Illumos 4757, 4913

4757 ZFS embedded-data block pointers ("zero block compression")
4913 zfs release should not be subject to space checks

Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://www.illumos.org/issues/4757
  https://www.illumos.org/issues/4913
  https://github.com/illumos/illumos-gate/commit/5d7b4d4

Porting notes:

For compatibility with the fastpath code the zio_done() function
needed to be updated.  Because embedded-data block pointers do
not require DVAs to be allocated the associated vdevs will not
be marked and therefore should not be unmarked.

Ported by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2544

include/sys/dmu.h

@@ -116,6 +116,14 @@ typedef enum dmu_object_byteswap {
 	((ot) & DMU_OT_METADATA) : \
 	dmu_ot[(int)(ot)].ot_metadata)
 
+/*
+ * These object types use bp_fill != 1 for their L0 bp's. Therefore they can't
+ * have their data embedded (i.e. use a BP_IS_EMBEDDED() bp), because bp_fill
+ * is repurposed for embedded BPs.
+ */
+#define	DMU_OT_HAS_FILL(ot) \
+	((ot) == DMU_OT_DNODE || (ot) == DMU_OT_OBJSET)
+
 #define	DMU_OT_BYTESWAP(ot) (((ot) & DMU_OT_NEWTYPE) ? \
 	((ot) & DMU_OT_BYTESWAP_MASK) : \
 	dmu_ot[(int)(ot)].ot_byteswap)
@@ -391,6 +399,11 @@ void dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
 void dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
     dmu_tx_t *tx);
 
+void
+dmu_write_embedded(objset_t *os, uint64_t object, uint64_t offset,
+    void *data, uint8_t etype, uint8_t comp, int uncompressed_size,
+    int compressed_size, int byteorder, dmu_tx_t *tx);
+
 /*
  * Decide how to write a block: checksum, compression, number of copies, etc.
  */