu_ref_add(&foo->reference, __FUNCTION__, cfs_current());
+ *
+ * ...
+ *
+ * // temporary reference is released.
+ * lu_ref_del(&foo->reference, __FUNCTION__, cfs_current());
+ * foo_put(foo);
+ * \endcode
+ *
+ * \e Et \e cetera. Often it makes sense to include lu_ref_add() and
+ * lu_ref_del() calls into foo_get() and foo_put(). When an instance of struct
+ * foo is destroyed, lu_ref_fini() has to be called that checks that no
+ * pending references remain. lu_ref_print() can be used to dump a list of
+ * pending references, while hunting down a leak.
+ *
+ * For objects to which a large number of references can be acquired,
+ * lu_ref_del() can become cpu consuming, as it has to scan the list of
+ * references. To work around this, remember result of lu_ref_add() (usually
+ * in the same place where pointer to struct foo is stored), and use
+ * lu_ref_del_at():
+ *
+ * \code
+ * // There is a large number of bar's for a single foo.
+ * bar->bar_foo = foo_get(foo);
+ * bar->bar_foo_ref = lu_ref_add(&foo->foo_reference, "bar", bar);
+ *
+ * ...
+ *
+ * // reference from bar to foo is released.
+ * lu_ref_del_at(&foo->foo_reference, bar->bar_foo_ref, "bar", bar);
+ * foo_put(bar->bar_foo);
+ * \endcode
+ *
+ * lu_ref interface degrades gracefully in case of memory shortages.
+ *
+ * @{
+ */
+
+#ifdef USE_LU_REF
+
+/* An incomplete type (defined locally in lu_ref.c) */
+struct lu_ref_link;
+
+/**
+ * Data-structure to keep track of references to a given object. This is used
+ * for debugging.
+ *
+ * lu_ref is embedded into an object which other entities (objects, threads,
+ * etc.) refer to.
+ */
+struct lu_ref {
+ spinlock_t lf_guard;
+ struct list_head lf_list;
+ int lf_failed;
+};
+
+void lu_ref_init(struct lu_ref *ref);
+void lu_ref_fini(struct lu_ref *ref);
+
+struct lu_ref_link *lu_ref_add (struct lu_ref *ref, const char *scope,
+ const void *source);
+struct lu_ref_link *lu_ref_add_atomic(struct lu_ref *ref, const char *scope,
+ const void *source);
+void lu_ref_del (struct lu_ref *ref, const char *scope,
+ const void *source);
+void lu_ref_set_at (struct lu_ref *ref,
+ struct lu_ref_link *link,
+ const char *scope, const void *source0,
+ const void *source1);
+void lu_ref_del_at (struct lu_ref *ref,
+ struct lu_ref_link *link,
+ const char *scope, const void *source);
+void lu_ref_print (const struct lu_ref *ref);
+#else /* !USE_LU_REF */
+
+struct lu_ref {};
+
+static inline void lu_ref_init(struct lu_ref *ref)
+{
+}
+
+static inline void lu_ref_fini(struct lu_ref *ref)
+{
+}
+
+static inline struct lu_ref_link *lu_ref_add(struct lu_ref *ref,
+ const char *scope,
+ const void *source)
+{
+ return NULL;
+}
+
+static inline struct lu_ref_link *lu_ref_add_atomic(struct lu_ref *ref,
+ const char *scope,
+ const void *source)
+{
+ return NULL;
+}
+
+static inline void lu_ref_del(struct lu_ref *ref, const char *scope,
+ const void *source)
+{
+}
+
+static inline void lu_ref_set_at(struct lu_ref *ref, struct lu_ref_link *link,
+ const char *scope, const void *source0,
+ const void *source1)
+{
+}
+
+static inline void lu_ref_del_at(struct lu_ref *ref, struct lu_ref_link *link,
+ const char *scope, const void *source)
+{
+}
+
+static inline int lu_ref_global_init(void)
+{
+ return 0;
+}
+
+static inline void lu_ref_global_fini(void)
+{
+}
+
+static inline void lu_ref_print(const struct lu_ref *ref)
+{
+}
+#endif /* USE_LU_REF */
+
+/** @} lu */
+
+#endif /* __LUSTRE_LU_REF_H */
--- /dev/null
+/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
+ * vim:expandtab:shiftwidth=8:tabstop=8:
+ *
+ * GPL HEADER START
+ *
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 only,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License version 2 for more details (a copy is included
+ * in the LICENSE file that accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; If not, see
+ * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ * GPL HEADER END
+ */
+/*
+ * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
+ * Use is subject to license terms.
+ */
+/*
+ * This file is part of Lustre, http://www.lustre.org/
+ * Lustre is a trademark of Sun Microsystems, Inc.
+ *
+ * lustre/obdclass/lu_ref.c
+ *
+ * Lustre reference.
+ *
+ * Author: Nikita Danilov <nikita.danilov@sun.com>
+ */
+
+#define DEBUG_SUBSYSTEM S_CLASS
+#ifndef EXPORT_SYMTAB
+# define EXPORT_SYMTAB
+#endif
+
+#ifdef __KERNEL__
+# include <libcfs/libcfs.h>
+#else
+# include <liblustre.h>
+#endif
+
+#include <obd.h>
+#include <obd_class.h>
+#include <obd_support.h>
+#include <lu_ref.h>
+
+#ifdef USE_LU_REF
+
+struct lu_ref_link {
+ struct lu_ref *ll_ref;
+ struct list_head ll_linkage;
+ const char *ll_scope;
+ const void *ll_source;
+};
+
+static cfs_mem_cache_t *lu_ref_link_kmem;
+
+static struct lu_kmem_descr lu_ref_caches[] = {
+ {
+ .ckd_cache = &lu_ref_link_kmem,
+ .ckd_name = "lu_ref_link_kmem",
+ .ckd_size = sizeof (struct lu_ref_link)
+ },
+ {
+ .ckd_cache = NULL
+ }
+};
+
+void lu_ref_print(const struct lu_ref *ref)
+{
+ struct lu_ref_link *link;
+
+ CERROR("lu_ref: %p %d\n", ref, ref->lf_failed);
+ list_for_each_entry(link, &ref->lf_list, ll_linkage) {
+ CERROR(" link: %s %p\n", link->ll_scope, link->ll_source);
+ }
+}
+EXPORT_SYMBOL(lu_ref_print);
+
+void lu_ref_init(struct lu_ref *ref)
+{
+ spin_lock_init(&ref->lf_guard);
+ CFS_INIT_LIST_HEAD(&ref->lf_list);
+}
+EXPORT_SYMBOL(lu_ref_init);
+
+void lu_ref_fini(struct lu_ref *ref)
+{
+ if (!list_empty(&ref->lf_list)) {
+ spin_lock(&ref->lf_guard);
+ lu_ref_print(ref);
+ spin_unlock(&ref->lf_guard);
+ }
+ LASSERT(list_empty(&ref->lf_list));
+}
+EXPORT_SYMBOL(lu_ref_fini);
+int lu_ref_global_init(void);
+
+static struct lu_ref_link *lu_ref_add_context(struct lu_ref *ref,
+ enum cfs_alloc_flags flags,
+ const char *scope,
+ const void *source)
+{
+ struct lu_ref_link *link;
+
+ /* this can be called so early in lustre initialization, that
+ * lu_ref_link_kmem slab is not yet created. */
+ lu_ref_global_init();
+
+ link = NULL;
+ if (lu_ref_link_kmem != NULL) {
+ OBD_SLAB_ALLOC(link, lu_ref_link_kmem, flags, sizeof(*link));
+ if (link != NULL) {
+ link->ll_ref = ref;
+ link->ll_scope = scope;
+ link->ll_source = source;
+ spin_lock(&ref->lf_guard);
+ list_add_tail(&link->ll_linkage, &ref->lf_list);
+ spin_unlock(&ref->lf_guard);
+ }
+ }
+
+ if (link == NULL) {
+ spin_lock(&ref->lf_guard);
+ ref->lf_failed++;
+ spin_unlock(&ref->lf_guard);
+ link = ERR_PTR(-ENOMEM);
+ }
+ return link;
+}
+
+struct lu_ref_link *lu_ref_add(struct lu_ref *ref, const char *scope,
+ const void *source)
+{
+ might_sleep();
+ return lu_ref_add_context(ref, CFS_ALLOC_STD, scope, source);
+}
+EXPORT_SYMBOL(lu_ref_add);
+
+/**
+ * Version of lu_ref_add() to be used in non-blockable contexts.
+ */
+struct lu_ref_link *lu_ref_add_atomic(struct lu_ref *ref, const char *scope,
+ const void *source)
+{
+ return lu_ref_add_context(ref, CFS_ALLOC_ATOMIC, scope, source);
+}
+EXPORT_SYMBOL(lu_ref_add_atomic);
+
+static inline int lu_ref_link_eq(const struct lu_ref_link *link,
+ const char *scope, const void *source)
+{
+ return link->ll_source == source && !strcmp(link->ll_scope, scope);
+}
+
+/**
+ * Maximal chain length seen so far.
+ */
+static unsigned lu_ref_chain_max_length = 127;
+
+/**
+ * Searches for a lu_ref_link with given [scope, source] within given lu_ref.
+ */
+static struct lu_ref_link *lu_ref_find(struct lu_ref *ref, const char *scope,
+ const void *source)
+{
+ struct lu_ref_link *link;
+ unsigned iterations;
+
+ iterations = 0;
+ list_for_each_entry(link, &ref->lf_list, ll_linkage) {
+ ++iterations;
+ if (lu_ref_link_eq(link, scope, source)) {
+ if (iterations > lu_ref_chain_max_length) {
+ CWARN("Long lu_ref chain %i \"%s\":%p\n",
+ iterations, scope, source);
+ lu_ref_chain_max_length = iterations * 3 / 2;
+ }
+ return link;
+ }
+ }
+ return NULL;
+}
+
+void lu_ref_del(struct lu_ref *ref, const char *scope, const void *source)
+{
+ struct lu_ref_link *link;
+
+ spin_lock(&ref->lf_guard);
+ link = lu_ref_find(ref, scope, source);
+ if (link != NULL) {
+ list_del(&link->ll_linkage);
+ spin_unlock(&ref->lf_guard);
+ OBD_SLAB_FREE(link, lu_ref_link_kmem, sizeof(*link));
+ } else {
+ LASSERT(ref->lf_failed > 0);
+ ref->lf_failed--;
+ spin_unlock(&ref->lf_guard);
+ }
+}
+EXPORT_SYMBOL(lu_ref_del);
+
+void lu_ref_set_at(struct lu_ref *ref, struct lu_ref_link *link,
+ const char *scope,
+ const void *source0, const void *source1)
+{
+ spin_lock(&ref->lf_guard);
+ if (link != ERR_PTR(-ENOMEM)) {
+ LASSERT(link->ll_ref == ref);
+ LASSERT(lu_ref_link_eq(link, scope, source0));
+ link->ll_source = source1;
+ } else {
+ LASSERT(ref->lf_failed > 0);
+ }
+ spin_unlock(&ref->lf_guard);
+}
+EXPORT_SYMBOL(lu_ref_set_at);
+
+void lu_ref_del_at(struct lu_ref *ref, struct lu_ref_link *link,
+ const char *scope, const void *source)
+{
+ if (link != ERR_PTR(-ENOMEM)) {
+ LASSERT(link->ll_ref == ref);
+ LASSERT(lu_ref_link_eq(link, scope, source));
+ spin_lock(&ref->lf_guard);
+ list_del(&link->ll_linkage);
+ spin_unlock(&ref->lf_guard);
+ OBD_SLAB_FREE(link, lu_ref_link_kmem, sizeof(*link));
+ } else {
+ LASSERT(ref->lf_failed > 0);
+ spin_lock(&ref->lf_guard);
+ ref->lf_failed--;
+ spin_unlock(&ref->lf_guard);
+ }
+}
+EXPORT_SYMBOL(lu_ref_del_at);
+
+static int lu_ref_initialized = 0;
+int lu_ref_global_init(void)
+{
+ int result;
+
+ if (lu_ref_initialized == 0) {
+ lu_ref_initialized = 1;
+ CDEBUG(D_CONSOLE,
+ "lu_ref tracking is enabled. Performance isn't.\n");
+ result = lu_kmem_init(lu_ref_caches);
+ } else
+ result = 0;
+ return result;
+}
+
+void lu_ref_global_fini(void)
+{
+ lu_kmem_fini(lu_ref_caches);
+}
+
+#endif /* USE_LU_REF */
git://git.whamcloud.com / fs / lustre-release.git / commitdiff