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qemu/block/qcow2-cache.c

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/*
* L2/refcount table cache for the QCOW2 format
*
* Copyright (c) 2010 Kevin Wolf <kwolf@redhat.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "block/block_int.h"
#include "qemu-common.h"
#include "qcow2.h"
#include "trace.h"
typedef struct Qcow2CachedTable {
int64_t offset;
bool dirty;
uint64_t lru_counter;
int ref;
} Qcow2CachedTable;
struct Qcow2Cache {
Qcow2CachedTable *entries;
struct Qcow2Cache *depends;
int size;
bool depends_on_flush;
void *table_array;
uint64_t lru_counter;
};
static inline void *qcow2_cache_get_table_addr(BlockDriverState *bs,
Qcow2Cache *c, int table)
{
BDRVQcowState *s = bs->opaque;
return (uint8_t *) c->table_array + (size_t) table * s->cluster_size;
}
static inline int qcow2_cache_get_table_idx(BlockDriverState *bs,
Qcow2Cache *c, void *table)
{
BDRVQcowState *s = bs->opaque;
ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array;
int idx = table_offset / s->cluster_size;
assert(idx >= 0 && idx < c->size && table_offset % s->cluster_size == 0);
return idx;
}
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
{
BDRVQcowState *s = bs->opaque;
Qcow2Cache *c;
c = g_new0(Qcow2Cache, 1);
c->size = num_tables;
c->entries = g_try_new0(Qcow2CachedTable, num_tables);
c->table_array = qemu_try_blockalign(bs->file,
(size_t) num_tables * s->cluster_size);
if (!c->entries || !c->table_array) {
qemu_vfree(c->table_array);
g_free(c->entries);
g_free(c);
c = NULL;
}
return c;
}
int qcow2_cache_destroy(BlockDriverState *bs, Qcow2Cache *c)
{
int i;
for (i = 0; i < c->size; i++) {
assert(c->entries[i].ref == 0);
}
qemu_vfree(c->table_array);
g_free(c->entries);
g_free(c);
return 0;
}
static int qcow2_cache_flush_dependency(BlockDriverState *bs, Qcow2Cache *c)
{
int ret;
ret = qcow2_cache_flush(bs, c->depends);
if (ret < 0) {
return ret;
}
c->depends = NULL;
c->depends_on_flush = false;
return 0;
}
static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
{
BDRVQcowState *s = bs->opaque;
int ret = 0;
if (!c->entries[i].dirty || !c->entries[i].offset) {
return 0;
}
trace_qcow2_cache_entry_flush(qemu_coroutine_self(),
c == s->l2_table_cache, i);
if (c->depends) {
ret = qcow2_cache_flush_dependency(bs, c);
} else if (c->depends_on_flush) {
ret = bdrv_flush(bs->file);
if (ret >= 0) {
c->depends_on_flush = false;
}
}
if (ret < 0) {
return ret;
}
if (c == s->refcount_block_cache) {
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_REFCOUNT_BLOCK,
c->entries[i].offset, s->cluster_size);
} else if (c == s->l2_table_cache) {
ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2,
c->entries[i].offset, s->cluster_size);
} else {
ret = qcow2_pre_write_overlap_check(bs, 0,
c->entries[i].offset, s->cluster_size);
}
if (ret < 0) {
return ret;
}
if (c == s->refcount_block_cache) {
BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
} else if (c == s->l2_table_cache) {
BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE);
}
ret = bdrv_pwrite(bs->file, c->entries[i].offset,
qcow2_cache_get_table_addr(bs, c, i), s->cluster_size);
if (ret < 0) {
return ret;
}
c->entries[i].dirty = false;
return 0;
}
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
{
BDRVQcowState *s = bs->opaque;
int result = 0;
int ret;
int i;
trace_qcow2_cache_flush(qemu_coroutine_self(), c == s->l2_table_cache);
for (i = 0; i < c->size; i++) {
ret = qcow2_cache_entry_flush(bs, c, i);
if (ret < 0 && result != -ENOSPC) {
result = ret;
}
}
if (result == 0) {
ret = bdrv_flush(bs->file);
if (ret < 0) {
result = ret;
}
}
return result;
}
int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
Qcow2Cache *dependency)
{
int ret;
if (dependency->depends) {
ret = qcow2_cache_flush_dependency(bs, dependency);
if (ret < 0) {
return ret;
}
}
if (c->depends && (c->depends != dependency)) {
ret = qcow2_cache_flush_dependency(bs, c);
if (ret < 0) {
return ret;
}
}
c->depends = dependency;
return 0;
}
void qcow2_cache_depends_on_flush(Qcow2Cache *c)
{
c->depends_on_flush = true;
}
int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c)
{
int ret, i;
ret = qcow2_cache_flush(bs, c);
if (ret < 0) {
return ret;
}
for (i = 0; i < c->size; i++) {
assert(c->entries[i].ref == 0);
c->entries[i].offset = 0;
c->entries[i].lru_counter = 0;
}
c->lru_counter = 0;
return 0;
}
static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
uint64_t offset, void **table, bool read_from_disk)
{
BDRVQcowState *s = bs->opaque;
int i;
int ret;
int lookup_index;
uint64_t min_lru_counter = UINT64_MAX;
int min_lru_index = -1;
trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache,
offset, read_from_disk);
/* Check if the table is already cached */
i = lookup_index = (offset / s->cluster_size * 4) % c->size;
do {
const Qcow2CachedTable *t = &c->entries[i];
if (t->offset == offset) {
goto found;
}
if (t->ref == 0 && t->lru_counter < min_lru_counter) {
min_lru_counter = t->lru_counter;
min_lru_index = i;
}
if (++i == c->size) {
i = 0;
}
} while (i != lookup_index);
if (min_lru_index == -1) {
/* This can't happen in current synchronous code, but leave the check
* here as a reminder for whoever starts using AIO with the cache */
abort();
}
/* Cache miss: write a table back and replace it */
i = min_lru_index;
trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(),
c == s->l2_table_cache, i);
if (i < 0) {
return i;
}
ret = qcow2_cache_entry_flush(bs, c, i);
if (ret < 0) {
return ret;
}
trace_qcow2_cache_get_read(qemu_coroutine_self(),
c == s->l2_table_cache, i);
c->entries[i].offset = 0;
if (read_from_disk) {
if (c == s->l2_table_cache) {
BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD);
}
ret = bdrv_pread(bs->file, offset, qcow2_cache_get_table_addr(bs, c, i),
s->cluster_size);
if (ret < 0) {
return ret;
}
}
c->entries[i].offset = offset;
/* And return the right table */
found:
c->entries[i].ref++;
*table = qcow2_cache_get_table_addr(bs, c, i);
trace_qcow2_cache_get_done(qemu_coroutine_self(),
c == s->l2_table_cache, i);
return 0;
}
int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table)
{
return qcow2_cache_do_get(bs, c, offset, table, true);
}
int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table)
{
return qcow2_cache_do_get(bs, c, offset, table, false);
}
void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table)
{
int i = qcow2_cache_get_table_idx(bs, c, *table);
c->entries[i].ref--;
*table = NULL;
if (c->entries[i].ref == 0) {
c->entries[i].lru_counter = ++c->lru_counter;
}
assert(c->entries[i].ref >= 0);
}
void qcow2_cache_entry_mark_dirty(BlockDriverState *bs, Qcow2Cache *c,
void *table)
{
int i = qcow2_cache_get_table_idx(bs, c, table);
assert(c->entries[i].offset != 0);
c->entries[i].dirty = true;
}
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