1 /* 2 * Image streaming 3 * 4 * Copyright IBM, Corp. 2011 5 * 6 * Authors: 7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> 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/block_int.h" 16 #include "block/blockjob.h" 17 #include "qemu/ratelimit.h" 18 19 enum { 20 /* 21 * Size of data buffer for populating the image file. This should be large 22 * enough to process multiple clusters in a single call, so that populating 23 * contiguous regions of the image is efficient. 24 */ 25 STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */ 26 }; 27 28 #define SLICE_TIME 100000000ULL /* ns */ 29 30 typedef struct StreamBlockJob { 31 BlockJob common; 32 RateLimit limit; 33 BlockDriverState *base; 34 BlockdevOnError on_error; 35 char *backing_file_str; 36 } StreamBlockJob; 37 38 static int coroutine_fn stream_populate(BlockDriverState *bs, 39 int64_t sector_num, int nb_sectors, 40 void *buf) 41 { 42 struct iovec iov = { 43 .iov_base = buf, 44 .iov_len = nb_sectors * BDRV_SECTOR_SIZE, 45 }; 46 QEMUIOVector qiov; 47 48 qemu_iovec_init_external(&qiov, &iov, 1); 49 50 /* Copy-on-read the unallocated clusters */ 51 return bdrv_co_copy_on_readv(bs, sector_num, nb_sectors, &qiov); 52 } 53 54 static void close_unused_images(BlockDriverState *top, BlockDriverState *base, 55 const char *base_id) 56 { 57 BlockDriverState *intermediate; 58 intermediate = top->backing_hd; 59 60 /* Must assign before bdrv_delete() to prevent traversing dangling pointer 61 * while we delete backing image instances. 62 */ 63 bdrv_set_backing_hd(top, base); 64 65 while (intermediate) { 66 BlockDriverState *unused; 67 68 /* reached base */ 69 if (intermediate == base) { 70 break; 71 } 72 73 unused = intermediate; 74 intermediate = intermediate->backing_hd; 75 bdrv_set_backing_hd(unused, NULL); 76 bdrv_unref(unused); 77 } 78 79 bdrv_refresh_limits(top, NULL); 80 } 81 82 typedef struct { 83 int ret; 84 bool reached_end; 85 } StreamCompleteData; 86 87 static void stream_complete(BlockJob *job, void *opaque) 88 { 89 StreamBlockJob *s = container_of(job, StreamBlockJob, common); 90 StreamCompleteData *data = opaque; 91 BlockDriverState *base = s->base; 92 93 if (!block_job_is_cancelled(&s->common) && data->reached_end && 94 data->ret == 0) { 95 const char *base_id = NULL, *base_fmt = NULL; 96 if (base) { 97 base_id = s->backing_file_str; 98 if (base->drv) { 99 base_fmt = base->drv->format_name; 100 } 101 } 102 data->ret = bdrv_change_backing_file(job->bs, base_id, base_fmt); 103 close_unused_images(job->bs, base, base_id); 104 } 105 106 g_free(s->backing_file_str); 107 block_job_completed(&s->common, data->ret); 108 g_free(data); 109 } 110 111 static void coroutine_fn stream_run(void *opaque) 112 { 113 StreamBlockJob *s = opaque; 114 StreamCompleteData *data; 115 BlockDriverState *bs = s->common.bs; 116 BlockDriverState *base = s->base; 117 int64_t sector_num, end; 118 int error = 0; 119 int ret = 0; 120 int n = 0; 121 void *buf; 122 123 if (!bs->backing_hd) { 124 block_job_completed(&s->common, 0); 125 return; 126 } 127 128 s->common.len = bdrv_getlength(bs); 129 if (s->common.len < 0) { 130 block_job_completed(&s->common, s->common.len); 131 return; 132 } 133 134 end = s->common.len >> BDRV_SECTOR_BITS; 135 buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE); 136 137 /* Turn on copy-on-read for the whole block device so that guest read 138 * requests help us make progress. Only do this when copying the entire 139 * backing chain since the copy-on-read operation does not take base into 140 * account. 141 */ 142 if (!base) { 143 bdrv_enable_copy_on_read(bs); 144 } 145 146 for (sector_num = 0; sector_num < end; sector_num += n) { 147 uint64_t delay_ns = 0; 148 bool copy; 149 150 wait: 151 /* Note that even when no rate limit is applied we need to yield 152 * with no pending I/O here so that bdrv_drain_all() returns. 153 */ 154 block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns); 155 if (block_job_is_cancelled(&s->common)) { 156 break; 157 } 158 159 copy = false; 160 161 ret = bdrv_is_allocated(bs, sector_num, 162 STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); 163 if (ret == 1) { 164 /* Allocated in the top, no need to copy. */ 165 } else if (ret >= 0) { 166 /* Copy if allocated in the intermediate images. Limit to the 167 * known-unallocated area [sector_num, sector_num+n). */ 168 ret = bdrv_is_allocated_above(bs->backing_hd, base, 169 sector_num, n, &n); 170 171 /* Finish early if end of backing file has been reached */ 172 if (ret == 0 && n == 0) { 173 n = end - sector_num; 174 } 175 176 copy = (ret == 1); 177 } 178 trace_stream_one_iteration(s, sector_num, n, ret); 179 if (copy) { 180 if (s->common.speed) { 181 delay_ns = ratelimit_calculate_delay(&s->limit, n); 182 if (delay_ns > 0) { 183 goto wait; 184 } 185 } 186 ret = stream_populate(bs, sector_num, n, buf); 187 } 188 if (ret < 0) { 189 BlockErrorAction action = 190 block_job_error_action(&s->common, s->common.bs, s->on_error, 191 true, -ret); 192 if (action == BLOCK_ERROR_ACTION_STOP) { 193 n = 0; 194 continue; 195 } 196 if (error == 0) { 197 error = ret; 198 } 199 if (action == BLOCK_ERROR_ACTION_REPORT) { 200 break; 201 } 202 } 203 ret = 0; 204 205 /* Publish progress */ 206 s->common.offset += n * BDRV_SECTOR_SIZE; 207 } 208 209 if (!base) { 210 bdrv_disable_copy_on_read(bs); 211 } 212 213 /* Do not remove the backing file if an error was there but ignored. */ 214 ret = error; 215 216 qemu_vfree(buf); 217 218 /* Modify backing chain and close BDSes in main loop */ 219 data = g_malloc(sizeof(*data)); 220 data->ret = ret; 221 data->reached_end = sector_num == end; 222 block_job_defer_to_main_loop(&s->common, stream_complete, data); 223 } 224 225 static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp) 226 { 227 StreamBlockJob *s = container_of(job, StreamBlockJob, common); 228 229 if (speed < 0) { 230 error_set(errp, QERR_INVALID_PARAMETER, "speed"); 231 return; 232 } 233 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 234 } 235 236 static const BlockJobDriver stream_job_driver = { 237 .instance_size = sizeof(StreamBlockJob), 238 .job_type = BLOCK_JOB_TYPE_STREAM, 239 .set_speed = stream_set_speed, 240 }; 241 242 void stream_start(BlockDriverState *bs, BlockDriverState *base, 243 const char *backing_file_str, int64_t speed, 244 BlockdevOnError on_error, 245 BlockCompletionFunc *cb, 246 void *opaque, Error **errp) 247 { 248 StreamBlockJob *s; 249 250 if ((on_error == BLOCKDEV_ON_ERROR_STOP || 251 on_error == BLOCKDEV_ON_ERROR_ENOSPC) && 252 !bdrv_iostatus_is_enabled(bs)) { 253 error_set(errp, QERR_INVALID_PARAMETER, "on-error"); 254 return; 255 } 256 257 s = block_job_create(&stream_job_driver, bs, speed, cb, opaque, errp); 258 if (!s) { 259 return; 260 } 261 262 s->base = base; 263 s->backing_file_str = g_strdup(backing_file_str); 264 265 s->on_error = on_error; 266 s->common.co = qemu_coroutine_create(stream_run); 267 trace_stream_start(bs, base, s, s->common.co, opaque); 268 qemu_coroutine_enter(s->common.co, s); 269 } 270