block: Revert .bdrv_drained_begin/end to non-coroutine_fn

Polling during bdrv_drained_end() can be problematic (and in the future,
we may get cases for bdrv_drained_begin() where polling is forbidde

block: Revert .bdrv_drained_begin/end to non-coroutine_fn

Polling during bdrv_drained_end() can be problematic (and in the future,
we may get cases for bdrv_drained_begin() where polling is forbidden,
and we don't care about already in-flight requests, but just want to
prevent new requests from arriving).

The .bdrv_drained_begin/end callbacks running in a coroutine is the only
reason why we have to do this polling, so make them non-coroutine
callbacks again. None of the callers actually yield any more.

This means that bdrv_drained_end() effectively doesn't poll any more,
even if AIO_WAIT_WHILE() loops are still there (their condition is false
from the beginning). This is generally not a problem, but in
test-bdrv-drain, some additional explicit aio_poll() calls need to be
added because the test case wants to verify the final state after BHs
have executed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221118174110.55183-4-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: Make bdrv_child_get_parent_aio_context I/O

We want to use bdrv_child_get_parent_aio_context() from
bdrv_parent_drained_{begin,end}_single(), both of which are "I/O or GS"
functions.

Prior to

block: Make bdrv_child_get_parent_aio_context I/O

We want to use bdrv_child_get_parent_aio_context() from
bdrv_parent_drained_{begin,end}_single(), both of which are "I/O or GS"
functions.

Prior to 3ed4f708fe1, all the implementations were I/O code anyway.
3ed4f708fe1 has put block jobs' AioContext field under the job mutex, so
to make child_job_get_parent_aio_context() work in an I/O context, we
need to take that lock there.

Furthermore, blk_root_get_parent_aio_context() is not marked as
anything, but is safe to run in an I/O context, so mark it that way now.
(blk_get_aio_context() is an I/O code function.)

With that done, all implementations explicitly are I/O code, so we can
mark bdrv_child_get_parent_aio_context() as I/O code, too, so callers
know it is safe to run from both GS and I/O contexts.

Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221107151321.211175-2-hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: add missing coroutine_fn annotation to BlockDriverState callbacks

Signed-off-by: Alberto Faria <afaria@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <202210131237

block: add missing coroutine_fn annotation to BlockDriverState callbacks

Signed-off-by: Alberto Faria <afaria@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20221013123711.620631-9-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: remove all unused ->can_set_aio_ctx and ->set_aio_ctx callbacks

Together with all _can_set_ and _set_ APIs, as they are not needed
anymore.

Signed-off-by: Emanuele Giuseppe Esposito <eesposi

block: remove all unused ->can_set_aio_ctx and ->set_aio_ctx callbacks

Together with all _can_set_ and _set_ APIs, as they are not needed
anymore.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221025084952.2139888-9-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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bdrv_change_aio_context: use hash table instead of list of visited nodes

Minor performance improvement, but given that we have hash tables
available, avoid iterating in the visited nodes list every

bdrv_change_aio_context: use hash table instead of list of visited nodes

Minor performance improvement, but given that we have hash tables
available, avoid iterating in the visited nodes list every time just
to check if a node has been already visited.

The data structure is not actually a proper hash map, but an hash set,
as we are just adding nodes and not key,value pairs.

Suggested-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221025084952.2139888-4-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: use transactions as a replacement of ->{can_}set_aio_context()

Simplify the way the aiocontext can be changed in a BDS graph.
There are currently two problems in bdrv_try_set_aio_context:
- T

block: use transactions as a replacement of ->{can_}set_aio_context()

Simplify the way the aiocontext can be changed in a BDS graph.
There are currently two problems in bdrv_try_set_aio_context:
- There is a confusion of AioContext locks taken and released, because
we assume that old aiocontext is always taken and new one is
taken inside.

- It doesn't look very safe to call bdrv_drained_begin while some
nodes have already switched to the new aiocontext and others haven't.
This could be especially dangerous because bdrv_drained_begin polls, so
something else could be executed while graph is in an inconsistent
state.

Additional minor nitpick: can_set and set_ callbacks both traverse the
graph, both using the ignored list of visited nodes in a different way.

Therefore, get rid of all of this and introduce a new callback,
change_aio_context, that uses transactions to efficiently, cleanly
and most importantly safely change the aiocontext of a graph.

This new callback is a "merge" of the two previous ones:
- Just like can_set_aio_context, recursively traverses the graph.
Marks all nodes that are visited using a GList, and checks if
they *could* change the aio_context.
- For each node that passes the above check, drain it and add a new transaction
that implements a callback that effectively changes the aiocontext.
- Once done, the recursive function returns if *all* nodes can change
the AioContext. If so, commit the above transactions.
Regardless of the outcome, call transaction.clean() to undo all drains
done in the recursion.
- The transaction list is scanned only after all nodes are being drained, so
we are sure that they all are in the same context, and then
we switch their AioContext, concluding the drain only after all nodes
switched to the new AioContext. In this way we make sure that
bdrv_drained_begin() is always called under the old AioContext, and
bdrv_drained_end() under the new one.
- Because of the above, we don't need to release and re-acquire the
old AioContext every time, as everything is done once (and not
per-node drain and aiocontext change).

Note that the "change" API is not yet invoked anywhere.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20221025084952.2139888-3-eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: Manipulate bs->file / bs->backing pointers in .attach/.detach

bs->file and bs->backing are a kind of duplication of part of
bs->children. But very useful diplication, so let's not drop them a

block: Manipulate bs->file / bs->backing pointers in .attach/.detach

bs->file and bs->backing are a kind of duplication of part of
bs->children. But very useful diplication, so let's not drop them at
all:)

We should manage bs->file and bs->backing in same place, where we
manage bs->children, to keep them in sync.

Moreover, generic io paths are unprepared to BdrvChild without a bs, so
it's double good to clear bs->file / bs->backing when we detach the
child.

Detach is simple: if we detach bs->file or bs->backing child, just
set corresponding field to NULL.

Attach is a bit more complicated. But we still can precisely detect
should we set one of bs->file / bs->backing or not:

- if role is BDRV_CHILD_COW, we definitely deal with bs->backing
- else, if role is BDRV_CHILD_FILTERED (it must be also
BDRV_CHILD_PRIMARY), it's a filtered child. Use
bs->drv->filtered_child_is_backing to chose the pointer field to
modify.
- else, if role is BDRV_CHILD_PRIMARY, we deal with bs->file
- in all other cases, it's neither bs->backing nor bs->file. It's some
other child and we shouldn't care

OK. This change brings one more good thing: we can (and should) get rid
of all indirect pointers in the block-graph-change transactions:

bdrv_attach_child_common() stores BdrvChild** into transaction to clear
it on abort.

bdrv_attach_child_common() has two callers: bdrv_attach_child_noperm()
just pass-through this feature, bdrv_root_attach_child() doesn't need
the feature.

Look at bdrv_attach_child_noperm() callers:
- bdrv_attach_child() doesn't need the feature
- bdrv_set_file_or_backing_noperm() uses the feature to manage
bs->file and bs->backing, we don't want it anymore
- bdrv_append() uses the feature to manage bs->backing, again we
don't want it anymore

So, we should drop this stuff! Great!

We could probably keep BdrvChild** argument to keep the int return
value, but it seems not worth the complexity.

Finally, we now set .file / .backing automatically in generic code and
want to restring setting them by hand outside of .attach/.detach.
So, this patch cleanups all remaining places where they were set.
To find such places I use:

git grep '\->file ='
git grep '\->backing ='
git grep '&.*\<backing\>'
git grep '&.*\<file\>'

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220726201134.924743-14-vsementsov@yandex-team.ru>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

test-bdrv-graph-mod: fix filters to be filters

bdrv_pass_through is used as filter, even all node variables has
corresponding names. We want to append it, so it should be
backing-child-based filter

test-bdrv-graph-mod: fix filters to be filters

bdrv_pass_through is used as filter, even all node variables has
corresponding names. We want to append it, so it should be
backing-child-based filter like mirror_top.
So, in test_update_perm_tree, first child should be DATA, as we don't
want filters with two filtered children.

bdrv_exclusive_writer is used as a filter once. So it should be filter
anyway. We want to append it, so it should be backing-child-based
fitler too.

Make all FILTERED children to be PRIMARY as well. We are going to force
this rule by assertion soon.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220726201134.924743-7-vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: BlockDriver: add .filtered_child_is_backing field

Unfortunately not all filters use .file child as filtered child. Two
exclusions are mirror_top and commit_top. Happily they both are private

block: BlockDriver: add .filtered_child_is_backing field

Unfortunately not all filters use .file child as filtered child. Two
exclusions are mirror_top and commit_top. Happily they both are private
filters. Bad thing is that this inconsistency is observable through qmp
commands query-block / query-named-block-nodes. So, could we just
change mirror_top and commit_top to use file child as all other filter
driver is an open question. Probably, we could do that with some kind
of deprecation period, but how to warn users during it?

For now, let's just add a field so we can distinguish them in generic
code, it will be used in further commits.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220726201134.924743-2-vsementsov@yandex-team.ru>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block: Refactor get_tmp_filename()

At present there are two callers of get_tmp_filename() and they are
inconsistent.

One does:

/* TODO: extra byte is a hack to ensure MAX_PATH space on Windows

block: Refactor get_tmp_filename()

At present there are two callers of get_tmp_filename() and they are
inconsistent.

One does:

/* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */
char *tmp_filename = g_malloc0(PATH_MAX + 1);
...
ret = get_tmp_filename(tmp_filename, PATH_MAX + 1);

while the other does:

s->qcow_filename = g_malloc(PATH_MAX);
ret = get_tmp_filename(s->qcow_filename, PATH_MAX);

As we can see different 'size' arguments are passed. There are also
platform specific implementations inside the function, and the use
of snprintf is really undesirable.

The function name is also misleading. It creates a temporary file,
not just a filename.

Refactor this routine by changing its name and signature to:

char *create_tmp_file(Error **errp)

and use g_get_tmp_dir() / g_mkstemp() for a consistent implementation.

While we are here, add some comments to mention that /var/tmp is
preferred over /tmp on non-win32 hosts.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Message-Id: <20221010040432.3380478-2-bin.meng@windriver.com>
[kwolf: Fixed incorrect errno negation and iotest 051]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

block: return errors from bdrv_register_buf()

Registering an I/O buffer is only a performance optimization hint but it
is still necessary to return errors when it fails.

Later patches will need to

block: return errors from bdrv_register_buf()

Registering an I/O buffer is only a performance optimization hint but it
is still necessary to return errors when it fails.

Later patches will need to detect errors when registering buffers but an
immediate advantage is that error_report() calls are no longer needed in
block driver .bdrv_register_buf() functions.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20221013185908.1297568-8-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

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block: use BdrvRequestFlags type for supported flag fields

Use the enum type so GDB displays the enum members instead of printing a
numeric constant.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat

block: use BdrvRequestFlags type for supported flag fields

Use the enum type so GDB displays the enum members instead of printing a
numeric constant.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-6-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

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block: pass size to bdrv_unregister_buf()

The only implementor of bdrv_register_buf() is block/nvme.c, where the
size is not needed when unregistering a buffer. This is because
util/vfio-helpers.c c

block: pass size to bdrv_unregister_buf()

The only implementor of bdrv_register_buf() is block/nvme.c, where the
size is not needed when unregistering a buffer. This is because
util/vfio-helpers.c can look up mappings by address.

Future block drivers that implement bdrv_register_buf() may not be able
to do their job given only the buffer address. Add a size argument to
bdrv_unregister_buf().

Also document the assumptions about
bdrv_register_buf()/bdrv_unregister_buf() calls. The same <host, size>
values that were given to bdrv_register_buf() must be given to
bdrv_unregister_buf().

gcc 11.2.1 emits a spurious warning that img_bench()'s buf_size local
variable might be uninitialized, so it's necessary to silence the
compiler.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20221013185908.1297568-5-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

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block: introduce snapshot-access block driver

The new block driver simply utilizes snapshot-access API of underlying
block node.

In further patches we want to use it like this:

[guest]

block: introduce snapshot-access block driver

The new block driver simply utilizes snapshot-access API of underlying
block node.

In further patches we want to use it like this:

[guest] [NBD export]
| |
| root | root
v file v
[copy-before-write]<------[snapshot-access]
| |
| file | target
v v
[active-disk] [temp.img]

This way, NBD client will be able to read snapshotted state of active
disk, when active disk is continued to be written by guest. This is
known as "fleecing", and currently uses another scheme based on qcow2
temporary image which backing file is active-disk. New scheme comes
with benefits - see next commit.

The other possible application is exporting internal snapshots of
qcow2, like this:

[guest] [NBD export]
| |
| root | root
v file v
[qcow2]<---------[snapshot-access]

For this, we'll need to implement snapshot-access API handlers in
qcow2 driver, and improve snapshot-access block driver (and API) to
make it possible to select snapshot by name. Another thing to improve
is size of snapshot. Now for simplicity we just use size of bs->file,
which is OK for backup, but for qcow2 snapshots export we'll need to
imporve snapshot-access API to get size of snapshot.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20220303194349.2304213-12-vsementsov@virtuozzo.com>
[hreitz: Rebased on block GS/IO split]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

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block/io: introduce block driver snapshot-access API

Add new block driver handlers and corresponding generic wrappers.
It will be used to allow copy-before-write filter to provide
reach fleecing int

block/io: introduce block driver snapshot-access API

Add new block driver handlers and corresponding generic wrappers.
It will be used to allow copy-before-write filter to provide
reach fleecing interface in further commit.

In future this approach may be used to allow reading qcow2 internal
snapshots, for example to export them through NBD.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220303194349.2304213-11-vsementsov@virtuozzo.com>
[hreitz: Rebased on block GS/IO split]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

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block_int-common.h: split function pointers in BdrvChildClass

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-28-eesposit@redhat.com>
Signed-off-by

block_int-common.h: split function pointers in BdrvChildClass

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-28-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block_int-common.h: split function pointers in BlockDriver

Similar to the header split, also the function pointers in BlockDriver
can be split in I/O and global state.

Signed-off-by: Emanuele Giuse

block_int-common.h: split function pointers in BlockDriver

Similar to the header split, also the function pointers in BlockDriver
can be split in I/O and global state.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-26-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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include/block/block_int: split header into I/O and global state API

Similarly to the previous patch, split block_int.h
in block_int-io.h and block_int-global-state.h

block_int-common.h contains the

include/block/block_int: split header into I/O and global state API

Similarly to the previous patch, split block_int.h
in block_int-io.h and block_int-global-state.h

block_int-common.h contains the structures shared between
the two headers, and the functions that can't be categorized as
I/O or global state.

Assertions are added in the next patch.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-12-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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