/* * 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 "qemu/osdep.h" #include "block/block-io.h" #include "qemu/memalign.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; int table_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(Qcow2Cache *c, int table) { return (uint8_t *) c->table_array + (size_t) table * c->table_size; } static inline int qcow2_cache_get_table_idx(Qcow2Cache *c, void *table) { ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array; int idx = table_offset / c->table_size; assert(idx >= 0 && idx < c->size && table_offset % c->table_size == 0); return idx; } static inline const char *qcow2_cache_get_name(BDRVQcow2State *s, Qcow2Cache *c) { if (c == s->refcount_block_cache) { return "refcount block"; } else if (c == s->l2_table_cache) { return "L2 table"; } else { /* Do not abort, because this is not critical */ return "unknown"; } } static void qcow2_cache_table_release(Qcow2Cache *c, int i, int num_tables) { /* Using MADV_DONTNEED to discard memory is a Linux-specific feature */ #ifdef CONFIG_LINUX void *t = qcow2_cache_get_table_addr(c, i); int align = qemu_real_host_page_size(); size_t mem_size = (size_t) c->table_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 (mem_size > offset && length > 0) { madvise((uint8_t *) t + offset, length, 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(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(c, i - to_clean, to_clean); } } c->cache_clean_lru_counter = c->lru_counter; } Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables, unsigned table_size) { BDRVQcow2State *s = bs->opaque; Qcow2Cache *c; assert(num_tables > 0); assert(is_power_of_2(table_size)); assert(table_size >= (1 << MIN_CLUSTER_BITS)); assert(table_size <= s->cluster_size); c = g_new0(Qcow2Cache, 1); c->size = num_tables; c->table_size = table_size; c->entries = g_try_new0(Qcow2CachedTable, num_tables); c->table_array = qemu_try_blockalign(bs->file->bs, (size_t) num_tables * c->table_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(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 GRAPH_RDLOCK 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 GRAPH_RDLOCK 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, c->table_size, false); } else if (c == s->l2_table_cache) { ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2, c->entries[i].offset, c->table_size, false); } else { ret = qcow2_pre_write_overlap_check(bs, 0, c->entries[i].offset, c->table_size, 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->table_size, qcow2_cache_get_table_addr(c, i), 0); if (ret < 0) { return ret; } c->entries[i].dirty = false; return 0; } int qcow2_cache_write(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; } } return result; } int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c) { int result = qcow2_cache_write(bs, c); if (result == 0) { int 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(c, 0, c->size); c->lru_counter = 0; return 0; } static int GRAPH_RDLOCK 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; assert(offset != 0); trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache, offset, read_from_disk); if (!QEMU_IS_ALIGNED(offset, c->table_size)) { qcow2_signal_corruption(bs, true, -1, -1, "Cannot get entry from %s " "cache: Offset %#" PRIx64 " is unaligned", qcow2_cache_get_name(s, c), offset); return -EIO; } /* Check if the table is already cached */ i = lookup_index = (offset / c->table_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, offset, c->table_size, qcow2_cache_get_table_addr(c, i), 0); 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(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(Qcow2Cache *c, void **table) { int i = qcow2_cache_get_table_idx(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(Qcow2Cache *c, void *table) { int i = qcow2_cache_get_table_idx(c, table); assert(c->entries[i].offset != 0); c->entries[i].dirty = true; } void *qcow2_cache_is_table_offset(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(c, i); } } return NULL; } void qcow2_cache_discard(Qcow2Cache *c, void *table) { int i = qcow2_cache_get_table_idx(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(c, i, 1); }