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add lzc_receive_with_header() and a helper function receive_header() #25

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add lzc_receive_with_header() and a helper function receive_header() #25

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340f585
add lzc_receive_with_header() and a helper function receive_header()
Oct 30, 2015
15ba755
lzc_receive_with_header now takes dmu_replay_record argument
Nov 3, 2015
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4 changes: 4 additions & 0 deletions libzfs_core/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@
lzc_send,
lzc_send_space,
lzc_receive,
lzc_receive_with_header,
lzc_recv,
lzc_exists,
is_supported,
Expand All @@ -56,6 +57,7 @@
lzc_get_props,
lzc_list_children,
lzc_list_snaps,
receive_header,
)

__all__ = [
Expand All @@ -78,6 +80,7 @@
'lzc_send',
'lzc_send_space',
'lzc_receive',
'lzc_receive_with_header',
'lzc_recv',
'lzc_exists',
'is_supported',
Expand All @@ -89,6 +92,7 @@
'lzc_get_props',
'lzc_list_children',
'lzc_list_snaps',
'receive_header',
]

# vim: softtabstop=4 tabstop=4 expandtab shiftwidth=4
119 changes: 119 additions & 0 deletions libzfs_core/_libzfs_core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -652,6 +652,125 @@ def lzc_receive(snapname, fd, force=False, origin=None, props=None):
lzc_recv = lzc_receive


def lzc_receive_with_header(snapname, fd, header, force=False, origin=None, props=None):
'''
Like :func:`lzc_receive`, but allows the caller to read the begin record
and then to pass it in.

That could be useful if the caller wants to derive, for example,
the snapname or the origin parameters based on the information contained in
the begin record.
:func:`receive_header` can be used to receive the begin record from the file
descriptor.

:param bytes snapname: the name of the snapshot to create.
:param int fd: the file descriptor from which to read the stream.
:param header: the stream's begin header.
:type header: ``cffi`` `CData` representing the header structure.
:param bool force: whether to roll back or destroy the target filesystem
if that is required to receive the stream.
:param origin: the optional origin snapshot name if the stream is for a clone.
:type origin: bytes or None
:param props: the properties to set on the snapshot as *received* properties.
:type props: dict of bytes : Any

:raises IOError: if an input / output error occurs while reading from the ``fd``.
:raises DatasetExists: if the snapshot named ``snapname`` already exists.
:raises DatasetExists: if the stream is a full stream and the destination filesystem already exists.
:raises DatasetExists: if ``force`` is `True` but the destination filesystem could not
be rolled back to a matching snapshot because a newer snapshot
exists and it is an origin of a cloned filesystem.
:raises StreamMismatch: if an incremental stream is received and the latest
snapshot of the destination filesystem does not match
the source snapshot of the stream.
:raises StreamMismatch: if a full stream is received and the destination
filesystem already exists and it has at least one snapshot,
and ``force`` is `False`.
:raises StreamMismatch: if an incremental clone stream is received but the specified
``origin`` is not the actual received origin.
:raises DestinationModified: if an incremental stream is received and the destination
filesystem has been modified since the last snapshot
and ``force`` is `False`.
:raises DestinationModified: if a full stream is received and the destination
filesystem already exists and it does not have any
snapshots, and ``force`` is `False`.
:raises DatasetNotFound: if the destination filesystem and its parent do not exist.
:raises DatasetNotFound: if the ``origin`` is not `None` and does not exist.
:raises DatasetBusy: if ``force`` is `True` but the destination filesystem could not
be rolled back to a matching snapshot because a newer snapshot
is held and could not be destroyed.
:raises DatasetBusy: if another receive operation is being performed on the
destination filesystem.
:raises BadStream: if the stream is corrupt or it is not recognized or it is
a compound stream or it is a clone stream, but ``origin``
is `None`.
:raises BadStream: if a clone stream is received and the destination filesystem
already exists.
:raises StreamFeatureNotSupported: if the stream has a feature that is not
supported on this side.
:raises PropertyInvalid: if one or more of the specified properties is invalid
or has an invalid type or value.
:raises NameInvalid: if the name of either snapshot is invalid.
:raises NameTooLong: if the name of either snapshot is too long.
'''

if origin is not None:
c_origin = origin
else:
c_origin = _ffi.NULL
if props is None:
props = {}
nvlist = nvlist_in(props)
ret = _lib.lzc_receive_with_header(snapname, nvlist, c_origin, force,
False, fd, header)
errors.lzc_receive_translate_error(ret, snapname, fd, force, origin, props)


def receive_header(fd):
'''
Read the begin record of the ZFS backup stream from the given file descriptor.

This is a helper function for :func:`lzc_receive_with_header`.

:param int fd: the file descriptor from which to read the stream.
:return: a tuple with two elements where the first one is a Python `dict` representing
the fields of the begin record and the second one is an opaque object
suitable for passing to :func:`lzc_receive_with_header`.
:raises IOError: if an input / output error occurs while reading from the ``fd``.

At present the following fields can be of interest in the header:

drr_toname : bytes
the name of the snapshot for which the stream has been created
drr_toguid : integer
the GUID of the snapshot for which the stream has been created
drr_fromguid : integer
the GUID of the starting snapshot in the case the stream is incremental,
zero otherwise
drr_flags : integer
the flags describing the stream's properties
drr_type : integer
the type of the dataset for which the stream has been created
(volume, filesystem)
'''
# read sizeof(dmu_replay_record_t) bytes directly into the memort backing 'record'
record = _ffi.new("dmu_replay_record_t *")
_ffi.buffer(record)[:] = os.read(fd, _ffi.sizeof(record[0]))
# get drr_begin member and its representation as a Pythn dict
drr_begin = record.drr_u.drr_begin
header = {}
for field, descr in _ffi.typeof(drr_begin).fields:
if descr.type.kind == 'primitive':
header[field] = getattr(drr_begin, field)
elif descr.type.kind == 'enum':
header[field] = getattr(drr_begin, field)
elif descr.type.kind == 'array' and descr.type.item.cname == 'char':
header[field] = _ffi.string(getattr(drr_begin, field))
else:
raise TypeError('Unexpected field type in drr_begin: ' + str(descr.type))
return (header, record)


def lzc_exists(name):
'''
Check if a dataset (a filesystem, or a volume, or a snapshot)
Expand Down
38 changes: 37 additions & 1 deletion libzfs_core/bindings/libzfs_core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,40 @@
DMU_OST_NUMTYPES
} dmu_objset_type_t;

#define MAXNAMELEN 256

struct drr_begin {
uint64_t drr_magic;
uint64_t drr_versioninfo; /* was drr_version */
uint64_t drr_creation_time;
dmu_objset_type_t drr_type;
uint32_t drr_flags;
uint64_t drr_toguid;
uint64_t drr_fromguid;
char drr_toname[MAXNAMELEN];
};

typedef struct zio_cksum {
uint64_t zc_word[4];
} zio_cksum_t;

typedef struct dmu_replay_record {
enum {
DRR_BEGIN, DRR_OBJECT, DRR_FREEOBJECTS,
DRR_WRITE, DRR_FREE, DRR_END, DRR_WRITE_BYREF,
DRR_SPILL, DRR_WRITE_EMBEDDED, DRR_NUMTYPES
} drr_type;
uint32_t drr_payloadlen;
union {
struct drr_begin drr_begin;
/* ... */
struct drr_checksum {
uint64_t drr_pad[34];
zio_cksum_t drr_checksum;
} drr_checksum;
} drr_u;
} dmu_replay_record_t;

int libzfs_core_init(void);
void libzfs_core_fini(void);

Expand All @@ -38,8 +72,10 @@
int lzc_get_holds(const char *, nvlist_t **);

int lzc_send(const char *, const char *, int, enum lzc_send_flags);
int lzc_receive(const char *, nvlist_t *, const char *, boolean_t, int);
int lzc_send_space(const char *, const char *, uint64_t *);
int lzc_receive(const char *, nvlist_t *, const char *, boolean_t, int);
int lzc_receive_with_header(const char *, nvlist_t *, const char *, boolean_t,
boolean_t, int, const struct dmu_replay_record *);

boolean_t lzc_exists(const char *);

Expand Down
39 changes: 21 additions & 18 deletions libzfs_core/test/test_libzfs_core.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1800,24 +1800,6 @@ def test_recv_incremental(self):
self.assertTrue(
filecmp.cmp(os.path.join(mnt1, name), os.path.join(mnt2, name), False))

# This test case fails unless unless a patch from
# https://clusterhq.atlassian.net/browse/ZFS-20
# is applied to libzfs_core, otherwise it succeeds.
@unittest.skip("fails with unpatched libzfs_core")
def test_recv_without_explicit_snap_name(self):
srcfs = ZFSTest.pool.makeName("fs1")
src1 = srcfs + "@snap1"
src2 = srcfs + "@snap2"
dstfs = ZFSTest.pool.makeName("fs2/received-100")
dst1 = dstfs + '@snap1'
dst2 = dstfs + '@snap2'

with streams(srcfs, src1, src2) as (_, (full, incr)):
lzc.lzc_receive(dstfs, full.fileno())
lzc.lzc_receive(dstfs, incr.fileno())
self.assertExists(dst1)
self.assertExists(dst2)

def test_recv_clone(self):
orig_src = ZFSTest.pool.makeName("fs2@send-origin")
clone = ZFSTest.pool.makeName("fs1/fs/send-clone")
Expand Down Expand Up @@ -2432,6 +2414,27 @@ def test_recv_incremental_into_cloned_fs(self):
self.assertExists(dst1)
self.assertNotExists(dst2)

def test_recv_with_header_full(self):
src = ZFSTest.pool.makeName("fs1@snap")
dst = ZFSTest.pool.makeName("fs2/received")

with temp_file_in_fs(ZFSTest.pool.makeName("fs1")) as name:
lzc.lzc_snapshot([src])

with tempfile.TemporaryFile(suffix='.ztream') as stream:
lzc.lzc_send(src, None, stream.fileno())
stream.seek(0)

(header, c_header) = lzc.receive_header(stream.fileno())
self.assertEqual(src, header['drr_toname'])
snap = header['drr_toname'].split('@', 1)[1]
lzc.lzc_receive_with_header(dst + '@' + snap, stream.fileno(), c_header)

name = os.path.basename(name)
with zfs_mount(src) as mnt1, zfs_mount(dst) as mnt2:
self.assertTrue(
filecmp.cmp(os.path.join(mnt1, name), os.path.join(mnt2, name), False))

def test_send_full_across_clone_branch_point(self):
origfs = ZFSTest.pool.makeName("fs2")

Expand Down