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  1. Dec 19, 2020
    • Markus Armbruster's avatar
      block: Use GString instead of QString to build filenames · 18cf67c5
      Markus Armbruster authored 
      
QString supports modifying its string, but it's quite limited: you can
only append.  Just one caller remains:
bdrv_parse_filename_strip_prefix() uses it just for building an
initial string.

Change it to do build the initial string with GString.  This is
another step towards making QString immutable.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-20-armbru@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
      18cf67c5
    • Markus Armbruster's avatar
      block: Avoid qobject_get_try_str() · 410f44f5
      Markus Armbruster authored 
      
I'm about to remove qobject_get_try_str().  Use qstring_get_str()
instead.  Safe because the argument is known to be a QString here.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-11-armbru@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
      410f44f5
    • Markus Armbruster's avatar
      qobject: Change qobject_to_json()'s value to GString · eab3a467
      Markus Armbruster authored 
      
qobject_to_json() and qobject_to_json_pretty() build a GString, then
covert it to QString.  Just one of the callers actually needs a
QString: qemu_rbd_parse_filename().  A few others need a string they
can modify: qmp_send_response(), qga's send_response(), to_json_str(),
and qmp_fd_vsend_fds().  The remainder just need a string.

Change qobject_to_json() and qobject_to_json_pretty() to return the
GString.

qemu_rbd_parse_filename() now has to convert to QString.  All others
save a QString temporary.  to_json_str() actually becomes a bit
simpler, because GString provides more convenient modification
functions.

Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-6-armbru@redhat.com>
      eab3a467
  3. Dec 18, 2020
  5. Dec 11, 2020
    • Vladimir Sementsov-Ogievskiy's avatar
      block: introduce BDRV_MAX_LENGTH · 8b117001
      Vladimir Sementsov-Ogievskiy authored 
      
We are going to modify block layer to work with 64bit requests. And
first step is moving to int64_t type for both offset and bytes
arguments in all block request related functions.

It's mostly safe (when widening signed or unsigned int to int64_t), but
switching from uint64_t is questionable.

So, let's first establish the set of requests we want to work with.
First signed int64_t should be enough, as off_t is signed anyway. Then,
obviously offset + bytes should not overflow.

And most interesting: (offset + bytes) being aligned up should not
overflow as well. Aligned to what alignment? First thing that comes in
mind is bs->bl.request_alignment, as we align up request to this
alignment. But there is another thing: look at
bdrv_mark_request_serialising(). It aligns request up to some given
alignment. And this parameter may be bdrv_get_cluster_size(), which is
often a lot greater than bs->bl.request_alignment.
Note also, that bdrv_mark_request_serialising() uses signed int64_t for
calculations. So, actually, we already depend on some restrictions.

Happily, bdrv_get_cluster_size() returns int and
bs->bl.request_alignment has 32bit unsigned type, but defined to be a
power of 2 less than INT_MAX. So, we may establish, that INT_MAX is
absolute maximum for any kind of alignment that may occur with the
request.

Note, that bdrv_get_cluster_size() is not documented to return power
of 2, still bdrv_mark_request_serialising() behaves like it is.
Also, backup uses bdi.cluster_size and is not prepared to it not being
power of 2.
So, let's establish that Qemu supports only power-of-2 clusters and
alignments.

So, alignment can't be greater than 2^30.

Finally to be safe with calculations, to not calculate different
maximums for different nodes (depending on cluster size and
request_alignment), let's simply set QEMU_ALIGN_DOWN(INT64_MAX, 2^30)
as absolute maximum bytes length for Qemu. Actually, it's not much less
than INT64_MAX.

OK, then, let's apply it to block/io.

Let's consider all block/io entry points of offset/bytes:

4 bytes/offset interface functions: bdrv_co_preadv_part(),
bdrv_co_pwritev_part(), bdrv_co_copy_range_internal() and
bdrv_co_pdiscard() and we check them all with bdrv_check_request().

We also have one entry point with only offset: bdrv_co_truncate().
Check the offset.

And one public structure: BdrvTrackedRequest. Happily, it has only
three external users:

 file-posix.c: adopted by this patch
 write-threshold.c: only read fields
 test-write-threshold.c: sets obviously small constant values

Better is to make the structure private and add corresponding
interfaces.. Still it's not obvious what kind of interface is needed
for file-posix.c. Let's keep it public but add corresponding
assertions.

After this patch we'll convert functions in block/io.c to int64_t bytes
and offset parameters. We can assume that offset/bytes pair always
satisfy new restrictions, and make
corresponding assertions where needed. If we reach some offset/bytes
point in block/io.c missing bdrv_check_request() it is considered a
bug. As well, if block/io.c modifies a offset/bytes request, expanding
it more then aligning up to request_alignment, it's a bug too.

For all io requests except for discard we keep for now old restriction
of 32bit request length.

iotest 206 output error message changed, as now test disk size is
larger than new limit. Add one more test case with new maximum disk
size to cover too-big-L1 case.

Signed-off-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201203222713.13507-5-vsementsov@virtuozzo.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
      8b117001
    • Hanna Reitz's avatar
      fuse: Allow exporting BDSs via FUSE · 0c9b70d5
      Hanna Reitz authored 
      
block-export-add type=fuse allows mounting block graph nodes via FUSE on
some existing regular file.  That file should then appears like a raw
disk image, and accesses to it result in accesses to the exported BDS.

Right now, we only implement the necessary block export functions to set
it up and shut it down.  We do not implement any access functions, so
accessing the mount point only results in errors.  This will be
addressed by a followup patch.

We keep a hash table of exported mount points, because we want to be
able to detect when users try to use a mount point twice.  This is
because we invoke stat() to check whether the given mount point is a
regular file, but if that file is served by ourselves (because it is
already used as a mount point), then this stat() would have to be served
by ourselves, too, which is impossible to do while we (as the caller)
are waiting for it to settle.  Therefore, keep track of mount point
paths to at least catch the most obvious instances of that problem.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Message-Id: <20201027190600.192171-3-mreitz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
      0c9b70d5
  7. Nov 09, 2020
  9. Oct 30, 2020
    • Eric Blake's avatar
      qapi: Add QAPI_LIST_PREPEND() macro · 9812e712
      Eric Blake authored 
      
block.c has a useful macro QAPI_LIST_ADD() for inserting at the front
of any QAPI-generated list; move it from block.c to qapi/util.h so
more places can use it, including one earlier place in block.c, and
rename it to something more obvious (since we also have a lot of
places that append, rather than prepend, to a list).

There are many more places in the codebase that can benefit from using
the macro, but converting them will be left to later patches.

In theory, all QAPI list types are child classes of GenericList; but
in practice, that relationship is not explicitly spelled out in the C
type declarations (rather, it is something that happens implicitly due
to C compatible layouts), and the macro does not actually depend on
the GenericList type.  We considered moving GenericList from visitor.h
into util.h to group related code; however, such a move would be
awkward if we do not also move GenericAlternate.  Unfortunately,
moving GenericAlternate would introduce its own problems of
declaration circularity (qapi-builtin-types.h needs a complete
definition of QEnumLookup from util.h, but GenericAlternate needs a
complete definition of QType from qapi-builtin-types.h).

Suggested-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
Message-Id: <20201027050556.269064-3-eblake@redhat.com>
[eblake: s/ADD/PREPEND/ per suggestion by Markus]
      9812e712
    • Eric Blake's avatar
      block: Simplify QAPI_LIST_ADD · 159f8442
      Eric Blake authored 
      
There is no need to rely on the verbosity of the gcc/clang compiler
extension of g_new(typeof(X), 1) when we can instead use the standard
g_malloc(sizeof(X)).  In general, we like g_new over g_malloc for
returning type X rather than void* to let the compiler catch more
potential typing mistakes, but in this particular macro, our other use
of typeof on the same line already ensures we are getting correct
results.

Suggested-by: default avatarMarkus Armbruster <armbru@redhat.com>
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Message-Id: <20201027050556.269064-2-eblake@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: default avatarMarkus Armbruster <armbru@redhat.com>
      159f8442
  11. Oct 27, 2020
    • Greg Kurz's avatar
      block: End quiescent sections when a BDS is deleted · 1a6d3bd2
      Greg Kurz authored 
      If a BDS gets deleted during blk_drain_all(), it might miss a
call to bdrv_do_drained_end(). This means missing a call to
aio_enable_external() and the AIO context remains disabled for
ever. This can cause a device to become irresponsive and to
disrupt the guest execution, ie. hang, loop forever or worse.

This scenario is quite easy to encounter with virtio-scsi
on POWER when punching multiple blockdev-create QMP commands
while the guest is booting and it is still running the SLOF
firmware. This happens because SLOF disables/re-enables PCI
devices multiple times via IO/MEM/MASTER bits of PCI_COMMAND
register after the initial probe/feature negotiation, as it
tends to work with a single device at a time at various stages
like probing and running block/network bootloaders without
doing a full reset in-between. This naturally generates many
dataplane stops and starts, and thus many drain sections that
can race with blockdev_create_run(). In the end, SLOF bails
out.

It is somehow reproducible on x86 but it requires to generate
articial dataplane start/stop activity with stop/cont QMP
commands. In this case, seabios ends up looping for ever,
waiting for the virtio-scsi device to send a response to
a command it never received.

Add a helper that pairs all previously called bdrv_do_drained_begin()
with a bdrv_do_drained_end() and call it from bdrv_close().
While at it, update the "/bdrv-drain/graph-change/drain_all"
test in test-bdrv-drain so that it can catch the issue.

BugId: https://bugzilla.redhat.com/show_bug.cgi?id=1874441


Signed-off-by: default avatarGreg Kurz <groug@kaod.org>
Message-Id: <160346526998.272601.9045392804399803158.stgit@bahia.lan>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
      1a6d3bd2
  13. Oct 09, 2020
  15. Oct 05, 2020
  17. Oct 02, 2020
  19. Sep 23, 2020
    • Stefan Hajnoczi's avatar
      qemu/atomic.h: rename atomic_ to qatomic_ · d73415a3
      Stefan Hajnoczi authored 
      
clang's C11 atomic_fetch_*() functions only take a C11 atomic type
pointer argument. QEMU uses direct types (int, etc) and this causes a
compiler error when a QEMU code calls these functions in a source file
that also included <stdatomic.h> via a system header file:

  $ CC=clang CXX=clang++ ./configure ... && make
  ../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid)

Avoid using atomic_*() names in QEMU's atomic.h since that namespace is
used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h
and <stdatomic.h> can co-exist. I checked /usr/include on my machine and
searched GitHub for existing "qatomic_" users but there seem to be none.

This patch was generated using:

  $ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \
    sort -u >/tmp/changed_identifiers
  $ for identifier in $(</tmp/changed_identifiers); do
        sed -i "s%\<$identifier\>%q$identifier%g" \
            $(git grep -I -l "\<$identifier\>")
    done

I manually fixed line-wrap issues and misaligned rST tables.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
      d73415a3
  21. Sep 17, 2020
  23. Sep 07, 2020
    • Hanna Reitz's avatar
      block: Leave BDS.backing_{file,format} constant · 0b877d09
      Hanna Reitz authored 
      
Parts of the block layer treat BDS.backing_file as if it were whatever
the image header says (i.e., if it is a relative path, it is relative to
the overlay), other parts treat it like a cache for
bs->backing->bs->filename (relative paths are relative to the CWD).
Considering bs->backing->bs->filename exists, let us make it mean the
former.

Among other things, this now allows the user to specify a base when
using qemu-img to commit an image file in a directory that is not the
CWD (assuming, everything uses relative filenames).

Before this patch:

$ ./qemu-img create -f qcow2 foo/bot.qcow2 1M
$ ./qemu-img create -f qcow2 -b bot.qcow2 foo/mid.qcow2
$ ./qemu-img create -f qcow2 -b mid.qcow2 foo/top.qcow2
$ ./qemu-img commit -b mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find '[...]/foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'

After this patch:

$ ./qemu-img commit -b mid.qcow2 foo/top.qcow2
Image committed.
$ ./qemu-img commit -b foo/mid.qcow2 foo/top.qcow2
qemu-img: Did not find 'foo/mid.qcow2' in the backing chain of 'foo/top.qcow2'
$ ./qemu-img commit -b $PWD/foo/mid.qcow2 foo/top.qcow2
Image committed.

With this change, bdrv_find_backing_image() must look at whether the
user has overridden a BDS's backing file.  If so, it can no longer use
bs->backing_file, but must instead compare the given filename against
the backing node's filename directly.

Note that this changes the QAPI output for a node's backing_file.  We
had very inconsistent output there (sometimes what the image header
said, sometimes the actual filename of the backing image).  This
inconsistent output was effectively useless, so we have to decide one
way or the other.  Considering that bs->backing_file usually at runtime
contained the path to the image relative to qemu's CWD (or absolute),
this patch changes QAPI's backing_file to always report the
bs->backing->bs->filename from now on.  If you want to receive the image
header information, you have to refer to full-backing-filename.

This necessitates a change to iotest 228.  The interesting information
it really wanted is the image header, and it can get that now, but it
has to use full-backing-filename instead of backing_file.  Because of
this patch's changes to bs->backing_file's behavior, we also need some
reference output changes.

Along with the changes to bs->backing_file, stop updating
BDS.backing_format in bdrv_backing_attach() as well.  This way,
ImageInfo's backing-filename and backing-filename-format fields will
represent what the image header says and nothing else.

iotest 245 changes in behavior: With the backing node no longer
overriding the parent node's backing_file string, you can now omit the
@backing option when reopening a node with neither a default nor a
current backing file even if it used to have a backing node at some
point.

273 also changes: The base image is opened without a format layer, so
ImageInfo.backing-filename-format used to report "file" for the base
image's overlay after blockdev-snapshot.  However, the image header
never says "file" anywhere, so it now reports $IMGFMT.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
      0b877d09
    • Hanna Reitz's avatar
      block: Improve get_allocated_file_size's default · 081e4650
      Hanna Reitz authored 
      
There are two practical problems with bdrv_get_allocated_file_size()'s
default right now:
(1) For drivers with children, we should generally sum all their sizes
    instead of just passing the request through to bs->file.  The latter
    is good for filters, but not so much for format drivers.

(2) Filters need not have bs->file, so we should actually go to the
    filtered child instead of hard-coding bs->file.

Fix this by splitting the default implementation into three branches:
(1) For filter drivers: Return the size of the filtered child
(2) For protocol drivers: Return -ENOTSUP, because the default
    implementation cannot make a guess
(3) For other drivers: Sum all data-bearing children's sizes

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
      081e4650
    • Hanna Reitz's avatar
      block: Use CAFs for debug breakpoints · f706a92f
      Hanna Reitz authored 
      
When looking for a blkdebug node (which implements debug breakpoints),
use bdrv_primary_bs() to iterate through the graph, because that is
where a blkdebug node would be.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      f706a92f
    • Hanna Reitz's avatar
      block: Use CAFs in bdrv_refresh_filename() · 52f72d6f
      Hanna Reitz authored 
      
bdrv_refresh_filename() and the kind of related bdrv_dirname() should
look to the primary child when they wish to copy the underlying file's
filename.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      52f72d6f
    • Hanna Reitz's avatar
      block: Re-evaluate backing file handling in reopen · 1d42f48c
      Hanna Reitz authored 
      
Reopening a node's backing child needs a bit of special handling because
the "backing" child has different defaults than all other children
(among other things).  Adding filter support here is a bit more
difficult than just using the child access functions.  In fact, we often
have to directly use bs->backing because these functions are about the
"backing" child (which may or may not be the COW backing file).

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
      1d42f48c
    • Hanna Reitz's avatar
      block: Use CAFs when working with backing chains · dcf3f9b2
      Hanna Reitz authored 
      
Use child access functions when iterating through backing chains so
filters do not break the chain.

In addition, bdrv_find_overlay() will now always return the actual
overlay; that is, it will never return a filter node but only one with a
COW backing file (there may be filter nodes between that node and @bs).

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
      dcf3f9b2
    • Hanna Reitz's avatar
      block: Use bdrv_filter_(bs|child) where obvious · 93393e69
      Hanna Reitz authored 
      
Places that use patterns like

    if (bs->drv->is_filter && bs->file) {
        ... something about bs->file->bs ...
    }

should be

    BlockDriverState *filtered = bdrv_filter_bs(bs);
    if (filtered) {
        ... something about @filtered ...
    }

instead.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      93393e69
    • Hanna Reitz's avatar
      block: Add bdrv_supports_compressed_writes() · ae23f786
      Hanna Reitz authored 
      
Filters cannot compress data themselves but they have to implement
.bdrv_co_pwritev_compressed() still (or they cannot forward compressed
writes).  Therefore, checking whether
bs->drv->bdrv_co_pwritev_compressed is non-NULL is not sufficient to
know whether the node can actually handle compressed writes.  This
function looks down the filter chain to see whether there is a
non-filter that can actually convert the compressed writes into
compressed data (and thus normal writes).

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      ae23f786
    • Hanna Reitz's avatar
      block: Drop bdrv_is_encrypted() · 8b8277cd
      Hanna Reitz authored 
      
The original purpose of bdrv_is_encrypted() was to inquire whether a BDS
can be used without the user entering a password or not.  It has not
been used for that purpose for quite some time.

Actually, it is not even fit for that purpose, because to answer that
question, it would have recursively query all of the given node's
children.

So now we have to decide in which direction we want to fix
bdrv_is_encrypted(): Recursively query all children, or drop it and just
use bs->encrypted to get the current node's status?

Nowadays, its only purpose is to report through bdrv_query_image_info()
whether the given image is encrypted or not.  For this purpose, it is
probably more interesting to see whether a given node itself is
encrypted or not (otherwise, a management application cannot discern for
certain which nodes are really encrypted and which just have encrypted
children).

Suggested-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      8b8277cd
    • Hanna Reitz's avatar
      block: Include filters when freezing backing chain · 7b99a266
      Hanna Reitz authored 
      
In order to make filters work in backing chains, the associated
functions must be able to deal with them and freeze both COW and filter
child links.

While at it, add some comments that note which functions require their
caller to ensure that a given child link is not frozen, and how the
callers do so.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      7b99a266
    • Hanna Reitz's avatar
      block: bdrv_set_backing_hd() is about bs->backing · 9ee413cb
      Hanna Reitz authored 
      
bdrv_set_backing_hd() is a function that explicitly cares about the
bs->backing child.  Highlight that in its description and use
child_bs(bs->backing) instead of backing_bs(bs) to make it more obvious.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      9ee413cb
    • Hanna Reitz's avatar
      block: bdrv_cow_child() for bdrv_has_zero_init() · 34778172
      Hanna Reitz authored 
      
bdrv_has_zero_init() should use bdrv_cow_child() if it wants to check
whether the given BDS has a COW backing file.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarAndrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
      34778172
    • Hanna Reitz's avatar
      block: Add chain helper functions · d38d7eb8
      Hanna Reitz authored 
      
Add some helper functions for skipping filters in a chain of block
nodes.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
      d38d7eb8
    • Hanna Reitz's avatar
      block: Add child access functions · 9a6fc887
      Hanna Reitz authored 
      
There are BDS children that the general block layer code can access,
namely bs->file and bs->backing.  Since the introduction of filters and
external data files, their meaning is not quite clear.  bs->backing can
be a COW source, or it can be a filtered child; bs->file can be a
filtered child, it can be data and metadata storage, or it can be just
metadata storage.

This overloading really is not helpful.  This patch adds functions that
retrieve the correct child for each exact purpose.  Later patches in
this series will make use of them.  Doing so will allow us to handle
filter nodes in a meaningful way.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
      9a6fc887
    • Connor Kuehl's avatar
      block: Raise an error when backing file parameter is an empty string · 975a7bd2
      Connor Kuehl authored 
      
Providing an empty string for the backing file parameter like so:

	qemu-img create -f qcow2 -b '' /tmp/foo

allows the flow of control to reach and subsequently fail an assert
statement because passing an empty string to

	bdrv_get_full_backing_filename_from_filename()

simply results in NULL being returned without an error being raised.

To fix this, let's check for an empty string when getting the value from
the opts list.

Reported-by: default avatarAttila Fazekas <afazekas@redhat.com>
Fixes: https://bugzilla.redhat.com/1809553


Signed-off-by: default avatarConnor Kuehl <ckuehl@redhat.com>
Message-Id: <20200813134722.802180-1-ckuehl@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
      975a7bd2