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1.1 root 1: /*
2: * Image streaming
3: *
4: * Copyright IBM, Corp. 2011
5: *
6: * Authors:
7: * Stefan Hajnoczi <[email protected]>
8: *
9: * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10: * See the COPYING.LIB file in the top-level directory.
11: *
12: */
13:
14: #include "trace.h"
15: #include "block_int.h"
16:
17: enum {
18: /*
19: * Size of data buffer for populating the image file. This should be large
20: * enough to process multiple clusters in a single call, so that populating
21: * contiguous regions of the image is efficient.
22: */
23: STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */
24: };
25:
26: #define SLICE_TIME 100000000ULL /* ns */
27:
28: typedef struct {
29: int64_t next_slice_time;
30: uint64_t slice_quota;
31: uint64_t dispatched;
32: } RateLimit;
33:
34: static int64_t ratelimit_calculate_delay(RateLimit *limit, uint64_t n)
35: {
36: int64_t now = qemu_get_clock_ns(rt_clock);
37:
38: if (limit->next_slice_time < now) {
39: limit->next_slice_time = now + SLICE_TIME;
40: limit->dispatched = 0;
41: }
42: if (limit->dispatched == 0 || limit->dispatched + n <= limit->slice_quota) {
43: limit->dispatched += n;
44: return 0;
45: } else {
46: limit->dispatched = n;
47: return limit->next_slice_time - now;
48: }
49: }
50:
51: static void ratelimit_set_speed(RateLimit *limit, uint64_t speed)
52: {
53: limit->slice_quota = speed / (1000000000ULL / SLICE_TIME);
54: }
55:
56: typedef struct StreamBlockJob {
57: BlockJob common;
58: RateLimit limit;
59: BlockDriverState *base;
60: char backing_file_id[1024];
61: } StreamBlockJob;
62:
63: static int coroutine_fn stream_populate(BlockDriverState *bs,
64: int64_t sector_num, int nb_sectors,
65: void *buf)
66: {
67: struct iovec iov = {
68: .iov_base = buf,
69: .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
70: };
71: QEMUIOVector qiov;
72:
73: qemu_iovec_init_external(&qiov, &iov, 1);
74:
75: /* Copy-on-read the unallocated clusters */
76: return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov);
77: }
78:
79: static void close_unused_images(BlockDriverState *top, BlockDriverState *base,
80: const char *base_id)
81: {
82: BlockDriverState *intermediate;
83: intermediate = top->backing_hd;
84:
85: while (intermediate) {
86: BlockDriverState *unused;
87:
88: /* reached base */
89: if (intermediate == base) {
90: break;
91: }
92:
93: unused = intermediate;
94: intermediate = intermediate->backing_hd;
95: unused->backing_hd = NULL;
96: bdrv_delete(unused);
97: }
98: top->backing_hd = base;
99: }
100:
101: /*
102: * Given an image chain: [BASE] -> [INTER1] -> [INTER2] -> [TOP]
103: *
104: * Return true if the given sector is allocated in top.
105: * Return false if the given sector is allocated in intermediate images.
106: * Return true otherwise.
107: *
108: * 'pnum' is set to the number of sectors (including and immediately following
109: * the specified sector) that are known to be in the same
110: * allocated/unallocated state.
111: *
112: */
113: static int coroutine_fn is_allocated_base(BlockDriverState *top,
114: BlockDriverState *base,
115: int64_t sector_num,
116: int nb_sectors, int *pnum)
117: {
118: BlockDriverState *intermediate;
119: int ret, n;
120:
121: ret = bdrv_co_is_allocated(top, sector_num, nb_sectors, &n);
122: if (ret) {
123: *pnum = n;
124: return ret;
125: }
126:
127: /*
128: * Is the unallocated chunk [sector_num, n] also
129: * unallocated between base and top?
130: */
131: intermediate = top->backing_hd;
132:
133: while (intermediate != base) {
134: int pnum_inter;
135:
136: ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors,
137: &pnum_inter);
138: if (ret < 0) {
139: return ret;
140: } else if (ret) {
141: *pnum = pnum_inter;
142: return 0;
143: }
144:
145: /*
146: * [sector_num, nb_sectors] is unallocated on top but intermediate
147: * might have
148: *
149: * [sector_num+x, nr_sectors] allocated.
150: */
151: if (n > pnum_inter) {
152: n = pnum_inter;
153: }
154:
155: intermediate = intermediate->backing_hd;
156: }
157:
158: *pnum = n;
159: return 1;
160: }
161:
162: static void coroutine_fn stream_run(void *opaque)
163: {
164: StreamBlockJob *s = opaque;
165: BlockDriverState *bs = s->common.bs;
166: BlockDriverState *base = s->base;
167: int64_t sector_num, end;
168: int ret = 0;
169: int n = 0;
170: void *buf;
171:
172: s->common.len = bdrv_getlength(bs);
173: if (s->common.len < 0) {
174: block_job_complete(&s->common, s->common.len);
175: return;
176: }
177:
178: end = s->common.len >> BDRV_SECTOR_BITS;
179: buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE);
180:
181: /* Turn on copy-on-read for the whole block device so that guest read
182: * requests help us make progress. Only do this when copying the entire
183: * backing chain since the copy-on-read operation does not take base into
184: * account.
185: */
186: if (!base) {
187: bdrv_enable_copy_on_read(bs);
188: }
189:
190: for (sector_num = 0; sector_num < end; sector_num += n) {
191: uint64_t delay_ns = 0;
192:
193: wait:
194: /* Note that even when no rate limit is applied we need to yield
195: * with no pending I/O here so that qemu_aio_flush() returns.
196: */
197: block_job_sleep_ns(&s->common, rt_clock, delay_ns);
198: if (block_job_is_cancelled(&s->common)) {
199: break;
200: }
201:
202: ret = is_allocated_base(bs, base, sector_num,
203: STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
204: trace_stream_one_iteration(s, sector_num, n, ret);
205: if (ret == 0) {
206: if (s->common.speed) {
207: delay_ns = ratelimit_calculate_delay(&s->limit, n);
208: if (delay_ns > 0) {
209: goto wait;
210: }
211: }
212: ret = stream_populate(bs, sector_num, n, buf);
213: }
214: if (ret < 0) {
215: break;
216: }
217: ret = 0;
218:
219: /* Publish progress */
220: s->common.offset += n * BDRV_SECTOR_SIZE;
221: }
222:
223: if (!base) {
224: bdrv_disable_copy_on_read(bs);
225: }
226:
227: if (!block_job_is_cancelled(&s->common) && sector_num == end && ret == 0) {
228: const char *base_id = NULL, *base_fmt = NULL;
229: if (base) {
230: base_id = s->backing_file_id;
231: if (base->drv) {
232: base_fmt = base->drv->format_name;
233: }
234: }
235: ret = bdrv_change_backing_file(bs, base_id, base_fmt);
236: close_unused_images(bs, base, base_id);
237: }
238:
239: qemu_vfree(buf);
240: block_job_complete(&s->common, ret);
241: }
242:
243: static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
244: {
245: StreamBlockJob *s = container_of(job, StreamBlockJob, common);
246:
247: if (speed < 0) {
248: error_set(errp, QERR_INVALID_PARAMETER, "speed");
249: return;
250: }
251: ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE);
252: }
253:
254: static BlockJobType stream_job_type = {
255: .instance_size = sizeof(StreamBlockJob),
256: .job_type = "stream",
257: .set_speed = stream_set_speed,
258: };
259:
260: void stream_start(BlockDriverState *bs, BlockDriverState *base,
261: const char *base_id, int64_t speed,
262: BlockDriverCompletionFunc *cb,
263: void *opaque, Error **errp)
264: {
265: StreamBlockJob *s;
266:
267: s = block_job_create(&stream_job_type, bs, speed, cb, opaque, errp);
268: if (!s) {
269: return;
270: }
271:
272: s->base = base;
273: if (base_id) {
274: pstrcpy(s->backing_file_id, sizeof(s->backing_file_id), base_id);
275: }
276:
277: s->common.co = qemu_coroutine_create(stream_run);
278: trace_stream_start(bs, base, s, s->common.co, opaque);
279: qemu_coroutine_enter(s->common.co, s);
280: }
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