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[Qemu-block] [PATCH v4 2/4] qcow2: add qcow2_cache_discard
From: |
Pavel Butsykin |
Subject: |
[Qemu-block] [PATCH v4 2/4] qcow2: add qcow2_cache_discard |
Date: |
Tue, 11 Jul 2017 15:40:22 +0300 |
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 <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
---
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 7c06061aae..0141c9cbe7 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -767,6 +767,20 @@ 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);
}
}
diff --git a/block/qcow2.h b/block/qcow2.h
index 87b15eb4aa..bf6691dbd0 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -604,5 +604,8 @@ int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c,
uint64_t offset,
int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table);
void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table);
+void *qcow2_cache_is_table_offset(BlockDriverState *bs, Qcow2Cache *c,
+ uint64_t offset);
+void qcow2_cache_discard(BlockDriverState *bs, Qcow2Cache *c, void *table);
#endif
--
2.13.0
- [Qemu-block] [PATCH v4 0/4] Add shrink image for qcow2, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 3/4] qcow2: add shrink image support, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 1/4] qemu-img: add --shrink flag for resize, Pavel Butsykin, 2017/07/11
- [Qemu-block] [PATCH v4 2/4] qcow2: add qcow2_cache_discard,
Pavel Butsykin <=
- [Qemu-block] [PATCH v4 4/4] qemu-iotests: add shrinking image test, Pavel Butsykin, 2017/07/11
- Re: [Qemu-block] [Qemu-devel] [PATCH v4 0/4] Add shrink image for qcow2, no-reply, 2017/07/11
- Re: [Qemu-block] [Qemu-devel] [PATCH v4 0/4] Add shrink image for qcow2, no-reply, 2017/07/11
- Re: [Qemu-block] [PATCH v4 0/4] Add shrink image for qcow2, Max Reitz, 2017/07/11