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[PATCH v11 22/34] qcow2: Add subcluster support to zero_in_l2_slice()
From: |
Alberto Garcia |
Subject: |
[PATCH v11 22/34] qcow2: Add subcluster support to zero_in_l2_slice() |
Date: |
Fri, 10 Jul 2020 18:13:04 +0200 |
The QCOW_OFLAG_ZERO bit that indicates that a cluster reads as
zeroes is only used in standard L2 entries. Extended L2 entries use
individual 'all zeroes' bits for each subcluster.
This must be taken into account when updating the L2 entry and also
when deciding that an existing entry does not need to be updated.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
block/qcow2-cluster.c | 36 +++++++++++++++++++-----------------
1 file changed, 19 insertions(+), 17 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 492296a90f..cb07fd00a1 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1957,7 +1957,6 @@ static int zero_in_l2_slice(BlockDriverState *bs,
uint64_t offset,
int l2_index;
int ret;
int i;
- bool unmap = !!(flags & BDRV_REQ_MAY_UNMAP);
ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
if (ret < 0) {
@@ -1969,28 +1968,31 @@ static int zero_in_l2_slice(BlockDriverState *bs,
uint64_t offset,
assert(nb_clusters <= INT_MAX);
for (i = 0; i < nb_clusters; i++) {
- uint64_t old_offset;
- QCow2ClusterType cluster_type;
+ uint64_t old_l2_entry = get_l2_entry(s, l2_slice, l2_index + i);
+ uint64_t old_l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i);
+ QCow2ClusterType type = qcow2_get_cluster_type(bs, old_l2_entry);
+ bool unmap = (type == QCOW2_CLUSTER_COMPRESSED) ||
+ ((flags & BDRV_REQ_MAY_UNMAP) && qcow2_cluster_is_allocated(type));
+ uint64_t new_l2_entry = unmap ? 0 : old_l2_entry;
+ uint64_t new_l2_bitmap = old_l2_bitmap;
- old_offset = get_l2_entry(s, l2_slice, l2_index + i);
+ if (has_subclusters(s)) {
+ new_l2_bitmap = QCOW_L2_BITMAP_ALL_ZEROES;
+ } else {
+ new_l2_entry |= QCOW_OFLAG_ZERO;
+ }
- /*
- * Minimize L2 changes if the cluster already reads back as
- * zeroes with correct allocation.
- */
- cluster_type = qcow2_get_cluster_type(bs, old_offset);
- if (cluster_type == QCOW2_CLUSTER_ZERO_PLAIN ||
- (cluster_type == QCOW2_CLUSTER_ZERO_ALLOC && !unmap)) {
+ if (old_l2_entry == new_l2_entry && old_l2_bitmap == new_l2_bitmap) {
continue;
}
qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
- if (cluster_type == QCOW2_CLUSTER_COMPRESSED || unmap) {
- set_l2_entry(s, l2_slice, l2_index + i, QCOW_OFLAG_ZERO);
- qcow2_free_any_clusters(bs, old_offset, 1, QCOW2_DISCARD_REQUEST);
- } else {
- uint64_t entry = get_l2_entry(s, l2_slice, l2_index + i);
- set_l2_entry(s, l2_slice, l2_index + i, entry | QCOW_OFLAG_ZERO);
+ if (unmap) {
+ qcow2_free_any_clusters(bs, old_l2_entry, 1,
QCOW2_DISCARD_REQUEST);
+ }
+ set_l2_entry(s, l2_slice, l2_index + i, new_l2_entry);
+ if (has_subclusters(s)) {
+ set_l2_bitmap(s, l2_slice, l2_index + i, new_l2_bitmap);
}
}
--
2.20.1
- [PATCH v11 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), (continued)
- [PATCH v11 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/07/10
- [PATCH v11 15/34] qcow2: Add qcow2_get_subcluster_range_type(), Alberto Garcia, 2020/07/10
- [PATCH v11 19/34] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/07/10
- [PATCH v11 20/34] qcow2: Add subcluster support to calculate_l2_meta(), Alberto Garcia, 2020/07/10
- [PATCH v11 18/34] qcow2: Replace QCOW2_CLUSTER_* with QCOW2_SUBCLUSTER_*, Alberto Garcia, 2020/07/10
- [PATCH v11 09/34] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/07/10
- [PATCH v11 11/34] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/07/10
- [PATCH v11 10/34] qcow2: Add offset_to_sc_index(), Alberto Garcia, 2020/07/10
- [PATCH v11 14/34] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(), Alberto Garcia, 2020/07/10
- [PATCH v11 32/34] qcow2: Allow preallocation and backing files if extended_l2 is set, Alberto Garcia, 2020/07/10
- [PATCH v11 22/34] qcow2: Add subcluster support to zero_in_l2_slice(),
Alberto Garcia <=
- [PATCH v11 24/34] qcow2: Add subcluster support to check_refcounts_l2(), Alberto Garcia, 2020/07/10
- [PATCH v11 25/34] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/07/10
- [PATCH v11 17/34] qcow2: Add cluster type parameter to qcow2_get_host_offset(), Alberto Garcia, 2020/07/10
- [PATCH v11 12/34] qcow2: Add l2_entry_size(), Alberto Garcia, 2020/07/10
- [PATCH v11 26/34] qcow2: Clear the L2 bitmap when allocating a compressed cluster, Alberto Garcia, 2020/07/10
- [PATCH v11 28/34] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes(), Alberto Garcia, 2020/07/10
- [PATCH v11 21/34] qcow2: Add subcluster support to qcow2_get_host_offset(), Alberto Garcia, 2020/07/10
- [PATCH v11 29/34] qcow2: Add subcluster support to qcow2_measure(), Alberto Garcia, 2020/07/10
- [PATCH v11 34/34] iotests: Add tests for qcow2 images with extended L2 entries, Alberto Garcia, 2020/07/10
- [PATCH v11 23/34] qcow2: Add subcluster support to discard_in_l2_slice(), Alberto Garcia, 2020/07/10