From f71c08ea8e60f035485a512fd2af8908567592f0 Mon Sep 17 00:00:00 2001 From: Pavel Butsykin Date: Mon, 18 Sep 2017 15:42:28 +0300 Subject: [PATCH] qcow2: add qcow2_cache_discard 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 Reviewed-by: Max Reitz Reviewed-by: John Snow Message-id: 20170918124230.8152-3-pbutsykin@virtuozzo.com Signed-off-by: Max Reitz --- block/qcow2-cache.c | 26 ++++++++++++++++++++++++++ block/qcow2-refcount.c | 20 ++++++++++++++++++-- block/qcow2.h | 3 +++ 3 files changed, 47 insertions(+), 2 deletions(-) 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 168fc32e7b..8c17c0e3aa 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -861,8 +861,24 @@ 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]) { - update_refcount_discard(bs, cluster_offset, s->cluster_size); + if (refcount == 0) { + 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); + } + + if (s->discard_passthrough[type]) { + update_refcount_discard(bs, cluster_offset, s->cluster_size); + } } } diff --git a/block/qcow2.h b/block/qcow2.h index 96a8d43c17..52c374e9ed 100644 --- a/block/qcow2.h +++ b/block/qcow2.h @@ -649,6 +649,9 @@ 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); /* qcow2-bitmap.c functions */ int qcow2_check_bitmaps_refcounts(BlockDriverState *bs, BdrvCheckResult *res,