Illumos 5314 - Remove "dbuf phys" db->db_data pointer aliases in ZFS

5314 Remove "dbuf phys" db->db_data pointer aliases in ZFS
Author: Justin T. Gibbs <justing@spectralogic.com>
Reviewed by: Andriy Gapon <avg@freebsd.org>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Will Andrews <willa@spectralogic.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/5314
  illumos/illumos-gate@c137962

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

Author: Justin T. Gibbs

cmd/zdb/zdb.c

@@ -1928,8 +1928,8 @@ dump_dir(objset_t *os)
 	if (dds.dds_type == DMU_OST_META) {
 		dds.dds_creation_txg = TXG_INITIAL;
 		usedobjs = BP_GET_FILL(os->os_rootbp);
-		refdbytes = os->os_spa->spa_dsl_pool->
-		    dp_mos_dir->dd_phys->dd_used_bytes;
+		refdbytes = dsl_dir_phys(os->os_spa->spa_dsl_pool->dp_mos_dir)->
+		    dd_used_bytes;
 	} else {
 		dmu_objset_space(os, &refdbytes, &scratch, &usedobjs, &scratch);
 	}

include/sys/dbuf.h

@@ -228,7 +228,6 @@ typedef struct dmu_buf_impl {
 
 	/* stuff we store for the user (see dmu_buf_set_user) */
 	void *db_user_ptr;
-	void **db_user_data_ptr_ptr;
 	dmu_buf_evict_func_t *db_evict_func;
 
 	uint8_t db_immediate_evict;

include/sys/dmu.h

@@ -481,30 +481,23 @@ void dmu_buf_rele_array(dmu_buf_t **, int numbufs, void *tag);
  *
  * user_ptr is for use by the user and can be obtained via dmu_buf_get_user().
  *
- * user_data_ptr_ptr should be NULL, or a pointer to a pointer which
- * will be set to db->db_data when you are allowed to access it.  Note
- * that db->db_data (the pointer) can change when you do dmu_buf_read(),
- * dmu_buf_tryupgrade(), dmu_buf_will_dirty(), or dmu_buf_will_fill().
- * *user_data_ptr_ptr will be set to the new value when it changes.
- *
  * If non-NULL, pageout func will be called when this buffer is being
  * excised from the cache, so that you can clean up the data structure
  * pointed to by user_ptr.
  *
  * dmu_evict_user() will call the pageout func for all buffers in a
  * objset with a given pageout func.
  */
-void *dmu_buf_set_user(dmu_buf_t *db, void *user_ptr, void *user_data_ptr_ptr,
+void *dmu_buf_set_user(dmu_buf_t *db, void *user_ptr,
     dmu_buf_evict_func_t *pageout_func);
 /*
  * set_user_ie is the same as set_user, but request immediate eviction
  * when hold count goes to zero.
  */
 void *dmu_buf_set_user_ie(dmu_buf_t *db, void *user_ptr,
-    void *user_data_ptr_ptr, dmu_buf_evict_func_t *pageout_func);
-void *dmu_buf_update_user(dmu_buf_t *db_fake, void *old_user_ptr,
-    void *user_ptr, void *user_data_ptr_ptr,
     dmu_buf_evict_func_t *pageout_func);
+void *dmu_buf_update_user(dmu_buf_t *db_fake, void *old_user_ptr,
+    void *user_ptr, dmu_buf_evict_func_t *pageout_func);
 void dmu_evict_user(objset_t *os, dmu_buf_evict_func_t *func);
 
 /*

include/sys/dsl_dataset.h

@@ -48,7 +48,7 @@ struct dsl_pool;
 
 #define	DS_FLAG_INCONSISTENT	(1ULL<<0)
 #define	DS_IS_INCONSISTENT(ds)	\
-	((ds)->ds_phys->ds_flags & DS_FLAG_INCONSISTENT)
+	(dsl_dataset_phys(ds)->ds_flags & DS_FLAG_INCONSISTENT)
 
 /*
  * Do not allow this dataset to be promoted.
@@ -68,7 +68,7 @@ struct dsl_pool;
  */
 #define	DS_FLAG_DEFER_DESTROY	(1ULL<<3)
 #define	DS_IS_DEFER_DESTROY(ds)	\
-	((ds)->ds_phys->ds_flags & DS_FLAG_DEFER_DESTROY)
+	(dsl_dataset_phys(ds)->ds_flags & DS_FLAG_DEFER_DESTROY)
 
 /*
  * DS_FIELD_* are strings that are used in the "extensified" dataset zap object.
@@ -127,7 +127,6 @@ typedef struct dsl_dataset_phys {
 typedef struct dsl_dataset {
 	/* Immutable: */
 	struct dsl_dir *ds_dir;
-	dsl_dataset_phys_t *ds_phys;
 	dmu_buf_t *ds_dbuf;
 	uint64_t ds_object;
 	uint64_t ds_fsid_guid;
@@ -177,17 +176,26 @@ typedef struct dsl_dataset {
 	char ds_snapname[MAXNAMELEN];
 } dsl_dataset_t;
 
+static inline dsl_dataset_phys_t *
+dsl_dataset_phys(dsl_dataset_t *ds)
+{
+	return (ds->ds_dbuf->db_data);
+}
+
 /*
  * The max length of a temporary tag prefix is the number of hex digits
  * required to express UINT64_MAX plus one for the hyphen.
  */
 #define	MAX_TAG_PREFIX_LEN	17
 
-#define	dsl_dataset_is_snapshot(ds) \
-	((ds)->ds_phys->ds_num_children != 0)
+static inline boolean_t
+dsl_dataset_is_snapshot(dsl_dataset_t *ds)
+{
+	return (dsl_dataset_phys(ds)->ds_num_children != 0);
+}
 
 #define	DS_UNIQUE_IS_ACCURATE(ds)	\
-	(((ds)->ds_phys->ds_flags & DS_FLAG_UNIQUE_ACCURATE) != 0)
+	((dsl_dataset_phys(ds)->ds_flags & DS_FLAG_UNIQUE_ACCURATE) != 0)
 
 int dsl_dataset_hold(struct dsl_pool *dp, const char *name, void *tag,
     dsl_dataset_t **dsp);

include/sys/dsl_dir.h

@@ -86,10 +86,11 @@ typedef struct dsl_dir_phys {
 struct dsl_dir {
 	/* These are immutable; no lock needed: */
 	uint64_t dd_object;
-	dsl_dir_phys_t *dd_phys;
-	dmu_buf_t *dd_dbuf;
 	dsl_pool_t *dd_pool;
 
+	/* Stable until user eviction; no lock needed: */
+	dmu_buf_t *dd_dbuf;
+
 	/* protected by lock on pool's dp_dirty_dirs list */
 	txg_node_t dd_dirty_link;
 
@@ -111,6 +112,12 @@ struct dsl_dir {
 	char dd_myname[MAXNAMELEN];
 };
 
+static inline dsl_dir_phys_t *
+dsl_dir_phys(dsl_dir_t *dd)
+{
+	return (dd->dd_dbuf->db_data);
+}
+
 void dsl_dir_rele(dsl_dir_t *dd, void *tag);
 int dsl_dir_hold(dsl_pool_t *dp, const char *name, void *tag,
     dsl_dir_t **, const char **tail);

include/sys/zap_impl.h

@@ -70,7 +70,7 @@ typedef struct mzap_ent {
 } mzap_ent_t;
 
 #define	MZE_PHYS(zap, mze) \
-	(&(zap)->zap_m.zap_phys->mz_chunk[(mze)->mze_chunkid])
+	(&zap_m_phys(zap)->mz_chunk[(mze)->mze_chunkid])
 
 /*
  * The (fat) zap is stored in one object. It is an array of
@@ -104,7 +104,7 @@ struct zap_leaf;
  * word number (1<<ZAP_EMBEDDED_PTRTBL_SHIFT(zap)).
  */
 #define	ZAP_EMBEDDED_PTRTBL_ENT(zap, idx) \
-	((uint64_t *)(zap)->zap_f.zap_phys) \
+	((uint64_t *)zap_f_phys(zap)) \
 	[(idx) + (1<<ZAP_EMBEDDED_PTRTBL_SHIFT(zap))]
 
 /*
@@ -149,8 +149,6 @@ typedef struct zap {
 	uint64_t zap_salt;
 	union {
 		struct {
-			zap_phys_t *zap_phys;
-
 			/*
 			 * zap_num_entries_mtx protects
 			 * zap_num_entries
@@ -159,7 +157,6 @@ typedef struct zap {
 			int zap_block_shift;
 		} zap_fat;
 		struct {
-			mzap_phys_t *zap_phys;
 			int16_t zap_num_entries;
 			int16_t zap_num_chunks;
 			int16_t zap_alloc_next;
@@ -168,6 +165,18 @@ typedef struct zap {
 	} zap_u;
 } zap_t;
 
+static inline zap_phys_t *
+zap_f_phys(zap_t *zap)
+{
+	return (zap->zap_dbuf->db_data);
+}
+
+static inline mzap_phys_t *
+zap_m_phys(zap_t *zap)
+{
+	return (zap->zap_dbuf->db_data);
+}
+
 typedef struct zap_name {
 	zap_t *zn_zap;
 	int zn_key_intlen;

include/sys/zap_leaf.h

@@ -83,7 +83,7 @@ struct zap_stats;
  */
 #define	ZAP_LEAF_CHUNK(l, idx) \
 	((zap_leaf_chunk_t *) \
-	((l)->l_phys->l_hash + ZAP_LEAF_HASH_NUMENTRIES(l)))[idx]
+	(zap_leaf_phys(l)->l_hash + ZAP_LEAF_HASH_NUMENTRIES(l)))[idx]
 #define	ZAP_LEAF_ENTRY(l, idx) (&ZAP_LEAF_CHUNK(l, idx).l_entry)
 
 typedef enum zap_chunk_type {
@@ -156,9 +156,13 @@ typedef struct zap_leaf {
 	uint64_t l_blkid;		/* 1<<ZAP_BLOCK_SHIFT byte block off */
 	int l_bs;			/* block size shift */
 	dmu_buf_t *l_dbuf;
-	zap_leaf_phys_t *l_phys;
 } zap_leaf_t;
 
+static inline zap_leaf_phys_t *
+zap_leaf_phys(zap_leaf_t *l)
+{
+	return (l->l_dbuf->db_data);
+}
 
 typedef struct zap_entry_handle {
 	/* Set by zap_leaf and public to ZAP */

module/zfs/dbuf.c

@@ -255,11 +255,8 @@ dbuf_evict_user(dmu_buf_impl_t *db)
 	if (db->db_level != 0 || db->db_evict_func == NULL)
 		return;
 
-	if (db->db_user_data_ptr_ptr)
-		*db->db_user_data_ptr_ptr = db->db.db_data;
 	db->db_evict_func(&db->db, db->db_user_ptr);
 	db->db_user_ptr = NULL;
-	db->db_user_data_ptr_ptr = NULL;
 	db->db_evict_func = NULL;
 }
 
@@ -473,16 +470,6 @@ dbuf_verify(dmu_buf_impl_t *db)
 }
 #endif
 
-static void
-dbuf_update_data(dmu_buf_impl_t *db)
-{
-	ASSERT(MUTEX_HELD(&db->db_mtx));
-	if (db->db_level == 0 && db->db_user_data_ptr_ptr) {
-		ASSERT(!refcount_is_zero(&db->db_holds));
-		*db->db_user_data_ptr_ptr = db->db.db_data;
-	}
-}
-
 static void
 dbuf_set_data(dmu_buf_impl_t *db, arc_buf_t *buf)
 {
@@ -493,7 +480,6 @@ dbuf_set_data(dmu_buf_impl_t *db, arc_buf_t *buf)
 		db->db.db_data = buf->b_data;
 		if (!arc_released(buf))
 			arc_set_callback(buf, dbuf_do_evict, db);
-		dbuf_update_data(db);
 	} else {
 		dbuf_evict_user(db);
 		db->db.db_data = NULL;
@@ -600,7 +586,6 @@ dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 		if (bonuslen)
 			bcopy(DN_BONUS(dn->dn_phys), db->db.db_data, bonuslen);
 		DB_DNODE_EXIT(db);
-		dbuf_update_data(db);
 		db->db_state = DB_CACHED;
 		mutex_exit(&db->db_mtx);
 		return (0);
@@ -1801,7 +1786,6 @@ dbuf_create(dnode_t *dn, uint8_t level, uint64_t blkid,
 	db->db_blkptr = blkptr;
 
 	db->db_user_ptr = NULL;
-	db->db_user_data_ptr_ptr = NULL;
 	db->db_evict_func = NULL;
 	db->db_immediate_evict = 0;
 	db->db_freed_in_flight = 0;
@@ -2052,7 +2036,6 @@ __dbuf_hold_impl(struct dbuf_hold_impl_data *dh)
 	}
 
 	(void) refcount_add(&dh->dh_db->db_holds, dh->dh_tag);
-	dbuf_update_data(dh->dh_db);
 	DBUF_VERIFY(dh->dh_db);
 	mutex_exit(&dh->dh_db->db_mtx);
 
@@ -2342,27 +2325,25 @@ dbuf_refcount(dmu_buf_impl_t *db)
 }
 
 void *
-dmu_buf_set_user(dmu_buf_t *db_fake, void *user_ptr, void *user_data_ptr_ptr,
+dmu_buf_set_user(dmu_buf_t *db_fake, void *user_ptr,
     dmu_buf_evict_func_t *evict_func)
 {
-	return (dmu_buf_update_user(db_fake, NULL, user_ptr,
-	    user_data_ptr_ptr, evict_func));
+	return (dmu_buf_update_user(db_fake, NULL, user_ptr, evict_func));
 }
 
 void *
-dmu_buf_set_user_ie(dmu_buf_t *db_fake, void *user_ptr, void *user_data_ptr_ptr,
+dmu_buf_set_user_ie(dmu_buf_t *db_fake, void *user_ptr,
     dmu_buf_evict_func_t *evict_func)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 
 	db->db_immediate_evict = TRUE;
-	return (dmu_buf_update_user(db_fake, NULL, user_ptr,
-	    user_data_ptr_ptr, evict_func));
+	return (dmu_buf_update_user(db_fake, NULL, user_ptr, evict_func));
 }
 
 void *
 dmu_buf_update_user(dmu_buf_t *db_fake, void *old_user_ptr, void *user_ptr,
-    void *user_data_ptr_ptr, dmu_buf_evict_func_t *evict_func)
+    dmu_buf_evict_func_t *evict_func)
 {
 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 	ASSERT(db->db_level == 0);
@@ -2373,10 +2354,7 @@ dmu_buf_update_user(dmu_buf_t *db_fake, void *old_user_ptr, void *user_ptr,
 
 	if (db->db_user_ptr == old_user_ptr) {
 		db->db_user_ptr = user_ptr;
-		db->db_user_data_ptr_ptr = user_data_ptr_ptr;
 		db->db_evict_func = evict_func;
-
-		dbuf_update_data(db);
 	} else {
 		old_user_ptr = db->db_user_ptr;
 	}

module/zfs/dmu_diff.c

@@ -194,7 +194,7 @@ dmu_diff(const char *tosnap_name, const char *fromsnap_name,
 		return (SET_ERROR(EXDEV));
 	}
 
-	fromtxg = fromsnap->ds_phys->ds_creation_txg;
+	fromtxg = dsl_dataset_phys(fromsnap)->ds_creation_txg;
 	dsl_dataset_rele(fromsnap, FTAG);
 
 	dsl_dataset_long_hold(tosnap, FTAG);