I already sent (and merged) patches that are meant to prevent users from setting the writethrough option on non-root nodes, where we won't be able to support the feature in the long term because we discovered that writethrough mode only makes sense as a BlockBackend feature. The intention was to allow moving the feature where it belongs in the following release without allowing broken behaviour into the current release.
However, moving the feature involves another few changes in behaviour (which are really fixes as the current behaviour is not what was intended) in some corner cases (most of which became only possible with patches after 2.5), so it seems to be actually preferable to do the full thing now instead of having behaviour changes in two consecutive releases. This series removes all traces of writethrough handling from the BlockDriverState layer and implements it in BlockBackend instead. v2: - Rebased on top of the LUKS patches - Keep .bdrv_co_writev implementation in iscsi/nbd/raw because there are still places calling it instead of .bdrv_co_writev_flags [Max] Kevin Wolf (20): block: Add bdrv_parse_cache_mode() qemu-nbd: Call blk_set_enable_write_cache() explicitly qemu-io: Call blk_set_enable_write_cache() explicitly qemu-img: Expand all BDRV_O_FLAGS uses qemu-img: Call blk_set_enable_write_cache() explicitly xen_disk: Call blk_set_enable_write_cache() explicitly block: blockdev_init(): Call blk_set_enable_write_cache() explicitly block: Always set writeback mode in blk_new_open() block: Handle flush error in bdrv_pwrite_sync() block: Move enable_write_cache to BB level block/qapi: Use blk_enable_write_cache() block: Introduce bdrv_co_writev_flags() iscsi: Support BDRV_REQ_FUA nbd: Support BDRV_REQ_FUA raw: Support BDRV_REQ_FUA block: Use bdrv_parse_cache_mode() in drive_init() qemu-io: Use bdrv_parse_cache_mode() in reopen_f() block: Remove bdrv_parse_cache_flags() block: Remove BDRV_O_CACHE_WB block: Remove bdrv_(set_)enable_write_cache() block.c | 78 +++++--------------------------- block/backup.c | 1 - block/block-backend.c | 45 ++++++++++-------- block/crypto.c | 3 +- block/io.c | 15 ++++-- block/iscsi.c | 30 ++++++------ block/mirror.c | 1 - block/nbd-client.c | 13 +++--- block/nbd-client.h | 2 +- block/nbd.c | 27 ++++++++++- block/parallels.c | 3 +- block/qapi.c | 7 +-- block/qcow.c | 3 +- block/qcow2.c | 9 ++-- block/qed.c | 3 +- block/raw_bsd.c | 17 +++++-- block/sheepdog.c | 5 +- block/vdi.c | 3 +- block/vhdx.c | 3 +- block/vmdk.c | 8 ++-- block/vpc.c | 3 +- block/vvfat.c | 3 +- blockdev.c | 35 ++++++-------- hw/block/xen_disk.c | 5 +- include/block/block.h | 8 ++-- include/block/block_int.h | 8 ++-- include/block/qapi.h | 3 +- qemu-img.c | 81 +++++++++++++++++++-------------- qemu-io-cmds.c | 13 +++++- qemu-io.c | 21 +++++---- qemu-nbd.c | 5 +- tests/qemu-iotests/051 | 2 +- tests/qemu-iotests/051.pc.out | 10 ++-- tests/qemu-iotests/142 | 19 +++++--- tests/qemu-iotests/142.out | 103 ++++++++++++++++++++++++++++-------------- 35 files changed, 320 insertions(+), 275 deletions(-) -- 1.8.3.1
