diff options
Diffstat (limited to 'contrib/qemu/block/qcow2-cache.c')
| -rw-r--r-- | contrib/qemu/block/qcow2-cache.c | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/contrib/qemu/block/qcow2-cache.c b/contrib/qemu/block/qcow2-cache.c new file mode 100644 index 00000000000..2f3114ecc24 --- /dev/null +++ b/contrib/qemu/block/qcow2-cache.c @@ -0,0 +1,323 @@ +/* + * 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 { + void* table; + int64_t offset; + bool dirty; + int cache_hits; + int ref; +} Qcow2CachedTable; + +struct Qcow2Cache { + Qcow2CachedTable* entries; + struct Qcow2Cache* depends; + int size; + bool depends_on_flush; +}; + +Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables) +{ + BDRVQcowState *s = bs->opaque; + Qcow2Cache *c; + int i; + + c = g_malloc0(sizeof(*c)); + c->size = num_tables; + c->entries = g_malloc0(sizeof(*c->entries) * num_tables); + + for (i = 0; i < c->size; i++) { + c->entries[i].table = qemu_blockalign(bs, s->cluster_size); + } + + 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->entries[i].table); + } + + 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) { + 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, c->entries[i].table, + 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; +} + +static int qcow2_cache_find_entry_to_replace(Qcow2Cache *c) +{ + int i; + int min_count = INT_MAX; + int min_index = -1; + + + for (i = 0; i < c->size; i++) { + if (c->entries[i].ref) { + continue; + } + + if (c->entries[i].cache_hits < min_count) { + min_index = i; + min_count = c->entries[i].cache_hits; + } + + /* Give newer hits priority */ + /* TODO Check how to optimize the replacement strategy */ + c->entries[i].cache_hits /= 2; + } + + if (min_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(); + } + return min_index; +} + +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; + + trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache, + offset, read_from_disk); + + /* Check if the table is already cached */ + for (i = 0; i < c->size; i++) { + if (c->entries[i].offset == offset) { + goto found; + } + } + + /* If not, write a table back and replace it */ + i = qcow2_cache_find_entry_to_replace(c); + 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, c->entries[i].table, s->cluster_size); + if (ret < 0) { + return ret; + } + } + + /* Give the table some hits for the start so that it won't be replaced + * immediately. The number 32 is completely arbitrary. */ + c->entries[i].cache_hits = 32; + c->entries[i].offset = offset; + + /* And return the right table */ +found: + c->entries[i].cache_hits++; + c->entries[i].ref++; + *table = c->entries[i].table; + + 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); +} + +int qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table) +{ + int i; + + for (i = 0; i < c->size; i++) { + if (c->entries[i].table == *table) { + goto found; + } + } + return -ENOENT; + +found: + c->entries[i].ref--; + *table = NULL; + + assert(c->entries[i].ref >= 0); + return 0; +} + +void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table) +{ + int i; + + for (i = 0; i < c->size; i++) { + if (c->entries[i].table == table) { + goto found; + } + } + abort(); + +found: + c->entries[i].dirty = true; +} |