Whenever l2/refcount table clusters are discarded from the file we can
automatically drop unnecessary content of the cache tables. This reduces
the chance of eviction useful cache data and eliminates inconsistent data
in the cache with the data in the file.
Signed-off-by: Pavel Butsykin <pbutsy...@virtuozzo.com>
Reviewed-by: Max Reitz <mre...@redhat.com>
---
block/qcow2-cache.c | 26 ++++++++++++++++++++++++++
block/qcow2-refcount.c | 14 ++++++++++++++
block/qcow2.h | 3 +++
3 files changed, 43 insertions(+)
diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c
index 1d25147392..75746a7f43 100644
--- a/block/qcow2-cache.c
+++ b/block/qcow2-cache.c
@@ -411,3 +411,29 @@ void qcow2_cache_entry_mark_dirty(BlockDriverState *bs,
Qcow2Cache *c,
assert(c->entries[i].offset != 0);
c->entries[i].dirty = true;
}
+
+void *qcow2_cache_is_table_offset(BlockDriverState *bs, Qcow2Cache *c,
+ uint64_t offset)
+{
+ int i;
+
+ for (i = 0; i < c->size; i++) {
+ if (c->entries[i].offset == offset) {
+ return qcow2_cache_get_table_addr(bs, c, i);
+ }
+ }
+ return NULL;
+}
+
+void qcow2_cache_discard(BlockDriverState *bs, Qcow2Cache *c, void *table)
+{
+ int i = qcow2_cache_get_table_idx(bs, c, table);
+
+ assert(c->entries[i].ref == 0);
+
+ c->entries[i].offset = 0;
+ c->entries[i].lru_counter = 0;
+ c->entries[i].dirty = false;
+
+ qcow2_cache_table_release(bs, c, i, 1);
+}
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index c9b0dcb4f3..8050db4544 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -862,6 +862,20 @@ static int QEMU_WARN_UNUSED_RESULT
update_refcount(BlockDriverState *bs,
s->set_refcount(refcount_block, block_index, refcount);
if (refcount == 0 && s->discard_passthrough[type]) {
+ void *table;
+
+ table = qcow2_cache_is_table_offset(bs, s->refcount_block_cache,
+ offset);
+ if (table != NULL) {
+ qcow2_cache_put(bs, s->refcount_block_cache, &refcount_block);
+ qcow2_cache_discard(bs, s->refcount_block_cache, table);
+ }
+
+ table = qcow2_cache_is_table_offset(bs, s->l2_table_cache, offset);
+ if (table != NULL) {
+ qcow2_cache_discard(bs, s->l2_table_cache, table);
+ }
+
update_refcount_discard(bs, cluster_offset, s->cluster_size);
}
}
