mirror of https://github.com/schoebel/mars
98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
/*
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* MARS Long Distance Replication Software
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*
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* This file is part of MARS project: http://schoebel.github.io/mars/
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*
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* Copyright (C) 2010-2014 Thomas Schoebel-Theuer
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* Copyright (C) 2011-2014 1&1 Internet AG
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/semaphore.h>
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#include "lamport.h"
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struct semaphore lamport_sem = __SEMAPHORE_INITIALIZER(lamport_sem, 1); // TODO: replace with spinlock if possible (first check)
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struct timespec lamport_now = {};
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void get_lamport(struct timespec *now)
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{
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int diff;
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down(&lamport_sem);
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*now = CURRENT_TIME;
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diff = timespec_compare(now, &lamport_now);
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if (diff >= 0) {
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timespec_add_ns(now, 1);
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memcpy(&lamport_now, now, sizeof(lamport_now));
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timespec_add_ns(&lamport_now, 1);
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} else {
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timespec_add_ns(&lamport_now, 1);
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memcpy(now, &lamport_now, sizeof(*now));
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}
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up(&lamport_sem);
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}
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EXPORT_SYMBOL_GPL(get_lamport);
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void set_lamport(struct timespec *old)
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{
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int diff;
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protect_timespec(old);
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down(&lamport_sem);
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diff = timespec_compare(old, &lamport_now);
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if (diff >= 0) {
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memcpy(&lamport_now, old, sizeof(lamport_now));
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timespec_add_ns(&lamport_now, 1);
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}
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up(&lamport_sem);
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}
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EXPORT_SYMBOL_GPL(set_lamport);
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/* Protect against illegal values, e.g. from currupt filesystems etc.
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*/
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int max_lamport_future = 30 * 24 * 3600;
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bool protect_timespec(struct timespec *check)
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{
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struct timespec limit = CURRENT_TIME;
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bool res = false;
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limit.tv_sec += max_lamport_future;
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if (unlikely(check->tv_sec >= limit.tv_sec)) {
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down(&lamport_sem);
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timespec_add_ns(&lamport_now, 1);
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memcpy(check, &lamport_now, sizeof(*check));
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if (unlikely(check->tv_sec > limit.tv_sec))
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max_lamport_future += check->tv_sec - limit.tv_sec;
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up(&lamport_sem);
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res = true;
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}
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return res;
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}
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