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a89ef0c357
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Eric Blake a89ef0c357 nbd: don't request FUA on FLUSH 
The NBD protocol does not clearly document what will happen
if a client sends NBD_CMD_FLAG_FUA on NBD_CMD_FLUSH.
Historically, both the qemu and upstream NBD servers silently
ignored that flag, but that feels a bit risky.  Meanwhile, the
qemu NBD client unconditionally sends the flag (without even
bothering to check whether the caller cares; at least with
NBD_CMD_WRITE the client only sends FUA if requested by a
higher layer).

There is ongoing discussion on the NBD list to fix the
protocol documentation to require that the server MUST ignore
the flag (unless the kernel folks can better explain what FUA
means for a flush), but until those doc improvements land, the
current nbd.git master was recently changed to reject the flag
with EINVAL (see nbd commit ab22e082), which now makes it
impossible for a qemu client to use FLUSH with an upstream NBD
server.

We should not send FUA with flush unless the upstream protocol
documents what it will do, and even then, it should be something
that the caller can opt into, rather than being unconditional.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1459526902-32561-1-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-04-05 11:46:52 +02:00
..
accounting.c block: Clean up includes 2016-01-20 13:36:23 +01:00
archipelago.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
backup.c block: Remove bdrv_(set_)enable_write_cache() 2016-03-30 12:16:03 +02:00
blkdebug.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
blkreplay.c replay: introduce block devices record/replay 2016-03-30 12:15:57 +02:00
blkverify.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
block-backend.c block: Remove BDRV_O_CACHE_WB 2016-03-30 12:16:03 +02:00
bochs.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
cloop.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
commit.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
crypto.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
curl.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
dirty-bitmap.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
dmg.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
gluster.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
io.c block: Introduce bdrv_co_writev_flags() 2016-03-30 12:16:02 +02:00
iscsi.c iscsi: Support BDRV_REQ_FUA 2016-03-30 12:16:02 +02:00
linux-aio.c block: Clean up includes 2016-01-20 13:36:23 +01:00
Makefile.objs replay: introduce block devices record/replay 2016-03-30 12:15:57 +02:00
mirror.c block: Remove bdrv_(set_)enable_write_cache() 2016-03-30 12:16:03 +02:00
nbd-client.c nbd: don't request FUA on FLUSH 2016-04-05 11:46:52 +02:00
nbd-client.h nbd: Support BDRV_REQ_FUA 2016-03-30 12:16:02 +02:00
nbd.c nbd: Support BDRV_REQ_FUA 2016-03-30 12:16:02 +02:00
nfs.c block/nfs: add missing #include "qemu/cutils.h" 2016-03-30 16:50:39 -04:00
null.c block/null-{co,aio}: Implement get_block_status() 2016-03-30 12:16:04 +02:00
parallels.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
qapi.c block/qapi: Use blk_enable_write_cache() 2016-03-30 12:16:02 +02:00
qcow2-cache.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qcow2-cluster.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
qcow2-refcount.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
qcow2-snapshot.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
qcow2.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
qcow2.h qcow2: Add function for refcount order amendment 2015-12-18 14:34:43 +01:00
qcow.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
qed-check.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qed-cluster.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qed-gencb.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qed-l2-cache.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qed-table.c block: Clean up includes 2016-01-20 13:36:23 +01:00
qed.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
qed.h util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
quorum.c quorum: Emit QUORUM_REPORT_BAD for reads in fifo mode 2016-03-17 16:43:30 +01:00
raw_bsd.c raw: Support BDRV_REQ_FUA 2016-03-30 12:16:02 +02:00
raw-aio.h include/qemu/iov.h: Don't include qemu-common.h 2016-03-22 22:20:16 +01:00
raw-posix.c block/raw-posix.c: Make physical devices usable in QEMU under Mac OS X host 2016-03-30 11:59:32 +02:00
raw-win32.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
rbd.c util: move declarations out of qemu-common.h 2016-03-22 22:20:17 +01:00
sheepdog.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
snapshot.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
ssh.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
stream.c -----BEGIN PGP SIGNATURE----- 2016-03-29 19:54:49 +01:00
throttle-groups.c block: Clean up includes 2016-01-20 13:36:23 +01:00
vdi.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
vhdx-endian.c block: Clean up includes 2016-01-20 13:36:23 +01:00
vhdx-log.c include/qemu/osdep.h: Don't include qapi/error.h 2016-03-22 22:20:15 +01:00
vhdx.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
vhdx.h block: vhdx - update PAYLOAD_BLOCK_UNMAPPED value to match 1.00 spec 2014-12-12 15:42:22 +00:00
vmdk.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
vpc.c block: Always set writeback mode in blk_new_open() 2016-03-30 12:16:01 +02:00
vvfat.c block: Remove BDRV_O_CACHE_WB 2016-03-30 12:16:03 +02:00
win32-aio.c block: Clean up includes 2016-01-20 13:36:23 +01:00
write-threshold.c block: Clean up includes 2016-01-20 13:36:23 +01:00