From 3be020259d1627f335fe27aac1dc55e1249b7390 Mon Sep 17 00:00:00 2001

From: Max Reitz <mreitz@redhat.com>

Date: Sat, 13 Jun 2015 16:22:22 +0200

Subject: [PATCH 28/42] qcow2: Rebuild refcount structure during check

Message-id: <1434212556-3927-29-git-send-email-mreitz@redhat.com>

Patchwork-id: 66047

O-Subject: [RHEL-7.2 qemu-kvm PATCH 28/42] qcow2: Rebuild refcount structure during check

Bugzilla: 1129893

RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

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

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

BZ: 1129893

The previous commit introduced the "rebuild" variable to qcow2's

implementation of the image consistency check. Now make use of this by

adding a function which creates a completely new refcount structure

based solely on the in-memory information gathered before.

The old refcount structure will be leaked, however. This leak will be

dealt with in a follow-up commit.

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

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

(cherry picked from commit c7c0681bc8a781e0319b7cf969b904dfe50d083e)

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

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

---

 block/qcow2-refcount.c | 311 ++++++++++++++++++++++++++++++++++++++++++++++++-

 1 file changed, 305 insertions(+), 6 deletions(-)

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

index 3d66e7c..651ddb6 100644

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

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

@@ -1660,6 +1660,285 @@ static void compare_refcounts(BlockDriverState *bs, BdrvCheckResult *res,

 }

 /*

+ * Allocates clusters using an in-memory refcount table (IMRT) in contrast to

+ * the on-disk refcount structures.

+ *

+ * On input, *first_free_cluster tells where to start looking, and need not

+ * actually be a free cluster; the returned offset will not be before that

+ * cluster.  On output, *first_free_cluster points to the first gap found, even

+ * if that gap was too small to be used as the returned offset.

+ *

+ * Note that *first_free_cluster is a cluster index whereas the return value is

+ * an offset.

+ */

+static int64_t alloc_clusters_imrt(BlockDriverState *bs,

+                                   int cluster_count,

+                                   uint16_t **refcount_table,

+                                   int64_t *imrt_nb_clusters,

+                                   int64_t *first_free_cluster)

+{

+    BDRVQcowState *s = bs->opaque;

+    int64_t cluster = *first_free_cluster, i;

+    bool first_gap = true;

+    int contiguous_free_clusters;

+

+    /* Starting at *first_free_cluster, find a range of at least cluster_count

+     * continuously free clusters */

+    for (contiguous_free_clusters = 0;

+         cluster < *imrt_nb_clusters &&

+         contiguous_free_clusters < cluster_count;

+         cluster++)

+    {

+        if (!(*refcount_table)[cluster]) {

+            contiguous_free_clusters++;

+            if (first_gap) {

+                /* If this is the first free cluster found, update

+                 * *first_free_cluster accordingly */

+                *first_free_cluster = cluster;

+                first_gap = false;

+            }

+        } else if (contiguous_free_clusters) {

+            contiguous_free_clusters = 0;

+        }

+    }

+

+    /* If contiguous_free_clusters is greater than zero, it contains the number

+     * of continuously free clusters until the current cluster; the first free

+     * cluster in the current "gap" is therefore

+     * cluster - contiguous_free_clusters */

+

+    /* If no such range could be found, grow the in-memory refcount table

+     * accordingly to append free clusters at the end of the image */

+    if (contiguous_free_clusters < cluster_count) {

+        int64_t old_imrt_nb_clusters = *imrt_nb_clusters;

+        uint16_t *new_refcount_table;

+

+        /* contiguous_free_clusters clusters are already empty at the image end;

+         * we need cluster_count clusters; therefore, we have to allocate

+         * cluster_count - contiguous_free_clusters new clusters at the end of

+         * the image (which is the current value of cluster; note that cluster

+         * may exceed old_imrt_nb_clusters if *first_free_cluster pointed beyond

+         * the image end) */

+        *imrt_nb_clusters = cluster + cluster_count - contiguous_free_clusters;

+        new_refcount_table = g_try_realloc(*refcount_table,

+                                           *imrt_nb_clusters *

+                                           sizeof(**refcount_table));

+        if (!new_refcount_table) {

+            *imrt_nb_clusters = old_imrt_nb_clusters;

+            return -ENOMEM;

+        }

+        *refcount_table = new_refcount_table;

+

+        memset(*refcount_table + old_imrt_nb_clusters, 0,

+               (*imrt_nb_clusters - old_imrt_nb_clusters) *

+               sizeof(**refcount_table));

+    }

+

+    /* Go back to the first free cluster */

+    cluster -= contiguous_free_clusters;

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

+        (*refcount_table)[cluster + i] = 1;

+    }

+

+    return cluster << s->cluster_bits;

+}

+

+/*

+ * Creates a new refcount structure based solely on the in-memory information

+ * given through *refcount_table. All necessary allocations will be reflected

+ * in that array.

+ *

+ * On success, the old refcount structure is leaked (it will be covered by the

+ * new refcount structure).

+ */

+static int rebuild_refcount_structure(BlockDriverState *bs,

+                                      BdrvCheckResult *res,

+                                      uint16_t **refcount_table,

+                                      int64_t *nb_clusters)

+{

+    BDRVQcowState *s = bs->opaque;

+    int64_t first_free_cluster = 0, reftable_offset = -1, cluster = 0;

+    int64_t refblock_offset, refblock_start, refblock_index;

+    uint32_t reftable_size = 0;

+    uint64_t *on_disk_reftable = NULL;

+    uint16_t *on_disk_refblock;

+    int i, ret = 0;

+    struct {

+        uint64_t reftable_offset;

+        uint32_t reftable_clusters;

+    } QEMU_PACKED reftable_offset_and_clusters;

+

+    qcow2_cache_empty(bs, s->refcount_block_cache);

+

+write_refblocks:

+    for (; cluster < *nb_clusters; cluster++) {

+        if (!(*refcount_table)[cluster]) {

+            continue;

+        }

+

+        refblock_index = cluster >> s->refcount_block_bits;

+        refblock_start = refblock_index << s->refcount_block_bits;

+

+        /* Don't allocate a cluster in a refblock already written to disk */

+        if (first_free_cluster < refblock_start) {

+            first_free_cluster = refblock_start;

+        }

+        refblock_offset = alloc_clusters_imrt(bs, 1, refcount_table,

+                                              nb_clusters, &first_free_cluster);

+        if (refblock_offset < 0) {

+            fprintf(stderr, "ERROR allocating refblock: %s\n",

+                    strerror(-refblock_offset));

+            res->check_errors++;

+            ret = refblock_offset;

+            goto fail;

+        }

+

+        if (reftable_size <= refblock_index) {

+            uint32_t old_reftable_size = reftable_size;

+            uint64_t *new_on_disk_reftable;

+

+            reftable_size = ROUND_UP((refblock_index + 1) * sizeof(uint64_t),

+                                     s->cluster_size) / sizeof(uint64_t);

+            new_on_disk_reftable = g_try_realloc(on_disk_reftable,

+                                                 reftable_size *

+                                                 sizeof(uint64_t));

+            if (!new_on_disk_reftable) {

+                res->check_errors++;

+                ret = -ENOMEM;

+                goto fail;

+            }

+            on_disk_reftable = new_on_disk_reftable;

+

+            memset(on_disk_reftable + old_reftable_size, 0,

+                   (reftable_size - old_reftable_size) * sizeof(uint64_t));

+

+            /* The offset we have for the reftable is now no longer valid;

+             * this will leak that range, but we can easily fix that by running

+             * a leak-fixing check after this rebuild operation */

+            reftable_offset = -1;

+        }

+        on_disk_reftable[refblock_index] = refblock_offset;

+

+        /* If this is apparently the last refblock (for now), try to squeeze the

+         * reftable in */

+        if (refblock_index == (*nb_clusters - 1) >> s->refcount_block_bits &&

+            reftable_offset < 0)

+        {

+            uint64_t reftable_clusters = size_to_clusters(s, reftable_size *

+                                                          sizeof(uint64_t));

+            reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,

+                                                  refcount_table, nb_clusters,

+                                                  &first_free_cluster);

+            if (reftable_offset < 0) {

+                fprintf(stderr, "ERROR allocating reftable: %s\n",

+                        strerror(-reftable_offset));

+                res->check_errors++;

+                ret = reftable_offset;

+                goto fail;

+            }

+        }

+

+        ret = qcow2_pre_write_overlap_check(bs, 0, refblock_offset,

+                                            s->cluster_size);

+        if (ret < 0) {

+            fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));

+            goto fail;

+        }

+

+        on_disk_refblock = qemu_blockalign0(bs->file, s->cluster_size);

+        for (i = 0; i < s->refcount_block_size &&

+                    refblock_start + i < *nb_clusters; i++)

+        {

+            on_disk_refblock[i] =

+                cpu_to_be16((*refcount_table)[refblock_start + i]);

+        }

+

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

+                         (void *)on_disk_refblock, s->cluster_sectors);

+        qemu_vfree(on_disk_refblock);

+        if (ret < 0) {

+            fprintf(stderr, "ERROR writing refblock: %s\n", strerror(-ret));

+            goto fail;

+        }

+

+        /* Go to the end of this refblock */

+        cluster = refblock_start + s->refcount_block_size - 1;

+    }

+

+    if (reftable_offset < 0) {

+        uint64_t post_refblock_start, reftable_clusters;

+

+        post_refblock_start = ROUND_UP(*nb_clusters, s->refcount_block_size);

+        reftable_clusters = size_to_clusters(s,

+                                             reftable_size * sizeof(uint64_t));

+        /* Not pretty but simple */

+        if (first_free_cluster < post_refblock_start) {

+            first_free_cluster = post_refblock_start;

+        }

+        reftable_offset = alloc_clusters_imrt(bs, reftable_clusters,

+                                              refcount_table, nb_clusters,

+                                              &first_free_cluster);

+        if (reftable_offset < 0) {

+            fprintf(stderr, "ERROR allocating reftable: %s\n",

+                    strerror(-reftable_offset));

+            res->check_errors++;

+            ret = reftable_offset;

+            goto fail;

+        }

+

+        goto write_refblocks;

+    }

+

+    assert(on_disk_reftable);

+

+    for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {

+        cpu_to_be64s(&on_disk_reftable[refblock_index]);

+    }

+

+    ret = qcow2_pre_write_overlap_check(bs, 0, reftable_offset,

+                                        reftable_size * sizeof(uint64_t));

+    if (ret < 0) {

+        fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));

+        goto fail;

+    }

+

+    assert(reftable_size < INT_MAX / sizeof(uint64_t));

+    ret = bdrv_pwrite(bs->file, reftable_offset, on_disk_reftable,

+                      reftable_size * sizeof(uint64_t));

+    if (ret < 0) {

+        fprintf(stderr, "ERROR writing reftable: %s\n", strerror(-ret));

+        goto fail;

+    }

+

+    /* Enter new reftable into the image header */

+    cpu_to_be64w(&reftable_offset_and_clusters.reftable_offset,

+                 reftable_offset);

+    cpu_to_be32w(&reftable_offset_and_clusters.reftable_clusters,

+                 size_to_clusters(s, reftable_size * sizeof(uint64_t)));

+    ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader,

+                                              refcount_table_offset),

+                           &reftable_offset_and_clusters,

+                           sizeof(reftable_offset_and_clusters));

+    if (ret < 0) {

+        fprintf(stderr, "ERROR setting reftable: %s\n", strerror(-ret));

+        goto fail;

+    }

+

+    for (refblock_index = 0; refblock_index < reftable_size; refblock_index++) {

+        be64_to_cpus(&on_disk_reftable[refblock_index]);

+    }

+    s->refcount_table = on_disk_reftable;

+    s->refcount_table_offset = reftable_offset;

+    s->refcount_table_size = reftable_size;

+

+    return 0;

+

+fail:

+    g_free(on_disk_reftable);

+    return ret;

+}

+

+/*

  * Checks an image for refcount consistency.

  *

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

@@ -1669,6 +1948,7 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,

                           BdrvCheckMode fix)

 {

     BDRVQcowState *s = bs->opaque;

+    BdrvCheckResult pre_compare_res;

     int64_t size, highest_cluster, nb_clusters;

     uint16_t *refcount_table = NULL;

     bool rebuild = false;

@@ -1695,14 +1975,33 @@ int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,

         goto fail;

     }

-    compare_refcounts(bs, res, fix, &rebuild, &highest_cluster, refcount_table,

+    /* In case we don't need to rebuild the refcount structure (but want to fix

+     * something), this function is immediately called again, in which case the

+     * result should be ignored */

+    pre_compare_res = *res;

+    compare_refcounts(bs, res, 0, &rebuild, &highest_cluster, refcount_table,

                       nb_clusters);

-    if (rebuild) {

-        fprintf(stderr, "ERROR need to rebuild refcount structures\n");

-        res->check_errors++;

-        /* Just carry on, the rest does not rely on the on-disk refcount

-         * structures */

+    if (rebuild && (fix & BDRV_FIX_ERRORS)) {

+        fprintf(stderr, "Rebuilding refcount structure\n");

+        ret = rebuild_refcount_structure(bs, res, &refcount_table,

+                                         &nb_clusters);

+        if (ret < 0) {

+            goto fail;

+        }

+    } else if (fix) {

+        if (rebuild) {

+            fprintf(stderr, "ERROR need to rebuild refcount structures\n");

+            res->check_errors++;

+            ret = -EIO;

+            goto fail;

+        }

+

+        if (res->leaks || res->corruptions) {

+            *res = pre_compare_res;

+            compare_refcounts(bs, res, fix, &rebuild, &highest_cluster,

+                              refcount_table, nb_clusters);

+        }

     }

     /* check OFLAG_COPIED */

-- 

1.8.3.1