4 * This file and its contents are supplied under the terms of the
5 * Common Development and Distribution License ("CDDL"), version 1.0.
6 * You may only use this file in accordance with the terms of version
9 * A full copy of the text of the CDDL should have accompanied this
10 * source. A copy of the CDDL is also available via the Internet at
11 * http://www.illumos.org/license/CDDL.
17 * Copyright (c) 2013 by Delphix. All rights reserved.
20 #include <sys/zfs_context.h>
22 #include <sys/zio_compress.h>
25 * Embedded-data Block Pointers
27 * Normally, block pointers point (via their DVAs) to a block which holds data.
28 * If the data that we need to store is very small, this is an inefficient
29 * use of space, because a block must be at minimum 1 sector (typically 512
30 * bytes or 4KB). Additionally, reading these small blocks tends to generate
33 * Embedded-data Block Pointers allow small pieces of data (the "payload",
34 * up to 112 bytes) to be stored in the block pointer itself, instead of
35 * being pointed to. The "Pointer" part of this name is a bit of a
36 * misnomer, as nothing is pointed to.
38 * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to
39 * be embedded in the block pointer. The logic for this is handled in
40 * the SPA, by the zio pipeline. Therefore most code outside the zio
41 * pipeline doesn't need special-cases to handle these block pointers.
43 * See spa.h for details on the exact layout of embedded block pointers.
47 encode_embedded_bp_compressed(blkptr_t *bp, void *data,
48 enum zio_compress comp, int uncompressed_size, int compressed_size)
50 uint64_t *bp64 = (uint64_t *)bp;
52 uint8_t *data8 = data;
55 ASSERT3U(compressed_size, <=, BPE_PAYLOAD_SIZE);
56 ASSERT(uncompressed_size == compressed_size ||
57 comp != ZIO_COMPRESS_OFF);
58 ASSERT3U(comp, >=, ZIO_COMPRESS_OFF);
59 ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
61 bzero(bp, sizeof (*bp));
62 BP_SET_EMBEDDED(bp, B_TRUE);
63 BP_SET_COMPRESS(bp, comp);
64 BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
65 BPE_SET_LSIZE(bp, uncompressed_size);
66 BPE_SET_PSIZE(bp, compressed_size);
69 * Encode the byte array into the words of the block pointer.
70 * First byte goes into low bits of first word (little endian).
72 for (i = 0; i < compressed_size; i++) {
73 BF64_SET(w, (i % sizeof (w)) * NBBY, NBBY, data8[i]);
74 if (i % sizeof (w) == sizeof (w) - 1) {
75 /* we've reached the end of a word */
76 ASSERT3P(bp64, <, bp + 1);
79 if (!BPE_IS_PAYLOADWORD(bp, bp64))
84 /* write last partial word */
85 if (bp64 < (uint64_t *)(bp + 1))
90 * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
91 * more than BPE_PAYLOAD_SIZE bytes).
94 decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
99 const uint64_t *bp64 = (const uint64_t *)bp;
102 ASSERT(BP_IS_EMBEDDED(bp));
104 psize = BPE_GET_PSIZE(bp);
107 * Decode the words of the block pointer into the byte array.
108 * Low bits of first word are the first byte (little endian).
110 for (i = 0; i < psize; i++) {
111 if (i % sizeof (w) == 0) {
112 /* beginning of a word */
113 ASSERT3P(bp64, <, bp + 1);
116 if (!BPE_IS_PAYLOADWORD(bp, bp64))
119 buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);