It is a common requirement for virtual machine to send persistent
reservations, but this currently requires either running QEMU with
CAP_SYS_RAWIO, or using out-of-tree patches that let an unprivileged
QEMU bypass Linux's filter on SG_IO commands.

As an alternative mechanism, the next patches will introduce a
privileged helper to run persistent reservation commands without
expanding QEMU's attack surface unnecessarily.

The helper is invoked through a "pr-manager" QOM object, to which
file-posix.c passes SG_IO requests for PERSISTENT RESERVE OUT and
PERSISTENT RESERVE IN commands.  For example:

  $ qemu-system-x86_64
      -device virtio-scsi \
      -object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
      -drive if=none,id=hd,driver=raw,file.filename=/dev/sdb,file.pr-manager=helper0
      -device scsi-block,drive=hd

or:

  $ qemu-system-x86_64
      -device virtio-scsi \
      -object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
      -blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0
      -device scsi-block,drive=hd

Multiple pr-manager implementations are conceivable and possible, though
only one is implemented right now.  For example, a pr-manager could:

- talk directly to the multipath daemon from a privileged QEMU
  (i.e. QEMU links to libmpathpersist); this makes reservation work
  properly with multipath, but still requires CAP_SYS_RAWIO

- use the Linux IOC_PR_* ioctls (they require CAP_SYS_ADMIN though)

- more interestingly, implement reservations directly in QEMU
  through file system locks or a shared database (e.g. sqlite)

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

Tidy up some of the warn_report() messages after having converted them
to use warn_report().

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <9cb1d23551898c9c9a5f84da6773e99871285120.1505158760.git.alistair.francis@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Convert all the multi-line uses of fprintf(stderr, "warning:"..."\n"...
to use warn_report() instead. This helps standardise on a single
method of printing warnings to the user.

All of the warnings were changed using these commands:
  find ./* -type f -exec sed -i \
    'N; {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N; {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N;N; {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N;N;N {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N;N;N;N {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N;N;N;N;N {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +
  find ./* -type f -exec sed -i \
    'N;N;N;N;N;N;N; {s|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig}' \
    {} +

Indentation fixed up manually afterwards.

Some of the lines were manually edited to reduce the line length to below
80 charecters. Some of the lines with newlines in the middle of the
string were also manually edit to avoid checkpatch errrors.

The #include lines were manually updated to allow the code to compile.

Several of the warning messages can be improved after this patch, to
keep this patch mechanical this has been moved into a later patch.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Yongbok Kim <yongbok.kim@imgtec.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Jason Wang <jasowang@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <5def63849ca8f551630c6f2b45bcb1c482f765a6.1505158760.git.alistair.francis@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Convert all the single line uses of fprintf(stderr, "warning:"..."\n"...
to use warn_report() instead. This helps standardise on a single
method of printing warnings to the user.

All of the warnings were changed using this command:
  find ./* -type f -exec sed -i \
    's|fprintf(.*".*warning[,:] \(.*\)\\n"\(.*\));|warn_report("\1"\2);|Ig' \
    {} +

Some of the lines were manually edited to reduce the line length to below
80 charecters.

The #include lines were manually updated to allow the code to compile.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Yongbok Kim <yongbok.kim@imgtec.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: James Hogan <james.hogan@imgtec.com> [mips]
Message-Id: <ae8f8a7f0a88ded61743dff2adade21f8122a9e7.1505158760.git.alistair.francis@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

In a previous patch (3dc6f869) we
converted uses of error_report("warning:"... to use warn_report()
instead. This was to help standardise on a single method of printing
warnings to the user.

There appears to have been some cases that slipped through in patch sets
applied around the same time, this patch catches the few remaining
cases.

All of the warnings were changed using this command:
  find ./* -type f -exec sed -i \
    's|error_report(".*warning[,:] |warn_report("|Ig' {} +

Indentation fixed up manually afterwards.

Two messages were manually fixed up as well.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <eec8cba0d5434bd828639e5e45f12182490ff47d.1505158760.git.alistair.francis@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Complete the transition by renaming this header, which was
shared by block/iscsi.c and the SCSI emulation code.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

util/scsi.c includes some SCSI code that is shared by block/iscsi.c and
hw/scsi, but the introduction of the persistent reservation helper
will add many more instances of this.  There is also include/block/scsi.h,
which actually is not part of the core block layer.

The persistent reservation manager will also need a home.  A scsi/
directory provides one for both the aforementioned shared code and
the PR manager code.

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

So that it can be reused outside of iscsi.c.

Also update MAINTAINERS to include the new files in SCSI section.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <20170821141008.19383-2-famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Rather than open-coding our own read/write-all functions, we
can make use of the recently-added qio code.  It slightly
changes the error message in one of the iotests.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170905191114.5959-4-eblake@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>

After calling qcow2_inactivate(), all qcow2 caches must be flushed, but this
may not happen, because the last call qcow2_store_persistent_dirty_bitmaps()
can lead to marking l2/refcont cache as dirty.

Let's move qcow2_store_persistent_dirty_bitmaps() before the caсhe flushing
to fix it.

Cc: qemu-stable@nongnu.org
Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/throttle.c uses existing I/O throttle infrastructure inside a
block filter driver. I/O operations are intercepted in the filter's
read/write coroutines, and referred to block/throttle-groups.c

The driver can be used with the syntax
-drive driver=throttle,file.filename=foo.qcow2,throttle-group=bar

which registers the throttle filter node with the ThrottleGroup 'bar'. The
given group must be created beforehand with object-add or -object.

Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

ThrottleGroup is converted to an object. This will allow the future
throttle block filter drive easy creation and configuration of throttle
groups in QMP and cli.

A new QAPI struct, ThrottleLimits, is introduced to provide a shared
struct for all throttle configuration needs in QMP.

ThrottleGroups can be created via CLI as
    -object throttle-group,id=foo,x-iops-total=100,x-..
where x-* are individual limit properties. Since we can't add non-scalar
properties in -object this interface must be used instead. However,
setting these properties must be disabled after initialization because
certain combinations of limits are forbidden and thus configuration
changes should be done in one transaction. The individual properties
will go away when support for non-scalar values in CLI is implemented
and thus are marked as experimental.

ThrottleGroup also has a `limits` property that uses the ThrottleLimits
struct.  It can be used to create ThrottleGroups or set the
configuration in existing groups as follows:

{ "execute": "object-add",
  "arguments": {
    "qom-type": "throttle-group",
    "id": "foo",
    "props" : {
      "limits": {
          "iops-total": 100
      }
    }
  }
}
{ "execute" : "qom-set",
    "arguments" : {
        "path" : "foo",
        "property" : "limits",
        "value" : {
            "iops-total" : 99
        }
    }
}

This also means a group's configuration can be fetched with qom-get.

Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Move the CoMutex and CoQueue inits inside throttle_group_register_tgm()
which is called whenever a ThrottleGroupMember is initialized. There's
no need for them to be separate.

Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

timer_cb() needs to know about the current Aio context of the throttle
request that is woken up. In order to make ThrottleGroupMember backend
agnostic, this information is stored in an aio_context field instead of
accessing it from BlockBackend.

Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

This commit eliminates the 1:1 relationship between BlockBackend and
throttle group state.  Users will be able to create multiple throttle
nodes, each with its own throttle group state, in the future.  The
throttle group state cannot be per-BlockBackend anymore, it must be
per-throttle node. This is done by gathering ThrottleGroup membership
details from BlockBackendPublic into ThrottleGroupMember and refactoring
existing code to use the structure.

Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

The non-blocking connect mechanism is obsolete, and it doesn't
work well in inet connection, because it will call getaddrinfo
first and getaddrinfo will blocks on DNS lookups. Since commit
e65c67e4 & d984464e, the non-blocking connect of migration goes
through QIOChannel in a different manner(using a thread), and
nobody use this old non-blocking connect anymore.

Any newly written code which needs a non-blocking connect should
use the QIOChannel code, so we can drop NonBlockingConnectHandler
as a concept entirely.

Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Mao Zhongyi <maozy.fnst@cn.fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

Omitting the check for whether bdrv_getlength() and bdrv_truncate()
failed meant that it was theoretically possible to return an
incorrect offset to the caller.  More likely, conditions for either
of these functions to fail would also cause one of our other calls
(such as bdrv_pread() or bdrv_pwrite_sync()) to also fail, but
auditing that we are safe is difficult compared to just patching
things to always forward on the error rather than ignoring it.

Use osdep.h macros instead of open-coded rounding while in the
area.

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

The old signature has an ambiguous meaning for a return of 0:
either no allocation was requested or necessary, or an error
occurred (but any errno associated with the error is lost to
the caller, which then has to assume EIO).

Better is to follow the example of qcow2, by changing the
signature to have a separate return value that cleanly
distinguishes between failure and success, along with a
parameter that cleanly holds a 64-bit value.  Then update all
callers.

While auditing that all return paths return a negative errno
(rather than -1), I also simplified places where we can pass
NULL rather than a local Error that just gets thrown away.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

bdrv_co_get_block_status_from_file() and
bdrv_co_get_block_status_from_backing() set *file to bs->file and
bs->backing respectively, so that bdrv_co_get_block_status() can recurse
to them. Future block drivers won't have to duplicate code to implement
this.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Now that bdrv_truncate is passed to bs->file by default, remove the
callback from block/blkdebug.c and set is_filter to true. is_filter also gives
access to other callbacks that are forwarded automatically to bs->file for
filters.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

This function is not used anywhere, so remove it.

Markus Armbruster adds:
The i82078 floppy device model used to call bdrv_media_changed() to
implement its media change bit when backed by a host floppy.  This
went away in 21fcf360 "fdc: simplify media change handling".
Probably broke host floppy media change.  Host floppy pass-through
was dropped in commit f709623b.  bdrv_media_changed() has never been
used for anything else.  Remove it.
(Source is Message-ID: <87y3ruaypm.fsf@dusky.pond.sub.org>)

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Now that all usages have been converted to user lookup helpers.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170822132255.23945-14-marcandre.lureau@redhat.com>
[Rebased, superfluous local variable dropped, missing
check-qom-proplist.c update added]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-17-git-send-email-armbru@redhat.com>

Currently, a FOO_lookup is an array of strings terminated by a NULL
sentinel.

A future patch will generate enums with "holes".  NULL-termination
will cease to work then.

To prepare for that, store the length in the FOO_lookup by wrapping it
in a struct and adding a member for the length.

The sentinel will be dropped next.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170822132255.23945-13-marcandre.lureau@redhat.com>
[Basically redone]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-16-git-send-email-armbru@redhat.com>
[Rebased]

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-14-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

The next commit will put it to use.  May look pointless now, but we're
going to change the FOO_lookup's type, and then it'll help.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-13-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170822132255.23945-12-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, qemu_opt_get() factored out, commit message tweaked]
Cc: Alberto Garcia <berto@igalia.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-9-git-send-email-armbru@redhat.com>

The error message on invalid blkdebug events changes from

    qemu-system-x86_64: LOCATION: Invalid event name "VALUE"

to

    qemu-system-x86_64: LOCATION: invalid parameter value: VALUE

Slight degradation, but the message is sub-par even before the patch.
When complaining about a parameter value, both parameter name and
value should be mentioned, as the value may well not be unique.  Left
for another day.

Also left is the error message's unhelpful location: it points to the
config=FILENAME rather than into that file.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170822132255.23945-11-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, commit message rewritten]
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-8-git-send-email-armbru@redhat.com>

The lookup tables have a sentinel, no need to make callers pass their
size.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-3-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[Rebased, commit message corrected]

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extra



Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extra



Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extra



Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extra



Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

I used the clang-tidy qemu-round check to generate the fix:
https://github.com/elmarco/clang-tools-extra



Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>

Add nbd_co_request, to remove code duplications in
nbd_client_co_{pwrite,pread,...} functions. Also this is
needed for further refactoring.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170804151440.320927-8-vsementsov@virtuozzo.com>
[eblake: make nbd_co_request a wrapper, rather than merging two
existing functions]
Signed-off-by: Eric Blake <eblake@redhat.com>

Rename nbd_recv_coroutines_enter_all to nbd_recv_coroutines_wake_all,
as it most probably just adds all recv coroutines into co_queue_wakeup,
rather than directly enter them.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170804151440.320927-9-vsementsov@virtuozzo.com>
[eblake: tweak commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>

Use int variable for nbd_co_send_request return value (as
nbd_co_send_request returns int).

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170804151440.320927-6-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

The following segfault is encountered if the NBD server closes the UNIX
domain socket immediately after negotiation:

  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  aio_co_schedule (ctx=0x0, co=0xd3c0ff2ef0) at util/async.c:441
  441       QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines,
  (gdb) bt
  #0  0x000000d3c01a50f8 in aio_co_schedule (ctx=0x0, co=0xd3c0ff2ef0) at util/async.c:441
  #1  0x000000d3c012fa90 in nbd_coroutine_end (bs=bs@entry=0xd3c0fec650, request=<optimized out>) at block/nbd-client.c:207
  #2  0x000000d3c012fb58 in nbd_client_co_preadv (bs=0xd3c0fec650, offset=0, bytes=<optimized out>, qiov=0x7ffc10a91b20, flags=0) at block/nbd-client.c:237
  #3  0x000000d3c0128e63 in bdrv_driver_preadv (bs=bs@entry=0xd3c0fec650, offset=offset@entry=0, bytes=bytes@entry=512, qiov=qiov@entry=0x7ffc10a91b20, flags=0) at block/io.c:836
  #4  0x000000d3c012c3e0 in bdrv_aligned_preadv (child=child@entry=0xd3c0ff51d0, req=req@entry=0x7f31885d6e90, offset=offset@entry=0, bytes=bytes@entry=512, align=align@entry=1, qiov=qiov@entry=0x7ffc10a91b20, f
+lags=0) at block/io.c:1086
  #5  0x000000d3c012c6b8 in bdrv_co_preadv (child=0xd3c0ff51d0, offset=offset@entry=0, bytes=bytes@entry=512, qiov=qiov@entry=0x7ffc10a91b20, flags=flags@entry=0) at block/io.c:1182
  #6  0x000000d3c011cc17 in blk_co_preadv (blk=0xd3c0ff4f80, offset=0, bytes=512, qiov=0x7ffc10a91b20, flags=0) at block/block-backend.c:1032
  #7  0x000000d3c011ccec in blk_read_entry (opaque=0x7ffc10a91b40) at block/block-backend.c:1079
  #8  0x000000d3c01bbb96 in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:79
  #9  0x00007f3196cb8600 in __start_context () at /lib64/libc.so.6

The problem is that nbd_client_init() uses
nbd_client_attach_aio_context() -> aio_co_schedule(new_context,
client->read_reply_co).  Execution of read_reply_co is deferred to a BH
which doesn't run until later.

In the mean time blk_co_preadv() can be called and nbd_coroutine_end()
calls aio_wake() on read_reply_co.  At this point in time
read_reply_co's ctx isn't set because it has never been entered yet.

This patch simplifies the nbd_co_send_request() ->
nbd_co_receive_reply() -> nbd_coroutine_end() lifecycle to just
nbd_co_send_request() -> nbd_co_receive_reply().  The request is "ended"
if an error occurs at any point.  Callers no longer have to invoke
nbd_coroutine_end().

This cleanup also eliminates the segfault because we don't call
aio_co_schedule() to wake up s->read_reply_co if sending the request
failed.  It is only necessary to wake up s->read_reply_co if a reply was
received.

Note this only happens with UNIX domain sockets on Linux.  It doesn't
seem possible to reproduce this with TCP sockets.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170829122745.14309-2-stefanha@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

Most qcow2 files are uncompressed so it is wasteful to allocate (32 + 1)
* cluster_size + 512 bytes upfront.  Allocate s->cluster_cache and
s->cluster_data when the first read operation is performance on a
compressed cluster.

The buffers are freed in .bdrv_close().  .bdrv_open() no longer has any
code paths that can allocate these buffers, so remove the free functions
in the error code path.

This patch can result in significant memory savings when many qcow2
disks are attached or backing file chains are long:

Before 12.81% (1,023,193,088B)
After   5.36% (393,893,888B)

Reported-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170821135530.32344-1-stefanha@redhat.com
Cc: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

There's a few cases which we're passing an Error pointer to a function
only to discard it immediately afterwards without checking it. In
these cases we can simply remove the variable and pass NULL instead.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20170829120836.16091-1-berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

The following scenario leads to an assertion failure in
qio_channel_yield():

1. Request coroutine calls qio_channel_yield() successfully when sending
   would block on the socket.  It is now yielded.
2. nbd_read_reply_entry() calls nbd_recv_coroutines_enter_all() because
   nbd_receive_reply() failed.
3. Request coroutine is entered and returns from qio_channel_yield().
   Note that the socket fd handler has not fired yet so
   ioc->write_coroutine is still set.
4. Request coroutine attempts to send the request body with nbd_rwv()
   but the socket would still block.  qio_channel_yield() is called
   again and assert(!ioc->write_coroutine) is hit.

The problem is that nbd_read_reply_entry() does not distinguish between
request coroutines that are waiting to receive a reply and those that
are not.

This patch adds a per-request bool receiving flag so
nbd_read_reply_entry() can avoid spurious aio_wake() calls.

Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170822125113.5025-1-stefanha@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Tested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>