From d4803ddf6139cf2ad7e2d53035b5f828da97b51c Mon Sep 17 00:00:00 2001

From: Max Reitz <mreitz@redhat.com>

Date: Mon, 4 Nov 2013 22:32:04 +0100

Subject: [PATCH 11/87] qcow2-refcount: Repair shared refcount blocks

RH-Author: Max Reitz <mreitz@redhat.com>

Message-id: <1383604354-12743-14-git-send-email-mreitz@redhat.com>

Patchwork-id: 55313

O-Subject: [RHEL-7.0 qemu-kvm PATCH 13/43] qcow2-refcount: Repair shared refcount blocks

Bugzilla: 1004347

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

RH-Acked-by: Fam Zheng <famz@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

BZ: 1004347

If the refcount of a refcount block is greater than one, we can at least

try to repair that problem by duplicating the affected block.

Signed-off-by: Max Reitz <mreitz@redhat.com>

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

(cherry picked from commit afa50193cde574528a130a25544fd6f3aa8da069)

Signed-off-by: Max Reitz <mreitz@redhat.com>

---

 block/blkdebug.c       |   1 +

 block/qcow2-refcount.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++-

 include/block/block.h  |   1 +

 3 files changed, 148 insertions(+), 2 deletions(-)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 block/blkdebug.c       |    1 +

 block/qcow2-refcount.c |  148 +++++++++++++++++++++++++++++++++++++++++++++++-

 include/block/block.h  |    1 +

 3 files changed, 148 insertions(+), 2 deletions(-)

diff --git a/block/blkdebug.c b/block/blkdebug.c

index 71f99e4..d659d38 100644

--- a/block/blkdebug.c

+++ b/block/blkdebug.c

@@ -168,6 +168,7 @@ static const char *event_names[BLKDBG_EVENT_MAX] = {

     [BLKDBG_REFTABLE_LOAD]                  = "reftable_load",

     [BLKDBG_REFTABLE_GROW]                  = "reftable_grow",

+    [BLKDBG_REFTABLE_UPDATE]                = "reftable_update",

     [BLKDBG_REFBLOCK_LOAD]                  = "refblock_load",

     [BLKDBG_REFBLOCK_UPDATE]                = "refblock_update",

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c

index 92ecc64..927bdeb 100644

--- a/block/qcow2-refcount.c

+++ b/block/qcow2-refcount.c

@@ -1320,6 +1320,121 @@ fail:

 }

 /*

+ * Writes one sector of the refcount table to the disk

+ */

+#define RT_ENTRIES_PER_SECTOR (512 / sizeof(uint64_t))

+static int write_reftable_entry(BlockDriverState *bs, int rt_index)

+{

+    BDRVQcowState *s = bs->opaque;

+    uint64_t buf[RT_ENTRIES_PER_SECTOR];

+    int rt_start_index;

+    int i, ret;

+

+    rt_start_index = rt_index & ~(RT_ENTRIES_PER_SECTOR - 1);

+    for (i = 0; i < RT_ENTRIES_PER_SECTOR; i++) {

+        buf[i] = cpu_to_be64(s->refcount_table[rt_start_index + i]);

+    }

+

+    ret = qcow2_pre_write_overlap_check(bs,

+            QCOW2_OL_DEFAULT & ~QCOW2_OL_REFCOUNT_TABLE,

+            s->refcount_table_offset + rt_start_index * sizeof(uint64_t),

+            sizeof(buf));

+    if (ret < 0) {

+        return ret;

+    }

+

+    BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_UPDATE);

+    ret = bdrv_pwrite_sync(bs->file, s->refcount_table_offset +

+            rt_start_index * sizeof(uint64_t), buf, sizeof(buf));

+    if (ret < 0) {

+        return ret;

+    }

+

+    return 0;

+}

+

+/*

+ * Allocates a new cluster for the given refcount block (represented by its

+ * offset in the image file) and copies the current content there. This function

+ * does _not_ decrement the reference count for the currently occupied cluster.

+ *

+ * This function prints an informative message to stderr on error (and returns

+ * -errno); on success, 0 is returned.

+ */

+static int64_t realloc_refcount_block(BlockDriverState *bs, int reftable_index,

+                                      uint64_t offset)

+{

+    BDRVQcowState *s = bs->opaque;

+    int64_t new_offset = 0;

+    void *refcount_block = NULL;

+    int ret;

+

+    /* allocate new refcount block */

+    new_offset = qcow2_alloc_clusters(bs, s->cluster_size);

+    if (new_offset < 0) {

+        fprintf(stderr, "Could not allocate new cluster: %s\n",

+                strerror(-new_offset));

+        ret = new_offset;

+        goto fail;

+    }

+

+    /* fetch current refcount block content */

+    ret = qcow2_cache_get(bs, s->refcount_block_cache, offset, &refcount_block);

+    if (ret < 0) {

+        fprintf(stderr, "Could not fetch refcount block: %s\n", strerror(-ret));

+        goto fail;

+    }

+

+    /* new block has not yet been entered into refcount table, therefore it is

+     * no refcount block yet (regarding this check) */

+    ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_DEFAULT, new_offset,

+            s->cluster_size);

+    if (ret < 0) {

+        fprintf(stderr, "Could not write refcount block; metadata overlap "

+                "check failed: %s\n", strerror(-ret));

+        /* the image will be marked corrupt, so don't even attempt on freeing

+         * the cluster */

+        new_offset = 0;

+        goto fail;

+    }

+

+    /* write to new block */

+    ret = bdrv_write(bs->file, new_offset / BDRV_SECTOR_SIZE, refcount_block,

+            s->cluster_sectors);

+    if (ret < 0) {

+        fprintf(stderr, "Could not write refcount block: %s\n", strerror(-ret));

+        goto fail;

+    }

+

+    /* update refcount table */

+    assert(!(new_offset & (s->cluster_size - 1)));

+    s->refcount_table[reftable_index] = new_offset;

+    ret = write_reftable_entry(bs, reftable_index);

+    if (ret < 0) {

+        fprintf(stderr, "Could not update refcount table: %s\n",

+                strerror(-ret));

+        goto fail;

+    }

+

+fail:

+    if (new_offset && (ret < 0)) {

+        qcow2_free_clusters(bs, new_offset, s->cluster_size,

+                QCOW2_DISCARD_ALWAYS);

+    }

+    if (refcount_block) {

+        if (ret < 0) {

+            qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);

+        } else {

+            ret = qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);

+        }

+    }

+    if (ret < 0) {

+        return ret;

+    }

+    return new_offset;

+}

+

+/*

  * Checks an image for refcount consistency.

  *

  * Returns 0 if no errors are found, the number of errors in case the image is

@@ -1395,10 +1510,39 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,

             inc_refcounts(bs, res, refcount_table, nb_clusters,

                 offset, s->cluster_size);

             if (refcount_table[cluster] != 1) {

-                fprintf(stderr, "ERROR refcount block %" PRId64

+                fprintf(stderr, "%s refcount block %" PRId64

                     " refcount=%d\n",

+                    fix & BDRV_FIX_ERRORS ? "Repairing" :

+                                            "ERROR",

                     i, refcount_table[cluster]);

-                res->corruptions++;

+

+                if (fix & BDRV_FIX_ERRORS) {

+                    int64_t new_offset;

+

+                    new_offset = realloc_refcount_block(bs, i, offset);

+                    if (new_offset < 0) {

+                        res->corruptions++;

+                        continue;

+                    }

+

+                    /* update refcounts */

+                    if ((new_offset >> s->cluster_bits) >= nb_clusters) {

+                        /* increase refcount_table size if necessary */

+                        int old_nb_clusters = nb_clusters;

+                        nb_clusters = (new_offset >> s->cluster_bits) + 1;

+                        refcount_table = g_realloc(refcount_table,

+                                nb_clusters * sizeof(uint16_t));

+                        memset(&refcount_table[old_nb_clusters], 0, (nb_clusters

+                                - old_nb_clusters) * sizeof(uint16_t));

+                    }

+                    refcount_table[cluster]--;

+                    inc_refcounts(bs, res, refcount_table, nb_clusters,

+                            new_offset, s->cluster_size);

+

+                    res->corruptions_fixed++;

+                } else {

+                    res->corruptions++;

+                }

             }

         }

     }

diff --git a/include/block/block.h b/include/block/block.h

index 03ebc47..39770a3 100644

--- a/include/block/block.h

+++ b/include/block/block.h

@@ -447,6 +447,7 @@ typedef enum {

     BLKDBG_REFTABLE_LOAD,

     BLKDBG_REFTABLE_GROW,

+    BLKDBG_REFTABLE_UPDATE,

     BLKDBG_REFBLOCK_LOAD,

     BLKDBG_REFBLOCK_UPDATE,

-- 

1.7.1