1 /* 2 * QEMU Enhanced Disk Format Cluster functions 3 * 4 * Copyright IBM, Corp. 2010 5 * 6 * Authors: 7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> 8 * Anthony Liguori <aliguori@us.ibm.com> 9 * 10 * This work is licensed under the terms of the GNU LGPL, version 2 or later. 11 * See the COPYING.LIB file in the top-level directory. 12 * 13 */ 14 15 #include "qemu/osdep.h" 16 #include "qed.h" 17 18 /** 19 * Count the number of contiguous data clusters 20 * 21 * @s: QED state 22 * @table: L2 table 23 * @index: First cluster index 24 * @n: Maximum number of clusters 25 * @offset: Set to first cluster offset 26 * 27 * This function scans tables for contiguous clusters. A contiguous run of 28 * clusters may be allocated, unallocated, or zero. 29 */ 30 static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s, 31 QEDTable *table, 32 unsigned int index, 33 unsigned int n, 34 uint64_t *offset) 35 { 36 unsigned int end = MIN(index + n, s->table_nelems); 37 uint64_t last = table->offsets[index]; 38 unsigned int i; 39 40 *offset = last; 41 42 for (i = index + 1; i < end; i++) { 43 if (qed_offset_is_unalloc_cluster(last)) { 44 /* Counting unallocated clusters */ 45 if (!qed_offset_is_unalloc_cluster(table->offsets[i])) { 46 break; 47 } 48 } else if (qed_offset_is_zero_cluster(last)) { 49 /* Counting zero clusters */ 50 if (!qed_offset_is_zero_cluster(table->offsets[i])) { 51 break; 52 } 53 } else { 54 /* Counting allocated clusters */ 55 if (table->offsets[i] != last + s->header.cluster_size) { 56 break; 57 } 58 last = table->offsets[i]; 59 } 60 } 61 return i - index; 62 } 63 64 /** 65 * Find the offset of a data cluster 66 * 67 * @s: QED state 68 * @request: L2 cache entry 69 * @pos: Byte position in device 70 * @len: Number of bytes (may be shortened on return) 71 * @img_offset: Contains offset in the image file on success 72 * 73 * This function translates a position in the block device to an offset in the 74 * image file. The translated offset or unallocated range in the image file is 75 * reported back in *img_offset and *len. 76 * 77 * If the L2 table exists, request->l2_table points to the L2 table cache entry 78 * and the caller must free the reference when they are finished. The cache 79 * entry is exposed in this way to avoid callers having to read the L2 table 80 * again later during request processing. If request->l2_table is non-NULL it 81 * will be unreferenced before taking on the new cache entry. 82 * 83 * On success QED_CLUSTER_FOUND is returned and img_offset/len are a contiguous 84 * range in the image file. 85 * 86 * On failure QED_CLUSTER_L2 or QED_CLUSTER_L1 is returned for missing L2 or L1 87 * table offset, respectively. len is number of contiguous unallocated bytes. 88 * 89 * Called with table_lock held. 90 */ 91 int coroutine_fn qed_find_cluster(BDRVQEDState *s, QEDRequest *request, 92 uint64_t pos, size_t *len, 93 uint64_t *img_offset) 94 { 95 uint64_t l2_offset; 96 uint64_t offset = 0; 97 unsigned int index; 98 unsigned int n; 99 int ret; 100 101 /* Limit length to L2 boundary. Requests are broken up at the L2 boundary 102 * so that a request acts on one L2 table at a time. 103 */ 104 *len = MIN(*len, (((pos >> s->l1_shift) + 1) << s->l1_shift) - pos); 105 106 l2_offset = s->l1_table->offsets[qed_l1_index(s, pos)]; 107 if (qed_offset_is_unalloc_cluster(l2_offset)) { 108 *img_offset = 0; 109 return QED_CLUSTER_L1; 110 } 111 if (!qed_check_table_offset(s, l2_offset)) { 112 *img_offset = *len = 0; 113 return -EINVAL; 114 } 115 116 ret = qed_read_l2_table(s, request, l2_offset); 117 if (ret) { 118 goto out; 119 } 120 121 index = qed_l2_index(s, pos); 122 n = qed_bytes_to_clusters(s, qed_offset_into_cluster(s, pos) + *len); 123 n = qed_count_contiguous_clusters(s, request->l2_table->table, 124 index, n, &offset); 125 126 if (qed_offset_is_unalloc_cluster(offset)) { 127 ret = QED_CLUSTER_L2; 128 } else if (qed_offset_is_zero_cluster(offset)) { 129 ret = QED_CLUSTER_ZERO; 130 } else if (qed_check_cluster_offset(s, offset)) { 131 ret = QED_CLUSTER_FOUND; 132 } else { 133 ret = -EINVAL; 134 } 135 136 *len = MIN(*len, 137 n * s->header.cluster_size - qed_offset_into_cluster(s, pos)); 138 139 out: 140 *img_offset = offset; 141 return ret; 142 } 143