Commit Graph

548 Commits

Author SHA1 Message Date
Kevin Wolf 0ebd24e0a2 blockdev: Don't disable COR automatically with blockdev-add
If a read-only device is configured with copy-on-read=on, the old code
only prints a warning and automatically disables copy on read. Make it
a real error for blockdev-add.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2013-10-11 16:50:02 +02:00
Kevin Wolf 8f94a6e40e block: Improve driver whitelist checks
The main intent of this patch is to consolidate the whitelist checks to
a single point in the code instead of spreading it everywhere. This adds
a nicer error message for read-only whitelisting, too, in places where
it was still missing.

The patch also contains a bonus bug fix: By finding the format first in
bdrv_open() and then independently checking against the whitelist only
later, we avoid the case that use of a non-whitelisted format results in
probing rather than an error message. Previously, this could happen when
using the driver=... option.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
2013-10-11 16:50:00 +02:00
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 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
Dunrong Huang d4cea8dfb9 block: use correct filename
The content filename point to may be erased by qemu_opts_absorb_qdict()
in raw_open_common() in drv->bdrv_file_open()

So it's better to use bs->filename.

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-10-07 13:23:19 +02:00
Dunrong Huang 2fa9aa59cf block: use correct filename for error report
The content filename point to will be erased by qemu_opts_absorb_qdict()
in raw_open_common() in drv->bdrv_file_open()

So it's better to use bs->filename.

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-10-02 11:41:50 +02:00
Fam Zheng d055a1fec3 block: use DIV_ROUND_UP in bdrv_co_do_readv
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-26 14:11:06 +02:00
Benoît Canet 5726d872f3 qdict: Extract qdict_extract_subqdict
Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 16:21:28 +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
Peter Lieven 1f9db2243c block/get_block_status: avoid segfault if there is no backing_hd
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 10:08:56 +02:00
Peter Lieven 3e0a233d86 block/get_block_status: set *pnum = 0 on error
if the call is invoked through bdrv_is_allocated the caller might
expect *pnum = 0 on error. however, a new implementation of
bdrv_get_block_status might only return a negative exit value on
error while keeping *pnum untouched.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 10:08:56 +02:00
Fam Zheng dbecebddfa block: fix backing file overriding
Providing backing.file.filename doesn't override backing file as expected:

    $ x86_64-softmmu/qemu-system-x86_64 -drive \
        file=/tmp/child.qcow2,backing.file.filename=/tmp/fake.qcow2

    qemu-system-x86_64: -drive \
        file=/tmp/child.qcow2,backing.file.filename=/tmp/fake.qcow2: could not
        open disk image /tmp/child.qcow2: Can't specify 'file' and 'filename'
        options at the same time

With

    $ qemu-img info /tmp/child.qcow2
    image: /tmp/child.qcow2
    file format: qcow2
    virtual size: 1.0G (1073741824 bytes)
    disk size: 196K
    cluster_size: 65536
    backing file: /tmp/fake.qcow2

This fixes it by calling bdrv_get_full_backing_filename only if
backing.file.filename is not provided. Also save the backing file name
to bs->backing_file so the information is correct with HMP "info block".

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-09-25 10:08:56 +02:00
Fam Zheng bcb9d66e85 block: don't lose data from last incomplete sector
To read the last sector that is not aligned to sector boundary, current
code for growable backends, since commit 893a8f6 "block: Produce zeros
when protocols reading beyond end of file", drops the data and directly
returns zeroes. That is incorrect.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-20 19:27:26 +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
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 5daa74a6eb block: look for zero blocks in bs->file
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 918e92d71b block: add default get_block_status implementation for protocols
Protocols return raw data, so you can assume the offsets to pass
through unchanged.

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 f0ad5712d5 block: return BDRV_BLOCK_ZERO past end of backing file
If the sectors are unallocated and we are past the end of the
backing file, they will read as zero.

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 415b5b013c block: use bdrv_has_zero_init to return BDRV_BLOCK_ZERO
Alternatively, this could use a "discard zeroes data" flag returned
by bdrv_get_info.

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 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 11212d8fa0 block: make bdrv_has_zero_init return false for copy-on-write-images
This helps implementing is_allocated on top of get_block_status.

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 d663640c04 block: expect errors from bdrv_co_is_allocated
Some bdrv_is_allocated callers do not expect errors, but the fallback
in qcow2.c might make other callers trip on assertion failures or
infinite loops.

Fix the callers to always look for errors.

Cc: qemu-stable@nongnu.org
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 617ccb466e block: do not use ->total_sectors in bdrv_co_is_allocated
This is more robust when the device has removable media.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-09-06 15:25:08 +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
Paolo Bonzini df2a6f29a5 block: keep bs->total_sectors up to date even for growable block devices
If a BlockDriverState is growable, after every write we need to
check if bs->total_sectors might have changed.  With this change,
bdrv_getlength does not need anymore a system call.

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
Kevin Wolf 09da4a7292 block: Remove redundant assertion
The failing condition is checked immediately before the assertion, so
keeping the assertion is kind of redundant.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-08-30 15:28:52 +02:00
Alex Bligh bc72ad6754 aio / timers: Switch entire codebase to the new timer API
This is an autogenerated patch using scripts/switch-timer-api.

Switch the entire code base to using the new timer API.

Note this patch may introduce some line length issues.

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
MORITA Kazutaka 893a8f6220 block: Produce zeros when protocols reading beyond end of file
While Asias is debugging an issue creating qcow2 images on top of
non-file protocols.  It boils down to this example using NBD:

$ qemu-io -c 'open -g nbd+unix:///?socket=/tmp/nbd.sock' -c 'read -v 0 512'

Notice the open -g option to set bs->growable.  This means you can
read/write beyond end of file.  Reading beyond end of file is supposed
to produce zeroes.

We rely on this behavior in qcow2_create2() during qcow2 image
creation.  We create a new file and then write the qcow2 header
structure using bdrv_pwrite().  Since QCowHeader is not a multiple of
sector size, block.c first uses bdrv_read() on the empty file to fetch
the first sector (should be all zeroes).

Here is the output from the qemu-io NBD example above:

$ qemu-io -c 'open -g nbd+unix:///?socket=/tmp/nbd.sock' -c 'read -v 0 512'
00000000:  ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab  ................
00000010:  ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab  ................
00000020:  ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab  ................
...

We are not zeroing the buffer!  As a result qcow2 image creation on top
of protocols is not guaranteed to work even when file creation is
supported by the protocol.

[Adapted this patch to use bs->zero_beyond_eof.
-- Stefan]

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-22 14:14:56 +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 88266f5aa7 block: stop relying on io_flush() in bdrv_drain_all()
If a block driver has no file descriptors to monitor but there are still
active requests, it can return 1 from .io_flush().  This is used to spin
during synchronous I/O.

Stop relying on .io_flush() and instead check
QLIST_EMPTY(&bs->tracked_requests) to decide whether there are active
requests.

This is the first step in removing .io_flush() so that event loops no
longer need to have the concept of synchronous I/O.  Eventually we may
be able to kill synchronous I/O completely by running everything in a
coroutine, but that is future work.

Note this patch moves bs->throttled_reqs initialization to bdrv_new() so
that bdrv_requests_pending(bs) can safely access it.  In practice bs is
g_malloc0() so the memory is already zeroed but it's safer to initialize
the queue properly.

We also need to fix up block/stream.c:close_unused_images() to prevent
traversing a dangling pointer while it rearranges the backing file
chain.  This is necessary since the new bdrv_drain_all() traverses the
backing file chain.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19 15:45:34 +02:00
Stefan Hajnoczi e1b5c52e04 block: ensure bdrv_drain_all() works during bdrv_delete()
In bdrv_delete() make sure to call bdrv_make_anon() *after* bdrv_close()
so that the device is still seen by bdrv_drain_all() when iterating
bdrv_states.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-08-19 15:45:34 +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
Kevin Wolf 74fe54f2a1 block: Allow "driver" option on the top level
This is traditionally -drive format=..., which is now translated into
the new driver option. This gives us a more consistent way to select the
driver of BlockDriverStates that can be used in QMP context, too.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2013-07-26 21:10:11 +02:00
Peter Lieven 4e7395e84f block: fix bdrv_read_unthrottled()
Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-07-19 12:29:22 +08:00
Peter Lieven 4105eaaab9 block: add bdrv_write_zeroes()
Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-07-19 12:29:21 +08:00
Kevin Wolf f0f0fdfeec block: Add return value for bdrv_flush_all()
bdrv_flush() can fail, and bdrv_flush_all() should return an error as
well if this happens for a block device. It returns the first error
return now, but still at least tries to flush the remaining devices even
in error cases.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-07-15 09:51:27 +02:00
Kevin Wolf 98289620e0 block: Don't parse protocol from file.filename
One of the major reasons for doing something new for -blockdev and
blockdev-add was that the old block layer code parses filenames instead
of just taking them literally. So we should really leave it untouched
when it's passing using the new interfaces (like -drive
file.filename=...).

This allows opening relative file names that contain a colon.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2013-07-15 09:49:00 +02:00
Stefan Hajnoczi 58fda173e1 block: fix bdrv_flush() ordering in bdrv_close()
Since 80ccf93b we flush the block device during close.  The
bdrv_drain_all() call should come before bdrv_flush() to ensure guest
write requests have completed.  Otherwise we may miss pending writes
when flushing.

Call bdrv_drain_all() again for safety as the final step after
bdrv_flush().  This should not be necessary but we can be paranoid here
in case bdrv_flush() left I/O pending.

Cc: qemu-stable@nongnu.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
2013-07-05 10:52:23 +02:00
Peter Lieven 3ac216270a block: change default of .has_zero_init to 0
.has_zero_init defaults to 1 for all formats and protocols.

this is a dangerous default since this means that all
new added drivers need to manually overwrite it to 0 if
they do not ensure that a device is zero initialized
after bdrv_create().

if a driver needs to explicitly set this value to
1 its easier to verify the correctness in the review process.

during review of the existing drivers it turned out
that ssh and gluster had a wrong default of 1.
both protocols support host_devices as backend
which are not by default zero initialized. this
wrong assumption will lead to possible corruption
if qemu-img convert is used to write to such a backend.

vpc and vmdk also defaulted to 1 altough they support
fixed respectively flat extends. this has to be addresses
in separate patches. both formats as well as the mentioned
ssh and gluster are turned to the default of 0 with this
patch for safety.

a similar problem with the wrong default existed for
iscsi most likely because the driver developer did
oversee the default value of 1.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-06-28 13:52:35 +02:00
Stefan Hajnoczi d616b22474 block: add bdrv_add_before_write_notifier()
The bdrv_add_before_write_notifier() function installs a callback that
is invoked before a write request is processed.  This will be used to
implement copy-on-write point-in-time snapshots where we need to copy
out old data before overwriting it.

Note that BdrvTrackedRequest is moved to block_int.h since it is passed
to .notify() functions.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-06-28 09:20:26 +02:00
Kevin Wolf 50b05b6f2e block: Always enable discard on the protocol level
Turning on discard options in qcow2 doesn't help a lot when the discard
requests that it issues are thrown away by the raw-posix layer. This
patch always enables discard functionality on the protocol level so that
it's the image format's responsibility to send (or not) discard
requests. Requests sent by the guest will be allowed or ignored by the
top level BlockDriverState, which depends on the discard=... option like
before.

In particular, this means that even without specifying options, the
qcow2 default of discarding deleted snapshots actually takes effect now,
both for qemu and qemu-img.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-06-24 10:25:17 +02:00