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[Qemu-block] [PATCH v5 14/14] nbd: Implement NBD_CMD_WRITE_ZEROES on cli
From: |
Eric Blake |
Subject: |
[Qemu-block] [PATCH v5 14/14] nbd: Implement NBD_CMD_WRITE_ZEROES on client |
Date: |
Mon, 18 Jul 2016 22:08:01 -0600 |
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 <address@hidden>
---
v5: enhance commit message
v4: rebase to byte-based limits
v3: rebase, tell block layer about our support
---
block/nbd-client.h | 2 ++
block/nbd-client.c | 35 +++++++++++++++++++++++++++++++++++
block/nbd.c | 4 ++++
3 files changed, 41 insertions(+)
diff --git a/block/nbd-client.h b/block/nbd-client.h
index 044aca4..2cfe377 100644
--- a/block/nbd-client.h
+++ b/block/nbd-client.h
@@ -48,6 +48,8 @@ int nbd_client_co_pdiscard(BlockDriverState *bs, int64_t
offset, int count);
int nbd_client_co_flush(BlockDriverState *bs);
int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov, int flags);
+int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+ int count, BdrvRequestFlags flags);
int nbd_client_co_preadv(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov, int flags);
diff --git a/block/nbd-client.c b/block/nbd-client.c
index 7e9c3ec..104ba2f 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -275,6 +275,41 @@ int nbd_client_co_pwritev(BlockDriverState *bs, uint64_t
offset,
return -reply.error;
}
+int nbd_client_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset,
+ int count, BdrvRequestFlags flags)
+{
+ ssize_t ret;
+ NbdClientSession *client = nbd_get_client_session(bs);
+ struct nbd_request request = {
+ .type = NBD_CMD_WRITE_ZEROES,
+ .from = offset,
+ .len = count,
+ };
+ struct nbd_reply reply;
+
+ if (!(client->nbdflags & NBD_FLAG_SEND_WRITE_ZEROES)) {
+ return -ENOTSUP;
+ }
+
+ if (flags & BDRV_REQ_FUA) {
+ assert(client->nbdflags & NBD_FLAG_SEND_FUA);
+ request.flags |= NBD_CMD_FLAG_FUA;
+ }
+ if (!(flags & BDRV_REQ_MAY_UNMAP)) {
+ request.flags |= NBD_CMD_FLAG_NO_HOLE;
+ }
+
+ nbd_coroutine_start(client, &request);
+ ret = nbd_co_send_request(bs, &request, NULL);
+ if (ret < 0) {
+ reply.error = -ret;
+ } else {
+ nbd_co_receive_reply(client, &request, &reply, NULL);
+ }
+ nbd_coroutine_end(client, &request);
+ return -reply.error;
+}
+
int nbd_client_co_flush(BlockDriverState *bs)
{
NbdClientSession *client = nbd_get_client_session(bs);
diff --git a/block/nbd.c b/block/nbd.c
index 8d57220..049d1bd 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -357,6 +357,7 @@ 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;
}
@@ -440,6 +441,7 @@ 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,
@@ -458,6 +460,7 @@ 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,
@@ -476,6 +479,7 @@ 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,
--
2.5.5
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), (continued)
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/21
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Pádraig Brady, 2016/07/21
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Paolo Bonzini, 2016/07/21
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Dave Chinner, 2016/07/22
- Re: [Qemu-block] semantics of FIEMAP without FIEMAP_FLAG_SYNC (was Re: [Qemu-devel] [PATCH v5 13/14] nbd: Implement NBD_CMD_WRITE_ZEROES on server), Paolo Bonzini, 2016/07/22
[Qemu-block] [PATCH v5 10/14] nbd: Less allocation during NBD_OPT_LIST, Eric Blake, 2016/07/19
[Qemu-block] [PATCH v5 12/14] nbd: Improve server handling of shutdown requests, Eric Blake, 2016/07/19
[Qemu-block] [PATCH v5 07/14] nbd: Share common option-sending code in client, Eric Blake, 2016/07/19
[Qemu-block] [PATCH v5 11/14] nbd: Support shorter handshake, Eric Blake, 2016/07/19
[Qemu-block] [PATCH v5 14/14] nbd: Implement NBD_CMD_WRITE_ZEROES on client,
Eric Blake <=
Re: [Qemu-block] [Qemu-devel] [PATCH for-2.7 v5 00/14] nbd: efficient write zeroes, Fam Zheng, 2016/07/19
Re: [Qemu-block] [PATCH for-2.7 v5 00/14] nbd: efficient write zeroes, Paolo Bonzini, 2016/07/19