1 /*
2 * CDDL HEADER START
3 *
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
7 * 1.0 of the CDDL.
8 *
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.
12 *
13 * CDDL HEADER END
14 */
15
16 /*
17 * Copyright (c) 2013, 2016 by Delphix. All rights reserved.
18 */
19
20 #include <sys/blkptr.h>
21 #include <sys/zfs_context.h>
22 #include <sys/zio.h>
23 #include <sys/zio_compress.h>
24
25 /*
26 * Embedded-data Block Pointers
27 *
28 * Normally, block pointers point (via their DVAs) to a block which holds data.
29 * If the data that we need to store is very small, this is an inefficient
30 * use of space, because a block must be at minimum 1 sector (typically 512
31 * bytes or 4KB). Additionally, reading these small blocks tends to generate
32 * more random reads.
33 *
34 * Embedded-data Block Pointers allow small pieces of data (the "payload",
35 * up to 112 bytes) to be stored in the block pointer itself, instead of
36 * being pointed to. The "Pointer" part of this name is a bit of a
37 * misnomer, as nothing is pointed to.
38 *
39 * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to
40 * be embedded in the block pointer. The logic for this is handled in
41 * the SPA, by the zio pipeline. Therefore most code outside the zio
42 * pipeline doesn't need special-cases to handle these block pointers.
43 *
44 * See spa.h for details on the exact layout of embedded block pointers.
45 */
46
47 void
encode_embedded_bp_compressed(blkptr_t * bp,void * data,enum zio_compress comp,int uncompressed_size,int compressed_size)48 encode_embedded_bp_compressed(blkptr_t *bp, void *data,
49 enum zio_compress comp, int uncompressed_size, int compressed_size)
50 {
51 uint64_t *bp64 = (uint64_t *)bp;
52 uint64_t w = 0;
53 uint8_t *data8 = data;
54
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);
60
61 memset(bp, 0, 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);
67
68 /*
69 * Encode the byte array into the words of the block pointer.
70 * First byte goes into low bits of first word (little endian).
71 */
72 for (int 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);
77 *bp64 = w;
78 bp64++;
79 if (!BPE_IS_PAYLOADWORD(bp, bp64))
80 bp64++;
81 w = 0;
82 }
83 }
84 /* write last partial word */
85 if (bp64 < (uint64_t *)(bp + 1))
86 *bp64 = w;
87 }
88
89 /*
90 * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
91 * more than BPE_PAYLOAD_SIZE bytes).
92 */
93 void
decode_embedded_bp_compressed(const blkptr_t * bp,void * buf)94 decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
95 {
96 int psize;
97 uint8_t *buf8 = buf;
98 uint64_t w = 0;
99 const uint64_t *bp64 = (const uint64_t *)bp;
100
101 ASSERT(BP_IS_EMBEDDED(bp));
102
103 psize = BPE_GET_PSIZE(bp);
104
105 /*
106 * Decode the words of the block pointer into the byte array.
107 * Low bits of first word are the first byte (little endian).
108 */
109 for (int i = 0; i < psize; i++) {
110 if (i % sizeof (w) == 0) {
111 /* beginning of a word */
112 ASSERT3P(bp64, <, bp + 1);
113 w = *bp64;
114 bp64++;
115 if (!BPE_IS_PAYLOADWORD(bp, bp64))
116 bp64++;
117 }
118 buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);
119 }
120 }
121
122 /*
123 * Fill in the buffer with the (decompressed) payload of the embedded
124 * blkptr_t. Takes into account compression and byteorder (the payload is
125 * treated as a stream of bytes).
126 * Return 0 on success, or ENOSPC if it won't fit in the buffer.
127 */
128 int
decode_embedded_bp(const blkptr_t * bp,void * buf,int buflen)129 decode_embedded_bp(const blkptr_t *bp, void *buf, int buflen)
130 {
131 int lsize, psize;
132
133 ASSERT(BP_IS_EMBEDDED(bp));
134
135 lsize = BPE_GET_LSIZE(bp);
136 psize = BPE_GET_PSIZE(bp);
137
138 if (lsize > buflen)
139 return (SET_ERROR(ENOSPC));
140 ASSERT3U(lsize, ==, buflen);
141
142 if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF) {
143 uint8_t dstbuf[BPE_PAYLOAD_SIZE];
144 decode_embedded_bp_compressed(bp, dstbuf);
145 VERIFY0(zio_decompress_data_buf(BP_GET_COMPRESS(bp),
146 dstbuf, buf, psize, buflen, NULL));
147 } else {
148 ASSERT3U(lsize, ==, psize);
149 decode_embedded_bp_compressed(bp, buf);
150 }
151
152 return (0);
153 }
154