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[Qemu-devel] [PATCH v2 14/20] nbd: Support BDRV_REQ_FUA
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH v2 14/20] nbd: Support BDRV_REQ_FUA |
Date: |
Tue, 29 Mar 2016 15:30:51 +0200 |
The NBD server already used to send a FUA flag when the writethrough
mode was set. This code was a remnant from the times where protocol
drivers actually had to implement writethrough modes. Since nowadays the
block layer sends flushes in writethrough mode and non-root nodes are
always writeback, this was mostly dead code - only mostly because if NBD
was configured to be used without a format, we sent _both_ FUA and an
explicit flush afterwards, which makes the code not technically dead,
but useless overhead.
This patch changes the code so that the block layer's FUA flag is
recognised and translated into a NBD FUA flag. The additional flush is
avoided now.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/nbd-client.c | 13 +++++++------
block/nbd-client.h | 2 +-
block/nbd.c | 27 ++++++++++++++++++++++++++-
3 files changed, 34 insertions(+), 8 deletions(-)
diff --git a/block/nbd-client.c b/block/nbd-client.c
index 6a9b4c7..021a88b 100644
--- a/block/nbd-client.c
+++ b/block/nbd-client.c
@@ -243,15 +243,15 @@ static int nbd_co_readv_1(BlockDriverState *bs, int64_t
sector_num,
static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov,
- int offset)
+ int offset, int *flags)
{
NbdClientSession *client = nbd_get_client_session(bs);
struct nbd_request request = { .type = NBD_CMD_WRITE };
struct nbd_reply reply;
ssize_t ret;
- if (!bdrv_enable_write_cache(bs) &&
- (client->nbdflags & NBD_FLAG_SEND_FUA)) {
+ if ((*flags & BDRV_REQ_FUA) && (client->nbdflags & NBD_FLAG_SEND_FUA)) {
+ *flags &= ~BDRV_REQ_FUA;
request.type |= NBD_CMD_FLAG_FUA;
}
@@ -291,12 +291,13 @@ int nbd_client_co_readv(BlockDriverState *bs, int64_t
sector_num,
}
int nbd_client_co_writev(BlockDriverState *bs, int64_t sector_num,
- int nb_sectors, QEMUIOVector *qiov)
+ int nb_sectors, QEMUIOVector *qiov, int *flags)
{
int offset = 0;
int ret;
while (nb_sectors > NBD_MAX_SECTORS) {
- ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
+ ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset,
+ flags);
if (ret < 0) {
return ret;
}
@@ -304,7 +305,7 @@ int nbd_client_co_writev(BlockDriverState *bs, int64_t
sector_num,
sector_num += NBD_MAX_SECTORS;
nb_sectors -= NBD_MAX_SECTORS;
}
- return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
+ return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset, flags);
}
int nbd_client_co_flush(BlockDriverState *bs)
diff --git a/block/nbd-client.h b/block/nbd-client.h
index 53f116d..bc7aec0 100644
--- a/block/nbd-client.h
+++ b/block/nbd-client.h
@@ -48,7 +48,7 @@ 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_writev(BlockDriverState *bs, int64_t sector_num,
- int nb_sectors, QEMUIOVector *qiov);
+ int nb_sectors, QEMUIOVector *qiov, int *flags);
int nbd_client_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov);
diff --git a/block/nbd.c b/block/nbd.c
index 836424c..7b1eb5f 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -354,10 +354,29 @@ 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_writev_flags(BlockDriverState *bs, int64_t sector_num,
+ int nb_sectors, QEMUIOVector *qiov, int flags)
+{
+ int ret;
+
+ ret = nbd_client_co_writev(bs, sector_num, nb_sectors, qiov, &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(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
- return nbd_client_co_writev(bs, sector_num, nb_sectors, qiov);
+ return nbd_co_writev_flags(bs, sector_num, nb_sectors, qiov, 0);
}
static int nbd_co_flush(BlockDriverState *bs)
@@ -457,6 +476,8 @@ static BlockDriver bdrv_nbd = {
.bdrv_file_open = nbd_open,
.bdrv_co_readv = nbd_co_readv,
.bdrv_co_writev = nbd_co_writev,
+ .bdrv_co_writev_flags = nbd_co_writev_flags,
+ .supported_write_flags = BDRV_REQ_FUA,
.bdrv_close = nbd_close,
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_discard = nbd_co_discard,
@@ -475,6 +496,8 @@ static BlockDriver bdrv_nbd_tcp = {
.bdrv_file_open = nbd_open,
.bdrv_co_readv = nbd_co_readv,
.bdrv_co_writev = nbd_co_writev,
+ .bdrv_co_writev_flags = nbd_co_writev_flags,
+ .supported_write_flags = BDRV_REQ_FUA,
.bdrv_close = nbd_close,
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_discard = nbd_co_discard,
@@ -493,6 +516,8 @@ static BlockDriver bdrv_nbd_unix = {
.bdrv_file_open = nbd_open,
.bdrv_co_readv = nbd_co_readv,
.bdrv_co_writev = nbd_co_writev,
+ .bdrv_co_writev_flags = nbd_co_writev_flags,
+ .supported_write_flags = BDRV_REQ_FUA,
.bdrv_close = nbd_close,
.bdrv_co_flush_to_os = nbd_co_flush,
.bdrv_co_discard = nbd_co_discard,
--
1.8.3.1
- [Qemu-devel] [PATCH v2 00/20] block: Implement writethrough in BlockBackend, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 01/20] block: Add bdrv_parse_cache_mode(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 04/20] qemu-img: Expand all BDRV_O_FLAGS uses, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 02/20] qemu-nbd: Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 03/20] qemu-io: Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 07/20] block: blockdev_init(): Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 05/20] qemu-img: Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 06/20] xen_disk: Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 14/20] nbd: Support BDRV_REQ_FUA,
Kevin Wolf <=
- [Qemu-devel] [PATCH v2 11/20] block/qapi: Use blk_enable_write_cache(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 16/20] block: Use bdrv_parse_cache_mode() in drive_init(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 10/20] block: Move enable_write_cache to BB level, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 09/20] block: Handle flush error in bdrv_pwrite_sync(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 08/20] block: Always set writeback mode in blk_new_open(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 12/20] block: Introduce bdrv_co_writev_flags(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 15/20] raw: Support BDRV_REQ_FUA, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PATCH v2 17/20] qemu-io: Use bdrv_parse_cache_mode() in reopen_f(), Kevin Wolf, 2016/03/29