qcow2 used to use bounce buffers for any AIO requests. This does not only imply
unnecessary copying, but also unbounded allocations which should be avoided.
This patch removes bounce buffers from the normal AIO read path, and constrains
them to a constant size for encrypted images.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This distinguishes between harmless leaks and real corruption. Hopefully users
better understand what qemu-img check wants to tell them.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
qcow2_get_cluster_offset() looks up a given virtual disk offset and returns the
offset of the corresponding cluster in the image file. Errors (e.g. L2 table
can't be read) are currenctly indicated by a return value of 0, which is
unfortuately the same as for any unallocated cluster. So in effect we can't
check for errors.
This makes the old return value a by-reference parameter and returns the usual
0/-errno error code.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This patch adds the ability to grow qcow2 images in-place using
bdrv_truncate(). This enables qemu-img resize command support for
qcow2.
Snapshots are not supported and bdrv_truncate() will return -ENOTSUP.
The notion of resizing an image with snapshots could lead to confusion:
users may expect snapshots to remain unchanged, but this is not possible
with the current qcow2 on-disk format where the header.size field is
global instead of per-snapshot. Others may expect snapshots to change
size along with the current image data. I think it is safest to not
support snapshots and perhaps add behavior later if there is a
consensus.
Backing images continue to work. If the image is now larger than its
backing image, zeroes are read when accessing beyond the end of the
backing image.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Format drivers shouldn't need to bother with things like file names, but rather
just get an open BlockDriverState for the underlying protocol. This patch
introduces this behaviour for bdrv_open implementation. For protocols which
need to access the filename to open their file/device/connection/... a new
callback bdrv_file_open is introduced which doesn't get an underlying file
opened.
For now, also some of the more obscure formats use bdrv_file_open because they
open() the file themselves instead of using the block.c functions. They need to
be fixed in later patches.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Checking for return codes < 0 isn't really going to work with unsigned
types. Use signed types instead.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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 <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
It was merely a workaround and the real fix is done now.
This reverts commit ef845c3bf4.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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.
The original bdrv_read would mean that we read some data synchronously and that
we won't be interrupted during this read. The latter assumption is no longer
true with the emulation function which needs to use qemu_aio_poll and therefore
allows the callback of any other concurrent AIO request to be run during the
read. Which in turn means that (meta)data read earlier could have changed and
be invalid now. qcow2 is not prepared to work in this way and it's just scary
how many places there are where other requests could run.
I'm not sure yet where exactly it breaks, but you'll see breakage with virtio
on qcow2 with a backing file. Providing synchronous functions again fixes the
problem for me.
Patchworks-ID: 35437
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This patch increases the maximum qcow2 cluster size to 2 MB. Starting with 128k
clusters, L2 tables span 2 GB or more of virtual disk space, causing 32 bit
truncation and wraparound of signed integers. Therefore some variables need to
use a larger data type.
While being at reviewing data types, change some integers that are used for
array indices to unsigned. In some places they were checked against some upper
limit but not for negative values. This could avoid potential segfaults with
corrupted qcow2 images.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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 15cc923584,
f40d753718,
96555a96d7 and
3990d09adf but the fixes were fragile.
Solution: Avoid the conflict entirely by renaming the functions and the
file. Revert the previous hacks.
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
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
read and a cluster deallocation which cause some overhead. If we simply let the
second request wait until the first one is done, we improve overall performance
with AIO requests (specifially, qcow2/virtio combinations).
This patch maintains a list of in-flight requests that have allocated new
clusters. A second request touching the same cluster is limited so that it
either doesn't touch the allocation of the first request (so it can have a
non-overlapping allocation) or it waits for the first request to complete.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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
names, but they are not nice. This patch adds a qcow2_ prefix to all of the
global functions in qcow2.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
qcow2-snapshot.c contains the code related to snapshotting.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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
two-level lookup tables.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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
the split qcow2 modules.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
