1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
/*
* 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, 2016 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;
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 (int 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;
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 (int 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);
}
}
/*
* Fill in the buffer with the (decompressed) payload of the embedded
* blkptr_t. Takes into account compression and byteorder (the payload is
* treated as a stream of bytes).
* Return 0 on success, or ENOSPC if it won't fit in the buffer.
*/
int
decode_embedded_bp(const blkptr_t *bp, void *buf, int buflen)
{
int lsize, psize;
ASSERT(BP_IS_EMBEDDED(bp));
lsize = BPE_GET_LSIZE(bp);
psize = BPE_GET_PSIZE(bp);
if (lsize > buflen)
return (SET_ERROR(ENOSPC));
ASSERT3U(lsize, ==, buflen);
if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF) {
uint8_t dstbuf[BPE_PAYLOAD_SIZE];
decode_embedded_bp_compressed(bp, dstbuf);
VERIFY0(zio_decompress_data_buf(BP_GET_COMPRESS(bp),
dstbuf, buf, psize, buflen));
} else {
ASSERT3U(lsize, ==, psize);
decode_embedded_bp_compressed(bp, buf);
}
return (0);
}
|
