diff options
Diffstat (limited to 'src/block/qcow2-cache.c')
-rw-r--r-- | src/block/qcow2-cache.c | 412 |
1 files changed, 412 insertions, 0 deletions
diff --git a/src/block/qcow2-cache.c b/src/block/qcow2-cache.c new file mode 100644 index 0000000..86dd7f2 --- /dev/null +++ b/src/block/qcow2-cache.c @@ -0,0 +1,412 @@ +/* + * 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. + */ + +/* Needed for CONFIG_MADVISE */ +#include "config-host.h" + +#if defined(CONFIG_MADVISE) || defined(CONFIG_POSIX_MADVISE) +#include <sys/mman.h> +#endif + +#include "block/block_int.h" +#include "qemu-common.h" +#include "qemu/osdep.h" +#include "qcow2.h" +#include "trace.h" + +typedef struct Qcow2CachedTable { + int64_t offset; + uint64_t lru_counter; + int ref; + bool dirty; +} Qcow2CachedTable; + +struct Qcow2Cache { + Qcow2CachedTable *entries; + struct Qcow2Cache *depends; + int size; + bool depends_on_flush; + void *table_array; + uint64_t lru_counter; + uint64_t cache_clean_lru_counter; +}; + +static inline void *qcow2_cache_get_table_addr(BlockDriverState *bs, + Qcow2Cache *c, int table) +{ + BDRVQcow2State *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) +{ + BDRVQcow2State *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; +} + +static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c, + int i, int num_tables) +{ +#if QEMU_MADV_DONTNEED != QEMU_MADV_INVALID + BDRVQcow2State *s = bs->opaque; + void *t = qcow2_cache_get_table_addr(bs, c, i); + int align = getpagesize(); + size_t mem_size = (size_t) s->cluster_size * num_tables; + size_t offset = QEMU_ALIGN_UP((uintptr_t) t, align) - (uintptr_t) t; + size_t length = QEMU_ALIGN_DOWN(mem_size - offset, align); + if (length > 0) { + qemu_madvise((uint8_t *) t + offset, length, QEMU_MADV_DONTNEED); + } +#endif +} + +static inline bool can_clean_entry(Qcow2Cache *c, int i) +{ + Qcow2CachedTable *t = &c->entries[i]; + return t->ref == 0 && !t->dirty && t->offset != 0 && + t->lru_counter <= c->cache_clean_lru_counter; +} + +void qcow2_cache_clean_unused(BlockDriverState *bs, Qcow2Cache *c) +{ + int i = 0; + while (i < c->size) { + int to_clean = 0; + + /* Skip the entries that we don't need to clean */ + while (i < c->size && !can_clean_entry(c, i)) { + i++; + } + + /* And count how many we can clean in a row */ + while (i < c->size && can_clean_entry(c, i)) { + c->entries[i].offset = 0; + c->entries[i].lru_counter = 0; + i++; + to_clean++; + } + + if (to_clean > 0) { + qcow2_cache_table_release(bs, c, i - to_clean, to_clean); + } + } + + c->cache_clean_lru_counter = c->lru_counter; +} + +Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables) +{ + BDRVQcow2State *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->bs, + (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) +{ + BDRVQcow2State *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->bs); + 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->bs, 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) +{ + BDRVQcow2State *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->bs); + 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; + } + + qcow2_cache_table_release(bs, c, 0, c->size); + + 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) +{ + BDRVQcow2State *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); + + 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->bs, 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; +} |