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qemu/block/qed.h

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/*
* QEMU Enhanced Disk Format
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#ifndef BLOCK_QED_H
#define BLOCK_QED_H
#include "block/block_int.h"
#include "qemu/cutils.h"
/* The layout of a QED file is as follows:
*
* +--------+----------+----------+----------+-----+
* | header | L1 table | cluster0 | cluster1 | ... |
* +--------+----------+----------+----------+-----+
*
* There is a 2-level pagetable for cluster allocation:
*
* +----------+
* | L1 table |
* +----------+
* ,------' | '------.
* +----------+ | +----------+
* | L2 table | ... | L2 table |
* +----------+ +----------+
* ,------' | '------.
* +----------+ | +----------+
* | Data | ... | Data |
* +----------+ +----------+
*
* The L1 table is fixed size and always present. L2 tables are allocated on
* demand. The L1 table size determines the maximum possible image size; it
* can be influenced using the cluster_size and table_size values.
*
* All fields are little-endian on disk.
*/
#define QED_DEFAULT_CLUSTER_SIZE 65536
enum {
QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
/* The image supports a backing file */
QED_F_BACKING_FILE = 0x01,
/* The image needs a consistency check before use */
QED_F_NEED_CHECK = 0x02,
/* The backing file format must not be probed, treat as raw image */
QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
/* Feature bits must be used when the on-disk format changes */
QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
QED_F_NEED_CHECK |
QED_F_BACKING_FORMAT_NO_PROBE,
QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */
QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear feature bits */
/* Data is stored in groups of sectors called clusters. Cluster size must
* be large to avoid keeping too much metadata. I/O requests that have
* sub-cluster size will require read-modify-write.
*/
QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,
/* Allocated clusters are tracked using a 2-level pagetable. Table size is
* a multiple of clusters so large maximum image sizes can be supported
* without jacking up the cluster size too much.
*/
QED_MIN_TABLE_SIZE = 1, /* in clusters */
QED_MAX_TABLE_SIZE = 16,
QED_DEFAULT_TABLE_SIZE = 4,
/* Delay to flush and clean image after last allocating write completes */
QED_NEED_CHECK_TIMEOUT = 5, /* in seconds */
};
typedef struct {
uint32_t magic; /* QED\0 */
uint32_t cluster_size; /* in bytes */
uint32_t table_size; /* for L1 and L2 tables, in clusters */
uint32_t header_size; /* in clusters */
uint64_t features; /* format feature bits */
uint64_t compat_features; /* compatible feature bits */
uint64_t autoclear_features; /* self-resetting feature bits */
uint64_t l1_table_offset; /* in bytes */
uint64_t image_size; /* total logical image size, in bytes */
/* if (features & QED_F_BACKING_FILE) */
uint32_t backing_filename_offset; /* in bytes from start of header */
uint32_t backing_filename_size; /* in bytes */
} QEMU_PACKED QEDHeader;
typedef struct {
uint64_t offsets[0]; /* in bytes */
} QEDTable;
/* The L2 cache is a simple write-through cache for L2 structures */
typedef struct CachedL2Table {
QEDTable *table;
uint64_t offset; /* offset=0 indicates an invalidate entry */
QTAILQ_ENTRY(CachedL2Table) node;
int ref;
} CachedL2Table;
typedef struct {
QTAILQ_HEAD(, CachedL2Table) entries;
unsigned int n_entries;
} L2TableCache;
typedef struct QEDRequest {
CachedL2Table *l2_table;
} QEDRequest;
enum {
QED_AIOCB_WRITE = 0x0001, /* read or write? */
QED_AIOCB_ZERO = 0x0002, /* zero write, used with QED_AIOCB_WRITE */
};
typedef struct QEDAIOCB {
BlockAIOCB common;
int bh_ret; /* final return status for completion bh */
QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */
int flags; /* QED_AIOCB_* bits ORed together */
uint64_t end_pos; /* request end on block device, in bytes */
/* User scatter-gather list */
QEMUIOVector *qiov;
size_t qiov_offset; /* byte count already processed */
/* Current cluster scatter-gather list */
QEMUIOVector cur_qiov;
QEMUIOVector *backing_qiov;
uint64_t cur_pos; /* position on block device, in bytes */
uint64_t cur_cluster; /* cluster offset in image file */
unsigned int cur_nclusters; /* number of clusters being accessed */
int find_cluster_ret; /* used for L1/L2 update */
QEDRequest request;
} QEDAIOCB;
typedef struct {
BlockDriverState *bs; /* device */
uint64_t file_size; /* length of image file, in bytes */
QEDHeader header; /* always cpu-endian */
QEDTable *l1_table;
L2TableCache l2_cache; /* l2 table cache */
uint32_t table_nelems;
uint32_t l1_shift;
uint32_t l2_shift;
uint32_t l2_mask;
/* Allocating write request queue */
QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
bool allocating_write_reqs_plugged;
/* Periodic flush and clear need check flag */
QEMUTimer *need_check_timer;
} BDRVQEDState;
enum {
QED_CLUSTER_FOUND, /* cluster found */
QED_CLUSTER_ZERO, /* zero cluster found */
QED_CLUSTER_L2, /* cluster missing in L2 */
QED_CLUSTER_L1, /* cluster missing in L1 */
};
/**
* qed_find_cluster() completion callback
*
* @opaque: User data for completion callback
* @ret: QED_CLUSTER_FOUND Success
* QED_CLUSTER_L2 Data cluster unallocated in L2
* QED_CLUSTER_L1 L2 unallocated in L1
* -errno POSIX error occurred
* @offset: Data cluster offset
* @len: Contiguous bytes starting from cluster offset
*
* This function is invoked when qed_find_cluster() completes.
*
* On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
* in the image file.
*
* On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
* table offset, respectively. len is number of contiguous unallocated bytes.
*/
typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
void qed_acquire(BDRVQEDState *s);
void qed_release(BDRVQEDState *s);
/**
* Generic callback for chaining async callbacks
*/
typedef struct {
BlockCompletionFunc *cb;
void *opaque;
} GenericCB;
void *gencb_alloc(size_t len, BlockCompletionFunc *cb, void *opaque);
void gencb_complete(void *opaque, int ret);
/**
* Header functions
*/
int qed_write_header_sync(BDRVQEDState *s);
/**
* L2 cache functions
*/
void qed_init_l2_cache(L2TableCache *l2_cache);
void qed_free_l2_cache(L2TableCache *l2_cache);
CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
void qed_unref_l2_cache_entry(CachedL2Table *entry);
CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
/**
* Table I/O functions
*/
int qed_read_l1_table_sync(BDRVQEDState *s);
void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
BlockCompletionFunc *cb, void *opaque);
int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
unsigned int n);
int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
uint64_t offset);
void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
BlockCompletionFunc *cb, void *opaque);
void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
unsigned int index, unsigned int n, bool flush,
BlockCompletionFunc *cb, void *opaque);
int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
unsigned int index, unsigned int n, bool flush);
/**
* Cluster functions
*/
void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
size_t len, QEDFindClusterFunc *cb, void *opaque);
/**
* Consistency check
*/
int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
QEDTable *qed_alloc_table(BDRVQEDState *s);
/**
* Round down to the start of a cluster
*/
static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
{
return offset & ~(uint64_t)(s->header.cluster_size - 1);
}
static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
{
return offset & (s->header.cluster_size - 1);
}
static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
{
return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
(s->header.cluster_size - 1);
}
static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
{
return pos >> s->l1_shift;
}
static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
{
return (pos >> s->l2_shift) & s->l2_mask;
}
/**
* Test if a cluster offset is valid
*/
static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
{
uint64_t header_size = (uint64_t)s->header.header_size *
s->header.cluster_size;
if (offset & (s->header.cluster_size - 1)) {
return false;
}
return offset >= header_size && offset < s->file_size;
}
/**
* Test if a table offset is valid
*/
static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
{
uint64_t end_offset = offset + (s->header.table_size - 1) *
s->header.cluster_size;
/* Overflow check */
if (end_offset <= offset) {
return false;
}
return qed_check_cluster_offset(s, offset) &&
qed_check_cluster_offset(s, end_offset);
}
static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
uint64_t offset)
{
if (qed_offset_into_cluster(s, offset)) {
return false;
}
return true;
}
static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
{
if (offset == 0) {
return true;
}
return false;
}
static inline bool qed_offset_is_zero_cluster(uint64_t offset)
{
if (offset == 1) {
return true;
}
return false;
}
#endif /* BLOCK_QED_H */
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