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/*
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* QEMU Enhanced Disk Format
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*
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* Copyright IBM, Corp. 2010
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#ifndef BLOCK_QED_H
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#define BLOCK_QED_H
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#include "block_int.h" |
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/* The layout of a QED file is as follows:
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*
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* +--------+----------+----------+----------+-----+
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* | header | L1 table | cluster0 | cluster1 | ... |
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* +--------+----------+----------+----------+-----+
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*
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* There is a 2-level pagetable for cluster allocation:
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*
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* +----------+
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* | L1 table |
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* +----------+
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* ,------' | '------.
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* +----------+ | +----------+
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* | L2 table | ... | L2 table |
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* +----------+ +----------+
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* ,------' | '------.
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* +----------+ | +----------+
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* | Data | ... | Data |
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* +----------+ +----------+
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*
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* The L1 table is fixed size and always present. L2 tables are allocated on
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* demand. The L1 table size determines the maximum possible image size; it
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* can be influenced using the cluster_size and table_size values.
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*
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* All fields are little-endian on disk.
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*/
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enum {
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QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24, |
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/* The image supports a backing file */
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QED_F_BACKING_FILE = 0x01,
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/* The backing file format must not be probed, treat as raw image */
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QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
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/* Feature bits must be used when the on-disk format changes */
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QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
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QED_F_BACKING_FORMAT_NO_PROBE, |
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QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */ |
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QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear feature bits */ |
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/* Data is stored in groups of sectors called clusters. Cluster size must
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* be large to avoid keeping too much metadata. I/O requests that have
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* sub-cluster size will require read-modify-write.
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*/
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QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */ |
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QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024, |
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QED_DEFAULT_CLUSTER_SIZE = 64 * 1024, |
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/* Allocated clusters are tracked using a 2-level pagetable. Table size is
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* a multiple of clusters so large maximum image sizes can be supported
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* without jacking up the cluster size too much.
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*/
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QED_MIN_TABLE_SIZE = 1, /* in clusters */ |
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QED_MAX_TABLE_SIZE = 16,
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QED_DEFAULT_TABLE_SIZE = 4,
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}; |
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typedef struct { |
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uint32_t magic; /* QED\0 */
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uint32_t cluster_size; /* in bytes */
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uint32_t table_size; /* for L1 and L2 tables, in clusters */
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uint32_t header_size; /* in clusters */
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uint64_t features; /* format feature bits */
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uint64_t compat_features; /* compatible feature bits */
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uint64_t autoclear_features; /* self-resetting feature bits */
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uint64_t l1_table_offset; /* in bytes */
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uint64_t image_size; /* total logical image size, in bytes */
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/* if (features & QED_F_BACKING_FILE) */
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uint32_t backing_filename_offset; /* in bytes from start of header */
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uint32_t backing_filename_size; /* in bytes */
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} QEDHeader; |
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typedef struct { |
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BlockDriverState *bs; /* device */
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uint64_t file_size; /* length of image file, in bytes */
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QEDHeader header; /* always cpu-endian */
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uint32_t table_nelems; |
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uint32_t l1_shift; |
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uint32_t l2_shift; |
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uint32_t l2_mask; |
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} BDRVQEDState; |
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/**
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* Round down to the start of a cluster
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*/
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static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset) |
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{ |
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return offset & ~(uint64_t)(s->header.cluster_size - 1); |
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} |
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/**
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* Test if a cluster offset is valid
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*/
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static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset) |
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{ |
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uint64_t header_size = (uint64_t)s->header.header_size * |
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s->header.cluster_size; |
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if (offset & (s->header.cluster_size - 1)) { |
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return false; |
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} |
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return offset >= header_size && offset < s->file_size;
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} |
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/**
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* Test if a table offset is valid
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*/
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static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset) |
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{ |
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uint64_t end_offset = offset + (s->header.table_size - 1) *
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s->header.cluster_size; |
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/* Overflow check */
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if (end_offset <= offset) {
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return false; |
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} |
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return qed_check_cluster_offset(s, offset) &&
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qed_check_cluster_offset(s, end_offset); |
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} |
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#endif /* BLOCK_QED_H */ |