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 "qapi/qmp/qdict.h"
  21 #include "qemu/ratelimit.h"
  22 #include "sysemu/block-backend.h"
  23 #include "block/copy-on-read.h"
  24
  25 enum {
  26     /*
  27      * Maximum chunk size to feed to copy-on-read.  This should be
  28      * large enough to process multiple clusters in a single call, so
  29      * that populating contiguous regions of the image is efficient.
  30      */
  31     STREAM_CHUNK = 512 * 1024, /* in bytes */
  32 };
  33
  34 typedef struct StreamBlockJob {
  35     BlockJob common;
  36     BlockDriverState *base_overlay; /* COW overlay (stream from this) */
  37     BlockDriverState *above_base;   /* Node directly above the base */
  38     BlockDriverState *cor_filter_bs;
  39     BlockDriverState *target_bs;
  40     BlockdevOnError on_error;
  41     char *backing_file_str;
  42     bool bs_read_only;
  43 } StreamBlockJob;
  44
  45 static int coroutine_fn stream_populate(BlockBackend *blk,
  46                                         int64_t offset, uint64_t bytes)
  47 {
  48     assert(bytes < SIZE_MAX);
  49
  50     return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
  51 }
  52
  53 static int stream_prepare(Job *job)
  54 {
  55     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
  56     BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
  57     BlockDriverState *base = bdrv_filter_or_cow_bs(s->above_base);
  58     BlockDriverState *unfiltered_base = bdrv_skip_filters(base);
  59     Error *local_err = NULL;
  60     int ret = 0;
  61
  62     /* We should drop filter at this point, as filter hold the backing chain */
  63     bdrv_cor_filter_drop(s->cor_filter_bs);
  64     s->cor_filter_bs = NULL;
  65
  66     if (bdrv_cow_child(unfiltered_bs)) {
  67         const char *base_id = NULL, *base_fmt = NULL;
  68         if (unfiltered_base) {
  69             base_id = s->backing_file_str ?: unfiltered_base->filename;
  70             if (unfiltered_base->drv) {
  71                 base_fmt = unfiltered_base->drv->format_name;
  72             }
  73         }
  74         bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
  75         ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
  76         if (local_err) {
  77             error_report_err(local_err);
  78             return -EPERM;
  79         }
  80     }
  81
  82     return ret;
  83 }
  84
  85 static void stream_clean(Job *job)
  86 {
  87     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
  88     BlockJob *bjob = &s->common;
  89
  90     if (s->cor_filter_bs) {
  91         bdrv_cor_filter_drop(s->cor_filter_bs);
  92         s->cor_filter_bs = NULL;
  93     }
  94
  95     /* Reopen the image back in read-only mode if necessary */
  96     if (s->bs_read_only) {
  97         /* Give up write permissions before making it read-only */
  98         blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
  99         bdrv_reopen_set_read_only(s->target_bs, true, NULL);
 100     }
 101
 102     g_free(s->backing_file_str);
 103 }
 104
 105 static int coroutine_fn stream_run(Job *job, Error **errp)
 106 {
 107     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
 108     BlockBackend *blk = s->common.blk;
 109     BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
 110     int64_t len;
 111     int64_t offset = 0;
 112     uint64_t delay_ns = 0;
 113     int error = 0;
 114     int64_t n = 0; /* bytes */
 115
 116     if (unfiltered_bs == s->base_overlay) {
 117         /* Nothing to stream */
 118         return 0;
 119     }
 120
 121     len = bdrv_getlength(s->target_bs);
 122     if (len < 0) {
 123         return len;
 124     }
 125     job_progress_set_remaining(&s->common.job, len);
 126
 127     for ( ; offset < len; offset += n) {
 128         bool copy;
 129         int ret;
 130
 131         /* Note that even when no rate limit is applied we need to yield
 132          * with no pending I/O here so that bdrv_drain_all() returns.
 133          */
 134         job_sleep_ns(&s->common.job, delay_ns);
 135         if (job_is_cancelled(&s->common.job)) {
 136             break;
 137         }
 138
 139         copy = false;
 140
 141         ret = bdrv_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n);
 142         if (ret == 1) {
 143             /* Allocated in the top, no need to copy.  */
 144         } else if (ret >= 0) {
 145             /* Copy if allocated in the intermediate images.  Limit to the
 146              * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE).  */
 147             ret = bdrv_is_allocated_above(bdrv_cow_bs(unfiltered_bs),
 148                                           s->base_overlay, true,
 149                                           offset, n, &n);
 150             /* Finish early if end of backing file has been reached */
 151             if (ret == 0 && n == 0) {
 152                 n = len - offset;
 153             }
 154
 155             copy = (ret > 0);
 156         }
 157         trace_stream_one_iteration(s, offset, n, ret);
 158         if (copy) {
 159             ret = stream_populate(blk, offset, n);
 160         }
 161         if (ret < 0) {
 162             BlockErrorAction action =
 163                 block_job_error_action(&s->common, s->on_error, true, -ret);
 164             if (action == BLOCK_ERROR_ACTION_STOP) {
 165                 n = 0;
 166                 continue;
 167             }
 168             if (error == 0) {
 169                 error = ret;
 170             }
 171             if (action == BLOCK_ERROR_ACTION_REPORT) {
 172                 break;
 173             }
 174         }
 175
 176         /* Publish progress */
 177         job_progress_update(&s->common.job, n);
 178         if (copy) {
 179             delay_ns = block_job_ratelimit_get_delay(&s->common, n);
 180         } else {
 181             delay_ns = 0;
 182         }
 183     }
 184
 185     /* Do not remove the backing file if an error was there but ignored. */
 186     return error;
 187 }
 188
 189 static const BlockJobDriver stream_job_driver = {
 190     .job_driver = {
 191         .instance_size = sizeof(StreamBlockJob),
 192         .job_type      = JOB_TYPE_STREAM,
 193         .free          = block_job_free,
 194         .run           = stream_run,
 195         .prepare       = stream_prepare,
 196         .clean         = stream_clean,
 197         .user_resume   = block_job_user_resume,
 198     },
 199 };
 200
 201 void stream_start(const char *job_id, BlockDriverState *bs,
 202                   BlockDriverState *base, const char *backing_file_str,
 203                   BlockDriverState *bottom,
 204                   int creation_flags, int64_t speed,
 205                   BlockdevOnError on_error,
 206                   const char *filter_node_name,
 207                   Error **errp)
 208 {
 209     StreamBlockJob *s;
 210     BlockDriverState *iter;
 211     bool bs_read_only;
 212     int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
 213     BlockDriverState *base_overlay;
 214     BlockDriverState *cor_filter_bs = NULL;
 215     BlockDriverState *above_base;
 216     QDict *opts;
 217
 218     assert(!(base && bottom));
 219     assert(!(backing_file_str && bottom));
 220
 221     if (bottom) {
 222         /*
 223          * New simple interface. The code is written in terms of old interface
 224          * with @base parameter (still, it doesn't freeze link to base, so in
 225          * this mean old code is correct for new interface). So, for now, just
 226          * emulate base_overlay and above_base. Still, when old interface
 227          * finally removed, we should refactor code to use only "bottom", but
 228          * not "*base*" things.
 229          */
 230         assert(!bottom->drv->is_filter);
 231         base_overlay = above_base = bottom;
 232     } else {
 233         base_overlay = bdrv_find_overlay(bs, base);
 234         if (!base_overlay) {
 235             error_setg(errp, "'%s' is not in the backing chain of '%s'",
 236                        base->node_name, bs->node_name);
 237             return;
 238         }
 239
 240         /*
 241          * Find the node directly above @base.  @base_overlay is a COW overlay,
 242          * so it must have a bdrv_cow_child(), but it is the immediate overlay
 243          * of @base, so between the two there can only be filters.
 244          */
 245         above_base = base_overlay;
 246         if (bdrv_cow_bs(above_base) != base) {
 247             above_base = bdrv_cow_bs(above_base);
 248             while (bdrv_filter_bs(above_base) != base) {
 249                 above_base = bdrv_filter_bs(above_base);
 250             }
 251         }
 252     }
 253
 254     /* Make sure that the image is opened in read-write mode */
 255     bs_read_only = bdrv_is_read_only(bs);
 256     if (bs_read_only) {
 257         int ret;
 258         /* Hold the chain during reopen */
 259         if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
 260             return;
 261         }
 262
 263         ret = bdrv_reopen_set_read_only(bs, false, errp);
 264
 265         /* failure, or cor-filter will hold the chain */
 266         bdrv_unfreeze_backing_chain(bs, above_base);
 267
 268         if (ret < 0) {
 269             return;
 270         }
 271     }
 272
 273     opts = qdict_new();
 274
 275     qdict_put_str(opts, "driver", "copy-on-read");
 276     qdict_put_str(opts, "file", bdrv_get_node_name(bs));
 277     /* Pass the base_overlay node name as 'bottom' to COR driver */
 278     qdict_put_str(opts, "bottom", base_overlay->node_name);
 279     if (filter_node_name) {
 280         qdict_put_str(opts, "node-name", filter_node_name);
 281     }
 282
 283     cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
 284     if (!cor_filter_bs) {
 285         goto fail;
 286     }
 287
 288     if (!filter_node_name) {
 289         cor_filter_bs->implicit = true;
 290     }
 291
 292     s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
 293                          BLK_PERM_CONSISTENT_READ,
 294                          basic_flags | BLK_PERM_WRITE,
 295                          speed, creation_flags, NULL, NULL, errp);
 296     if (!s) {
 297         goto fail;
 298     }
 299
 300     /*
 301      * Prevent concurrent jobs trying to modify the graph structure here, we
 302      * already have our own plans. Also don't allow resize as the image size is
 303      * queried only at the job start and then cached.
 304      */
 305     if (block_job_add_bdrv(&s->common, "active node", bs, 0,
 306                            basic_flags | BLK_PERM_WRITE, &error_abort)) {
 307         goto fail;
 308     }
 309
 310     /* Block all intermediate nodes between bs and base, because they will
 311      * disappear from the chain after this operation. The streaming job reads
 312      * every block only once, assuming that it doesn't change, so forbid writes
 313      * and resizes. Reassign the base node pointer because the backing BS of the
 314      * bottom node might change after the call to bdrv_reopen_set_read_only()
 315      * due to parallel block jobs running.
 316      * above_base node might change after the call to
 317      * bdrv_reopen_set_read_only() due to parallel block jobs running.
 318      */
 319     base = bdrv_filter_or_cow_bs(above_base);
 320     for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
 321          iter = bdrv_filter_or_cow_bs(iter))
 322     {
 323         block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
 324                            basic_flags, &error_abort);
 325     }
 326
 327     s->base_overlay = base_overlay;
 328     s->above_base = above_base;
 329     s->backing_file_str = g_strdup(backing_file_str);
 330     s->cor_filter_bs = cor_filter_bs;
 331     s->target_bs = bs;
 332     s->bs_read_only = bs_read_only;
 333
 334     s->on_error = on_error;
 335     trace_stream_start(bs, base, s);
 336     job_start(&s->common.job);
 337     return;
 338
 339 fail:
 340     if (cor_filter_bs) {
 341         bdrv_cor_filter_drop(cor_filter_bs);
 342     }
 343     if (bs_read_only) {
 344         bdrv_reopen_set_read_only(bs, true, NULL);
 345     }
 346 }