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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_int.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.
*/
enum {
QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
/* The image supports a backing file */
QED_F_BACKING_FILE = 0x01,
/* 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_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,
QED_DEFAULT_CLUSTER_SIZE = 64 * 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,
};
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 */
} QEDHeader;
typedef struct {
BlockDriverState *bs; /* device */
uint64_t file_size; /* length of image file, in bytes */
QEDHeader header; /* always cpu-endian */
uint32_t table_nelems;
uint32_t l1_shift;
uint32_t l2_shift;
uint32_t l2_mask;
} BDRVQEDState;
/**
* 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);
}
/**
* 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);
}
#endif /* BLOCK_QED_H */
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