Another step towards byte-based interfaces everywhere.  Replace
the sector-based bdrv_co_discard() with a new byte-based
bdrv_co_pdiscard(), which silently ignores any unaligned head
or tail.  Driver callbacks will be converted in followup patches.

By calculating the alignment outside of the loop, and clamping
the max discard to an aligned value, we can simplify the actions
done within the loop.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1468624988-423-2-git-send-email-eblake@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

The rerror/werror policies are implemented in the devices, so that's
where they should be configured. In comparison to the old options in
-drive, the qdev properties are only added to those devices that
actually support them.

If the option isn't given (or "auto" is specified), the setting of the
BlockBackend is used for compatibility with the old options. For block
jobs, "auto" is the same as "enospc".
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

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: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This is the final patch for converting the common I/O path to take
a BdrvChild parameter instead of BlockDriverState.

The completion of this conversion means that all users that perform I/O
on an image need to actually hold a reference (in the form of BdrvChild,
possible as part of a BlockBackend) to that image. This also protects
against inconsistent use of BlockBackend vs. BlockDriverState functions
because direct use of a BlockDriverState isn't possible any more and
blk->root is private for block-backends.c.

In addition, we can now distinguish different users in the I/O path,
and the future op blockers work is going to add assertions based on
permissions stored in BdrvChild.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Sector-based limits are awkward to think about; in our on-going
quest to move to byte-based interfaces, convert max_transfer_length
and opt_transfer_length.  Rename them (dropping the _length suffix)
so that the compiler will help us catch the change in semantics
across any rebased code, and improve the documentation.  Use unsigned
values, so that we don't have to worry about negative values and
so that bit-twiddling is easier; however, we are still constrained
by 2^31 of signed int in most APIs.

When a value comes from an external source (iscsi and raw-posix),
sanitize the results to ensure that opt_transfer is a power of 2.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Making all callers special-case 0 as unlimited is awkward,
and we DO have a hard maximum of BDRV_REQUEST_MAX_SECTORS given
our current block layer API limits.

In the case of scsi, this means that we now always advertise a
limit to the guest, even in cases where the underlying layers
previously use 0 for no inherent limit beyond the block layer.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Also add trace points now that the function can be directly called.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>

The existing users of the function are:

1. blk_new_open(), which already enabled the write cache
2. Some test cases that don't care about the setting
3. blockdev_init() for empty drives, where the cache mode is overridden
   with the value from the options when a medium is inserted

Therefore, this patch doesn't change the current behaviour. It will be
convenient, however, for additional users of blk_new() (like block
jobs) if the most sensible WCE setting is the default.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>

Commit 983a1600 changed the semantics of blk_write_zeroes() to
be byte-based rather than sector-based, but did not change the
name, which is an open invitation for other code to misuse the
function.  Renaming to pwrite_zeroes() makes it more in line
with other byte-based interfaces, and will help make it easier
to track which remaining write_zeroes interfaces still need
conversion.
Reported-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

When changing the BlockDriverState that a BdrvChild points to while the
node is currently drained, we must call the .drained_end() parent
callback. Conversely, when this means attaching a new node that is
already drained, we need to call .drained_begin().

bdrv_root_attach_child() takes now an opaque parameter, which is needed
because the callbacks must also be called if we're attaching a new child
to the BlockBackend when the root node is already drained, and they need
a way to identify the BlockBackend. Previously, child->opaque was set
too late and the callbacks would still see it as NULL.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>

blk_new() cannot fail so its Error ** parameter has become superfluous.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

There are no callers to bdrv_open() or bdrv_open_inherit() left that
pass a pointer to a non-NULL BDS pointer as the first argument of these
functions, so we can finally drop that parameter and just make them
return the new BDS.

Generally, the following pattern is applied:

    bs = NULL;
    ret = bdrv_open(&bs, ..., &local_err);
    if (ret < 0) {
        error_propagate(errp, local_err);
        ...
    }

by

    bs = bdrv_open(..., errp);
    if (!bs) {
        ret = -EINVAL;
        ...
    }

Of course, there are only a few instances where the pattern is really
pure.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Its only caller is blk_new_open(), so we can just inline it there.

The bdrv_new_root() call is dropped in the process because we can just
let bdrv_open() create the BDS.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

The bdrv_next() users all leaked the BdrvNextIterator after completing
the iteration. Simply changing bdrv_next() to free the iterator before
returning NULL at the end of list doesn't work because some callers exit
the loop before looking at all BDSes.

This patch moves the BdrvNextIterator from the heap to the stack of
the caller and switches to a bdrv_first()/bdrv_next() interface for
initialising the iterator.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>

This patch removes the remaining users of bs->blk, which will allow us
to have multiple BBs on top of a single BDS. In the meantime, all checks
that are currently in place to prevent the user from creating such
setups can be switched to bdrv_has_blk() instead of accessing BDS.blk.

Future patches can allow them and e.g. enable users to mirror to a block
device that already has a BlockBackend on it.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

We need to introduce a separate BdrvNextIterator struct that can keep
more state than just the current BDS in order to avoid using the bs->blk
pointer.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

In many cases we just want to know whether a BDS has at least one BB
attached, without needing to know the exact BB that is attached. In
contrast to bs->blk, this is still a valid question when more than one
BB can be attached, so just answer it by checking the parents list.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

Since virtio-blk implements request merging itself these days, the only
remaining users are test cases for the function. That doesn't make the
function exactly useful any more.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

In order to get rid of bs->blk for bdrv_get_device_name() and
bdrv_get_device_or_node_name(), ask all parents for their name and
simply pick the first one.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

We want to get rid of BlockDriverState.blk in order to allow multiple
BlockBackends per BDS. Converting the device callbacks in block.c (which
assume a single BlockBackend) to per-child callbacks gets us rid of the
first few instances.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

This moves the throttling related part of the BDS life cycle management
to BlockBackend. The throttling group reference is now kept even when no
medium is inserted.

With this commit, throttling isn't disabled and then re-enabled any more
during graph reconfiguration. This fixes the temporary breakage of I/O
throttling when used with live snapshots or block jobs that manipulate
the graph.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

This removes the last part of I/O throttling from block/io.c and moves
it to the BlockBackend.

Instead of having knowledge about throttling inside io.c, we can call a
BdrvChild callback .drained_begin/end, which happens to drain the
throttled requests for BlockBackend parents.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

BlockBackends use it to get a back pointer from BdrvChild to
BlockBackend in any BdrvChildRole callbacks.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

This patch changes where the throttling state is stored (used to be the
BlockDriverState, now it is the BlockBackend), but it doesn't actually
make it a BB level feature yet. For example, throttling is still
disabled when the BDS is detached from the BB.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Some features, like I/O throttling, are implemented outside
block-backend.c, but still want to keep information in BlockBackend,
e.g. list entries that allow keeping a list of BlockBackends.

In order to avoid exposing the whole struct layout in the public header
file, this patch introduces an embedded public struct where such
information can be added and a pair of functions to convert between
BlockBackend and BlockBackendPublic.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

It was already true in principle that a throttled BDS always has a BB
attached, except that the order of operations while attaching or
detaching a BDS to/from a BB wasn't careful enough.

This commit breaks graph manipulations while I/O throttling is enabled.
It would have been possible to keep things working with some temporary
hacks, but quite cumbersome, so it's not worth the hassle. We'll fix
things again in a minute.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>

Now that there are no remaining clients, we can drop the
sector-based blk_read(), blk_write(), blk_aio_readv(), and
blk_aio_writev().  Sadly, there are still remaining
sector-based interfaces, such as blk_*discard(), or
blk_write_compressed(); those will have to wait for another
day.
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

blk_aio_readv() and blk_aio_writev() are annoying in that they
can't access sub-sector granularity, and cannot pass flags.
Also, they require the caller to pass redundant information
about the size of the I/O (qiov->size in bytes must match
nb_sectors in sectors).

Add new blk_aio_preadv() and blk_aio_pwritev() functions to fix
the flaws. The next few patches will upgrade callers, then
finally delete the old interfaces.
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Sector-based blk_write() should die; convert the one-off
variant blk_write_zeroes() to use an offset/count interface
instead.  Likewise for blk_co_write_zeroes() and
blk_aio_write_zeroes().
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Sector-based blk_read() should die; convert the one-off
variant blk_read_unthrottled().
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

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: NEric Blake <eblake@redhat.com>
Acked-by: NDenis V. Lunev <den@openvz.org>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

It used to be an internal helper function just for implementing
bdrv_co_do_readv/writev(), but now that it's a public interface, it
deserves a name without "do" in it.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>

Extract the handling of throttling from bdrv_flush_io_queue.  These
new functions will soon become BdrvChildRole callbacks, as they can
be generalized to "beginning of drain" and "end of drain".
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Commit 57d6a428 neglected to pass the given flags to blk_aio_prwv(),
which broke discard by WRITE SAME for scsi-disk (the UNMAP bit would be
ignored).

Commit fc1453cd introduced the same bug for blk_write_zeroes(). This is
used for 'qemu-img convert' without has_zero_init (e.g. on a block
device) and for preallocation=falloc in parallels.

Commit 8896e088 is the version for blk_co_write_zeroes(). This function
is only used in qemu-io.
Reported-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

Commit 57d6a428 broke blk_aio_write_zeroes() because in some write
functions in the call path don't have an explicit length argument but
reuse qiov->size instead. Which is great, except that write_zeroes
doesn't have a qiov, which this commit interprets as 0 bytes.
Consequently, blk_aio_write_zeroes() didn't effectively do anything.

This patch introduces an explicit acb->bytes in BlkAioEmAIOCB and uses
that instead of acb->rwco.size.

The synchronous version of the function is okay because it does pass a
qiov (with the right size and a NULL pointer as its base).
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>

The previous patches have successively made blk->enable_write_cache the
true source for the information whether a writethrough mode must be
implemented. The corresponding BDRV_O_CACHE_WB is only useless baggage
we're carrying around, so now's the time to remove it.

At the same time, we remove the 'cache.writeback' option parsing on the
BDS level as the only effect was setting the BDRV_O_CACHE_WB flag.

This change requires test cases that explicitly enabled the option to
drop it. Other than that and the change of the error message when
writethrough is enabled on the BDS level (from "Can't set writethrough
mode" to "doesn't support the option"), there should be no change in
behaviour.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>