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 by Delphix. All rights reserved. 18 */ 19 20 #include <sys/zfs_context.h> 21 #include <sys/zio.h> 22 #include <sys/zio_compress.h> 23 24 /* 25 * Embedded-data Block Pointers 26 * 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 31 * more random reads. 32 * 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. 37 * 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. 42 * 43 * See spa.h for details on the exact layout of embedded block pointers. 44 */ 45 46 void 47 encode_embedded_bp_compressed(blkptr_t *bp, void *data, 48 enum zio_compress comp, int uncompressed_size, int compressed_size) 49 { 50 uint64_t *bp64 = (uint64_t *)bp; 51 uint64_t w = 0; 52 uint8_t *data8 = data; 53 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); 59 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); 66 67 /* 68 * Encode the byte array into the words of the block pointer. 69 * First byte goes into low bits of first word (little endian). 70 */ 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); 76 *bp64 = w; 77 bp64++; 78 if (!BPE_IS_PAYLOADWORD(bp, bp64)) 79 bp64++; 80 w = 0; 81 } 82 } 83 /* write last partial word */ 84 if (bp64 < (uint64_t *)(bp + 1)) 85 *bp64 = w; 86 } 87 88 /* 89 * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be 90 * more than BPE_PAYLOAD_SIZE bytes). 91 */ 92 void 93 decode_embedded_bp_compressed(const blkptr_t *bp, void *buf) 94 { 95 int psize; 96 uint8_t *buf8 = buf; 97 uint64_t w = 0; 98 const uint64_t *bp64 = (const uint64_t *)bp; 99 100 ASSERT(BP_IS_EMBEDDED(bp)); 101 102 psize = BPE_GET_PSIZE(bp); 103 104 /* 105 * Decode the words of the block pointer into the byte array. 106 * Low bits of first word are the first byte (little endian). 107 */ 108 for (int i = 0; i < psize; i++) { 109 if (i % sizeof (w) == 0) { 110 /* beginning of a word */ 111 ASSERT3P(bp64, <, bp + 1); 112 w = *bp64; 113 bp64++; 114 if (!BPE_IS_PAYLOADWORD(bp, bp64)) 115 bp64++; 116 } 117 buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY); 118 } 119 } 120