block: Fix parameter checking in bdrv_co_copy_range_internal

src may be NULL if BDRV_REQ_ZERO_WRITE flag is set, in this case only
check dst and dst->bs. This bug was introduced when moving in the
r

block: Fix parameter checking in bdrv_co_copy_range_internal

src may be NULL if BDRV_REQ_ZERO_WRITE flag is set, in this case only
check dst and dst->bs. This bug was introduced when moving in the
request tracking code from bdrv_co_copy_range, in 37aec7d75eb.

This especially fixes the possible segfault when initializing src_bs
with a NULL src.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 20180703023758.14422-2-famz@redhat.com
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Make truncate operations asynchronous (so that preallocation in
blockdev-create doesn't block th

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Make truncate operations asynchronous (so that preallocation in
blockdev-create doesn't block the main loop any more)
- usb-storage: Add rerror/werror properties
- nvme: Add num_queues property
- qemu-img convert: Copy offloading fixes (including data corruption fix)
- qcow2: Fix cluster leak on temporary write error
- Use byte-based functions instead of bdrv_co_readv/writev()
- Various small fixes and cleanups

# gpg: Signature made Fri 29 Jun 2018 15:08:34 BST
# gpg: using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74 56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (29 commits)
block: Remove unused sector-based vectored I/O
vhdx: Switch to byte-based calls
replication: Switch to byte-based calls
qcow: Switch to a byte-based driver
qcow: Switch qcow_co_writev to byte-based calls
qcow: Switch qcow_co_readv to byte-based calls
qcow: Switch get_cluster_offset to be byte-based
parallels: Switch to byte-based calls
file-posix: Fix EINTR handling
iscsi: Don't blindly use designator length in response for memcpy
qcow2: Fix src_offset in copy offloading
file-posix: Implement co versions of discard/flush
qemu-iotests: Test qcow2 not leaking clusters on write error
qcow2: Free allocated clusters on write error
qemu-iotests: Update 026.out.nocache reference output
block/crypto: Simplify block_crypto_{open,create}_opts_init()
block: Move request tracking to children in copy offloading
qcow2: Remove dead check on !ret
file-posix: Make .bdrv_co_truncate asynchronous
block: Use tracked request for truncate
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block: Remove unused sector-based vectored I/O

We are gradually moving away from sector-based interfaces, towards
byte-based. Now that all callers of vectored I/O have been converted
to use our pre

block: Remove unused sector-based vectored I/O

We are gradually moving away from sector-based interfaces, towards
byte-based. Now that all callers of vectored I/O have been converted
to use our preferred byte-based bdrv_co_p{read,write}v(), we can
delete the unused bdrv_co_{read,write}v().

Furthermore, this gets rid of the signature difference between the
public bdrv_co_writev() and the callback .bdrv_co_writev (the
latter still exists, because some drivers still need more work
before they are fully byte-based).

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Move request tracking to children in copy offloading

in_flight and tracked requests need to be tracked in every layer during
recursion. For now the only user is qemu-img convert where overlap

block: Move request tracking to children in copy offloading

in_flight and tracked requests need to be tracked in every layer during
recursion. For now the only user is qemu-img convert where overlapping
requests and IOThreads don't exist, therefore this change doesn't make
much difference form user point of view, but it is incorrect as part of
the API. Fix it.

Reported-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Use tracked request for truncate

When growing an image, block drivers (especially protocol drivers) may
initialise the newly added area. I/O requests to the same area need to
wait for this in

block: Use tracked request for truncate

When growing an image, block drivers (especially protocol drivers) may
initialise the newly added area. I/O requests to the same area need to
wait for this initialisation to be completed so that data writes don't
get overwritten and reads don't read uninitialised data.

To avoid overhead in the fast I/O path by adding new locking in the
protocol drivers and to restrict the impact to requests that actually
touch the new area, reuse the existing tracked request infrastructure in
block/io.c and mark all discard requests as serialising.

With this change, it is safe for protocol drivers to make
.bdrv_co_truncate actually asynchronous.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

block: Move bdrv_truncate() implementation to io.c

This moves the bdrv_truncate() implementation from block.c to block/io.c
so it can have access to the tracked requests infrastructure.

This involv

block: Move bdrv_truncate() implementation to io.c

This moves the bdrv_truncate() implementation from block.c to block/io.c
so it can have access to the tracked requests infrastructure.

This involves making refresh_total_sectors() public (in block_int.h).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Active mirror (blockdev-mirror copy-mode=write-blocking)
- bdrv_drain_*() fixes and test cases
- F

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Active mirror (blockdev-mirror copy-mode=write-blocking)
- bdrv_drain_*() fixes and test cases
- Fix crash with scsi-hd and drive_del

# gpg: Signature made Mon 18 Jun 2018 17:44:10 BST
# gpg: using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74 56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (35 commits)
iotests: Add test for active mirroring
block/mirror: Add copy mode QAPI interface
block/mirror: Add active mirroring
job: Add job_progress_increase_remaining()
block/mirror: Add MirrorBDSOpaque
block/dirty-bitmap: Add bdrv_dirty_iter_next_area
test-hbitmap: Add non-advancing iter_next tests
hbitmap: Add @advance param to hbitmap_iter_next()
block: Generalize should_update_child() rule
block/mirror: Use source as a BdrvChild
block/mirror: Wait for in-flight op conflicts
block/mirror: Use CoQueue to wait on in-flight ops
block/mirror: Convert to coroutines
block/mirror: Pull out mirror_perform()
block: fix QEMU crash with scsi-hd and drive_del
test-bdrv-drain: Test graph changes in drain_all section
block: Allow graph changes in bdrv_drain_all_begin/end sections
block: ignore_bds_parents parameter for drain functions
block: Move bdrv_drain_all_begin() out of coroutine context
block: Allow AIO_WAIT_WHILE with NULL ctx
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block: Allow graph changes in bdrv_drain_all_begin/end sections

bdrv_drain_all_*() used bdrv_next() to iterate over all root nodes and
did a subtree drain for each of them. This works fine as long a

block: Allow graph changes in bdrv_drain_all_begin/end sections

bdrv_drain_all_*() used bdrv_next() to iterate over all root nodes and
did a subtree drain for each of them. This works fine as long as the
graph is static, but sadly, reality looks different.

If the graph changes so that root nodes are added or removed, we would
have to compensate for this. bdrv_next() returns each root node only
once even if it's the root node for multiple BlockBackends or for a
monitor-owned block driver tree, which would only complicate things.

The much easier and more obviously correct way is to fundamentally
change the way the functions work: Iterate over all BlockDriverStates,
no matter who owns them, and drain them individually. Compensation is
only necessary when a new BDS is created inside a drain_all section.
Removal of a BDS doesn't require any action because it's gone afterwards
anyway.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: ignore_bds_parents parameter for drain functions

In the future, bdrv_drained_all_begin/end() will drain all invidiual
nodes separately rather than whole subtrees. This means that we don't
wan

block: ignore_bds_parents parameter for drain functions

In the future, bdrv_drained_all_begin/end() will drain all invidiual
nodes separately rather than whole subtrees. This means that we don't
want to propagate the drain to all parents any more: If the parent is a
BDS, it will already be drained separately. Recursing to all parents is
unnecessary work and would make it an O(n²) operation.

Prepare the drain function for the changed drain_all by adding an
ignore_bds_parents parameter to the internal implementation that
prevents the propagation of the drain to BDS parents. We still (have to)
propagate it to non-BDS parents like BlockBackends or Jobs because those
are not drained separately.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Move bdrv_drain_all_begin() out of coroutine context

Before we can introduce a single polling loop for all nodes in
bdrv_drain_all_begin(), we must make sure to run it outside of coroutine
co

block: Move bdrv_drain_all_begin() out of coroutine context

Before we can introduce a single polling loop for all nodes in
bdrv_drain_all_begin(), we must make sure to run it outside of coroutine
context like we already do for bdrv_do_drained_begin().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Defer .bdrv_drain_begin callback to polling phase

We cannot allow aio_poll() in bdrv_drain_invoke(begin=true) until we're
done with propagating the drain through the graph and are doing the
s

block: Defer .bdrv_drain_begin callback to polling phase

We cannot allow aio_poll() in bdrv_drain_invoke(begin=true) until we're
done with propagating the drain through the graph and are doing the
single final BDRV_POLL_WHILE().

Just schedule the coroutine with the callback and increase bs->in_flight
to make sure that the polling phase will wait for it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Don't poll in parent drain callbacks

bdrv_do_drained_begin() is only safe if we have a single
BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow
that parent callbacks intro

block: Don't poll in parent drain callbacks

bdrv_do_drained_begin() is only safe if we have a single
BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow
that parent callbacks introduce a nested polling loop that could cause
graph changes while we're traversing the graph.

Split off bdrv_do_drained_begin_quiesce(), which only quiesces a single
node without waiting for its requests to complete. These requests will
be waited for in the BDRV_POLL_WHILE() call down the call chain.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Drain recursively with a single BDRV_POLL_WHILE()

Anything can happen inside BDRV_POLL_WHILE(), including graph
changes that may interfere with its callers (e.g. child list iteration
in recur

block: Drain recursively with a single BDRV_POLL_WHILE()

Anything can happen inside BDRV_POLL_WHILE(), including graph
changes that may interfere with its callers (e.g. child list iteration
in recursive callers of bdrv_do_drained_begin).

Switch to a single BDRV_POLL_WHILE() call for the whole subtree at the
end of bdrv_do_drained_begin() to avoid such effects. The recursion
happens now inside the loop condition. As the graph can only change
between bdrv_drain_poll() calls, but not inside of it, doing the
recursion here is safe.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Remove bdrv_drain_recurse()

For bdrv_drain(), recursively waiting for child node requests is
pointless because we didn't quiesce their parents, so new requests could
come in anyway. Letting t

block: Remove bdrv_drain_recurse()

For bdrv_drain(), recursively waiting for child node requests is
pointless because we didn't quiesce their parents, so new requests could
come in anyway. Letting the function work only on a single node makes it
more consistent.

For subtree drains and drain_all, we already have the recursion in
bdrv_do_drained_begin(), so the extra recursion doesn't add anything
either.

Remove the useless code.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

block: Really pause block jobs on drain

We already requested that block jobs be paused in .bdrv_drained_begin,
but no guarantee was made that the job was actually inactive at the
point where bdrv_dr

block: Really pause block jobs on drain

We already requested that block jobs be paused in .bdrv_drained_begin,
but no guarantee was made that the job was actually inactive at the
point where bdrv_drained_begin() returned.

This introduces a new callback BdrvChildRole.bdrv_drained_poll() and
uses it to make bdrv_drain_poll() consider block jobs using the node to
be drained.

For the test case to work as expected, we have to switch from
block_job_sleep_ns() to qemu_co_sleep_ns() so that the test job is even
considered active and must be waited for when draining the node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Avoid unnecessary aio_poll() in AIO_WAIT_WHILE()

Commit 91af091f923 added an additional aio_poll() to BDRV_POLL_WHILE()
in order to make sure that all pending BHs are executed on drain. This

block: Avoid unnecessary aio_poll() in AIO_WAIT_WHILE()

Commit 91af091f923 added an additional aio_poll() to BDRV_POLL_WHILE()
in order to make sure that all pending BHs are executed on drain. This
was the wrong place to make the fix, as it is useless overhead for all
other users of the macro and unnecessarily complicates the mechanism.

This patch effectively reverts said commit (the context has changed a
bit and the code has moved to AIO_WAIT_WHILE()) and instead polls in the
loop condition for drain.

The effect is probably hard to measure in any real-world use case
because actual I/O will dominate, but if I run only the initialisation
part of 'qemu-img convert' where it calls bdrv_block_status() for the
whole image to find out how much data there is copy, this phase actually
needs only roughly half the time after this patch.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

block: Don't manually poll in bdrv_drain_all()

All involved nodes are already idle, we called bdrv_do_drain_begin() on
them.

The comment in the code suggested that this was not correct because the

block: Don't manually poll in bdrv_drain_all()

All involved nodes are already idle, we called bdrv_do_drain_begin() on
them.

The comment in the code suggested that this was not correct because the
completion of a request on one node could spawn a new request on a
different node (which might have been drained before, so we wouldn't
drain the new request). In reality, new requests to different nodes
aren't spawned out of nothing, but only in the context of a parent
request, and they aren't submitted to random nodes, but only to child
nodes. As long as we still poll for the completion of the parent request
(which we do), draining each root node separately is good enough.

Remove the additional polling code from bdrv_drain_all_begin() and
replace it with an assertion that all nodes are already idle after we
drained them separately.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

block: Remove 'recursive' parameter from bdrv_drain_invoke()

All callers pass false for the 'recursive' parameter now. Remove it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Ha

block: Remove 'recursive' parameter from bdrv_drain_invoke()

All callers pass false for the 'recursive' parameter now. Remove it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

block: Use bdrv_do_drain_begin/end in bdrv_drain_all()

bdrv_do_drain_begin/end() implement already everything that
bdrv_drain_all_begin/end() need and currently still do manually: Disable
external e

block: Use bdrv_do_drain_begin/end in bdrv_drain_all()

bdrv_do_drain_begin/end() implement already everything that
bdrv_drain_all_begin/end() need and currently still do manually: Disable
external events, call parent drain callbacks, call block driver
callbacks.

It also does two more things:

The first is incrementing bs->quiesce_counter. bdrv_drain_all() already
stood out in the test case by behaving different from the other drain
variants. Adding this is not only safe, but in fact a bug fix.

The second is calling bdrv_drain_recurse(). We already do that later in
the same function in a loop, so basically doing an early first iteration
doesn't hurt.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

test-bdrv-drain: bdrv_drain() works with cross-AioContext events

As long as nobody keeps the other I/O thread from working, there is no
reason why bdrv_drain() wouldn't work with cross-AioContext ev

test-bdrv-drain: bdrv_drain() works with cross-AioContext events

As long as nobody keeps the other I/O thread from working, there is no
reason why bdrv_drain() wouldn't work with cross-AioContext events. The
key is that the root request we're waiting for is in the AioContext
we're polling (which it always is for bdrv_drain()) so that aio_poll()
is woken up in the end.

Add a test case that shows that it works. Remove the comment in
bdrv_drain() that claims otherwise.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

* Copy offloading for qemu-img convert (iSCSI, raw, and qcow2)

If the underlying storage suppo

Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

* Copy offloading for qemu-img convert (iSCSI, raw, and qcow2)

If the underlying storage supports copy offloading, qemu-img convert will
use it instead of performing reads and writes. This avoids data transfers
and thus frees up storage bandwidth for other purposes. SCSI EXTENDED COPY
and Linux copy_file_range(2) are used to implement this optimization.

* Drop spurious "WARNING: I\/O thread spun for 1000 iterations" warning

# gpg: Signature made Mon 04 Jun 2018 12:20:08 BST
# gpg: using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>"
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35 775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
main-loop: drop spin_counter
qemu-img: Convert with copy offloading
block-backend: Add blk_co_copy_range
iscsi: Implement copy offloading
iscsi: Create and use iscsi_co_wait_for_task
iscsi: Query and save device designator when opening
file-posix: Implement bdrv_co_copy_range
qcow2: Implement copy offloading
raw: Implement copy offloading
raw: Check byte range uniformly
block: Introduce API for copy offloading

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block: Introduce API for copy offloading

Introduce the bdrv_co_copy_range() API for copy offloading. Block
drivers implementing this API support efficient copy operations that
avoid reading each bl

block: Introduce API for copy offloading

Introduce the bdrv_co_copy_range() API for copy offloading. Block
drivers implementing this API support efficient copy operations that
avoid reading each block from the source device and writing it to the
destination devices. Examples of copy offload primitives are SCSI
EXTENDED COPY and Linux copy_file_range(2).

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20180601092648.24614-2-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Switch AIO/callback based block drivers to a byte-based interface
- Block jobs: Expose error strin

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- Switch AIO/callback based block drivers to a byte-based interface
- Block jobs: Expose error string via query-block-jobs
- Block job cleanups and fixes
- hmp: Allow using a qdev id in block_set_io_throttle

# gpg: Signature made Tue 15 May 2018 16:33:10 BST
# gpg: using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74 56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (37 commits)
iotests: Add test for -U/force-share conflicts
qemu-img: Use only string options in img_open_opts
qemu-io: Use purely string blockdev options
block: Document BDRV_REQ_WRITE_UNCHANGED support
qemu-img: Check post-truncation size
iotests: Add test for COR across nodes
iotests: Copy 197 for COR filter driver
iotests: Clean up wrap image in 197
block: Support BDRV_REQ_WRITE_UNCHANGED in filters
block/quorum: Support BDRV_REQ_WRITE_UNCHANGED
block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes
block: Add BDRV_REQ_WRITE_UNCHANGED flag
block: BLK_PERM_WRITE includes ..._UNCHANGED
block: Add COR filter driver
iotests: Skip 181 and 201 without userfaultfd
iotests: Add failure matching to common.qemu
docs: Document the new default sizes of the qcow2 caches
qcow2: Give the refcount cache the minimum possible size by default
specs/qcow2: Clarify that compressed clusters have the COPIED bit reset
Fix error message about compressed clusters with OFLAG_COPIED
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

Merge remote-tracking branch 'mreitz/tags/pull-block-2018-05-15' into queue-block

- Copy-on-read block driver
- The qcow2 default refcount cache size has been decreased
- Various bug fixes

# gpg: S

Merge remote-tracking branch 'mreitz/tags/pull-block-2018-05-15' into queue-block

- Copy-on-read block driver
- The qcow2 default refcount cache size has been decreased
- Various bug fixes

# gpg: Signature made Tue May 15 16:18:25 2018 CEST
# gpg: using RSA key F407DB0061D5CF40
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>"
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1 1829 F407 DB00 61D5 CF40

* mreitz/tags/pull-block-2018-05-15: (21 commits)
iotests: Add test for -U/force-share conflicts
qemu-img: Use only string options in img_open_opts
qemu-io: Use purely string blockdev options
block: Document BDRV_REQ_WRITE_UNCHANGED support
qemu-img: Check post-truncation size
iotests: Add test for COR across nodes
iotests: Copy 197 for COR filter driver
iotests: Clean up wrap image in 197
block: Support BDRV_REQ_WRITE_UNCHANGED in filters
block/quorum: Support BDRV_REQ_WRITE_UNCHANGED
block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes
block: Add BDRV_REQ_WRITE_UNCHANGED flag
block: BLK_PERM_WRITE includes ..._UNCHANGED
block: Add COR filter driver
iotests: Skip 181 and 201 without userfaultfd
iotests: Add failure matching to common.qemu
docs: Document the new default sizes of the qcow2 caches
qcow2: Give the refcount cache the minimum possible size by default
specs/qcow2: Clarify that compressed clusters have the COPIED bit reset
Fix error message about compressed clusters with OFLAG_COPIED
...

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Mess

block: Set BDRV_REQ_WRITE_UNCHANGED for COR writes

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20180421132929.21610-5-mreitz@redhat.com
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

show more ...