Commit 8c44dfbc authored by Max Reitz's avatar Max Reitz Committed by Kevin Wolf
Browse files

qcow2: Rewrite qcow2_alloc_bytes() 



qcow2_alloc_bytes() is a function with insufficient error handling and
an unnecessary goto. This patch rewrites it.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 8e8cb375

block/qcow2-refcount.c

+39 −39
Original line number Diff line number Diff line
@@ -759,54 +759,54 @@ int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset, 
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)

{

    BDRVQcowState *s = bs->opaque;

    int64_t offset, cluster_offset;

    int free_in_cluster;

    int64_t offset;

    size_t free_in_cluster;

    int ret;



    BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);

    assert(size > 0 && size <= s->cluster_size);

    if (s->free_byte_offset == 0) {

        offset = qcow2_alloc_clusters(bs, s->cluster_size);

        if (offset < 0) {

            return offset;

    assert(!s->free_byte_offset || offset_into_cluster(s, s->free_byte_offset));



    offset = s->free_byte_offset;



    if (offset) {

        int refcount = qcow2_get_refcount(bs, offset >> s->cluster_bits);

        if (refcount < 0) {

            return refcount;

        }

        s->free_byte_offset = offset;



        if (refcount == 0xffff) {

            offset = 0;

        }

 redo:

    free_in_cluster = s->cluster_size -

        offset_into_cluster(s, s->free_byte_offset);

    if (size <= free_in_cluster) {

        /* enough space in current cluster */

        offset = s->free_byte_offset;

        s->free_byte_offset += size;

        free_in_cluster -= size;

        if (free_in_cluster == 0)

            s->free_byte_offset = 0;

        if (offset_into_cluster(s, offset) != 0)

            qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,

                                          QCOW2_DISCARD_NEVER);

    } else {

        offset = qcow2_alloc_clusters(bs, s->cluster_size);

        if (offset < 0) {

            return offset;

    }

        cluster_offset = start_of_cluster(s, s->free_byte_offset);

        if ((cluster_offset + s->cluster_size) == offset) {

            /* we are lucky: contiguous data */

            offset = s->free_byte_offset;

            qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits, 1,

                                          QCOW2_DISCARD_NEVER);

            s->free_byte_offset += size;

        } else {

            s->free_byte_offset = offset;

            goto redo;



    free_in_cluster = s->cluster_size - offset_into_cluster(s, offset);

    if (!offset || free_in_cluster < size) {

        int64_t new_cluster = alloc_clusters_noref(bs, s->cluster_size);

        if (new_cluster < 0) {

            return new_cluster;

        }



        if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) {

            offset = new_cluster;

        }

    }



    /* The cluster refcount was incremented, either by qcow2_alloc_clusters()

     * or explicitly by qcow2_update_cluster_refcount().  Refcount blocks must

     * be flushed before the caller's L2 table updates.

     */

    assert(offset);

    ret = update_refcount(bs, offset, size, 1, QCOW2_DISCARD_NEVER);

    if (ret < 0) {

        return ret;

    }



    /* The cluster refcount was incremented; refcount blocks must be flushed

     * before the caller's L2 table updates. */

    qcow2_cache_set_dependency(bs, s->l2_table_cache, s->refcount_block_cache);



    s->free_byte_offset = offset + size;

    if (!offset_into_cluster(s, s->free_byte_offset)) {

        s->free_byte_offset = 0;

    }



    return offset;

}