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[PATCH v7 22/32] qcow2: Add subcluster support to zero_in_l2_slice()
From: |
Alberto Garcia |
Subject: |
[PATCH v7 22/32] qcow2: Add subcluster support to zero_in_l2_slice() |
Date: |
Mon, 25 May 2020 20:08:47 +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 <address@hidden>
---
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 v7 07/32] qcow2: Document the Extended L2 Entries feature, (continued)
- [PATCH v7 07/32] qcow2: Document the Extended L2 Entries feature, Alberto Garcia, 2020/05/25
- [PATCH v7 28/32] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes(), Alberto Garcia, 2020/05/25
- [PATCH v7 15/32] qcow2: Add qcow2_get_subcluster_range_type(), Alberto Garcia, 2020/05/25
- [PATCH v7 06/32] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/05/25
- [PATCH v7 09/32] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/05/25
- [PATCH v7 23/32] qcow2: Add subcluster support to discard_in_l2_slice(), Alberto Garcia, 2020/05/25
- [PATCH v7 01/32] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/05/25
- [PATCH v7 22/32] qcow2: Add subcluster support to zero_in_l2_slice(),
Alberto Garcia <=
- [PATCH v7 13/32] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2020/05/25
- [PATCH v7 16/32] qcow2: Add qcow2_cluster_is_allocated(), Alberto Garcia, 2020/05/25
- [PATCH v7 04/32] qcow2: Split cluster_needs_cow() out of count_cow_clusters(), Alberto Garcia, 2020/05/25
- [PATCH v7 14/32] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(), Alberto Garcia, 2020/05/25
- [PATCH v7 08/32] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2020/05/25
- [PATCH v7 10/32] qcow2: Add offset_to_sc_index(), Alberto Garcia, 2020/05/25