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[PATCH v9 22/34] qcow2: Add subcluster support to zero_in_l2_slice()
From: |
Alberto Garcia |
Subject: |
[PATCH v9 22/34] qcow2: Add subcluster support to zero_in_l2_slice() |
Date: |
Sun, 28 Jun 2020 13:02:31 +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>
---
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 2f3bd3a882..4e59bbd545 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1956,7 +1956,6 @@ 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) {
@@ -1968,28 +1967,31 @@ 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 v9 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), (continued)
- [PATCH v9 04/34] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/06/28
- [PATCH v9 06/34] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/06/28
- [PATCH v9 10/34] qcow2: Add offset_to_sc_index(), Alberto Garcia, 2020/06/28
- [PATCH v9 08/34] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2020/06/28
- [PATCH v9 05/34] qcow2: Process QCOW2_CLUSTER_ZERO_ALLOC clusters in handle_copied(), Alberto Garcia, 2020/06/28
- [PATCH v9 02/34] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/06/28
- [PATCH v9 07/34] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/06/28
- [PATCH v9 13/34] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2020/06/28
- [PATCH v9 24/34] qcow2: Add subcluster support to check_refcounts_l2(), Alberto Garcia, 2020/06/28
- [PATCH v9 29/34] qcow2: Add subcluster support to qcow2_measure(), Alberto Garcia, 2020/06/28
- [PATCH v9 22/34] qcow2: Add subcluster support to zero_in_l2_slice(),
Alberto Garcia <=
- [PATCH v9 19/34] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/06/28
- [PATCH v9 09/34] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/06/28
- [PATCH v9 11/34] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/06/28
- [PATCH v9 16/34] qcow2: Add qcow2_cluster_is_allocated(), Alberto Garcia, 2020/06/28
- [PATCH v9 30/34] qcow2: Add prealloc field to QCowL2Meta, Alberto Garcia, 2020/06/28
- [PATCH v9 25/34] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/06/28
- [PATCH v9 01/34] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/06/28
- [PATCH v9 33/34] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters, Alberto Garcia, 2020/06/28
- [PATCH v9 17/34] qcow2: Add cluster type parameter to qcow2_get_host_offset(), Alberto Garcia, 2020/06/28
- [PATCH v9 20/34] qcow2: Add subcluster support to calculate_l2_meta(), Alberto Garcia, 2020/06/28