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 "qemu/osdep.h" 15 #include "trace.h" 16 #include "block/block_int.h" 17 #include "block/blockjob_int.h" 18 #include "qapi/error.h" 19 #include "qapi/qmp/qerror.h" 20 #include "qemu/ratelimit.h" 21 #include "sysemu/block-backend.h" 22 23 enum { 24 /* 25 * Size of data buffer for populating the image file. This should be large 26 * enough to process multiple clusters in a single call, so that populating 27 * contiguous regions of the image is efficient. 28 */ 29 STREAM_BUFFER_SIZE = 512 * 1024, /* in bytes */ 30 }; 31 32 #define SLICE_TIME 100000000ULL /* ns */ 33 34 typedef struct StreamBlockJob { 35 BlockJob common; 36 RateLimit limit; 37 BlockDriverState *base; 38 BlockdevOnError on_error; 39 char *backing_file_str; 40 int bs_flags; 41 } StreamBlockJob; 42 43 static int coroutine_fn stream_populate(BlockBackend *blk, 44 int64_t sector_num, int nb_sectors, 45 void *buf) 46 { 47 struct iovec iov = { 48 .iov_base = buf, 49 .iov_len = nb_sectors * BDRV_SECTOR_SIZE, 50 }; 51 QEMUIOVector qiov; 52 53 qemu_iovec_init_external(&qiov, &iov, 1); 54 55 /* Copy-on-read the unallocated clusters */ 56 return blk_co_preadv(blk, sector_num * BDRV_SECTOR_SIZE, qiov.size, &qiov, 57 BDRV_REQ_COPY_ON_READ); 58 } 59 60 typedef struct { 61 int ret; 62 bool reached_end; 63 } StreamCompleteData; 64 65 static void stream_complete(BlockJob *job, void *opaque) 66 { 67 StreamBlockJob *s = container_of(job, StreamBlockJob, common); 68 StreamCompleteData *data = opaque; 69 BlockDriverState *bs = blk_bs(job->blk); 70 BlockDriverState *base = s->base; 71 Error *local_err = NULL; 72 73 if (!block_job_is_cancelled(&s->common) && data->reached_end && 74 data->ret == 0) { 75 const char *base_id = NULL, *base_fmt = NULL; 76 if (base) { 77 base_id = s->backing_file_str; 78 if (base->drv) { 79 base_fmt = base->drv->format_name; 80 } 81 } 82 data->ret = bdrv_change_backing_file(bs, base_id, base_fmt); 83 bdrv_set_backing_hd(bs, base, &local_err); 84 if (local_err) { 85 error_report_err(local_err); 86 data->ret = -EPERM; 87 goto out; 88 } 89 } 90 91 out: 92 /* Reopen the image back in read-only mode if necessary */ 93 if (s->bs_flags != bdrv_get_flags(bs)) { 94 /* Give up write permissions before making it read-only */ 95 blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort); 96 bdrv_reopen(bs, s->bs_flags, NULL); 97 } 98 99 g_free(s->backing_file_str); 100 block_job_completed(&s->common, data->ret); 101 g_free(data); 102 } 103 104 static void coroutine_fn stream_run(void *opaque) 105 { 106 StreamBlockJob *s = opaque; 107 StreamCompleteData *data; 108 BlockBackend *blk = s->common.blk; 109 BlockDriverState *bs = blk_bs(blk); 110 BlockDriverState *base = s->base; 111 int64_t sector_num = 0; 112 int64_t end = -1; 113 uint64_t delay_ns = 0; 114 int error = 0; 115 int ret = 0; 116 int n = 0; 117 void *buf; 118 119 if (!bs->backing) { 120 goto out; 121 } 122 123 s->common.len = bdrv_getlength(bs); 124 if (s->common.len < 0) { 125 ret = s->common.len; 126 goto out; 127 } 128 129 end = s->common.len >> BDRV_SECTOR_BITS; 130 buf = qemu_blockalign(bs, STREAM_BUFFER_SIZE); 131 132 /* Turn on copy-on-read for the whole block device so that guest read 133 * requests help us make progress. Only do this when copying the entire 134 * backing chain since the copy-on-read operation does not take base into 135 * account. 136 */ 137 if (!base) { 138 bdrv_enable_copy_on_read(bs); 139 } 140 141 for (sector_num = 0; sector_num < end; sector_num += n) { 142 bool copy; 143 144 /* Note that even when no rate limit is applied we need to yield 145 * with no pending I/O here so that bdrv_drain_all() returns. 146 */ 147 block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns); 148 if (block_job_is_cancelled(&s->common)) { 149 break; 150 } 151 152 copy = false; 153 154 ret = bdrv_is_allocated(bs, sector_num, 155 STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n); 156 if (ret == 1) { 157 /* Allocated in the top, no need to copy. */ 158 } else if (ret >= 0) { 159 /* Copy if allocated in the intermediate images. Limit to the 160 * known-unallocated area [sector_num, sector_num+n). */ 161 ret = bdrv_is_allocated_above(backing_bs(bs), base, 162 sector_num, n, &n); 163 164 /* Finish early if end of backing file has been reached */ 165 if (ret == 0 && n == 0) { 166 n = end - sector_num; 167 } 168 169 copy = (ret == 1); 170 } 171 trace_stream_one_iteration(s, sector_num, n, ret); 172 if (copy) { 173 ret = stream_populate(blk, sector_num, n, buf); 174 } 175 if (ret < 0) { 176 BlockErrorAction action = 177 block_job_error_action(&s->common, s->on_error, true, -ret); 178 if (action == BLOCK_ERROR_ACTION_STOP) { 179 n = 0; 180 continue; 181 } 182 if (error == 0) { 183 error = ret; 184 } 185 if (action == BLOCK_ERROR_ACTION_REPORT) { 186 break; 187 } 188 } 189 ret = 0; 190 191 /* Publish progress */ 192 s->common.offset += n * BDRV_SECTOR_SIZE; 193 if (copy && s->common.speed) { 194 delay_ns = ratelimit_calculate_delay(&s->limit, n); 195 } 196 } 197 198 if (!base) { 199 bdrv_disable_copy_on_read(bs); 200 } 201 202 /* Do not remove the backing file if an error was there but ignored. */ 203 ret = error; 204 205 qemu_vfree(buf); 206 207 out: 208 /* Modify backing chain and close BDSes in main loop */ 209 data = g_malloc(sizeof(*data)); 210 data->ret = ret; 211 data->reached_end = sector_num == end; 212 block_job_defer_to_main_loop(&s->common, stream_complete, data); 213 } 214 215 static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp) 216 { 217 StreamBlockJob *s = container_of(job, StreamBlockJob, common); 218 219 if (speed < 0) { 220 error_setg(errp, QERR_INVALID_PARAMETER, "speed"); 221 return; 222 } 223 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME); 224 } 225 226 static const BlockJobDriver stream_job_driver = { 227 .instance_size = sizeof(StreamBlockJob), 228 .job_type = BLOCK_JOB_TYPE_STREAM, 229 .set_speed = stream_set_speed, 230 .start = stream_run, 231 }; 232 233 void stream_start(const char *job_id, BlockDriverState *bs, 234 BlockDriverState *base, const char *backing_file_str, 235 int64_t speed, BlockdevOnError on_error, Error **errp) 236 { 237 StreamBlockJob *s; 238 BlockDriverState *iter; 239 int orig_bs_flags; 240 241 /* Make sure that the image is opened in read-write mode */ 242 orig_bs_flags = bdrv_get_flags(bs); 243 if (!(orig_bs_flags & BDRV_O_RDWR)) { 244 if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) { 245 return; 246 } 247 } 248 249 /* Prevent concurrent jobs trying to modify the graph structure here, we 250 * already have our own plans. Also don't allow resize as the image size is 251 * queried only at the job start and then cached. */ 252 s = block_job_create(job_id, &stream_job_driver, bs, 253 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | 254 BLK_PERM_GRAPH_MOD, 255 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED | 256 BLK_PERM_WRITE, 257 speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp); 258 if (!s) { 259 goto fail; 260 } 261 262 /* Block all intermediate nodes between bs and base, because they will 263 * disappear from the chain after this operation. The streaming job reads 264 * every block only once, assuming that it doesn't change, so block writes 265 * and resizes. */ 266 for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) { 267 block_job_add_bdrv(&s->common, "intermediate node", iter, 0, 268 BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED, 269 &error_abort); 270 } 271 272 s->base = base; 273 s->backing_file_str = g_strdup(backing_file_str); 274 s->bs_flags = orig_bs_flags; 275 276 s->on_error = on_error; 277 trace_stream_start(bs, base, s); 278 block_job_start(&s->common); 279 return; 280 281 fail: 282 if (orig_bs_flags != bdrv_get_flags(bs)) { 283 bdrv_reopen(bs, orig_bs_flags, NULL); 284 } 285 } 286