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[Qemu-devel] [PULL 38/48] nbd: Support BDRV_REQ_FUA
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 38/48] nbd: Support BDRV_REQ_FUA |
Date: |
Tue, 29 Mar 2016 17:08:38 +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>
Reviewed-by: Max Reitz <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] [PULL 24/48] replay: introduce block devices record/replay, (continued)
- [Qemu-devel] [PULL 24/48] replay: introduce block devices record/replay, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 30/48] xen_disk: Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 33/48] block: Handle flush error in bdrv_pwrite_sync(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 31/48] block: blockdev_init(): Call blk_set_enable_write_cache() explicitly, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 34/48] block: Move enable_write_cache to BB level, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 37/48] iscsi: Support BDRV_REQ_FUA, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 32/48] block: Always set writeback mode in blk_new_open(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 39/48] raw: Support BDRV_REQ_FUA, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 36/48] block: Introduce bdrv_co_writev_flags(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 35/48] block/qapi: Use blk_enable_write_cache(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 38/48] nbd: Support BDRV_REQ_FUA,
Kevin Wolf <=
- [Qemu-devel] [PULL 41/48] qemu-io: Use bdrv_parse_cache_mode() in reopen_f(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 44/48] block: Remove bdrv_(set_)enable_write_cache(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 40/48] block: Use bdrv_parse_cache_mode() in drive_init(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 20/48] block: an interoperability test for luks vs dm-crypt/cryptsetup, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 42/48] block: Remove bdrv_parse_cache_flags(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 46/48] block/null-{co, aio}: Allow reading zeroes, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 43/48] block: Remove BDRV_O_CACHE_WB, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 47/48] block/null-{co, aio}: Implement get_block_status(), Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 45/48] qemu-img: Fix preallocation with -S 0 for convert, Kevin Wolf, 2016/03/29
- [Qemu-devel] [PULL 48/48] iotests: Test qemu-img convert -S 0 behavior, Kevin Wolf, 2016/03/29