[Qemu-devel] [PATCH v3 0/6] Auto-fragment large transactions at the block layer

[Eric Blake <eblake@redhat.com>]

We have max_transfer documented in BlockLimits, but while we
honor it during pwrite_zeroes, we were blindly ignoring it
during pwritev and preadv, leading to multiple drivers having
to implement fragmentation themselves.  This series moves
fragmentation to the block layer, then fixes the NBD and iscsi
driver to use it.

qcow2 still does self-fragmenting, but that's because of cluster
boundaries where it really has to do additional work beyond what
the block layer can automatically provide.

Prequisite: Kevin's latest block branch PULL request

Also available as a tag at:
git fetch git://repo.or.cz/qemu/ericb.git nbd-fragment-v3

Changes since v2:
- patch 1, 3: change return semantics to be 0, not bytes, on success,
since at least one caller asserts during 'make check' otherwise

001/6:[0008] [FC] 'block: Fragment reads to max transfer length'
002/6:[----] [--] 'raw_bsd: Don't advertise flags not supported by protocol layer'
003/6:[0002] [FC] 'block: Fragment writes to max transfer length'
004/6:[----] [--] 'nbd: Rely on block layer to break up large requests'
005/6:[----] [--] 'nbd: Drop unused offset parameter'
006/6:[----] [--] 'iscsi: Rely on block layer to break up large requests'

Eric Blake (6):
  block: Fragment reads to max transfer length
  raw_bsd: Don't advertise flags not supported by protocol layer
  block: Fragment writes to max transfer length
  nbd: Rely on block layer to break up large requests
  nbd: Drop unused offset parameter
  iscsi: Rely on block layer to break up large requests

 include/block/nbd.h |  1 -
 nbd/nbd-internal.h  |  4 +--
 block/io.c          | 90 +++++++++++++++++++++++++++++++++++++++--------------
 block/iscsi.c       | 14 +++------
 block/nbd-client.c  | 78 +++++++++++++---------------------------------
 block/nbd.c         | 12 ++-----
 block/raw_bsd.c     |  6 ++--
 nbd/common.c        |  5 +--
 8 files changed, 103 insertions(+), 107 deletions(-)

-- 
2.5.5