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Don't allow shrinking a PF_FSTRANS context

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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
This commit is contained in:
Tim Chase 2015-03-31 07:49:15 -05:00 committed by Brian Behlendorf
parent c089961110
commit ae26dd0039
2 changed files with 27 additions and 35 deletions
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56
include/sys/mutex.h
View File

@ -32,19 +32,29 @@
typedef enum {
MUTEX_DEFAULT = 0,
MUTEX_SPIN = 1,
MUTEX_ADAPTIVE = 2,
MUTEX_FSTRANS = 3,
MUTEX_ADAPTIVE = 2
} kmutex_type_t;
typedef struct {
struct mutex m_mutex;
kmutex_type_t m_type;
spinlock_t m_lock; /* used for serializing mutex_exit */
kthread_t *m_owner;
unsigned int m_saved_flags;
} kmutex_t;
#define MUTEX(mp) (&((mp)->m_mutex))
static inline void
spl_mutex_set_owner(kmutex_t *mp)
{
mp->m_owner = current;
}
static inline void
spl_mutex_clear_owner(kmutex_t *mp)
{
mp->m_owner = NULL;
}
#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
@ -60,18 +70,11 @@ typedef struct {
#define mutex_init(mp, name, type, ibc) \
{ \
static struct lock_class_key __key; \
\
ASSERT3P(mp, !=, NULL); \
ASSERT3P(ibc, ==, NULL); \
ASSERT((type == MUTEX_DEFAULT) || \
(type == MUTEX_ADAPTIVE) || \
(type == MUTEX_FSTRANS)); \
ASSERT(type == MUTEX_DEFAULT); \
\
__mutex_init(MUTEX(mp), (name) ? (#name) : (#mp), &__key); \
spin_lock_init(&(mp)->m_lock); \
(mp)->m_type = type; \
(mp)->m_owner = NULL; \
(mp)->m_saved_flags = 0; \
spl_mutex_clear_owner(mp); \
}
#undef mutex_destroy
@ -84,13 +87,8 @@ typedef struct {
({ \
int _rc_; \
\
if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) { \
(mp)->m_owner = current; \
if ((mp)->m_type == MUTEX_FSTRANS) { \
(mp)->m_saved_flags = current->flags; \
current->flags |= PF_FSTRANS; \
} \
} \
if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1) \
spl_mutex_set_owner(mp); \
\
_rc_; \
})
@ -100,22 +98,14 @@ typedef struct {
{ \
ASSERT3P(mutex_owner(mp), !=, current); \
mutex_lock_nested(MUTEX(mp), (subclass)); \
(mp)->m_owner = current; \
if ((mp)->m_type == MUTEX_FSTRANS) { \
(mp)->m_saved_flags = current->flags; \
current->flags |= PF_FSTRANS; \
} \
spl_mutex_set_owner(mp); \
}
#else /* CONFIG_DEBUG_LOCK_ALLOC */
#define mutex_enter_nested(mp, subclass) \
{ \
ASSERT3P(mutex_owner(mp), !=, current); \
mutex_lock(MUTEX(mp)); \
(mp)->m_owner = current; \
if ((mp)->m_type == MUTEX_FSTRANS) { \
(mp)->m_saved_flags = current->flags; \
current->flags |= PF_FSTRANS; \
} \
spl_mutex_set_owner(mp); \
}
#endif /* CONFIG_DEBUG_LOCK_ALLOC */
@ -143,11 +133,7 @@ typedef struct {
#define mutex_exit(mp) \
{ \
spin_lock(&(mp)->m_lock); \
if ((mp)->m_type == MUTEX_FSTRANS) { \
current->flags &= ~(PF_FSTRANS); \
current->flags |= (mp)->m_saved_flags; \
} \
(mp)->m_owner = NULL; \
spl_mutex_clear_owner(mp); \
mutex_unlock(MUTEX(mp)); \
spin_unlock(&(mp)->m_lock); \
}

6
module/spl/spl-kmem-cache.c
View File

@ -1574,6 +1574,12 @@ __spl_kmem_cache_generic_shrinker(struct shrinker *shrink,
spl_kmem_cache_t *skc;
int alloc = 0;
/*
* No shrinking in a transaction context. Can cause deadlocks.
*/
if (sc->nr_to_scan && spl_fstrans_check())
return (SHRINK_STOP);
down_read(&spl_kmem_cache_sem);
list_for_each_entry(skc, &spl_kmem_cache_list, skc_list) {
if (sc->nr_to_scan) {