[Qemu-devel] [PATCH V11 0/8] qcow2: rollback the modification on fail in snapshot creation

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

V2:
  1: all fail case will goto fail section.
  2: add the goto code.

v3:
  Address Stefan's comments:
  2: don't goto fail after allocation failure.
  3: use sn->l1size correctly in qcow2_free_cluster().
  4-7: add test case to verify the error paths.
  Other:
  1: new patch fix a existing bug, which will be exposed in error path test.

v4:
  General change:
  rebased on upstream since error path for qcow2_write_snapshots() already
exist in upstream. removed old patch 1 since it is fixed by Max in upstream.
  5: moved the snapshot_l1_update event just before write operation, instead of
before overlap check, since it is more straight.
  6: remove a duplicated error path test about flush after snapshot list
update, add a filter which replace number to X, since now in error in report
detailed message including error cluster number.
  Address Stefan's comments:
  1, 2, 4: add *errp to store detailed error message, instead of error_report()
and compile time determined debug printf message.
  3: do not free cluster when fail in header update for safety reason.
  Address Eric's comments:
  1, 2, 4: add *errp to store detailed error message, instead of error_report()
and compile time determined debug printf message.
  5: squashed patches that add and use debug events.
  6: added comments about test only on Linux.

v5:
  General change:
  6: rebased on upstream, use case number 070, adjust 070.out due to error
message change in this version.

  Address Max's comments:
  1 use error_setg_errno() when possible, remove "ret =" in functions when
possible since the function does not need to return int value, fix 32bit/
64bit issue in printf for "sizeof" and "offse", typo fix.
  2 use error_setg_errno() when possible, fix 32bit/64bit issue in printf
for "sizeof" and "offse", typo fix.
  3 typo fix in comments.
  5 typo fix in commit message.

  Address Eric's comments:
  2 fix 32bit/64bit issue in printf for "sizeof" and "offse".

v6:
  Address Jeff's comments:
  6: add quote for image name in test case.

v7:
  Rebased on Stefan's block tree, since I need to test after Fam's
cache mode series.
  6: change case number to 075 to avoid conflict, add a comments in
case that it covers only default cache mode, qemu-img snapshot would
not be affected by case's cache setting.

v8:
  Address Stefan's comments:
  1/8: typo fix.
  2/8: remove the type case for sizeof and offsetof.
  3/8, 4/8: new patches help appending error message and detect error.
  5/8: old patch that skip cluster free when header update fail, is removed.
Instead, this patch improved qcow2_write_snapshots()'s rollback procedure by
restore header.
  6/8: new variable *err_rollback is introduced to detect sub function's
rollback error. With new function introduced by patch 3/8, message pending
is simplified so old variable Error *err is removed. Renamed code section
"dealloc_cluster" to "dealloc_l1_table" to tip better.
  Note: patch 5/8 and 6/8 does a full mirrored rollback operation, and
follows the rule that skip following steps when one step fail in rollback
procedure.
  8/8: changed the qcow2 header update fail case correspondly.

v9:
  Address Peter's comments:
  3/8: rename *err to *errp in API param, it works like error_setg()
when *errp is not set.

v10:
  Address Max's comments:
  5/8, 6/8: Better commit message and error message.

v11:
  rebased on upstream.

Wenchao Xia (8):
  1 snapshot: add parameter *errp in snapshot create
  2 qcow2: add error message in qcow2_write_snapshots()
  3 util: add error_append()
  4 qcow2: return int for qcow2_free_clusters()
  5 qcow2: full rollback on fail in qcow2_write_snapshots()
  6 qcow2: rollback on fail in qcow2_snapshot_create()
  7 blkdebug: add debug events for snapshot
  8 qemu-iotests: add test for qcow2 snapshot

 block/blkdebug.c                 |    4 +
 block/qcow2-refcount.c           |    8 +-
 block/qcow2-snapshot.c           |  164 ++++++++++++++++++++++++-----
 block/qcow2.h                    |   10 +-
 block/rbd.c                      |   19 ++--
 block/sheepdog.c                 |   28 +++--
 block/snapshot.c                 |   19 +++-
 blockdev.c                       |   10 +-
 include/block/block.h            |    4 +
 include/block/block_int.h        |    5 +-
 include/block/snapshot.h         |    5 +-
 include/qapi/error.h             |    6 +
 qemu-img.c                       |   10 +-
 savevm.c                         |   12 ++-
 tests/qemu-iotests/075           |  216 ++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/075.out       |   32 ++++++
 tests/qemu-iotests/common.filter |    7 ++
 tests/qemu-iotests/group         |    1 +
 util/error.c                     |   44 +++++++-
 19 files changed, 523 insertions(+), 81 deletions(-)
 create mode 100755 tests/qemu-iotests/075
 create mode 100644 tests/qemu-iotests/075.out