block/export: Remove magic from block-export-add

nbd-server-add tries to be convenient and adds two questionable
features that we don't want to share in block-export-add, even for NBD
exports:

1. W

block/export: Remove magic from block-export-add

nbd-server-add tries to be convenient and adds two questionable
features that we don't want to share in block-export-add, even for NBD
exports:

1. When requesting a writable export of a read-only device, the export
is silently downgraded to read-only. This should be an error in the
context of block-export-add.

2. When using a BlockBackend name, unplugging the device from the guest
will automatically stop the NBD server, too. This may sometimes be
what you want, but it could also be very surprising. Let's keep
things explicit with block-export-add. If the user wants to stop the
export, they should tell us so.

Move these things into the nbd-server-add QMP command handler so that
they apply only there.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-8-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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qemu-nbd: Use raw block driver for --offset

Instead of implementing qemu-nbd --offset in the NBD code, just put a
raw block node with the requested offset on top of the user image and
rely on that d

qemu-nbd: Use raw block driver for --offset

Instead of implementing qemu-nbd --offset in the NBD code, just put a
raw block node with the requested offset on top of the user image and
rely on that doing the job.

This does not only simplify the nbd_export_new() interface and bring it
closer to the set of options that the nbd-server-add QMP command offers,
but in fact it also eliminates a potential source for bugs in the NBD
code which previously had to add the offset manually in all relevant
places.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-7-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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block/export: Add BlockExport infrastructure and block-export-add

We want to have a common set of commands for all types of block exports.
Currently, this is only NBD, but we're going to add more ty

block/export: Add BlockExport infrastructure and block-export-add

We want to have a common set of commands for all types of block exports.
Currently, this is only NBD, but we're going to add more types.

This patch adds the basic BlockExport and BlockExportDriver structs and
a QMP command block-export-add that creates a new export based on the
given BlockExportOptions.

qmp_nbd_server_add() becomes a wrapper around qmp_block_export_add().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20200924152717.287415-5-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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nbd: Remove unused nbd_export_get_blockdev()

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924

nbd: Remove unused nbd_export_get_blockdev()

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200924152717.287415-2-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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nbd: Use CAF when looking for dirty bitmap

When looking for a dirty bitmap to share, we should handle filters by
just including them in the search (so they do not break backing chains).

Signed-off-

nbd: Use CAF when looking for dirty bitmap

When looking for a dirty bitmap to share, we should handle filters by
just including them in the search (so they do not break backing chains).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>

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meson: convert block

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

trace: switch position of headers to what Meson requires

Meson doesn't enjoy the same flexibility we have with Make in choosing
the include path. In particular the tracing headers are using
$(build

trace: switch position of headers to what Meson requires

Meson doesn't enjoy the same flexibility we have with Make in choosing
the include path. In particular the tracing headers are using
$(build_root)/$(<D).

In order to keep the include directives unchanged,
the simplest solution is to generate headers with patterns like
"trace/trace-audio.h" and place forwarding headers in the source tree
such that for example "audio/trace.h" includes "trace/trace-audio.h".

This patch is too ugly to be applied to the Makefiles now. It's only
a way to separate the changes to the tracing header files from the
Meson rewrite of the tracing logic.

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

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nbd: Fix large trim/zero requests

Although qemu as NBD client limits requests to <2G, the NBD protocol
allows clients to send requests almost all the way up to 4G. But
because our block layer is no

nbd: Fix large trim/zero requests

Although qemu as NBD client limits requests to <2G, the NBD protocol
allows clients to send requests almost all the way up to 4G. But
because our block layer is not yet 64-bit clean, we accidentally wrap
such requests into a negative size, and fail with EIO instead of
performing the intended operation.

The bug is visible in modern systems with something as simple as:

$ qemu-img create -f qcow2 /tmp/image.img 5G
$ sudo qemu-nbd --connect=/dev/nbd0 /tmp/image.img
$ sudo blkdiscard /dev/nbd0

or with user-space only:

$ truncate --size=3G file
$ qemu-nbd -f raw file
$ nbdsh -u nbd://localhost:10809 -c 'h.trim(3*1024*1024*1024,0)'

Although both blk_co_pdiscard and blk_pwrite_zeroes currently return 0
on success, this is also a good time to fix our code to a more robust
paradigm that treats all non-negative values as success.

Alas, our iotests do not currently make it easy to add external
dependencies on blkdiscard or nbdsh, so we have to rely on manual
testing for now.

This patch can be reverted when we later improve the overall block
layer to be 64-bit clean, but for now, a minimal fix was deemed less
risky prior to release.

CC: qemu-stable@nongnu.org
Fixes: 1f4d6d18ed
Fixes: 1c6c4bb7f0
Fixes: https://github.com/systemd/systemd/issues/16242
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200722212231.535072-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[eblake: rework success tests to use >=0]

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nbd: make nbd_export_close_all() synchronous

Consider nbd_export_close_all(). The call-stack looks like this:
nbd_export_close_all() -> nbd_export_close -> call client_close() for
each client.

cli

nbd: make nbd_export_close_all() synchronous

Consider nbd_export_close_all(). The call-stack looks like this:
nbd_export_close_all() -> nbd_export_close -> call client_close() for
each client.

client_close() doesn't guarantee that client is closed: nbd_trip()
keeps reference to it. So, nbd_export_close_all() just reduce
reference counter on export and removes it from the list, but doesn't
guarantee that nbd_trip() finished neither export actually removed.

Let's wait for all exports actually removed.

Without this fix, the following crash is possible:

- export bitmap through internal Qemu NBD server
- connect a client
- shutdown Qemu

On shutdown nbd_export_close_all is called, but it actually don't wait
for nbd_trip() to finish and to release its references. So, export is
not release, and exported bitmap remains busy, and on try to remove the
bitmap (which is part of bdrv_close()) the assertion fails:

bdrv_release_dirty_bitmap_locked: Assertion `!bdrv_dirty_bitmap_busy(bitmap)' failed

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200714162234.13113-2-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

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nbd: Use ERRP_GUARD()

If we want to check error after errp-function call, we need to
introduce local_err and then propagate it to errp. Instead, use
the ERRP_GUARD() macro, benefits are:
1. No need

nbd: Use ERRP_GUARD()

If we want to check error after errp-function call, we need to
introduce local_err and then propagate it to errp. Instead, use
the ERRP_GUARD() macro, benefits are:
1. No need of explicit error_propagate call
2. No need of explicit local_err variable: use errp directly
3. ERRP_GUARD() leaves errp as is if it's not NULL or
&error_fatal, this means that we don't break error_abort
(we'll abort on error_set, not on error_propagate)

If we want to add some info to errp (by error_prepend() or
error_append_hint()), we must use the ERRP_GUARD() macro.
Otherwise, this info will not be added when errp == &error_fatal
(the program will exit prior to the error_append_hint() or
error_prepend() call). Fix several such cases, e.g. in nbd_read().

This commit is generated by command

sed -n '/^Network Block Device (NBD)$/,/^$/{s/^F: //p}' \
MAINTAINERS | \
xargs git ls-files | grep '\.[hc]$' | \
xargs spatch \
--sp-file scripts/coccinelle/errp-guard.cocci \
--macro-file scripts/cocci-macro-file.h \
--in-place --no-show-diff --max-width 80

Reported-by: Kevin Wolf <kwolf@redhat.com>
Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20200707165037.1026246-8-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[ERRP_AUTO_PROPAGATE() renamed to ERRP_GUARD(), and
auto-propagated-errp.cocci to errp-guard.cocci. Commit message
tweaked again.]

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