Commit Graph

107 Commits

Author SHA1 Message Date
Peter Lieven
7337acaf21 block: add opt_transfer_length to BlockLimits
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-05 11:45:24 +01:00
Wenchao Xia
8c116b0e41 qemu-nbd: support internal snapshot export
Now it is possible to directly export an internal snapshot, which
can be used to probe the snapshot's contents without qemu-img
convert.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-04 15:19:00 +01:00
Wenchao Xia
7b4c4781e3 snapshot: distinguish id and name in load_tmp
Since later this function will be used so improve it. The only caller of it
now is qemu-img, and it is not impacted by introduce function
bdrv_snapshot_load_tmp_by_id_or_name() that call bdrv_snapshot_load_tmp()
twice to keep old search logic. bdrv_snapshot_load_tmp_by_id_or_name() return
int to let caller know the errno, and errno will be used later.
Also fix a typo in comments of bdrv_snapshot_delete().

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-04 15:19:00 +01:00
Paolo Bonzini
d5ef94d43d block: add bdrv_aio_write_zeroes
This will be used by the SCSI layer.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-03 15:26:49 +01:00
Paolo Bonzini
d20d9b7c67 block: add flags to BlockRequest
This lets bdrv_co_do_rw receive flags, so that it can be used for
zero writes.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-03 15:26:48 +01:00
Marc-André Lureau
7b6b145dbc coroutine: remove unused CoQueue AioContext
The AioContext ctx field is apparently unused in qemu codebase since
02ffb50448.

Signed-off-by: Marc-André Lureau <marcandre.lureau@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-02 17:11:49 +01:00
Marc-André Lureau
f287c41381 coroutine: remove qemu_co_queue_wait_insert_head
qemu_co_queue_wait_insert_head() is unused in qemu code base now.

Signed-off-by: Marc-André Lureau <marcandre.lureau@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-02 17:11:49 +01:00
Fam Zheng
4cc70e9337 blkdebug: add "remove_break" command
This adds "remove_break" command which is the reverse of blkdebug
command "break": it removes all breakpoints with given tag and resumes
all the requests.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-29 13:40:37 +01:00
Liu Yuan
b3af018f3b sheepdog: support user-defined redundancy option
Sheepdog support two kinds of redundancy, full replication and erasure coding.

# create a fully replicated vdi with x copies
 -o redundancy=x (1 <= x <= SD_MAX_COPIES)

# create a erasure coded vdi with x data strips and y parity strips
 -o redundancy=x:y (x must be one of {2,4,8,16} and 1 <= y < SD_EC_MAX_STRIP)

E.g, to convert a vdi into sheepdog vdi 'test' with 8:3 erasure coding scheme

$ qemu-img convert -o redundancy=8:3 linux-0.2.img sheepdog:test

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-29 13:40:37 +01:00
Fam Zheng
21b5683508 qapi: Change BlockDirtyInfo to list
We have multiple dirty bitmaps in BDS now, switch QAPI to allow query
it (BlockInfo.dirty_bitmaps), and also drop old BlockInfo.dirty.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-11-29 13:40:36 +01:00
Fam Zheng
e4654d2d94 block: per caller dirty bitmap
Previously a BlockDriverState has only one dirty bitmap, so only one
caller (e.g. a block job) can keep track of writing. This changes the
dirty bitmap to a list and creates a BdrvDirtyBitmap for each caller, the
lifecycle is managed with these new functions:

    bdrv_create_dirty_bitmap
    bdrv_release_dirty_bitmap

Where BdrvDirtyBitmap is a linked list wrapper structure of HBitmap.

In place of bdrv_set_dirty_tracking, a BdrvDirtyBitmap pointer argument
is added to these functions, since each caller has its own dirty bitmap:

    bdrv_get_dirty
    bdrv_dirty_iter_init
    bdrv_get_dirty_count

bdrv_set_dirty and bdrv_reset_dirty prototypes are unchanged but will
internally walk the list of all dirty bitmaps and set them one by one.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-11-29 13:40:33 +01:00
Peter Lieven
d75cbb5e68 block: introduce bdrv_make_zero
this patch adds a call to completely zero out a block device.
the operation is sped up by checking the block status and
only writing zeroes to the device if they currently do not
return zeroes. optionally the zero writing can be sped up
by setting the flag BDRV_REQ_MAY_UNMAP to emulate the zero
write by unmapping if the driver supports it.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:52 +01:00
Peter Lieven
fe81c2cca6 block: add BlockLimits structure to BlockDriverState
this patch adds BlockLimits which introduces discard and write_zeroes
limits and alignment information to the BlockDriverState.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
Peter Lieven
4ce786914b block: add wrappers for logical block provisioning information
This adds 2 wrappers to read the unallocated_blocks_are_zero and
can_write_zeroes_with_unmap info from the BDI. The wrappers are
required to check for the existence of a backing_hd and
if the devices are opened with the correct flags.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
Peter Lieven
e1a5c4bed4 block: add logical block provisioning info to BlockDriverInfo
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
Peter Lieven
d32f35cbc5 block: introduce BDRV_REQ_MAY_UNMAP request flag
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
Peter Lieven
aa7bfbfff7 block: add flags to bdrv_*_write_zeroes
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
Peter Lieven
6faac15fa8 block: make BdrvRequestFlags public
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-28 10:30:51 +01:00
MORITA Kazutaka
3ab7bd1917 coroutine: add co_aio_sleep_ns() to allow sleep in block drivers
This helper function behaves similarly to co_sleep_ns(), but the
sleeping coroutine will be resumed when using qemu_aio_wait().

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Tested-by: Liu Yuan <namei.unix@gmail.com>
Reviewed-by: Liu Yuan <namei.unix@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-30 12:22:09 +01:00
Kevin Wolf
b94a261057 block: Avoid unecessary drv->bdrv_getlength() calls
The block layer generally keeps the size of an image cached in
bs->total_sectors so that it doesn't have to perform expensive
operations to get the size whenever it needs it.

This doesn't work however when using a backend that can change its size
without qemu being aware of it, i.e. passthrough of removable media like
CD-ROMs or floppy disks. For this reason, the caching is disabled when a
removable device is used.

It is obvious that checking whether the _guest_ device has removable
media isn't the right thing to do when we want to know whether the size
of the host backend can change. To make things worse, non-top-level
BlockDriverStates never have any device attached, which makes qemu
assume they are removable, so drv->bdrv_getlength() is always called on
the protocol layer. In the case of raw-posix, this causes unnecessary
lseek() system calls, which turned out to be rather expensive.

This patch completely changes the logic and disables bs->total_sectors
caching only for certain block driver types, for which a size change is
expected: host_cdrom and host_floppy on POSIX, host_device on win32; also
the raw format in case it sits on top of one of these protocols, but in
the common case the nested bdrv_getlength() call on the protocol driver
will use the cache again and avoid an expensive drv->bdrv_getlength()
call.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2013-10-29 13:10:26 +01:00
Benoît Canet
f6186f49e2 block: Add BlockDriver.bdrv_check_ext_snapshot.
This field is used by blkverify to disable external snapshots creation.
It will also be used by block filters like quorum to disable external
snapshot creation.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 16:49:59 +02:00
Peter Lieven
92bc50a5ad block/get_block_status: avoid redundant callouts on raw devices
if a raw device like an iscsi target or host device is used
the current implementation makes a second call out to get
the block status of bs->file.

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 16:49:59 +02:00
Max Reitz
a8d8ecb77f block/qapi: Human-readable ImageInfoSpecific dump
Add a function for generically dumping the ImageInfoSpecific information
in a human-readable format to block/qapi.c.

Use this function in bdrv_image_info_dump and qemu-io-cmds.c:info_f to
allow qemu-img info resp. qemu-io -c info to print that format specific
information.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 10:52:54 +02:00
Max Reitz
eae041fe6f block: Add bdrv_get_specific_info
Add a function for retrieving an ImageInfoSpecific object from a block
driver.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 10:52:54 +02:00
Fam Zheng
79e14bf778 qapi: make use of new BlockJobType
Switch the string to enum type BlockJobType in BlockJobDriver.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 10:52:54 +02:00
Fam Zheng
3fc4b10af0 blockjob: rename BlockJobType to BlockJobDriver
We will use BlockJobType as the enum type name of block jobs in QAPI,
rename current BlockJobType to BlockJobDriver, which will eventually
become a set of operations, similar to block drivers.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-10-11 10:52:54 +02:00
Benoît Canet
030be32184 block: introduce BlockDriver.bdrv_needs_filename to enable some drivers.
Some drivers will have driver specifics options but no filename.
This new bool allow the block layer to treat them correctly.

The .bdrv_needs_filename is set in drivers not having .bdrv_parse_filename and
not having .bdrv_open.

The first exception to this rule will be the quorum driver.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 16:21:28 +02:00
Max Reitz
cc84d90ff5 block: Error parameter for create functions
Add an Error ** parameter to bdrv_create and its associated functions to
allow more specific error messages.

Signed-off-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:48 +02:00
Max Reitz
34b5d2c68e block: Error parameter for open functions
Add an Error ** parameter to bdrv_open, bdrv_file_open and associated
functions to allow more specific error messages.

Signed-off-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:48 +02:00
Max Reitz
d5124c00d8 bdrv: Use "Error" for creating images
Add an Error ** parameter to BlockDriver.bdrv_create to allow more
specific error messages.

Signed-off-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:48 +02:00
Max Reitz
015a1036a7 bdrv: Use "Error" for opening images
Add an Error ** parameter to BlockDriver.bdrv_open and
BlockDriver.bdrv_file_open to allow more specific error messages.

Signed-off-by: Max Reitz <mreitz@redhat.com>
2013-09-12 10:12:47 +02:00
Wenchao Xia
a89d89d3e6 snapshot: distinguish id and name in snapshot delete
Snapshot creation actually already distinguish id and name since it take
a structured parameter *sn, but delete can't. Later an accurate delete
is needed in qmp_transaction abort and blockdev-snapshot-delete-sync,
so change its prototype. Also *errp is added to tip error, but return
value is kepted to let caller check what kind of error happens. Existing
caller for it are savevm, delvm and qemu-img, they are not impacted by
introducing a new function bdrv_snapshot_delete_by_id_or_name(), which
check the return value and do the operation again.

Before this patch:
  For qcow2, it search id first then name to find the one to delete.
  For rbd, it search name.
  For sheepdog, it does nothing.

After this patch:
  For qcow2, logic is the same by call it twice in caller.
  For rbd, it always fails in delete with id, but still search for name
in second try, no change to user.

Some code for *errp is based on Pavel's patch.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12 10:12:47 +02:00
Wenchao Xia
2ea1dd758c snapshot: new function bdrv_snapshot_find_by_id_and_name()
To make it clear about id and name in searching, add this API
to distinguish them. Caller can choose to search by id or name,
*errp will be set only for exception.

Some code are modified based on Pavel's patch.

Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12 10:12:47 +02:00
Max Reitz
6f176b48f9 block: Image file option amendment
This patch adds the "amend" option to qemu-img which allows changing
image options on existing image files. It also adds the generic bdrv
implementation which is basically just a wrapper for the image format
specific function.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-12 10:12:46 +02:00
Paolo Bonzini
4333bb7140 block: define get_block_status return value
Define the return value of get_block_status.  Bits 0, 1, 2 and 9-62
are valid; bit 63 (the sign bit) is reserved for errors.  Bits 3-8
are left for future extensions.

The return code is compatible with the old is_allocated API: if a driver
only returns 0 or 1 (aka BDRV_BLOCK_DATA) like is_allocated used to,
clients of is_allocated will not have any change in behavior.  Still,
we will return more precise information in the next patches and the
new definition of bdrv_is_allocated is already prepared for this.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:09 +02:00
Paolo Bonzini
b6b8a33354 block: introduce bdrv_get_block_status API
For now, bdrv_get_block_status is just another name for bdrv_is_allocated.
The next patches will add more flags.

This also touches all block drivers with a mostly mechanical rename.  The
sole exception is cow; because it calls cow_co_is_allocated from the read
code, we keep that function and make cow_co_get_block_status a wrapper.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:09 +02:00
Paolo Bonzini
4f5786376e block: remove bdrv_is_allocated_above/bdrv_co_is_allocated_above distinction
Now that bdrv_is_allocated detects coroutine context, the two can
use the same code.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:09 +02:00
Paolo Bonzini
bdad13b9de block: make bdrv_co_is_allocated static
bdrv_is_allocated can detect coroutine context and go through a fast
path, similar to other block layer functions.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:08 +02:00
Fam Zheng
4f6fd3491c block: make bdrv_delete() static
Manage BlockDriverState lifecycle with refcnt, so bdrv_delete() is no
longer public and should be called by bdrv_unref() if refcnt is
decreased to 0.

This is an identical change because effectively, there's no multiple
reference of BDS now: no caller of bdrv_ref() yet, only bdrv_new() sets
bs->refcnt to 1, so all bdrv_unref() now actually delete the BDS.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:08 +02:00
Fam Zheng
9fcb025146 block: implement reference count for BlockDriverState
Introduce bdrv_ref/bdrv_unref to manage the lifecycle of
BlockDriverState. They are unused for now but will used to replace
bdrv_delete() later.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:08 +02:00
Benoît Canet
cc0681c454 block: Enable the new throttling code in the block layer.
Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:07 +02:00
Max Reitz
afa50193cd qcow2-refcount: Repair shared refcount blocks
If the refcount of a refcount block is greater than one, we can at least
try to repair that problem by duplicating the affected block.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-02 10:06:59 +02:00
Alex Bligh
7483d1e547 aio / timers: convert block_job_sleep_ns and co_sleep_ns to new API
Convert block_job_sleep_ns and co_sleep_ns to use the new timer
API.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:14:24 +02:00
Alex Bligh
4e29e8311a aio / timers: Add aio_timer_init & aio_timer_new wrappers
Add aio_timer_init and aio_timer_new wrapper functions.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:10:28 +02:00
Alex Bligh
dae21b98b9 aio / timers: Add QEMUTimerListGroup to AioContext
Add a QEMUTimerListGroup each AioContext (meaning a QEMUTimerList
associated with each clock is added) and delete it when the
AioContext is freed.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:10:27 +02:00
Alex Bligh
6a1751b7aa aio / timers: Untangle include files
include/qemu/timer.h has no need to include main-loop.h and
doing so causes an issue for the next patch. Unfortunately
various files assume including timers.h will pull in main-loop.h.
Untangle this mess.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 19:10:27 +02:00
Asias He
0d51b4debe block: Introduce bs->zero_beyond_eof
In 4146b46c42e0989cb5842e04d88ab6ccb1713a48 (block: Produce zeros when
protocols reading beyond end of file), we break qemu-iotests ./check
-qcow2 022. This happens because qcow2 temporarily sets ->growable = 1
for vmstate accesses (which are stored beyond the end of regular image
data).

We introduce the bs->zero_beyond_eof to allow qcow2_load_vmstate() to
disable ->zero_beyond_eof temporarily in addition to enable ->growable.

[Since the broken patch "block: Produce zeros when protocols reading
beyond end of file" has not been merged yet, I have applied this fix
*first* and will then apply the next patch to keep the tree bisectable.
-- Stefan]

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 14:10:21 +02:00
Stefan Hajnoczi
f2e5dca46b aio: drop io_flush argument
The .io_flush() handler no longer exists and has no users.  Drop the
io_flush argument to aio_set_fd_handler() and related functions.

The AioFlushEventNotifierHandler and AioFlushHandler typedefs are no
longer used and are dropped too.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19 15:52:19 +02:00
Benoît Canet
b681a1c73e block: Repair the throttling code.
The throttling code was segfaulting since commit
02ffb50448 because some qemu_co_queue_next caller
does not run in a coroutine.
qemu_co_queue_do_restart assume that the caller is a coroutinne.
As suggested by Stefan fix this by entering the coroutine directly.
Also make sure like suggested that qemu_co_queue_next() and
qemu_co_queue_restart_all() can be called only in coroutines.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-07-29 17:07:37 +02:00
Ian Main
fc5d3f8432 Implement sync modes for drive-backup.
This patch adds sync-modes to the drive-backup interface and
implements the FULL, NONE and TOP modes of synchronization.

FULL performs as before copying the entire contents of the drive
while preserving the point-in-time using CoW.
NONE only copies new writes to the target drive.
TOP copies changes to the topmost drive image and preserves the
point-in-time using CoW.

For sync mode TOP are creating a new target image using the same backing
file as the original disk image.  Then any new data that has been laid
on top of it since creation is copied in the main backup_run() loop.
There is an extra check in the 'TOP' case so that we don't bother to copy
all the data of the backing file as it already exists in the target.
This is where the bdrv_co_is_allocated() is used to determine if the
data exists in the topmost layer or below.

Also any new data being written is intercepted via the write_notifier
hook which ends up calling backup_do_cow() to copy old data out before
it gets overwritten.

For mode 'NONE' we create the new target image and only copy in the
original data from the disk image starting from the time the call was
made.  This preserves the point in time data by only copying the parts
that are *going to change* to the target image.  This way we can
reconstruct the final image by checking to see if the given block exists
in the new target image first, and if it does not, you can get it from
the original image.  This is basically an optimization allowing you to
do point-in-time snapshots with low overhead vs the 'FULL' version.

Since there is no old data to copy out the loop in backup_run() for the
NONE case just calls qemu_coroutine_yield() which only wakes up after
an event (usually cancel in this case).  The rest is handled by the
before_write notifier which again calls backup_do_cow() to write out
the old data so it can be preserved.

Signed-off-by: Ian Main <imain@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-07-26 22:01:31 +02:00