As in v1, the series is logically split in two parts.
The first six patches ensure that BDRV_O_NO_CACHE is set for all non-file
protocols. This makes sure that large sectors are handled correctly
for the libiscsi backend.
The next patches add support for arbitrary combinations of host/guest
logical block size even for cache=none. Having guest_block_size >
host_block_size is unsafe in the presence of power failures, while
having guest_block_size < host_block_size is just (possibly) slower.
Physical block size and minimum I/O size are set to the host block
size in order to minimize ill performance behavior. This is a small
guest-visible change, but only if you were hosting your images on a
4k-sector partition _and_ using cache != none:
- 4k-sectors and cache=none used to fail horribly
- filesystem images with cache != none cannot detect they are on a
4k-sector disk, because BLKSSZGET fails
This should be rare enough that it's bearable to trade this for better
defaults.
v1->v2: new patch to set min_io_size and please XFS;
aesthetic changes to patches 2 and 3 suggested by Zhi;
rebase around copy-on-read changes.
Paolo Bonzini (18):
block: do not rely on open_flags for bdrv_is_snapshot
block: store actual flags in bs->open_flags
block: pass protocol flags up to the format
block: non-raw protocols never cache
block: remove enable_write_cache
block: move flag bits together
raw: remove the aligned_buf
block: rename buffer_alignment to guest_block_size
block: add host_block_size
raw: probe host_block_size
iscsi: save host block size
block: allow waiting only for overlapping writes
block: allow waiting at arbitrary granularity
block: protect against "torn reads" for guest_block_size > host_block_size
block: align and serialize I/O when guest_block_size < host_block_size
block: default physical block size to host block size
qemu-io: add blocksize argument to open
block: default min_io_size to host block size when doing rmw
Makefile.objs | 4 +-
block.c | 336 ++++++++++++++++++++++++++++++++++++++++++++++-------
block.h | 18 +---
block/curl.c | 1 +
block/iscsi.c | 3 +
block/nbd.c | 1 +
block/raw-posix.c | 97 +++++++++------
block/raw-win32.c | 42 +++++++
block/rbd.c | 1 +
block/sheepdog.c | 1 +
block/vdi.c | 1 +
block_int.h | 25 ++--
hw/ide/core.c | 2 +-
hw/scsi-disk.c | 4 +-
hw/scsi-generic.c | 2 +-
hw/virtio-blk.c | 4 +-
qemu-io.c | 33 +++++-
trace-events | 1 +
18 files changed, 452 insertions(+), 124 deletions(-)
--
1.7.7.6
