[Qemu-devel] [PATCH 0/3] Remove ->bdrv_pread() internal block layer API (v2)

[Avi Kivity]

The internal block layer API has a wart in the form of the
->bdrv_pread() and ->bdrv_pwrite() methods.  These duplicate
bdrv_read() and bdrv_write(), and are unnatural for a block
device in that they are not sector oriented.

One of the reasons for their existence is the scsi-generic host support.
That is also a wart, as scsi-generic is really a packet (command/response)
rather than a block (random access to sectors) API.  There is also the
wierd negative sector count == byte count thing.

This patchset addresses these warts by adding a new API for scsi-generic
and dropping ->bdrv_pread() and bdrv_pwrite().  While the improvement
falls short of spectacular, it does make further hacking on the block
layer easier as there are fewer callbacks to worry about.

---

Changes since v1:
- rebased against trunk
- performance testing: tested 'rm -rf *; tar xjf ../linux-2.6.22.tar.bz2'
  with a vm snapshot.  While there are significant variances among runs
  (15-25sec), likely due to different ext3 allocation decisions and different
  host caching decisions, there seems to be no regression due to this patchset.

Avi Kivity (3):
  Add specialized block driver scsi generic API
  Add internal scsi generic block API
  Drop internal bdrv_pread()/bdrv_pwrite() APIs

 block-raw-posix.c |   50 ++++++++++++++++++++++++--
 block-raw-win32.c |   20 ++++++----
 block.c           |  101 +++++++++++++++--------------------------------------
 block.h           |    8 ++++
 block_int.h       |   14 +++++--
 hw/scsi-generic.c |   39 +++++++++++---------
 6 files changed, 126 insertions(+), 106 deletions(-)