1*4a5d661aSToomas Soome /* 2*4a5d661aSToomas Soome * CDDL HEADER START 3*4a5d661aSToomas Soome * 4*4a5d661aSToomas Soome * This file and its contents are supplied under the terms of the 5*4a5d661aSToomas Soome * Common Development and Distribution License ("CDDL"), version 1.0. 6*4a5d661aSToomas Soome * You may only use this file in accordance with the terms of version 7*4a5d661aSToomas Soome * 1.0 of the CDDL. 8*4a5d661aSToomas Soome * 9*4a5d661aSToomas Soome * A full copy of the text of the CDDL should have accompanied this 10*4a5d661aSToomas Soome * source. A copy of the CDDL is also available via the Internet at 11*4a5d661aSToomas Soome * http://www.illumos.org/license/CDDL. 12*4a5d661aSToomas Soome * 13*4a5d661aSToomas Soome * CDDL HEADER END 14*4a5d661aSToomas Soome */ 15*4a5d661aSToomas Soome 16*4a5d661aSToomas Soome /* 17*4a5d661aSToomas Soome * Copyright (c) 2013 by Delphix. All rights reserved. 18*4a5d661aSToomas Soome */ 19*4a5d661aSToomas Soome 20*4a5d661aSToomas Soome /* 21*4a5d661aSToomas Soome * Embedded-data Block Pointers 22*4a5d661aSToomas Soome * 23*4a5d661aSToomas Soome * Normally, block pointers point (via their DVAs) to a block which holds data. 24*4a5d661aSToomas Soome * If the data that we need to store is very small, this is an inefficient 25*4a5d661aSToomas Soome * use of space, because a block must be at minimum 1 sector (typically 512 26*4a5d661aSToomas Soome * bytes or 4KB). Additionally, reading these small blocks tends to generate 27*4a5d661aSToomas Soome * more random reads. 28*4a5d661aSToomas Soome * 29*4a5d661aSToomas Soome * Embedded-data Block Pointers allow small pieces of data (the "payload", 30*4a5d661aSToomas Soome * up to 112 bytes) to be stored in the block pointer itself, instead of 31*4a5d661aSToomas Soome * being pointed to. The "Pointer" part of this name is a bit of a 32*4a5d661aSToomas Soome * misnomer, as nothing is pointed to. 33*4a5d661aSToomas Soome * 34*4a5d661aSToomas Soome * BP_EMBEDDED_TYPE_DATA block pointers allow highly-compressible data to 35*4a5d661aSToomas Soome * be embedded in the block pointer. The logic for this is handled in 36*4a5d661aSToomas Soome * the SPA, by the zio pipeline. Therefore most code outside the zio 37*4a5d661aSToomas Soome * pipeline doesn't need special-cases to handle these block pointers. 38*4a5d661aSToomas Soome * 39*4a5d661aSToomas Soome * See spa.h for details on the exact layout of embedded block pointers. 40*4a5d661aSToomas Soome */ 41*4a5d661aSToomas Soome 42*4a5d661aSToomas Soome /* 43*4a5d661aSToomas Soome * buf must be at least BPE_GET_PSIZE(bp) bytes long (which will never be 44*4a5d661aSToomas Soome * more than BPE_PAYLOAD_SIZE bytes). 45*4a5d661aSToomas Soome */ 46*4a5d661aSToomas Soome void 47*4a5d661aSToomas Soome decode_embedded_bp_compressed(const blkptr_t *bp, void *buf) 48*4a5d661aSToomas Soome { 49*4a5d661aSToomas Soome int psize; 50*4a5d661aSToomas Soome uint8_t *buf8 = buf; 51*4a5d661aSToomas Soome uint64_t w = 0; 52*4a5d661aSToomas Soome const uint64_t *bp64 = (const uint64_t *)bp; 53*4a5d661aSToomas Soome 54*4a5d661aSToomas Soome ASSERT(BP_IS_EMBEDDED(bp)); 55*4a5d661aSToomas Soome 56*4a5d661aSToomas Soome psize = BPE_GET_PSIZE(bp); 57*4a5d661aSToomas Soome 58*4a5d661aSToomas Soome /* 59*4a5d661aSToomas Soome * Decode the words of the block pointer into the byte array. 60*4a5d661aSToomas Soome * Low bits of first word are the first byte (little endian). 61*4a5d661aSToomas Soome */ 62*4a5d661aSToomas Soome for (int i = 0; i < psize; i++) { 63*4a5d661aSToomas Soome if (i % sizeof (w) == 0) { 64*4a5d661aSToomas Soome /* beginning of a word */ 65*4a5d661aSToomas Soome ASSERT3P(bp64, <, bp + 1); 66*4a5d661aSToomas Soome w = *bp64; 67*4a5d661aSToomas Soome bp64++; 68*4a5d661aSToomas Soome if (!BPE_IS_PAYLOADWORD(bp, bp64)) 69*4a5d661aSToomas Soome bp64++; 70*4a5d661aSToomas Soome } 71*4a5d661aSToomas Soome buf8[i] = BF64_GET(w, (i % sizeof (w)) * NBBY, NBBY); 72*4a5d661aSToomas Soome } 73*4a5d661aSToomas Soome } 74