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# Date Author Comment
1d36e3aa 01/26/2010 10:59 pm Kevin Wolf

qcow2: Fix error handling in qcow_save_vmstate

Don't assume success but pass the bdrv_pwrite return value on.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

148da7ea 01/26/2010 10:59 pm Kevin Wolf

qcow2: Return 0/-errno in qcow2_alloc_cluster_offset

Returning 0/-errno allows it to distingush different errors classes. The
cluster offset of newly allocated clusters is now returned in the QCowL2Meta
struct.

Signed-off-by: Kevin Wolf <>...

756e6736 01/14/2010 01:14 am Kevin Wolf

block: Add bdrv_change_backing_file

Introduce the functions needed to change the backing file of an image. The
function is implemented for qcow2.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

f8012c13 01/14/2010 01:14 am Kevin Wolf

qcow/qcow2: implement bdrv_aio_flush

Now that we do not have to flush the backing device anymore implementing
the bdrv_aio_flush method for image formats is trivial.

[hch: forward ported to qemu mainline from a product tree]

Signed-off-by: Kevin Wolf <>...

e1c7f0e3 12/03/2009 07:45 pm Kevin Wolf

qcow2: Store exact backing format length

Currently qcow2 unnecessarily rounds up the length of the backing format string
to the next multiple of 8. At the same time, the array in BlockDriverState can
only hold 15 characters, so in effect backing formats with 9 characters or more...

d191d12d 11/09/2009 04:43 pm Stefan Weil

qcow2: Allow qcow2 disk images with size zero

Images with disk size 0 may be used for
VM snapshots, but not to save normal block data.

It is possible to create such images using
qemu-img, but opening them later fails.

So even "qemu-img info image.qcow2" is not...

72ecf02d 10/27/2009 07:28 pm Kevin Wolf

Revert "qcow2: Bring synchronous read/write back to life"

It was merely a workaround and the real fix is done now.
This reverts commit ef845c3bf421290153154635dc18eaa677cecb43.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

ef845c3b 10/15/2009 05:32 pm Kevin Wolf

qcow2: Bring synchronous read/write back to life

When the synchronous read and write functions were dropped, they were replaced
by generic emulation functions. Unfortunately, these emulation functions don't
provide the same semantics as the original functions did....

72cf2d4f 09/12/2009 10:36 am Blue Swirl

Fix sys-queue.h conflict for good

Problem: Our file sys-queue.h is a copy of the BSD file, but there are
some additions and it's not entirely compatible. Because of that, there have
been conflicts with system headers on BSD systems. Some hacks have been
introduced in the commits 15cc9235840a22c289edbe064a9b3c19c5f49896,...

ea80b906 09/10/2009 01:31 am Kevin Wolf

qcow2: Fix metadata preallocation

The wrong version of the preallocation patch has been applied, so this is the
remaining diff.

We can't use truncate to grow the image file to the right size because we don't
know if metadata has been written after the last data cluster. In this case...

f214978a 09/10/2009 01:31 am Kevin Wolf

qcow2: Order concurrent AIO requests on the same unallocated cluster

When two AIO requests write to the same cluster, and this cluster is
unallocated, currently both requests allocate a new cluster and the second one
merges the first one when it is completed. This means an cluster allocation, a...

2000cbc5 08/29/2009 04:37 pm Blue Swirl

Fix gcc 3 warning about uninitialized variable

If nb_sectors is 0, cluster_offset will not be initialized.

Signed-off-by: Blue Swirl <>

a35e1c17 08/28/2009 04:30 am Kevin Wolf

qcow2: Metadata preallocation

This introduces a qemu-img create option for qcow2 which allows the metadata to
be preallocated, i.e. clusters are reserved in the refcount table and L1/L2
tables, but no data is written to them. Metadata is quite small, so this...

45566e9c 07/16/2009 04:28 pm Christoph Hellwig

replace bdrv_{get, put}_buffer with bdrv_{load, save}_vmstate

The VM state offset is a concept internal to the image format. Replace
the old bdrv_{get,put}_buffer method that require an index into the
image file that is constructed from the VM state offset and an offset...

3f6a3ee5 07/10/2009 09:44 pm Kevin Wolf

qcow2: Fix L1 table memory allocation

Contrary to what one could expect, the size of L1 tables is not cluster
aligned. So as we're writing whole sectors now instead of single entries,
we need to ensure that the L1 table in memory is large enough; otherwise...

0aa217e4 07/10/2009 12:06 am Kevin Wolf

qcow2: Make cache=writethrough default

The performance of qcow2 has improved meanwhile, so we don't need to
special-case it any more. Switch the default to write-through caching
like all other block drivers.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

14899cdf 06/29/2009 04:52 pm Filip Navara

Fix QCOW2 debugging code to compile again

Updated to use C99 comments.

Signed-off-by: Filip Navara <>
Signed-off-by: Anthony Liguori <>

9ccb258e 06/16/2009 11:18 pm Kevin Wolf

qcow2: Change default cluster size to 64k

Larger cluster sizes mean less metadata. This has been discussion a few times,
let's do it now. This turns 64k clusters on by default for new images.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

f7d0fe02 06/16/2009 11:18 pm Kevin Wolf

qcow2: Split out refcount handling

qcow2-refcount.c contains all functions which are related to cluster
allocation and management in the image file. A large part of this is the
reference counting of these clusters.

Also a header file qcow2.h is introduced which will contain the interface of...

45aba42f 06/16/2009 11:18 pm Kevin Wolf

qcow2: Split out guest cluster functions

qcow2-cluster.c contains all functions related to the management of guest
clusters, i.e. what the guest sees on its virtual disk. This code is about
mapping these guest clusters to host clusters in the image file using the...

c142442b 06/16/2009 11:18 pm Kevin Wolf

qcow2: Split out snapshot functions

qcow2-snapshot.c contains the code related to snapshotting.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

ed6ccf0f 06/16/2009 11:18 pm Kevin Wolf

qcow2: Rename global functions

The qcow2 source is now split into several more manageable files. During the
conversion quite some functions that were static before needed to be changed to
be global to make the source compile again.

We were lucky enough not to get name conflicts with these additional global...

db08adf5 06/06/2009 06:38 pm Kevin Wolf

qemu-img: Print available options with -o ?

This patch adds a small help text to each of the options in the block drivers
which can be displayed by using qemu-img create -f fmt -o ?

Signed-off-by: Kevin Wolf <>

c16b5a2c 05/27/2009 05:46 pm Christoph Hellwig

fully split aio_pool from BlockDriver

Now that we have a separate aio pool structure we can remove those
aio pool details from BlockDriver.

Every driver supporting AIO now needs to declare a static AIOPool
with the aiocb size and the cancellation method. This cleans up the...

a980c98c 05/27/2009 05:45 pm Kevin Wolf

qcow2: Update multiple refcounts at once

Don't write each single changed refcount block entry to the disk after it is
written, but update all entries of the block and write all of them at once.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

44ff42de 05/27/2009 05:45 pm Kevin Wolf

qcow2: Refactor update_refcount

This is a preparation patch with no functional changes. It moves the allocation
of new refcounts block to a new function and makes update_cluster_refcount (for
one cluster) call update_refcount (for multiple clusters) instead the other way...

ade40677 05/27/2009 05:45 pm Kevin Wolf

qcow/qcow2: Drop synchronous qcow_write()

There is only one (internal) user left and it can be switched to the normal
emulation provided in block.c

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

73c632ed 05/22/2009 06:50 pm Kevin Wolf

qcow2: Allow different cluster sizes

Add an option to specify the cluster size of a newly created qcow2 image.
Default is 4k which is the same value that was hard-coded before.

Signed-off-by: Kevin Wolf <>
Signed-off-by: Anthony Liguori <>

0e7e1989 05/22/2009 06:50 pm Kevin Wolf

Convert all block drivers to new bdrv_create

Now we can make use of the newly introduced option structures. Instead of
having bdrv_create carry more and more parameters (which are format specific in
most cases), just pass a option structure as defined by the driver itself....

eb0b64f7 05/21/2009 04:40 am malc

Do not attempt to allocate sn_tab when there are no snapshots

This was caught by a7d27b536ffc0773028a90f14580552c0c3ddb2a which
aborted on this attempt, thanks to Alex Ivanov for report.

Signed-off-by: malc <>

019d6b8f 05/15/2009 12:13 am Anthony Liguori

Move block drivers into their own directory

Signed-off-by: Anthony Liguori <>