Commit 169407e1 authored by Eric Blake's avatar Eric Blake Committed by Paolo Bonzini
Browse files

nbd: Allow unmap and fua during write zeroes 



Commit fa778fff wired up support to send the NBD_CMD_WRITE_ZEROES,
but forgot to inform the block layer that FUA unmapping of zeroes is
supported.  Without BDRV_REQ_MAY_UNMAP listed as a supported flag,
the block layer will always insist on the NBD layer passing
NBD_CMD_FLAG_NO_HOLE, resulting in the server always allocating
things even when it was desired to let the server punch holes.
Similarly, failing to set BDRV_REQ_FUA means that the client may
send unnecessary NBD_CMD_FLUSH when it could have instead used the
NBD_CMD_FLAG_FUA bit.

CC: qemu-stable@nongnu.org
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Message-Id: <1479413642-22463-2-git-send-email-eblake@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c2a85316

block/nbd-client.c

+4 −0
Original line number Diff line number Diff line
@@ -415,6 +415,10 @@ int nbd_client_init(BlockDriverState *bs, 
    }

    if (client->nbdflags & NBD_FLAG_SEND_FUA) {

        bs->supported_write_flags = BDRV_REQ_FUA;

        bs->supported_zero_flags |= BDRV_REQ_FUA;

    }

    if (client->nbdflags & NBD_FLAG_SEND_WRITE_ZEROES) {

        bs->supported_zero_flags |= BDRV_REQ_MAY_UNMAP;

    }



    qemu_co_mutex_init(&client->send_mutex);