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* QEMU Enhanced Disk Format
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* Copyright IBM, Corp. 2010
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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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* 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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#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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* | header | L1 table | cluster0 | cluster1 | ... |
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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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* | L2 table | ... | L2 table |
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* +----------+ +----------+
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* +----------+ | +----------+
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* | Data | ... | Data |
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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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* All fields are little-endian on disk.
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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 image needs a consistency check before use */
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QED_F_NEED_CHECK = 0x02,
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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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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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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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/* Delay to flush and clean image after last allocating write completes */
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QED_NEED_CHECK_TIMEOUT = 5, /* in seconds */
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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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uint64_t offsets[0]; /* in bytes */
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/* The L2 cache is a simple write-through cache for L2 structures */
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typedef struct CachedL2Table {
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uint64_t offset; /* offset=0 indicates an invalidate entry */
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QTAILQ_ENTRY(CachedL2Table) node;
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QTAILQ_HEAD(, CachedL2Table) entries;
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unsigned int n_entries;
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typedef struct QEDRequest {
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CachedL2Table *l2_table;
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typedef struct QEDAIOCB {
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BlockDriverAIOCB common;
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int bh_ret; /* final return status for completion bh */
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QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */
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bool is_write; /* false - read, true - write */
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bool *finished; /* signal for cancel completion */
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uint64_t end_pos; /* request end on block device, in bytes */
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/* User scatter-gather list */
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size_t qiov_offset; /* byte count already processed */
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/* Current cluster scatter-gather list */
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QEMUIOVector cur_qiov;
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uint64_t cur_pos; /* position on block device, in bytes */
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uint64_t cur_cluster; /* cluster offset in image file */
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unsigned int cur_nclusters; /* number of clusters being accessed */
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int find_cluster_ret; /* used for L1/L2 update */
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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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L2TableCache l2_cache; /* l2 table cache */
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uint32_t table_nelems;
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/* Allocating write request queue */
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QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
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bool allocating_write_reqs_plugged;
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/* Periodic flush and clear need check flag */
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QEMUTimer *need_check_timer;
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QED_CLUSTER_FOUND, /* cluster found */
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QED_CLUSTER_ZERO, /* zero cluster found */
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QED_CLUSTER_L2, /* cluster missing in L2 */
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QED_CLUSTER_L1, /* cluster missing in L1 */
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* qed_find_cluster() completion callback
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* @opaque: User data for completion callback
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* @ret: QED_CLUSTER_FOUND Success
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* QED_CLUSTER_L2 Data cluster unallocated in L2
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* QED_CLUSTER_L1 L2 unallocated in L1
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* -errno POSIX error occurred
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* @offset: Data cluster offset
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* @len: Contiguous bytes starting from cluster offset
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* This function is invoked when qed_find_cluster() completes.
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* On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
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* On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
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* table offset, respectively. len is number of contiguous unallocated bytes.
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typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
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* Generic callback for chaining async callbacks
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BlockDriverCompletionFunc *cb;
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void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);
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void gencb_complete(void *opaque, int ret);
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void qed_init_l2_cache(L2TableCache *l2_cache);
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void qed_free_l2_cache(L2TableCache *l2_cache);
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CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
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void qed_unref_l2_cache_entry(CachedL2Table *entry);
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CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
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void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
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* Table I/O functions
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int qed_read_l1_table_sync(BDRVQEDState *s);
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void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
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BlockDriverCompletionFunc *cb, void *opaque);
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int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
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int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
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void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
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BlockDriverCompletionFunc *cb, void *opaque);
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void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
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unsigned int index, unsigned int n, bool flush,
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BlockDriverCompletionFunc *cb, void *opaque);
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int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
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unsigned int index, unsigned int n, bool flush);
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void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
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size_t len, QEDFindClusterFunc *cb, void *opaque);
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int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
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QEDTable *qed_alloc_table(BDRVQEDState *s);
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* Round down to the start of a cluster
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static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
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return offset & ~(uint64_t)(s->header.cluster_size - 1);
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static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
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return offset & (s->header.cluster_size - 1);
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static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
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return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
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(s->header.cluster_size - 1);
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static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
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return pos >> s->l1_shift;
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static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
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return (pos >> s->l2_shift) & s->l2_mask;
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* Test if a cluster offset is valid
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static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
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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 offset >= header_size && offset < s->file_size;
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* Test if a table offset is valid
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static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
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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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if (end_offset <= offset) {
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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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static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
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if (qed_offset_into_cluster(s, offset)) {
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static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
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static inline bool qed_offset_is_zero_cluster(uint64_t offset)
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#endif /* BLOCK_QED_H */
added
removed
block/qed.h
