[Qemu-block] [PATCH v9 0/2] mirror: Improve zero write and discard

[Fam Zheng]

v9: Fix the one bug Max found:
    "shrink *= chunk_sectors".

v8: Rebase onto master (didn't pick up Max's rev-by due to non-trivial code
    change).

    The conflict is around removed lines about "max_iov" and "IOV_MAX" due to
    commit 3515727f3, but this also reveals this series forgot that check. So
    this revision adds it back:
    - Two new fields in MirrorBlockJob are added to cache size info:
      target_cluster_sectors and max_iov.
    - mirror_align_cow compares nb_chunks and max_iov, and cut the tail
      appropriately.
    - The orphan trace point is removed from trace-events.

Patch 1 rewrites mirror_iteration. Patch 2 is a small DRY cleaning up.

The main benefit is copying unallocated sectors (both zeroed and discarded)
doesn't go through the iov setup loop, as they don't need it.


Fam Zheng (2):
  mirror: Rewrite mirror_iteration
  mirror: Add mirror_wait_for_io

 block/mirror.c | 365 +++++++++++++++++++++++++++++++++++----------------------
 trace-events   |   1 -
 2 files changed, 225 insertions(+), 141 deletions(-)

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2.4.3