qemu

stream.c (11954B)

---

 /*
  * Image streaming
  *
  * Copyright IBM, Corp. 2011
  *
  * Authors:
  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
  *
  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  * See the COPYING.LIB file in the top-level directory.
  *
  */
 
 #include "qemu/osdep.h"
 #include "trace.h"
 #include "block/block_int.h"
 #include "block/blockjob_int.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qdict.h"
 #include "qemu/ratelimit.h"
 #include "sysemu/block-backend.h"
 #include "block/copy-on-read.h"
 
 enum {
     /*
      * Maximum chunk size to feed to copy-on-read.  This should be
      * large enough to process multiple clusters in a single call, so
      * that populating contiguous regions of the image is efficient.
      */
     STREAM_CHUNK = 512 * 1024, /* in bytes */
 };
 
 typedef struct StreamBlockJob {
     BlockJob common;
     BlockBackend *blk;
     BlockDriverState *base_overlay; /* COW overlay (stream from this) */
     BlockDriverState *above_base;   /* Node directly above the base */
     BlockDriverState *cor_filter_bs;
     BlockDriverState *target_bs;
     BlockdevOnError on_error;
     char *backing_file_str;
     bool bs_read_only;
 } StreamBlockJob;
 
 static int coroutine_fn stream_populate(BlockBackend *blk,
                                         int64_t offset, uint64_t bytes)
 {
     assert(bytes < SIZE_MAX);
 
     return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
 }
 
 static int stream_prepare(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
     BlockDriverState *base;
     BlockDriverState *unfiltered_base;
     Error *local_err = NULL;
     int ret = 0;
 
     /* We should drop filter at this point, as filter hold the backing chain */
     bdrv_cor_filter_drop(s->cor_filter_bs);
     s->cor_filter_bs = NULL;
 
     bdrv_subtree_drained_begin(s->above_base);
 
     base = bdrv_filter_or_cow_bs(s->above_base);
     if (base) {
         bdrv_ref(base);
     }
 
     unfiltered_base = bdrv_skip_filters(base);
 
     if (bdrv_cow_child(unfiltered_bs)) {
         const char *base_id = NULL, *base_fmt = NULL;
         if (unfiltered_base) {
             base_id = s->backing_file_str ?: unfiltered_base->filename;
             if (unfiltered_base->drv) {
                 base_fmt = unfiltered_base->drv->format_name;
             }
         }
 
         bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
         ret = bdrv_change_backing_file(unfiltered_bs, base_id, base_fmt, false);
         if (local_err) {
             error_report_err(local_err);
             ret = -EPERM;
             goto out;
         }
     }
 
 out:
     if (base) {
         bdrv_unref(base);
     }
     bdrv_subtree_drained_end(s->above_base);
     return ret;
 }
 
 static void stream_clean(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
 
     if (s->cor_filter_bs) {
         bdrv_cor_filter_drop(s->cor_filter_bs);
         s->cor_filter_bs = NULL;
     }
 
     blk_unref(s->blk);
     s->blk = NULL;
 
     /* Reopen the image back in read-only mode if necessary */
     if (s->bs_read_only) {
         /* Give up write permissions before making it read-only */
         bdrv_reopen_set_read_only(s->target_bs, true, NULL);
     }
 
     g_free(s->backing_file_str);
 }
 
 static int coroutine_fn stream_run(Job *job, Error **errp)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
     int64_t len;
     int64_t offset = 0;
     uint64_t delay_ns = 0;
     int error = 0;
     int64_t n = 0; /* bytes */
 
     if (unfiltered_bs == s->base_overlay) {
         /* Nothing to stream */
         return 0;
     }
 
     len = bdrv_getlength(s->target_bs);
     if (len < 0) {
         return len;
     }
     job_progress_set_remaining(&s->common.job, len);
 
     for ( ; offset < len; offset += n) {
         bool copy;
         int ret;
 
         /* Note that even when no rate limit is applied we need to yield
          * with no pending I/O here so that bdrv_drain_all() returns.
          */
         job_sleep_ns(&s->common.job, delay_ns);
         if (job_is_cancelled(&s->common.job)) {
             break;
         }
 
         copy = false;
 
         ret = bdrv_is_allocated(unfiltered_bs, offset, STREAM_CHUNK, &n);
         if (ret == 1) {
             /* Allocated in the top, no need to copy.  */
         } else if (ret >= 0) {
             /* Copy if allocated in the intermediate images.  Limit to the
              * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE).  */
             ret = bdrv_is_allocated_above(bdrv_cow_bs(unfiltered_bs),
                                           s->base_overlay, true,
                                           offset, n, &n);
             /* Finish early if end of backing file has been reached */
             if (ret == 0 && n == 0) {
                 n = len - offset;
             }
 
             copy = (ret > 0);
         }
         trace_stream_one_iteration(s, offset, n, ret);
         if (copy) {
             ret = stream_populate(s->blk, offset, n);
         }
         if (ret < 0) {
             BlockErrorAction action =
                 block_job_error_action(&s->common, s->on_error, true, -ret);
             if (action == BLOCK_ERROR_ACTION_STOP) {
                 n = 0;
                 continue;
             }
             if (error == 0) {
                 error = ret;
             }
             if (action == BLOCK_ERROR_ACTION_REPORT) {
                 break;
             }
         }
 
         /* Publish progress */
         job_progress_update(&s->common.job, n);
         if (copy) {
             delay_ns = block_job_ratelimit_get_delay(&s->common, n);
         } else {
             delay_ns = 0;
         }
     }
 
     /* Do not remove the backing file if an error was there but ignored. */
     return error;
 }
 
 static const BlockJobDriver stream_job_driver = {
     .job_driver = {
         .instance_size = sizeof(StreamBlockJob),
         .job_type      = JOB_TYPE_STREAM,
         .free          = block_job_free,
         .run           = stream_run,
         .prepare       = stream_prepare,
         .clean         = stream_clean,
         .user_resume   = block_job_user_resume,
     },
 };
 
 void stream_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *base, const char *backing_file_str,
                   BlockDriverState *bottom,
                   int creation_flags, int64_t speed,
                   BlockdevOnError on_error,
                   const char *filter_node_name,
                   Error **errp)
 {
     StreamBlockJob *s = NULL;
     BlockDriverState *iter;
     bool bs_read_only;
     int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
     BlockDriverState *base_overlay;
     BlockDriverState *cor_filter_bs = NULL;
     BlockDriverState *above_base;
     QDict *opts;
     int ret;
 
     GLOBAL_STATE_CODE();
 
     assert(!(base && bottom));
     assert(!(backing_file_str && bottom));
 
     if (bottom) {
         /*
          * New simple interface. The code is written in terms of old interface
          * with @base parameter (still, it doesn't freeze link to base, so in
          * this mean old code is correct for new interface). So, for now, just
          * emulate base_overlay and above_base. Still, when old interface
          * finally removed, we should refactor code to use only "bottom", but
          * not "*base*" things.
          */
         assert(!bottom->drv->is_filter);
         base_overlay = above_base = bottom;
     } else {
         base_overlay = bdrv_find_overlay(bs, base);
         if (!base_overlay) {
             error_setg(errp, "'%s' is not in the backing chain of '%s'",
                        base->node_name, bs->node_name);
             return;
         }
 
         /*
          * Find the node directly above @base.  @base_overlay is a COW overlay,
          * so it must have a bdrv_cow_child(), but it is the immediate overlay
          * of @base, so between the two there can only be filters.
          */
         above_base = base_overlay;
         if (bdrv_cow_bs(above_base) != base) {
             above_base = bdrv_cow_bs(above_base);
             while (bdrv_filter_bs(above_base) != base) {
                 above_base = bdrv_filter_bs(above_base);
             }
         }
     }
 
     /* Make sure that the image is opened in read-write mode */
     bs_read_only = bdrv_is_read_only(bs);
     if (bs_read_only) {
         int ret;
         /* Hold the chain during reopen */
         if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
             return;
         }
 
         ret = bdrv_reopen_set_read_only(bs, false, errp);
 
         /* failure, or cor-filter will hold the chain */
         bdrv_unfreeze_backing_chain(bs, above_base);
 
         if (ret < 0) {
             return;
         }
     }
 
     opts = qdict_new();
 
     qdict_put_str(opts, "driver", "copy-on-read");
     qdict_put_str(opts, "file", bdrv_get_node_name(bs));
     /* Pass the base_overlay node name as 'bottom' to COR driver */
     qdict_put_str(opts, "bottom", base_overlay->node_name);
     if (filter_node_name) {
         qdict_put_str(opts, "node-name", filter_node_name);
     }
 
     cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
     if (!cor_filter_bs) {
         goto fail;
     }
 
     if (!filter_node_name) {
         cor_filter_bs->implicit = true;
     }
 
     s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
                          0, BLK_PERM_ALL,
                          speed, creation_flags, NULL, NULL, errp);
     if (!s) {
         goto fail;
     }
 
     s->blk = blk_new_with_bs(cor_filter_bs, BLK_PERM_CONSISTENT_READ,
                              basic_flags | BLK_PERM_WRITE, errp);
     if (!s->blk) {
         goto fail;
     }
     /*
      * Disable request queuing in the BlockBackend to avoid deadlocks on drain:
      * The job reports that it's busy until it reaches a pause point.
      */
     blk_set_disable_request_queuing(s->blk, true);
     blk_set_allow_aio_context_change(s->blk, true);
 
     /*
      * Prevent concurrent jobs trying to modify the graph structure here, we
      * already have our own plans. Also don't allow resize as the image size is
      * queried only at the job start and then cached.
      */
     if (block_job_add_bdrv(&s->common, "active node", bs, 0,
                            basic_flags | BLK_PERM_WRITE, errp)) {
         goto fail;
     }
 
     /* Block all intermediate nodes between bs and base, because they will
      * disappear from the chain after this operation. The streaming job reads
      * every block only once, assuming that it doesn't change, so forbid writes
      * and resizes. Reassign the base node pointer because the backing BS of the
      * bottom node might change after the call to bdrv_reopen_set_read_only()
      * due to parallel block jobs running.
      * above_base node might change after the call to
      * bdrv_reopen_set_read_only() due to parallel block jobs running.
      */
     base = bdrv_filter_or_cow_bs(above_base);
     for (iter = bdrv_filter_or_cow_bs(bs); iter != base;
          iter = bdrv_filter_or_cow_bs(iter))
     {
         ret = block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
                                  basic_flags, errp);
         if (ret < 0) {
             goto fail;
         }
     }
 
     s->base_overlay = base_overlay;
     s->above_base = above_base;
     s->backing_file_str = g_strdup(backing_file_str);
     s->cor_filter_bs = cor_filter_bs;
     s->target_bs = bs;
     s->bs_read_only = bs_read_only;
 
     s->on_error = on_error;
     trace_stream_start(bs, base, s);
     job_start(&s->common.job);
     return;
 
 fail:
     if (s) {
         job_early_fail(&s->common.job);
     }
     if (cor_filter_bs) {
         bdrv_cor_filter_drop(cor_filter_bs);
     }
     if (bs_read_only) {
         bdrv_reopen_set_read_only(bs, true, NULL);
     }
 }