block/stream.c

   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 offset, uint64_t bytes,
  45                                         void *buf)
  46 {
  47     struct iovec iov = {
  48         .iov_base = buf,
  49         .iov_len  = bytes,
  50     };
  51     QEMUIOVector qiov;
  52
  53     assert(bytes < SIZE_MAX);
  54     qemu_iovec_init_external(&qiov, &iov, 1);
  55
  56     /* Copy-on-read the unallocated clusters */
  57     return blk_co_preadv(blk, offset, qiov.size, &qiov, 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 * BDRV_SECTOR_SIZE,
 172                                    n * BDRV_SECTOR_SIZE, ret);
 173         if (copy) {
 174             ret = stream_populate(blk, sector_num * BDRV_SECTOR_SIZE,
 175                                   n * BDRV_SECTOR_SIZE, buf);
 176         }
 177         if (ret < 0) {
 178             BlockErrorAction action =
 179                 block_job_error_action(&s->common, s->on_error, true, -ret);
 180             if (action == BLOCK_ERROR_ACTION_STOP) {
 181                 n = 0;
 182                 continue;
 183             }
 184             if (error == 0) {
 185                 error = ret;
 186             }
 187             if (action == BLOCK_ERROR_ACTION_REPORT) {
 188                 break;
 189             }
 190         }
 191         ret = 0;
 192
 193         /* Publish progress */
 194         s->common.offset += n * BDRV_SECTOR_SIZE;
 195         if (copy && s->common.speed) {
 196             delay_ns = ratelimit_calculate_delay(&s->limit,
 197                                                  n * BDRV_SECTOR_SIZE);
 198         }
 199     }
 200
 201     if (!base) {
 202         bdrv_disable_copy_on_read(bs);
 203     }
 204
 205     /* Do not remove the backing file if an error was there but ignored.  */
 206     ret = error;
 207
 208     qemu_vfree(buf);
 209
 210 out:
 211     /* Modify backing chain and close BDSes in main loop */
 212     data = g_malloc(sizeof(*data));
 213     data->ret = ret;
 214     data->reached_end = sector_num == end;
 215     block_job_defer_to_main_loop(&s->common, stream_complete, data);
 216 }
 217
 218 static void stream_set_speed(BlockJob *job, int64_t speed, Error **errp)
 219 {
 220     StreamBlockJob *s = container_of(job, StreamBlockJob, common);
 221
 222     if (speed < 0) {
 223         error_setg(errp, QERR_INVALID_PARAMETER, "speed");
 224         return;
 225     }
 226     ratelimit_set_speed(&s->limit, speed, SLICE_TIME);
 227 }
 228
 229 static const BlockJobDriver stream_job_driver = {
 230     .instance_size = sizeof(StreamBlockJob),
 231     .job_type      = BLOCK_JOB_TYPE_STREAM,
 232     .set_speed     = stream_set_speed,
 233     .start         = stream_run,
 234 };
 235
 236 void stream_start(const char *job_id, BlockDriverState *bs,
 237                   BlockDriverState *base, const char *backing_file_str,
 238                   int64_t speed, BlockdevOnError on_error, Error **errp)
 239 {
 240     StreamBlockJob *s;
 241     BlockDriverState *iter;
 242     int orig_bs_flags;
 243
 244     /* Make sure that the image is opened in read-write mode */
 245     orig_bs_flags = bdrv_get_flags(bs);
 246     if (!(orig_bs_flags & BDRV_O_RDWR)) {
 247         if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) {
 248             return;
 249         }
 250     }
 251
 252     /* Prevent concurrent jobs trying to modify the graph structure here, we
 253      * already have our own plans. Also don't allow resize as the image size is
 254      * queried only at the job start and then cached. */
 255     s = block_job_create(job_id, &stream_job_driver, bs,
 256                          BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
 257                          BLK_PERM_GRAPH_MOD,
 258                          BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
 259                          BLK_PERM_WRITE,
 260                          speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
 261     if (!s) {
 262         goto fail;
 263     }
 264
 265     /* Block all intermediate nodes between bs and base, because they will
 266      * disappear from the chain after this operation. The streaming job reads
 267      * every block only once, assuming that it doesn't change, so block writes
 268      * and resizes. */
 269     for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
 270         block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
 271                            BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
 272                            &error_abort);
 273     }
 274
 275     s->base = base;
 276     s->backing_file_str = g_strdup(backing_file_str);
 277     s->bs_flags = orig_bs_flags;
 278
 279     s->on_error = on_error;
 280     trace_stream_start(bs, base, s);
 281     block_job_start(&s->common);
 282     return;
 283
 284 fail:
 285     if (orig_bs_flags != bdrv_get_flags(bs)) {
 286         bdrv_reopen(bs, orig_bs_flags, NULL);
 287     }
 288 }