+/*
+ * 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.gnu.org/licenses/gpl-2.0.html
+ *
+ * GPL HEADER END
+ */
+/*
+ * Range lock is used to allow multiple threads writing a single shared
+ * file given each thread is writing to a non-overlapping portion of the
+ * file.
+ *
+ * Refer to the possible upstream kernel version of range lock by
+ * Jan Kara <jack@suse.cz>: https://lkml.org/lkml/2013/1/31/480
+ *
+ * This file could later replaced by the upstream kernel version.
+ */
+/*
+ * Author: Prakash Surya <surya1@llnl.gov>
+ * Author: Bobi Jam <bobijam.xu@intel.com>
+ */
+#include "range_lock.h"
+#include <lustre/lustre_user.h>
+
+/**
+ * Initialize a range lock tree
+ *
+ * \param tree [in] an empty range lock tree
+ *
+ * Pre: Caller should have allocated the range lock tree.
+ * Post: The range lock tree is ready to function.
+ */
+void range_lock_tree_init(struct range_lock_tree *tree)
+{
+ tree->rlt_root = NULL;
+ tree->rlt_sequence = 0;
+ spin_lock_init(&tree->rlt_lock);
+}
+
+/**
+ * Intialize a range lock node
+ *
+ * \param lock [in] an empty range lock node
+ * \param start [in] start of the covering region
+ * \param end [in] end of the covering region
+ *
+ * Pre: Caller should have allocated the range lock node.
+ * Post: The range lock node is meant to cover [start, end] region
+ */
+void range_lock_init(struct range_lock *lock, __u64 start, __u64 end)
+{
+ interval_init(&lock->rl_node);
+ if (end != LUSTRE_EOF)
+ end >>= PAGE_SHIFT;
+ interval_set(&lock->rl_node, start >> PAGE_SHIFT, end);
+ INIT_LIST_HEAD(&lock->rl_next_lock);
+ lock->rl_task = NULL;
+ lock->rl_lock_count = 0;
+ lock->rl_blocking_ranges = 0;
+ lock->rl_sequence = 0;
+}
+
+static inline struct range_lock *next_lock(struct range_lock *lock)
+{
+ return list_entry(lock->rl_next_lock.next, typeof(*lock), rl_next_lock);
+}
+
+/**
+ * Helper function of range_unlock()
+ *
+ * \param node [in] a range lock found overlapped during interval node
+ * search
+ * \param arg [in] the range lock to be tested
+ *
+ * \retval INTERVAL_ITER_CONT indicate to continue the search for next
+ * overlapping range node
+ * \retval INTERVAL_ITER_STOP indicate to stop the search
+ */
+enum interval_iter range_unlock_cb(struct interval_node *node, void *arg)
+{
+ struct range_lock *lock = arg;
+ struct range_lock *overlap = node2rangelock(node);
+ struct range_lock *iter;
+ ENTRY;
+
+ list_for_each_entry(iter, &overlap->rl_next_lock, rl_next_lock) {
+ if (iter->rl_sequence > lock->rl_sequence) {
+ --iter->rl_blocking_ranges;
+ LASSERT(iter->rl_blocking_ranges > 0);
+ }
+ }
+ if (overlap->rl_sequence > lock->rl_sequence) {
+ --overlap->rl_blocking_ranges;
+ if (overlap->rl_blocking_ranges == 0)
+ wake_up_process(overlap->rl_task);
+ }
+ RETURN(INTERVAL_ITER_CONT);
+}
+
+/**
+ * Unlock a range lock, wake up locks blocked by this lock.
+ *
+ * \param tree [in] range lock tree
+ * \param lock [in] range lock to be deleted
+ *
+ * If this lock has been granted, relase it; if not, just delete it from
+ * the tree or the same region lock list. Wake up those locks only blocked
+ * by this lock through range_unlock_cb().
+ */
+void range_unlock(struct range_lock_tree *tree, struct range_lock *lock)
+{
+ ENTRY;
+
+ spin_lock(&tree->rlt_lock);
+ if (!list_empty(&lock->rl_next_lock)) {
+ struct range_lock *next;
+
+ if (interval_is_intree(&lock->rl_node)) { /* first lock */
+ /* Insert the next same range lock into the tree */
+ next = next_lock(lock);
+ next->rl_lock_count = lock->rl_lock_count - 1;
+ interval_erase(&lock->rl_node, &tree->rlt_root);
+ interval_insert(&next->rl_node, &tree->rlt_root);
+ } else {
+ /* find the first lock in tree */
+ list_for_each_entry(next, &lock->rl_next_lock,
+ rl_next_lock) {
+ if (!interval_is_intree(&next->rl_node))
+ continue;
+
+ LASSERT(next->rl_lock_count > 0);
+ next->rl_lock_count--;
+ break;
+ }
+ }
+ list_del_init(&lock->rl_next_lock);
+ } else {
+ LASSERT(interval_is_intree(&lock->rl_node));
+ interval_erase(&lock->rl_node, &tree->rlt_root);
+ }
+
+ interval_search(tree->rlt_root, &lock->rl_node.in_extent,
+ range_unlock_cb, lock);
+ spin_unlock(&tree->rlt_lock);
+
+ EXIT;
+}
+
+/**
+ * Helper function of range_lock()
+ *
+ * \param node [in] a range lock found overlapped during interval node
+ * search
+ * \param arg [in] the range lock to be tested
+ *
+ * \retval INTERVAL_ITER_CONT indicate to continue the search for next
+ * overlapping range node
+ * \retval INTERVAL_ITER_STOP indicate to stop the search
+ */
+enum interval_iter range_lock_cb(struct interval_node *node, void *arg)
+{
+ struct range_lock *lock = (struct range_lock *)arg;
+ struct range_lock *overlap = node2rangelock(node);
+
+ lock->rl_blocking_ranges += overlap->rl_lock_count + 1;
+ RETURN(INTERVAL_ITER_CONT);
+}
+
+/**
+ * Lock a region
+ *
+ * \param tree [in] range lock tree
+ * \param lock [in] range lock node containing the region span
+ *
+ * \retval 0 get the range lock
+ * \retval <0 error code while not getting the range lock
+ *
+ * If there exists overlapping range lock, the new lock will wait and
+ * retry, if later it find that it is not the chosen one to wake up,
+ * it wait again.
+ */
+int range_lock(struct range_lock_tree *tree, struct range_lock *lock)
+{
+ struct interval_node *node;
+ int rc = 0;
+ ENTRY;
+
+ spin_lock(&tree->rlt_lock);
+ /*
+ * We need to check for all conflicting intervals
+ * already in the tree.
+ */
+ interval_search(tree->rlt_root, &lock->rl_node.in_extent,
+ range_lock_cb, lock);
+ /*
+ * Insert to the tree if I am unique, otherwise I've been linked to
+ * the rl_next_lock of another lock which has the same range as mine
+ * in range_lock_cb().
+ */
+ node = interval_insert(&lock->rl_node, &tree->rlt_root);
+ if (node != NULL) {
+ struct range_lock *tmp = node2rangelock(node);
+
+ list_add_tail(&lock->rl_next_lock, &tmp->rl_next_lock);
+ tmp->rl_lock_count++;
+ }
+ lock->rl_sequence = ++tree->rlt_sequence;
+
+ while (lock->rl_blocking_ranges > 0) {
+ lock->rl_task = current;
+ __set_current_state(TASK_INTERRUPTIBLE);
+ spin_unlock(&tree->rlt_lock);
+ schedule();
+
+ if (signal_pending(current)) {
+ range_unlock(tree, lock);
+ GOTO(out, rc = -EINTR);
+ }
+ spin_lock(&tree->rlt_lock);
+ }
+ spin_unlock(&tree->rlt_lock);
+out:
+ RETURN(rc);
+}
git://git.whamcloud.com / fs / lustre-release.git / commitdiff