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/*
* 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 "../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);
}
/**
* Initialize 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
*/
int range_lock_init(struct range_lock *lock, __u64 start, __u64 end)
{
int rc;
memset(&lock->rl_node, 0, sizeof(lock->rl_node));
if (end != LUSTRE_EOF)
end >>= PAGE_SHIFT;
rc = interval_set(&lock->rl_node, start >> PAGE_SHIFT, end);
if (rc)
return rc;
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;
return rc;
}
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
*/
static 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;
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)
{
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);
}
/**
* 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
*/
static 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;
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) {
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);
rc = -EINTR;
goto out;
}
spin_lock(&tree->rlt_lock);
}
spin_unlock(&tree->rlt_lock);
out:
return rc;
}
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