diff options
| author | Eric Blake <eblake@redhat.com> | 2016-10-14 13:33:18 -0500 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-11-02 09:28:56 +0100 |
| commit | fa778fffdfafce811bba3dd97de41fb524b861f7 (patch) | |
| tree | 9e44cd06de20db032f56d0aec6ce432318e126a8 /block/nbd.c | |
| parent | 1f4d6d18edfeaea64ae74bf5254b8d0e923dc73f (diff) | |
| download | qemu-fa778fffdfafce811bba3dd97de41fb524b861f7.tar.gz | |
nbd: Implement NBD_CMD_WRITE_ZEROES on client
Upstream NBD protocol recently added the ability to efficiently
write zeroes without having to send the zeroes over the wire,
along with a flag to control whether the client wants a hole.
The generic block code takes care of falling back to the obvious
write of lots of zeroes if we return -ENOTSUP because the server
does not have WRITE_ZEROES.
Ideally, since NBD_CMD_WRITE_ZEROES does not involve any data
over the wire, we want to support transactions that are much
larger than the normal 32M limit imposed on NBD_CMD_WRITE. But
the server may still have a limit smaller than UINT_MAX, so
until experimental NBD protocol additions for advertising various
command sizes is finalized (see [1], [2]), for now we just stick to
the same limits as normal writes.
[1] https://github.com/yoe/nbd/blob/extension-info/doc/proto.md
[2] https://sourceforge.net/p/nbd/mailman/message/35081223/
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-17-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'block/nbd.c')
| -rw-r--r-- | block/nbd.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/block/nbd.c b/block/nbd.c index b281484648..9cff8396f9 100644 --- a/block/nbd.c +++ b/block/nbd.c @@ -466,6 +466,7 @@ static int nbd_co_flush(BlockDriverState *bs) static void nbd_refresh_limits(BlockDriverState *bs, Error **errp) { bs->bl.max_pdiscard = NBD_MAX_BUFFER_SIZE; + bs->bl.max_pwrite_zeroes = NBD_MAX_BUFFER_SIZE; bs->bl.max_transfer = NBD_MAX_BUFFER_SIZE; } @@ -558,6 +559,7 @@ static BlockDriver bdrv_nbd = { .bdrv_file_open = nbd_open, .bdrv_co_preadv = nbd_client_co_preadv, .bdrv_co_pwritev = nbd_client_co_pwritev, + .bdrv_co_pwrite_zeroes = nbd_client_co_pwrite_zeroes, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, .bdrv_co_pdiscard = nbd_client_co_pdiscard, @@ -576,6 +578,7 @@ static BlockDriver bdrv_nbd_tcp = { .bdrv_file_open = nbd_open, .bdrv_co_preadv = nbd_client_co_preadv, .bdrv_co_pwritev = nbd_client_co_pwritev, + .bdrv_co_pwrite_zeroes = nbd_client_co_pwrite_zeroes, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, .bdrv_co_pdiscard = nbd_client_co_pdiscard, @@ -594,6 +597,7 @@ static BlockDriver bdrv_nbd_unix = { .bdrv_file_open = nbd_open, .bdrv_co_preadv = nbd_client_co_preadv, .bdrv_co_pwritev = nbd_client_co_pwritev, + .bdrv_co_pwrite_zeroes = nbd_client_co_pwrite_zeroes, .bdrv_close = nbd_close, .bdrv_co_flush_to_os = nbd_co_flush, .bdrv_co_pdiscard = nbd_client_co_pdiscard, |