Now that the API offers also _locked() functions, take advantage
of it and give also the caller control to take the lock and call
_locked functions.
This makes sense especially when we have for loops, because it
makes no sense to have:
for(job = job_next(); ...)
where each job_next() takes the lock internally.
Instead we want
JOB_LOCK_GUARD();
for(job = job_next_locked(); ...)
In addition, protect also direct field accesses, by either creating a
new critical section or widening the existing ones.
Note: at this stage, job_{lock/unlock} and job lock guard macros
are *nop*.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-Id: <20220926093214.506243-12-eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Callers of coroutine_fn must be coroutine_fn themselves, or the call
must be within "if (qemu_in_coroutine())". Apply coroutine_fn to
functions where this holds.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220922084924.201610-3-pbonzini@redhat.com>
[kwolf: Fixed up coding style]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Swap 'buf' and 'bytes' around for consistency with
blk_co_{pread,pwrite}(), and in preparation to implement these functions
using generated_co_wrapper.
Callers were updated using this Coccinelle script:
@@ expression blk, offset, buf, bytes, flags; @@
- blk_pread(blk, offset, buf, bytes, flags)
+ blk_pread(blk, offset, bytes, buf, flags)
@@ expression blk, offset, buf, bytes, flags; @@
- blk_pwrite(blk, offset, buf, bytes, flags)
+ blk_pwrite(blk, offset, bytes, buf, flags)
It had no effect on hw/block/nand.c, presumably due to the #if, so that
file was updated manually.
Overly-long lines were then fixed by hand.
Signed-off-by: Alberto Faria <afaria@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220705161527.1054072-4-afaria@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
For consistency with other I/O functions, and in preparation to
implement it using generated_co_wrapper.
Callers were updated using this Coccinelle script:
@@ expression blk, offset, buf, bytes; @@
- blk_pread(blk, offset, buf, bytes)
+ blk_pread(blk, offset, buf, bytes, 0)
It had no effect on hw/block/nand.c, presumably due to the #if, so that
file was updated manually.
Overly-long lines were then fixed by hand.
Signed-off-by: Alberto Faria <afaria@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220705161527.1054072-3-afaria@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
They currently return the value of their 'bytes' parameter on success.
Make them return 0 instead, for consistency with other I/O functions and
in preparation to implement them using generated_co_wrapper. This also
makes it clear that short reads/writes are not possible.
Signed-off-by: Alberto Faria <afaria@redhat.com>
Message-Id: <20220705161527.1054072-2-afaria@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
This function is safe to call in an I/O context, and qcow2_do_open()
does so (invoked in an I/O context by qcow2_co_invalidate_cache()).
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220427114057.36651-2-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Replace the global variables with inlined helper functions. getpagesize() is very
likely annotated with a "const" function attribute (at least with glibc), and thus
optimization should apply even better.
This avoids the need for a constructor initialization too.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220323155743.1585078-12-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-29-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-27-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
block coroutines functions run in different aiocontext, and are
not protected by the BQL. Therefore are I/O.
On the other side, generated_co_wrapper functions use BDRV_POLL_WHILE,
meaning the caller can either be the main loop or a specific iothread.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-25-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Following the assertion derived from the API split,
propagate the assertion also in the static functions.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-18-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We want to be sure that the functions that write the child and
parent list of a bs are under BQL and drain.
BQL prevents from concurrent writings from the GS API, while
drains protect from I/O.
TODO: drains are missing in some functions using this assert.
Therefore a proper assertion will fail. Because adding drains
requires additional discussions, they will be added in future
series.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-15-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Mark all I/O functions with IO_CODE, and all "I/O OR GS" with
IO_OR_GS_CODE.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-14-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-13-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Now that we "covered" the three main cases where the
permission API was being used under BQL (fuse,
amend and invalidate_cache), we can safely assert for
the permission functions implemented in block.c
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-11-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Mark all I/O functions with IO_CODE, and all "I/O OR GS" with
IO_OR_GS_CODE.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-6-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
All the global state (GS) API functions will check that
qemu_in_main_thread() returns true. If not, it means
that the safety of BQL cannot be guaranteed, and
they need to be moved to I/O.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-5-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
block.h currently contains a mix of functions:
some of them run under the BQL and modify the block layer graph,
others are instead thread-safe and perform I/O in iothreads.
Some others can only be called by either the main loop or the
iothread running the AioContext (and not other iothreads),
and using them in another thread would cause deadlocks, and therefore
it is not ideal to define them as I/O.
It is not easy to understand which function is part of which
group (I/O vs GS vs "I/O or GS"), and this patch aims to clarify it.
The "GS" functions need the BQL, and often use
aio_context_acquire/release and/or drain to be sure they
can modify the graph safely.
The I/O function are instead thread safe, and can run in
any AioContext.
"I/O or GS" functions run instead in the main loop or in
a single iothread, and use BDRV_POLL_WHILE().
By splitting the header in two files, block-io.h
and block-global-state.h we have a clearer view on what
needs what kind of protection. block-common.h
contains common structures shared by both headers.
block.h is left there for legacy and to avoid changing
all includes in all c files that use the block APIs.
Assertions are added in the next patch.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220303151616.325444-4-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Split bdrv_co_invalidate cache in two: the Global State (under BQL)
code that takes care of permissions and running GS callbacks,
and leave only the I/O code (->bdrv_co_invalidate_cache) running in
the I/O coroutine.
The only side effect is that bdrv_co_invalidate_cache is not
recursive anymore, and so is every direct call to
bdrv_invalidate_cache().
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20220209105452.1694545-6-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Following the bdrv_activate renaming, change also the name
of the respective callers.
bdrv_invalidate_cache_all -> bdrv_activate_all
blk_invalidate_cache -> blk_activate
test_sync_op_invalidate_cache -> test_sync_op_activate
No functional change intended.
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220209105452.1694545-5-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This function is currently just a wrapper for bdrv_invalidate_cache(),
but in future will contain the code of bdrv_co_invalidate_cache() that
has to always be protected by BQL, and leave the rest in the I/O
coroutine.
Replace all bdrv_invalidate_cache() invokations with bdrv_activate().
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20220209105452.1694545-4-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Graph modifications should be done in drained section. stream_prepare()
handler of block stream job call bdrv_set_backing_hd() without using
drained section and it's theoretically possible that some IO request
will interleave with graph modification and will use outdated pointers
to removed block nodes.
Some other callers use bdrv_set_backing_hd() not caring about drained
sections too. So it seems good to make a drained section exactly in
bdrv_set_backing_hd().
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20220124173741.2984056-1-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
First, this permission never protected a node from being changed, as
generic child-replacing functions don't check it.
Second, it's a strange thing: it presents a permission of parent node
to change its child. But generally, children are replaced by different
mechanisms, like jobs or qmp commands, not by nodes.
Graph-mod permission is hard to understand. All other permissions
describe operations which done by parent node on its child: read,
write, resize. Graph modification operations are something completely
different.
The only place where BLK_PERM_GRAPH_MOD is used as "perm" (not shared
perm) is mirror_start_job, for s->target. Still modern code should use
bdrv_freeze_backing_chain() to protect from graph modification, if we
don't do it somewhere it may be considered as a bug. So, it's a bit
risky to drop GRAPH_MOD, and analyzing of possible loss of protection
is hard. But one day we should do it, let's do it now.
One more bit of information is that locking the corresponding byte in
file-posix doesn't make sense at all.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210902093754.2352-1-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_backing_overridden is only used in block.c, so there is
no need to leave it in block_int.h
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20211215121140.456939-2-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
In most of the block layer, especially when traversing down from other
BlockDriverStates, we assume that BdrvChild.bs can never be NULL. When
it becomes NULL, it is expected that the corresponding BdrvChild pointer
also becomes NULL and the BdrvChild object is freed.
Therefore, once bdrv_replace_child_noperm() sets the BdrvChild.bs
pointer to NULL, it should also immediately set the corresponding
BdrvChild pointer (like bs->file or bs->backing) to NULL.
In that context, it also makes sense for this function to free the
child. Sometimes we cannot do so, though, because it is called in a
transactional context where the caller might still want to reinstate the
child in the abort branch (and free it only on commit), so this behavior
has to remain optional.
In bdrv_replace_child_tran()'s abort handler, we now rely on the fact
that the BdrvChild passed to bdrv_replace_child_tran() must have had a
non-NULL .bs pointer initially. Make a note of that and assert it.
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211111120829.81329-10-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-10-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
As of a future commit, bdrv_replace_child_noperm() will clear the
indirect BdrvChild pointer passed to it if the new child BDS is NULL.
bdrv_replace_child_tran() will want to let it do that, but revert this
change in its abort handler. For that, we need to have it receive a
BdrvChild ** pointer, too, and keep it stored in the
BdrvReplaceChildState object that we attach to the transaction.
Note that we do not need to store it in the BdrvReplaceChildState when
new_bs is not NULL, because then there is nothing to revert. This is
important so that bdrv_replace_node_noperm() can pass a pointer to a
loop-local variable to bdrv_replace_child_tran() without worrying that
this pointer will outlive one loop iteration.
(Of course, for that to work, bdrv_replace_node_noperm() and in turn
bdrv_replace_node() and its relatives may not be called with a NULL @to
node. Luckily, they already are not, but now we should assert this.)
bdrv_remove_file_or_backing_child() on the other hand needs to ensure
that the indirect pointer it passes will stay valid for the duration of
the transaction. Ensure this by keeping a strong reference to the BDS
whose &bs->backing or &bs->file it passes to bdrv_replace_child_tran(),
and giving up that reference only in the transaction .clean() handler.
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211111120829.81329-9-hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-9-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
As of a future patch, bdrv_replace_child_tran() will take a BdrvChild **
pointer. Prepare for that by getting such a pointer and using it where
applicable, and (dereferenced) as a parameter for
bdrv_replace_child_tran().
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211111120829.81329-7-hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-7-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
bdrv_replace_child_noperm() modifies BdrvChild.bs, and can potentially
set it to NULL. That is dangerous, because BDS parents generally assume
that their children's .bs pointer is never NULL. We therefore want to
let bdrv_replace_child_noperm() set the corresponding BdrvChild pointer
to NULL, too.
This patch lays the foundation for it by passing a BdrvChild ** pointer
to bdrv_replace_child_noperm() so that it can later use it to NULL the
BdrvChild pointer immediately after setting BdrvChild.bs to NULL.
(We will still need to undertake some intermediate steps, though.)
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211111120829.81329-6-hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-6-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
bdrv_attach_child_common_abort() restores the parent's AioContext. To
do so, the child (which was supposed to be attached, but is now detached
again by this abort handler) is added to the ignore list for the
AioContext changing functions.
However, since we modify a BDS's children list in the BdrvChildClass's
.attach and .detach handlers, the child is already effectively detached
from the parent by this point. We do not need to put it into the ignore
list.
Use this opportunity to clean up the empty line structure: Keep setting
the ignore list, invoking the AioContext function, and freeing the
ignore list in blocks separated by empty lines.
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211111120829.81329-5-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-5-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Now that bdrv_remove_empty_child() no longer removes the child from the
parent's children list but only checks that it is not in such a list, it
is only a wrapper around bdrv_child_free() that checks that the child is
empty and unused. That should apply to all children that we free, so
put those checks into bdrv_child_free() and drop
bdrv_remove_empty_child().
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211111120829.81329-4-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-4-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
The children list is specific to BDS parents. We should not modify it
in the general children modification code, but let BDS parents deal with
it in their .attach() and .detach() methods.
This also has the advantage that a BdrvChild is removed from the
children list before its .bs pointer can become NULL. BDS parents
generally assume that their children's .bs pointer is never NULL, so
this is actually a bug fix.
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20211111120829.81329-3-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211115145409.176785-3-kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Using blockdev-snapshot to append a node as an overlay to itself, or to
any of its parents, causes crashes. Catch the condition and return an
error for these cases instead.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1824363
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20211018134714.48438-1-kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Use bdrv_new_open_driver_opts() instead of complicated bdrv_open().
Among other extra things bdrv_open() also check for white-listed
formats, which we don't want for internal node creation: currently
backup doesn't work when copy-before-write filter is not white-listed.
As well block-stream doesn't work when copy-on-read is not
white-listed.
Fixes: 751cec7a26
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2004812
Reported-by: Yanan Fu
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210920115538.264372-5-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
- options & flags is common pair for open-like functions, let's use it
- add a comment that specifies use of @options
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210920115538.264372-4-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
- use ERRP_GUARD(): function calls error_prepend(), so it must use
ERRP_GUARD(), otherwise error_prepend() would not be called when
passed errp is error_fatal
- drop error propagation, handle return code instead
- for symmetry, do error_prepend() for the second failure
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210920115538.264372-3-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Add version of bdrv_new_open_driver() that supports QDict options.
We'll use it in further commit.
Simply add one more argument to bdrv_new_open_driver() is worse, as
there are too many invocations of bdrv_new_open_driver() to update
then.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210920115538.264372-2-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We must not inactivate child when parent has write permissions on
it.
Calling .bdrv_inactivate() doesn't help: actually only qcow2 has this
handler and it is used to flush caches, not for permission
manipulations.
So, let's simply check cumulative parent permissions before
inactivating the node.
This commit fixes a crash when we do migration during backup: prior to
the commit nothing prevents all nodes inactivation at migration finish
and following backup write to the target crashes on assertion
"assert(!(bs->open_flags & BDRV_O_INACTIVE));" in
bdrv_co_write_req_prepare().
After the commit, we rely on the fact that copy-before-write filter
keeps write permission on target node to be able to write to it. So
inactivation fails and migration fails as expected.
Corresponding test now passes, so, enable it.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210911120027.8063-3-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
As we have attempted before
(https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg06451.html,
"file-posix: Cache lseek result for data regions";
https://lists.nongnu.org/archive/html/qemu-block/2021-02/msg00934.html,
"file-posix: Cache next hole"), this patch seeks to reduce the number of
SEEK_DATA/HOLE operations the file-posix driver has to perform. The
main difference is that this time it is implemented as part of the
general block layer code.
The problem we face is that on some filesystems or in some
circumstances, SEEK_DATA/HOLE is unreasonably slow. Given the
implementation is outside of qemu, there is little we can do about its
performance.
We have already introduced the want_zero parameter to
bdrv_co_block_status() to reduce the number of SEEK_DATA/HOLE calls
unless we really want zero information; but sometimes we do want that
information, because for files that consist largely of zero areas,
special-casing those areas can give large performance boosts. So the
real problem is with files that consist largely of data, so that
inquiring the block status does not gain us much performance, but where
such an inquiry itself takes a lot of time.
To address this, we want to cache data regions. Most of the time, when
bad performance is reported, it is in places where the image is iterated
over from start to end (qemu-img convert or the mirror job), so a simple
yet effective solution is to cache only the current data region.
(Note that only caching data regions but not zero regions means that
returning false information from the cache is not catastrophic: Treating
zeroes as data is fine. While we try to invalidate the cache on zero
writes and discards, such incongruences may still occur when there are
other processes writing to the image.)
We only use the cache for nodes without children (i.e. protocol nodes),
because that is where the problem is: Drivers that rely on block-status
implementations outside of qemu (e.g. SEEK_DATA/HOLE).
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/307
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210812084148.14458-3-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[hreitz: Added `local_file == bs` assertion, as suggested by Vladimir]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Add function to transactionally replace bs inside BdrvChild.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210824083856.17408-2-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Currently, the block driver whitelists are only applied for the system
emulator. All other binaries still give unrestricted access to all block
drivers. There are use cases where this made sense because the main
concern was avoiding customers running VMs on less optimised block
drivers and getting bad performance. Allowing the same image format e.g.
as a target for 'qemu-img convert' is not a problem then.
However, if the concern is the supportability of the driver in general,
either in full or when used read-write, not applying the list driver
whitelist in tools doesn't help - especially since qemu-nbd and
qemu-storage-daemon now give access to more or less the same operations
in block drivers as running a system emulator.
In order to address this, introduce a new configure option that enforces
the driver whitelist in all binaries.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210709164141.254097-1-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
As the BlockReopenQueue can contain nodes in multiple AioContexts, only
one of which may be locked when AIO_WAIT_WHILE() can be called, we can't
let the caller lock the right contexts. Instead, individually lock the
AioContext of a single node when iterating the queue.
Reintroduce bdrv_reopen() as a wrapper for reopening a single node that
drains the node and temporarily drops the AioContext lock for
bdrv_reopen_multiple().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210708114709.206487-4-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Move the code to free a BlockReopenQueue to a separate function.
It will be used in a subsequent patch.
[ kwolf: Also free explicit_options and options, and explicitly
qobject_ref() the value when it continues to be used. This makes
future memory leaks less likely. ]
Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210708114709.206487-3-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Back in commit d9f059aa6c (qemu-img: Deprecate use of -b without -F),
we deprecated the ability to create a file with a backing image that
requires qemu to perform format probing. Qemu can still probe older
files for backwards compatibility, but it is time to finish off the
ability to create such images, due to the potential security risk they
present. Update a couple of iotests affected by the change.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210503213600.569128-3-eblake@redhat.com>
Reviewed-by: Connor Kuehl <ckuehl@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
When the x-blockdev-reopen was added it allowed reconfiguring the
graph by replacing backing files, but changing the 'file' option was
forbidden. Because of this restriction some operations are not
possible, notably inserting and removing block filters.
This patch adds support for replacing the 'file' option. This is
similar to replacing the backing file and the user is likewise
responsible for the correctness of the resulting graph, otherwise this
can lead to data corruption.
Signed-off-by: Alberto Garcia <berto@igalia.com>
[vsementsov: bdrv_reopen_parse_file_or_backing() is modified a lot]
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-9-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
It's used only in bdrv_reopen_commit(). "backing" is covered by the
loop through all children except for case when we removed backing child
during reopen.
Make it more obvious and drop extra boolean field: qdict_del will not
fail if there is no such entry.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-8-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Move supports_backing check of bdrv_reopen_parse_backing to called
(through bdrv_set_backing_noperm()) bdrv_set_file_or_backing_noperm()
function. The check applies to general case, so it's appropriate for
bdrv_set_file_or_backing_noperm().
We have to declare backing support for two test drivers, otherwise new
check fails.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-7-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The logic around finding overlay here is not obvious. Actually it does
two simple things:
1. If new bs is already in backing chain, split from parent bs by
several implicit filters we are done, do nothing.
2. Otherwise, don't try to replace implicit filter.
Let's rewrite this in more obvious way.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-6-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_set_backing_noperm() takes care of it (actual check is in
bdrv_set_file_or_backing_noperm()), so we don't need to check it here.
While being here, improve error message a bit.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-5-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We don't need this check: bdrv_set_backing_noperm() will do it anyway
(actually in bdrv_attach_child_common()).
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-4-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
To be used for reopen in future commit.
Notes:
- It seems OK to update inherits_from if new bs is recursively inherits
from parent bs. Let's just not check for backing_chain_contains, to
support file child of non-filters.
- Simply check child->frozen instead of
bdrv_is_backing_chain_frozen(), as we really interested only in this
one child.
- Role determination of new child is a bit more complex: it remains
the same for backing child, it's obvious for filter driver. But for
non-filter file child let's for now restrict to only replacing
existing child (and keeping its role).
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20210610120537.196183-3-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
