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[PATCH v5 21/31] qcow2: Add subcluster support to zero_in_l2_slice()
From: |
Alberto Garcia |
Subject: |
[PATCH v5 21/31] qcow2: Add subcluster support to zero_in_l2_slice() |
Date: |
Tue, 5 May 2020 19:38:21 +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 f500cbfb8e..bf32ed0825 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1913,7 +1913,6 @@ 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) {
@@ -1925,28 +1924,31 @@ 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 v5 08/31] qcow2: Add dummy has_subclusters() function, (continued)
- [PATCH v5 08/31] qcow2: Add dummy has_subclusters() function, Alberto Garcia, 2020/05/05
- [PATCH v5 01/31] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/05/05
- [PATCH v5 03/31] qcow2: Add calculate_l2_meta(), Alberto Garcia, 2020/05/05
- [PATCH v5 11/31] qcow2: Add offset_into_subcluster() and size_to_subclusters(), Alberto Garcia, 2020/05/05
- [PATCH v5 02/31] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/05/05
- [PATCH v5 18/31] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/05/05
- [PATCH v5 24/31] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/05/05
- [PATCH v5 06/31] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/05/05
- [PATCH v5 21/31] qcow2: Add subcluster support to zero_in_l2_slice(),
Alberto Garcia <=
- [PATCH v5 15/31] qcow2: Add qcow2_cluster_is_allocated(), Alberto Garcia, 2020/05/05
- [PATCH v5 17/31] qcow2: Replace QCOW2_CLUSTER_* with QCOW2_SUBCLUSTER_*, Alberto Garcia, 2020/05/05
- [PATCH v5 30/31] qcow2: Add subcluster support to qcow2_measure(), Alberto Garcia, 2020/05/05
- [PATCH v5 13/31] qcow2: Update get/set_l2_entry() and add get/set_l2_bitmap(), Alberto Garcia, 2020/05/05
- [PATCH v5 14/31] qcow2: Add QCow2SubclusterType and qcow2_get_subcluster_type(), Alberto Garcia, 2020/05/05