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Diffstat (limited to 'block/qed.h')
| -rw-r--r-- | block/qed.h | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/block/qed.h b/block/qed.h new file mode 100644 index 0000000000..1f8a125787 --- /dev/null +++ b/block/qed.h @@ -0,0 +1,148 @@ +/* + * 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 */ |