1 // SPDX-License-Identifier: CDDL-1.0
2 /*
3 * CDDL HEADER START
4 *
5 * This file and its contents are supplied under the terms of the
6 * Common Development and Distribution License ("CDDL"), version 1.0.
7 * You may only use this file in accordance with the terms of version
8 * 1.0 of the CDDL.
9 *
10 * A full copy of the text of the CDDL should have accompanied this
11 * source. A copy of the CDDL is also available via the Internet at
12 * http://www.illumos.org/license/CDDL.
13 *
14 * CDDL HEADER END
15 */
16
17 /*
18 * Copyright (c) 2013, 2016 by Delphix. All rights reserved.
19 */
20
21 #include <sys/blkptr.h>
22 #include <sys/zfs_context.h>
23 #include <sys/zio.h>
24 #include <sys/zio_compress.h>
25
26 /*
27 * Embedded-data Block Pointers
28 *
29 * Normally, block pointers point (via their DVAs) to a block which holds data.
30 * If the data that we need to store is very small, this is an inefficient
31 * use of space, because a block must be at minimum 1 sector (typically 512
32 * bytes or 4KB). Additionally, reading these small blocks tends to generate
33 * more random reads.
34 *
35 * Embedded-data Block Pointers allow small pieces of data (the "payload",
36 * up to 112 bytes) to be stored in the block pointer itself, instead of
37 * being pointed to. The "Pointer" part of this name is a bit of a
38 * misnomer, as nothing is pointed to.
39 *
40 * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to
41 * be embedded in the block pointer. The logic for this is handled in
42 * the SPA, by the zio pipeline. Therefore most code outside the zio
43 * pipeline doesn't need special-cases to handle these block pointers.
44 *
45 * See spa.h for details on the exact layout of embedded block pointers.
46 */
47
48 void
encode_embedded_bp_compressed(blkptr_t * bp,void * data,enum zio_compress comp,int uncompressed_size,int compressed_size)49 encode_embedded_bp_compressed(blkptr_t *bp, void *data,
50 enum zio_compress comp, int uncompressed_size, int compressed_size)
51 {
52 uint64_t *bp64 = (uint64_t *)bp;
53 uint64_t w = 0;
54 uint8_t *data8 = data;
55
56 ASSERT3U(compressed_size, <=, BPE_PAYLOAD_SIZE);
57 ASSERT(uncompressed_size == compressed_size ||
58 comp != ZIO_COMPRESS_OFF);
59 ASSERT3U(comp, >=, ZIO_COMPRESS_OFF);
60 ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
61
62 memset(bp, 0, sizeof (*bp));
63 BP_SET_EMBEDDED(bp, B_TRUE);
64 BP_SET_COMPRESS(bp, comp);
65 BP_SET_BYTEORDER(bp, ZFS_HOST_BYTEORDER);
66 BPE_SET_LSIZE(bp, uncompressed_size);
67 BPE_SET_PSIZE(bp, compressed_size);
68
69 /*
70 * Encode the byte array into the words of the block pointer.
71 * First byte goes into low bits of first word (little endian).
72 */
73 for (int i = 0; i < compressed_size; i++) {
74 BF64_SET(w, (i % sizeof (w)) * NBBY, NBBY, data8[i]);
75 if (i % sizeof (w) == sizeof (w) - 1) {
76 /* we've reached the end of a word */
77 ASSERT3P(bp64, <, bp + 1);
78 *bp64 = w;
79 bp64++;
80 if (!BPE_IS_PAYLOADWORD(bp, bp64))
81 bp64++;
82 w = 0;
83 }
84 }
85 /* write last partial word */
86 if (bp64 < (uint64_t *)(bp + 1))
87 *bp64 = w;
88 }
89
90 /*
91 * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be
92 * more than BPE_PAYLOAD_SIZE bytes).
93 */
94 void
decode_embedded_bp_compressed(const blkptr_t * bp,void * buf)95 decode_embedded_bp_compressed(const blkptr_t *bp, void *buf)
96 {
97 int psize;
98 uint8_t *buf8 = buf;
99 uint64_t w = 0;
100 const uint64_t *bp64 = (const uint64_t *)bp;
101
102 ASSERT(BP_IS_EMBEDDED(bp));
103
104 psize = BPE_GET_PSIZE(bp);
105
106 /*
107 * Decode the words of the block pointer into the byte array.
108 * Low bits of first word are the first byte (little endian).
109 */
110 for (int i = 0; i < psize; i++) {
111 if (i % sizeof (w) == 0) {
112 /* beginning of a word */
113 ASSERT3P(bp64, <, bp + 1);
114 w = *bp64;
115 bp64++;
116 if (!BPE_IS_PAYLOADWORD(bp, bp64))
117 bp64++;
118 }
119 buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY);
120 }
121 }
122
123 /*
124 * Fill in the buffer with the (decompressed) payload of the embedded
125 * blkptr_t. Takes into account compression and byteorder (the payload is
126 * treated as a stream of bytes).
127 * Return 0 on success, or ENOSPC if it won't fit in the buffer.
128 */
129 int
decode_embedded_bp(const blkptr_t * bp,void * buf,int buflen)130 decode_embedded_bp(const blkptr_t *bp, void *buf, int buflen)
131 {
132 int lsize, psize;
133
134 ASSERT(BP_IS_EMBEDDED(bp));
135
136 lsize = BPE_GET_LSIZE(bp);
137 psize = BPE_GET_PSIZE(bp);
138
139 if (lsize > buflen)
140 return (SET_ERROR(ENOSPC));
141 ASSERT3U(lsize, ==, buflen);
142
143 if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF) {
144 uint8_t dstbuf[BPE_PAYLOAD_SIZE];
145 decode_embedded_bp_compressed(bp, dstbuf);
146 abd_t cabd, dabd;
147 abd_get_from_buf_struct(&cabd, dstbuf, psize);
148 abd_get_from_buf_struct(&dabd, buf, buflen);
149 VERIFY0(zio_decompress_data(BP_GET_COMPRESS(bp), &cabd,
150 &dabd, psize, buflen, NULL));
151 abd_free(&dabd);
152 abd_free(&cabd);
153 } else {
154 ASSERT3U(lsize, ==, psize);
155 decode_embedded_bp_compressed(bp, buf);
156 }
157
158 return (0);
159 }
160