During shutdown, blockdev_close_all_bdrv_states() drops any block node
references that are still owned by the monitor (i.e. the user). However,
in doing so, it forgot to also remove the node from monitor_bdrv_states
(which qmp_blockdev_del() correctly does), which means that later calls
of bdrv_first()/bdrv_next() will still return the (now stale) pointer to
the node.
Usually there is no such call after this point, but in some cases it can
happen. In the reported case, there was an ongoing migration, and the
migration thread wasn't shut down yet: migration_shutdown() called by
qemu_cleanup() doesn't actually wait for the migration to be shut down,
but may just move it to MIGRATION_STATUS_CANCELLING. The next time
migration_iteration_finish() runs, it sees the status and tries to
re-activate all block devices that migration may have previously
inactivated. This is where bdrv_first()/bdrv_next() get called and the
access to the already freed node happens.
It is debatable if migration_shutdown() should really return before
migration has settled, but leaving a dangling pointer in the list of
monitor-owned block nodes is clearly a bug either way and fixing it
solves the immediate problem, so fix it.
Cc: qemu-stable@nongnu.org
Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20251215150714.130214-1-kwolf@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This patch allows stats-intervals to be used for storage
devices with the -device option. It accepts a list of interval
lengths in JSON format.
It configures and collects the stats in the BlockBackend layer
through the storage device that consumes the BlockBackend.
Signed-off-by: Chandan Somani <csomani@redhat.com>
Message-ID: <20251003220039.1336663-1-csomani@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The function bdrv_inactivate() calls bdrv_drain_all_begin(), which
needs to be called with the graph unlocked, so either
bdrv_inactivate() should be marked as GRAPH_UNLOCKED or the drain
needs to be moved to the callers. The caller in
qmp_blockdev_set_active() requires that the locked section covers
bdrv_find_node() too, so the latter alternative is chosen.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-36-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Nearly all callers (outside of the tests) are already using the
_drained() variant of the function. It doesn't seem worth keeping.
Simply adapt the remaining callers of bdrv_set_backing_hd() and rename
bdrv_set_backing_hd_drained() to bdrv_set_backing_hd().
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-31-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
By using the appropriate variants bdrv_set_backing_hd_drained() and
bdrv_try_change_aio_context_locked(), there only needs to be a single
drained and write-locked section in external_snapshot_abort().
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-30-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Many write-locked sections are also drained sections. A new
bdrv_graph_wrunlock_drained() wrapper around bdrv_graph_wrunlock() is
introduced, which will begin a drained section first. A global
variable is used so bdrv_graph_wrunlock() knows if it also needs
to end such a drained section. Both the aio_poll call in
bdrv_graph_wrlock() and the aio_bh_poll() in bdrv_graph_wrunlock()
can re-enter a write-locked section. While for the latter, ending the
drain could be moved to before the call, the former requires that the
variable is a counter and not just a boolean.
Since the wrapper calls bdrv_drain_all_begin(), which must be called
with the graph unlocked, mark the wrapper as GRAPH_UNLOCKED too.
The switch to the new helpers was generated with the following
commands and then manually checked:
find . -name '*.c' -exec sed -i -z 's/bdrv_drain_all_begin();\n\s*bdrv_graph_wrlock();/bdrv_graph_wrlock_drained();/g' {} ';'
find . -name '*.c' -exec sed -i -z 's/bdrv_graph_wrunlock();\n\s*bdrv_drain_all_end();/bdrv_graph_wrunlock();/g' {} ';'
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-25-f.ebner@proxmox.com>
[kwolf: Removed redundant GRAPH_UNLOCKED]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This is part of resolving the deadlock mentioned in commit "block:
move draining out of bdrv_change_aio_context() and mark GRAPH_RDLOCK".
The quorum_add_child() callback runs under the graph lock, so it is
not allowed to drain. It is only called as the .bdrv_add_child()
callback, which is only called in the bdrv_add_child() function, which
also runs under the graph lock.
The bdrv_add_child() function is called by qmp_x_blockdev_change(),
where a drained section is introduced.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-15-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This is part of resolving the deadlock mentioned in commit "block:
move draining out of bdrv_change_aio_context() and mark GRAPH_RDLOCK".
Convert the function to a _locked() version that has to be called with
the graph lock held and add a convenience wrapper that has to be
called with the graph unlocked, which drains and takes the lock
itself. Since bdrv_try_change_aio_context() is global state code, the
wrapper is too.
Callers are adapted to use the appropriate variant, depending on
whether the caller already holds the lock. In the
test_set_aio_context() unit test, prior drains can be removed, because
draining already happens inside the new wrapper.
Note that bdrv_attach_child_common_abort(), bdrv_attach_child_common()
and bdrv_root_unref_child() hold the graph lock and are not actually
allowed to drain either. This will be addressed in the following
commits.
Functions like qmp_blockdev_mirror() query the nodes to act on before
draining and locking. In theory, draining could invalidate those nodes.
This kind of issue is not addressed by these commits.
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250530151125.955508-10-f.ebner@proxmox.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This is in preparation to mark bdrv_drained_begin() as GRAPH_UNLOCKED.
More granular draining is not trivially possible, because
bdrv_snapshot_delete() can recursively call itself.
The return value of bdrv_all_delete_snapshot() changes from -1 to
-errno propagated from failed sub-calls. This is fine for the existing
callers of bdrv_all_delete_snapshot().
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20250530151125.955508-4-f.ebner@proxmox.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The two callers to a mirror job (drive-mirror and blockdev-mirror) set
zero_target precisely when sync mode == FULL, with the one exception
that drive-mirror skips zeroing the target if it was newly created and
reads as zero. But given the previous patch, that exception is
equally captured by target_is_zero.
Meanwhile, there is another slight wrinkle, fortunately caught by
iotest 185: if the caller uses "sync":"top" but the source has no
backing file, the code in blockdev.c was changing sync to be FULL, but
only after it had set zero_target=false. In mirror.c, prior to recent
patches, this didn't matter: the only places that inspected sync were
setting is_none_mode (both TOP and FULL had set that to false), and
mirror_start() setting base = mode == MIRROR_SYNC_MODE_TOP ?
bdrv_backing_chain_next(bs) : NULL. But now that we are passing sync
around, the slammed sync mode would result in a new pre-zeroing pass
even when the user had passed "sync":"top" in an effort to skip
pre-zeroing. Fortunately, the assignment of base when bs has no
backing chain still works out to NULL if we don't slam things. So
with the forced change of sync ripped out of blockdev.c, the sync mode
is passed through the full callstack unmolested, and we can now
reliably reconstruct the same settings as what used to be passed in by
zero_target=false, without the redundant parameter.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20250509204341.3553601-24-eblake@redhat.com>
Reviewed-by: Sunny Zhu <sunnyzhyy@qq.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[eblake: Fix regression in iotest 185]
Signed-off-by: Eric Blake <eblake@redhat.com>
QEMU has an optimization for a just-created drive-mirror destination
that is not possible for blockdev-mirror (which can't create the
destination) - any time we know the destination starts life as all
zeroes, we can skip a pre-zeroing pass on the destination. Recent
patches have added an improved heuristic for detecting if a file
contains all zeroes, and we plan to use that heuristic in upcoming
patches. But since a heuristic cannot quickly detect all scenarios,
and there may be cases where the caller is aware of information that
QEMU cannot learn quickly, it makes sense to have a way to tell QEMU
to assume facts about the destination that can make the mirror
operation faster. Given our existing example of "qemu-img convert
--target-is-zero", it is time to expose this override in QMP for
blockdev-mirror as well.
This patch results in some slight redundancy between the older
s->zero_target (set any time mode==FULL and the destination image was
not just created - ie. clear if drive-mirror is asking to skip the
pre-zero pass) and the newly-introduced s->target_is_zero (in addition
to the QMP override, it is set when drive-mirror creates the
destination image); this will be cleaned up in the next patch.
There is also a subtlety that we must consider. When drive-mirror is
passing target_is_zero on behalf of a just-created image, we know the
image is sparse (skipping the pre-zeroing keeps it that way), so it
doesn't matter whether the destination also has "discard":"unmap" and
"detect-zeroes":"unmap". But now that we are letting the user set the
knob for target-is-zero, if the user passes a pre-existing file that
is fully allocated, it is fine to leave the file fully allocated under
"detect-zeroes":"on", but if the file is open with
"detect-zeroes":"unmap", we should really be trying harder to punch
holes in the destination for every region of zeroes copied from the
source. The easiest way to do this is to still run the pre-zeroing
pass (turning the entire destination file sparse before populating
just the allocated portions of the source), even though that currently
results in double I/O to the portions of the file that are allocated.
A later patch will add further optimizations to reduce redundant
zeroing I/O during the mirror operation.
Since "target-is-zero":true is designed for optimizations, it is okay
to silently ignore the parameter rather than erroring if the user ever
sets the parameter in a scenario where the mirror job can't exploit it
(for example, when doing "sync":"top" instead of "sync":"full", we
can't pre-zero, so setting the parameter won't make a speed
difference).
Signed-off-by: Eric Blake <eblake@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20250509204341.3553601-23-eblake@redhat.com>
Reviewed-by: Sunny Zhu <sunnyzhyy@qq.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch extends the blockdev-backup QMP command to allow users to specify
how to behave when IO errors occur during copy-before-write operations.
Previously, the behavior was fixed and could not be controlled by the user.
The new 'on-cbw-error' option can be set to one of two values:
- 'break-guest-write': Forwards the IO error to the guest and triggers
the on-source-error policy. This preserves snapshot integrity at the
expense of guest IO operations.
- 'break-snapshot': Allows the guest OS to continue running normally,
but invalidates the snapshot and aborts related jobs. This prioritizes
guest operation over backup consistency.
This enhancement provides more flexibility for backup operations in different
environments where requirements for guest availability versus backup
consistency may vary.
The default behavior remains unchanged to maintain backward compatibility.
Signed-off-by: Raman Dzehtsiar <Raman.Dzehtsiar@gmail.com>
Message-ID: <20250414090025.828660-1-Raman.Dzehtsiar@gmail.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
[vsementsov: fix long lines]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Tested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
The general expectation is that header files should follow the same
file/path naming scheme as the corresponding source file. There are
various historical exceptions to this practice in QEMU, with one of
the most notable being the include/qapi/qmp/ directory. Most of the
headers there correspond to source files in qobject/.
This patch corrects most of that inconsistency by creating
include/qobject/ and moving the headers for qobject/ there.
This also fixes MAINTAINERS for include/qapi/qmp/dispatch.h:
scripts/get_maintainer.pl now reports "QAPI" instead of "No
maintainers found".
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com> #s390x
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20241118151235.2665921-2-armbru@redhat.com>
[Rebased]
The system emulator tries to automatically activate and inactivate block
nodes at the right point during migration. However, there are still
cases where it's necessary that the user can do this manually.
Images are only activated on the destination VM of a migration when the
VM is actually resumed. If the VM was paused, this doesn't happen
automatically. The user may want to perform some operation on a block
device (e.g. taking a snapshot or starting a block job) without also
resuming the VM yet. This is an example where a manual command is
necessary.
Another example is VM migration when the image files are opened by an
external qemu-storage-daemon instance on each side. In this case, the
process that needs to hand over the images isn't even part of the
migration and can't know when the migration completes. Management tools
need a way to explicitly inactivate images on the source and activate
them on the destination.
This adds a new blockdev-set-active QMP command that lets the user
change the status of individual nodes (this is necessary in
qemu-storage-daemon because it could be serving multiple VMs and only
one of them migrates at a time). For convenience, operating on all
devices (like QEMU does automatically during migration) is offered as an
option, too, and can be used in the context of single VM.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250204211407.381505-9-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Putting an active block node on top of an inactive one is strictly
speaking an invalid configuration and the next patch will turn it into a
hard error.
However, taking a snapshot while disk images are inactive after
completing migration has an important use case: After migrating to a
file, taking an external snapshot is what is needed to take a full VM
snapshot.
In order for this to keep working after the later patches, change
creating a snapshot such that it automatically inactivates an overlay
that is added on top of an already inactive node.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250204211407.381505-4-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Headers in include/sysemu/ are not only related to system
*emulation*, they are also used by virtualization. Rename
as system/ which is clearer.
Files renamed manually then mechanical change using sed tool.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Message-Id: <20241203172445.28576-1-philmd@linaro.org>
In the context of backup fleecing, discarding the source will not work
when the fleecing image has a larger granularity than the one used for
block-copy operations (can happen if the backup target has smaller
cluster size), because cbw_co_pdiscard_snapshot() will align down the
discard requests and thus effectively ignore then.
To make @discard-source work in such a scenario, allow specifying the
minimum cluster size used for block-copy operations and thus in
particular also the granularity for discard requests to the source.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Acked-by: Markus Armbruster <armbru@redhat.com> (QAPI schema)
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-Id: <20240711120915.310243-3-f.ebner@proxmox.com>
[vsementsov: switch version to 9.2 in QAPI doc]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Add a parameter that enables discard-after-copy. That is mostly useful
in "push backup with fleecing" scheme, when source is snapshot-access
format driver node, based on copy-before-write filter snapshot-access
API:
[guest] [snapshot-access] ~~ blockdev-backup ~~> [backup target]
| |
| root | file
v v
[copy-before-write]
| |
| file | target
v v
[active disk] [temp.img]
In this case discard-after-copy does two things:
- discard data in temp.img to save disk space
- avoid further copy-before-write operation in discarded area
Note that we have to declare WRITE permission on source in
copy-before-write filter, for discard to work. Still we can't take it
unconditionally, as it will break normal backup from RO source. So, we
have to add a parameter and pass it thorough bdrv_open flags.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20240313152822.626493-5-vsementsov@yandex-team.ru>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
external_snapshot_action() reports bdrv_flush() failure to its caller
as
An IO error has occurred
The errno code returned by bdrv_flush() is lost.
Improve this to
Write to node '<device or node name>' failed: <description of errno>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240513141703.549874-2-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Address the comment added in commit 4629ed1e98
("qerror: Finally unused, clean up"), from 2015:
/*
* These macros will go away, please don't use
* in new code, and do not add new ones!
*/
Mechanical transformation using sed, and manual cleanup.
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240312141343.3168265-4-armbru@redhat.com>
