Hi all!
There is an idea to make NBD protocol extension to support 64bit
write-zero/discard/block-status commands (commands, which doesn't
transfer user data). It's needed to increase performance of zeroing
large ranges (up to the whole image). Zeroing of the whole image is used
as first step of mirror job, qemu-img convert, it should be also used at
start of backup actually..
We need to support it in block-layer, so we want 64bit write_zeros.
Currently driver handler now have int bytes parameter.
write_zeros path goes through normal pwritev, so we need 64bit write,
and then we need 64bit read for symmetry, and better, let's make all io
path work with 64bit bytes parameter.
Actually most of block-layer already have 64bit parameters: offset is
sometimes int64_t and sometimes uint64_t. bytes parameter is one of
int64_t, uint64_t, int, unsigned int...
I think we need one type for all of this, and this one type is int64_t.
Signed int64_t is a bit better than uint64_t: you can use same variable
to get some result (including error < 0) and than reuse it as an
argument without any type conversion.
So, I propose, as a first step, convert all uint64_t parameters to
int64_t.
Still, I don't have good idea of how to split this into more than 3
patches, so, this is an RFC.
What's next?
Converting write_zero and discard is not as simple: we can't just
s/int/uint64_t/, as some functions may use some int variables for
calculations and this will be broken by something larger than int.
So, I think the simplest way is to add .bdrv_co_pwritev_zeros64 and
.bdrv_co_pdiscard64 and update drivers one-by-one. If at some point all
drivers updated - drop unused 32bit functions, and then drop "64" suffix
from API. If not - we'll live with both APIs.
Another thing to do is updating default limiting of request (currently
they are limited to INT_MAX).
Then we may move some drivers to 64bit discard/write_zero: I think about
qcow2, file-posix and nbd (as a proof-of-concept for already proposed
NBD extension).
Any ideas?
Vladimir Sementsov-Ogievskiy (3):
block: use int64_t as bytes type in tracked requests
block/io: convert generic io path to use int64_t parameters
block: use int64_t instead of uint64_t in driver handlers
include/block/block.h | 8 ++--
include/block/block_int.h | 52 ++++++++++-----------
block/backup-top.c | 5 +-
block/blkdebug.c | 4 +-
block/blklogwrites.c | 4 +-
block/blkreplay.c | 4 +-
block/blkverify.c | 6 +--
block/bochs.c | 2 +-
block/cloop.c | 2 +-
block/commit.c | 2 +-
block/copy-on-read.c | 4 +-
block/crypto.c | 4 +-
block/curl.c | 2 +-
block/dmg.c | 2 +-
block/file-posix.c | 18 ++++----
block/filter-compress.c | 6 +--
block/io.c | 97 ++++++++++++++++++++-------------------
block/iscsi.c | 12 ++---
block/mirror.c | 4 +-
block/nbd.c | 8 ++--
block/nfs.c | 8 ++--
block/null.c | 8 ++--
block/nvme.c | 4 +-
block/qcow.c | 12 ++---
block/qcow2.c | 18 ++++----
block/quorum.c | 8 ++--
block/raw-format.c | 28 +++++------
block/rbd.c | 4 +-
block/throttle.c | 4 +-
block/vdi.c | 4 +-
block/vmdk.c | 8 ++--
block/vpc.c | 4 +-
block/vvfat.c | 6 +--
tests/test-bdrv-drain.c | 8 ++--
block/trace-events | 14 +++---
35 files changed, 192 insertions(+), 192 deletions(-)