Now that we store only relative names in virStorageSource's member
relPath the backingRelative member is obsolete. Remove it and adapt the
code to the removal.

Due to various refactors and compatibility with the virstoragetest the
relPath field of the virStorageSource structure was always filled either
with the relative name or the full path in case of absolutely backed
storage. Return its original purpose to store only the relative name of
the disk if it is backed relatively and tweak the tests.

This patch introduces a function that will allow us to resolve a
relative difference between two elements of a disk backing chain. This
function will be used to allow relative block commit and block pull
where we need to specify the new relative name of the image to qemu.

This patch also adds unit tests for the function to verify that it works
correctly.

Introduce a common function that will take a callback to resolve links
that will be used to canonicalize paths on various storage systems and
add extensive tests.

The image labels are stored in the virStorageSource struct. Convert the
virDomainDiskDefGetSecurityLabelDef helper not to use the full disk def
and move it appropriately.

Add parsers for relative and absolute backing names for local and remote
storage files.

This parser parses relative paths as relative to their parents and
absolute paths according to the protocol or local access.

For remote storage volumes, all URI based backing file names are
supported and for the qemu colon syntax the NBD protocol is supported.

Use virStorageFileReadHeader() to read headers of storage files possibly
on remote storage to retrieve the image metadata.

The backend information is now parsed by
virStorageFileGetMetadataInternal which is now exported from the util
source and virStorageFileGetMetadataFromFDInternal now doesn't need to
be exported.

My future work will modify the metadata crawler function to use the
storage driver file APIs to access the files instead of accessing them
directly so that we will be able to request the metadata for remote
files too. To avoid linking the storage driver to every helper file
using the utils code, the backing chain traversal function needs to be
moved to the storage driver source.

Additionally the virt-aa-helper and virstoragetest programs need to be
linked with the storage driver as a result of this change.

Add argument to return backing file format of a file probed by
virStorageFileGetMetadataFromFD so that it can be used in place of
virStorageFileGetMetadataFromBuf.

Currently the protocol type with index 0 was NBD which made it hard to
distinguish whether the protocol type was actually assigned. Add a new
protocol type with index 0 to distinguish it explicitly.

The gluster volume name was previously stored as part of the source path
string. This is unfortunate when we want to do operations on the path as
the volume is used separately.

Parse and store the volume name separately for gluster storage volumes
and use the newly stored variable appropriately.

This partially reverts commits b279e52f and ea18f8b2.

It turns out our code base is full of:

if ((struct.member = virBlahFromString(str)) < 0)
    goto error;

Meanwhile, the C standard says it is up to the compiler whether
an enum is signed or unsigned when all of its declared values
happen to be positive.  In my testing (Fedora 20, gcc 4.8.2),
the compiler picked signed, and nothing changed.  But others
testing with gcc 4.7 got compiler warnings, because it picked
the enum to be unsigned, but no unsigned value is less than 0.
Even worse:

if ((struct.member = virBlahFromString(str)) <= 0)
    goto error;

is silently compiled without warning, but incorrectly treats -1
from a bad parse as a large positive number with no warning; and
without the compiler's help to find these instances, it is a
nightmare to maintain correctly.  We could force signed enums
with a dummy negative declaration in each enum, or cast the
result of virBlahFromString back to int after assigning to an
enum value, or use a temporary int for collecting results from
virBlahFromString, but those actions are all uglier than what we
were trying to cure by directly using enum types for struct
values in the first place.  It's better off to just live with int
members, and use 'switch ((virFoo) struct.member)' where we want
the compiler to help, than to track down all the conversions from
string to enum and ensure they don't suffer from type problems.

* src/util/virstorageencryption.h: Revert back to int declarations
with comment about enum usage.
* src/util/virstoragefile.h: Likewise.
* src/conf/domain_conf.c: Restore back to casts in switches.
* src/qemu/qemu_driver.c: Likewise.
* src/qemu/qemu_command.c: Add cast rather than revert.
Signed-off-by: NEric Blake <eblake@redhat.com>

Add VIR_STORAGE_FILE_PLOOP format. This format is used
to store disk images for virtual machines in PCS and containers
in PCS, OpenVZ and also in Parallels Desktop for Mac.

This format is described on OpenVZ site -
https://openvz.org/Ploop (together with ploop devices). It
consists of XML descriptor and one or more image files: base
image and deltas. Format of the image files described here:
https://openvz.org/Ploop/format.

This patch only adds VIR_STORAGE_FILE_PLOOP constant, consequent
patches will use it in parallels driver.
Signed-off-by: NDmitry Guryanov <dguryanov@parallels.com>

For internal structs, we might as well be type-safe and let the
compiler help us with less typing required on our part (getting
rid of casts is always nice).  In trying to use enums directly,
I noticed two problems in virstoragefile.h that can't be fixed
without more invasive refactoring: virStorageSource.format is
used as more of a union of multiple enums in storage volume
code (so it has to remain an int), and virStorageSourcePoolDef
refers to pooltype whose enum is declared in src/conf, but where
src/util can't pull in headers from src/conf.

* src/util/virstoragefile.h (virStorageNetHostDef)
(virStorageSourcePoolDef, virStorageSource): Use enums instead of
int for fields of internal types.
* src/qemu/qemu_command.c (qemuParseCommandLine): Cover all values.
* src/conf/domain_conf.c (virDomainDiskSourceParse)
(virDomainDiskSourceFormat): Simplify clients.
* src/qemu/qemu_driver.c
(qemuDomainSnapshotCreateSingleDiskActive)
(qemuDomainSnapshotPrepareDiskExternalBackingInactive)
(qemuDomainSnapshotPrepareDiskExternalOverlayActive)
(qemuDomainSnapshotPrepareDiskInternal): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

In "src/conf/" there are many enumeration (enum) declarations.
Similar to the recent cleanup to "src/util" directory, it's
better to use a typedef for variable types, function types and
other usages. Other enumeration and folders will be changed to
typedef's in the future. Most of the files changed in this
commit are related to storage (storage_conf) enums.
Signed-off-by: NJulio Faracco <jcfaracco@gmail.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

In "src/util/" there are many enumeration (enum) declarations.
Sometimes, it's better using a typedef for variable types,
function types and other usages. Other enumeration will be
changed to typedef's in the future.
Signed-off-by: NJulio Faracco <jcfaracco@gmail.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

All callers of virStorageFileGetMetadataFromBuf were first calling
virStorageFileProbeFormatFromBuf, to learn what format to pass in.
But this function is already wired to do the exact same probe if
the incoming format is VIR_STORAGE_FILE_AUTO, so it's simpler to
just refactor the probing into the central function.

* src/util/virstoragefile.h (virStorageFileGetMetadataFromBuf):
Drop parameter.
(virStorageFileProbeFormatFromBuf): Drop declaration.
* src/util/virstoragefile.c (virStorageFileGetMetadataFromBuf):
Do probe here instead of in callers.
(virStorageFileProbeFormatFromBuf): Make static.
* src/libvirt_private.syms (virstoragefile.h): Drop function.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Update caller.
* src/storage/storage_backend_gluster.c
(virStorageBackendGlusterRefreshVol): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

To avoid memory leak of the "backingStoreRaw" field when reparsing
backing chains a new function is being introduced by this patch that
shall be used to clear backing store information.

The memory leak was introduced in commit 8823272d.

Each backing store of a given disk is associated with a unique index
(which is also formatted in domain XML) for easier addressing of any
particular backing store. With this patch, any backing store can be
addressed by its disk target and the index. For example, "vdc[4]"
addresses the backing store with index equal to 4 of the disk identified
by "vdc" target. Such shorthand can be used in any API in place for a
backing file path:

    virsh blockcommit domain vda --base vda[3] --top vda[2]
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

Returning both virStorageSourcePtr and its path member does not make a
lot of sense.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

To avoid having the root of a backing chain present twice in the list we
need to invert the working of virStorageFileGetMetadataRecurse.

Until now the recursive worker created a new backing chain element from
the name and other information passed as arguments. This required us to
pass the data of the parent in a deconstructed way and the worker
created a new entry for the parent.

This patch converts this function so that it just fills in metadata
about the parent and creates a backing chain element from those. This
removes the duplication of the first element.

To avoid breaking the test suite, virstoragetest now calls a wrapper
that creates the parent structure explicitly and pre-fills it with the
test data with same function signature as previously used.

To conform with the naming of the planned XML output rename the metadata
variable name.

s/backingMeta/backingStore/g

Remove the now unused pieces of the structure.

Replace the old structure with the new one. This change is a trivial
name change operation (along with change of the freeing function).

Add the required fields that are missing from the new structure that
will allow us to switch the storage file metadata code entirely to the
new structure.

Add "relPath" and "relDir" and the raw backing store name. Also allow
creating linked lists of virStorageSourcePtrs to express backing chains.

Add a free function as some parts of the code will allocate the
structure.

Remove the obsolete field replaced by data in "path".

The testsuite requires tweaking as the name of the backing file is now
stored one layer deeper in the backing chain linked list.

As for the previous patch, this change is needed to achieve
compatibility with all the existing code, where we expect a fully
qualified path of local files to be present.

To allow future change of virStorageFileMetadata to virStorageSource we
need to store a full path in the "path" variable as rest of the code
expects it to be a full path. Rename the "path" field to "relPath" to
keep tracking the info but allowing a real "path" field.

Domain snapshots should only permit an external snapshot into
a storage format that permits a backing chain, since the new
snapshot file necessarily must be backed by the existing file.
The C code for the qemu driver is a little bit stricter in
currently enforcing only qcow2 or qed, but at the XML parser
level, including virt-xml-validate, it is fairly easy to
enforce that a user can't request a 'raw' external snapshot.

* docs/schemas/storagecommon.rng (storageFormat): Split out...
(storageFormatBacking): ...new sublist.
* docs/schemas/domainsnapshot.rng (disksnapshotdriver): Use new
type.
* src/util/virstoragefile.h (virStorageFileFormat): Rearrange for
easier code management.
* src/util/virstoragefile.c (virStorageFileFormat, fileTypeInfo):
Likewise.
* src/conf/snapshot_conf.c (virDomainSnapshotDiskDefParseXML): Use
new marker to limit selection of formats.
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

Another field no longer needed, getting us one step closer to
merging virStorageFileMetadata and virStorageSource.

* src/util/virstoragefile.h (_virStorageFileMetadata): Drop
field.
* src/util/virstoragefile.c (virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataFromFDInternal): Alter signature.
(virStorageFileFreeMetadata, virStorageFileGetMetadataFromBuf)
(virStorageFileGetMetadataFromFD): Adjust clients.
* tests/virstoragetest.c (_testFileData, testStorageChain)
(mymain): Simplify test.
Signed-off-by: NEric Blake <eblake@redhat.com>

The original chain lookup code had to pass in the starting name,
because it was not available in the chain.  But now that we have
added fields to the struct, this parameter is redundant.

* src/util/virstoragefile.h (virStorageFileChainLookup): Alter
signature.
* src/util/virstoragefile.c (virStorageFileChainLookup): Adjust
handling of top of chain.
* src/qemu/qemu_driver.c (qemuDomainBlockCommit): Adjust caller.
* tests/virstoragetest.c (testStorageLookup, mymain): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

Drop another redundant field from virStorageFileMetadata.

* src/util/virstoragefile.h (_virStorageFileMetadata): Drop
field.
* src/util/virstoragefile.c
(virStorageFileGetMetadataFromFDInternal)
(virStorageFileGetMetadataFromFD)
(virStorageFileGetMetadataRecurse): Adjust callers.
* tests/virstoragetest.c (_testFileData, testStorageChain)
(mymain): Simplify test.
Signed-off-by: NEric Blake <eblake@redhat.com>

A couple pieces of virStorageFileMetadata are used only while
collecting information about the chain, and don't need to
live permanently in the struct.  This patch refactors external
callers to collect the information separately, so that the
next patch can remove the fields.

* src/util/virstoragefile.h (virStorageFileGetMetadataFromBuf):
Alter signature.
* src/util/virstoragefile.c (virStorageFileGetMetadataInternal):
Likewise.
(virStorageFileGetMetadataFromFDInternal): Adjust callers.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Likewise.
* src/storage/storage_backend_gluster.c
(virStorageBackendGlusterRefreshVol): Likewise.
Signed-off-by: NEric Blake <eblake@redhat.com>

Finally starting to prune away some of the old fields that have
been made redundant by the new fields, on my way towards directly
reusing virStorageSource.

* src/util/virstoragefile.h (_virStorageFileMetadata): Drop
field.
* src/util/virstoragefile.c (virStorageFileGetMetadataInternal)
(virStorageFileChainLookup): Adjust callers.
* tests/virstoragetest.c (_testFileData, testStorageChain)
(mymain): Simplify test.
Signed-off-by: NEric Blake <eblake@redhat.com>

Deciding if a user string represents a local file instead of a
network path is an operation worth exposing directly, particularly
since the next patch will be removing a redundant variable that
was caching the information.

* src/util/virstoragefile.h (virStorageIsFile): New declaration.
* src/util/virstoragefile.c (virBackingStoreIsFile): Rename...
(virStorageIsFile): ...export, and allow NULL input.
(virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataRecurse, virStorageFileGetMetadata):
Update callers.
* src/conf/domain_conf.c (virDomainDiskDefForeachPath): Use it.
* src/storage/storage_backend_fs.c (virStorageBackendProbeTarget):
Likewise.
* src/libvirt_private.syms (virstoragefile.h): Export function.
Signed-off-by: NEric Blake <eblake@redhat.com>

The current use of virStorageFileMetadata is awkward; to learn
some of the information about a child node, you have to read
fields in the parent node.  This does not lend itself well to
modifying backing chains (whether inserting a new node in the
chain, or consolidating existing nodes); better would be to
learn about a child node directly in that node.  This patch
sets up some new fields which contain redundant information,
although not necessarily in the final desired state for the
new fields (see the next patch for actual tests of what is there
now).  Then later patches will do any refactoring necessary to
get the fields to their desired states, and update clients to
get the information from the new fields, so we can finally
delete the fields that are tracking information about the wrong
node.

More concretely, compare these three example backing chains:

good <- one
missing <- two
gluster://server/vol/img <- three

Pre-patch, querying the chains gives:
{ .backingStore = "/path/to/good",
  .backingStoreRaw = "good",
  .backingStoreIsFile = true,
  .backingStoreFormat = VIR_STORAGE_FILE_RAW,
  .backingMeta = {
    .backingStore = NULL,
    .backingStoreRaw = NULL,
    .backingStoreIsFile = false,
    .backingMeta = NULL,
  }
}
{ .backingStore = NULL,
  .backingStoreRaw = "missing",
  .backingStoreIsFile = false,
  .backingStoreFormat = VIR_STORAGE_FILE_NONE,
  .backingMeta = NULL,
}
{ .backingStore = "gluster://server/vol/img",
  .backingStoreRaw = NULL,
  .backingStoreIsFile = false,
  .backingStoreFormat = VIR_STORAGE_FILE_RAW,
  .backingMeta = NULL,
}

Deciding whether to ignore a missing backing file (as in virsh
vol-dumpxml) or report an error (as in security manager sVirt
labeling) requires reading multiple fields.  Plus, the format
is hard-coded to treat all network protocols as end-of-the-chain,
as if they were raw.  By the end of this patch series, the goal
is to instead represent these three situations as:

{ .path = "one",
  .canonPath = "/path/to/one",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "good",
  .backingMeta = {
    .path = "good",
    .canonPath = "/path/to/good",
    .type = VIR_STORAGE_TYPE_FILE,
    .format = VIR_STORAGE_FILE_RAW,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}
{ .path = "two",
  .canonPath = "/path/to/two",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "missing",
  .backingMeta = NULL,
}
{ .path = "three",
  .canonPath = "/path/to/three",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "gluster://server/vol/img",
  .backingMeta = {
    .path = "gluster://server/vol/img",
    .canonPath = "gluster://server/vol/img",
    .type = VIR_STORAGE_TYPE_NETWORK,
    .format = VIR_STORAGE_FILE_RAW,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}

or, for the second file, maybe also allowing:
{ .path = "two",
  .canonPath = "/path/to/two",
  .type = VIR_STORAGE_TYPE_FILE,
  .format = VIR_STORAGE_FILE_QCOW2,
  .backingStoreRaw = "missing",
  .backingMeta = {
    .path = "missing",
    .canonPath = NULL,
    .type = VIR_STORAGE_TYPE_NONE,
    .format = VIR_STORAGE_FILE_NONE,
    .backingStoreRaw = NULL,
    .backingMeta = NULL,
  }
}

* src/util/virstoragefile.h (_virStorageFileMetadata): Add
path, canonPath, relDir, type, and format fields.  Reorder
existing fields, and add lots of comments.
* src/util/virstoragefile.c (virStorageFileFreeMetadata): Clean
new fields.
(virStorageFileGetMetadataInternal)
(virStorageFileGetMetadataFromFDInternal): Start populating new
fields.
Signed-off-by: NEric Blake <eblake@redhat.com>

Now that we store all metadata about a storage image in a
virStorageSource struct let's use it also to store information needed by
the storage driver to access and do operations on the files.

Now that the storage source definition is uniform convert the helpers to
retrieve the actual storage type to a single one.

I noticed that the apparmor code could request metadata even
for a cdrom with no media, which would cause a memory leak of
the hash table used to look for loops in the backing chain.
But even before that, we blindly dereferenced the path for
printing a debug statement, so it is just better to enforce
that this is only used on non-NULL names.

* src/util/virstoragefile.c (virStorageFileGetMetadata): Assume
non-NULL path.
* src/util/virstoragefile.h: Annotate this.
* src/security/virt-aa-helper.c (get_files): Fix caller.
Signed-off-by: NEric Blake <eblake@redhat.com>