The new AioPollFn io_poll() argument to aio_set_fd_handler() and
aio_set_event_handler() is used in the next patch.

Keep this code change separate due to the number of files it touches.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 20161201192652.9509-3-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Commit 0ed93d84 ("linux-aio: process
completions from ioq_submit()") added an optimization that processes
completions each time ioq_submit() returns with requests in flight.
This commit introduces a "Co-routine re-entered recursively" error which
can be triggered with -drive format=qcow2,aio=native.

Fam Zheng <famz@redhat.com>, Kevin Wolf <kwolf@redhat.com>, and I
debugged the following backtrace:

  (gdb) bt
  #0  0x00007ffff0a046f5 in raise () at /lib64/libc.so.6
  #1  0x00007ffff0a062fa in abort () at /lib64/libc.so.6
  #2  0x0000555555ac0013 in qemu_coroutine_enter (co=0x5555583464d0) at util/qemu-coroutine.c:113
  #3  0x0000555555a4b663 in qemu_laio_process_completions (s=s@entry=0x555557e2f7f0) at block/linux-aio.c:218
  #4  0x0000555555a4b874 in ioq_submit (s=s@entry=0x555557e2f7f0) at block/linux-aio.c:331
  #5  0x0000555555a4ba12 in laio_do_submit (fd=fd@entry=13, laiocb=laiocb@entry=0x555559d38ae0, offset=offset@entry=2932727808, type=type@entry=1) at block/linux-aio.c:383
  #6  0x0000555555a4bbd3 in laio_co_submit (bs=<optimized out>, s=0x555557e2f7f0, fd=13, offset=2932727808, qiov=0x555559d38e20, type=1) at block/linux-aio.c:402
  #7  0x0000555555a4fd23 in bdrv_driver_preadv (bs=bs@entry=0x55555663bcb0, offset=offset@entry=2932727808, bytes=bytes@entry=8192, qiov=qiov@entry=0x555559d38e20, flags=0) at block/io.c:804
  #8  0x0000555555a52b34 in bdrv_aligned_preadv (bs=bs@entry=0x55555663bcb0, req=req@entry=0x555559d38d20, offset=offset@entry=2932727808, bytes=bytes@entry=8192, align=align@entry=512, qiov=qiov@entry=0x555559d38e20, flags=0) at block/io.c:1041
  #9  0x0000555555a52db8 in bdrv_co_preadv (child=<optimized out>, offset=2932727808, bytes=8192, qiov=qiov@entry=0x555559d38e20, flags=flags@entry=0) at block/io.c:1133
  #10 0x0000555555a29629 in qcow2_co_preadv (bs=0x555556635890, offset=6178725888, bytes=8192, qiov=0x555557527840, flags=<optimized out>) at block/qcow2.c:1509
  #11 0x0000555555a4fd23 in bdrv_driver_preadv (bs=bs@entry=0x555556635890, offset=offset@entry=6178725888, bytes=bytes@entry=8192, qiov=qiov@entry=0x555557527840, flags=0) at block/io.c:804
  #12 0x0000555555a52b34 in bdrv_aligned_preadv (bs=bs@entry=0x555556635890, req=req@entry=0x555559d39000, offset=offset@entry=6178725888, bytes=bytes@entry=8192, align=align@entry=1, qiov=qiov@entry=0x555557527840, flags=0) at block/io.c:1041
  #13 0x0000555555a52db8 in bdrv_co_preadv (child=<optimized out>, offset=offset@entry=6178725888, bytes=bytes@entry=8192, qiov=qiov@entry=0x555557527840, flags=flags@entry=0) at block/io.c:1133
  #14 0x0000555555a4515a in blk_co_preadv (blk=0x5555566356d0, offset=6178725888, bytes=8192, qiov=0x555557527840, flags=0) at block/block-backend.c:783
  #15 0x0000555555a45266 in blk_aio_read_entry (opaque=0x5555577025e0) at block/block-backend.c:991
  #16 0x0000555555ac0cfa in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:78

It turned out that re-entrant ioq_submit() and completion processing
between three requests caused this error.  The following check is not
sufficient to prevent recursively entering coroutines:

  if (laiocb->co != qemu_coroutine_self()) {
      qemu_coroutine_enter(laiocb->co);
  }

As the following coroutine backtrace shows, not just the current
coroutine (self) can be entered.  There might also be other coroutines
that are currently entered and transferred control due to the qcow2 lock
(CoMutex):

  (gdb) qemu coroutine 0x5555583464d0
  #0  0x0000555555ac0c90 in qemu_coroutine_switch (from_=from_@entry=0x5555583464d0, to_=to_@entry=0x5555572f9890, action=action@entry=COROUTINE_ENTER) at util/coroutine-ucontext.c:175
  #1  0x0000555555abfe54 in qemu_coroutine_enter (co=0x5555572f9890) at util/qemu-coroutine.c:117
  #2  0x0000555555ac031c in qemu_co_queue_run_restart (co=co@entry=0x5555583462c0) at util/qemu-coroutine-lock.c:60
  #3  0x0000555555abfe5e in qemu_coroutine_enter (co=0x5555583462c0) at util/qemu-coroutine.c:119
  #4  0x0000555555a4b663 in qemu_laio_process_completions (s=s@entry=0x555557e2f7f0) at block/linux-aio.c:218
  #5  0x0000555555a4b874 in ioq_submit (s=s@entry=0x555557e2f7f0) at block/linux-aio.c:331
  #6  0x0000555555a4ba12 in laio_do_submit (fd=fd@entry=13, laiocb=laiocb@entry=0x55555a338b40, offset=offset@entry=2911477760, type=type@entry=1) at block/linux-aio.c:383
  #7  0x0000555555a4bbd3 in laio_co_submit (bs=<optimized out>, s=0x555557e2f7f0, fd=13, offset=2911477760, qiov=0x55555a338e80, type=1) at block/linux-aio.c:402
  #8  0x0000555555a4fd23 in bdrv_driver_preadv (bs=bs@entry=0x55555663bcb0, offset=offset@entry=2911477760, bytes=bytes@entry=8192, qiov=qiov@entry=0x55555a338e80, flags=0) at block/io.c:804
  #9  0x0000555555a52b34 in bdrv_aligned_preadv (bs=bs@entry=0x55555663bcb0, req=req@entry=0x55555a338d80, offset=offset@entry=2911477760, bytes=bytes@entry=8192, align=align@entry=512, qiov=qiov@entry=0x55555a338e80, flags=0) at block/io.c:1041
  #10 0x0000555555a52db8 in bdrv_co_preadv (child=<optimized out>, offset=2911477760, bytes=8192, qiov=qiov@entry=0x55555a338e80, flags=flags@entry=0) at block/io.c:1133
  #11 0x0000555555a29629 in qcow2_co_preadv (bs=0x555556635890, offset=6157475840, bytes=8192, qiov=0x5555575df720, flags=<optimized out>) at block/qcow2.c:1509
  #12 0x0000555555a4fd23 in bdrv_driver_preadv (bs=bs@entry=0x555556635890, offset=offset@entry=6157475840, bytes=bytes@entry=8192, qiov=qiov@entry=0x5555575df720, flags=0) at block/io.c:804
  #13 0x0000555555a52b34 in bdrv_aligned_preadv (bs=bs@entry=0x555556635890, req=req@entry=0x55555a339060, offset=offset@entry=6157475840, bytes=bytes@entry=8192, align=align@entry=1, qiov=qiov@entry=0x5555575df720, flags=0) at block/io.c:1041
  #14 0x0000555555a52db8 in bdrv_co_preadv (child=<optimized out>, offset=offset@entry=6157475840, bytes=bytes@entry=8192, qiov=qiov@entry=0x5555575df720, flags=flags@entry=0) at block/io.c:1133
  #15 0x0000555555a4515a in blk_co_preadv (blk=0x5555566356d0, offset=6157475840, bytes=8192, qiov=0x5555575df720, flags=0) at block/block-backend.c:783
  #16 0x0000555555a45266 in blk_aio_read_entry (opaque=0x555557231aa0) at block/block-backend.c:991
  #17 0x0000555555ac0cfa in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:78

Use the new qemu_coroutine_entered() function instead of comparing
against qemu_coroutine_self().  This is correct because:

1. If a coroutine is not entered then it must have yielded to wait for
   I/O completion.  It is therefore safe to enter.

2. If a coroutine is entered then it must be in
   ioq_submit()/qemu_laio_process_completions() because otherwise it
   would be yielded while waiting for I/O completion.  Therefore it will
   check laio->ret and return from ioq_submit() instead of yielding,
   i.e. it's guaranteed not to hang.
Reported-by: NFam Zheng <famz@redhat.com>
Tested-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Message-id: 1474989516-18255-4-git-send-email-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

In order to reduce completion latency it makes sense to harvest completed
requests ASAP.  Very fast backend device can complete requests just after
submission, so it is worth trying to check ring buffer in order to peek
completed requests directly after io_submit() has been called.

Indeed, this patch reduces the completions latencies and increases the
overall throughput, e.g. the following is the percentiles of number of
completed requests at once:

        1th 10th  20th  30th  40th  50th  60th  70th  80th  90th  99.99th
Before    2    4    42   112   128   128   128   128   128   128    128
 After    1    1     4    14    33    45    47    48    50    51    108

That means, that before the current patch is applied the ring buffer is
observed as full (128 requests were consumed at once) in 60% of calls.

After patch is applied the distribution of number of completed requests
is "smoother" and the queue (requests in-flight) is almost never full.

The fio read results are the following (write results are almost the
same and are not showed here):

  Before
  ------
job: (groupid=0, jobs=8): err= 0: pid=2227: Tue Jul 19 11:29:50 2016
  Description  : [Emulation of Storage Server Access Pattern]
  read : io=54681MB, bw=1822.7MB/s, iops=179779, runt= 30001msec
    slat (usec): min=172, max=16883, avg=338.35, stdev=109.66
    clat (usec): min=1, max=21977, avg=1051.45, stdev=299.29
     lat (usec): min=317, max=22521, avg=1389.83, stdev=300.73
    clat percentiles (usec):
     |  1.00th=[  346],  5.00th=[  596], 10.00th=[  708], 20.00th=[  852],
     | 30.00th=[  932], 40.00th=[  996], 50.00th=[ 1048], 60.00th=[ 1112],
     | 70.00th=[ 1176], 80.00th=[ 1256], 90.00th=[ 1384], 95.00th=[ 1496],
     | 99.00th=[ 1800], 99.50th=[ 1928], 99.90th=[ 2320], 99.95th=[ 2672],
     | 99.99th=[ 4704]
    bw (KB  /s): min=205229, max=553181, per=12.50%, avg=233278.26, stdev=18383.51

  After
  ------
job: (groupid=0, jobs=8): err= 0: pid=2220: Tue Jul 19 11:31:51 2016
  Description  : [Emulation of Storage Server Access Pattern]
  read : io=57637MB, bw=1921.2MB/s, iops=189529, runt= 30002msec
    slat (usec): min=169, max=20636, avg=329.61, stdev=124.18
    clat (usec): min=2, max=19592, avg=988.78, stdev=251.04
     lat (usec): min=381, max=21067, avg=1318.42, stdev=243.58
    clat percentiles (usec):
     |  1.00th=[  310],  5.00th=[  580], 10.00th=[  748], 20.00th=[  876],
     | 30.00th=[  908], 40.00th=[  948], 50.00th=[ 1012], 60.00th=[ 1064],
     | 70.00th=[ 1080], 80.00th=[ 1128], 90.00th=[ 1224], 95.00th=[ 1288],
     | 99.00th=[ 1496], 99.50th=[ 1608], 99.90th=[ 1960], 99.95th=[ 2256],
     | 99.99th=[ 5408]
    bw (KB  /s): min=212149, max=390160, per=12.49%, avg=245746.04, stdev=11606.75

Throughput increased from 1822MB/s to 1921MB/s, average completion latencies
decreased from 1051us to 988us.
Signed-off-by: NRoman Pen <roman.penyaev@profitbricks.com>
Message-id: 1468931263-32667-4-git-send-email-roman.penyaev@profitbricks.com
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Prepare processing events function to be called from ioq_submit(),
thus split function on two parts: the first harvests completed IO
requests, the second submits pending requests.
Signed-off-by: NRoman Pen <roman.penyaev@profitbricks.com>
Message-id: 1468931263-32667-3-git-send-email-roman.penyaev@profitbricks.com
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

AIO context in userspace is represented as a simple ring buffer, which
can be consumed directly without entering the kernel, which obviously
can bring some performance gain.  QEMU does not use timeout value for
waiting for events completions, so we can consume all events from
userspace.
Signed-off-by: NRoman Pen <roman.penyaev@profitbricks.com>
Message-id: 1468931263-32667-2-git-send-email-roman.penyaev@profitbricks.com
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

It is generally not expected that io_submit() fails other than with
-EAGAIN, but corner cases like SELinux refusing I/O when permissions are
revoked are still possible. In this case, we shouldn't abort, but just
return an I/O error for the request.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1470741619-23231-1-git-send-email-kwolf@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Invoking io_setup(MAX_EVENTS) we ask kernel to create ring buffer for us
with specified number of events.  But kernel ring buffer allocation logic
is a bit tricky (ring buffer is page size aligned + some percpu allocation
are required) so eventually more than requested events number is allocated.

From a userspace side we have to follow the convention and should not try
to io_submit() more or logic, which consumes completed events, should be
changed accordingly.  The pitfall is in the following sequence:

    MAX_EVENTS = 128
    io_setup(MAX_EVENTS)

    io_submit(MAX_EVENTS)
    io_submit(MAX_EVENTS)

    /* now 256 events are in-flight */

    io_getevents(MAX_EVENTS) = 128

    /* we can handle only 128 events at once, to be sure
     * that nothing is pended the io_getevents(MAX_EVENTS)
     * call must be invoked once more or hang will happen. */

To prevent the hang or reiteration of io_getevents() call this patch
restricts the number of in-flights, which is now limited to MAX_EVENTS.
Signed-off-by: NRoman Pen <roman.penyaev@profitbricks.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1468415004-31755-1-git-send-email-roman.penyaev@profitbricks.com
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel@nongnu.org
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

This has better performance because it executes fewer system calls
and does not use a bottom half per disk.

Originally proposed by Ming Lei.

[Changed #include "raw-aio.h" to "block/raw-aio.h" in win32-aio.c to fix
build error as reported by Peter Maydell <peter.maydell@linaro.org>.
--Stefan]
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1467650000-51385-1-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

squash! linux-aio: share one LinuxAioState within an AioContext

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>

Partial write most likely means that there is not space rather than
"something wrong happens". Thus it would be more natural to return
ENOSPC rather than EINVAL.

The problem actually happens with NBD server, which has reported EINVAL
rather then ENOSPC on the first error using its protocol, which makes
report to the user wrong.
Signed-off-by: NDenis V. Lunev <den@openvz.org>
CC: Pavel Borzenkov <pborzenkov@virtuozzo.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

linux-aio uses a BH in order to make sure that the remaining completions
are processed even in nested event loops of completion callbacks in
order to avoid deadlocks.

There is no need, however, to have the BH overhead for the first call
into qemu_laio_completion_bh() or after all pending completions have
already been processed. Therefore, this patch calls directly into
qemu_laio_completion_bh() in qemu_laio_completion_cb() and cancels
the BH after qemu_laio_completion_bh() has processed all pending
completions.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>

The raw-posix block driver actually supports byte-aligned requests now
on non-O_DIRECT images, like it already (and previously incorrectly)
claimed in bs->request_alignment.

For some block drivers this means that a RMW cycle can be avoided when
they write sub-sector metadata e.g. for cluster allocation.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

In order to use the modern byte-based .bdrv_co_preadv/pwritev()
interface, this patch switches raw-posix to coroutine-based interfaces
as a first step. In terms of semantics and performance, it doesn't make
a difference with the existing code whether we go from a coroutine to a
callback-based interface already in block/io.c or only in linux-aio.c

As there have been concerns in the past that this change may be a step
in the wrong direction with respect to a possible AIO fast path, the
old callback-based interface for linux-aio is left around and can be
reactivated when a fast path (e.g. directly from virtio-blk dataplane,
bypassing the whole block layer) is implemented.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>

Replace void* with an opaque LinuxAioState type.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Extract the handling of io_plug "depth" from linux-aio.c and let the
main bdrv_drain loop do nothing but wait on I/O.

Like the two newly introduced functions, bdrv_io_plug and bdrv_io_unplug
now operate on all children.  The visit order is now symmetrical between
plug and unplug, making it possible for formats to implement plug/unplug.
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Acked-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.

This commit was created with scripts/clean-includes.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

All callers pass in false, and the real external ones will switch to
true in coming patches.
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

There is no need to do another O(n) pass on the list; the iocb to
split the list at is already available through the array we passed to
io_submit.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-6-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

These are unused.
Suggested-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-5-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

It does not identify an index in an array anymore.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-4-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Avoid that unplug submits requests when io_submit reported that it
couldn't accept more; at the same time, try more io_submit calls if it
could handle the whole set of requests that were passed, so that the
"blocked" flag is reset as soon as possible.

After the previous patch, laio_submit already tried to avoid submitting
requests to a blocked queue, by comparing s->io_q.idx with "==" instead
of the more natural ">=".  Switch to the simpler expression now that we
have the "blocked" flag.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-3-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Keep a queue of requests that were not submitted; pass them to
the kernel when a completion is reported, unless the queue is
plugged.

The array of iocbs is rebuilt every time from scratch.  This
avoids keeping the iocbs array and list synchronized.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Message-id: 1418305950-30924-2-git-send-email-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

I'll use it with block backends shortly, and the name is going to fit
badly there.  It's a block layer thing anyway, not just a block driver
thing.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

I'll use BlockDriverAIOCB with block backends shortly, and the name is
going to fit badly there.  It's a block layer thing anyway, not just a
block driver thing.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Suggested-by: NBenoît Canet <benoit.canet@irqsave.net>
Signed-off-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Just call io_cancel (2), if it fails, it means the request is not
canceled, so the event loop will eventually call
qemu_laio_process_completion.

In qemu_laio_process_completion, change to call the cb unconditionally.
It is required by bdrv_aio_cancel_async.
Signed-off-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

If two Linux AIO request completions are fetched in the same
io_getevents() call, QEMU will deadlock if request A's callback waits
for request B to complete using an aio_poll() loop.  This was reported
to happen with the mirror blockjob.

This patch moves completion processing into a BH and makes it resumable.
Nested event loops can resume completion processing so that request B
will complete and the deadlock will not occur.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Marcin Gibuła <m.gibula@beyond.pl>
Reported-by: NMarcin Gibuła <m.gibula@beyond.pl>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Tested-by: NMarcin Gibuła <m.gibula@beyond.pl>

when hotplug virtio-scsi disks using laio, the aio_nr will
increase in laio_init() by io_setup(), we can see the number by
  # cat /proc/sys/fs/aio-nr
  128
if the aio_nr attach the maxnum, which found from
  # cat /proc/sys/fs/aio-max-nr
  65536
the hotplug process will fail because of aio context leak.

Fix it by io_destroy in laio_cleanup().
Reported-by: Ndaifulai <daifulai@huawei.com>
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

This patch implements .bdrv_io_plug, .bdrv_io_unplug and
.bdrv_flush_io_queue callbacks for linux-aio Block Drivers,
so that submitting I/O as a batch can be supported on linux-aio.

[Unprocessed requests are completed with -EIO instead of a bogus ret
value.
--Stefan]
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Hot unplugging -drive aio=native,file=test.img,format=raw images leaves
the Linux AIO event notifier and struct qemu_laio_state allocated.
Luckily nothing will use the event notifier after the BlockDriverState
has been closed so the handler function is never called.

It's still worth fixing this resource leak.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Drop the assumption that we're using the main AioContext for Linux AIO.
Convert the Linux AIO event notifier to use aio_set_event_notifier().

The .bdrv_detach/attach_aio_context() interfaces also need to be
implemented to move the event notifier handler from the old to the new
AioContext.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

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: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

.io_flush() is no longer called so drop qemu_laio_completion_cb().  It
turns out that count is now unused so drop that too.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Now that AIOPool no longer keeps a freelist, it isn't really a "pool"
anymore.  Rename it to AIOCBInfo and make it const since it no longer
needs to be modified.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since linux-aio already uses an eventfd, converting it to use the
EventNotifier-based API simplifies the code even though it is not
meant to be portable.
Reviewed-by: NAnthony Liguori <anthony@codemonkey.ws>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Start introducing AioContext, which will let us remove globals from
aio.c/async.c, and introduce multiple I/O threads.

The bottom half functions now take an additional AioContext argument.
A bottom half is created with a specific AioContext that remains the
same throughout the lifetime.  qemu_bh_new is just a wrapper that
uses a global context.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>