qemu/block/qcow2.h
Stefan Hajnoczi bfe8043e92 qcow2: implement lazy refcounts
Lazy refcounts is a performance optimization for qcow2 that postpones
refcount metadata updates and instead marks the image dirty.  In the
case of crash or power failure the image will be left in a dirty state
and repaired next time it is opened.

Reducing metadata I/O is important for cache=writethrough and
cache=directsync because these modes guarantee that data is on disk
after each write (hence we cannot take advantage of caching updates in
RAM).  Refcount metadata is not needed for guest->file block address
translation and therefore does not need to be on-disk at the time of
write completion - this is the motivation behind the lazy refcount
optimization.

The lazy refcount optimization must be enabled at image creation time:

  qemu-img create -f qcow2 -o compat=1.1,lazy_refcounts=on a.qcow2 10G
  qemu-system-x86_64 -drive if=virtio,file=a.qcow2,cache=writethrough

Update qemu-iotests 031 and 036 since the extension header size changes
when we add feature bit table entries.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-08-06 22:39:14 +02:00

337 lines
10 KiB
C

/*
* Block driver for the QCOW version 2 format
*
* Copyright (c) 2004-2006 Fabrice Bellard
*
* 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.
*/
#ifndef BLOCK_QCOW2_H
#define BLOCK_QCOW2_H
#include "aes.h"
#include "qemu-coroutine.h"
//#define DEBUG_ALLOC
//#define DEBUG_ALLOC2
//#define DEBUG_EXT
#define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)
#define QCOW_CRYPT_NONE 0
#define QCOW_CRYPT_AES 1
#define QCOW_MAX_CRYPT_CLUSTERS 32
/* indicate that the refcount of the referenced cluster is exactly one. */
#define QCOW_OFLAG_COPIED (1LL << 63)
/* indicate that the cluster is compressed (they never have the copied flag) */
#define QCOW_OFLAG_COMPRESSED (1LL << 62)
/* The cluster reads as all zeros */
#define QCOW_OFLAG_ZERO (1LL << 0)
#define REFCOUNT_SHIFT 1 /* refcount size is 2 bytes */
#define MIN_CLUSTER_BITS 9
#define MAX_CLUSTER_BITS 21
#define L2_CACHE_SIZE 16
/* Must be at least 4 to cover all cases of refcount table growth */
#define REFCOUNT_CACHE_SIZE 4
#define DEFAULT_CLUSTER_SIZE 65536
typedef struct QCowHeader {
uint32_t magic;
uint32_t version;
uint64_t backing_file_offset;
uint32_t backing_file_size;
uint32_t cluster_bits;
uint64_t size; /* in bytes */
uint32_t crypt_method;
uint32_t l1_size; /* XXX: save number of clusters instead ? */
uint64_t l1_table_offset;
uint64_t refcount_table_offset;
uint32_t refcount_table_clusters;
uint32_t nb_snapshots;
uint64_t snapshots_offset;
/* The following fields are only valid for version >= 3 */
uint64_t incompatible_features;
uint64_t compatible_features;
uint64_t autoclear_features;
uint32_t refcount_order;
uint32_t header_length;
} QCowHeader;
typedef struct QCowSnapshot {
uint64_t l1_table_offset;
uint32_t l1_size;
char *id_str;
char *name;
uint64_t disk_size;
uint64_t vm_state_size;
uint32_t date_sec;
uint32_t date_nsec;
uint64_t vm_clock_nsec;
} QCowSnapshot;
struct Qcow2Cache;
typedef struct Qcow2Cache Qcow2Cache;
typedef struct Qcow2UnknownHeaderExtension {
uint32_t magic;
uint32_t len;
QLIST_ENTRY(Qcow2UnknownHeaderExtension) next;
uint8_t data[];
} Qcow2UnknownHeaderExtension;
enum {
QCOW2_FEAT_TYPE_INCOMPATIBLE = 0,
QCOW2_FEAT_TYPE_COMPATIBLE = 1,
QCOW2_FEAT_TYPE_AUTOCLEAR = 2,
};
/* Incompatible feature bits */
enum {
QCOW2_INCOMPAT_DIRTY_BITNR = 0,
QCOW2_INCOMPAT_DIRTY = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
QCOW2_INCOMPAT_MASK = QCOW2_INCOMPAT_DIRTY,
};
/* Compatible feature bits */
enum {
QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR = 0,
QCOW2_COMPAT_LAZY_REFCOUNTS = 1 << QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,
QCOW2_COMPAT_FEAT_MASK = QCOW2_COMPAT_LAZY_REFCOUNTS,
};
typedef struct Qcow2Feature {
uint8_t type;
uint8_t bit;
char name[46];
} QEMU_PACKED Qcow2Feature;
typedef struct BDRVQcowState {
int cluster_bits;
int cluster_size;
int cluster_sectors;
int l2_bits;
int l2_size;
int l1_size;
int l1_vm_state_index;
int csize_shift;
int csize_mask;
uint64_t cluster_offset_mask;
uint64_t l1_table_offset;
uint64_t *l1_table;
Qcow2Cache* l2_table_cache;
Qcow2Cache* refcount_block_cache;
uint8_t *cluster_cache;
uint8_t *cluster_data;
uint64_t cluster_cache_offset;
QLIST_HEAD(QCowClusterAlloc, QCowL2Meta) cluster_allocs;
uint64_t *refcount_table;
uint64_t refcount_table_offset;
uint32_t refcount_table_size;
int64_t free_cluster_index;
int64_t free_byte_offset;
CoMutex lock;
uint32_t crypt_method; /* current crypt method, 0 if no key yet */
uint32_t crypt_method_header;
AES_KEY aes_encrypt_key;
AES_KEY aes_decrypt_key;
uint64_t snapshots_offset;
int snapshots_size;
int nb_snapshots;
QCowSnapshot *snapshots;
int flags;
int qcow_version;
uint64_t incompatible_features;
uint64_t compatible_features;
uint64_t autoclear_features;
size_t unknown_header_fields_size;
void* unknown_header_fields;
QLIST_HEAD(, Qcow2UnknownHeaderExtension) unknown_header_ext;
} BDRVQcowState;
/* XXX: use std qcow open function ? */
typedef struct QCowCreateState {
int cluster_size;
int cluster_bits;
uint16_t *refcount_block;
uint64_t *refcount_table;
int64_t l1_table_offset;
int64_t refcount_table_offset;
int64_t refcount_block_offset;
} QCowCreateState;
struct QCowAIOCB;
/* XXX This could be private for qcow2-cluster.c */
typedef struct QCowL2Meta
{
uint64_t offset;
uint64_t cluster_offset;
uint64_t alloc_offset;
int n_start;
int nb_available;
int nb_clusters;
CoQueue dependent_requests;
QLIST_ENTRY(QCowL2Meta) next_in_flight;
} QCowL2Meta;
enum {
QCOW2_CLUSTER_UNALLOCATED,
QCOW2_CLUSTER_NORMAL,
QCOW2_CLUSTER_COMPRESSED,
QCOW2_CLUSTER_ZERO
};
#define L1E_OFFSET_MASK 0x00ffffffffffff00ULL
#define L2E_OFFSET_MASK 0x00ffffffffffff00ULL
#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL
#define REFT_OFFSET_MASK 0xffffffffffffff00ULL
static inline int size_to_clusters(BDRVQcowState *s, int64_t size)
{
return (size + (s->cluster_size - 1)) >> s->cluster_bits;
}
static inline int size_to_l1(BDRVQcowState *s, int64_t size)
{
int shift = s->cluster_bits + s->l2_bits;
return (size + (1ULL << shift) - 1) >> shift;
}
static inline int64_t align_offset(int64_t offset, int n)
{
offset = (offset + n - 1) & ~(n - 1);
return offset;
}
static inline int qcow2_get_cluster_type(uint64_t l2_entry)
{
if (l2_entry & QCOW_OFLAG_COMPRESSED) {
return QCOW2_CLUSTER_COMPRESSED;
} else if (l2_entry & QCOW_OFLAG_ZERO) {
return QCOW2_CLUSTER_ZERO;
} else if (!(l2_entry & L2E_OFFSET_MASK)) {
return QCOW2_CLUSTER_UNALLOCATED;
} else {
return QCOW2_CLUSTER_NORMAL;
}
}
/* Check whether refcounts are eager or lazy */
static inline bool qcow2_need_accurate_refcounts(BDRVQcowState *s)
{
return !(s->incompatible_features & QCOW2_INCOMPAT_DIRTY);
}
// FIXME Need qcow2_ prefix to global functions
/* qcow2.c functions */
int qcow2_backing_read1(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t sector_num, int nb_sectors);
int qcow2_update_header(BlockDriverState *bs);
/* qcow2-refcount.c functions */
int qcow2_refcount_init(BlockDriverState *bs);
void qcow2_refcount_close(BlockDriverState *bs);
int64_t qcow2_alloc_clusters(BlockDriverState *bs, int64_t size);
int qcow2_alloc_clusters_at(BlockDriverState *bs, uint64_t offset,
int nb_clusters);
int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size);
void qcow2_free_clusters(BlockDriverState *bs,
int64_t offset, int64_t size);
void qcow2_free_any_clusters(BlockDriverState *bs,
uint64_t cluster_offset, int nb_clusters);
int qcow2_update_snapshot_refcount(BlockDriverState *bs,
int64_t l1_table_offset, int l1_size, int addend);
int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
BdrvCheckMode fix);
/* qcow2-cluster.c functions */
int qcow2_grow_l1_table(BlockDriverState *bs, int min_size, bool exact_size);
void qcow2_l2_cache_reset(BlockDriverState *bs);
int qcow2_decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset);
void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
uint8_t *out_buf, const uint8_t *in_buf,
int nb_sectors, int enc,
const AES_KEY *key);
int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
int *num, uint64_t *cluster_offset);
int qcow2_alloc_cluster_offset(BlockDriverState *bs, uint64_t offset,
int n_start, int n_end, int *num, QCowL2Meta *m);
uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
uint64_t offset,
int compressed_size);
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
int nb_sectors);
int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
/* qcow2-snapshot.c functions */
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id);
int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab);
int qcow2_snapshot_load_tmp(BlockDriverState *bs, const char *snapshot_name);
void qcow2_free_snapshots(BlockDriverState *bs);
int qcow2_read_snapshots(BlockDriverState *bs);
/* qcow2-cache.c functions */
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);
void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table);
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c);
int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
Qcow2Cache *dependency);
void qcow2_cache_depends_on_flush(Qcow2Cache *c);
int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table);
int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
void **table);
int qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table);
#endif