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