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2017-06-26block: change variable names in BlockDriverStateManos Pitsidianakis1-4/+4
Change the 'int count' parameter in *pwrite_zeros, *pdiscard related functions (and some others) to 'int bytes', as they both refer to bytes. This helps with code legibility. Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> Message-id: 20170609101808.13506-1-el13635@mail.ntua.gr Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-06-26qed: Use bdrv_co_* for coroutine_fnsKevin Wolf1-7/+9
All functions that are marked coroutine_fn can directly call the bdrv_co_* version of functions instead of going through the wrapper. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Manos Pitsidianakis <el13635@mail.ntua.gr> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add coroutine_fn to I/O path functionsKevin Wolf1-20/+24
Now that we stay in coroutine context for the whole request when doing reads or writes, we can add coroutine_fn annotations to many functions that can do I/O or yield directly. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Use a coroutine for need_check_timerKevin Wolf1-16/+17
This fixes the last place where we degraded from AIO to actual blocking synchronous I/O requests. Putting it into a coroutine means that instead of blocking, the coroutine simply yields while doing I/O. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Simplify request handlingKevin Wolf1-80/+21
Now that we process a request in the same coroutine from beginning to end and don't drop out of it any more, we can look like a proper coroutine-based driver and simply call qed_aio_next_io() and get a return value from it instead of spawning an additional coroutine that reenters the parent when it's done. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Use CoQueue for serialising allocationsKevin Wolf1-32/+17
Now that we're running in coroutine context, the ad-hoc serialisation code (which drops a request that has to wait out of coroutine context) can be replaced by a CoQueue. This means that when we resume a serialised request, it is running in coroutine context again and its I/O isn't blocking any more. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Implement .bdrv_co_readv/writevKevin Wolf1-55/+42
Most of the qed code is now synchronous and matches the coroutine model. One notable exception is the serialisation between requests which can still schedule a callback. Before we can replace this with coroutine locks, let's convert the driver's external interfaces to the coroutine versions. We need to be careful to handle both requests that call the completion callback directly from the calling coroutine (i.e. fully synchronous code) and requests that involve some callback, so that we need to yield and wait for the completion callback coming from outside the coroutine. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Manos Pitsidianakis <el13635@mail.ntua.gr> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove recursion in qed_aio_next_io()Kevin Wolf1-31/+32
Instead of calling itself recursively as the last thing, just convert qed_aio_next_io() into a loop. This patch is best reviewed with 'git show -w' because most of it is just whitespace changes. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove ret argument from qed_aio_next_io()Kevin Wolf1-11/+6
All callers pass ret = 0, so we can just remove it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_read/write_data()Kevin Wolf1-41/+31
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_write_inplace/alloc()Kevin Wolf1-23/+20
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_write_cow()Kevin Wolf1-37/+21
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. While refactoring qed_aio_write_alloc() to accomodate the change, qed_aio_write_zero_cluster() ended up with a single line, so I chose to inline that line and remove the function completely. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_write_main()Kevin Wolf1-25/+30
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_write_l2_update()Kevin Wolf1-17/+26
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Add return value to qed_aio_write_l1_update()Kevin Wolf1-10/+9
Don't recurse into qed_aio_next_io() and qed_aio_complete() here, but just return an error code and let the caller handle it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Inline qed_commit_l2_update()Kevin Wolf1-22/+14
qed_commit_l2_update() is unconditionally called at the end of qed_aio_write_l1_update(). Inline it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Make qed_aio_write_main() synchronousKevin Wolf1-42/+19
Note that this code is generally not running in coroutine context, so this is an actual blocking synchronous operation. We'll fix this in a moment. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Make qed_aio_read_data() synchronousKevin Wolf1-3/+5
Note that this code is generally not running in coroutine context, so this is an actual blocking synchronous operation. We'll fix this in a moment. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove callback from qed_write_table()Kevin Wolf1-5/+7
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove callback from qed_write_header()Kevin Wolf1-20/+12
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Make qed_write_header() synchronousKevin Wolf1-47/+29
Note that this code is generally not running in coroutine context, so this is an actual blocking synchronous operation. We'll fix this in a moment. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove callback from qed_copy_from_backing_file()Kevin Wolf1-34/+23
With this change, qed_aio_write_prefill() and qed_aio_write_postfill() collapse into a single function. This is reflected by a rename of the combined function to qed_aio_write_cow(). Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Make qed_copy_from_backing_file() synchronousKevin Wolf1-49/+29
Note that this code is generally not running in coroutine context, so this is an actual blocking synchronous operation. We'll fix this in a moment. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Make qed_read_backing_file() synchronousKevin Wolf1-14/+18
Note that this code is generally not running in coroutine context, so this is an actual blocking synchronous operation. We'll fix this in a moment. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Remove callback from qed_find_cluster()Kevin Wolf1-13/+11
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-06-26qed: Use bottom half to resume waiting requestsKevin Wolf1-3/+10
The qed driver serialises allocating write requests. When the active allocation is finished, the AIO callback is called, but after this, the next allocating request is immediately processed instead of leaving the coroutine. Resuming another allocation request in the same request coroutine means that the request now runs in the wrong coroutine. The following is one of the possible effects of this: The completed request will generally reenter its request coroutine in a bottom half, expecting that it completes the request in bdrv_driver_pwritev(). However, if the second request actually yielded before leaving the coroutine, the reused request coroutine is in an entirely different place and is reentered prematurely. Not a good idea. Let's make sure that we exit the coroutine after completing the first request by resuming the next allocating request only with a bottom half. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-05-18migration: migration.h was not neededJuan Quintela1-1/+0
This files don't use any function from migration.h, so drop it. Signed-off-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com>
2017-04-28block: Add .bdrv_truncate() error messagesMax Reitz1-1/+3
Add missing error messages for the block driver implementations of .bdrv_truncate(); drop the generic one from block.c's bdrv_truncate(). Since one of these changes touches a mis-indented block in block/file-posix.c, this patch fixes that coding style issue along the way. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170328205129.15138-5-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-28block: Add errp to BD.bdrv_truncate()Max Reitz1-1/+1
Add an Error parameter to the block drivers' bdrv_truncate() interface. If a block driver does not set this in case of an error, the generic bdrv_truncate() implementation will do so. Where it is obvious, this patch also makes some block drivers set this value. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170328205129.15138-4-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-28block: Add errp to b{lk,drv}_truncate()Max Reitz1-1/+1
For one thing, this allows us to drop the error message generation from qemu-img.c and blockdev.c and instead have it unified in bdrv_truncate(). Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170328205129.15138-3-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-02-28block: Add BDRV_O_RESIZE for blk_new_open()Kevin Wolf1-1/+2
blk_new_open() is a convenience function that processes flags rather than QDict options as a simple way to just open an image file. In order to keep it convenient in the future, it must automatically request the necessary permissions. This can easily be inferred from the flags for read and write, but we need another flag that tells us whether to get the resize permission. We can't just always request it because that means that no block jobs can run on the resulting BlockBackend (which is something that e.g. qemu-img commit wants to do), but we also can't request it never because most of the .bdrv_create() implementations call blk_truncate(). The solution is to introduce another flag that is passed by all users that want to resize the image. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Acked-by: Fam Zheng <famz@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
2017-02-28block: Request child permissions in format driversKevin Wolf1-0/+1
This makes use of the .bdrv_child_perm() implementation for formats that we just added. All format drivers expose the permissions they actually need nows, so that they can be set accordingly and updated when parents are attached or detached. The only format not included here is raw, which was already converted with the other filter drivers. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Fam Zheng <famz@redhat.com>
2017-02-24block: Attach bs->file only during .bdrv_open()Kevin Wolf1-3/+15
The way that attaching bs->file worked was a bit unusual in that it was the only child that would be attached to a node which is not opened yet. Because of this, the block layer couldn't know yet which permissions the driver would eventually need. This patch moves the point where bs->file is attached to the beginning of the individual .bdrv_open() implementations, so drivers already know what they are going to do with the child. This is also more consistent with how driver-specific children work. For a moment, bdrv_open() gets its own BdrvChild to perform image probing, but instead of directly assigning this BdrvChild to the BDS, it becomes a temporary one and the node name is passed as an option to the drivers, so that they can simply use bdrv_open_child() to create another reference for their own use. This duplicated child for (the not opened yet) bs is not the final state, a follow-up patch will change the image probing code to use a BlockBackend, which is completely independent of bs. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
2017-02-21block: explicitly acquire aiocontext in aio callbacks that need itPaolo Bonzini1-2/+2
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-16-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21block: explicitly acquire aiocontext in bottom halves that need itPaolo Bonzini1-0/+3
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-15-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21block: explicitly acquire aiocontext in timers that need itPaolo Bonzini1-0/+12
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-13-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21qed: introduce qed_aio_start_io and qed_aio_next_io_cbPaolo Bonzini1-14/+25
qed_aio_start_io and qed_aio_next_io will not have to acquire/release the AioContext, while qed_aio_next_io_cb will. Split the functionality and gain a little type-safety in the process. Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Message-id: 20170213135235.12274-11-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-10-28qed: Implement .bdrv_drainFam Zheng1-1/+15
The "need_check_timer" is used to clear the "NEED_CHECK" flag in the image header after a grace period once metadata update has finished. To comply with the bdrv_drain semantics, we should make sure it remains deleted once .bdrv_drain is called. The change to qed_need_check_timer_cb is needed because bdrv_qed_drain is called after s->bs has been drained, and should not operate on it; instead it should operate on the BdrvChild-ren exclusively. Doing so is easy because QED does not have a bdrv_co_flush_to_os callback, hence all that is needed to flush it is to ensure writes have reached the disk. Based on commit df9a681dc9a (which however included some unrelated hunks, possibly due to a merge failure or an overlooked squash). The patch was reverted because at the time bdrv_qed_drain could call qed_plug_allocating_write_reqs while an allocating write was queued. This however is not possible anymore after the previous patch; .bdrv_drain is only called after all writes have completed at the QED level, and its purpose is to trigger metadata writes in bs->file. Signed-off-by: Fam Zheng <famz@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <1477565348-5458-7-git-send-email-pbonzini@redhat.com> Signed-off-by: Fam Zheng <famz@redhat.com>
2016-10-07block: use aio_bh_schedule_oneshotPaolo Bonzini1-4/+2
This simplifies bottom half handlers by removing calls to qemu_bh_delete and thus removing the need to stash the bottom half pointer in the opaque datum. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-13coroutine: move entry argument to qemu_coroutine_createPaolo Bonzini1-2/+2
In practice the entry argument is always known at creation time, and it is confusing that sometimes qemu_coroutine_enter is used with a non-NULL argument to re-enter a coroutine (this happens in block/sheepdog.c and tests/test-coroutine.c). So pass the opaque value at creation time, for consistency with e.g. aio_bh_new. Mostly done with the following semantic patch: @ entry1 @ expression entry, arg, co; @@ - co = qemu_coroutine_create(entry); + co = qemu_coroutine_create(entry, arg); ... - qemu_coroutine_enter(co, arg); + qemu_coroutine_enter(co); @ entry2 @ expression entry, arg; identifier co; @@ - Coroutine *co = qemu_coroutine_create(entry); + Coroutine *co = qemu_coroutine_create(entry, arg); ... - qemu_coroutine_enter(co, arg); + qemu_coroutine_enter(co); @ entry3 @ expression entry, arg; @@ - qemu_coroutine_enter(qemu_coroutine_create(entry), arg); + qemu_coroutine_enter(qemu_coroutine_create(entry, arg)); @ reentry @ expression co; @@ - qemu_coroutine_enter(co, NULL); + qemu_coroutine_enter(co); except for the aforementioned few places where the semantic patch stumbled (as expected) and for test_co_queue, which would otherwise produce an uninitialized variable warning. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-05block: Convert bdrv_pwrite(v/_sync) to BdrvChildKevin Wolf1-2/+2
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-07-05block: Convert bdrv_pread(v) to BdrvChildKevin Wolf1-3/+3
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-07-05block: Convert bdrv_aio_writev() to BdrvChildKevin Wolf1-3/+3
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-07-05block: Convert bdrv_aio_readv() to BdrvChildKevin Wolf1-3/+3
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-06-08qed: Convert to bdrv_co_pwrite_zeroes()Eric Blake1-18/+15
Another step on our continuing quest to switch to byte-based interfaces. Kill an abuse of the comma operator while at it (fortunately, the semantics were still right). Also, the test for requests not aligned to clusters should be applied always, not just when a backing file is present. Signed-off-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-06-08block: Track write zero limits in bytesEric Blake1-1/+1
Another step towards removing sector-based interfaces: convert the maximum write and minimum alignment values from sectors to bytes. Rename the variables to let the compiler check that all users are converted to the new semantics. The maximum remains an int as long as BDRV_REQUEST_MAX_SECTORS is constrained by INT_MAX (this means that we can't even support a 2G write_zeroes, but just under it) - changing operation lengths to unsigned or to 64-bits is a much bigger audit, and debatable if we even want to do it (since at the core, a 32-bit platform will still have ssize_t as its underlying limit on write()). Meanwhile, alignment is changed to 'uint32_t', since it makes no sense to have an alignment larger than the maximum write, and less painful to use an unsigned type with well-defined behavior in bit operations than to have to worry about what happens if a driver mistakenly supplies a negative alignment. Add an assert that no one was trying to use sectors to get a write zeroes larger than 2G, and therefore that a later conversion to bytes won't be impacted by keeping the limit at 32 bits. Signed-off-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-06-07qed: Use DIV_ROUND_UPLaurent Vivier1-2/+1
Replace (((n) + (d) - 1) /(d)) by DIV_ROUND_UP(n,d). This patch is the result of coccinelle script scripts/coccinelle/round.cocci CC: qemu-block@nongnu.org Signed-off-by: Laurent Vivier <lvivier@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
2016-05-19qemu-common: stop including qemu/bswap.h from qemu-common.hPaolo Bonzini1-0/+1
Move it to the actual users. There are still a few includes of qemu/bswap.h in headers; removing them is left for future work. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-05-12block: Drop superfluous invalidating bs->file from driversFam Zheng1-6/+0
Now they are invalidated by the block layer, so it's not necessary to do this in block drivers' implementations of .bdrv_invalidate_cache. Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-05-12block: Allow BDRV_REQ_FUA through blk_pwrite()Eric Blake1-3/+3
We have several block drivers that understand BDRV_REQ_FUA, and emulate it in the block layer for the rest by a full flush. But without a way to actually request BDRV_REQ_FUA during a pass-through blk_pwrite(), FUA-aware block drivers like NBD are forced to repeat the emulation logic of a full flush regardless of whether the backend they are writing to could do it more efficiently. This patch just wires up a flags argument; followup patches will actually make use of it in the NBD driver and in qemu-io. Signed-off-by: Eric Blake <eblake@redhat.com> Acked-by: Denis V. Lunev <den@openvz.org> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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