qemu

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/*
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 * QEMU Enhanced Disk Format Consistency Check
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 *
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 * Copyright IBM, Corp. 2010
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 *
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 * Authors:
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 *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
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 *
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 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
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 * See the COPYING.LIB file in the top-level directory.
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 *
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 */
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#include "qemu/osdep.h"
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#include "block/block-io.h"
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#include "qed.h"
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typedef struct {
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    BDRVQEDState *s;
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    BdrvCheckResult *result;
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    bool fix;                           /* whether to fix invalid offsets */
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    uint64_t nclusters;
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    uint32_t *used_clusters;            /* referenced cluster bitmap */
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    QEDRequest request;
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} QEDCheck;
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static bool qed_test_bit(uint32_t *bitmap, uint64_t n) {
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    return !!(bitmap[n / 32] & (1 << (n % 32)));
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}
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static void qed_set_bit(uint32_t *bitmap, uint64_t n) {
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    bitmap[n / 32] |= 1 << (n % 32);
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}
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/**
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 * Set bitmap bits for clusters
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 *
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 * @check:          Check structure
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 * @offset:         Starting offset in bytes
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 * @n:              Number of clusters
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 */
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static bool qed_set_used_clusters(QEDCheck *check, uint64_t offset,
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                                  unsigned int n)
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{
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    uint64_t cluster = qed_bytes_to_clusters(check->s, offset);
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    unsigned int corruptions = 0;
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    while (n-- != 0) {
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        /* Clusters should only be referenced once */
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        if (qed_test_bit(check->used_clusters, cluster)) {
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            corruptions++;
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        }
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        qed_set_bit(check->used_clusters, cluster);
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        cluster++;
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    }
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    check->result->corruptions += corruptions;
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    return corruptions == 0;
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}
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/**
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 * Check an L2 table
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 *
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 * @ret:            Number of invalid cluster offsets
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 */
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static unsigned int qed_check_l2_table(QEDCheck *check, QEDTable *table)
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{
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    BDRVQEDState *s = check->s;
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    unsigned int i, num_invalid = 0;
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    uint64_t last_offset = 0;
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    for (i = 0; i < s->table_nelems; i++) {
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        uint64_t offset = table->offsets[i];
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        if (qed_offset_is_unalloc_cluster(offset) ||
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            qed_offset_is_zero_cluster(offset)) {
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            continue;
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        }
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        check->result->bfi.allocated_clusters++;
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        if (last_offset && (last_offset + s->header.cluster_size != offset)) {
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            check->result->bfi.fragmented_clusters++;
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        }
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        last_offset = offset;
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        /* Detect invalid cluster offset */
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        if (!qed_check_cluster_offset(s, offset)) {
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            if (check->fix) {
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                table->offsets[i] = 0;
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                check->result->corruptions_fixed++;
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            } else {
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                check->result->corruptions++;
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            }
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            num_invalid++;
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            continue;
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        }
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        qed_set_used_clusters(check, offset, 1);
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    }
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    return num_invalid;
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}
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/**
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 * Descend tables and check each cluster is referenced once only
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 */
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static int coroutine_fn GRAPH_RDLOCK
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qed_check_l1_table(QEDCheck *check, QEDTable *table)
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{
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    BDRVQEDState *s = check->s;
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    unsigned int i, num_invalid_l1 = 0;
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    int ret, last_error = 0;
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    /* Mark L1 table clusters used */
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    qed_set_used_clusters(check, s->header.l1_table_offset,
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                          s->header.table_size);
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    for (i = 0; i < s->table_nelems; i++) {
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        unsigned int num_invalid_l2;
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        uint64_t offset = table->offsets[i];
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        if (qed_offset_is_unalloc_cluster(offset)) {
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            continue;
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        }
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        /* Detect invalid L2 offset */
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        if (!qed_check_table_offset(s, offset)) {
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            /* Clear invalid offset */
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            if (check->fix) {
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                table->offsets[i] = 0;
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                check->result->corruptions_fixed++;
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            } else {
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                check->result->corruptions++;
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            }
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            num_invalid_l1++;
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            continue;
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        }
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        if (!qed_set_used_clusters(check, offset, s->header.table_size)) {
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            continue; /* skip an invalid table */
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        }
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        ret = qed_read_l2_table_sync(s, &check->request, offset);
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        if (ret) {
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            check->result->check_errors++;
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            last_error = ret;
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            continue;
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        }
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        num_invalid_l2 = qed_check_l2_table(check,
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                                            check->request.l2_table->table);
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        /* Write out fixed L2 table */
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        if (num_invalid_l2 > 0 && check->fix) {
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            ret = qed_write_l2_table_sync(s, &check->request, 0,
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                                          s->table_nelems, false);
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            if (ret) {
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                check->result->check_errors++;
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                last_error = ret;
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                continue;
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            }
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        }
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    }
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    /* Drop reference to final table */
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    qed_unref_l2_cache_entry(check->request.l2_table);
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    check->request.l2_table = NULL;
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    /* Write out fixed L1 table */
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    if (num_invalid_l1 > 0 && check->fix) {
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        ret = qed_write_l1_table_sync(s, 0, s->table_nelems);
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        if (ret) {
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            check->result->check_errors++;
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            last_error = ret;
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        }
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    }
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    return last_error;
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}
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/**
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 * Check for unreferenced (leaked) clusters
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 */
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static void qed_check_for_leaks(QEDCheck *check)
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{
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    BDRVQEDState *s = check->s;
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    uint64_t i;
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    for (i = s->header.header_size; i < check->nclusters; i++) {
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        if (!qed_test_bit(check->used_clusters, i)) {
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            check->result->leaks++;
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        }
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    }
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}
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/**
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 * Mark an image clean once it passes check or has been repaired
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 */
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static void coroutine_fn GRAPH_RDLOCK
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qed_check_mark_clean(BDRVQEDState *s, BdrvCheckResult *result)
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{
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    /* Skip if there were unfixable corruptions or I/O errors */
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    if (result->corruptions > 0 || result->check_errors > 0) {
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        return;
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    }
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    /* Skip if image is already marked clean */
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    if (!(s->header.features & QED_F_NEED_CHECK)) {
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        return;
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    }
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    /* Ensure fixes reach storage before clearing check bit */
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    bdrv_co_flush(s->bs);
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    s->header.features &= ~QED_F_NEED_CHECK;
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    qed_write_header_sync(s);
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}
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/* Called with table_lock held.  */
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int coroutine_fn qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix)
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{
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    QEDCheck check = {
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        .s = s,
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        .result = result,
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        .nclusters = qed_bytes_to_clusters(s, s->file_size),
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        .request = { .l2_table = NULL },
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        .fix = fix,
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    };
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    int ret;
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    check.used_clusters = g_try_new0(uint32_t, (check.nclusters + 31) / 32);
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    if (check.nclusters && check.used_clusters == NULL) {
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        return -ENOMEM;
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    }
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    check.result->bfi.total_clusters =
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        DIV_ROUND_UP(s->header.image_size, s->header.cluster_size);
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    ret = qed_check_l1_table(&check, s->l1_table);
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    if (ret == 0) {
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        /* Only check for leaks if entire image was scanned successfully */
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        qed_check_for_leaks(&check);
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        if (fix) {
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            qed_check_mark_clean(s, result);
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        }
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    }
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    g_free(check.used_clusters);
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    return ret;
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}
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