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ae26dd0039
Avoid deadlocks when entering the shrinker from a PF_FSTRANS context.
This patch also reverts commit d0d5dd7 which added MUTEX_FSTRANS. Its
use has been deprecated within ZFS as it was an ineffective mechanism
to eliminate deadlocks. Among other things, it introduced the need for
strict ordering of mutex locking and unlocking in order that the
PF_FSTRANS flag wouldn't set incorrectly.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #446
145 lines
4.1 KiB
C
145 lines
4.1 KiB
C
/*
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://zfsonlinux.org/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* 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 the SPL. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _SPL_MUTEX_H
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#define _SPL_MUTEX_H
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#include <sys/types.h>
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#include <linux/mutex.h>
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#include <linux/compiler_compat.h>
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typedef enum {
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MUTEX_DEFAULT = 0,
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MUTEX_SPIN = 1,
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MUTEX_ADAPTIVE = 2
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} kmutex_type_t;
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typedef struct {
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struct mutex m_mutex;
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spinlock_t m_lock; /* used for serializing mutex_exit */
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kthread_t *m_owner;
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} kmutex_t;
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#define MUTEX(mp) (&((mp)->m_mutex))
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static inline void
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spl_mutex_set_owner(kmutex_t *mp)
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{
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mp->m_owner = current;
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}
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static inline void
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spl_mutex_clear_owner(kmutex_t *mp)
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{
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mp->m_owner = NULL;
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}
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#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
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#define mutex_owned(mp) (mutex_owner(mp) == current)
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#define MUTEX_HELD(mp) mutex_owned(mp)
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#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))
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/*
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* The following functions must be a #define and not static inline.
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* This ensures that the native linux mutex functions (lock/unlock)
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* will be correctly located in the users code which is important
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* for the built in kernel lock analysis tools
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*/
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#undef mutex_init
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#define mutex_init(mp, name, type, ibc) \
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{ \
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static struct lock_class_key __key; \
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ASSERT(type == MUTEX_DEFAULT); \
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\
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__mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
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spin_lock_init(&(mp)->m_lock); \
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spl_mutex_clear_owner(mp); \
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}
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#undef mutex_destroy
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#define mutex_destroy(mp) \
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{ \
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VERIFY3P(mutex_owner(mp), ==, NULL); \
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}
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#define mutex_tryenter(mp) \
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({ \
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int _rc_; \
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\
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if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
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spl_mutex_set_owner(mp); \
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\
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_rc_; \
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})
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define mutex_enter_nested(mp, subclass) \
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{ \
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ASSERT3P(mutex_owner(mp), !=, current); \
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mutex_lock_nested(MUTEX(mp), (subclass)); \
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spl_mutex_set_owner(mp); \
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}
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#else /* CONFIG_DEBUG_LOCK_ALLOC */
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#define mutex_enter_nested(mp, subclass) \
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{ \
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ASSERT3P(mutex_owner(mp), !=, current); \
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mutex_lock(MUTEX(mp)); \
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spl_mutex_set_owner(mp); \
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}
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#endif /* CONFIG_DEBUG_LOCK_ALLOC */
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#define mutex_enter(mp) mutex_enter_nested((mp), 0)
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/*
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* The reason for the spinlock:
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*
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* The Linux mutex is designed with a fast-path/slow-path design such that it
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* does not guarantee serialization upon itself, allowing a race where latter
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* acquirers finish mutex_unlock before former ones.
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*
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* The race renders it unsafe to be used for serializing the freeing of an
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* object in which the mutex is embedded, where the latter acquirer could go
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* on to free the object while the former one is still doing mutex_unlock and
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* causing memory corruption.
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*
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* However, there are many places in ZFS where the mutex is used for
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* serializing object freeing, and the code is shared among other OSes without
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* this issue. Thus, we need the spinlock to force the serialization on
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* mutex_exit().
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*
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* See http://lwn.net/Articles/575477/ for the information about the race.
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*/
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#define mutex_exit(mp) \
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{ \
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spin_lock(&(mp)->m_lock); \
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spl_mutex_clear_owner(mp); \
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mutex_unlock(MUTEX(mp)); \
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spin_unlock(&(mp)->m_lock); \
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}
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int spl_mutex_init(void);
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void spl_mutex_fini(void);
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#endif /* _SPL_MUTEX_H */
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