Commit Graph

173 Commits

Author SHA1 Message Date
Max Reitz
32b6444d23 qcow2-cluster: Expand zero clusters
Add functionality for expanding zero clusters. This is necessary for
downgrading the image version to one without zero cluster support.

For non-backed images, this function may also just discard zero clusters
instead of truly expanding them.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12 10:12:46 +02:00
Max Reitz
e7108feaac qcow2-cache: Empty cache
Add a function for emptying a cache, i.e., flushing it and marking all
elements invalid.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12 10:12:46 +02:00
Kevin Wolf
1ebf561c11 qcow2: Discard VM state in active L1 after creating snapshot
During savevm, the VM state is written to the active L1 of the image and
then a snapshot is taken. After that, the VM state isn't needed any more
in the active L1 and should be discarded. This is implemented by this
patch.

The impact of not discarding the VM state is that a snapshot can never
become smaller than any previous snapshot (because it would be padded
with old VM state), and more importantly that future savevm operations
cause unnecessary COWs (with associated flushes), which makes subsequent
snapshots much slower.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:46 +02:00
Kevin Wolf
670df5e3b4 qcow2: Pass discard type to qcow2_discard_clusters()
The function will be used internally instead of only being called for
guest discard requests.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:46 +02:00
Max Reitz
e23e400ec6 qcow2-refcount: Repair OFLAG_COPIED errors
Since the OFLAG_COPIED checks are now executed after the refcounts have
been repaired (if repairing), it is safe to assume that they are correct
but the OFLAG_COPIED flag may be not. Therefore, if its value differs
from what it should be (considering the according refcount), that
discrepancy can be repaired by correctly setting (or clearing that flag.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30 15:48:44 +02:00
Max Reitz
a40f1c2add qcow2: Metadata overlap checks
Two new functions are added; the first one checks a given range in the
image file for overlaps with metadata (main header, L1 tables, L2
tables, refcount table and blocks).

The second one should be used immediately before writing to the image
file as it calls the first function and, upon collision, marks the
image as corrupt and makes the BDS unusable, thereby preventing
further access.

Both functions take a bitmask argument specifying the structures which
should be checked for overlaps, making it possible to also check
metadata writes against colliding with other structures.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30 15:48:43 +02:00
Max Reitz
69c9872653 qcow2: Add corrupt bit
This adds an incompatible bit indicating corruption to qcow2. Any image
with this bit set may not be written to unless for repairing (and
subsequently clearing the bit if the repair has been successful).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30 15:48:43 +02:00
Peter Maydell
127c84e1a5 block/qcow2.h: Avoid "1LL << 63" (shifts into sign bit)
The expression "1LL << 63" tries to shift the 1 into the sign bit of a
'long long', which provokes a clang sanitizer warning:

runtime error: left shift of 1 by 63 places cannot be represented in type 'long long'

Use "1ULL << 63" as the definition of QCOW_OFLAG_COPIED instead
to avoid this. For consistency, we also update the other QCOW_OFLAG
definitions to use the ULL suffix rather than LL, though only the
shift by 63 is undefined behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30 15:28:52 +02:00
Kevin Wolf
64aa99d3e0 qcow2: Use dashes instead of underscores in options
This is what QMP wants to use. The options haven't been enabled in any
release yet, so we're still free to change them.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2013-07-26 21:59:56 +02:00
Kevin Wolf
0b919fae31 qcow2: Batch discards
This optimises the discard operation for freed clusters by batching
discard requests (both snapshot deletion and bdrv_discard end up
updating the refcounts cluster by cluster).

Note that we don't discard asynchronously, but keep s->lock held. This
is to avoid that a freed cluster is reallocated and written to while the
discard is still in flight.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-06-24 10:25:17 +02:00
Kevin Wolf
67af674e47 qcow2: Options to enable discard for freed clusters
Deleted snapshots are discarded in the image file by default, discard
requests take their default from the -drive discard=... option and other
places that free clusters must always be enabled explicitly.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-06-24 10:25:17 +02:00
Kevin Wolf
6cfcb9b8b9 qcow2: Add refcount update reason to all callers
This adds a refcount update reason to all callers of update_refcounts(),
so that a follow-up patch can use this information to decide whether
clusters that reach a refcount of 0 should be discarded in the image
file.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-06-24 10:25:17 +02:00
Kevin Wolf
2cf7cfa1cd qcow2: Catch some L1 table index overflows
This catches the situation that is described in the bug report at
https://bugs.launchpad.net/qemu/+bug/865518 and goes like this:

    $ qemu-img create -f qcow2 huge.qcow2 $((1024*1024))T
    Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976 encryption=off cluster_size=65536 lazy_refcounts=off
    $ qemu-io /tmp/huge.qcow2 -c "write $((1024*1024*1024*1024*1024*1024 - 1024)) 512"
    Segmentation fault

With this patch applied the segfault will be avoided, however the case
will still fail, though gracefully:

    $ qemu-img create -f qcow2 /tmp/huge.qcow2 $((1024*1024))T
    Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976 encryption=off cluster_size=65536 lazy_refcounts=off
    qemu-img: The image size is too large for file format 'qcow2'

Note that even long before these overflow checks kick in, you get
insanely high memory usage (up to INT_MAX * sizeof(uint64_t) = 16 GB for
the L1 table), so with somewhat smaller image sizes you'll probably see
qemu aborting for a failed g_malloc().

If you need huge image sizes, you should increase the cluster size to
the maximum of 2 MB in order to get higher limits.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-05-14 16:44:33 +02:00
Aurelien Jarno
753d9b82c5 aes: move aes.h from include/block to include/qemu
Move aes.h from include/block to include/qemu to show it can be reused
by other subsystems.

Cc: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
2013-04-13 13:51:57 +02:00
Kevin Wolf
88c6588c51 qcow2: Allow requests with multiple l2metas
Instead of expecting a single l2meta, have a list of them. This allows
to still have a single I/O request for the guest data, even though
multiple l2meta may be needed in order to describe both a COW overwrite
and a new cluster allocation (typical sequential write case).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:44 +01:00
Kevin Wolf
c37f4cd71d qcow2: Finalise interface of handle_alloc()
The interface works completely on a byte granularity now and duplicated
parameters are removed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:43 +01:00
Kevin Wolf
3b8e2e260c qcow2: handle_alloc(): Get rid of keep_clusters parameter
handle_alloc() is now called with the offset at which the actual new
allocation starts instead of the offset at which the whole write request
starts, part of which may already be processed.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:43 +01:00
Kevin Wolf
65eb2e35c0 qcow2: Change handle_dependency to byte granularity
This is a more precise description of what really constitutes a
dependency. The behaviour doesn't change at this point because the COW
area of the old request is still aligned to cluster boundaries and
therefore an overlap is detected wheneven the requests touch any part of
the same cluster.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:43 +01:00
Kevin Wolf
17a71e5823 qcow2: Handle dependencies earlier
Handling overlapping allocations isn't just a detail of cluster
allocation. It is rather one of three ways to get the host cluster
offset for a write request:

1. If a request overlaps an in-flight allocations, the cluster offset
   can be taken from there (this is what handle_dependencies will evolve
   into) or the request must just wait until the allocation has
   completed. Accessing the L2 is not valid in this case, it has
   outdated information.

2. Outside overlapping areas, check the clusters that can be written to
   as they are, with no COW involved.

3. If a COW is required, allocate new clusters

Changing the code to reflect this doesn't change the behaviour because
overlaps cannot exist for clusters that are kept in step 2. It does
however make it easier for later patches to work on clusters that belong
to an allocation that is still in flight.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-28 11:52:42 +01:00
Kevin Wolf
acdfb480ba qcow2: Fix segfault in qcow2_invalidate_cache
Need to pass an options QDict to qcow2_open() now. This fixes a segfault
on the migration target with qcow2.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-03-19 11:48:36 +01:00
Kevin Wolf
74c4510a3c qcow2: Allow lazy refcounts to be enabled on the command line
qcow2 images now accept a boolean lazy_refcounts options. Use it like
this:

  -drive file=test.qcow2,lazy_refcounts=on

If the option is specified on the command line, it overrides the default
specified by the qcow2 header flags that were set when creating the
image.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-03-15 16:07:49 +01:00
Paolo Bonzini
737e150e89 block: move include files to include/block/
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2012-12-19 08:31:31 +01:00
Kevin Wolf
280d373579 qcow2: Enable dirty flag in qcow2_alloc_cluster_link_l2
This is closer to where the dirty flag is really needed, and it avoids
having checks for special cases related to cluster allocation directly
in the writev loop.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-12-13 15:37:59 +01:00
Kevin Wolf
f50f88b9fe qcow2: Allocate l2meta only for cluster allocations
Even for writes to already allocated clusters, an l2meta is allocated,
though it stays effectively unused. After this patch, only allocating
requests still have one. Each l2meta now describes an in-flight request
that writes to clusters that are not yet hooked up in the L2 table.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-12-13 15:37:59 +01:00
Kevin Wolf
060bee8943 qcow2: Drop l2meta.cluster_offset
There's no real reason to have an l2meta for normal requests that don't
allocate anything. Before we can get rid of it, we must return the host
cluster offset in a different way.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-12-13 15:37:59 +01:00
Kevin Wolf
593fb83cac qcow2: Introduce Qcow2COWRegion
This makes it easier to address the areas for which a COW must be
performed. As a nice side effect, the COW code in
qcow2_alloc_cluster_link_l2 becomes really trivial.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-12-13 15:37:59 +01:00
Kevin Wolf
1d3afd649b qcow2: Round QCowL2Meta.offset down to cluster boundary
The offset within the cluster is already present as n_start and this is
what the code uses. QCowL2Meta.offset is only needed at a cluster
granularity.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-12-13 15:37:59 +01:00
Stefan Hajnoczi
bfe8043e92 qcow2: implement lazy refcounts
Lazy refcounts is a performance optimization for qcow2 that postpones
refcount metadata updates and instead marks the image dirty.  In the
case of crash or power failure the image will be left in a dirty state
and repaired next time it is opened.

Reducing metadata I/O is important for cache=writethrough and
cache=directsync because these modes guarantee that data is on disk
after each write (hence we cannot take advantage of caching updates in
RAM).  Refcount metadata is not needed for guest->file block address
translation and therefore does not need to be on-disk at the time of
write completion - this is the motivation behind the lazy refcount
optimization.

The lazy refcount optimization must be enabled at image creation time:

  qemu-img create -f qcow2 -o compat=1.1,lazy_refcounts=on a.qcow2 10G
  qemu-system-x86_64 -drive if=virtio,file=a.qcow2,cache=writethrough

Update qemu-iotests 031 and 036 since the extension header size changes
when we add feature bit table entries.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-08-06 22:39:14 +02:00
Stefan Hajnoczi
c61d0004bc qcow2: introduce dirty bit
This patch adds an incompatible feature bit to mark images that have not
been closed cleanly.  When a dirty image file is opened a consistency
check and repair is performed.

Update qemu-iotests 031 and 036 since the extension header size changes
when we add feature bit table entries.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-08-06 22:39:14 +02:00
Paolo Bonzini
6af4e9ead4 qcow2: always operate caches in writeback mode
Writethrough does not need special-casing anymore in the qcow2 caches.
The block layer adds flushes after every guest-initiated data write,
and these will also flush the qcow2 caches to the OS.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-06-15 14:03:43 +02:00
Kevin Wolf
166acf546f qcow2: Support for fixing refcount inconsistencies
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-06-15 14:03:42 +02:00
Kevin Wolf
621f058940 qcow2: Zero write support
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:30 +02:00
Kevin Wolf
cfcc4c62ff qcow2: Support for feature table header extension
Instead of printing an ugly bitmask, qemu can now print a more helpful
string even for yet unknown features.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:29 +02:00
Kevin Wolf
6377af48b0 qcow2: Support reading zero clusters
This adds support for reading zero clusters in version 3 images.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:29 +02:00
Kevin Wolf
6744cbab8c qcow2: Version 3 images
This adds the basic infrastructure to qcow2 to handle version 3 images.
It includes code to create v3 images, allow header updates for v3 images
and checks feature bits.

It still misses support for zero clusters, so this is not a fully
compliant implementation of v3 yet.

The default for creating new images stays at v2 for now.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:29 +02:00
Kevin Wolf
76dc9e0c8f qcow2: Ignore reserved bits in refcount table entries
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:29 +02:00
Kevin Wolf
68d000a390 qcow2: Ignore reserved bits in get_cluster_offset
With this change, reading from a qcow2 image ignores all reserved bits
that are set in an L1 or L2 table entry.

Now get_cluster_offset() assigns *cluster_offset only the offset without
any other flags. The cluster type is not longer encoded in the offset,
but a positive return value in case of success.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:27 +02:00
Kevin Wolf
90b277593d qcow2: Save disk size in snapshot header
This allows that different snapshots of an image can have different
sizes, which is a requirement for enabling image resizing even with
images that have internal snapshots.

We don't do the actual support for it now, but make sure that the
additional field is present and not completely ignored in all version 3
images. When trying to load a snapshot of different size, it returns
an error.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:27 +02:00
Kevin Wolf
250196f19c qcow2: Reduce number of I/O requests
If the first part of a write request is allocated, but the second isn't
and it can be allocated so that the resulting area is contiguous, handle
it at once. This is a common case for sequential writes.

After this patch, alloc_cluster_offset() only checks if the clusters are
already allocated or how many new clusters can be allocated contigouosly.
The actual cluster allocation is split off into a new function
do_alloc_cluster_offset().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-03-12 15:14:07 +01:00
Kevin Wolf
256900b16b qcow2: Add qcow2_alloc_clusters_at()
This function allows to allocate clusters at a given offset in the image
file. This is useful if you want to allocate the second part of an area
that must be contiguous.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-03-12 15:14:07 +01:00
Kevin Wolf
75bab85ca0 qcow2: Keep unknown header extension when rewriting header
If we want header extensions to work as compatible extensions, we can't
destroy yet unknown header extensions when rewriting the header (e.g.
for changing the backing file). Save all unknown header extensions in a
list of blobs and include them in a new header.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-02-09 16:17:51 +01:00
Kevin Wolf
e24e49e619 qcow2: Update whole header at once
In order to switch the backing file, qcow2 issues multiple write
requests that only changed a part of the image header. Any failure after
the first one would leave the header in an corrupted state. With this
patch, the whole header is written at once, so we can't fail in the
middle.

At the same time, this gives us a reusable functions that updates all
fields of the qcow2 header and not only the backing file.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-02-09 16:17:51 +01:00
Kevin Wolf
c2c9a46609 qcow2: Allow >4 GB VM state
This is a compatible extension to the snapshot header format that allows
saving a 64 bit VM state size.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-12-15 12:40:33 +01:00
Anthony Liguori
06d9260ffa qcow2: implement bdrv_invalidate_cache (v2)
We don't reopen the actual file, but instead invoke the close and open routines.
We specifically ignore the backing file since it's contents are read-only and
therefore immutable.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-11-21 14:58:48 -06:00
Frediano Ziglio
a791236992 qcow2: removed unused depends_on field
Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-09-12 15:17:17 +02:00
Frediano Ziglio
2f4b759367 qcow2: remove unused qcow2_create_refcount_update function
Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-25 15:23:10 +02:00
Kevin Wolf
68d100e905 qcow2: Use coroutines
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-02 15:53:41 +02:00
Kevin Wolf
93913dfd8a qcow2: Use Qcow2Cache in writeback mode during loadvm/savevm
In snapshotting there is no guest involved, so we can safely use a writeback
mode and do the flushes in the right place (i.e. at the very end). This
improves the time that creating/restoring an internal snapshot takes with an
image in writethrough mode.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-07-19 15:39:22 +02:00
Kevin Wolf
99cce9fa4e qemu-img create: Fix displayed default cluster size
When not specifying a cluster size on the command line, qemu-img printed
a cluster size of 0:

    Formatting '/tmp/test.qcow2', fmt=qcow2 size=67108864
    encryption=off cluster_size=0

This patch adds the default cluster size to the QEMUOptionParameter list, so
that it displays the default value that is used.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-06-08 11:56:40 +02:00
Kevin Wolf
5ea929e3d1 qcow2: Add bdrv_discard support
This adds a bdrv_discard function to qcow2 that frees the discarded clusters.
It does not yet pass the discard on to the underlying file system driver, but
the space can be reused by future writes to the image.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2011-01-31 10:03:00 +01:00
Kevin Wolf
3de0a2944b qcow2: Batch flushes for COW
qcow2 calls bdrv_flush() after performing COW in order to ensure that the
L2 table change is never written before the copy is safe on disk. Now that the
L2 table is cached, we can wait with flushing until we write out the next L2
table.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-01-24 16:41:49 +01:00
Kevin Wolf
29c1a7301a qcow2: Use QcowCache
Use the new functions of qcow2-cache.c for everything that works on refcount
block and L2 tables.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-01-24 16:41:49 +01:00
Kevin Wolf
493810940b qcow2: Add QcowCache
This adds some new cache functions to qcow2 which can be used for caching
refcount blocks and L2 tables. When used with cache=writethrough they work
like the old caching code which is spread all over qcow2, so for this case we
have merely a cleanup.

The interesting case is with writeback caching (this includes cache=none) where
data isn't written to disk immediately but only kept in cache initially. This
leads to some form of metadata write batching which avoids the current "write
to refcount block, flush, write to L2 table" pattern for each single request
when a lot of cluster allocations happen. Instead, cache entries are only
written out if its required to maintain the right order. In the pure cluster
allocation case this means that all metadata updates for requests are done in
memory initially and on sync, first the refcount blocks are written to disk,
then fsync, then L2 tables.

This improves performance of scenarios with lots of cluster allocations
noticably (e.g. installation or after taking a snapshot).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-01-24 11:08:51 +01:00
Kevin Wolf
80465c5016 block: Remove unused s->hd in various drivers
All drivers use bs->file instead of s->hd for quite a while now, so it's time
to remove s->hd.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2010-11-24 17:31:06 +01:00
edison
51ef67270b Copy snapshots out of QCOW2 disk
In order to backup snapshots, created from QCOW2 iamge, we want to copy snapshots out of QCOW2 disk to a seperate storage.
The following patch adds a new option in "qemu-img": qemu-img convert -f qcow2 -O qcow2 -s snapshot_name src_img bck_img.
Right now, it only supports to copy the full snapshot, delta snapshot is on the way.

Changes from V1: all the comments from Kevin are addressed:
Add read-only checking
Fix coding style
Change the name from bdrv_snapshot_load to bdrv_snapshot_load_tmp

Signed-off-by: Disheng Su <edison@cloud.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-10-22 14:49:35 +02:00
Stefan Hajnoczi
72893756e0 qcow2: Support exact L1 table growth
The L1 table grow operation includes a size calculation that bumps up
the new L1 table size in order to anticipate the size needs of vmstate
data.  This helps reduce the number of times that the L1 table has to be
grown when vmstate data is appended.

This size overhead is not necessary during image creation,
bdrv_truncate(), or snapshot goto operations.  In fact, existing
qemu-iotests that exercise table growth are no longer able to trigger it
because image creation preallocates an L1 table that is too large after
changes to qcow_create2().

This patch keeps the size calculation but also adds exact growth for
callers that do not want to inflate the L1 table size unnecessarily.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-10-22 14:49:35 +02:00
Kevin Wolf
bd28f83565 qcow2: Avoid bounce buffers for AIO read requests
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>
2010-09-21 15:39:42 +02:00
Kevin Wolf
9ac228e02c qcow2/vdi: Change check to distinguish error cases
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>
2010-07-06 17:05:49 +02:00
Kevin Wolf
1c46efaa0a qcow2: Allow qcow2_get_cluster_offset to return errors
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>
2010-05-28 13:29:11 +02:00
Stefan Hajnoczi
419b19d9b4 qcow2: Implement bdrv_truncate() for growing images
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>
2010-05-03 10:07:32 +02:00
Kevin Wolf
66f82ceed6 block: Open the underlying image file in generic code
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>
2010-05-03 10:07:30 +02:00
Kevin Wolf
f4f0d391b2 qcow2: Fix signedness bugs
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>
2010-02-10 11:56:57 -06:00
Kevin Wolf
148da7ea9d 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 <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2010-01-26 14:59:19 -06:00
Kevin Wolf
72ecf02d7d Revert "qcow2: Bring synchronous read/write back to life"
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>
2009-10-27 12:28:59 -05:00
Kevin Wolf
ef845c3bf4 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.

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>
2009-10-15 09:32:04 -05:00
Kevin Wolf
80ee15a6b2 qcow2: Increase maximum cluster size to 2 MB
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>
2009-10-05 09:32:52 -05:00
Blue Swirl
72cf2d4f0e 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 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>
2009-09-12 07:36:22 +00:00
Kevin Wolf
f214978a42 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
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>
2009-09-09 17:31:26 -05:00
Filip Navara
14899cdf3a Fix QCOW2 debugging code to compile again
Updated to use C99 comments.

Signed-off-by: Filip Navara <filip.navara@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2009-06-29 08:52:40 -05:00
Kevin Wolf
ed6ccf0f51 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
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>
2009-06-16 15:18:36 -05:00
Kevin Wolf
c142442b06 qcow2: Split out snapshot functions
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>
2009-06-16 15:18:36 -05:00
Kevin Wolf
45aba42fba 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
two-level lookup tables.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2009-06-16 15:18:36 -05:00
Kevin Wolf
f7d0fe0239 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
the split qcow2 modules.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2009-06-16 15:18:36 -05:00