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

module/zfs/blkptr.c

@@ -0,0 +1,121 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2013 by Delphix. All rights reserved.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/zio.h>
+#include <sys/zio_compress.h>
+
+/*
+ * Embedded-data Block Pointers
+ *
+ * Normally, block pointers point (via their DVAs) to a block which holds data.
+ * If the data that we need to store is very small, this is an inefficient
+ * use of space, because a block must be at minimum 1 sector (typically 512
+ * bytes or 4KB).  Additionally, reading these small blocks tends to generate
+ * more random reads.
+ *
+ * Embedded-data Block Pointers allow small pieces of data (the "payload",
+ * up to 112 bytes) to be stored in the block pointer itself, instead of
+ * being pointed to.  The "Pointer" part of this name is a bit of a
+ * misnomer, as nothing is pointed to.
+ *
+ * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to
+ * be embedded in the block pointer.  The logic for this is handled in
+ * the SPA, by the zio pipeline.  Therefore most code outside the zio
+ * pipeline doesn't need special-cases to handle these block pointers.
+ *
+ * See spa.h for details on the exact layout of embedded block pointers.
+ */
+
+void
+encode_embedded_bp_compressed(blkptr_t *bp, void *data,
+    enum zio_compress comp, int uncompressed_size, int compressed_size)
+{
+	uint64_t *bp64 = (uint64_t *)bp;
+	uint64_t w = 0;
+	uint8_t *data8 = data;
+	int i;
+
+	ASSERT3U(compressed_size, <=, BPE_PAYLOAD_SIZE);
+	ASSERT(uncompressed_size == compressed_size ||
+	    comp != ZIO_COMPRESS_OFF);
+	ASSERT3U(comp, >=, ZIO_COMPRESS_OFF);
+	ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
+
+	bzero(bp, sizeof (*bp));
+	BP_SET_EMBEDDED(bp, B_TRUE);
+	BP_SET_COMPRESS(bp, comp);
+	BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
+	BPE_SET_LSIZE(bp, uncompressed_size);
+	BPE_SET_PSIZE(bp, compressed_size);
+
+	/*
+	 * Encode the byte array into the words of the block pointer.
+	 * First byte goes into low bits of first word (little endian).
+	 */
+	for (i = 0; i < compressed_size; i++) {
+		BF64_SET(w, (i % sizeof (w)) * NBBY, NBBY, data8[i]);
+		if (i % sizeof (w) == sizeof (w) - 1) {
+			/* we've reached the end of a word */
+			ASSERT3P(bp64, <, bp + 1);
+			*bp64 = w;
+			bp64++;
+			if (!BPE_IS_PAYLOADWORD(bp, bp64))
+				bp64++;
+			w = 0;
+		}
+	}
+	/* write last partial word */
+	if (bp64 < (uint64_t *)(bp + 1))
+		*bp64 = w;
+}
+
+/*
+ * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
+ * more than BPE_PAYLOAD_SIZE bytes).
+ */
+void
+decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
+{
+	int psize;
+	uint8_t *buf8 = buf;
+	uint64_t w = 0;
+	const uint64_t *bp64 = (const uint64_t *)bp;
+	int i;
+
+	ASSERT(BP_IS_EMBEDDED(bp));
+
+	psize = BPE_GET_PSIZE(bp);
+
+	/*
+	 * Decode the words of the block pointer into the byte array.
+	 * Low bits of first word are the first byte (little endian).
+	 */
+	for (i = 0; i < psize; i++) {
+		if (i % sizeof (w) == 0) {
+			/* beginning of a word */
+			ASSERT3P(bp64, <, bp + 1);
+			w = *bp64;
+			bp64++;
+			if (!BPE_IS_PAYLOADWORD(bp, bp64))
+				bp64++;
+		}
+		buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);
+	}
+}