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1.1 root 1: /*
2: * QEMU Enhanced Disk Format
3: *
4: * Copyright IBM, Corp. 2010
5: *
6: * Authors:
7: * Stefan Hajnoczi <[email protected]>
8: * Anthony Liguori <[email protected]>
9: *
10: * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11: * See the COPYING.LIB file in the top-level directory.
12: *
13: */
14:
15: #ifndef BLOCK_QED_H
16: #define BLOCK_QED_H
17:
18: #include "block_int.h"
19:
20: /* The layout of a QED file is as follows:
21: *
22: * +--------+----------+----------+----------+-----+
23: * | header | L1 table | cluster0 | cluster1 | ... |
24: * +--------+----------+----------+----------+-----+
25: *
26: * There is a 2-level pagetable for cluster allocation:
27: *
28: * +----------+
29: * | L1 table |
30: * +----------+
31: * ,------' | '------.
32: * +----------+ | +----------+
33: * | L2 table | ... | L2 table |
34: * +----------+ +----------+
35: * ,------' | '------.
36: * +----------+ | +----------+
37: * | Data | ... | Data |
38: * +----------+ +----------+
39: *
40: * The L1 table is fixed size and always present. L2 tables are allocated on
41: * demand. The L1 table size determines the maximum possible image size; it
42: * can be influenced using the cluster_size and table_size values.
43: *
44: * All fields are little-endian on disk.
45: */
46:
47: enum {
48: QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
49:
50: /* The image supports a backing file */
51: QED_F_BACKING_FILE = 0x01,
52:
53: /* The image needs a consistency check before use */
54: QED_F_NEED_CHECK = 0x02,
55:
56: /* The backing file format must not be probed, treat as raw image */
57: QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
58:
59: /* Feature bits must be used when the on-disk format changes */
60: QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
61: QED_F_NEED_CHECK |
62: QED_F_BACKING_FORMAT_NO_PROBE,
63: QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */
64: QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear feature bits */
65:
66: /* Data is stored in groups of sectors called clusters. Cluster size must
67: * be large to avoid keeping too much metadata. I/O requests that have
68: * sub-cluster size will require read-modify-write.
69: */
70: QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
71: QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,
72: QED_DEFAULT_CLUSTER_SIZE = 64 * 1024,
73:
74: /* Allocated clusters are tracked using a 2-level pagetable. Table size is
75: * a multiple of clusters so large maximum image sizes can be supported
76: * without jacking up the cluster size too much.
77: */
78: QED_MIN_TABLE_SIZE = 1, /* in clusters */
79: QED_MAX_TABLE_SIZE = 16,
80: QED_DEFAULT_TABLE_SIZE = 4,
81: };
82:
83: typedef struct {
84: uint32_t magic; /* QED\0 */
85:
86: uint32_t cluster_size; /* in bytes */
87: uint32_t table_size; /* for L1 and L2 tables, in clusters */
88: uint32_t header_size; /* in clusters */
89:
90: uint64_t features; /* format feature bits */
91: uint64_t compat_features; /* compatible feature bits */
92: uint64_t autoclear_features; /* self-resetting feature bits */
93:
94: uint64_t l1_table_offset; /* in bytes */
95: uint64_t image_size; /* total logical image size, in bytes */
96:
97: /* if (features & QED_F_BACKING_FILE) */
98: uint32_t backing_filename_offset; /* in bytes from start of header */
99: uint32_t backing_filename_size; /* in bytes */
100: } QEDHeader;
101:
102: typedef struct {
103: uint64_t offsets[0]; /* in bytes */
104: } QEDTable;
105:
106: /* The L2 cache is a simple write-through cache for L2 structures */
107: typedef struct CachedL2Table {
108: QEDTable *table;
109: uint64_t offset; /* offset=0 indicates an invalidate entry */
110: QTAILQ_ENTRY(CachedL2Table) node;
111: int ref;
112: } CachedL2Table;
113:
114: typedef struct {
115: QTAILQ_HEAD(, CachedL2Table) entries;
116: unsigned int n_entries;
117: } L2TableCache;
118:
119: typedef struct QEDRequest {
120: CachedL2Table *l2_table;
121: } QEDRequest;
122:
123: typedef struct QEDAIOCB {
124: BlockDriverAIOCB common;
125: QEMUBH *bh;
126: int bh_ret; /* final return status for completion bh */
127: QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */
128: bool is_write; /* false - read, true - write */
129: bool *finished; /* signal for cancel completion */
130: uint64_t end_pos; /* request end on block device, in bytes */
131:
132: /* User scatter-gather list */
133: QEMUIOVector *qiov;
134: size_t qiov_offset; /* byte count already processed */
135:
136: /* Current cluster scatter-gather list */
137: QEMUIOVector cur_qiov;
138: uint64_t cur_pos; /* position on block device, in bytes */
139: uint64_t cur_cluster; /* cluster offset in image file */
140: unsigned int cur_nclusters; /* number of clusters being accessed */
141: int find_cluster_ret; /* used for L1/L2 update */
142:
143: QEDRequest request;
144: } QEDAIOCB;
145:
146: typedef struct {
147: BlockDriverState *bs; /* device */
148: uint64_t file_size; /* length of image file, in bytes */
149:
150: QEDHeader header; /* always cpu-endian */
151: QEDTable *l1_table;
152: L2TableCache l2_cache; /* l2 table cache */
153: uint32_t table_nelems;
154: uint32_t l1_shift;
155: uint32_t l2_shift;
156: uint32_t l2_mask;
157:
158: /* Allocating write request queue */
159: QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
160: } BDRVQEDState;
161:
162: enum {
163: QED_CLUSTER_FOUND, /* cluster found */
164: QED_CLUSTER_L2, /* cluster missing in L2 */
165: QED_CLUSTER_L1, /* cluster missing in L1 */
166: };
167:
168: /**
169: * qed_find_cluster() completion callback
170: *
171: * @opaque: User data for completion callback
172: * @ret: QED_CLUSTER_FOUND Success
173: * QED_CLUSTER_L2 Data cluster unallocated in L2
174: * QED_CLUSTER_L1 L2 unallocated in L1
175: * -errno POSIX error occurred
176: * @offset: Data cluster offset
177: * @len: Contiguous bytes starting from cluster offset
178: *
179: * This function is invoked when qed_find_cluster() completes.
180: *
181: * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
182: * in the image file.
183: *
184: * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
185: * table offset, respectively. len is number of contiguous unallocated bytes.
186: */
187: typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
188:
189: /**
190: * Generic callback for chaining async callbacks
191: */
192: typedef struct {
193: BlockDriverCompletionFunc *cb;
194: void *opaque;
195: } GenericCB;
196:
197: void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);
198: void gencb_complete(void *opaque, int ret);
199:
200: /**
201: * L2 cache functions
202: */
203: void qed_init_l2_cache(L2TableCache *l2_cache);
204: void qed_free_l2_cache(L2TableCache *l2_cache);
205: CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
206: void qed_unref_l2_cache_entry(CachedL2Table *entry);
207: CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
208: void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
209:
210: /**
211: * Table I/O functions
212: */
213: int qed_read_l1_table_sync(BDRVQEDState *s);
214: void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
215: BlockDriverCompletionFunc *cb, void *opaque);
216: int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
217: unsigned int n);
218: int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
219: uint64_t offset);
220: void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
221: BlockDriverCompletionFunc *cb, void *opaque);
222: void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
223: unsigned int index, unsigned int n, bool flush,
224: BlockDriverCompletionFunc *cb, void *opaque);
225: int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
226: unsigned int index, unsigned int n, bool flush);
227:
228: /**
229: * Cluster functions
230: */
231: void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
232: size_t len, QEDFindClusterFunc *cb, void *opaque);
233:
234: /**
235: * Consistency check
236: */
237: int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
238:
239: QEDTable *qed_alloc_table(BDRVQEDState *s);
240:
241: /**
242: * Round down to the start of a cluster
243: */
244: static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
245: {
246: return offset & ~(uint64_t)(s->header.cluster_size - 1);
247: }
248:
249: static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
250: {
251: return offset & (s->header.cluster_size - 1);
252: }
253:
1.1.1.2 ! root 254: static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
1.1 root 255: {
256: return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
257: (s->header.cluster_size - 1);
258: }
259:
260: static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
261: {
262: return pos >> s->l1_shift;
263: }
264:
265: static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
266: {
267: return (pos >> s->l2_shift) & s->l2_mask;
268: }
269:
270: /**
271: * Test if a cluster offset is valid
272: */
273: static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
274: {
275: uint64_t header_size = (uint64_t)s->header.header_size *
276: s->header.cluster_size;
277:
278: if (offset & (s->header.cluster_size - 1)) {
279: return false;
280: }
281: return offset >= header_size && offset < s->file_size;
282: }
283:
284: /**
285: * Test if a table offset is valid
286: */
287: static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
288: {
289: uint64_t end_offset = offset + (s->header.table_size - 1) *
290: s->header.cluster_size;
291:
292: /* Overflow check */
293: if (end_offset <= offset) {
294: return false;
295: }
296:
297: return qed_check_cluster_offset(s, offset) &&
298: qed_check_cluster_offset(s, end_offset);
299: }
300:
301: #endif /* BLOCK_QED_H */
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