Commit Graph

70 Commits

Author SHA1 Message Date
Kevin Wolf
54e6814360 qcow2: Limit COW to where it's needed
This fixes a regression introduced in commit 250196f1. The bug leads to
data corruption, found during an Autotest run with a Fedora 8 guest.

Consider a write request whose first part is covered by an already
allocated cluster, but additional clusters need to be newly allocated.
When counting the number of clusters to allocate, the qcow2 code would
decide to do COW for all remaining clusters of the write request, even
if some of them are already allocated.

If during this COW operation another write request is issued that touches
the same cluster, it will still refer to the old cluster. When the COW
completes, the first request will update the L2 table and the second
write request will be lost. Note that the requests need not overlap, it's
enough for them to touch the same cluster.

This patch ensures that only clusters that really require COW are
considered for allocation. In this case any other request writing to the
same cluster will be an allocating write and gets serialised.

Reported-by: Marcelo Tosatti <mtosatti@redhat.com>
Tested-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-05-07 19:33:18 +02:00
Kevin Wolf
7242411460 qcow2: Don't hold cache references across yield
If cache references are held while the coroutine has yielded, the cache
may get used up and abort() when it can't find a free entry.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-05-02 18:39:39 +02:00
Kevin Wolf
60651f901a qcow2: Remove unused parameter in do_alloc_cluster_offset
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-05-02 18:39:39 +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
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
143550a83e qcow2: Simplify count_cow_clusters
count_cow_clusters() tries to reuse existing functions, and all it
achieves is to make things much more complicated than they really are:
Everything needs COW, unless it's a normal cluster with refcount 1.

This patch implements the obvious way of doing this, and by using
qcow2_get_cluster_type() it gets rid of all flag magic.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:28 +02:00
Kevin Wolf
8e37f681d5 qcow2: Ignore reserved bits in L1/L2 entries
This changes the still existing places that assume that the only flags
are QCOW_OFLAG_COPIED and QCOW_OFLAG_COMPRESSED to properly mask out
reserved bits.

It does not convert bdrv_check yet.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:28 +02:00
Kevin Wolf
b0b6862e5e qcow2: Fail write_compressed when overwriting data
qcow2_alloc_compressed_cluster_offset() already fails if the copied flag
is set, because qcow2_write_compressed() doesn't perform COW as it would
have to do to allow this.

However, what we really want to check here is whether the cluster is
allocated or not. With internal snapshots the copied flag may not be set
on allocated clusters. Check the cluster offset instead.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:27 +02:00
Kevin Wolf
2bfcc4a0a0 qcow2: Ignore reserved bits in count_contiguous_clusters()
Until now, count_contiguous_clusters() has an argument that allowed to
specify flags that should be ignored in the comparison, i.e. that are
allowed to change between contiguous clusters.

This patch changes the function so that it ignores all flags by default
now and you need to pass the flags on which it should stop.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-20 15:57:27 +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
8dc0a5e7a0 qcow2: Fix error handling in qcow2_alloc_cluster_offset
If do_alloc_cluster_offset() fails, the error handling code tried to
remove the request from the in-flight queue, to which it wasn't added
yet, resulting in a NULL pointer dereference.

m->nb_clusters really only becomes != 0 when the request is in the list.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2012-04-19 16:03:27 +02:00
Kevin Wolf
3948d1d487 qcow2: Remove unused parameter in get_cluster_table()
Since everything goes through the cache, callers don't use the L2 table
offset any more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-04-05 14:54:39 +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
bf319ece56 qcow2: Factor out count_cow_clusters
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
3cce16f44d qcow2: Add some tracing
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2012-03-12 15:14:06 +01:00
Stefan Hajnoczi
aef4acb661 qcow2: avoid reentrant bdrv_read() in copy_sectors()
A BlockDriverState should not issue requests on itself through the
public block layer interface.  Nested, or reentrant, requests are
problematic because they do I/O throttling and request tracking twice.

Features like block layer copy-on-read use request tracking to avoid
race conditions between concurrent requests.  The reentrant request will
have to "wait" for its parent request to complete.  But the parent is
waiting for the reentrant request to make progress so we have reached
deadlock.

The solution is for block drivers to avoid the public block layer
interfaces for reentrant requests.   Instead they should call their own
internal functions if they wish to perform reentrant requests.

This is also a good opportunity to make copy_sectors() a true
coroutine_fn.  That means calling bdrv_co_writev() instead of
bdrv_write().  Behavior is unchanged but we're being explicit that this
executes in coroutine context.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-12-05 14:49:47 +01:00
Kevin Wolf
1b9f1491f8 qcow2: Unlock during COW
Unlocking during COW allows for more parallelism. One change it requires is
that buffers are dynamically allocated instead of just using a per-image
buffer.

While touching the code, drop the synchronous qcow2_read() function and replace
it by a bdrv_read() call.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-12-05 14:49:40 +01:00
Kevin Wolf
8f1efd00c4 qcow2: Fix bdrv_write_compressed error handling
If during allocation of compressed clusters the cluster was already allocated
uncompressed, fail and properly release the l2_table (the latter avoids a
failed assertion).

While at it, make it return some real error numbers instead of -1.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
2011-10-21 17:34:13 +02:00
Frediano Ziglio
ee18e73023 qcow2: fix range check
QCowL2Meta::offset is not cluster aligned but only sector aligned
however nb_clusters count cluster from cluster start.
This fix range check. Note that old code have no corruption issues
related to this check cause it only cause intersection to occur
when shouldn't.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-09-12 15:17:22 +02:00
Frediano Ziglio
05140499d3 qcow2: initialize metadata before inserting in cluster_allocs
QCow2Meta structure was inserted into list before many fields are
initialized. Currently is not a problem cause all occur in a lock
but if qcow2_alloc_clusters would in a future unlock this lock
some issues could arise.
Initializing fields before inserting fix the problem.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-09-12 15:17:22 +02:00
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
35ee5e39c5 qcow2: use always stderr for debugging
let all DEBUG_ALLOC2 printf goes to stderr

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-25 15:22:25 +02:00
Devin Nakamura
d57237f291 qcow2: fix typo in documentation for qcow2_get_cluster_offset()
Documentation states the num is measured in clusters, but its
actually measured in sectors

Signed-off-by: Devin Nakamura <devin122@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-23 14:15:17 +02:00
Anthony Liguori
7267c0947d Use glib memory allocation and free functions
qemu_malloc/qemu_free no longer exist after this commit.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
2011-08-20 23:01:08 -05:00
Kevin Wolf
68d100e905 qcow2: Use coroutines
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-08-02 15:53:41 +02:00
Kevin Wolf
9e2a3701a1 qcow2: Fix in-flight list after qcow2_cache_put failure
If qcow2_cache_put returns an error during cluster allocation and the
allocation fails, it must be removed from the list of in-flight allocations.
Otherwise we'd get a loop in the list when the ACB is used for the next
allocation.

Luckily, this qcow2_cache_put shouldn't fail anyway because the L2 table is
only read, so that qcow2_cache_put doesn't even involve I/O.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2011-06-15 14:36:15 +02:00
Kevin Wolf
80fa3341a7 qcow2: Fix memory leaks in error cases
This fixes memory leaks that may be caused by I/O errors during L1 table growth
(can happen during save_vm) and in qemu-img check.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-06-08 11:56:40 +02:00
Kevin Wolf
16fde5f2c2 qcow2: Fix order in L2 table COW
When copying L2 tables (this happens only with internal snapshots), the order
wasn't completely safe, so that after a crash you could end up with a L2 table
that has too low refcount, possibly leading to corruption in the long run.

This patch puts the operations in the right order: First allocate the new
L2 table and replace the reference, and only then decrease the refcount of the
old table.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-02-10 13:24:29 +01:00
Kevin Wolf
8af3648843 qcow2: Fix error handling for reading compressed clusters
When reading a compressed cluster failed, qcow2 falsely returned success.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
2011-02-10 13:23:44 +01:00
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
Aurelien Jarno
653df36bbe qcow2: fix unaligned access
cpu_to_be64w() is called with an obviously non-aligned pointer. Use
cpu_to_be64wu() instead. It fixes unaligned accesses errors on IA64
hosts.

Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-01-24 11:08:50 +01:00
Jes Sorensen
7c80ab3f21 block/qcow2.c: rename qcow_ functions to qcow2_
It doesn't really make sense for functions in qcow2.c to be named
qcow_ so convert the names to match correctly.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-12-17 16:15:01 +01:00
Kevin Wolf
1c02e2a171 qcow2: Invalidate cache after failed read
The cache content may be destroyed after a failed read, better not use it any
more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
2010-11-04 13:54:37 +01:00
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
9f8e668eb1 qcow2: Get rid of additional sync on COW
We always have a sync for the refcount update when a new cluster is
allocated. If we move this past the COW, we can save an additional sync.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-09-21 15:39:42 +02:00
Kevin Wolf
29216ed14f qcow2: Move sync out of qcow2_alloc_clusters
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-09-21 15:39:42 +02:00
Kevin Wolf
7ec5e6a4ca qcow2: Remove unnecessary flush after L2 write
When a new cluster was allocated, we only need a flush after the write to the
L2 table if it was a COW and we need to decrease the refcounts of the old
clusters.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-09-08 12:39:24 +02:00
Kevin Wolf
8b3b720620 qcow2: Use bdrv_(p)write_sync for metadata writes
Use bdrv_(p)write_sync to ensure metadata integrity in case of a crash.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-06-22 14:38:02 +02:00
Kevin Wolf
68dba0bf45 qcow2: Restore L1 entry on l2_allocate failure
If writing the L1 table to disk failed, we need to restore its old content in
memory to avoid inconsistencies.

Reported-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-06-15 09:41:58 +02:00
Kevin Wolf
55c17e9821 qcow2: Change l2_load to return 0/-errno
Provide the error code to the caller instead of just indicating success/error.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-05-28 13:29:12 +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
Kevin Wolf
175e11526e qcow2: Fix error handling in l2_allocate
l2_allocate has some intermediate states in which the image is inconsistent.
Change the order to write to the L1 table only after the new L2 table has
successfully been initialized.

Also reset the L2 cache in failure case, it's very likely wrong.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-05-28 13:14:25 +02:00
Kevin Wolf
1b7c801b40 qcow2: Clear L2 table cache after write error
If the L2 table was already updated in cache, but writing it to disk has
failed, we must not continue using the changed version in the cache to stay
consistent with what's on the disk.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-05-28 13:14:25 +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
c46e116723 qcow2: Return 0/-errno in l2_allocate
Returning NULL on error doesn't allow distinguishing between different errors.
Change the interface to return an integer for -errno.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-04-23 16:08:46 +02:00
Kevin Wolf
f7defcb627 qcow2: Return 0/-errno in write_l1_entry
Change write_l1_entry to return the real error code instead of -1.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-04-23 16:08:46 +02:00
Kevin Wolf
c835d00fc8 qcow2: Fix error return code in qcow2_alloc_cluster_link_l2
Fix qcow2_alloc_cluster_link_l2 to return the real error code like it does in
all other error cases.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2010-04-23 16:08:46 +02:00