/* * 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); /** * 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 */