Parts of the block layer treat BDS.backing_file as if it were whatever
the image header says (i.e., if it is a relative path, it is relative to
the overlay), other parts treat it like a cache for
bs->backing->bs->filename (relative paths are relative to the CWD).
Considering bs->backing->bs->filename exists, let us make it mean the
former.
Among other things, this now allows the user to specify a base when
using qemu-img to commit an image file in a directory that is not the
CWD (assuming, everything uses relative filenames).
Before this patch:
$ ./qemu-img create -f qcow2 foo/bot.qcow2 1M
$ ./qemu-img create -f qcow2 -b bot.qcow2 foo/mid.qcow2
$ ./qemu-img create -f qcow2 -b mid.qcow2 foo/top.qcow2
$ ./qemu-img commit -b mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find '[...]/foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'
After this patch:
$ ./qemu-img commit -b mid.qcow2 foo/top.qcow2
Image committed.
$ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2
Image committed.
With this change, bdrv_find_backing_image() must look at whether the
user has overridden a BDS's backing file. If so, it can no longer use
bs->backing_file, but must instead compare the given filename against
the backing node's filename directly.
Note that this changes the QAPI output for a node's backing_file. We
had very inconsistent output there (sometimes what the image header
said, sometimes the actual filename of the backing image). This
inconsistent output was effectively useless, so we have to decide one
way or the other. Considering that bs->backing_file usually at runtime
contained the path to the image relative to qemu's CWD (or absolute),
this patch changes QAPI's backing_file to always report the
bs->backing->bs->filename from now on. If you want to receive the image
header information, you have to refer to full-backing-filename.
This necessitates a change to iotest 228. The interesting information
it really wanted is the image header, and it can get that now, but it
has to use full-backing-filename instead of backing_file. Because of
this patch's changes to bs->backing_file's behavior, we also need some
reference output changes.
Along with the changes to bs->backing_file, stop updating
BDS.backing_format in bdrv_backing_attach() as well. This way,
ImageInfo's backing-filename and backing-filename-format fields will
represent what the image header says and nothing else.
iotest 245 changes in behavior: With the backing node no longer
overriding the parent node's backing_file string, you can now omit the
@backing option when reopening a node with neither a default nor a
current backing file even if it used to have a backing node at some
point.
273 also changes: The base image is opened without a format layer, so
ImageInfo.backing-filename-format used to report "file" for the base
image's overlay after blockdev-snapshot. However, the image header
never says "file" anywhere, so it now reports $IMGFMT.
Signed-off-by: Max Reitz <mreitz@redhat.com>
With bdrv_filter_bs(), we can easily handle this default filter behavior
in bdrv_co_block_status().
blkdebug wants to have an additional assertion, so it keeps its own
implementation, except bdrv_co_block_status_from_file() needs to be
inlined there.
Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
This includes some permission limiting (for example, we only need to
take the RESIZE permission if the base is smaller than the top).
Signed-off-by: Max Reitz <mreitz@redhat.com>
This includes some permission limiting (for example, we only need to
take the RESIZE permission for active commits where the base is smaller
than the top).
base_overlay is introduced so we can query bdrv_is_allocated_above() on
it - we cannot do that with base itself, because a filter's block_status
is the same as its child node, so if there are filters on base,
bdrv_is_allocated_above() on base would return information including
base.
Use this opportunity to rename qmp_drive_mirror()'s "source" BDS to
"target_backing_bs", because that is what it really refers to.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
query-block, query-named-block-nodes, and query-blockstats now return
any filtered child under "backing", not just bs->backing or COW
children. This is so that filters do not interrupt the reported backing
chain. This changes the output for iotest 184, as the throttled node
now appears as a backing child.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
It makes no sense to report the block stats of a purely metadata-storing
child in query-blockstats. So if the primary child does not have any
data, try to find a unique data-storing child.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
It is trivial, so we might as well do it.
Remove _filter_actual_image_size from iotest 184, so we get to see the
result in its reference output.
Signed-off-by: Max Reitz <mreitz@redhat.com>
If the top node's driver does not provide snapshot functionality and we
want to fall back to a node down the chain, we need to snapshot all
non-COW children. For simplicity's sake, just do not fall back if there
is more than one such child. Furthermore, we really only can fall back
to bs->file and bs->backing, because bdrv_snapshot_goto() has to modify
the child link (notably, set it to NULL).
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
If a node whose driver does not provide VM state functions has a
metadata child, the VM state should probably go there; if it is a
filter, the VM state should probably go there. It follows that we
should generally go down to the primary child.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Instead of looking at just bs->file and bs->backing, we should look at
all children that could end up receiving forwarded requests.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Before HEAD^, we needed this because bdrv_co_flush() by itself would
only flush bs->file. With HEAD^, bdrv_co_flush() will flush all
children on which a WRITE or WRITE_UNCHANGED permission has been taken.
Thus, vmdk no longer needs to do it itself.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
If the driver does not support .bdrv_co_flush() so bdrv_co_flush()
itself has to flush the children of the given node, it should not flush
just bs->file->bs, but in fact all children that might have been written
to (judging from the permissions taken on them).
This is a bug fix for qcow2 images with an external data file, as they
so far did not flush that data_file node.
In any case, the BLKDBG_EVENT() should be emitted on the primary child,
because that is where a blkdebug node would be if there is any.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
The condition modified here is not about potentially filtered children,
but only about COW sources (i.e. traditional backing files).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Because of the (not so recent anymore) changes that make the stream job
independent of the base node and instead track the node above it, we
have to split that "bottom" node into two cases: The bottom COW node,
and the node directly above the base node (which may be an R/W filter
or the bottom COW node).
Signed-off-by: Max Reitz <mreitz@redhat.com>
Places that use patterns like
if (bs->drv->is_filter && bs->file) {
... something about bs->file->bs ...
}
should be
BlockDriverState *filtered = bdrv_filter_bs(bs);
if (filtered) {
... something about @filtered ...
}
instead.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
The original purpose of bdrv_is_encrypted() was to inquire whether a BDS
can be used without the user entering a password or not. It has not
been used for that purpose for quite some time.
Actually, it is not even fit for that purpose, because to answer that
question, it would have recursively query all of the given node's
children.
So now we have to decide in which direction we want to fix
bdrv_is_encrypted(): Recursively query all children, or drop it and just
use bs->encrypted to get the current node's status?
Nowadays, its only purpose is to report through bdrv_query_image_info()
whether the given image is encrypted or not. For this purpose, it is
probably more interesting to see whether a given node itself is
encrypted or not (otherwise, a management application cannot discern for
certain which nodes are really encrypted and which just have encrypted
children).
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
In preparation of using multiple IRQ (thus multiple eventfds)
make BDRVNVMeState::irq_notifier an array (for now of a single
element, the admin queue notifier).
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-16-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
As we want to do per-queue polling, extract the nvme_poll_queue()
method which operates on a single queue.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-15-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
nvme_create_queue_pair() doesn't require BlockDriverState anymore.
Replace it by BDRVNVMeState and AioContext to simplify.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-14-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
BDRV_POLL_WHILE() is defined as:
#define BDRV_POLL_WHILE(bs, cond) ({ \
BlockDriverState *bs_ = (bs); \
AIO_WAIT_WHILE(bdrv_get_aio_context(bs_), \
cond); })
As we will remove the BlockDriverState use in the next commit,
start by using the exploded version of BDRV_POLL_WHILE().
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-13-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
nvme_init_queue() doesn't require BlockDriverState anymore.
Replace it by BDRVNVMeState to simplify.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-12-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
qemu_try_blockalign() is a generic API that call back to the
block driver to return its page alignment. As we call from
within the very same driver, we already know to page alignment
stored in our state. Remove indirections and use the value from
BDRVNVMeState.
This change is required to later remove the BlockDriverState
argument, to make nvme_init_queue() per hardware, and not per
block driver.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-11-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
In the next commit we'll get rid of qemu_try_blockalign().
To ease review, first replace qemu_try_blockalign0() by explicit
calls to qemu_try_blockalign() and memset().
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-10-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We allocate an unique chunk of memory then use it for two
different structures. By using an union, we make it clear
the data is overlapping (and we can remove the casts).
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-9-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
We are going to modify the code in the next commit. Renaming
the 'resp' variable to 'id' first makes the next commit easier
to review. No logical changes.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-8-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Rearrange nvme_add_io_queue() by using a common error path.
This will be proven useful in few commits where we add IRQ
notification to the IO queues.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-7-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Do not use the same error message for different failures.
Display a different error whether it is the CQ or the SQ.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-6-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Use definitions instead of '0' or '1' indexes. Also this will
be useful when using multi-queues later.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-5-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
As nvme_create_queue_pair() is allowed to fail, replace the
alloc() calls by try_alloc() to avoid aborting QEMU.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-4-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Avoid further processing if TRACE_NVME_SUBMIT_COMMAND_RAW is
not enabled. This is an untested intend of performance optimization.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-3-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Use self-explicit SCALE_MS definition instead of magic value.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200821195359.1285345-2-philmd@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This makes nbd's connection_co yield during reconnects, so that
reconnect doesn't block the main thread. This is very important in
case of an unavailable nbd server host: connect() call may take a long
time, blocking the main thread (and due to reconnect, it will hang
again and again with small gaps of working time during pauses between
connection attempts).
Realization notes:
- We don't want to implement non-blocking connect() over non-blocking
socket, because getaddrinfo() doesn't have portable non-blocking
realization anyway, so let's just use a thread for both getaddrinfo()
and connect().
- We can't use qio_channel_socket_connect_async (which behaves
similarly and starts a thread to execute connect() call), as it's relying
on someone iterating main loop (g_main_loop_run() or something like
this), which is not always the case.
- We can't use thread_pool_submit_co API, as thread pool waits for all
threads to finish (but we don't want to wait for blocking reconnect
attempt on shutdown.
So, we just create the thread by hand. Some additional difficulties
are:
- We want our connect to avoid blocking drained sections and aio context
switches. To achieve this, we make it possible to "cancel" synchronous
wait for the connect (which is a coroutine yield actually), still,
the thread continues in background, and if successful, its result may be
reused on next reconnect attempt.
- We don't want to wait for reconnect on shutdown, so there is
CONNECT_THREAD_RUNNING_DETACHED thread state, which means that the block
layer is no longer interested in a result, and thread should close new
connected socket on finish and free the state.
How to reproduce the bug, fixed with this commit:
1. Create an image on node1:
qemu-img create -f qcow2 xx 100M
2. Start NBD server on node1:
qemu-nbd xx
3. Start vm with second nbd disk on node2, like this:
./x86_64-softmmu/qemu-system-x86_64 -nodefaults -drive \
file=/work/images/cent7.qcow2 -drive file=nbd+tcp://192.168.100.2 \
-vnc :0 -qmp stdio -m 2G -enable-kvm -vga std
4. Access the vm through vnc (or some other way?), and check that NBD
drive works:
dd if=/dev/sdb of=/dev/null bs=1M count=10
- the command should succeed.
5. Now, let's trigger nbd-reconnect loop in Qemu process. For this:
5.1 Kill NBD server on node1
5.2 run "dd if=/dev/sdb of=/dev/null bs=1M count=10" in the guest
again. The command should fail and a lot of error messages about
failing disk may appear as well.
Now NBD client driver in Qemu tries to reconnect.
Still, VM works well.
6. Make node1 unavailable on NBD port, so connect() from node2 will
last for a long time:
On node1 (Note, that 10809 is just a default NBD port):
sudo iptables -A INPUT -p tcp --dport 10809 -j DROP
After some time the guest hangs, and you may check in gdb that Qemu
hangs in connect() call, issued from the main thread. This is the
BUG.
7. Don't forget to drop iptables rule from your node1:
sudo iptables -D INPUT -p tcp --dport 10809 -j DROP
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200812145237.4396-1-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: minor wording and formatting tweaks]
Signed-off-by: Eric Blake <eblake@redhat.com>
The NVM Express specification generally uses 'zeroes' and not 'zeros',
so let us align with it.
Cc: Fam Zheng <fam@euphon.net>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Add missing fields in the Identify Controller and Identify Namespace
data structures to bring them in line with NVMe v1.3.
This also adds data structures and defines for SGL support which
requires a couple of trivial changes to the nvme block driver as well.
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Acked-by: Fam Zheng <fam@euphon.net>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Message-Id: <20200706061303.246057-2-its@irrelevant.dk>
Remove superfluous breaks, as there is a "return" before them.
Signed-off-by: Liao Pingfang <liao.pingfang@zte.com.cn>
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1594631107-36574-1-git-send-email-wang.yi59@zte.com.cn>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
The qcow2 driver needs the zlib dependency. While emulators
provided it through the migration code, this is not true of
the tools. Move the dependency from the qcow1 rule directly
into block_ss so that it is included unconditionally.
Fixes build with --disable-qcow1.
Reported-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move typedef closer to the type check macros, to make it easier
to convert the code to OBJECT_DEFINE_TYPE() in the future.
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Tested-By: Roman Bolshakov <r.bolshakov@yadro.com>
Message-Id: <20200825192110.3528606-17-ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This function is only used by qcow2_expand_zero_clusters() to
downgrade a qcow2 image to a previous version. This would require
transforming all extended L2 entries into normal L2 entries but this
is not a simple task and there are no plans to implement this at the
moment.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <15e65112b4144381b4d8c0bdf8fb76b0d813e3d1.1594396418.git.berto@igalia.com>
[mreitz: Fixed comment style]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Traditional qcow2 images don't allow preallocation if a backing file
is set. This is because once a cluster is allocated there is no way to
tell that its data should be read from the backing file.
Extended L2 entries have individual allocation bits for each
subcluster, and therefore it is perfectly possible to have an
allocated cluster with all its subclusters unallocated.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <6d5b0f38e7dc5f2f31d8cab1cb92044e9909aece.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Now that the implementation of subclusters is complete we can finally
add the necessary options to create and read images with this feature,
which we call "extended L2 entries".
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <6476caaa73216bd05b7bb2d504a20415e1665176.1594396418.git.berto@igalia.com>
[mreitz: %s/5\.1/5.2/; fixed 302's and 303's reference output]
Signed-off-by: Max Reitz <mreitz@redhat.com>
This field allows us to indicate that the L2 metadata update does not
come from a write request with actual data but from a preallocation
request.
For traditional images this does not make any difference, but for
images with extended L2 entries this means that the clusters are
allocated normally in the L2 table but individual subclusters are
marked as unallocated.
This will allow preallocating images that have a backing file.
There is one special case: when we resize an existing image we can
also request that the new clusters are preallocated. If the image
already had a backing file then we have to hide any possible stale
data and zero out the new clusters (see commit 955c7d6687 for more
details).
In this case the subclusters cannot be left as unallocated so the L2
bitmap must be updated.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <960d4c444a4f5a870e2b47e5da322a73cd9a2f5a.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Extended L2 entries are bigger than normal L2 entries so this has an
impact on the amount of metadata needed for a qcow2 file.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <7efae2efd5e36b42d2570743a12576d68ce53685.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
