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>
I used the following command to enable debugging:
perl -p -i -e 's/^\/\/#define DEBUG/#define DEBUG/g' * */* */*/*
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
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
write would access memory after the end of the L1 table.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
The really time consuming part of snapshotting is to adjust the reference count
of all clusters. Currently after each adjusted cluster the refcount block is
written to disk.
Don't write each single byte immediately to disk but cache all writes to the
refcount block and write them out once we're done with the block.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
When updating the refcount blocks in update_refcount(), write complete sectors
instead of updating single entries.
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-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>
