qemu/block/qed-check.c
<<
>>
Prefs
   1/*
   2 * QEMU Enhanced Disk Format Consistency Check
   3 *
   4 * Copyright IBM, Corp. 2010
   5 *
   6 * Authors:
   7 *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
   8 *
   9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10 * See the COPYING.LIB file in the top-level directory.
  11 *
  12 */
  13
  14#include "qemu/osdep.h"
  15#include "qed.h"
  16
  17typedef struct {
  18    BDRVQEDState *s;
  19    BdrvCheckResult *result;
  20    bool fix;                           /* whether to fix invalid offsets */
  21
  22    uint64_t nclusters;
  23    uint32_t *used_clusters;            /* referenced cluster bitmap */
  24
  25    QEDRequest request;
  26} QEDCheck;
  27
  28static bool qed_test_bit(uint32_t *bitmap, uint64_t n) {
  29    return !!(bitmap[n / 32] & (1 << (n % 32)));
  30}
  31
  32static void qed_set_bit(uint32_t *bitmap, uint64_t n) {
  33    bitmap[n / 32] |= 1 << (n % 32);
  34}
  35
  36/**
  37 * Set bitmap bits for clusters
  38 *
  39 * @check:          Check structure
  40 * @offset:         Starting offset in bytes
  41 * @n:              Number of clusters
  42 */
  43static bool qed_set_used_clusters(QEDCheck *check, uint64_t offset,
  44                                  unsigned int n)
  45{
  46    uint64_t cluster = qed_bytes_to_clusters(check->s, offset);
  47    unsigned int corruptions = 0;
  48
  49    while (n-- != 0) {
  50        /* Clusters should only be referenced once */
  51        if (qed_test_bit(check->used_clusters, cluster)) {
  52            corruptions++;
  53        }
  54
  55        qed_set_bit(check->used_clusters, cluster);
  56        cluster++;
  57    }
  58
  59    check->result->corruptions += corruptions;
  60    return corruptions == 0;
  61}
  62
  63/**
  64 * Check an L2 table
  65 *
  66 * @ret:            Number of invalid cluster offsets
  67 */
  68static unsigned int qed_check_l2_table(QEDCheck *check, QEDTable *table)
  69{
  70    BDRVQEDState *s = check->s;
  71    unsigned int i, num_invalid = 0;
  72    uint64_t last_offset = 0;
  73
  74    for (i = 0; i < s->table_nelems; i++) {
  75        uint64_t offset = table->offsets[i];
  76
  77        if (qed_offset_is_unalloc_cluster(offset) ||
  78            qed_offset_is_zero_cluster(offset)) {
  79            continue;
  80        }
  81        check->result->bfi.allocated_clusters++;
  82        if (last_offset && (last_offset + s->header.cluster_size != offset)) {
  83            check->result->bfi.fragmented_clusters++;
  84        }
  85        last_offset = offset;
  86
  87        /* Detect invalid cluster offset */
  88        if (!qed_check_cluster_offset(s, offset)) {
  89            if (check->fix) {
  90                table->offsets[i] = 0;
  91                check->result->corruptions_fixed++;
  92            } else {
  93                check->result->corruptions++;
  94            }
  95
  96            num_invalid++;
  97            continue;
  98        }
  99
 100        qed_set_used_clusters(check, offset, 1);
 101    }
 102
 103    return num_invalid;
 104}
 105
 106/**
 107 * Descend tables and check each cluster is referenced once only
 108 */
 109static int qed_check_l1_table(QEDCheck *check, QEDTable *table)
 110{
 111    BDRVQEDState *s = check->s;
 112    unsigned int i, num_invalid_l1 = 0;
 113    int ret, last_error = 0;
 114
 115    /* Mark L1 table clusters used */
 116    qed_set_used_clusters(check, s->header.l1_table_offset,
 117                          s->header.table_size);
 118
 119    for (i = 0; i < s->table_nelems; i++) {
 120        unsigned int num_invalid_l2;
 121        uint64_t offset = table->offsets[i];
 122
 123        if (qed_offset_is_unalloc_cluster(offset)) {
 124            continue;
 125        }
 126
 127        /* Detect invalid L2 offset */
 128        if (!qed_check_table_offset(s, offset)) {
 129            /* Clear invalid offset */
 130            if (check->fix) {
 131                table->offsets[i] = 0;
 132                check->result->corruptions_fixed++;
 133            } else {
 134                check->result->corruptions++;
 135            }
 136
 137            num_invalid_l1++;
 138            continue;
 139        }
 140
 141        if (!qed_set_used_clusters(check, offset, s->header.table_size)) {
 142            continue; /* skip an invalid table */
 143        }
 144
 145        ret = qed_read_l2_table_sync(s, &check->request, offset);
 146        if (ret) {
 147            check->result->check_errors++;
 148            last_error = ret;
 149            continue;
 150        }
 151
 152        num_invalid_l2 = qed_check_l2_table(check,
 153                                            check->request.l2_table->table);
 154
 155        /* Write out fixed L2 table */
 156        if (num_invalid_l2 > 0 && check->fix) {
 157            ret = qed_write_l2_table_sync(s, &check->request, 0,
 158                                          s->table_nelems, false);
 159            if (ret) {
 160                check->result->check_errors++;
 161                last_error = ret;
 162                continue;
 163            }
 164        }
 165    }
 166
 167    /* Drop reference to final table */
 168    qed_unref_l2_cache_entry(check->request.l2_table);
 169    check->request.l2_table = NULL;
 170
 171    /* Write out fixed L1 table */
 172    if (num_invalid_l1 > 0 && check->fix) {
 173        ret = qed_write_l1_table_sync(s, 0, s->table_nelems);
 174        if (ret) {
 175            check->result->check_errors++;
 176            last_error = ret;
 177        }
 178    }
 179
 180    return last_error;
 181}
 182
 183/**
 184 * Check for unreferenced (leaked) clusters
 185 */
 186static void qed_check_for_leaks(QEDCheck *check)
 187{
 188    BDRVQEDState *s = check->s;
 189    uint64_t i;
 190
 191    for (i = s->header.header_size; i < check->nclusters; i++) {
 192        if (!qed_test_bit(check->used_clusters, i)) {
 193            check->result->leaks++;
 194        }
 195    }
 196}
 197
 198/**
 199 * Mark an image clean once it passes check or has been repaired
 200 */
 201static void qed_check_mark_clean(BDRVQEDState *s, BdrvCheckResult *result)
 202{
 203    /* Skip if there were unfixable corruptions or I/O errors */
 204    if (result->corruptions > 0 || result->check_errors > 0) {
 205        return;
 206    }
 207
 208    /* Skip if image is already marked clean */
 209    if (!(s->header.features & QED_F_NEED_CHECK)) {
 210        return;
 211    }
 212
 213    /* Ensure fixes reach storage before clearing check bit */
 214    bdrv_flush(s->bs);
 215
 216    s->header.features &= ~QED_F_NEED_CHECK;
 217    qed_write_header_sync(s);
 218}
 219
 220int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix)
 221{
 222    QEDCheck check = {
 223        .s = s,
 224        .result = result,
 225        .nclusters = qed_bytes_to_clusters(s, s->file_size),
 226        .request = { .l2_table = NULL },
 227        .fix = fix,
 228    };
 229    int ret;
 230
 231    check.used_clusters = g_try_new0(uint32_t, (check.nclusters + 31) / 32);
 232    if (check.nclusters && check.used_clusters == NULL) {
 233        return -ENOMEM;
 234    }
 235
 236    check.result->bfi.total_clusters =
 237        DIV_ROUND_UP(s->header.image_size, s->header.cluster_size);
 238    ret = qed_check_l1_table(&check, s->l1_table);
 239    if (ret == 0) {
 240        /* Only check for leaks if entire image was scanned successfully */
 241        qed_check_for_leaks(&check);
 242
 243        if (fix) {
 244            qed_check_mark_clean(s, result);
 245        }
 246    }
 247
 248    g_free(check.used_clusters);
 249    return ret;
 250}
 251