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).
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- Made 'bytes' argument to tracked_request_overlaps() unsigned [Max] - Fixed a corruption bug that came from using outdated RMW buffers after waiting for another request and added some assertions to check the assumptions [Peter] - Fixed bytes vs. sectors error in zero-after-EOF code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 -- 1.8.1.4
