v4.19.13 snapshot.
diff --git a/lib/lru_cache.c b/lib/lru_cache.c
new file mode 100644
index 0000000..2b10a40
--- /dev/null
+++ b/lib/lru_cache.c
@@ -0,0 +1,688 @@
+/*
+ lru_cache.c
+
+ This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+ Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+ Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+ Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+ drbd is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ drbd 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 drbd; see the file COPYING. If not, write to
+ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/module.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/string.h> /* for memset */
+#include <linux/seq_file.h> /* for seq_printf */
+#include <linux/lru_cache.h>
+
+MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
+ "Lars Ellenberg <lars@linbit.com>");
+MODULE_DESCRIPTION("lru_cache - Track sets of hot objects");
+MODULE_LICENSE("GPL");
+
+/* this is developers aid only.
+ * it catches concurrent access (lack of locking on the users part) */
+#define PARANOIA_ENTRY() do { \
+ BUG_ON(!lc); \
+ BUG_ON(!lc->nr_elements); \
+ BUG_ON(test_and_set_bit(__LC_PARANOIA, &lc->flags)); \
+} while (0)
+
+#define RETURN(x...) do { \
+ clear_bit_unlock(__LC_PARANOIA, &lc->flags); \
+ return x ; } while (0)
+
+/* BUG() if e is not one of the elements tracked by lc */
+#define PARANOIA_LC_ELEMENT(lc, e) do { \
+ struct lru_cache *lc_ = (lc); \
+ struct lc_element *e_ = (e); \
+ unsigned i = e_->lc_index; \
+ BUG_ON(i >= lc_->nr_elements); \
+ BUG_ON(lc_->lc_element[i] != e_); } while (0)
+
+
+/* We need to atomically
+ * - try to grab the lock (set LC_LOCKED)
+ * - only if there is no pending transaction
+ * (neither LC_DIRTY nor LC_STARVING is set)
+ * Because of PARANOIA_ENTRY() above abusing lc->flags as well,
+ * it is not sufficient to just say
+ * return 0 == cmpxchg(&lc->flags, 0, LC_LOCKED);
+ */
+int lc_try_lock(struct lru_cache *lc)
+{
+ unsigned long val;
+ do {
+ val = cmpxchg(&lc->flags, 0, LC_LOCKED);
+ } while (unlikely (val == LC_PARANOIA));
+ /* Spin until no-one is inside a PARANOIA_ENTRY()/RETURN() section. */
+ return 0 == val;
+#if 0
+ /* Alternative approach, spin in case someone enters or leaves a
+ * PARANOIA_ENTRY()/RETURN() section. */
+ unsigned long old, new, val;
+ do {
+ old = lc->flags & LC_PARANOIA;
+ new = old | LC_LOCKED;
+ val = cmpxchg(&lc->flags, old, new);
+ } while (unlikely (val == (old ^ LC_PARANOIA)));
+ return old == val;
+#endif
+}
+
+/**
+ * lc_create - prepares to track objects in an active set
+ * @name: descriptive name only used in lc_seq_printf_stats and lc_seq_dump_details
+ * @max_pending_changes: maximum changes to accumulate until a transaction is required
+ * @e_count: number of elements allowed to be active simultaneously
+ * @e_size: size of the tracked objects
+ * @e_off: offset to the &struct lc_element member in a tracked object
+ *
+ * Returns a pointer to a newly initialized struct lru_cache on success,
+ * or NULL on (allocation) failure.
+ */
+struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
+ unsigned max_pending_changes,
+ unsigned e_count, size_t e_size, size_t e_off)
+{
+ struct hlist_head *slot = NULL;
+ struct lc_element **element = NULL;
+ struct lru_cache *lc;
+ struct lc_element *e;
+ unsigned cache_obj_size = kmem_cache_size(cache);
+ unsigned i;
+
+ WARN_ON(cache_obj_size < e_size);
+ if (cache_obj_size < e_size)
+ return NULL;
+
+ /* e_count too big; would probably fail the allocation below anyways.
+ * for typical use cases, e_count should be few thousand at most. */
+ if (e_count > LC_MAX_ACTIVE)
+ return NULL;
+
+ slot = kcalloc(e_count, sizeof(struct hlist_head), GFP_KERNEL);
+ if (!slot)
+ goto out_fail;
+ element = kcalloc(e_count, sizeof(struct lc_element *), GFP_KERNEL);
+ if (!element)
+ goto out_fail;
+
+ lc = kzalloc(sizeof(*lc), GFP_KERNEL);
+ if (!lc)
+ goto out_fail;
+
+ INIT_LIST_HEAD(&lc->in_use);
+ INIT_LIST_HEAD(&lc->lru);
+ INIT_LIST_HEAD(&lc->free);
+ INIT_LIST_HEAD(&lc->to_be_changed);
+
+ lc->name = name;
+ lc->element_size = e_size;
+ lc->element_off = e_off;
+ lc->nr_elements = e_count;
+ lc->max_pending_changes = max_pending_changes;
+ lc->lc_cache = cache;
+ lc->lc_element = element;
+ lc->lc_slot = slot;
+
+ /* preallocate all objects */
+ for (i = 0; i < e_count; i++) {
+ void *p = kmem_cache_alloc(cache, GFP_KERNEL);
+ if (!p)
+ break;
+ memset(p, 0, lc->element_size);
+ e = p + e_off;
+ e->lc_index = i;
+ e->lc_number = LC_FREE;
+ e->lc_new_number = LC_FREE;
+ list_add(&e->list, &lc->free);
+ element[i] = e;
+ }
+ if (i == e_count)
+ return lc;
+
+ /* else: could not allocate all elements, give up */
+ for (i--; i; i--) {
+ void *p = element[i];
+ kmem_cache_free(cache, p - e_off);
+ }
+ kfree(lc);
+out_fail:
+ kfree(element);
+ kfree(slot);
+ return NULL;
+}
+
+static void lc_free_by_index(struct lru_cache *lc, unsigned i)
+{
+ void *p = lc->lc_element[i];
+ WARN_ON(!p);
+ if (p) {
+ p -= lc->element_off;
+ kmem_cache_free(lc->lc_cache, p);
+ }
+}
+
+/**
+ * lc_destroy - frees memory allocated by lc_create()
+ * @lc: the lru cache to destroy
+ */
+void lc_destroy(struct lru_cache *lc)
+{
+ unsigned i;
+ if (!lc)
+ return;
+ for (i = 0; i < lc->nr_elements; i++)
+ lc_free_by_index(lc, i);
+ kfree(lc->lc_element);
+ kfree(lc->lc_slot);
+ kfree(lc);
+}
+
+/**
+ * lc_reset - does a full reset for @lc and the hash table slots.
+ * @lc: the lru cache to operate on
+ *
+ * It is roughly the equivalent of re-allocating a fresh lru_cache object,
+ * basically a short cut to lc_destroy(lc); lc = lc_create(...);
+ */
+void lc_reset(struct lru_cache *lc)
+{
+ unsigned i;
+
+ INIT_LIST_HEAD(&lc->in_use);
+ INIT_LIST_HEAD(&lc->lru);
+ INIT_LIST_HEAD(&lc->free);
+ INIT_LIST_HEAD(&lc->to_be_changed);
+ lc->used = 0;
+ lc->hits = 0;
+ lc->misses = 0;
+ lc->starving = 0;
+ lc->locked = 0;
+ lc->changed = 0;
+ lc->pending_changes = 0;
+ lc->flags = 0;
+ memset(lc->lc_slot, 0, sizeof(struct hlist_head) * lc->nr_elements);
+
+ for (i = 0; i < lc->nr_elements; i++) {
+ struct lc_element *e = lc->lc_element[i];
+ void *p = e;
+ p -= lc->element_off;
+ memset(p, 0, lc->element_size);
+ /* re-init it */
+ e->lc_index = i;
+ e->lc_number = LC_FREE;
+ e->lc_new_number = LC_FREE;
+ list_add(&e->list, &lc->free);
+ }
+}
+
+/**
+ * lc_seq_printf_stats - print stats about @lc into @seq
+ * @seq: the seq_file to print into
+ * @lc: the lru cache to print statistics of
+ */
+void lc_seq_printf_stats(struct seq_file *seq, struct lru_cache *lc)
+{
+ /* NOTE:
+ * total calls to lc_get are
+ * (starving + hits + misses)
+ * misses include "locked" count (update from an other thread in
+ * progress) and "changed", when this in fact lead to an successful
+ * update of the cache.
+ */
+ seq_printf(seq, "\t%s: used:%u/%u hits:%lu misses:%lu starving:%lu locked:%lu changed:%lu\n",
+ lc->name, lc->used, lc->nr_elements,
+ lc->hits, lc->misses, lc->starving, lc->locked, lc->changed);
+}
+
+static struct hlist_head *lc_hash_slot(struct lru_cache *lc, unsigned int enr)
+{
+ return lc->lc_slot + (enr % lc->nr_elements);
+}
+
+
+static struct lc_element *__lc_find(struct lru_cache *lc, unsigned int enr,
+ bool include_changing)
+{
+ struct lc_element *e;
+
+ BUG_ON(!lc);
+ BUG_ON(!lc->nr_elements);
+ hlist_for_each_entry(e, lc_hash_slot(lc, enr), colision) {
+ /* "about to be changed" elements, pending transaction commit,
+ * are hashed by their "new number". "Normal" elements have
+ * lc_number == lc_new_number. */
+ if (e->lc_new_number != enr)
+ continue;
+ if (e->lc_new_number == e->lc_number || include_changing)
+ return e;
+ break;
+ }
+ return NULL;
+}
+
+/**
+ * lc_find - find element by label, if present in the hash table
+ * @lc: The lru_cache object
+ * @enr: element number
+ *
+ * Returns the pointer to an element, if the element with the requested
+ * "label" or element number is present in the hash table,
+ * or NULL if not found. Does not change the refcnt.
+ * Ignores elements that are "about to be used", i.e. not yet in the active
+ * set, but still pending transaction commit.
+ */
+struct lc_element *lc_find(struct lru_cache *lc, unsigned int enr)
+{
+ return __lc_find(lc, enr, 0);
+}
+
+/**
+ * lc_is_used - find element by label
+ * @lc: The lru_cache object
+ * @enr: element number
+ *
+ * Returns true, if the element with the requested "label" or element number is
+ * present in the hash table, and is used (refcnt > 0).
+ * Also finds elements that are not _currently_ used but only "about to be
+ * used", i.e. on the "to_be_changed" list, pending transaction commit.
+ */
+bool lc_is_used(struct lru_cache *lc, unsigned int enr)
+{
+ struct lc_element *e = __lc_find(lc, enr, 1);
+ return e && e->refcnt;
+}
+
+/**
+ * lc_del - removes an element from the cache
+ * @lc: The lru_cache object
+ * @e: The element to remove
+ *
+ * @e must be unused (refcnt == 0). Moves @e from "lru" to "free" list,
+ * sets @e->enr to %LC_FREE.
+ */
+void lc_del(struct lru_cache *lc, struct lc_element *e)
+{
+ PARANOIA_ENTRY();
+ PARANOIA_LC_ELEMENT(lc, e);
+ BUG_ON(e->refcnt);
+
+ e->lc_number = e->lc_new_number = LC_FREE;
+ hlist_del_init(&e->colision);
+ list_move(&e->list, &lc->free);
+ RETURN();
+}
+
+static struct lc_element *lc_prepare_for_change(struct lru_cache *lc, unsigned new_number)
+{
+ struct list_head *n;
+ struct lc_element *e;
+
+ if (!list_empty(&lc->free))
+ n = lc->free.next;
+ else if (!list_empty(&lc->lru))
+ n = lc->lru.prev;
+ else
+ return NULL;
+
+ e = list_entry(n, struct lc_element, list);
+ PARANOIA_LC_ELEMENT(lc, e);
+
+ e->lc_new_number = new_number;
+ if (!hlist_unhashed(&e->colision))
+ __hlist_del(&e->colision);
+ hlist_add_head(&e->colision, lc_hash_slot(lc, new_number));
+ list_move(&e->list, &lc->to_be_changed);
+
+ return e;
+}
+
+static int lc_unused_element_available(struct lru_cache *lc)
+{
+ if (!list_empty(&lc->free))
+ return 1; /* something on the free list */
+ if (!list_empty(&lc->lru))
+ return 1; /* something to evict */
+
+ return 0;
+}
+
+/* used as internal flags to __lc_get */
+enum {
+ LC_GET_MAY_CHANGE = 1,
+ LC_GET_MAY_USE_UNCOMMITTED = 2,
+};
+
+static struct lc_element *__lc_get(struct lru_cache *lc, unsigned int enr, unsigned int flags)
+{
+ struct lc_element *e;
+
+ PARANOIA_ENTRY();
+ if (lc->flags & LC_STARVING) {
+ ++lc->starving;
+ RETURN(NULL);
+ }
+
+ e = __lc_find(lc, enr, 1);
+ /* if lc_new_number != lc_number,
+ * this enr is currently being pulled in already,
+ * and will be available once the pending transaction
+ * has been committed. */
+ if (e) {
+ if (e->lc_new_number != e->lc_number) {
+ /* It has been found above, but on the "to_be_changed"
+ * list, not yet committed. Don't pull it in twice,
+ * wait for the transaction, then try again...
+ */
+ if (!(flags & LC_GET_MAY_USE_UNCOMMITTED))
+ RETURN(NULL);
+ /* ... unless the caller is aware of the implications,
+ * probably preparing a cumulative transaction. */
+ ++e->refcnt;
+ ++lc->hits;
+ RETURN(e);
+ }
+ /* else: lc_new_number == lc_number; a real hit. */
+ ++lc->hits;
+ if (e->refcnt++ == 0)
+ lc->used++;
+ list_move(&e->list, &lc->in_use); /* Not evictable... */
+ RETURN(e);
+ }
+ /* e == NULL */
+
+ ++lc->misses;
+ if (!(flags & LC_GET_MAY_CHANGE))
+ RETURN(NULL);
+
+ /* To avoid races with lc_try_lock(), first, mark us dirty
+ * (using test_and_set_bit, as it implies memory barriers), ... */
+ test_and_set_bit(__LC_DIRTY, &lc->flags);
+
+ /* ... only then check if it is locked anyways. If lc_unlock clears
+ * the dirty bit again, that's not a problem, we will come here again.
+ */
+ if (test_bit(__LC_LOCKED, &lc->flags)) {
+ ++lc->locked;
+ RETURN(NULL);
+ }
+
+ /* In case there is nothing available and we can not kick out
+ * the LRU element, we have to wait ...
+ */
+ if (!lc_unused_element_available(lc)) {
+ __set_bit(__LC_STARVING, &lc->flags);
+ RETURN(NULL);
+ }
+
+ /* It was not present in the active set. We are going to recycle an
+ * unused (or even "free") element, but we won't accumulate more than
+ * max_pending_changes changes. */
+ if (lc->pending_changes >= lc->max_pending_changes)
+ RETURN(NULL);
+
+ e = lc_prepare_for_change(lc, enr);
+ BUG_ON(!e);
+
+ clear_bit(__LC_STARVING, &lc->flags);
+ BUG_ON(++e->refcnt != 1);
+ lc->used++;
+ lc->pending_changes++;
+
+ RETURN(e);
+}
+
+/**
+ * lc_get - get element by label, maybe change the active set
+ * @lc: the lru cache to operate on
+ * @enr: the label to look up
+ *
+ * Finds an element in the cache, increases its usage count,
+ * "touches" and returns it.
+ *
+ * In case the requested number is not present, it needs to be added to the
+ * cache. Therefore it is possible that an other element becomes evicted from
+ * the cache. In either case, the user is notified so he is able to e.g. keep
+ * a persistent log of the cache changes, and therefore the objects in use.
+ *
+ * Return values:
+ * NULL
+ * The cache was marked %LC_STARVING,
+ * or the requested label was not in the active set
+ * and a changing transaction is still pending (@lc was marked %LC_DIRTY).
+ * Or no unused or free element could be recycled (@lc will be marked as
+ * %LC_STARVING, blocking further lc_get() operations).
+ *
+ * pointer to the element with the REQUESTED element number.
+ * In this case, it can be used right away
+ *
+ * pointer to an UNUSED element with some different element number,
+ * where that different number may also be %LC_FREE.
+ *
+ * In this case, the cache is marked %LC_DIRTY,
+ * so lc_try_lock() will no longer succeed.
+ * The returned element pointer is moved to the "to_be_changed" list,
+ * and registered with the new element number on the hash collision chains,
+ * so it is possible to pick it up from lc_is_used().
+ * Up to "max_pending_changes" (see lc_create()) can be accumulated.
+ * The user now should do whatever housekeeping is necessary,
+ * typically serialize on lc_try_lock_for_transaction(), then call
+ * lc_committed(lc) and lc_unlock(), to finish the change.
+ *
+ * NOTE: The user needs to check the lc_number on EACH use, so he recognizes
+ * any cache set change.
+ */
+struct lc_element *lc_get(struct lru_cache *lc, unsigned int enr)
+{
+ return __lc_get(lc, enr, LC_GET_MAY_CHANGE);
+}
+
+/**
+ * lc_get_cumulative - like lc_get; also finds to-be-changed elements
+ * @lc: the lru cache to operate on
+ * @enr: the label to look up
+ *
+ * Unlike lc_get this also returns the element for @enr, if it is belonging to
+ * a pending transaction, so the return values are like for lc_get(),
+ * plus:
+ *
+ * pointer to an element already on the "to_be_changed" list.
+ * In this case, the cache was already marked %LC_DIRTY.
+ *
+ * Caller needs to make sure that the pending transaction is completed,
+ * before proceeding to actually use this element.
+ */
+struct lc_element *lc_get_cumulative(struct lru_cache *lc, unsigned int enr)
+{
+ return __lc_get(lc, enr, LC_GET_MAY_CHANGE|LC_GET_MAY_USE_UNCOMMITTED);
+}
+
+/**
+ * lc_try_get - get element by label, if present; do not change the active set
+ * @lc: the lru cache to operate on
+ * @enr: the label to look up
+ *
+ * Finds an element in the cache, increases its usage count,
+ * "touches" and returns it.
+ *
+ * Return values:
+ * NULL
+ * The cache was marked %LC_STARVING,
+ * or the requested label was not in the active set
+ *
+ * pointer to the element with the REQUESTED element number.
+ * In this case, it can be used right away
+ */
+struct lc_element *lc_try_get(struct lru_cache *lc, unsigned int enr)
+{
+ return __lc_get(lc, enr, 0);
+}
+
+/**
+ * lc_committed - tell @lc that pending changes have been recorded
+ * @lc: the lru cache to operate on
+ *
+ * User is expected to serialize on explicit lc_try_lock_for_transaction()
+ * before the transaction is started, and later needs to lc_unlock() explicitly
+ * as well.
+ */
+void lc_committed(struct lru_cache *lc)
+{
+ struct lc_element *e, *tmp;
+
+ PARANOIA_ENTRY();
+ list_for_each_entry_safe(e, tmp, &lc->to_be_changed, list) {
+ /* count number of changes, not number of transactions */
+ ++lc->changed;
+ e->lc_number = e->lc_new_number;
+ list_move(&e->list, &lc->in_use);
+ }
+ lc->pending_changes = 0;
+ RETURN();
+}
+
+
+/**
+ * lc_put - give up refcnt of @e
+ * @lc: the lru cache to operate on
+ * @e: the element to put
+ *
+ * If refcnt reaches zero, the element is moved to the lru list,
+ * and a %LC_STARVING (if set) is cleared.
+ * Returns the new (post-decrement) refcnt.
+ */
+unsigned int lc_put(struct lru_cache *lc, struct lc_element *e)
+{
+ PARANOIA_ENTRY();
+ PARANOIA_LC_ELEMENT(lc, e);
+ BUG_ON(e->refcnt == 0);
+ BUG_ON(e->lc_number != e->lc_new_number);
+ if (--e->refcnt == 0) {
+ /* move it to the front of LRU. */
+ list_move(&e->list, &lc->lru);
+ lc->used--;
+ clear_bit_unlock(__LC_STARVING, &lc->flags);
+ }
+ RETURN(e->refcnt);
+}
+
+/**
+ * lc_element_by_index
+ * @lc: the lru cache to operate on
+ * @i: the index of the element to return
+ */
+struct lc_element *lc_element_by_index(struct lru_cache *lc, unsigned i)
+{
+ BUG_ON(i >= lc->nr_elements);
+ BUG_ON(lc->lc_element[i] == NULL);
+ BUG_ON(lc->lc_element[i]->lc_index != i);
+ return lc->lc_element[i];
+}
+
+/**
+ * lc_index_of
+ * @lc: the lru cache to operate on
+ * @e: the element to query for its index position in lc->element
+ */
+unsigned int lc_index_of(struct lru_cache *lc, struct lc_element *e)
+{
+ PARANOIA_LC_ELEMENT(lc, e);
+ return e->lc_index;
+}
+
+/**
+ * lc_set - associate index with label
+ * @lc: the lru cache to operate on
+ * @enr: the label to set
+ * @index: the element index to associate label with.
+ *
+ * Used to initialize the active set to some previously recorded state.
+ */
+void lc_set(struct lru_cache *lc, unsigned int enr, int index)
+{
+ struct lc_element *e;
+ struct list_head *lh;
+
+ if (index < 0 || index >= lc->nr_elements)
+ return;
+
+ e = lc_element_by_index(lc, index);
+ BUG_ON(e->lc_number != e->lc_new_number);
+ BUG_ON(e->refcnt != 0);
+
+ e->lc_number = e->lc_new_number = enr;
+ hlist_del_init(&e->colision);
+ if (enr == LC_FREE)
+ lh = &lc->free;
+ else {
+ hlist_add_head(&e->colision, lc_hash_slot(lc, enr));
+ lh = &lc->lru;
+ }
+ list_move(&e->list, lh);
+}
+
+/**
+ * lc_dump - Dump a complete LRU cache to seq in textual form.
+ * @lc: the lru cache to operate on
+ * @seq: the &struct seq_file pointer to seq_printf into
+ * @utext: user supplied additional "heading" or other info
+ * @detail: function pointer the user may provide to dump further details
+ * of the object the lc_element is embedded in. May be NULL.
+ * Note: a leading space ' ' and trailing newline '\n' is implied.
+ */
+void lc_seq_dump_details(struct seq_file *seq, struct lru_cache *lc, char *utext,
+ void (*detail) (struct seq_file *, struct lc_element *))
+{
+ unsigned int nr_elements = lc->nr_elements;
+ struct lc_element *e;
+ int i;
+
+ seq_printf(seq, "\tnn: lc_number (new nr) refcnt %s\n ", utext);
+ for (i = 0; i < nr_elements; i++) {
+ e = lc_element_by_index(lc, i);
+ if (e->lc_number != e->lc_new_number)
+ seq_printf(seq, "\t%5d: %6d %8d %6d ",
+ i, e->lc_number, e->lc_new_number, e->refcnt);
+ else
+ seq_printf(seq, "\t%5d: %6d %-8s %6d ",
+ i, e->lc_number, "-\"-", e->refcnt);
+ if (detail)
+ detail(seq, e);
+ seq_putc(seq, '\n');
+ }
+}
+
+EXPORT_SYMBOL(lc_create);
+EXPORT_SYMBOL(lc_reset);
+EXPORT_SYMBOL(lc_destroy);
+EXPORT_SYMBOL(lc_set);
+EXPORT_SYMBOL(lc_del);
+EXPORT_SYMBOL(lc_try_get);
+EXPORT_SYMBOL(lc_find);
+EXPORT_SYMBOL(lc_get);
+EXPORT_SYMBOL(lc_put);
+EXPORT_SYMBOL(lc_committed);
+EXPORT_SYMBOL(lc_element_by_index);
+EXPORT_SYMBOL(lc_index_of);
+EXPORT_SYMBOL(lc_seq_printf_stats);
+EXPORT_SYMBOL(lc_seq_dump_details);
+EXPORT_SYMBOL(lc_try_lock);
+EXPORT_SYMBOL(lc_is_used);
+EXPORT_SYMBOL(lc_get_cumulative);