Re: [Qemu-devel] [PATCH v19 04/16] block: Replace in_use with operation blocker

[Markus Armbruster]

Fam Zheng <address@hidden> writes:

> This drops BlockDriverState.in_use with op_blockers:
>
>   - Call bdrv_op_block_all in place of bdrv_set_in_use(bs, 1).
>   - Call bdrv_op_unblock_all in place of bdrv_set_in_use(bs, 0).
>   - Check bdrv_op_is_blocked() in place of bdrv_in_use(bs).
>     The specific types are used, e.g. in place of starting block backup,
>     bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP, ...).
>   - Check bdrv_op_blocker_is_empty() in place of assert(!bs->in_use).
>
> Note: there is only bdrv_op_block_all and bdrv_op_unblock_all callers at
> this moment. So although the checks are specific to op types, this
> changes can still be seen as identical logic with previously with
> in_use. The difference is error message are improved because of blocker
> error info.
>
> Signed-off-by: Fam Zheng <address@hidden>
> Reviewed-by: Jeff Cody <address@hidden>
> ---
>  block-migration.c               |  7 +++++--
>  block.c                         | 24 +++++++-----------------
>  blockdev.c                      | 19 +++++++++----------
>  blockjob.c                      | 14 +++++++++-----
>  hw/block/dataplane/virtio-blk.c | 18 ++++++++++++------
>  include/block/block.h           |  2 --
>  include/block/block_int.h       |  1 -
>  include/block/blockjob.h        |  3 +++
>  8 files changed, 45 insertions(+), 43 deletions(-)
>
> diff --git a/block-migration.c b/block-migration.c
> index 56951e0..1656270 100644
> --- a/block-migration.c
> +++ b/block-migration.c
> @@ -59,6 +59,7 @@ typedef struct BlkMigDevState {
>      unsigned long *aio_bitmap;
>      int64_t completed_sectors;
>      BdrvDirtyBitmap *dirty_bitmap;
> +    Error *blocker;
>  } BlkMigDevState;
>  
>  typedef struct BlkMigBlock {
> @@ -361,7 +362,8 @@ static void init_blk_migration_it(void *opaque, 
> BlockDriverState *bs)
>          bmds->completed_sectors = 0;
>          bmds->shared_base = block_mig_state.shared_base;
>          alloc_aio_bitmap(bmds);
> -        bdrv_set_in_use(bs, 1);
> +        error_setg(&bmds->blocker, "block device is in use by migration");
> +        bdrv_op_block_all(bs, bmds->blocker);
>          bdrv_ref(bs);
>  
>          block_mig_state.total_sector_sum += sectors;

Unlike QERR_DEVICE_IN_USE, this message doesn't include the device name.
Did you verify it's not needed to make sense of the message?

> @@ -599,7 +601,8 @@ static void blk_mig_cleanup(void)
>      blk_mig_lock();
>      while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
>          QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
> -        bdrv_set_in_use(bmds->bs, 0);
> +        bdrv_op_unblock_all(bmds->bs, bmds->blocker);
> +        error_free(bmds->blocker);
>          bdrv_unref(bmds->bs);
>          g_free(bmds->aio_bitmap);
>          g_free(bmds);
> diff --git a/block.c b/block.c
> index 32338ca..0747a43 100644
> --- a/block.c
> +++ b/block.c
> @@ -1904,7 +1904,6 @@ static void bdrv_move_feature_fields(BlockDriverState 
> *bs_dest,
>      bs_dest->refcnt             = bs_src->refcnt;
>  
>      /* job */
> -    bs_dest->in_use             = bs_src->in_use;
>      bs_dest->job                = bs_src->job;
>  
>      /* keep the same entry in bdrv_states */
> @@ -1947,7 +1946,7 @@ void bdrv_swap(BlockDriverState *bs_new, 
> BlockDriverState *bs_old)
>      assert(QLIST_EMPTY(&bs_new->dirty_bitmaps));
>      assert(bs_new->job == NULL);
>      assert(bs_new->dev == NULL);
> -    assert(bs_new->in_use == 0);
> +    assert(bdrv_op_blocker_is_empty(bs_new));
>      assert(bs_new->io_limits_enabled == false);
>      assert(!throttle_have_timer(&bs_new->throttle_state));
>  
> @@ -1966,7 +1965,7 @@ void bdrv_swap(BlockDriverState *bs_new, 
> BlockDriverState *bs_old)
>      /* Check a few fields that should remain attached to the device */
>      assert(bs_new->dev == NULL);
>      assert(bs_new->job == NULL);
> -    assert(bs_new->in_use == 0);
> +    assert(bdrv_op_blocker_is_empty(bs_new));
>      assert(bs_new->io_limits_enabled == false);
>      assert(!throttle_have_timer(&bs_new->throttle_state));
>  
> @@ -2011,7 +2010,7 @@ static void bdrv_delete(BlockDriverState *bs)
>  {
>      assert(!bs->dev);
>      assert(!bs->job);
> -    assert(!bs->in_use);
> +    assert(bdrv_op_blocker_is_empty(bs));
>      assert(!bs->refcnt);
>      assert(QLIST_EMPTY(&bs->dirty_bitmaps));
>  
> @@ -2193,7 +2192,8 @@ int bdrv_commit(BlockDriverState *bs)
>          return -ENOTSUP;
>      }
>  
> -    if (bdrv_in_use(bs) || bdrv_in_use(bs->backing_hd)) {
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_COMMIT, NULL) ||
> +        bdrv_op_is_blocked(bs->backing_hd, BLOCK_OP_TYPE_COMMIT, NULL)) {
>          return -EBUSY;
>      }
>  
> @@ -3446,8 +3446,9 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset)
>          return -ENOTSUP;
>      if (bs->read_only)
>          return -EACCES;
> -    if (bdrv_in_use(bs))
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_RESIZE, NULL)) {
>          return -EBUSY;
> +    }
>      ret = drv->bdrv_truncate(bs, offset);
>      if (ret == 0) {
>          ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
> @@ -5344,17 +5345,6 @@ bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
>      return true;
>  }
>  
> -void bdrv_set_in_use(BlockDriverState *bs, int in_use)
> -{
> -    assert(bs->in_use != in_use);
> -    bs->in_use = in_use;
> -}
> -
> -int bdrv_in_use(BlockDriverState *bs)
> -{
> -    return bs->in_use;
> -}
> -
>  void bdrv_iostatus_enable(BlockDriverState *bs)
>  {
>      bs->iostatus_enabled = true;
> diff --git a/blockdev.c b/blockdev.c
> index 7810e9f..5d950fa 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1295,8 +1295,8 @@ static void 
> external_snapshot_prepare(BlkTransactionState *common,
>          return;
>      }
>  
> -    if (bdrv_in_use(state->old_bs)) {
> -        error_set(errp, QERR_DEVICE_IN_USE, device);
> +    if (bdrv_op_is_blocked(state->old_bs,
> +                           BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT, errp)) {
>          return;
>      }
>  
> @@ -1518,8 +1518,7 @@ exit:
>  
>  static void eject_device(BlockDriverState *bs, int force, Error **errp)
>  {
> -    if (bdrv_in_use(bs)) {
> -        error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_EJECT, errp)) {
>          return;
>      }
>      if (!bdrv_dev_has_removable_media(bs)) {
> @@ -1721,14 +1720,16 @@ int do_drive_del(Monitor *mon, const QDict *qdict, 
> QObject **ret_data)
>  {
>      const char *id = qdict_get_str(qdict, "id");
>      BlockDriverState *bs;
> +    Error *local_err = NULL;
>  
>      bs = bdrv_find(id);
>      if (!bs) {
>          qerror_report(QERR_DEVICE_NOT_FOUND, id);
>          return -1;
>      }
> -    if (bdrv_in_use(bs)) {
> -        qerror_report(QERR_DEVICE_IN_USE, id);
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_DRIVE_DEL, &local_err)) {
> +        error_report("%s", error_get_pretty(local_err));
> +        error_free(local_err);
>          return -1;
>      }
>  
> @@ -1984,8 +1985,7 @@ void qmp_drive_backup(const char *device, const char 
> *target,
>          }
>      }
>  
> -    if (bdrv_in_use(bs)) {
> -        error_set(errp, QERR_DEVICE_IN_USE, device);
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
>          return;
>      }
>  
> @@ -2118,8 +2118,7 @@ void qmp_drive_mirror(const char *device, const char 
> *target,
>          }
>      }
>  
> -    if (bdrv_in_use(bs)) {
> -        error_set(errp, QERR_DEVICE_IN_USE, device);
> +    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_MIRROR, errp)) {
>          return;
>      }
>  
> diff --git a/blockjob.c b/blockjob.c
> index cd4784f..60e72f5 100644
> --- a/blockjob.c
> +++ b/blockjob.c
> @@ -41,14 +41,16 @@ void *block_job_create(const BlockJobDriver *driver, 
> BlockDriverState *bs,
>  {
>      BlockJob *job;
>  
> -    if (bs->job || bdrv_in_use(bs)) {
> +    if (bs->job || !bdrv_op_blocker_is_empty(bs)) {
>          error_set(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
>          return NULL;
>      }

Elsewhere, you replace bdrv_in_use() by bdrv_op_is_blocked().  Why not
here?

Doesn't this contradict the commit message?

>      bdrv_ref(bs);
> -    bdrv_set_in_use(bs, 1);
> -
>      job = g_malloc0(driver->instance_size);
> +    error_setg(&job->blocker, "block device is in use by block job: %s",
> +               BlockJobType_lookup[driver->job_type]);
> +    bdrv_op_block_all(bs, job->blocker);
> +
>      job->driver        = driver;
>      job->bs            = bs;
>      job->cb            = cb;
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