Commit 8b81a7b6 authored by Max Reitz's avatar Max Reitz Committed by Kevin Wolf
Browse files

qcow2-refcount: Snapshot update for zero clusters 



Account for all cluster types in qcow2_update_snapshot_refcounts;
this prevents this function from updating the refcount of unallocated
zero clusters which effectively led to wrong adjustments of the refcount
of cluster 0 (the main qcow2 header). This in turn resulted in images
with (unallocated) zero clusters having a cluster 0 refcount greater
than one after creating a snapshot.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent d4ca092a

block/qcow2-refcount.c

+35 −17
Original line number Diff line number Diff line
@@ -861,11 +861,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, 
            }



            for(j = 0; j < s->l2_size; j++) {

                uint64_t cluster_index;



                offset = be64_to_cpu(l2_table[j]);

                if (offset != 0) {

                old_offset = offset;

                offset &= ~QCOW_OFLAG_COPIED;

                    if (offset & QCOW_OFLAG_COMPRESSED) {



                switch (qcow2_get_cluster_type(offset)) {

                    case QCOW2_CLUSTER_COMPRESSED:

                        nb_csectors = ((offset >> s->csize_shift) &

                                       s->csize_mask) + 1;

                        if (addend != 0) {
@@ -880,8 +883,16 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, 
                        }

                        /* compressed clusters are never modified */

                        refcount = 2;

                    } else {

                        uint64_t cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;

                        break;



                    case QCOW2_CLUSTER_NORMAL:

                    case QCOW2_CLUSTER_ZERO:

                        cluster_index = (offset & L2E_OFFSET_MASK) >> s->cluster_bits;

                        if (!cluster_index) {

                            /* unallocated */

                            refcount = 0;

                            break;

                        }

                        if (addend != 0) {

                            refcount = update_cluster_refcount(bs, cluster_index, addend,

                                                               QCOW2_DISCARD_SNAPSHOT);
@@ -893,6 +904,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, 
                            ret = refcount;

                            goto fail;

                        }

                        break;



                    case QCOW2_CLUSTER_UNALLOCATED:

                        refcount = 0;

                        break;



                    default:

                        abort();

                }



                if (refcount == 1) {
@@ -907,7 +926,6 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs, 
                    qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);

                }

            }

            }



            ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);

            if (ret < 0) {