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(-)