On 01/26/2018 08:59 AM, Alberto Garcia wrote: > expand_zero_clusters_in_l1() expands zero clusters as a necessary step > to downgrade qcow2 images to a version that doesn't support metadata > zero clusters. This function takes an L1 table (which may or may not > be active) and iterates over all its L2 tables looking for zero > clusters. > > Since we'll be loading L2 slices instead of full tables we need to add > an extra loop that iterates over all slices of each L2 table, and we > should also use the slice size when allocating the buffer used when > the L1 table is not active. > > This function doesn't need any additional changes so apart from that > this patch simply updates the variable name from l2_table to l2_slice. > > Finally, and since we have to touch the bdrv_read() / bdrv_write() > calls anyway, this patch takes the opportunity to replace them with > the byte-based bdrv_pread() / bdrv_pwrite().
This last paragraph could perhaps be split to a separate patch, but
that's more churn so I'm also fine leaving it here.
>
> Signed-off-by: Alberto Garcia <be...@igalia.com>
> ---
> block/qcow2-cluster.c | 52
> ++++++++++++++++++++++++++++-----------------------
> 1 file changed, 29 insertions(+), 23 deletions(-)
Reviewed-by: Eric Blake <ebl...@redhat.com>
> @@ -1905,22 +1908,24 @@ static int
> expand_zero_clusters_in_l1(BlockDriverState *bs, uint64_t *l1_table,
> goto fail;
> }
>
> - {
> + for (slice = 0; slice < n_slices; slice++) {
> + uint64_t slice_offset = l2_offset + slice * slice_size2;
> + bool l2_dirty = false;
> if (is_active_l1) {
> /* get active L2 tables from cache */
> - ret = qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
> - (void **)&l2_table);
> + ret = qcow2_cache_get(bs, s->l2_table_cache, slice_offset,
> + (void **)&l2_slice);
The (void **) cast is probably still necessary (anything can go to
void*, but C gets pickier when going to void**), but...
> } else {
> /* load inactive L2 tables from disk */
> - ret = bdrv_read(bs->file, l2_offset / BDRV_SECTOR_SIZE,
> - (void *)l2_table, s->cluster_sectors);
> + ret = bdrv_pread(bs->file, slice_offset,
> + (void *)l2_slice, slice_size2);
...do we still need this cast to void*?
>
> - ret = bdrv_write(bs->file, l2_offset / BDRV_SECTOR_SIZE,
> - (void *)l2_table, s->cluster_sectors);
> + ret = bdrv_pwrite(bs->file, slice_offset,
> + (void *)l2_slice, slice_size2);
and again here
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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