Add MUTEX_FSTRANS mutex type

There are regions in the ZFS code where it is desirable to be able
to be set PF_FSTRANS while a specific mutex is held.  The ZFS code
could be updated to set/clear this flag in all the correct places,
but this is undesirable for a few reasons.

1) It would require changes to a significant amount of the ZFS
   code.  This would complicate applying patches from upstream.

2) It would be easy to accidentally miss a critical region in
   the initial patch or to have an future change introduce a
   new one.

Both of these concerns can be addressed by adding a new mutex type
which is responsible for managing PF_FSTRANS, support for which was
added to the SPL in commit 9099312 - Merge branch 'kmem-rework'.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tim Chase <tim@chase2k.com>
Issue #435

diff --git a/include/sys/mutex.h b/include/sys/mutex.h
index 2e45093455fe6c2f98592716b6e6394845ae53ee..5e2b2508a9d8d675c18be6915e71669a50ed486d 100644 (file)
--- a/include/sys/mutex.h
+++ b/include/sys/mutex.h
@@ -32,29 +32,19 @@
 typedef enum {
        MUTEX_DEFAULT   = 0,
        MUTEX_SPIN      = 1,
-       MUTEX_ADAPTIVE  = 2
+       MUTEX_ADAPTIVE  = 2,
+       MUTEX_FSTRANS   = 3,
 } 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)
@@ -70,11 +60,18 @@ spl_mutex_clear_owner(kmutex_t *mp)
 #define        mutex_init(mp, name, type, ibc)                         \
 {                                                              \
        static struct lock_class_key __key;                     \
-       ASSERT(type == MUTEX_DEFAULT);                          \
+                                                               \
+       ASSERT3P(mp, !=, NULL);                                 \
+       ASSERT3P(ibc, ==, NULL);                                \
+       ASSERT((type == MUTEX_DEFAULT) ||                       \
+           (type == MUTEX_ADAPTIVE) ||                         \
+           (type == MUTEX_FSTRANS));                           \
                                                                \
        __mutex_init(MUTEX(mp), #mp, &__key);                   \
        spin_lock_init(&(mp)->m_lock);                          \
-       spl_mutex_clear_owner(mp);                              \
+       (mp)->m_type = type;                                    \
+       (mp)->m_owner = NULL;                                   \
+       (mp)->m_saved_flags = 0;                                \
 }
 
 #undef mutex_destroy
@@ -87,8 +84,13 @@ spl_mutex_clear_owner(kmutex_t *mp)
 ({                                                             \
        int _rc_;                                               \
                                                                \
-       if ((_rc_ = mutex_trylock(MUTEX(mp))) == 1)             \
-               spl_mutex_set_owner(mp);                        \
+       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;           \
+               }                                               \
+       }                                                       \
                                                                \
        _rc_;                                                   \
 })
@@ -97,7 +99,11 @@ spl_mutex_clear_owner(kmutex_t *mp)
 {                                                              \
        ASSERT3P(mutex_owner(mp), !=, current);                 \
        mutex_lock(MUTEX(mp));                                  \
-       spl_mutex_set_owner(mp);                                \
+       (mp)->m_owner = current;                                \
+       if ((mp)->m_type == MUTEX_FSTRANS) {                    \
+               (mp)->m_saved_flags = current->flags;           \
+               current->flags |= PF_FSTRANS;                   \
+       }                                                       \
 }
 
 /*
@@ -122,7 +128,11 @@ spl_mutex_clear_owner(kmutex_t *mp)
 #define        mutex_exit(mp)                                          \
 {                                                              \
        spin_lock(&(mp)->m_lock);                               \
-       spl_mutex_clear_owner(mp);                              \
+       if ((mp)->m_type == MUTEX_FSTRANS) {                    \
+               current->flags &= ~(PF_FSTRANS);                \
+               current->flags |= (mp)->m_saved_flags;          \
+       }                                                       \
+       (mp)->m_owner = NULL;                                   \
        mutex_unlock(MUTEX(mp));                                \
        spin_unlock(&(mp)->m_lock);                             \
 }

diff --git a/module/splat/splat-atomic.c b/module/splat/splat-atomic.c
index a270dc42f9b19d735297e366aca341f732a099a8..e94f42f00b15da2ea1cf7799aa6e3fd294ab1510 100644 (file)
--- a/module/splat/splat-atomic.c
+++ b/module/splat/splat-atomic.c
@@ -145,7 +145,7 @@ splat_atomic_test1(struct file *file, void *arg)
 
        ap.ap_magic = SPLAT_ATOMIC_TEST_MAGIC;
        ap.ap_file = file;
-       mutex_init(&ap.ap_lock, SPLAT_ATOMIC_TEST1_NAME, NULL, NULL);
+       mutex_init(&ap.ap_lock, SPLAT_ATOMIC_TEST1_NAME, MUTEX_DEFAULT, NULL);
        init_waitqueue_head(&ap.ap_waitq);
        ap.ap_atomic = SPLAT_ATOMIC_INIT_VALUE;
        ap.ap_atomic_exited = 0;