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From d4803ddf6139cf2ad7e2d53035b5f828da97b51c Mon Sep 17 00:00:00 2001
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From: Max Reitz <mreitz@redhat.com>
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Date: Mon, 4 Nov 2013 22:32:04 +0100
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Subject: [PATCH 11/87] qcow2-refcount: Repair shared refcount blocks
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RH-Author: Max Reitz <mreitz@redhat.com>
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Message-id: <1383604354-12743-14-git-send-email-mreitz@redhat.com>
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Patchwork-id: 55313
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O-Subject: [RHEL-7.0 qemu-kvm PATCH 13/43] qcow2-refcount: Repair shared refcount blocks
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Bugzilla: 1004347
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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BZ: 1004347
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If the refcount of a refcount block is greater than one, we can at least
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try to repair that problem by duplicating the affected block.
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit afa50193cde574528a130a25544fd6f3aa8da069)
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Signed-off-by: Max Reitz <mreitz@redhat.com>
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---
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 block/blkdebug.c       |   1 +
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 block/qcow2-refcount.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++-
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 include/block/block.h  |   1 +
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 3 files changed, 148 insertions(+), 2 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block/blkdebug.c       |    1 +
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 block/qcow2-refcount.c |  148 +++++++++++++++++++++++++++++++++++++++++++++++-
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 include/block/block.h  |    1 +
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 3 files changed, 148 insertions(+), 2 deletions(-)
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diff --git a/block/blkdebug.c b/block/blkdebug.c
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index 71f99e4..d659d38 100644
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--- a/block/blkdebug.c
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+++ b/block/blkdebug.c
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@@ -168,6 +168,7 @@ static const char *event_names[BLKDBG_EVENT_MAX] = {
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     [BLKDBG_REFTABLE_LOAD]                  = "reftable_load",
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     [BLKDBG_REFTABLE_GROW]                  = "reftable_grow",
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+    [BLKDBG_REFTABLE_UPDATE]                = "reftable_update",
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     [BLKDBG_REFBLOCK_LOAD]                  = "refblock_load",
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     [BLKDBG_REFBLOCK_UPDATE]                = "refblock_update",
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diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
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index 92ecc64..927bdeb 100644
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--- a/block/qcow2-refcount.c
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+++ b/block/qcow2-refcount.c
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@@ -1320,6 +1320,121 @@ fail:
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 }
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 /*
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+ * Writes one sector of the refcount table to the disk
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+ */
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+#define RT_ENTRIES_PER_SECTOR (512 / sizeof(uint64_t))
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+static int write_reftable_entry(BlockDriverState *bs, int rt_index)
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+{
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+    BDRVQcowState *s = bs->opaque;
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+    uint64_t buf[RT_ENTRIES_PER_SECTOR];
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+    int rt_start_index;
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+    int i, ret;
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+
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+    rt_start_index = rt_index & ~(RT_ENTRIES_PER_SECTOR - 1);
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+    for (i = 0; i < RT_ENTRIES_PER_SECTOR; i++) {
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+        buf[i] = cpu_to_be64(s->refcount_table[rt_start_index + i]);
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+    }
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+
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+    ret = qcow2_pre_write_overlap_check(bs,
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+            QCOW2_OL_DEFAULT & ~QCOW2_OL_REFCOUNT_TABLE,
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+            s->refcount_table_offset + rt_start_index * sizeof(uint64_t),
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+            sizeof(buf));
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+    if (ret < 0) {
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+        return ret;
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+    }
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+
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+    BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_UPDATE);
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+    ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset +
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+            rt_start_index * sizeof(uint64_t), buf, sizeof(buf));
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+    if (ret < 0) {
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+        return ret;
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+    }
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+
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+    return 0;
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+}
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+
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+/*
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+ * Allocates a new cluster for the given refcount block (represented by its
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+ * offset in the image file) and copies the current content there. This function
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+ * does _not_ decrement the reference count for the currently occupied cluster.
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+ *
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+ * This function prints an informative message to stderr on error (and returns
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+ * -errno); on success, 0 is returned.
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+ */
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+static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index,
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+                                      uint64_t offset)
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+{
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+    BDRVQcowState *s = bs->opaque;
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+    int64_t new_offset = 0;
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+    void *refcount_block = NULL;
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+    int ret;
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+
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+    /* allocate new refcount block */
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+    new_offset = qcow2_alloc_clusters(bs, s->cluster_size);
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+    if (new_offset < 0) {
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+        fprintf(stderr, "Could not allocate new cluster: %s\n",
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+                strerror(-new_offset));
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+        ret = new_offset;
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+        goto fail;
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+    }
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+
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+    /* fetch current refcount block content */
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+    ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block);
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+    if (ret < 0) {
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+        fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret));
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+        goto fail;
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+    }
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+
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+    /* new block has not yet been entered into refcount table, therefore it is
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+     * no refcount block yet (regarding this check) */
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+    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT, new_offset,
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+            s->cluster_size);
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+    if (ret < 0) {
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+        fprintf(stderr, "Could not write refcount block; metadata overlap "
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+                "check failed: %s\n", strerror(-ret));
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+        /* the image will be marked corrupt, so don't even attempt on freeing
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+         * the cluster */
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+        new_offset = 0;
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+        goto fail;
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+    }
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+
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+    /* write to new block */
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+    ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block,
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+            s->cluster_sectors);
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+    if (ret < 0) {
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+        fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret));
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+        goto fail;
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+    }
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+
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+    /* update refcount table */
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+    assert(!(new_offset & (s->cluster_size - 1)));
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+    s->refcount_table[reftable_index] = new_offset;
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+    ret = write_reftable_entry(bs, reftable_index);
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+    if (ret < 0) {
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+        fprintf(stderr, "Could not update refcount table: %s\n",
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+                strerror(-ret));
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+        goto fail;
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+    }
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+
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+fail:
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+    if (new_offset && (ret < 0)) {
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+        qcow2_free_clusters(bs, new_offset, s->cluster_size,
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+                QCOW2_DISCARD_ALWAYS);
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+    }
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+    if (refcount_block) {
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+        if (ret < 0) {
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+            qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
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+        } else {
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+            ret = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
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+        }
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+    }
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+    if (ret < 0) {
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+        return ret;
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+    }
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+    return new_offset;
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+}
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+
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+/*
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  * Checks an image for refcount consistency.
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  *
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  * Returns 0 if no errors are found, the number of errors in case the image is
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@@ -1395,10 +1510,39 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
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             inc_refcounts(bs, res, refcount_table, nb_clusters,
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                 offset, s->cluster_size);
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             if (refcount_table[cluster] != 1) {
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-                fprintf(stderr, "ERROR refcount block %" PRId64
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+                fprintf(stderr, "%s refcount block %" PRId64
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                     " refcount=%d\n",
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+                    fix & BDRV_FIX_ERRORS ? "Repairing" :
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+                                            "ERROR",
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                     i, refcount_table[cluster]);
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-                res->corruptions++;
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+
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+                if (fix & BDRV_FIX_ERRORS) {
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+                    int64_t new_offset;
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+
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+                    new_offset = realloc_refcount_block(bs, i, offset);
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+                    if (new_offset < 0) {
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+                        res->corruptions++;
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+                        continue;
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+                    }
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+
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+                    /* update refcounts */
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+                    if ((new_offset >> s->cluster_bits) >= nb_clusters) {
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+                        /* increase refcount_table size if necessary */
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+                        int old_nb_clusters = nb_clusters;
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+                        nb_clusters = (new_offset >> s->cluster_bits) + 1;
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+                        refcount_table = g_realloc(refcount_table,
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+                                nb_clusters * sizeof(uint16_t));
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+                        memset(&refcount_table[old_nb_clusters], 0, (nb_clusters
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+                                - old_nb_clusters) * sizeof(uint16_t));
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+                    }
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+                    refcount_table[cluster]--;
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+                    inc_refcounts(bs, res, refcount_table, nb_clusters,
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+                            new_offset, s->cluster_size);
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+
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+                    res->corruptions_fixed++;
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+                } else {
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+                    res->corruptions++;
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+                }
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             }
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         }
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     }
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diff --git a/include/block/block.h b/include/block/block.h
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index 03ebc47..39770a3 100644
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--- a/include/block/block.h
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+++ b/include/block/block.h
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@@ -447,6 +447,7 @@ typedef enum {
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     BLKDBG_REFTABLE_LOAD,
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     BLKDBG_REFTABLE_GROW,
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+    BLKDBG_REFTABLE_UPDATE,
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     BLKDBG_REFBLOCK_LOAD,
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     BLKDBG_REFBLOCK_UPDATE,
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-- 
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1.7.1
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