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, 2016 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;
54 ASSERT3U(compressed_size, <=, BPE_PAYLOAD_SIZE);
55 ASSERT(uncompressed_size == compressed_size ||
56 comp != ZIO_COMPRESS_OFF);
57 ASSERT3U(comp, >=, ZIO_COMPRESS_OFF);
58 ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
60 bzero(bp, sizeof (*bp));
61 BP_SET_EMBEDDED(bp, B_TRUE);
62 BP_SET_COMPRESS(bp, comp);
63 BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
64 BPE_SET_LSIZE(bp, uncompressed_size);
65 BPE_SET_PSIZE(bp, compressed_size);
68 * Encode the byte array into the words of the block pointer.
69 * First byte goes into low bits of first word (little endian).
71 for (int i = 0; i < compressed_size; i++) {
72 BF64_SET(w, (i % sizeof (w)) * NBBY, NBBY, data8[i]);
73 if (i % sizeof (w) == sizeof (w) - 1) {
74 /* we've reached the end of a word */
75 ASSERT3P(bp64, <, bp + 1);
78 if (!BPE_IS_PAYLOADWORD(bp, bp64))
83 /* write last partial word */
84 if (bp64 < (uint64_t *)(bp + 1))
89 * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
90 * more than BPE_PAYLOAD_SIZE bytes).
93 decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
98 const uint64_t *bp64 = (const uint64_t *)bp;
100 ASSERT(BP_IS_EMBEDDED(bp));
102 psize = BPE_GET_PSIZE(bp);
105 * Decode the words of the block pointer into the byte array.
106 * Low bits of first word are the first byte (little endian).
108 for (int i = 0; i < psize; i++) {
109 if (i % sizeof (w) == 0) {
110 /* beginning of a word */
111 ASSERT3P(bp64, <, bp + 1);
114 if (!BPE_IS_PAYLOADWORD(bp, bp64))
117 buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);
122 * Fill in the buffer with the (decompressed) payload of the embedded
123 * blkptr_t. Takes into account compression and byteorder (the payload is
124 * treated as a stream of bytes).
125 * Return 0 on success, or ENOSPC if it won't fit in the buffer.
128 decode_embedded_bp(const blkptr_t *bp, void *buf, int buflen)
132 ASSERT(BP_IS_EMBEDDED(bp));
134 lsize = BPE_GET_LSIZE(bp);
135 psize = BPE_GET_PSIZE(bp);
139 ASSERT3U(lsize, ==, buflen);
141 if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF) {
142 uint8_t dstbuf[BPE_PAYLOAD_SIZE];
143 decode_embedded_bp_compressed(bp, dstbuf);
144 VERIFY0(zio_decompress_data_buf(BP_GET_COMPRESS(bp),
145 dstbuf, buf, psize, buflen));
147 ASSERT3U(lsize, ==, psize);
148 decode_embedded_bp_compressed(bp, buf);