bdrv_co_invalidate_cache() clears the BDRV_O_INACTIVE flag before
actually activating a node so that the correct permissions etc. are
taken. In case of errors, the flag must be restored so that the next
call to bdrv_co_invalidate_cache() retries activation.
Restoring the flag was missing in the error path for a failed
parent->role->activate() call. The consequence is that this attempt to
activate all images correctly fails because we still set errp, however
on the next attempt BDRV_O_INACTIVE is already clear, so we return
success without actually retrying the failed action.
An example where this is observable in practice is migration to a QEMU
instance that has a raw format block node attached to a guest device
with share-rw=off (the default) while another process holds
BLK_PERM_WRITE for the same image. In this case, all activation steps
before parent->role->activate() succeed because raw can tolerate other
writers to the image. Only the parent callback (in particular
blk_root_activate()) tries to implement the share-rw=on property and
requests exclusive write permissions. This fails when the migration
completes and correctly displays an error. However, a manual 'cont' will
incorrectly resume the VM without calling blk_root_activate() again.
This case is described in more detail in the following bug report:
https://bugzilla.redhat.com/show_bug.cgi?id=1531888
Fix this by correctly restoring the BDRV_O_INACTIVE flag in the error
path.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
If QEMU was configured with a driver in --block-drv-ro-whitelist, trying
to use that driver read-write resulted in an error message even if
auto-read-only=on was set.
Consider auto-read-only=on for the whitelist checking and use it to
automatically degrade to read-only for block drivers on the read-only
whitelist.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
In the block layer, synchronous APIs are often implemented by creating a
coroutine that calls the asynchronous coroutine-based implementation and
then waiting for completion with BDRV_POLL_WHILE().
For this to work with iothreads (more specifically, when the synchronous
API is called in a thread that is not the home thread of the block
device, so that the coroutine will run in a different thread), we must
make sure to call aio_wait_kick() at the end of the operation. Many
places are missing this, so that BDRV_POLL_WHILE() keeps hanging even if
the condition has long become false.
Note that bdrv_dec_in_flight() involves an aio_wait_kick() call. This
corresponds to the BDRV_POLL_WHILE() in the drain functions, but it is
generally not enough for most other operations because they haven't set
the return value in the coroutine entry stub yet. To avoid race
conditions there, we need to kick after setting the return value.
The race window is small enough that the problem doesn't usually surface
in the common path. However, it does surface and causes easily
reproducible hangs if the operation can return early before even calling
bdrv_inc/dec_in_flight, which many of them do (trivial error or no-op
success paths).
The bug in bdrv_truncate(), bdrv_check() and bdrv_invalidate_cache() is
slightly different: These functions even neglected to schedule the
coroutine in the home thread of the node. This avoids the hang, but is
obviously wrong, too. Fix those to schedule the coroutine in the right
AioContext in addition to adding aio_wait_kick() calls.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Add a new command, returning block nodes (and their users) graph.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20181221170909.25584-2-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
Towards the end of bdrv_reopen_queue_child(), before starting to
process the children, the update_flags_from_options() function is
called in order to have BDRVReopenState.flags in sync with the options
from the QDict.
This is necessary because during the reopen process flags must be
updated for all nodes in the queue so bdrv_is_writable_after_reopen()
and the permission checks work correctly.
Because of that, calling update_flags_from_options() again in
bdrv_reopen_prepare() doesn't really change the flags (they are
already up-to-date). But we need to call it in order to remove those
options from QemuOpts and that way indicate that they have been
processed.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This function takes four options (cache.direct, cache.no-flush,
read-only and auto-read-only) from a QemuOpts object and updates the
flags accordingly.
If any of those options is not set (because it was missing from the
original QDict or because it had an invalid value) then the function
aborts with a failed assertion:
$ qemu-io -c 'reopen -o read-only=foo' hd.qcow2
block.c:1126: update_flags_from_options: Assertion `qemu_opt_find(opts, BDRV_OPT_CACHE_DIRECT)' failed.
Aborted
This assertion is unnecessary, and it forces any caller of
bdrv_reopen() to pass all the aforementioned four options. This may
have made sense in order to remove ambiguity when bdrv_reopen() was
taking both flags and options, but that's not the case anymore.
It's also unnecessary if we want to validate the option values,
because bdrv_reopen_prepare() already takes care of that, as we can
see if we remove the assertions:
$ qemu-io -c 'reopen -o read-only=foo' hd.qcow2
Parameter 'read-only' expects 'on' or 'off'
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Now that all callers are passing the new options using the QDict we no
longer need the 'flags' parameter.
This patch makes the following changes:
1) The update_options_from_flags() call is no longer necessary
so it can be removed.
2) The update_flags_from_options() call is now used in all cases,
and is moved down a few lines so it happens after the options
QDict contains the final set of values.
3) The flags parameter is removed. Now the flags are initialized
using the current value (for the top-level node) or the parent
flags (after inherit_options()). In both cases the initial
values are updated to reflect the new options in the QDict. This
happens in bdrv_reopen_queue_child() (as explained above) and in
bdrv_reopen_prepare().
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Now that all callers are passing all flag changes as QDict options,
the flags parameter is no longer necessary, so we can get rid of it.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
No one is using this function anymore, so we can safely remove it.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This patch replaces the bdrv_reopen() calls that set and remove the
BDRV_O_RDWR flag with the new bdrv_reopen_set_read_only() function.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Most callers of bdrv_reopen() only use it to switch a BlockDriverState
between read-only and read-write, so this patch adds a new function
that does just that.
We also want to get rid of the flags parameter in the bdrv_reopen()
API, so this function sets the "read-only" option and passes the
original flags (which will then be updated in bdrv_reopen_prepare()).
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_child_cb_inactivate() asserts that parents are already inactive
when children get inactivated. This precondition is necessary because
parents could still issue requests in their inactivation code.
When block nodes are created individually with -blockdev, all of them
are monitor owned and will be returned by bdrv_next() in an undefined
order (in practice, in the order of their creation, which is usually
children before parents), which obviously fails the assertion:
qemu: block.c:899: bdrv_child_cb_inactivate: Assertion `bs->open_flags & BDRV_O_INACTIVE' failed.
This patch fixes the ordering by skipping nodes with still active
parents in bdrv_inactivate_recurse() because we know that they will be
covered by recursion when the last active parent becomes inactive.
With the correct parents-before-children ordering, we also got rid of
the reason why commit aad0b7a0bf introduced two passes, so we can go
back to a single-pass recursion. This is necessary so we can rely on the
BDRV_O_INACTIVE flag to skip nodes with active parents (the flag used
to be set only in pass 2, so we would always skip non-root nodes in
pass 1 because all parents would still be considered active; setting the
flag in pass 1 would mean, that we never skip anything in pass 2 because
all parents are already considered inactive).
Because of the change to single pass, this patch is best reviewed with
whitespace changes ignored.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
The previous patch fixed the inherits_from pointer after block-stream,
and this one does the same for block-commit.
When block-commit finishes and the 'top' node is not the topmost one
from the backing chain then all nodes above 'base' up to and including
'top' are removed from the chain.
The bdrv_drop_intermediate() call converts a chain like this one:
base <- intermediate <- top <- active
into this one:
base <- active
In a simple scenario each backing file from the first chain has the
inherits_from attribute pointing to its parent. This means that
reopening 'active' will recursively reopen all its children, whose
options can be changed in the process.
However after the 'block-commit' call base.inherits_from is NULL and
the chain is broken, so 'base' does not inherit from 'active' and will
not be reopened automatically:
$ qemu-img create -f qcow2 hd0.qcow2 1M
$ qemu-img create -f qcow2 -b hd0.qcow2 hd1.qcow2
$ qemu-img create -f qcow2 -b hd1.qcow2 hd2.qcow2
$ $QEMU -drive if=none,file=hd2.qcow2
{ 'execute': 'block-commit',
'arguments': {
'device': 'none0',
'top': 'hd1.qcow2' } }
{ 'execute': 'human-monitor-command',
'arguments': {
'command-line':
'qemu-io none0 "reopen -o backing.l2-cache-size=2M"' } }
{ "return": "Cannot change the option 'backing.l2-cache-size'\r\n"}
This patch updates base.inherits_from in this scenario, and adds a
test case.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When a BlockDriverState's child is opened (be it a backing file, the
protocol layer, or any other) inherits_from is set to point to the
parent node. Children opened separately and then attached to a parent
don't have this pointer set.
bdrv_reopen_queue_child() uses this to determine whether a node's
children must also be reopened inheriting the options from the parent
or not. If inherits_from points to the parent then the child is
reopened and its options can be changed, like in this example:
$ qemu-img create -f qcow2 hd0.qcow2 1M
$ qemu-img create -f qcow2 hd1.qcow2 1M
$ $QEMU -drive if=none,node-name=hd0,file=hd0.qcow2,\
backing.driver=qcow2,backing.file.filename=hd1.qcow2
(qemu) qemu-io hd0 "reopen -o backing.l2-cache-size=2M"
If the child does not inherit from the parent then it does not get
reopened and its options cannot be changed:
$ $QEMU -drive if=none,node-name=hd1,file=hd1.qcow2
-drive if=none,node-name=hd0,file=hd0.qcow2,backing=hd1
(qemu) qemu-io hd0 "reopen -o backing.l2-cache-size=2M"
Cannot change the option 'backing.l2-cache-size'
If a disk image has a chain of backing files then all of them are also
connected through their inherits_from pointers (i.e. it's possible to
walk the chain in reverse order from base to top).
However this is broken if the intermediate nodes are removed using
e.g. block-stream because the inherits_from pointer from the base node
becomes NULL:
$ qemu-img create -f qcow2 hd0.qcow2 1M
$ qemu-img create -f qcow2 -b hd0.qcow2 hd1.qcow2
$ qemu-img create -f qcow2 -b hd1.qcow2 hd2.qcow2
$ $QEMU -drive if=none,file=hd2.qcow2
(qemu) qemu-io none0 "reopen -o backing.l2-cache-size=2M"
(qemu) block_stream none0 0 hd0.qcow2
(qemu) qemu-io none0 "reopen -o backing.l2-cache-size=2M"
Cannot change the option 'backing.l2-cache-size'
This patch updates the inherits_from pointer if the intermediate nodes
of a backing chain are removed using bdrv_set_backing_hd(), and adds a
test case for this scenario.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Commit e35bdc123a added the auto-read-only option and the
code to update its corresponding flag in update_flags_from_options(),
but forgot to clear the flag if auto-read-only is false.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_reopen_multiple() does not invoke bdrv_reopen_abort() for the
element of the reopen queue for which bdrv_reopen_prepare() failed,
because it assumes that the prepare function will have rolled back all
changes already.
However, bdrv_reopen_prepare() does not do this in every case: It may
notice an error after BlockDriver.bdrv_reopen_prepare() succeeded, and
it will not invoke BlockDriver.bdrv_reopen_abort() then; and neither
will bdrv_reopen_multiple(), as explained above.
This is wrong because we must always call .bdrv_reopen_commit() or
.bdrv_reopen_abort() after .bdrv_reopen_prepare() has succeeded.
Otherwise, the block driver has no chance to undo what it has done in
its implementation of .bdrv_reopen_prepare().
To fix this, bdrv_reopen_prepare() has to call .bdrv_reopen_abort() if
it wants to return an error after .bdrv_reopen_prepare() has succeeded.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Some block drivers have traditionally changed their node to read-only
mode without asking the user. This behaviour has been marked deprecated
since 2.11, expecting users to provide an explicit read-only=on option.
Now that we have auto-read-only=on, enable these drivers to make use of
the option.
This is the only use of bdrv_set_read_only(), so we can make it a bit
more specific and turn it into a bdrv_apply_auto_read_only() that is
more convenient for drivers to use.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
If a management application builds the block graph node by node, the
protocol layer doesn't inherit its read-only option from the format
layer any more, so it must be set explicitly.
Backing files should work on read-only storage, but at the same time, a
block job like commit should be able to reopen them read-write if they
are on read-write storage. However, without option inheritance, reopen
only changes the read-only option for the root node (typically the
format layer), but not the protocol layer, so reopening fails (the
format layer wants to get write permissions, but the protocol layer is
still read-only).
A simple workaround for the problem in the management tool would be to
open the protocol layer always read-write and to make only the format
layer read-only for backing files. However, sometimes the file is
actually stored on read-only storage and we don't know whether the image
can be opened read-write (for example, for NBD it depends on the server
we're trying to connect to). This adds an option that makes QEMU try to
open the image read-write, but allows it to degrade to a read-only mode
without returning an error.
The documentation for this option is consciously phrased in a way that
allows QEMU to switch to a better model eventually: Instead of trying
when the image is first opened, making the read-only flag dynamic and
changing it automatically whenever the first BLK_PERM_WRITE user is
attached or the last one is detached would be much more useful
behaviour.
Unfortunately, this more useful behaviour is also a lot harder to
implement, and libvirt needs a solution now before it can switch to
-blockdev, so let's start with this easier approach for now.
Instead of adding a new auto-read-only option, turning the existing
read-only into an enum (with a bool alternate for compatibility) was
considered, but it complicated the implementation to the point that it
didn't seem to be worth it.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
To fully change the read-only state of a node, we must not only change
bs->read_only, but also update bs->open_flags.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
This patch aims to bring the following behavior:
1. We don't load bitmaps, when started in inactive mode. It's the case
of incoming migration. In this case we wait for bitmaps migration
through migration channel (if 'dirty-bitmaps' capability is enabled) or
for invalidation (to load bitmaps from the image).
2. We don't remove persistent bitmaps on inactivation. Instead, we only
remove bitmaps after storing. This is the only way to restore bitmaps,
if we decided to resume source after [failed] migration with
'dirty-bitmaps' capability enabled (which means, that bitmaps were not
stored).
3. We load bitmaps on open and any invalidation, it's ok for all cases:
- normal open
- migration target invalidation with dirty-bitmaps capability
(bitmaps are migrating through migration channel, the are not
stored, so they should have IN_USE flag set and will be skipped
when loading. However, it would fail if bitmaps are read-only[1])
- migration target invalidation without dirty-bitmaps capability
(normal load of the bitmaps, if migrated with shared storage)
- source invalidation with dirty-bitmaps capability
(skip because IN_USE)
- source invalidation without dirty-bitmaps capability
(bitmaps were dropped, reload them)
[1]: to accurately handle this, migration of read-only bitmaps is
explicitly forbidden in this patch.
New mechanism for not storing bitmaps when migrate with dirty-bitmaps
capability is introduced: migration filed in BdrvDirtyBitmap.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: John Snow <jsnow@redhat.com>
bdrv_img_create() takes an Error ** argument and uses it in the
conventional way, except for one place: when qemu_opts_do_parse()
fails, it first reports its error to stderr or the HMP monitor with
error_report_err(), then error_setg()'s a generic error.
When the caller reports that second error similarly, this produces two
consecutive error messages on stderr or the HMP monitor.
When the caller does something else with it, such as send it via QMP,
the first error still goes to stderr or the HMP monitor. Fortunately,
no such caller exists.
Simply use the first error as is. Update expected output of
qemu-iotest 049 accordingly.
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181017082702.5581-37-armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
From include/qapi/error.h:
* Pass an existing error to the caller with the message modified:
* error_propagate(errp, err);
* error_prepend(errp, "Could not frobnicate '%s': ", name);
Fei Li pointed out that doing error_propagate() first doesn't work
well when @errp is &error_fatal or &error_abort: the error_prepend()
is never reached.
Since I doubt fixing the documentation will stop people from getting
it wrong, introduce error_propagate_prepend(), in the hope that it
lures people away from using its constituents in the wrong order.
Update the instructions in error.h accordingly.
Convert existing error_prepend() next to error_propagate to
error_propagate_prepend(). If any of these get reached with
&error_fatal or &error_abort, the error messages improve. I didn't
check whether that's the case anywhere.
Cc: Fei Li <fli@suse.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181017082702.5581-2-armbru@redhat.com>
'detect-zeroes' is one of the basic BlockdevOptions available for all
drivers, but it's not handled by bdrv_reopen_prepare(), so any attempt
to change it results in an error:
(qemu) qemu-io virtio0 "reopen -o detect-zeroes=on"
Cannot change the option 'detect-zeroes'
Since there's no reason why we shouldn't allow changing it and the
implementation is simple let's just do it.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
'discard' is one of the basic BlockdevOptions available for all
drivers, but it's not handled by bdrv_reopen_prepare() so any attempt
to change it results in an error:
(qemu) qemu-io virtio0 "reopen -o discard=on"
Cannot change the option 'discard'
Since there's no reason why we shouldn't allow changing it and the
implementation is simple let's just do it.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The bdrv_reopen_prepare() function checks all options passed to each
BlockDriverState (in the reopen_state->options QDict) and makes all
necessary preparations to apply the option changes requested by the
user.
Options are removed from the QDict as they are processed, so at the
end of bdrv_reopen_prepare() only the options that can't be changed
are left. Then a loop goes over all remaining options and verifies
that the old and new values are identical, returning an error if
they're not.
The problem is that at the moment there are options that are removed
from the QDict although they can't be changed. The consequence of this
is any modification to any of those options is silently ignored:
(qemu) qemu-io virtio0 "reopen -o discard=on"
This happens when all options from bdrv_runtime_opts are removed
from the QDict but then only a few of them are processed. Since
it's especially important that "node-name" and "driver" are not
changed, the code puts them back into the QDict so they are checked
at the end of the function. Instead of putting only those two options
back into the QDict, this patch puts all unprocessed options using
qemu_opts_to_qdict().
update_flags_from_options() also needs to be modified to prevent
BDRV_OPT_CACHE_NO_FLUSH, BDRV_OPT_CACHE_DIRECT and BDRV_OPT_READ_ONLY
from going back to the QDict.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
In the previous patches we removed all child references from
bs->{options,explicit_options} because keeping them is useless and
wrong.
Because of this, any attempt to reopen a BlockDriverState using a
child reference as one of its options would result in a failure,
because bdrv_reopen_prepare() would detect that there's a new option
(the child reference) that wasn't present in bs->options.
But passing child references on reopen can be useful. It's a way to
specify a BDS's child without having to pass recursively all of the
child's options, and if the reference points to a different BDS then
this can allow us to replace the child.
However, replacing the child is something that needs to be implemented
case by case and only when it makes sense. For now, this patch allows
passing a child reference as long as it points to the current child of
the BlockDriverState.
It's also important to remember that, as a consequence of the
previous patches, this child reference will be removed from
bs->{options,explicit_options} after the reopening has been completed.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
In the previous patch we removed child references from bs->options, so
there's no need to look for them here anymore.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Block drivers allow opening their children using a reference to an
existing BlockDriverState. These references remain stored in the
'options' and 'explicit_options' QDicts, but we don't need to keep
them once everything is open.
What is more important, these values can become wrong if the children
change:
$ qemu-img create -f qcow2 hd0.qcow2 10M
$ qemu-img create -f qcow2 hd1.qcow2 10M
$ qemu-img create -f qcow2 hd2.qcow2 10M
$ $QEMU -drive if=none,file=hd0.qcow2,node-name=hd0 \
-drive if=none,file=hd1.qcow2,node-name=hd1,backing=hd0 \
-drive file=hd2.qcow2,node-name=hd2,backing=hd1
After this hd2 has hd1 as its backing file. Now let's remove it using
block_stream:
(qemu) block_stream hd2 0 hd0.qcow2
Now hd0 is the backing file of hd2, but hd2's options QDicts still
contain backing=hd1.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When draining a block node, we recurse to its parent and for subtree
drains also to its children. A single AIO_WAIT_WHILE() is then used to
wait for bdrv_drain_poll() to become true, which depends on all of the
nodes we recursed to. However, if the respective child or parent becomes
quiescent and calls bdrv_wakeup(), only the AioWait of the child/parent
is checked, while AIO_WAIT_WHILE() depends on the AioWait of the
original node.
Fix this by using a single AioWait for all callers of AIO_WAIT_WHILE().
This may mean that the draining thread gets a few more unnecessary
wakeups because an unrelated operation got completed, but we already
wake it up when something _could_ have changed rather than only if it
has certainly changed.
Apart from that, drain is a slow path anyway. In theory it would be
possible to use wakeups more selectively and still correctly, but the
gains are likely not worth the additional complexity. In fact, this
patch is a nice simplification for some places in the code.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
When a block device is opened with BDRV_O_SNAPSHOT and the
bdrv_append_temp_snapshot() call fails then the error code path tries
to unref the already destroyed 'options' QDict.
This can be reproduced easily by setting TMPDIR to a location where
the QEMU process can't write:
$ TMPDIR=/nonexistent $QEMU -drive driver=null-co,snapshot=on
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The last case where qobject_from_json() & friends return null without
setting an error is empty or blank input. Callers:
* block.c's parse_json_protocol() reports "Could not parse the JSON
options". It's marked as a work-around, because it also covered
actual bugs, but they got fixed in the previous few commits.
* qobject_input_visitor_new_str() reports "JSON parse error". Also
marked as work-around. The recent fixes have made this unreachable,
because it currently gets called only for input starting with '{'.
* check-qjson.c's empty_input() and blank_input() demonstrate the
behavior.
* The other callers are not affected since they only pass input with
exactly one JSON value or, in the case of negative tests, one error.
Fail with "Expecting a JSON value" instead of returning null, and
simplify callers.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180823164025.12553-48-armbru@redhat.com>
This function returns a BDS's driver-specific options, excluding also
those from its children. Since we have just removed all children
options from bs->options there's no need to do this last step.
We allow references to children, though ("backing": "node0"), so those
we still have to remove.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If bdrv_reopen() succeeds then bs->explicit_options is updated with
the new values, but bs->options never changes.
Here's an example:
{ "execute": "blockdev-add",
"arguments": {
"driver": "qcow2",
"node-name": "hd0",
"overlap-check": "all",
"file": {
"driver": "file",
"filename": "hd0.qcow2"
}
}
}
After this, both bs->options and bs->explicit_options contain
"overlap-check": "all".
Now let's change that using qemu-io's reopen command:
(qemu) qemu-io hd0 "reopen -o overlap-check=none"
After this, bs->explicit_options contains the new value but
bs->options still keeps the old one.
This patch updates bs->options after a BDS has been successfully
reopened.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If a bdrv_reopen_multiple() call fails, then the explicit_options
QDict has to be deleted for every entry in the reopen queue. This must
happen regardless of whether that entry's bdrv_reopen_prepare() call
succeeded or not.
This patch simplifies the cleanup code a bit.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When bdrv_open_inherit() opens a BlockDriverState the options QDict
can contain options for some of its children, passed in the form of
child-name.option=value
So while each child is opened with that subset of options, those same
options remain stored in the parent BDS, leaving (at least) two copies
of each one of them ("child-name.option=value" in the parent and
"option=value" in the child).
Having the children options stored in the parent is unnecessary and it
can easily lead to an inconsistent state:
$ qemu-img create -f qcow2 hd0.qcow2 10M
$ qemu-img create -f qcow2 -b hd0.qcow2 hd1.qcow2
$ qemu-img create -f qcow2 -b hd1.qcow2 hd2.qcow2
$ $QEMU -drive file=hd2.qcow2,node-name=hd2,backing.node-name=hd1
This opens a chain of images hd0 <- hd1 <- hd2. Now let's remove hd1
using block_stream:
(qemu) block_stream hd2 0 hd0.qcow2
After this hd2 contains backing.node-name=hd1, which is no longer
correct because hd1 doesn't exist anymore.
This patch removes all children options from the parent dictionaries
at the end of bdrv_open_inherit() and bdrv_reopen_queue_child().
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Commit dcf94a23b1 ('block: Don't poll in parent drain callbacks')
removed polling in bdrv_child_cb_drained_begin() on the grounds that the
original bdrv_drain() already will poll and BdrvChildRole.drained_begin
calls must not cause graph changes (and therefore must not call
aio_poll() or the recursion through the graph will break.
This reasoning is correct for calls through bdrv_do_drained_begin().
However, BdrvChildRole.drained_begin is also called when a node that is
already in a drained section (i.e. bdrv_do_drained_begin() has already
returned and therefore can't poll any more) is attached to a new parent.
In this case, we must explicitly poll to have all requests completed
before the drained new child can be attached to the parent.
In bdrv_replace_child_noperm(), we know that we're not inside the
recursion of bdrv_do_drained_begin() because graph changes are not
allowed there, and bdrv_replace_child_noperm() is a graph change. The
call of BdrvChildRole.drained_begin() must therefore be followed by a
BDRV_POLL_WHILE() that waits for the completion of requests.
Reported-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If the user passes a too long node name string, we silently truncate it
to fit into BlockDriverState.node_name, i.e. to 31 characters. Apart
from surprising the user when the node has a different name than
requested, this also bypasses the check for duplicate names, so that the
same name can be assigned to multiple nodes.
Fix this by just making too long node names an error.
Reported-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This allows using the two constants outside of block.c, which will
happen in a subsequent patch.
Signed-off-by: Ari Sundholm <ari@tuxera.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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>
bdrv_truncate() is an operation that can block (even for a quite long
time, depending on the PreallocMode) in I/O paths that shouldn't block.
Convert it to a coroutine_fn so that we have the infrastructure for
drivers to make their .bdrv_co_truncate implementation asynchronous.
This change could potentially introduce new race conditions because
bdrv_truncate() isn't necessarily executed atomically any more. Whether
this is a problem needs to be evaluated for each block driver that
supports truncate:
* file-posix/win32, gluster, iscsi, nfs, rbd, ssh, sheepdog: The
protocol drivers are trivially safe because they don't actually yield
yet, so there is no change in behaviour.
* copy-on-read, crypto, raw-format: Essentially just filter drivers that
pass the request to a child node, no problem.
* qcow2: The implementation modifies metadata, so it needs to hold
s->lock to be safe with concurrent I/O requests. In order to avoid
double locking, this requires pulling the locking out into
preallocate_co() and using qcow2_write_caches() instead of
bdrv_flush().
* qed: Does a single header update, this is fine without locking.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Currently, bdrv_replace_node() refuses to create loops from one BDS to
itself if the BDS to be replaced is the backing node of the BDS to
replace it: Say there is a node A and a node B. Replacing B by A means
making all references to B point to A. If B is a child of A (i.e. A has
a reference to B), that would mean we would have to make this reference
point to A itself -- so we'd create a loop.
bdrv_replace_node() (through should_update_child()) refuses to do so if
B is the backing node of A. There is no reason why we should create
loops if B is not the backing node of A, though. The BDS graph should
never contain loops, so we should always refuse to create them.
If B is a child of A and B is to be replaced by A, we should simply
leave B in place there because it is the most sensible choice.
A more specific argument would be: Putting filter drivers into the BDS
graph is basically the same as appending an overlay to a backing chain.
But the main child BDS of a filter driver is not "backing" but "file",
so restricting the no-loop rule to backing nodes would fail here.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20180613181823.13618-7-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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>
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>
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>
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>
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>
There are numerous QDict functions that have been introduced for and are
used only by the block layer. Move their declarations into an own
header file to reflect that.
While qdict_extract_subqdict() is in fact used outside of the block
layer (in util/qemu-config.c), it is still a function related very
closely to how the block layer works with nested QDicts, namely by
sometimes flattening them. Therefore, its declaration is put into this
header as well and util/qemu-config.c includes it with a comment stating
exactly which function it needs.
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20180509165530.29561-7-mreitz@redhat.com>
[Copyright note tweaked, superfluous includes dropped]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Kevin Wolf