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Re: [Qemu-devel] [PATCH v3 00/29] block: Support for 512b-on-4k emulatio
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [PATCH v3 00/29] block: Support for 512b-on-4k emulation |
Date: |
Wed, 22 Jan 2014 21:30:31 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
On 17/01/14 15:14, Kevin Wolf wrote:
> This patch series adds code to the block layer that allows performing
> I/O requests in smaller granularities than required by the host backend
> (most importantly, O_DIRECT restrictions). It achieves this for reads
> by rounding the request to host-side block boundary, and for writes by
> performing a read-modify-write cycle (and serialising requests
> touching the same block so that the RMW doesn't write back stale data).
Nice, this might really help on s390 (also for KVM) since dasd disks usually
have a 4k sector size. We also have flash systems with 4k block size. Both
disk systems cause lots of trouble with cache=none and friends.
Do you have a tree with these patches, so that I can test those on s390?
>
> Originally I intended to reuse a lot of code from Paolo's previous
> patch series, however as I tried to integrate pread/pwrite, which
> already do a very similar thing (except for considering concurrency),
> and because I wanted to implement zero-copy, most of this series ended
> up being new code.
>
> Zero-copy is possible in a common case because while XFS defauls to a
> 4k sector size and therefore 4k on-disk O_DIRECT alignment for 512E
> disks, it still only has a 512 byte memory alignment requirement.
> (Unfortunately the XFS_IOC_DIOINFO ioctl claims 4k even for memory, but
> we know that the value is wrong and can probe it.)
>
>
> Changes in v2 -> v3:
> - Fixed I/O throttling bypass by converting to byte granularity [Wenchao]
> - Made 'bytes' argument to tracked_request_overlaps() unsigned [Max]
> - Fixed a corruption bug that came from using outdated RMW buffers after
> waiting for another request and added some assertions to check the
> assumptions [Peter]
> - Fixed bytes vs. sectors error in zero-after-EOF code of
> bdrv_co_do_preadv [Max]
> - Removed orphaned protoype in block.h [Max]
> - A qemu-iotests case and some infrastructure to support it
>
> Changes in v1 -> v2:
> - Fixed overlap_bytes calculation in mark_request_serialising()
> - Fixed wait_serialising_requests() deadlock
> - iscsi: Set bs->request_alignment [Peter]
> - iscsi: Query block limits only in iscsi_open() when no other request
> are in flight, and in iscsi_refresh_limits() copy the stored values
> into bs->bl [Peter]
>
> Changes in RFC -> v1:
> - Moved opt_mem_alignment into BlockLimits [Paolo]
> - Changed BlockLimits in turn to work a bit more like the
> .bdrv_opt_mem_align() callback of the RFC; allows updating the
> BlockLimits later when the chain changes or bdrv_reopen() toggles
> O_DIRECT
> - Fixed a typo in a commit message [Eric]
>
>
> Kevin Wolf (26):
> block: Move initialisation of BlockLimits to bdrv_refresh_limits()
> block: Inherit opt_transfer_length
> block: Update BlockLimits when they might have changed
> qemu_memalign: Allow small alignments
> block: Detect unaligned length in bdrv_qiov_is_aligned()
> block: Don't use guest sector size for qemu_blockalign()
> block: Introduce bdrv_aligned_preadv()
> block: Introduce bdrv_co_do_preadv()
> block: Introduce bdrv_aligned_pwritev()
> block: write: Handle COR dependency after I/O throttling
> block: Introduce bdrv_co_do_pwritev()
> block: Switch BdrvTrackedRequest to byte granularity
> block: Allow waiting for overlapping requests between begin/end
> block: Make zero-after-EOF work with larger alignment
> block: Generalise and optimise COR serialisation
> block: Make overlap range for serialisation dynamic
> block: Allow wait_serialising_requests() at any point
> block: Align requests in bdrv_co_do_pwritev()
> block: Assert serialisation assumptions in pwritev
> block: Change coroutine wrapper to byte granularity
> block: Make bdrv_pread() a bdrv_prwv_co() wrapper
> block: Make bdrv_pwrite() a bdrv_prwv_co() wrapper
> blkdebug: Make required alignment configurable
> qemu-io: New command 'sleep'
> qemu-iotests: Test pwritev RMW logic
> block: Switch bdrv_io_limits_intercept() to byte granularity
>
> Paolo Bonzini (3):
> block: rename buffer_alignment to guest_block_size
> raw: Probe required direct I/O alignment
> iscsi: Set bs->request_alignment
>
> block.c | 644
> +++++++++++++++++++++++++++++++--------------
> block/backup.c | 7 +-
> block/blkdebug.c | 24 ++
> block/iscsi.c | 47 ++--
> block/qcow2.c | 11 +-
> block/qed.c | 11 +-
> block/raw-posix.c | 102 +++++--
> block/raw-win32.c | 41 +++
> block/stream.c | 2 +
> block/vmdk.c | 22 +-
> hw/block/virtio-blk.c | 2 +-
> hw/ide/core.c | 2 +-
> hw/scsi/scsi-disk.c | 2 +-
> hw/scsi/scsi-generic.c | 2 +-
> include/block/block.h | 15 +-
> include/block/block_int.h | 27 +-
> qemu-io-cmds.c | 42 +++
> tests/qemu-iotests/077 | 278 +++++++++++++++++++
> tests/qemu-iotests/077.out | 202 ++++++++++++++
> tests/qemu-iotests/group | 1 +
> util/oslib-posix.c | 5 +
> 21 files changed, 1234 insertions(+), 255 deletions(-)
> create mode 100755 tests/qemu-iotests/077
> create mode 100644 tests/qemu-iotests/077.out
>
- [Qemu-devel] [PATCH v3 26/29] blkdebug: Make required alignment configurable, (continued)