Commit Graph

27 Commits

Author SHA1 Message Date
aliguori 4dc822d726 Use writeback caching by default with qcow2
qcow2 writes a cluster reference count on every cluster update.  This causes
performance to crater when using anything but cache=writeback.  This is most
noticeable when using savevm.  Right now, qcow2 isn't a reliable format
regardless of the type of cache your using because metadata is not updated in
the correct order.  Considering this, I think it's somewhat reasonable to use
writeback caching by default with qcow2 files.

It at least avoids the massive performance regression for users until we sort
out the issues in qcow2. 

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5879 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-04 21:39:21 +00:00
aliguori e976c6a1e4 Change order of metadata update to prevent loosing guest data because of unexpected exit (Gleb Natapov)
Currently the order is this (during cow since it's the interesting case):
1. Decrement refcount of old clusters
2. Increment refcount for newly allocated clusters
3. Copy content of old sectors that will not be rewritten
4. Update L2 table with pointers to new clusters
5. Write guest data into new clusters (asynchronously)

There are several problems with this order. The first one is that if qemu
crashes (or killed or host reboots) after new clusters are linked into L2
table but before user data is written there, then on the next reboot guest
will find neither old data nor new one in those sectors and this is not
what gust expects even when journaling file system is in use.  The other
problem is that if qemu is killed between steps 1 and 4 then refcount
of old cluster will be incorrect and may cause snapshot corruption.

The patch change the order to be like this:
1. Increment refcount for newly allocated clusters
2. Write guest data into new clusters (asynchronously)
3. Copy content of old sectors that were not rewritten
4. Update L2 table with pointers to new clusters
5. Decrement refcount of old clusters

Unexpected crash may cause cluster leakage, but guest data should be safe.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5861 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-02 20:14:05 +00:00
aliguori 6db6c63826 Cleanup {alloc|get}_cluster_offset() (Gleb Natapov)
Move duplicated code into helper functions.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5860 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-02 20:11:27 +00:00
aliguori 643e5399bb Write table offset and size in one syscall (Gleb Natapov)
Otherwise if VM is killed between two writes data may be lost.
But if offset and size fields are at the same disk block one
write should update them both simultaneously.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5859 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-02 20:10:14 +00:00
aliguori a32ef786f4 Introduce new helper function qcow_shedule_bh() (Gleb Natapov)
Use it to remove code duplications from qcow_aio_read_cb().

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5858 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-02 20:08:04 +00:00
aliguori ac67488746 Remove tabs from qcow_aio_read_cb(). (Gleb Natapov)
Fix indentation.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5857 c046a42c-6fe2-441c-8c8c-71466251a162
2008-12-02 20:06:51 +00:00
aliguori 1490791f61 fix bdrv_aio_read API breakage in qcow2 (Andrea Arcangeli)
I noticed the qemu_aio_flush was doing nothing at all. And a flood of
cmd_writeb commands leading to a noop-invocation of qemu_aio_flush
were executed.

In short all 'memset;goto redo' places must be fixed to use the bh and
not to call the callback in the context of bdrv_aio_read or the
bdrv_aio_read model falls apart. Reading from qcow2 holes is possible
with phyisical readahead (kind of breada in linux buffer cache).

This is needed at least for scsi, ide is lucky (or it has been
band-aided against this API breakage by fixing the symptom and not the
real bug).

Same bug exists in qcow of course, can be fixed later as it's less
urgent.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5574 c046a42c-6fe2-441c-8c8c-71466251a162
2008-10-31 17:28:00 +00:00
aliguori f4af02ed1b fix bug in block-qcow2.c:alloc_cluster_offset() (Shahar Frank)
During the debugging of the new revision of the zero dedup patch I
stepped on the following bug in block-qcow2.c:alloc_cluster_offset(). I
am not sure what the exact damage this bug can do, but it may be very
nasty because you way not notice it effects until you will do some
snapshot operations or similar actions that rely on the reference
counting.

The bug is easy to spot using the new "check" verb I added to the
qemu-img in one of the previous patches. I will resend the qemu-img
patch again with the new version of the zero dedup.

Signed-off-by: Shahar Frank <shaharf@qumranet.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5313 c046a42c-6fe2-441c-8c8c-71466251a162
2008-09-24 16:52:15 +00:00
balrog ac509d8887 Move offsetof to osdep.h, remove local defintions.
With this container_of can actually be used without causing build errors.
Reformat container_of.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5234 c046a42c-6fe2-441c-8c8c-71466251a162
2008-09-16 13:36:57 +00:00
aliguori bc352085d2 qcow2: Try to aggregate free clusters and freed clusters (Laurent Vivier)
In alloc_cluster_offset(), try to aggregate free clusters and freed clusters.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5008 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:11:52 +00:00
aliguori 768706a52f qcow2: Make sure to return an error when L2 table loading fails
This was suggested by Kevin Wolf since this is, in fact, an error condition.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5007 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:11:00 +00:00
aliguori 095a9c58ce qcow2: Aggregate same type clusters (Laurent Vivier)
Modify get_cluster_offset(), alloc_cluster_offset() to specify how many clusters
we want.

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5006 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:10:28 +00:00
aliguori 52d893ecf9 Extract compressing part from alloc_cluster_offset() (Laurent Vivier)
Divide alloc_cluster_offset() into alloc_cluster_offset() and
alloc_compressed_cluster_offset().
Common parts are moved to free_any_clusters() and get_cluster_table();

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5005 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:09:32 +00:00
aliguori 052035244f Divide get_cluster_offset() (Laurent Vivier)
Divide get_cluster_offset() into get_cluster_offset() and
alloc_cluster_offset().

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5004 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:08:21 +00:00
aliguori 108534b968 qcow2: Extract code from get_cluster_offset() (Laurent Vivier)
Extract code from get_cluster_offset() into new functions:

- seek_l2_table()

Search an l2 offset in the l2_cache table.

- l2_load()

Read the l2 entry from disk

- l2_allocate()

Allocate a new l2 entry.

Some comment fixups from Kevin Wolf

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Kevin Wolf <kwolf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5003 c046a42c-6fe2-441c-8c8c-71466251a162
2008-08-14 18:07:12 +00:00
aurel32 b5eff35546 Revert fix for CVE-2008-0928. Will be fixed in a different way later.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4041 c046a42c-6fe2-441c-8c8c-71466251a162
2008-03-11 23:30:22 +00:00
aurel32 902b27d0b8 Fix CVE-2008-0928 - insufficient block device address range checking
Qemu 0.9.1 and earlier does not perform range checks for block device
read or write requests, which allows guest host users with root
privileges to access arbitrary memory and escape the virtual machine.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4037 c046a42c-6fe2-441c-8c8c-71466251a162
2008-03-11 17:17:59 +00:00
pbrook faf07963cb Split block API from vl.h.
Remove QEMU_TOOL. Replace with QEMU_IMG and NEED_CPU_H.
Avoid linking qemu-img against whole system emulatior.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3578 c046a42c-6fe2-441c-8c8c-71466251a162
2007-11-11 02:51:17 +00:00
ths 3b46e62427 find -type f | xargs sed -i 's/[\t ]*$//g' # Yes, again. Note the star in the regex.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3177 c046a42c-6fe2-441c-8c8c-71466251a162
2007-09-17 08:09:54 +00:00
ths ec36ba1474 vmdk compatibility level 6 images, by Soren Hansen.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3175 c046a42c-6fe2-441c-8c8c-71466251a162
2007-09-16 21:59:02 +00:00
ths 5fafdf24ef find -type f | xargs sed -i 's/[\t ]$//g' # on most files
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3173 c046a42c-6fe2-441c-8c8c-71466251a162
2007-09-16 21:08:06 +00:00
ths 23be50f1af Qcow2: Release refcount table clusters after growing the refcount table,
by Juergen Keil.


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2586 c046a42c-6fe2-441c-8c8c-71466251a162
2007-04-02 12:48:47 +00:00
ths a4080ece74 Qcow2 corruption fix, by Juergen Keil.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2578 c046a42c-6fe2-441c-8c8c-71466251a162
2007-04-01 19:01:40 +00:00
pbrook ce1a14dc0d Dynamically allocate AIO Completion Blocks.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2098 c046a42c-6fe2-441c-8c8c-71466251a162
2006-08-07 02:38:06 +00:00
bellard a946592212 handle read outside the backing file
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2093 c046a42c-6fe2-441c-8c8c-71466251a162
2006-08-06 13:34:04 +00:00
bellard 15e6690aca fixed disk image creation
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2089 c046a42c-6fe2-441c-8c8c-71466251a162
2006-08-05 22:24:28 +00:00
bellard 585f8587ad new qcow2 disk image format
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@2083 c046a42c-6fe2-441c-8c8c-71466251a162
2006-08-05 21:14:20 +00:00