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Re: [Qemu-devel] [PATCH v3 42/44] nbd: Implement NBD_CMD_WRITE_ZEROES on
From: |
Alex Bligh |
Subject: |
Re: [Qemu-devel] [PATCH v3 42/44] nbd: Implement NBD_CMD_WRITE_ZEROES on client |
Date: |
Mon, 25 Apr 2016 13:12:40 +0100 |
On 23 Apr 2016, at 00:40, Eric Blake <address@hidden> wrote:
> 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.
>
> Signed-off-by: Eric Blake <address@hidden>
Reviewed-by: Alex Bligh <address@hidden>
>
> ---
> v3: rebase, tell block layer about our support
> ---
> block/nbd-client.h | 2 ++
> block/nbd-client.c | 34 ++++++++++++++++++++++++++++++++++
> block/nbd.c | 24 ++++++++++++++++++++++++
> 3 files changed, 60 insertions(+)
>
> diff --git a/block/nbd-client.h b/block/nbd-client.h
> index 0867147..07630ab 100644
> --- a/block/nbd-client.h
> +++ b/block/nbd-client.h
> @@ -46,6 +46,8 @@ void nbd_client_close(BlockDriverState *bs);
> int nbd_client_co_discard(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors);
> int nbd_client_co_flush(BlockDriverState *bs);
> +int nbd_client_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, int *flags);
> int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors, QEMUIOVector *qiov, int *flags);
> int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index f20219b..2b6ac27 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -291,6 +291,40 @@ int nbd_client_co_readv(BlockDriverState *bs, int64_t
> sector_num,
> return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
> }
>
> +int nbd_client_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, int *flags)
> +{
> + ssize_t ret;
> + NbdClientSession *client = nbd_get_client_session(bs);
> + struct nbd_request request = { .type = NBD_CMD_WRITE_ZEROES };
> + struct nbd_reply reply;
> +
> + if (!(client->info.flags & NBD_FLAG_SEND_WRITE_ZEROES)) {
> + return -ENOTSUP;
> + }
> +
> + if ((*flags & BDRV_REQ_FUA) && (client->info.flags & NBD_FLAG_SEND_FUA))
> {
> + *flags &= ~BDRV_REQ_FUA;
> + request.flags |= NBD_CMD_FLAG_FUA;
> + }
> + if (!(*flags & BDRV_REQ_MAY_UNMAP)) {
> + request.flags |= NBD_CMD_FLAG_NO_HOLE;
> + }
> +
> + request.from = sector_num * 512;
> + request.len = nb_sectors * 512;
> +
> + nbd_coroutine_start(client, &request);
> + ret = nbd_co_send_request(bs, &request, NULL, 0);
> + if (ret < 0) {
> + reply.error = -ret;
> + } else {
> + nbd_co_receive_reply(client, &request, &reply, NULL, 0);
> + }
> + nbd_coroutine_end(client, &request);
> + return -reply.error;
> +}
> +
> int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors, QEMUIOVector *qiov, int *flags)
> {
> diff --git a/block/nbd.c b/block/nbd.c
> index 34db83e..5172039 100644
> --- a/block/nbd.c
> +++ b/block/nbd.c
> @@ -355,6 +355,26 @@ static int nbd_co_readv(BlockDriverState *bs, int64_t
> sector_num,
> return nbd_client_co_readv(bs, sector_num, nb_sectors, qiov);
> }
>
> +static int nbd_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, BdrvRequestFlags orig_flags)
> +{
> + int flags = orig_flags;
> + int ret;
> +
> + ret = nbd_client_co_write_zeroes(bs, sector_num, nb_sectors, &flags);
> + if (ret < 0) {
> + return ret;
> + }
> +
> + /* The flag wasn't sent to the server, so we need to emulate it with an
> + * explicit flush */
> + if (flags & BDRV_REQ_FUA) {
> + ret = nbd_client_co_flush(bs);
> + }
> +
> + return ret;
> +}
> +
> static int nbd_co_writev_flags(BlockDriverState *bs, int64_t sector_num,
> int nb_sectors, QEMUIOVector *qiov, int flags)
> {
> @@ -388,6 +408,7 @@ static int nbd_co_flush(BlockDriverState *bs)
> static void nbd_refresh_limits(BlockDriverState *bs, Error **errp)
> {
> bs->bl.max_discard = UINT32_MAX >> BDRV_SECTOR_BITS;
> + bs->bl.max_write_zeroes = UINT32_MAX >> BDRV_SECTOR_BITS;
> bs->bl.max_transfer_length = UINT32_MAX >> BDRV_SECTOR_BITS;
> }
>
> @@ -476,6 +497,7 @@ static BlockDriver bdrv_nbd = {
> .bdrv_parse_filename = nbd_parse_filename,
> .bdrv_file_open = nbd_open,
> .bdrv_co_readv = nbd_co_readv,
> + .bdrv_co_write_zeroes = nbd_co_write_zeroes,
> .bdrv_co_writev = nbd_co_writev,
> .bdrv_co_writev_flags = nbd_co_writev_flags,
> .supported_write_flags = BDRV_REQ_FUA,
> @@ -496,6 +518,7 @@ static BlockDriver bdrv_nbd_tcp = {
> .bdrv_parse_filename = nbd_parse_filename,
> .bdrv_file_open = nbd_open,
> .bdrv_co_readv = nbd_co_readv,
> + .bdrv_co_write_zeroes = nbd_co_write_zeroes,
> .bdrv_co_writev = nbd_co_writev,
> .bdrv_co_writev_flags = nbd_co_writev_flags,
> .supported_write_flags = BDRV_REQ_FUA,
> @@ -516,6 +539,7 @@ static BlockDriver bdrv_nbd_unix = {
> .bdrv_parse_filename = nbd_parse_filename,
> .bdrv_file_open = nbd_open,
> .bdrv_co_readv = nbd_co_readv,
> + .bdrv_co_write_zeroes = nbd_co_write_zeroes,
> .bdrv_co_writev = nbd_co_writev,
> .bdrv_co_writev_flags = nbd_co_writev_flags,
> .supported_write_flags = BDRV_REQ_FUA,
> --
> 2.5.5
>
>
--
Alex Bligh
- [Qemu-devel] [PATCH v3 28/44] nbd: Detect servers that send unexpected error values, (continued)
- [Qemu-devel] [PATCH v3 28/44] nbd: Detect servers that send unexpected error values, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 05/44] nbd: Group all Linux-specific ioctl code in one place, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 33/44] nbd: Let client skip portions of server reply, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 30/44] nbd: Treat flags vs. command type as separate fields, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 38/44] block: Add blk_get_opt_transfer_length(), Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 41/44] nbd: Implement NBD_CMD_WRITE_ZEROES on server, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 42/44] nbd: Implement NBD_CMD_WRITE_ZEROES on client, Eric Blake, 2016/04/22
- Re: [Qemu-devel] [PATCH v3 42/44] nbd: Implement NBD_CMD_WRITE_ZEROES on client,
Alex Bligh <=
- [Qemu-devel] [PATCH v3 37/44] nbd: Create struct for tracking export info, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 43/44] nbd: Implement NBD_OPT_BLOCK_SIZE on server, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 19/44] qemu-io: Switch to byte-based block access, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 24/44] qemu-io: Add 'write -f' to test FUA flag, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 25/44] qemu-io: Add 'open -u' to set BDRV_O_UNMAP after the fact, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 27/44] nbd: Use BDRV_REQ_FUA for better FUA where supported, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 26/44] qemu-io: Add 'write -z -u' to test MAY_UNMAP flag, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 34/44] nbd: Less allocation during NBD_OPT_LIST, Eric Blake, 2016/04/22
- [Qemu-devel] [PATCH v3 35/44] nbd: Support shorter handshake, Eric Blake, 2016/04/22