Add *_by-dnode routines

Add *_by_dnode() routines for accessing objects given their
dnode_t *, this is more efficient than accessing the object by 
(objset_t *, uint64_t object).  This change converts some but
not all of the existing consumers.  As performance-sensitive
code paths are discovered they should be converted to use
these routines.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Closes #5534 
Issue #4802

include/sys/dmu.h

@@ -674,10 +674,17 @@ boolean_t dmu_buf_freeable(dmu_buf_t *);
 
 dmu_tx_t *dmu_tx_create(objset_t *os);
 void dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len);
+void dmu_tx_hold_write_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off,
+    int len);
 void dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off,
     uint64_t len);
+void dmu_tx_hold_free_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off,
+    uint64_t len);
 void dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name);
+void dmu_tx_hold_zap_by_dnode(dmu_tx_t *tx, dnode_t *dn, int add,
+    const char *name);
 void dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object);
+void dmu_tx_hold_bonus_by_dnode(dmu_tx_t *tx, dnode_t *dn);
 void dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object);
 void dmu_tx_hold_sa(dmu_tx_t *tx, struct sa_handle *hdl, boolean_t may_grow);
 void dmu_tx_hold_sa_create(dmu_tx_t *tx, int total_size);
@@ -727,8 +734,12 @@ int dmu_free_long_object(objset_t *os, uint64_t object);
 #define	DMU_READ_NO_PREFETCH	1 /* don't prefetch */
 int dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 	void *buf, uint32_t flags);
+int dmu_read_by_dnode(dnode_t *dn, uint64_t offset, uint64_t size, void *buf,
+    uint32_t flags);
 void dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 	const void *buf, dmu_tx_t *tx);
+void dmu_write_by_dnode(dnode_t *dn, uint64_t offset, uint64_t size,
+    const void *buf, dmu_tx_t *tx);
 void dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 	dmu_tx_t *tx);
 #ifdef _KERNEL

include/sys/dmu_tx.h

@@ -171,7 +171,7 @@ extern dmu_tx_t *dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg);
 dmu_tx_t *dmu_tx_create_dd(dsl_dir_t *dd);
 int dmu_tx_is_syncing(dmu_tx_t *tx);
 int dmu_tx_private_ok(dmu_tx_t *tx);
-void dmu_tx_add_new_object(dmu_tx_t *tx, objset_t *os, uint64_t object);
+void dmu_tx_add_new_object(dmu_tx_t *tx, objset_t *os, dnode_t *dn);
 void dmu_tx_willuse_space(dmu_tx_t *tx, int64_t delta);
 void dmu_tx_dirty_buf(dmu_tx_t *tx, struct dmu_buf_impl *db);
 int dmu_tx_holds(dmu_tx_t *tx, uint64_t object);

include/sys/zap.h

@@ -255,6 +255,9 @@ int zap_count_write_by_dnode(dnode_t *dn, const char *name,
 int zap_add(objset_t *ds, uint64_t zapobj, const char *key,
     int integer_size, uint64_t num_integers,
     const void *val, dmu_tx_t *tx);
+int zap_add_by_dnode(dnode_t *dn, const char *key,
+    int integer_size, uint64_t num_integers,
+    const void *val, dmu_tx_t *tx);
 int zap_add_uint64(objset_t *ds, uint64_t zapobj, const uint64_t *key,
     int key_numints, int integer_size, uint64_t num_integers,
     const void *val, dmu_tx_t *tx);
@@ -294,6 +297,7 @@ int zap_length_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 int zap_remove(objset_t *ds, uint64_t zapobj, const char *name, dmu_tx_t *tx);
 int zap_remove_norm(objset_t *ds, uint64_t zapobj, const char *name,
     matchtype_t mt, dmu_tx_t *tx);
+int zap_remove_by_dnode(dnode_t *dn, const char *name, dmu_tx_t *tx);
 int zap_remove_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
     int key_numints, dmu_tx_t *tx);